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Pion parton distribution function in light-front holographic QCD
Lei Chang, Khépani Raya, Xiaobin Wang
Published: , doi: 10.1088/1674-1137/abae52
The valence-quark distribution function of the pion has been of interest for decades; particularly, the profile it should adopt when $x\to1$ (the large-x behavior) has been the subject of a long-standing debate. In the light-front holographic QCD (LFHQCD) approach, this behavior is controlled by the so-called reparametrization function, $w_\tau(x)$, which is not fully determined from first principles. We show that, owing to the flexibility of $w_\tau(x)$, the large-x profile $u^{\pi}(x)\sim (1-x)^{2}$ can be contained within the LFHQCD formalism. This is in contrast to a previous LFHQCD study (Guy F. de Teramond et al., Phys. Rev. Lett., 120(18), 2018) in which $u^{\pi}(x)\sim (1-x)^{1}$ was found instead. Given our observations, augmented by perturbative QCD and recent lattice QCD results, we state that the large-x exponent of “2” cannot be excluded.
Constraints on anomalous quartic gauge couplings via Wγjj production at the LHC
Yu-Chen Guo, Ying-Ying Wang, Ji-Chong Yang, Chong-Xing Yue
Vector boson scattering at the Large Hadron Collider (LHC) is sensitive to anomalous quartic gauge couplings (aQGCs). In this study, we investigate the aQGC contribution to $ W \gamma jj$ production at the LHC with $\sqrt{s}=13$ TeV in the context of an effective field theory (EFT). The unitarity bound is applied as a cut on the energy scale of this production process, which is found to have significant suppressive effects on signals. To enhance the statistical significance, we analyze the kinematic and polarization features of the aQGC signals in detail. We find that the polarization effects induced by aQGCs are unique and can discriminate the signals from the SM backgrounds well. With the proposed event selection strategy, we obtain the constraints on the coefficients of dimension-8 operators with current luminosity. The results indicate that the process $pp \to W \gamma jj$ is powerful for searching for the $O_{M_{2,3,4,5}}$ and $O_{T_{5,6,7}}$ operators.
Observational constraints on dark matter decaying via gravity portals
Xu-Dong Sun, Ben-Zhong Dai
Global symmetry can guarantee the stability of dark matter particles (DMps). However, the nonminimal coupling between dark matter (DM) and gravity can break the global symmetry of DMps, which in turn leads to their decay. Under the framework of nonminimal coupling between scalar singlet dark matter (ssDM) and gravity, it is worth exploring the extent to which the symmetry of ssDM is broken. It is suggested that the total number of decay products of ssDM cannot exceed current observational constraints. Along these lines, the data obtained with satellites such as Fermi-LAT and AMS-02 suggest that the scale of ssDM global symmetry breaking can be limited. Because the mass of many promising DM candidates is likely to be in the GeV-TeV range, we determine reasonable parameters for the ssDM lifetime within this range. We find that when the mass of ssDM is around the electroweak scale (246 GeV), the corresponding 3$\sigma$ lower limit of the lifetime of ssDM is $5.3\times10^{26}$ s. Our analysis of ssDM around the electroweak scale encompasses the most abundant decay channels of all mass ranges so that the analysis of the behavior of ssDM under the influence of gravity is more comprehensive.
Thermodynamics in rotating anti-de Sitter black holes with massive scalar field in three dimensions
Bogeun Gwak
We investigated the tendency in the variations of CFT2 when a rotating AdS3 black hole changes because of the fluxes transferred by the scattering of a massive scalar field according to the anti-de Sitter (AdS)/conformal field theory (CFT) correspondence. The conserved quantities of the black hole are definitely constrained by the extremal condition. Moreover, the laws of thermodynamics provide a direction for the changes in the conserved quantities. Therefore, the black hole cannot be extremal under the scattering; this is naturally preferred. According to the relationship between the rotating AdS3 black hole and dual CFT2, we find that such changes in the black hole constrain the variations in the eigenstates of dual CFT2. Furthermore, the tendency in the variations is closely related to the laws of thermodynamics.
Massless limit of transport theory for massive Fermions
Xingyu Guo
Published: , doi: 10.1088/1674-1137/ababf9
We studied the $ m = 0 $ limit of different components of Wigner functions for massive fermions. Comparing with the chiral kinetic theory, we separated the vanishing and non-vanishing parts of vector and axial-vector components, up to the first order of $ \hbar $. Then, we discussed the possible physical meaning of the vanishing and non-vanishing parts and their different behaviors at thermal equilibrium.
Alpha decay of heavy and super heavy nuclei with a generalized electrostatic potential
R. Budaca, A. I. Budaca
Half-lives of α decay for Z≥ 84 nuclei are calculated based on the WKB theory applied for a phenomenological potential barrier composed of a centrifugal contribution and a screened electrostatic interaction represented by a Hulthen potential. For favored decays, the model has a single adjustable parameter associated with the screening of the electrostatic potential. The description of half lives for unfavored decays requires an additional hindrance term. A good agreement with experimental data is obtained in all considered cases. The evolution of the screening parameter for each nucleus revealed its dependence on shell filling. The model is also used for theoretical predictions on a few nuclei with uncertain or incomplete decay information.
Anomalous ${{H\to ZZ \to 4\ell}}$ decay and its interference effects on gluon–gluon contribution at the LHC
Hua-Rong He, Xia Wan, You-Kai Wang
We calculate the spinor helicity amplitudes of anomalous $H\to ZZ \to 4\ell$ decay. After embedding these analytic formulas into the MCFM package, we study the interference effects between the anomalous $gg\to H\to ZZ \to 4\ell$ process and the SM processes, which are indispensable in the Higgs off-shell region. Subsequently, the constraints on the anomalous couplings are estimated using LHC experimental data.
A compact analytical approximation for a light sterile neutrino oscillation in matter
Bao-Biao Yue, Wei Li, Jia-Jie Ling, Fan-Rong Xu
Published: , doi: 10.1088/1674-1137/ababfa
The existence of light sterile neutrinos is a long-standing question in particle physics. Several experimental “anomalies” might be explained by introducing eV mass scaled light sterile neutrinos. Many experiments are actively searching for such light sterile neutrinos through neutrino oscillation. For long baseline experiments, the matter effect should be treated carefully for precise calculation of the neutrino oscillation probabilities. However, this is usually time-consuming or analytically complex. In this manuscript, we adopt a Jacobi-like method to diagonalize the Hermitian Hamiltonian matrix and derive analytically simplified neutrino oscillation probabilities for 3 (active) + 1 (sterile)-neutrino mixing for a constant matter density. These approximations can reach a considerably high numerical accuracy while retaining their analytical simplicity and fast computing speed. This would be useful for current and future long baseline neutrino oscillation experiments.
${{X(2239)}}$ and ${{\eta(2225)}}$ as hidden-strange molecular states from ${{\Lambda}}{\bar{\Lambda}}$ interaction
Jun-Tao Zhu, Yi Liu, Dian-Yong Chen, Longyu Jiang, Jun He
In this work, we propose the possible assignment of the newly observed $X(2239)$, as well as $\eta(2225)$, as a molecular state from the interaction of a baryon $\Lambda$ and an antibaryon $\bar{\Lambda}$. With the help of effective Lagrangians, the $\Lambda\bar{\Lambda}$ interaction is described within the one-boson-exchange model with $\eta$, $\eta'$, $\omega$, $\phi$, and $\sigma$ exchanges considered. After inserting the potential kernel into the quasipotential Bethe-Salpeter equation, the bound states from the $\Lambda\bar{\Lambda}$ interaction can be studied by searching for the pole of the scattering amplitude. Two loosely bound states with spin parities $I^G(J^{PC})=0^+(0^{-+})$ and $0^-(1^{--})$ appear near the threshold with almost the same parameter. The $0^-(1^{--})$ state can be assigned to $X(2239)$ observed at BESIII, which is very close to the $\Lambda\bar{\Lambda}$ threshold. The scalar meson $\eta(2225)$ can be interpreted as a $0^+(0^{-+})$ state from the $\Lambda\bar{\Lambda}$ interaction. The annihilation effect is also discussed through a coupled-channel calculation plus a phenomenological optical potential. It provides large widths to two bound states produced from the $\Lambda\bar{\Lambda}$ interaction. The mass of the $1^-$ state is slightly larger than the mass of the $0^-$ state after including the annihilation effect, which is consistent with our assignment of these two states as $X(2239)$ and $\eta(2225)$, respectively. The results suggest that further investigation is required to understand the structures near the $\Lambda\bar{\Lambda}$ threshold, such as $X(2239)$, $\eta(2225)$, and $X(2175)$.
