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Observational constraint on the dark energy scalar field
Ming-Jian Zhang, Hong Li
Published: , doi: 10.1088/1674-1137/abe0bf
Abstract:
In this paper, we study three scalar fields, namely the quintessence, phantom, and tachyon fields, to explore the source of dark energy via the Gaussian processes method from the background and perturbation growth rate data. The corresponding reconstructions suggest that the dark energy should be dynamical. Moreover, the quintom field, which is a combination of the quintessence and phantom fields, is powerfully favored by the reconstruction. The mean values indicate that the potential $ V(\phi) $ in the quintessence field is a double exponential function, whereas $ V(\phi) $ in the phantom field is a double Gaussian function. This reconstruction can provide an important reference for the scalar field study. The two types of data employed reveal that the tachyon field is disadvantageous for describing the cosmic acceleration.
Measurement of 59Co(n, x) reaction cross sections with the fast neutrons based on the 9Be(p, n) reaction
Muhammad Zaman, Muhammad Nadeem, Muhammad Sahid, Kwangsoo Kim, Guinyun Kim, Nguyen Thi Hien
Published: , doi: 10.1088/1674-1137/abe196
Abstract:
The cross sections of the 59Co(n, x) reaction in the average energy range of 15.2-37.2 MeV were measured using activation and an off-line γ-ray spectrometric technique. The neutrons were generated from the 9Be(p, n) reaction with proton beam energies of 25-45 MeV at the MC-50 Cyclotron facility of the Korean Institute of Radiological and Medical Sciences (KIRAMS). Theoretical calculations of neutron–induced reactions on 59Co were performed using the nuclear model code TALYS-1.9. The results for the 59Co(n, x) reactions were compared with the theoretical values obtained using TALYS-1.9 and the literature data provided in EXFOR and the TENDL 2019 nuclear data library. The theoretical values obtained using TALYS-1.9 with adjusted parameters are comparable to the experimental data. The measured reaction cross sections of a few radionuclides are new, and the others are comparable to the literature data, and thus, they can strengthen the database. The present study on cross sections leads to useful insight into the mechanisms of 59Co(n, x) reactions.
An improved semi-empirical relationship for cluster radioactivity
Yanzhao Wang, Fengzhu Xing, Yang Xiao, Jianzhong Gu
Published: , doi: 10.1088/1674-1137/abe112
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An improved semi-empirical relationship for cluster radioactivity half-lives is proposed by introducing an accurate charge radius formula and an analytic expression of the preformation probability. Moreover, the cluster radioactivity half-lives for the daughter nuclei around 208Pb or its neighbors and the 12C radioactivity half-life of 114Ba are calculated within the improved semi-empirical relationship. It is shown that the accuracy of the new relationship is improved significantly compared to its predecessor. In addition, the cluster radioactivity half-lives that are experimentally unavailable for the trans-lead and trans-tin nuclei are predicted by the new semi-empirical formula. These predictions might be useful for searching for the new cluster emitters of the two islands in future experiments.
Phase transition and quasinormal modes for charged black holes in 4D Einstein-Gauss-Bonnet gravity
Ming Zhang, Chao-Ming Zhang, De-Cheng Zou, Rui-Hong Yue
Published: , doi: 10.1088/1674-1137/abe19a
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In four-dimensional Einstein-Gauss-Bonnet (EGB) gravity, we consider the thermodynamic and phase transitions of (charged) AdS black holes. For the negative GB coefficient $ \alpha<0 $, the system allows two physical critical points, corresponding to the reentrant phase transition, when the charge $ Q>2\sqrt{-\alpha} $. For arbitrary $ \alpha>0 $, the system always leads to a van der Waals phase transition. We then study the quasinormal modes (QNMs) of massless scalar perturbations to probe the van der Waals-like phase transition between small and large black holes (SBH/LBH) for (charged) AdS black holes. We find that the signature of this SBH/LBH phase transition in the isobaric process can be detected since the slopes of the QNM frequencies change dramatically in small and large black holes near the critical point. The obtained results further support that QNMs can be a dynamic probe of thermodynamic properties in black holes.
Dynamics of k-essence in loop quantum cosmology
Jiali Shi, Jian-Pin Wu
Published: , doi: 10.1088/1674-1137/abe111
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In this paper, we study the dynamics of k-essence in loop quantum cosmology (LQC). The study indicates that the loop quantum gravity (LQG) effect plays a key role only in the early epoch of the universe and is diluted in the later stages. The fixed points in LQC are basically consistent with those in standard Friedmann-Robertson-Walker (FRW) cosmology. For most of the attractor solutions, the stability conditions in LQC are in agreement with those for the standard FRW universe. For some special fixed points, however, tighter constraints are imposed thanks to the LQG effect.