Gravitational wave imprint of new symmetry breaking
Wei Chao, Wen-Feng Cui, Huai-Ke Guo, Jing Shu
It is believed that there are more fundamental gauge symmetries beyond those described by the Standard Model of particle physics. The scales of these new gauge symmetries are usually too high to be reachable by particle colliders. Considering that the phase transition (PT) relating to the spontaneous breaking of new gauge symmetries to the electroweak symmetry might be strongly first order, we propose considering the stochastic gravitational waves (GW) arising from this phase transition as an indirect way of detecting these new fundamental gauge symmetries. As an illustration, we explore the possibility of detecting the stochastic GW generated from the PT of $ {\bf{B}}-{\bf{L}}$ in the space-based interferometer detectors. Our study demonstrates that the GW energy spectrum is reachable by the LISA, Tianqin, Taiji, BBO, and DECIGO experiments only for the case where the spontaneous breaking of $ {\bf{B}}-{\bf{L}}$ is triggered by at least two electroweak singlet scalars.
Fine tuning problem of the cosmological constant in a generalized Randall-Sundrum model
Guang-Zhen Kang, De-Sheng Zhang, Li Jun, Hong-Shi Zong
To solve the cosmological constant fine tuning problem, we investigate an $(n+1)$-dimensional generalized Randall-Sundrum brane world scenario with two $(n-1)$-branes instead of two 3-branes. Adopting an anisotropic metric ansatz, we obtain the positive effective cosmological constant $\Omega_{\rm eff}$ of order $10^{-124}$ and only require a solution $\simeq50-80$. Meanwhile, both the visible and hidden branes are stable because their tensions are positive. Therefore, the fine tuning problem can be solved quite well. Furthermore, the Hubble parameter $H_{1}(z)$ as a function of redshift $z$ is in good agreement with the cosmic chronometers dataset. The evolution of the universe naturally shifts from deceleration to acceleration. This suggests that the evolution of the universe is intrinsically an extra-dimensional phenomenon. It can be regarded as a dynamic model of dark energy that is driven by the evolution of the extra dimensions on the brane.
Finite particle number description of neutron matter using the unitary correlation operator and high-momentum pair methods
Niu Wan, Takayuki Myo, Chang Xu, Hiroshi Toki, Hisashi Horiuchi, Mengjiao Lyu
Using bare Argonne V4' (AV4'), V6' (AV6'), and V8' (AV8') nucleon–nucleon ($NN$) interactions, the nuclear equations of state (EOSs) for neutron matter are calculated with the unitary correlation operator and high-momentum pair methods. Neutron matter is described using a finite particle number approach with magic number $N=66$ under a periodic boundary condition. The central short-range correlation originating from the short-range repulsion in the $NN$ interaction is treated by the unitary correlation operator method (UCOM), and the tensor correlation and spin-orbit effects are described by the two-particle two-hole (2p2h) excitations of nucleon pairs, where the two nucleons with a large relative momentum are regarded as a high-momentum (HM) pair. With increasing 2p2h configurations, the total energy per particle of the neutron matter is well-converged under this UCOM+HM framework. Comparing the results calculated with AV4', AV6', and AV8' $NN$ interactions, we demonstrates the effects of the short-range correlation, tensor correlation, and spin-orbit coupling on the density dependence of the total energy per particle of neutron matter. Moreover, the contribution of each Hamiltonian component to the total energy per particle is discussed. The EOSs of neutron matter calculated within the present UCOM+HM framework agree with the calculations of six microscopic many-body theories, especially the auxiliary field-diffusion Monte Carlo calculations.
Gauge dependence of the perturbative QCD predictions under the momentum-space subtraction scheme
Jun Zeng, Xing-Gang Wu, Xu-Chang Zheng, Jian-Ming Shen
Published: , doi: 10.1088/1674-1137/abae4e
The momentum-space subtraction (MOM) scheme is one of the most frequently used renormalization schemes in perturbative QCD (pQCD) theory. In this paper, we discuss in detail the gauge dependence of the pQCD predictions obtained under the MOM scheme. Conventionally, a renormalization scale ambiguity exists for the fixed-order pQCD predictions; this assigns an arbitrary range and error for the fixed-order pQCD prediction and makes the discussions on the issue of the gauge dependence much more involved. The principle of maximum conformality (PMC) adopts the renormalization group equation to determine the magnitude of the coupling constant; hence, it determines the effective momentum flow of the process, which is independent of the choice of renormalization scale. Thus, no renormalization scale ambiguity exists in PMC predictions. To focus our attention on the MOM scheme's gauge dependence, we first apply the PMC to deal with the pQCD series. As an explicit example, we adopt the Higgs boson decay width $ \Gamma(H\to gg) $ up to its five-loop QCD contribution, to demonstrate the behavior of the gauge dependence before and after applying the PMC. Interaction vertices are chosen to define five different MOM schemes: mMOM, MOMh, MOMq, MOMg, and MOMgg. Under these MOM schemes, we obtain $ \Gamma(H \to gg)|^{\rm{mMOM}}_{\rm{PMC}} =$$ 332.8{^{+11.6}_{-3.7}}\pm7.3\; \rm{KeV} $, $ \Gamma(H \to gg)|^{\rm{MOMh}}_{\rm{PMC}} = 332.8{^{+27.5}_{-34.6}}\pm7.3\; \rm{KeV} $, $ \Gamma(H \to gg)|^{\rm{MOMq}}_{\rm{PMC}} = 332.9{^{+27.4}_{-34.7}}\pm 7.3\; \rm{KeV} $, $ \Gamma(H \to gg)|^{\rm{MOMg}}_{\rm{PMC}} = 332.7{^{+27.5}_{-34.6}}\pm7.3\; \rm{KeV} $, and $ \Gamma(H \to gg)|^{\rm{MOMgg}}_{\rm{PMC}} = 337.9{^{+1.2}_{-1.7}}\pm 7.7\; \rm{KeV} $; here, the central values correspond to the Landau gauge with the gauge parameter $ \xi^{\rm MOM} = 0 $, the first errors correspond to $ \xi^{\rm MOM}\in[-1,1] $, and the second ones arise through taking $ \Delta \alpha_s^{\overline{\rm MS}}(M_Z) = \pm0.0011 $. The uncertainty of the Higgs mass $ \Delta M_H = 0.24\; \rm{GeV} $ causes an extra error of $ \sim \pm1.7 $ (or $ \sim\pm1.8 $) KeV for all the aforementioned MOM schemes. It is found that the Higgs decay width $ \Gamma (H\to gg) $ depends very weakly on the choice of MOM scheme, which is consistent with renormalization group invariance. It is found that the gauge dependence of $ \Gamma(H\to gg) $ under the $ \rm{MOMgg} $ scheme is less than ±1%, which is the smallest gauge dependence among all the aforementioned MOM schemes.
Prediction of moment of inertia of rotating nuclei
Mohd Kh. M. Abu El Sheikh, A. A. Okhunov, H. Abu Kassim, M. U. Khandaker
Published: , doi: 10.1088/1674-1137/abb0dd
In this study, the mathematical expression formulated by Bohr for the moment of inertia of even-even nuclei based on the hydrodynamical model is modified. The modification pertains to the kinetic energy of the surface oscillations, including the second and third terms of the R-expansion as well as the first term, which had already been modified by Bohr. Therefore, this work can be considered a continuation and support of Bohr's hydrodynamic model. The procedure yields a Bohr formula to be multiplied by a factor that depends on the deformation parameter. Bohr's (modified) formula is examined by applying it on axially symmetric even-even nuclei with atomic masses ranging between 150 and 190 as well as on some triaxial symmetry nuclei. In this paper, the modification of Bohr's formula is discussed, including information about the stability of this modification and the second and third terms of the R-expansion in Bohr's formula. The results of the calculation are compared with the experimental data and Bohr's results recorded earlier. The results obtained are in good agreement with experimental data, with a ratio of approximately 0.7, and are better than those of the unmodified ones.
The effective potential originating from swampland and the non-trivial Brans-Dicke coupling
Qi Li, Jing Li, Yongxiang Zhou, Xun Xue
Published: , doi: 10.1088/1674-1137/abab8e
The effective vacuum energy density contributed by the non-trivial contortion distribution and the bare vacuum energy density can be viewed as the energy density of the auxiliary quintessence field potential. We find that the negative bare vacuum energy density from string landscape leads to a monotonically decreasing quintessence potential while the positive one from swampland leads to the metastable or stable de Sitter-like potential. Moreover, the non-trivial Brans-Dicke like coupling between the quintessence field and gravitation field is necessary in the latter case.
New measurements and reanalysis of 14N elastic scattering on 10B target
Marzhan Nassurlla, N. Burtebayev, T. Kh. Sadykov, I. Boztosun, N. Amangeldi, D. Alimov, Zh. Kerimkulov, J. Burtebayeva, Maulen Nassurlla, A. Kurakhmedov, S.B. Sakuta, Mesut Karakoc, Awad A. Ibraheem, K.W. Kemper, Sh. Hamada
Published: , doi: 10.1088/1674-1137/abab89
The angular distributions of elastic scattering of 14N ions on 10B targets have been measured at incident beam energies of 21.0 and 24.5 MeV. Angular distributions at higher energies 38–94.0 MeV (previously measured) were also included in the analysis. All data were analyzed within the framework of the optical model and the distorted waves Born approximation method. The observed rise in cross sections at large angles was interpreted as a possible contribution of the α-cluster exchange mechanism. Spectroscopic amplitudes SA2 and SA4 for the configuration 14N→ 10B +α were extracted. Their average values are 0.58±0.10 and 0.81±0.12 for SA2 and SA4, respectively, suggesting that the exchange mechanism is a major component of the elastic scattering for this system. The energy dependence of the depths for the real and imaginary potentials was found.
Tetraquark candidates in LHCb’s di-J/ψ mass spectrum
Zhi-Gang Wang
In this article, we study the first radial excited states of the scalar, axialvector, vector, and tensor diquark-antidiquark-type $cc\bar{c}\bar{c}$ tetraquark states with the QCD sum rules and obtain the masses and pole residues; then, we use the Regge trajectories to obtain the masses of the second radial excited states. The predicted masses support assigning the broad structure from 6.2 to 6.8 GeV in the di- $J/\psi$ mass spectrum to be the first radial excited state of the scalar, axialvector, vector, or tensor $cc\bar{c}\bar{c}$ tetraquark state, as well as assigning the narrow structure at about 6.9 GeV in the di- $J/\psi$ mass spectrum to be the second radial excited state of the scalar or axialvector $cc\bar{c}\bar{c}$ tetraquark state.
Thermodynamics and weak cosmic censorship conjecture of 4D Gauss-Bonnet-Maxwell black holes via charged particle absorption
Shuxuan Ying
Recently, the non-trivial solutions for 4-dimensional black holes of Einstein-Gauss-Bonnet gravity had been discovered. In this paper, considering a charged particle entering into a 4-dimensional Gauss-Bonnet-Maxwell black hole, we calculate the black hole thermodynamic properties using the Hamilton-Jacobi equation. In the normal phase space, the cosmological constant and Gauss-Bonnet parameter are fixed, the black hole satisfies the first and second laws of thermodynamics, and the weak cosmic censorship conjecture (WCCC) is valid. On the other hand, in the case of extended phase space, the cosmological constant and Gauss-Bonnet parameter are treated as thermodynamic variables. The black hole also satisfies the first law of thermodynamics. However, the increase or decrease in the black hole's entropy depends on some specific conditions. Finally, we observe that the WCCC is violated for the near-extremal black holes in the extended phase space.
Recent progress in multiple chiral doublet bands
Shou-Yu Wang
Published: , doi: 10.1088/1674-1137/abaed2
Recent progress regarding multiple chiral doublet bands ($ {\rm{M}}\chi{\rm{D}}$) is reviewed from the experimental and theoretical perspectives. In particular, the experimental findings, theoretical predictions, selection rule for electromagnetic transitions, $ {\rm{M}}\chi{\rm{D}}$ with octupole correlations, and some related topics are highlighted. Based on these discussions, it is of great scientific interest to search for the other $ {\rm{M}}\chi{\rm{D}}$, as well as possible chiral wobblers, chirality-parity quartet bands, and chirality-pseudospin triplet (or quartet) bands in the nuclear system.
A Bayesian-neural-network prediction for fragment production in proton induced spallation reaction
Chun-Wang Ma, Dan Peng, Hui-Ling Wei, Yu-Ting Wang, Jie Pu
Fragment production in spallation reactions yields key infrastructure data for various applications. Based on the empirical SPACS parameterizations, a Bayesian-neural-network (BNN) approach is established to predict the fragment cross sections in proton-induced spallation reactions. A systematic investigation has been performed for the measured proton-induced spallation reactions of systems ranging from intermediate to heavy nuclei systems and incident energies ranging from 168 MeV/u to 1500 MeV/u. By learning the residuals between the experimental measurements and SPACS predictions, it is found that the BNN-predicted results are in good agreement with the measured results. The established method is suggested to benefit the related research on nuclear astrophysics, nuclear radioactive beam sources, accelerator driven systems, proton therapy, etc.
Probing electroweak dark matter at 14 TeV LHC
Shuai Xu, Si-Bo Zheng
Published: , doi: 10.1088/1674-1137/abae4c
Well-motivated electroweak dark matter is often hosted by an extended electroweak sector that also contains new lepton pairs with masses near the weak scale. In this study, we explore such electroweak dark matter by combining dark matter direct detection experiments and high-luminosity LHC probes of new lepton pairs. Using Z- and W-associated electroweak processes with two or three lepton final states, we show that depending on the overall coupling constant, dark matter masses of up to $170-210$ GeV can be excluded at the $2\sigma$ level and those up to $175-205$ GeV can be discovered at the $5\sigma$ level at the 14 TeV LHC with integrated luminosities of 300 fb$^{-1}$ and 3000 fb$^{-1}$, respectively.
Revisiting nonfactorizable contributions to factorization-forbidden decays of B mesons to charmonium
Ya-Qian Li, Meng-Kun Jia, Rui Zhou
Published: , doi: 10.1088/1674-1137/abae50
Motivated by the large rates of $B\rightarrow (\chi_{c0}, \chi_{c2}, h_c)K$ decays observed by the $BABAR$ and Belle collaborations, we investigate the nonfactorizable contributions to these factorization-forbidden decays, which can occur through a gluon exchange between the $c\bar c$ system and the spectator quark. Our numerical results demonstrate that the spectator contributions are capable of producing a large branching ratio consistent with the experiments. As a by-product, we also study the Cabibbo-suppressed decays, such as $B\rightarrow (\chi_{c0}, \chi_{c2}, h_c)\pi$ and the U-spin-related $B_s$ decay, which have so far received less theoretical and experimental attention. The calculated branching ratios reach the order of $10^{-6}$, which is within the scope of the Belle-II and LHCb experiments. Further, the $CP$-asymmetry parameters are also calculated for these decays. The obtained results are compared with the available experimental data and numbers from other predictions. We also investigate the sources of theoretical uncertainties in our calculation.
Two-neutron transfer reactions as a tool to study the interplay between shape coexistence and quantum phase transitions
J.E. García-Ramos, J.M. Arias, A. Vitturi
The atomic mass table presents zones where the structure of the states changes rapidly as a function of the neutron or proton number. Among them, notable examples are the A ≈ 100 Zr region, the Pb region around the neutron midshell (N = 104), and the N ≈ 90 rare-earth region. The observed phenomena can be understood in terms of either shape coexistence or quantum phase transitions. The objective of this study is to find an observable that can distinguish between both shape coexistence and quantum phase transitions. As an observable to be analyzed, we selected the two-neutron transfer intensity between the 0+ states in the parent and daughter nuclei. The framework used for this study is the Interacting Boson Model (IBM), including its version with configuration mixing (IBM-CM). To generate wave functions of isotope chains of interest needed for calculating transfer intensities, previous systematic studies using IBM and IBM-CM were used without changing the parameters. The results of two-neutron transfer intensities are presented for Zr, Hg, and Pt isotopic chains using IBM-CM. Moreover, for Zr, Pt, and Sm isotopic chains, the results are presented using IBM with only a single configuration, i.e., without using configuration mixing. For Zr, the two-neutron transfer intensities between the ground states provide a clear observable, indicating that normal and intruder configurations coexist in the low-lying spectrum and cross at A = 98 → 100. This can help clarify whether shape coexistence induces a given quantum phase transition. For Pt, in which shape coexistence is present and the regular and intruder configurations cross for the ground state, there is almost no impact on the value of the two-neutron transfer intensity. Similar is the situation with Hg, where the ground state always has a regular nature. For the Sm isotope chain, which is one of the quantum phase transition paradigms, the value of the two-neutron transfer intensity is affected strongly.
Effect of null aether field on weak deflection angle of black holes
A. Övgün, İ. Sakallı, J. Saavedra
We study light rays in the static and spherically symmetric gravitational field of the null aether theory (NAT). To this end, we employ the Gauss-Bonnet theorem to compute the deflection angle formed by a NAT black hole in the weak limit approximation. Using the optical metrics of the NAT black hole, we first obtain the Gaussian curvature and then calculate the leading terms of the deflection angle. Our calculations indicate how gravitational lensing is affected by the NAT field. We also illustrate that the bending of light stems from global and topological effects.