Multiscalar B-L extension based on S4 flavor symmetry for neutrino masses and mixing
V. V. Vien, H. N. Long
Published: , doi: 10.1088/1674-1137/abe1c7
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A multiscalar and nonrenormalizable $B-L$ extension of the standard model (SM) with $S_4$ symmetry which successfully explains the recently observed neutrino oscillation data is proposed. The tiny neutrino masses and their hierarchies are generated via the type-I seesaw mechanism. The model reproduces the recent experiments of neutrino mixing angles and Dirac CP violating phase in which the atmospheric angle $(\theta_{23})$ and the reactor angle $(\theta_{13})$ get the best-fit values while the solar angle $(\theta_{12})$ and Dirac CP violating phase ($\delta $) are in $3\, \sigma $ range of the best-fit value for the normal hierarchy (NH). For the inverted hierarchy (IH), $\theta_{13}$ gets the best-fit value and $\theta_{23}$ together with $\delta $ are in the $1\, \sigma $ range, while $\theta_{12}$ is in $3\, \sigma $ range of the best-fit value. The effective neutrino masses are predicted to be $\langle m_{ee}\rangle=6.81 \,\, {\rm{meV}}$ for the NH and $\langle m_{ee}\rangle=48.48\,\, {\rm{meV}}$ for the IH, in good agreement with the most recent experimental data.
Systematic study of two-proton radioactivity within a Gamow-like model
Hong-Ming Liu, Xiao Pan, You-Tian Zou, Jiu-Long Chen, Jun-Hao Cheng, Biao He, Xiao-Hua Li
Published: , doi: 10.1088/1674-1137/abe10f
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In this study, based on the Gamow-like model, we systematically analyze two-proton ($2p$) radioactivity half-lives of nuclei near or beyond the proton drip line. It is found that the calculated results can reproduce experimental data well. Furthermore, using this model, we predict the half-lives of possible $2p$ radioactivity candidates whose $2p$ radioactivity is energetically allowed or observed but not yet quantified in the latest table of evaluated nuclear properties, i.e., NUBASE2016. The predicted results are in good agreement with those from other theoretical models and empirical formulas, namely the effective liquid drop model (ELDM), generalized liquid drop model (GLDM), Sreeja formula, and Liu formula.
Weak decays of doubly heavy baryons: ${{\cal{B}}_{{cc}}\to {\cal{B}} D^{(*)}} $
Run-Hui Li, Juan-Juan Hou, Bei He, Ya-Ru Wang
Published: , doi: 10.1088/1674-1137/abe0bc
Abstract:
The discovery of $ \Xi_{cc}^{++} $ has inspired new interest in studying doubly heavy baryons. In this study, the weak decays of a doubly charmed baryon $ {\cal B}_{cc} $ to a light baryon $ {\cal B} $ and a charm meson $ D^{(*)} $ (either a pseudoscalar or a vector one) are calculated. Following our previous work, we calculate the short distance contributions under the factorization hypothesis, whereas the long distance contributions are modeled as the final state interactions, which are calculated with the one particle exchange model. We find that the $ {\cal B}_{cc}\to {\cal B} D^{*} $ decays' branching ratios are obviously larger, as they receive contributions of more polarization states. Among the decays that we investigate, the following have the largest branching fractions: $ {\cal BR}(\Xi_{cc}^{++}\rightarrow\Sigma^{+}D^{*+}) \in [0.46 \%, 3.33 \%] $ estimated with $ \tau_{\Xi_{cc}^{++}} = 256 $ fs; $ {\cal BR}(\Xi_{cc}^{+}\rightarrow\Lambda D^{*+}) \in [0.38 \%, 2.63 \%] $ and $ {\cal BR}(\Xi_{cc}^{+}\rightarrow\Sigma^{0} D^{*+}) \in [0.45 \%, 3.16 \%] $ with $ \tau_{\Xi_{cc}^+} = 45 $ fs; and ${\cal BR}(\Omega_{cc}^{+}\rightarrow \Xi^{0} D^{*+}) \in [0.27 \%, 1.03 \%]$, $ {\cal BR}(\Omega_{cc}^{+}\rightarrow\Xi^{0} D^{+}) \in [0.07 \%, 0.44 \%] $, and $ {\cal BR}(\Omega_{cc}^{+}\rightarrow\Sigma^{0} D^{*+}) \in [0.06 \%, 0.45 \%] $ with $ \tau_{\Omega_{cc}^+} = 75 $ fs. By comparing the decay widths of pure color commensurate channels with those of pure bow-tie ones, we find that the bow-tie mechanism plays an important role in charm decays.