Dark matter search at colliders and neutrino floor
Qing-Hong Cao, An-Kang Wei, Qian-Fei Xiang
Published: , doi: 10.1088/1674-1137/abae53
The sensitivity of the direct detection of dark matter (DM) approaches the so-called neutrino floor, below which it is difficult to disentangle the DM candidate from the neutrino background. In this work, we consider the scenario that no DM signals are reported in various DM direct detection experiments and explore whether collider searches could probe DM below the neutrino floor. We adopt several simplified models in which the DM candidate couples to electroweak gauge bosons or leptons in the standard model only through high-dimensional operators. After including the RGE running effect, we investigate the constraints of direct detection, indirect detection, and collider searches. The collider search can probe light DM below the neutrino floor. Particularly, for the effective interaction of $ \bar{\chi}\chi B_{\mu\nu}B^{\mu\nu}$, current data from the mono-photon channel at the 13 TeV LHC has already covered the entire parameter space of the neutrino floor.
Null geodesics, quasinormal modes, and thermodynamic phase transition for charged black holes in asymptotically flat and dS spacetimes
Shao-Wen Wei, Yu-Xiao Liu
Published: , doi: 10.1088/1674-1137/abae54
A numerical study has indicated that there exists a relation between the quasinormal modes and the Davies point for a black hole. In this paper, we analytically study this relation for charged Reissner-Nordström black holes in asymptotically flat and de Sitter (dS) spacetimes in the eikonal limit, under which the quasinormal modes can be obtained from the null geodesics using the angular velocity $\Omega$ and the Lyapunov exponent $\lambda$ of the photon sphere. Both in asymptotically flat and dS spacetimes, we observe spiral-like shapes in the complex quasinormal mode plane. However, the starting point of the shapes does not coincide with the Davies point. Nevertheless, we find a new relation in which the Davies point exactly meets the maximum temperature T in the T-$\Omega$ and T-$\lambda$ planes. In a higher-dimensional asymptotically flat spacetime, although there is no spiral-like shape, such a relation still holds. Therefore, we provide a new relation between black hole thermodynamics and dynamics in the eikonal limit. Applying this relation, we can test the thermodynamic property of a black hole using the quasinormal modes.
Near-threshold K*(892)+ meson production in the interaction of π mesons with nuclei
E. Ya. Paryev
Published: , doi: 10.1088/1674-1137/abae55
We study the inclusive production of strange vector $K^*(892)^+$ mesons in ${\pi^-}A$ reactions at near-threshold laboratory incident pion momenta of 1.4–2.0 GeV/c via a nuclear spectral function approach. The approach accounts for incoherent primary $\pi^-$ meson–proton ${\pi^-}p \to {K^*(892)^+}\Sigma^-$ production processes as well as the influence of the scalar $K^*(892)^+$ –nucleus potential (or the $K^*(892)^+$ in-medium mass shift) on these processes. We calculate the absolute differential and total cross sections for the production of $K^*(892)^+$ mesons from carbon and tungsten nuclei at laboratory angles of 0 $^{\circ}$ –45 $^{\circ}$ and at the aforementioned momenta in five scenarios for the aforenoted shift. We show that the $K^*(892)^+$ momentum distributions and their excitation functions (absolute and relative) possess a high sensitivity to changes in the in-medium $K^*(892)^+$ mass shift in the low-momentum region of 0.1–0.6 GeV/c. Therefore, the measurement of such observables in a dedicated experiment at the GSI pion beam facility in the near-threshold momentum domain will allow us to get valuable information on the $K^*(892)^+$ in-medium properties.
Unified interpretation of scalegenesis in conformally extended standard models: a dynamical origin of Higgs portal
Hiroyuki Ishida, Shinya Matsuzaki, Ruiwen Ouyang
We present a universal interpretation of a class of conformal extended standard models that include Higgs portal interactions as realized in low-energy effective theories. The scale generation mechanism in this class (scalegenesis) arises along the (nearly) conformal/flat direction for breaking scale symmetry, where the electroweak symmetry-breaking structure arises similarly as in the standard model. A dynamical origin for the Higgs portal coupling can provide the discriminator for the low-energy “universality class,” to be probed in forthcoming collider experiments.
Radiative decays of f1(1285) as the ${ { K}^*\bar { K}}$ molecular state
Ju-Jun Xie, Gang Li, Xiao-Hai Liu
Published: , doi: 10.1088/1674-1137/abae51
With $f_1(1285)$ as a dynamically generated resonance from $ K^*\bar K$ interactions, we estimate the rates of the radiative transitions of the $f_1(1285)$ meson to the vector mesons $\rho^0$, $\omega$ and $\phi$. These radiative decays proceed via the kaon loop diagrams. The calculated results are in a fair agreement with experimental measurements. Some predictions can be tested experimentally; their analysis will be valuable for decoding the strong coupling of the $f_1(1285)$ state to the $\bar{K}K^*$ channel.
DP(π, K) helicity form factors within light-cone sum rule approach
Hai-Bing Fu, Wei Cheng, Rui-Yu Zhou, Long Zeng
Published: , doi: 10.1088/1674-1137/abae4f
In this study, $D\to P(\pi, K)$ helicity form factors (HFFs) are investigated by applying the QCD light-cone sum rule (LCSR) approach. The calculation accuracy is up to the next-to-leading order (NLO) gluon radiation correction of twist-(2,3) distribution amplitude. The resultant HFFs at a large recoil point are ${\cal{P}}_{t,0}^\pi(0) = 0.688^{+0.020}_{-0.024}$ and ${\cal{P}}_{t,0}^K(0)=0.780^{+0.024}_{-0.029}$, in which the contributions from the three particles of the leading order (LO) are so small that they can be safely neglected. The maximal contribution of the NLO gluon radiation correction for ${\cal{P}}_{t,0}^{\pi,K}(0)$ is less than 3%. After extrapolating the LCSR predictions for these HFFs to the whole $q^2$-region, we obtain the decay widths for semileptonic decay processes $D\to P\ell\nu_\ell$, which are consistent with the BES-III collaboration predictions within error limits. After considering the $D^{+}/D^{0}$-meson lifetime, we give the branching fractions of $D\to P\ell\nu_\ell$ with $\ell = e, \mu$; our predictions also agree with the BES-III collaboration results within error limits, especially for the $D\to \pi \ell\nu_\ell$ decay process. Finally, we present the forward-backward asymmetry ${\cal{A}}_{\rm{FB}}^\ell(q^2)$ and lepton convexity parameter ${\cal{C}}_F^\ell(q^2)$, and further calculate the mean value of these two observations, $\langle{\cal{A}}_{\rm{FB}}^\ell\rangle$ and $\langle{\cal{C}}_F^\ell\rangle$, which may provide a way to test those HFFs in future experiments.
Cosmic acceleration caused by the extra-dimensional evolution in a generalized Randall-Sundrum model
Guang-Zhen Kang, De-Sheng Zhang, Chao Shi, Long Du, Dan Shan, Hong-Shi Zong
Published: , doi: 10.1088/1674-1137/abadec
We investigate an $(n+1) $-dimensional generalized Randall-Sundrum model with an anisotropic metric which has three different scale factors. One obtains a positive effective cosmological constant $\Omega_{\rm eff}\sim10^{-124}$(in Planck units), which only needs a solution $ kr\simeq50-80$ without fine tuning. Both the visible and hidden brane tensions are positive, which renders the two branes stable. Then, we find that the Hubble parameter is close to a constant in a large region near its minimum, thus causing the acceleration of the universe. Meanwhile, the scale of extra dimensions is smaller than the observed scale but greater than the Planck length. This may suggest that the observed present acceleration of the universe is caused by the extra-dimensional evolution.
Fast heating dissociation of ${ \Upsilon(1S) }$ in heavy ion collisions at RHIC
Yunpeng Liu, Baoyi Chen
By adopting the adiabatic assumption in the cooling process, we discuss a novel mechanism of $ \Upsilon(1S) $ suppression that occurs due to the fast heating process at the early stage of the fireball, instead of its finite decay width in a finite temperature medium generated by heavy ion collisions. We calculate the transition probability after the fast heating dissociation as a function of the temperature of the medium and the nuclear modification factor in central collisions and find that the suppression is not negligible at RHIC, even if the width of $ \Upsilon(1S) $ becomes zero.
Cross-section measurements for 58,60,61Ni(n, α)55,57,58Fe reactions in the 4.50 – 5.50 MeV neutron energy region
Haoyu Jiang, Zengqi Cui, Yiwei Hu, Jie Liu, Jinxiang Chen, Guohui Zhang, Yu. M. Gledenov, E. Sansarbayar, G. Khuukhenkhuu, L. Krupa, I. Chuprakov
Published: , doi: 10.1088/1674-1137/abadf2
The cross sections at 5 energy points of the 58Ni(n, α)55Fe reaction were measured in the 4.50 MeV ≤ En ≤ 5.50 MeV region while those for the 60Ni(n, α)57Fe and 61Ni(n, α)58Fe reactions were measured at En = 5.00 and 5.50 MeV using the 4.5 MV Van de Graaff accelerator at Peking University. A gridded twin ionization chamber (GIC) was used as the detector, and enriched 58Ni, 60Ni, and 61Ni foil samples were prepared and mounted at the sample changer of the GIC. Three highly enriched 238U3O8 samples inside the GIC were used to determine the relative and absolute neutron fluxes. The neutron energy spectra were obtained through unfolding the pulse height spectra measured by the EJ-309 liquid scintillator. The interference from the low-energy neutrons and impurities in the samples has been corrected. The present data of the 60Ni(n, α)57Fe reaction are the first measurement results below 6.0 MeV, and those of the 61Ni(n, α)58Fe reactions are the first measurement results in the MeV region. The present results have been compared with existing measurements, evaluations, and TALYS-1.9 calculations.
Pattern for flavor-dependent quark-antiquark interaction
Muyang Chen, Lei Chang
A flavor-dependent kernel is constructed based on the rainbow-ladder truncation of the Dyson-Schwinger and Bethe-Salpeter equation approach of quantum chromodynamics. The quark-antiquark interaction is composed of a flavor-dependent infrared part and a flavor-independent ultraviolet part. Our model gives a successful and unified description of the light, heavy, and heavy-light ground pseudoscalar and vector mesons. For the first time, our model shows that the infrared-enhanced quark-antiquark interaction is stronger and wider for lighter quarks.
Heavy flavor quenching and flow: the roles of initial condition, pre-equilibrium evolution, and in-medium interaction
Shu-Qing Li, Wen-Jing Xing, Feng-Lei Liu, Shanshan Cao, Guang-You Qin
Published: , doi: 10.1088/1674-1137/abadee
Within an advanced Langevin-hydrodynamics framework coupled to a hybrid fragmentation-coalescence hadronization model, we study heavy flavor quenching and flow in relativistic heavy-ion collisions. We investigate how the initial heavy quark spectrum, the in-medium energy loss and hadronization mechanisms of heavy quarks, the evolution profile of the pre-equilibrium stage, the medium flow, and the temperature dependence of heavy quark diffusion coefficients influence the suppression and elliptic flow of heavy mesons at the RHIC and the LHC. Our results show that the different modeling of initial conditions, pre-equilibrium evolution, and in-medium interactions can individually yield uncertainties of approximately 10-40% in D meson suppression and flow at a low transverse momentum. We also find that proper combinations of collisional versus radiative energy loss, coalescence versus fragmentation in hadronization, and the inclusion of medium flow are the most important factors for describing the suppression and elliptic flow of heavy mesons.
Horizon thermodynamics in ${f(R,R^{\mu\nu}R_{\mu\nu}})$ theory
Haiyuan Feng, Rong-Jia Yang
Published: , doi: 10.1088/1674-1137/abadef
We investigate whether the new horizon first law still holds in $f(R,R^{\mu\nu}R_{\mu\nu})$ theory. For this complicated theory, we first determine the entropy of a black hole by using the Wald method, and then derive the energy of the black hole by using the new horizon first law, the degenerate Legendre transformation, and the gravitational field equations. For application, we consider the quadratic-curvature gravity, and first calculate the entropy and energy of a static spherically symmetric black hole, which are in agreement with the results obtained in the literature for a Schwarzschild-(A)dS black hole.
Cross-sections for (n,2n), (n,α), (n,p),(n,d), and (n,t) reactions on molybdenum isotopes in the neutron energy range of 13 to 15 MeV
Junhua Luo, Li Jiang
Published: , doi: 10.1088/1674-1137/abaded
Given the insufficient cross-sectional data regarding the 14-MeV-neutron experiment of molybdenum, the vital fusion reactor structural material, and the significant heterogeneities among the reported values, this study examined the (n,2n), (n,α), (n,p), (n,d), and (n,t) reaction cross sections in molybdenum isotopes based on the neutrons produced via a T(d,n)4He reaction carried out in the Pd-300 Neutron Generator at the China Academy of Engineering Physics (CAEP). A high-resolution gamma-ray spectrometer, which was equipped with a coaxial high-purity germanium detector, was used to measure the product nuclear gamma activities. In addition, 27Al(n,α)24Na and 93Nb(n,2n)92mNb reactions were utilized as the neutron fluence standards. The experimental 92Mo(n,2n)91Mo, 94Mo(n,2n)93mMo, 100Mo(n,2n)99Mo, 98Mo(n,α)95Zr, 100Mo(n,α)97Zr, 92Mo(n,p)92mNb, 96Mo(n,p)96Nb, 97Mo(n,p)97Nb, 98Mo(n,p)98mNb, 92Mo(n,d)91mNb, and 92Mo(n,t)90Nb reaction cross sections were acquired within the 13–15 MeV neutron energy range. Thereafter, we compared and analyzed these obtained cross sections based on the existing IAEA-EXFOR database-derived experimental data, together with evaluation results corresponding to ENDF/B-VIII.0, JEFF-3.3, BROND-3.1, and CENDL-3.1 and the theoretical outcomes acquired through TALYS-1.95 and EMPIRE-3.2.3 (nuclear-reaction modeling tools).
Possibility of observation of hidden-bottom pentaquark resonances in bottomonium photoproduction on protons and nuclei near threshold
E. Ya. Paryev
Published: , doi: 10.1088/1674-1137/aba5f8
We study the $\Upsilon(1S)$ meson photoproduction on protons and nuclei at near-threshold center-of-mass energies below 11.4 GeV (or at the corresponding photon laboratory energies $E_{\gamma}$ below 68.8 GeV). We calculate the absolute excitation functions for the nonresonant and resonant photoproduction of $\Upsilon(1S)$ mesons off protons at incident photon laboratory energies of 63-68 GeV by considering direct (${\gamma}p \to {\Upsilon(1S)}p$) and two-step (${\gamma}p \to P^+_b(11080) \to {\Upsilon(1S)}p$, ${\gamma}p \to P^+_b(11125) \to {\Upsilon(1S)}p$, ${\gamma}p \to P^+_b(11130) \to {\Upsilon(1S)}p$) $\Upsilon(1S)$ production channels within different scenarios for the nonresonant total cross section of the elementary reaction ${\gamma}p \to {\Upsilon(1S)}p$ and for branching ratios of the decays $P^+_b(11080) \to {\Upsilon(1S)}p$, $P^+_b(11125) \to {\Upsilon(1S)}p$, and $P^+_b(11130) \to {\Upsilon(1S)}p$. We also calculate an analogous function for the photoproduction of $\Upsilon(1S)$ mesons on the 12C and 208Pb target nuclei in the near-threshold center-of-mass beam energy region of 9.0-11.4 GeV by considering the respective incoherent direct (${\gamma}N \to {\Upsilon(1S)}N$) and two-step (${\gamma}p \to P^+_b(11080) \to {\Upsilon(1S)}p$, ${\gamma}p \to P^+_b(11125) \to {\Upsilon(1S)}p$, ${\gamma}p \to P^+_b(11130) \to {\Upsilon(1S)}p$ and ${\gamma}n \to P^0_b$$ (11080) \to{\Upsilon(1S)}n $, ${\gamma}n \to P^0_b(11125) \to {\Upsilon(1S)}n$, ${\gamma}n \to P^0_b(11130) \to {\Upsilon(1S)}n$) $\Upsilon(1S)$) production processes using a nuclear spectral function approach. We demonstrate that a detailed scan of the$\Upsilon(1S)$ total photoproduction cross section on proton and nuclear targets in the near-threshold energy region in future high-precision experiments at the proposed high-luminosity electron-ion colliders EIC and EicC in the US and China should provide a definite result for or against the existence of the nonstrange hidden-bottom pentaquark states$P_{bi}^+$ and $P_{bi}^0$ ($i$=1, 2, 3) as well as clarify their decay rates.
Mesonic condensation in isospin matter under rotation
Hui Zhang, Defu Hou, Jin-Feng Liao
Published: , doi: 10.1088/1674-1137/abae4d
We investigate mesonic condensation in isospin matter under rotation. Using the two-flavor NJL effective model in the presence of global rotation, we demonstrate two important effects of rotation on its phase structure: a rotational suppression of the scalar-channel condensates, in particular, the pion condensation region; and a rotational enhancement of the rho condensation region with vector-channel condensate. A new phase diagram for isospin matter under rotation is mapped out on the $ \omega-\mu_I$ plane where the three distinct phases, corresponding to the $ \sigma,\; \pi, \;\rho$ -dominated regions, respectively, are separated by a second-order line at low isospin chemical potential as well as a first-order line at high rotation and are further connected at a tri-critical point.