Production of super-heavy nuclei in cold fusion reactions
V. Yu. Denisov, I. Yu. Sedykh
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A model for cold-fusion reactions related to the synthesis of super-heavy nuclei in collisions of heavy projectile-nuclei with a 208Pb target nucleus is discussed. In the framework of this model, the production of the compound nucleus by two paths, the di-nuclear system path and the fusion path, are taken into account simultaneously. The formation of the compound nucleus in the framework of the di-nuclear system is related to the transfer of nucleons from the light nucleus to the heavy one. The fusion path is linked to the sequential evolution of the nuclear shape from the system of contacting nuclei to the compound nucleus. It is shown that the compound nucleus is mainly formed by the fusion path in cold-fusion reactions. The landscape of the potential energy related to the fusion path is discussed in detail. This landscape for very heavy nucleus-nucleus systems has an intermediate state, which is linked to the formation of both the compound nucleus and the quasi-fission fragments. The decay of the intermediate state is taken into account in the calculation of the compound nucleus production cross sections and the quasi-fission cross sections. The values of the cold-fusion cross sections obtained in the model agree well with the experimental data.
A comparison of condensate mass of QCD vacuum between Wilson line approach and Schwinger effect
Sara Tahery, Xurong Chen, Liping Zou
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We studied the condensate mass of QCD vacuum through the duality approach via dilaton wall background in the presence of the parameter $ c $, which represents the condensation in a holographic set up. First, from Wilson line calculation, we found $ m_0^2 $ (i.e., the condensate parameter in mixed non-local condensation), whose behavior mimics that of QCD. The value of $ m_0^2 $ that we found by this approach is in agreement with QCD data. Second, we considered the produced mass $ m $ via the Schwinger effect mechanism in the presence of the parameter $ c $. We show that vacuum condensation generally contributes the mass dominantly and that the produced mass via Schwinger effect is suppressed by $ m_0 $.
Study of the dinuclear system for 296119 superheavy compound nucleus in fusion reactions
J. Mohammadi, O. N. Ghodsi
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Abstract:
This investigation aims to find an appropriate dinuclear system for the formation of ${}^{296}$119 superheavy compound nucleus. By studying the driving potential and measuring the capture cross section of the reactions, the evolution of the dinuclear system can be understood. In this study, we obtained capture, fusion, and evaporation residue cross sections and survival probability at energies near the Coulomb barrier for four reactions, namely $^{45}$Sc + $^{251}$Cf, $^{42}$Ca + $^{254}$Es, $^{39}$K + $^{257}$Fm, and $^{38}$Ar + $^{258}$Md. Our calculations show that the reaction $^{38}$Ar + $^{258}$Md is a suitable choice for the formation of an element with 119 protons among the studied reactions from a theoretical viewpoint.
Higgsino asymmetry and direct-detection constraints of light dark matter in the NMSSM with non-universal Higgs masses
Kun Wang, Jingya Zhu, Quanlin Jie
Published: , doi: 10.1088/1674-1137/**/*/******
Abstract:
In this study, we analyze the direct-detection constraints of light dark matter in the next-to minimal supersymmetric standard model (NMSSM) with non-universal Higgs masses (NUHM); we specially focus on the correlation between higgsino asymmetry and spin-dependent (SD) cross section. We draw the following conclusions. (i) The SD cross section is proportional to the square of higgsino asymmetry in dark matter $\tilde{\chi}^0_1$ in the NMSSM-NUHM, and hence, it is small for highly singlino-dominated dark matter. (ii) The higgsino-mass parameter $\mu_{\rm{eff}}$ is smaller than approximately $335\;{\rm{GeV}}$ in the NMSSM-NUHM due to the current muon g-2 constraint, but our scenario with light dark matter can still be alive under current constraints including the direct detection of dark matter in the spin-dependent channel. (iii) With a sizeable higgsino component in the light dark matter, the higgsino asymmetry and SD cross section can also be sizeable, but dark matter relic density is always small; thus, it can escape the direct detections. (iv) Light dark matter in the $h_2$- and Z-funnel annihilation channels with sufficient relic density can be covered by future LUX-ZEPLIN (LZ) 7-ton in SD detections. (v) The spin-independent (SI) cross section is dominated by $h_1$- and $h_2$-exchanging channels, which can even cancel each other in some samples, leaving an SI cross section smaller by a few orders of magnitude than that of one individual channel.