The angular distributions of elastic scattering of 12,13C+Zr
Cui-Hua Rong, Gao-Long Zhang, Lin Gan, Zhi-Hong Li, L. C. Brandão, E. N. Cardozo, M. R. Cortes, Yun-Ju Li, Jun Su, Sheng-Quan Yan, Sheng Zeng, Gang Lian, Bing Guo, You-Bao Wang, Wei-Ping Liu, J. Lubian
Published: , doi: 10.1088/1674-1137/abab8d
To obtain the neutron spectroscopic amplitudes for ${}^{90-96}$Zr overlaps, experimental data of elastic scattering with small experimental errors and precise optical potentials were analyzed. In this study, the elastic scattering angular distributions of ${}^{12,13}$C + ${}^{A} {\rm{Zr}}$ (A = 90, 91, 92, 94, 96) were measured using the high-precision Q3D magnetic spectrometer in the Tandem accelerator. The São Paulo potential was used for the optical potential. The optical model and coupled channel calculations were compared with the experimental data. The theoretical results were found to be very close to the experimental data. In addition, the possible effects of the couplings to the inelastic channels of the ${}^A {\rm{Zr}}$ targets and ${}^{12, 13}$C projectiles on the elastic scattering were studied. It was observed that the couplings to the inelastic channels of the ${}^{12,13}$C projectiles could improve the agreement with the experimental data, while the inelastic couplings to the target states are of minor importance. The effect of the one-neutron stripping in the ${}^{13}$C+${}^A {\rm{Zr}}$ elastic scattering was also studied. The one-neutron stripping channel in ${}^{13}$C + ${}^A {\rm{Zr}}$ was found to be not relevant and did not affect the elastic scattering angular distributions. Our results also show that in the reactions with the considered zirconium isotopes, the presence of the extra neutron in ${}^{13}$C does not influence the reaction mechanism, which is governed by the collective excitation of the ${}^{12}$C core.
Orientation dichroism effect of proton scattering on deformed nuclei
Li Ou, Zhi-Gang Xiao
Published: , doi: 10.1088/1674-1137/abadf1
Proton-induced scattering of 238U nuclei, with spheroidal deformations at beam energies above 100 MeV, is simulated using an improved quantum molecular dynamics model. The angular distribution of the deflected protons is highly sensitive to the orientation of the symmetrical long axis of the target nuclei with respect to the beam direction. As a result, in reverse kinematic reactions, an orientation dichroism effect is predicted, implying that the absorption rate of the 238U beam by a proton target discerns between the parallel and perpendicular orientations of the deformed 238U nuclei.
Exploring physical properties of compact stars in ${ f(R,T)}$ -gravity: An embedding approach
Ksh. Newton Singh, Abdelghani Errehymy, Farook Rahaman, Mohammed Daoud
Published: , doi: 10.1088/1674-1137/abab88
Solving field equations exactly in $f(R,T)-$ gravity is a challenging task. To do so, many authors have adopted different methods such as assuming both the metric functions and an equation of state (EoS) and a metric function. However, such methods may not always lead to well-behaved solutions, and the solutions may even be rejected after complete calculations. Nevertheless, very recent studies on embedding class-one methods suggest that the chances of arriving at a well-behaved solution are very high, which is inspiring. In the class-one approach, one of the metric potentials is estimated and the other can be obtained using the Karmarkar condition. In this study, a new class-one solution is proposed that is well-behaved from all physical points of view. The nature of the solution is analyzed by tuning the $f(R,T)-$ coupling parameter $\chi$ , and it is found that the solution leads to a stiffer EoS for $\chi=-1$ than that for $\chi=1$ . This is because for small values of $\chi$ , the velocity of sound is higher, leading to higher values of $M_{\rm max}$ in the $M-R$ curve and the EoS parameter $\omega$ . The solution satisfies the causality condition and energy conditions and remains stable and static under radial perturbations (static stability criterion) and in equilibrium (modified TOV equation). The resulting $M-R$ diagram is well-fitted with observed values from a few compact stars such as PSR J1614-2230, Vela X-1, Cen X-3, and SAX J1808.4-3658. Therefore, for different values of $\chi$ , the corresponding radii and their respective moments of inertia have been predicted from the $M-I$ curve.
Analysis of the strong decays of Pc(4312) as a pentaquark molecular state with QCD sum rules
Zhi-Gang Wang, Xu Wang
Published: , doi: 10.1088/1674-1137/ababf7
In this article, we tentatively assign $P_c(4312)$ to be the $\bar{D}\Sigma_c$ pentaquark molecular state with the spin-parity $J^P={\frac{1}{2}}^-$, and discuss the factorizable and non-factorizable contributions in the two-point QCD sum rules for the $\bar{D}\Sigma_c$ molecular state in detail to prove the reliability of the single pole approximation in the hadronic spectral density. We study its two-body strong decays with the QCD sum rules, and special attention is paid to match the hadron side with the QCD side of the correlation functions to obtain solid duality. We obtain the partial decay widths $\Gamma\left(P_c(4312)\to \eta_c p\right)=0.255\,\,{\rm{MeV}}$ and $\Gamma\left(P_c(4312)\to J/\psi p\right)=9.296^{+19.542}_{-9.296}\,\,{\rm{MeV}}$, which are compatible with the experimental value of the total width, and support assigning $P_c(4312)$ to be the $\bar{D}\Sigma_c$ pentaquark molecular state.
Durgapal IV model considering the minimal geometric deformation approach
Francisco Tello-Ortiz, Ángel Rincón, Piyali Bhar, Y. Gomez-Leyton
Published: , doi: 10.1088/1674-1137/aba5f7
The present article reports the study of local anisotropic effects on Durgapal's fourth model in the context of gravitational decoupling via the minimal geometric deformation approach. To achieve this, the most general equation of state relating the components of the $\theta$−sector is imposed to obtain the decoupler function $f(r)$. In addition, certain properties of the obtained solution, such as the behavior of the salient material content threading the stellar interior; causality and energy conditions; hydrostatic balance through the modified Tolman−Oppenheimer−Volkoff conservation equation and stability mechanism against local anisotropies using the adiabatic index; sound velocity of the pressure waves; convection factor; and the Harrison−Zeldovich−Novikov procedure, are investigated to check whether the model is physically admissible or not. Regarding the stability analysis, it is found that the model presents unstable regions when the sound speed of the pressure waves and convection factor are used in distinction with the adiabatic index and Harrison−Zeldovich−Novikov case. To produce a more realistic picture, the numerical data for some known compact objects were determined and different values of the parameter $\alpha$ were considered to compare with the GR case, i.e., $\alpha=0$.
Decay properties of the Zc(3900) through the Fierz rearrangement
Hua-Xing Chen
Published: , doi: 10.1088/1674-1137/abae4b
We systematically construct all the tetraquark currents/operators of $J^{PC} = 1^{+-}$ with the quark configurations $[cq][\bar c \bar q]$, $[\bar c q][\bar q c]$, and $[\bar c c][\bar q q]$ ($q=u/d$), and derive their relations through the Fierz rearrangement of the Dirac and color indices. Using the transformations of $[qc][\bar q \bar c] \to [\bar c c][\bar q q]$ and $[\bar c q][\bar q c]$, we study decay properties of the $Z_c(3900)$ as a compact tetraquark state; while using the transformation of $[\bar c q][\bar q c] \to [\bar c c][\bar q q]$, we study its decay properties as a hadronic molecular state.
Yield ratio of hypertriton to light nuclei in heavy-ion collisions from ${ \sqrt{{ s}_{{NN}}}}$ = 4.9 GeV to 2.76 TeV
Tian-Hao Shao, Jin-Hui Chen, Che Ming Ko, Kai-Jia Sun, Zhang-Bu Xu
Published: , doi: 10.1088/1674-1137/abadf0
We argue that the difference in the yield ratio ${{{S}}_{\rm{3}}} = \dfrac{{{{{N}}_{_\Lambda ^3{\rm{H}}}}/{{{N}}_\Lambda }}}{{{{{N}}_{^3{\rm{He}}}}/{{{N}}_{{p}}}}}$ measured in Au+Au collisions at $\rm \sqrt{s_{NN}}$ = 200 GeV and in Pb-Pb collisions at $\rm \sqrt{s_{NN}}$ = 2.76 TeV is mainly owing to the different treatment of the weak decay contribution to the proton yield in the Au+Au collisions at $\rm \sqrt{s_{NN}}$ = 200 GeV. We then use the coalescence model to extract from measured $\rm S_3$ the information about the $\Lambda$ and nucleon density fluctuations at the kinetic freeze-out of heavy-ion collisions. We also show, using available experimental data, that the yield ratio ${{{S}}_{\rm{2}}} = \dfrac{{{{{N}}_{_\Lambda ^3{\rm{H}}}}}}{{{{{N}}_\Lambda }{{{N}}_{{d}}}}}$ is a more promising observable than $\rm S_3$ for probing the local baryon-strangeness correlation in the produced medium.
Calculations of the α-decay properties of Z = 120, 122, 124, 126 isotopes
Zhishuai Ge, Gen Zhang, Shihui Cheng, Yu. S. Tsyganov, Feng-Shou Zhang
Published: , doi: 10.1088/1674-1137/abab00
The $\alpha$-decay properties of even-Z nuclei with Z = 120, 122, 124, 126 are predicted. We employ the generalized liquid drop model (GLDM), Royer's formula, and universal decay law (UDL) to calculate the $\alpha$-decay half-lives. By comparing the theoretical calculations with the experimental data of known nuclei from Fl to Og, we confirm that all the employed methods can reproduce the $\alpha$-decay half-lives well. The preformation factor $P_{\alpha}$ and $\alpha$-decay energy $Q_{\alpha}$ show that $^{298,304,314,316,324,326,338,348}$120, $^{304,306,318,324,328,338}$122, and $^{328,332,340,344}$124 might be stable. The $\alpha$-decay half-lives show a peak at Z = 120, N = 184, and the peak vanishes when Z = 122, 124, 126. Based on detailed analysis of the competition between $\alpha$-decay and spontaneous fission, we predict that nuclei nearby N = 184 undergo $\alpha$-decay. The decay modes of $^{287-339}$120, $^{294-339}$122, $^{300-339}$124, and $^{306-339}$126 are also presented.
Running vacuum model in a non-flat universe
Chao-Qiang Geng, Yan-Ting Hsu, Lu Yin, Kaituo Zhang
Published: , doi: 10.1088/1674-1137/abab86
We investigate observational constraints on the running vacuum model (RVM) of $\Lambda=3\nu (H^{2}+K/a^2)+c_0$ in a spatially curved universe, where $\nu$ is the model parameter, $K$ corresponds to the spatial curvature constant, $a$ represents the scalar factor, and $c_{0}$ is a constant defined by the boundary conditions. We study the CMB power spectra with several sets of $\nu$ and $K$ in the RVM. By fitting the cosmological data, we find that the best fitted $\chi^2$ value for RVM is slightly smaller than that of $\Lambda$CDM in the non-flat universe, along with the constraints of $\nu\leqslant O(10^{-4})$ (68% C.L.) and $|\Omega_K=-K/(aH)^2|\leqslant O(10^{-2})$ (95% C.L.). In particular, our results favor the open universe in both $\Lambda$CDM and RVM. In addition, we show that the cosmological constraints of $\Sigma m_{\nu}=0.256^{+0.224}_{-0.234}$ (RVM) and $\Sigma m_{\nu}=0.257^{+0.219}_{-0.234}$ ($\Lambda$CDM) at 95% C.L. for the neutrino mass sum are relaxed in both models in the spatially curved universe.
Equation of state and chiral transition in soft-wall AdS/QCD with a more realistic gravitational background
Zhen Fang, Yue-Liang Wu
Published: , doi: 10.1088/1674-1137/abab90
We construct an improved soft-wall AdS/QCD model with a cubic coupling term of the dilaton and the bulk scalar field. The background fields in this model are solved by the Einstein-dilaton system with a nontrivial dilaton potential, which has been shown to reproduce the equation of state from the lattice QCD with two flavors. The chiral transition behaviors are investigated in the improved soft-wall AdS/QCD model with the solved gravitational background, and the crossover transition can be realized. Our study provides the possibility to address the deconfining and chiral phase transitions simultaneously in the bottom-up holographic framework.
Studying the localized CP violation and the branching fraction of the ${\bar{B}^0\rightarrow K^-\pi^+\pi^+\pi^-}$ decay
Jing-Juan Qi, Zhen-Yang Wang, Jing Xu, Xin-Heng Guo
Published: , doi: 10.1088/1674-1137/abac00
In this work, we study the localized $ CP $ violation and the branching fraction of the four-body decay $ \bar{B}^0\rightarrow K^-\pi^+\pi^-\pi^+ $ by employing a quasi-two-body QCD factorization approach. Considering the interference of $ \bar{B}^0\rightarrow \bar{K}_0^*(700)\rho^0(770)\rightarrow K^-\pi^+\pi^-\pi^+ $ and $ \bar{B}^0\rightarrow \bar{K}^*(892)f_0(500)\rightarrow K^-\pi^+\pi^-\pi^+ $ channels, we predict $ \mathcal{A_{CP}}(\bar{B}^0\rightarrow K^-\pi^+\pi^-\pi^+)\in [0.15,0.28] $ and $ {\cal{B}}(\bar{B}^0\rightarrow K^-\pi^+\pi^-\pi^+)\in[1.73,5.10]\times10^{-7} $, respectively, which shows that the interference mechanism of these two channels can induce the localized $ CP $ violation to this four-body decay. Meanwhile, within the two quark model framework for the scalar mesons $ f_0(500) $ and $ \bar{K}_0^*(700) $, we calculate the direct CP violations and branching fractions of the $ \bar{B}^0\rightarrow \bar{K}_0^*(700)\rho^0(770) $ and $ \bar{B}^0\rightarrow \bar{K}^*(892)f_0(500) $ decays, respectively. The corresponding results are $ \mathcal{A_{CP}}(\bar{B}^0\rightarrow \bar{K}_0^*(700)\rho^0(770)) \in [0.20, 0.36] $, $ \mathcal{A_{CP}}(\bar{B}^0\rightarrow \bar{K}^*(892)f_0(500))\in [0.08, 0.12] $, ${\cal{B}} (\bar{B}^0\rightarrow \bar{K}_0^*(700) \rho^0(770)\in [6.76, 18.93]\times10^{-8}$ and $ {\cal{B}} (\bar{B}^0\rightarrow \bar{K}^*(892)f_0(500))\in [2.66, 4.80]\times10^{-6} $, indicating that the $ CP $ violations of these two-body decays are both positive and the branching fractions quite different. These studies provide a new way to investigate the aforementioned four-body decay and can be helpful in clarifying the configuration of the structure of the light scalar meson.
Multi-pole dark energy
Chao-Jun Feng, Xiang-Hua Zhai, Xin-Zhou Li
Published: , doi: 10.1088/1674-1137/aba5f9
A scalar field with a pole in its kinetic term is often used to study cosmological inflation; it can also play the role of dark energy, which is called the pole dark energy model. We propose a generalized model where the scalar field may have two or even multiple poles in the kinetic term, and we call it the multi-pole dark energy. We find that the poles can place some restrictions on the values of the original scalar field with a non-canonical kinetic term. After the transformation to the canonical form, we get a flat potential for the transformed scalar field even if the original field has a steep one. The late-time evolution of the universe is obtained explicitly for the two pole model, while dynamical analysis is performed for the multiple pole model. We find that it does have a stable attractor solution, which corresponds to the universe dominated by the potential of the scalar field.
$ {{ \Lambda}{ \Lambda}{ N} { -} { \Xi} { N}{ N}} $ S wave resonance
H. Garcilazo, A. Valcarce
Published: , doi: 10.1088/1674-1137/abab8c
We use an existing model of the $ \Lambda\Lambda N - \Xi NN $ three-body system based on two-body separable interactions to study the $ (I,J^P) = (1/2,1/2^+) $ three-body channel. For the $ \Lambda\Lambda $, $ \Xi N $, and $ \Lambda\Lambda - \Xi N $ amplitudes, we have constructed separable potentials based on the most recent results of the HAL QCD Collaboration. They are characterized by the existence of a resonance just below or above the $ \Xi N $ threshold in the H-dibaryon channel, $ (i,j^p) = (0,0^+) $. A three-body resonance appears 2.3 MeV above the $ \Xi d $ threshold. We show that if the $ \Lambda\Lambda - \Xi N $ H-dibaryon channel is not considered, the $ \Lambda\Lambda N - \Xi NN $ S wave resonance disappears. Thus, the possible existence of a $ \Lambda\Lambda N - \Xi NN $ resonance would be sensitive to the $ \Lambda\Lambda - \Xi N $ interaction. The existence or nonexistence of this resonance could be evidenced by measuring, for example, the $ \Xi d $ cross section.
Revisiting black hole thermodynamics in massive gravity: charged particle absorption and infalling shell of dust
Shi-Qian Hu, Bo Liu, Xiao-Mei Kuang, Rui-Hong Yue
Published: , doi: 10.1088/1674-1137/abab8a
In this study, we apply two methods to consider the variation of massive black holes in both normal and extended thermodynamic phase spaces. The first method considers a charged particle being absorbed by the black hole, whereas the second considers a shell of dust falling into it. With the former method, the first and second laws of thermodynamics are always satisfied in the normal phase space; however, in the extended phase space, the first law is satisfied but the validity of the second law of thermodynamics depends upon the model parameters. With the latter method, both laws are valid. We argue that the former method's violation of the second law of thermodynamics may be attributable to the assumption that the change of internal energy of the black hole is equal to the energy of the particle. Finally, we demonstrate that the event horizon always ensures the validity of weak cosmic censorship in both phase spaces; this means that the violation of the second law of thermodynamics, arising under the aforementioned assumption, does not affect the weak cosmic censorship conjecture. This further supports our argument that the assumption in the first method is responsible for the violation and requires deeper treatment.
Quantum ekpyrotic mechanism in Fermi-bounce curvaton cosmology
Andrea Addazi, Antonino Marciano
Published: , doi: 10.1088/1674-1137/aba58d
Within the context of the Fermi-bounce curvaton mechanism, we analyze the one-loop radiative corrections to the four-fermion interaction, generated by the non-dynamical torsion field in the Einstein-Cartan-Holst-Sciama-Kibble theory. We show that contributions that arise from the one-loop radiative corrections modify the energy-momentum tensor, mimicking an effective Ekpyrotic fluid contribution. Therefore, we call this effect quantum Ekpyrotic mechanism. This leads to the dynamical washing out of anisotropic contributions to the energy-momentum tensor, without introducing any new extra Ekpyrotic fluid. We discuss the stability of the bouncing mechanism and derive the renormalization group flow of the dimensional coupling constant ξ, checking whether any change of its sign takes place towards the bounce. This enforces the theoretical motivations in favor of the torsion curvaton bounce cosmology as an alternative candidate to the inflation paradigm.
Quenching of ${ \gamma_{0}}$ transition results from 2p-1h doorway mechanism by p-wave neutron excitation
Tao-Feng Wang, Xiao-Ting Yang, T. Katabuchi, Zi-Ming Li, Zhi-Bo Xu, G. N. Kim, T. I. Ro, Ying-Lu Han, Li-Hua Zhu, M. Igashira
The ratio of $\gamma$ transition-intensities from the initial capture state to low-lying states may represent the model-independent $\gamma$-strength function, which reflects the effects of different neutron-capture reaction mechanisms. The extraordinary quenching of the $\gamma_{0}$ transition from the p-wave neutron radiative capture in $^{57}$Fe is observed, for the first time, from the pronounced enhancement of the $\gamma$-strength function ratios $f_{\gamma_{1}}/f_{\gamma_{0}}$ and $f_{\gamma_{2}}/f_{\gamma_{0}}$. The 2p-1h doorway excitation leads to suppression of the $\gamma_{0}$ transition to the ground state and the enhancement of the $\gamma_{1}$ and $\gamma_{2}$ transitions to the first and second excited states, respectively. The $fp$ sub-shells supply the exact number of spaces required for the 2p-1h configuration, which features the neutron capture mechanism in the vicinity of A = 55.
Jet quenching parameter from a soft wall AdS/QCD model
Xiangrong Zhu, Zi-qiang Zhang
We study the effect of chemical potential and nonconformality on the jet quenching parameter in a holographic QCD model with conformal invariance broken by background dilaton. The presence of chemical potential and nonconformality both increase the jet quenching parameter, thus enhancing the energy loss, consistently with the findings of the drag force.
Transverse momentum balance and angular distribution of ${{b\bar{b}}}$ dijets in Pb + Pb collisions
Wei Dai, Sa Wang, Shan-Liang Zhang, Ben-Wei Zhang, Enke Wang
In this study, the production of inclusive b-jet and $b\bar{b}$ dijets in Pb + Pb collisions has been investigated by considering the in-medium evolution of heavy and light quarks simultaneously. The initial hard processes of inclusive b-jet and $b\bar{b}$ dijets production are described using a next-to-leading order (NLO) plus parton shower Monte Carlo (MC) event generator, SHERPA, which can be well matched with the experimental data in p + p collisions. The framework uses the Langevin transport model to describe the evolution of the bottom quark. Furthermore, the collisional energy loss and higher-twist description are considered to determine the radiative energy loss from both the bottom and light quarks. We compare the theoretical simulation of the inclusive jet and b-jet $R_{\rm AA}$ in the Pb + Pb collisions at $\sqrt{s_{ NN}}=2.76$ TeV with the experimental data and present the theoretical simulation of the momentum balance of the $b\bar{b}$ dijet in the Pb + Pb collisions at $5.02$ TeV along with recent CMS data for the first time. A similar trend to that seen in inclusive dijets is observed in $b\bar{b}$ dijets; the distribution of the production shifts to smaller $x_{\rm J}$ owing to the jet quenching effect. Finally, we report the prediction of the normalized azimuthal angle distribution of the $b\bar{b}$ dijet in the Pb + Pb collisions at $5.02$ TeV. The medium-induced energy loss effect of the $b\bar{b}$ dijets will generally suppress its production; however, the same side ($\Delta \phi \to 0$ region) suffers more energy loss than the far side ($\Delta \phi \to \pi$ region), thus leading to suppression on the same side and enhancement on the far side in the normalized azimuthal angle distribution in A + A collisions.
Logarithmic Regge pole
S. D. Campos
This work presents the subtraction procedure and the Regge cut in the logarithmic Regge pole approach. The subtraction mechanism leads to the same asymptotic behavior as previously obtained in the non-subtraction case. The Regge cut, in contrast, introduces a clear role to the non-leading contributions for the asymptotic behavior of the total cross-section. From these results, some simple parameterization is introduced to fit the experimental data for the proton-proton and antiproton-proton total cross-section above some minimum value up to the cosmic-ray. The fit parameters obtained are used to present predictions for the $ \rho(s)$-parameter as well as to the elastic slope $ B(s)$ at high energies.
Measurement of away-side broadening with self-subtraction of flow in Au+Au collisions at ${{\sqrt{s_{NN}} = 200}}$ GeV
J. Adam, L. Adamczyk, J. R. Adams, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, D. M. Anderson, A. Aparin, E. C. Aschenauer, M. U. Ashraf, F. G. Atetalla, A. Attri, G. S. Averichev, V. Bairathi, K. Barish, A. Behera, R. Bellwied, A. Bhasin, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. D. Brandenburg, A. V. Brandin, J. Butterworth, H. Caines, M. Calderón de la Barca Sánchez, D. Cebra, I. Chakaberia, P. Chaloupka, B. K. Chan, F-H. Chang, Z. Chang, N. Chankova-Bunzarova, A. Chatterjee, D. Chen, J. H. Chen, X. Chen, Z. Chen, J. Cheng, M. Cherney, M. Chevalier, S. Choudhury, W. Christie, X. Chu, H. J. Crawford, M. Csanád, M. Daugherity, T. G. Dedovich, I. M. Deppner, A. A. Derevschikov, L. Didenko, X. Dong, J. L. Drachenberg, J. C. Dunlop, T. Edmonds, N. Elsey, J. Engelage, G. Eppley, S. Esumi, O. Evdokimov, A. Ewigleben, O. Eyser, R. Fatemi, S. Fazio, P. Federic, J. Fedorisin, C. J. Feng, Y. Feng, P. Filip, E. Finch, Y. Fisyak, A. Francisco, L. Fulek, C. A. Gagliardi, T
Published: , doi: 10.1088/1674-1137/ab97a9
High transverse momentum ($ p_T $) particle production is suppressed owing to the parton (jet) energy loss in the hot dense medium created in relativistic heavy-ion collisions. Redistribution of energy at low-to-modest $ p_T $ has been difficult to measure, owing to large anisotropic backgrounds. We report a data-driven method for background evaluation and subtraction, exploiting the away-side pseudorapidity gaps, to measure the jetlike correlation shape in Au+Au collisions at $\sqrt{s_{{NN}}} = 200$ GeV in the STAR experiment. The correlation shapes, for trigger particles $ p_T>3\;{\rm{GeV}}/{\rm{c}} $ and various associated particle $ p_T $ ranges within $ 0.5<p_T<10\;{\rm{GeV}}/{\rm{c}} $, are consistent with Gaussians, and their widths increase with centrality. The results indicate jet broadening in the medium created in central heavy-ion collisions.