Polarized light-by-light scattering at the CLIC induced by axion-like particles
S.C. İnan, A.V. Kisselev
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In this study, light-by-light (LBL) scattering with initial polarized Compton backscattered photons at the CLIC, induced by axion-like particles (ALPs), is investigated. The total cross sections are calculated assuming CP-even coupling of the pseudoscalar ALP to photons. The 95% C.L. exclusion region for the ALP mass $m_a$ and its coupling constant f is presented. The results are compared with CLIC bounds previously obtained for the unpolarized case. It is shown that the bounds on f for the polarized beams in the region $m_a = 1000 - 2000 \;{\rm{GeV}}$ with collision energy of 3000 GeV and integrated luminosity of 4000 fb$^{-1}$ are on average 1.5 times stronger than the bounds for the unpolarized beams. Moreover, our CLIC bounds are stronger than those for all current exclusion regions for $m_a > 80$ GeV. In particular, they are more restrictive than the limits that follow from the ALP-mediated LBL scattering at the LHC.
Confinement and the global SU(3) color symmetry
Ying Chen
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Abstract:
The global $ SU(3) $ color symmetry and its physical consequences are discussed. The Nöther current is actually governed by the conserved matter current of color charges if the color field generated by this charge is properly polarized. The color field strength of a charge can have a uniform part due to the nontrivial QCD vacuum field and the nonzero gluon condensate, which implies that the self-energy of a system with a net color charge is infinite and, therefore, cannot exist as a free state. This is precisely what color confinement means. Accordingly, the Cornell type potential with the feature of Casimir scaling is derived for a color singlet system composed of a static color charge and an anti-charge. The uniform color field also implies that a hadron has a minimal size and minimal energy. Furthermore, the global $ SU(3) $ color symmetry requires that the minimal irreducible color singlet systems can only be $ q\bar{q} $, $ qqq $, $ gg $, $ ggg $, $ q\bar{q}g $, $ qqqg $, $ \bar{q}\bar{q}\bar{q}g $, etc., therefore a multi-quark system can only exist as a molecular configuration if there are no other binding mechanisms.
α-decay study of 218Ac and 221Th in 40Ar+186W reaction
Wei Hua, Zhiyuan Zhang, Long Ma, Zaiguo Gan, Huabin Yang, Minghui Huang, Chunli Yang, Mingming Zhang, Yulin Tian, Xiaohong Zhou, Cenxi Yuan, Caiwan Shen, Long Zhu
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Abstract:
In this study, 218Ac and 221Th nuclides were produced via the heavy-ion induced fusion evaporation reaction 40Ar + 186W. Their decay properties were studied with the help of the gas-filled recoil spectrometer SHANS and a digital data acquisition system. The cross section ratio between 222Pa and 218Ac was extracted experimentally, with measured value 0.69(9). Two new possible α decay branches to 221Th are suggested. The valence neutron configurations for the daughter 217Ra are discussed in terms of the hindrance factors.
Anisotropic stellar structures in the ${{f(T)}} $ theory of gravity with quintessence via embedding approach
Allah Ditta, Mushtaq Ahmad, Ibrar Hussain, G. Mustafa
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This work suggests a new model for anisotropic compact stars with quintessence in $f(T)$ gravity by using the off-diagonal tetrad and the power-law as $f(T)=\beta T^n$, where T is the scalar torsion and $\beta$ and n are real constants. The acquired field equations incorporating the anisotropic matter source along with the quintessence field, in $f(T)$ gravity, are investigated by making use of the specific character of the scalar torsion T for the observed stars ${\rm{PSRJ1614}}-2230$, $4U 1608-52$, ${\rm{Cen}} X-3$, ${\rm{EXO1785}}-248$, and $SMC X-1$. It is suggested that all the stellar structures under examination are advantageously independent of any central singularity and are stable. Comprehensive graphical analysis shows that various physical features which are crucially important for the emergence of the stellar structures are conferred.
Longitudinal dynamics from hydrodynamics with an order parameter
Shu Lin, Gezheng Zhou
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Abstract:
We studied coupled dynamics of hydrodynamic fields and order parameter in the presence of nontrivial longitudinal flow using the chiral fluid dynamics model. We found that longitudinal expansion provides an effective relaxation for the order parameter, which equilibrates in an oscillatory fashion. Similar oscillations are also visible in hydrodynamic degrees of freedom through coupled dynamics. The oscillations are reduced when dissipation is present. We also found that the quark density, which initially peaked at the boundary of the boost invariant region, evolves toward forward rapidity with the peak velocity correlated with the velocity of longitudinal expansion. The peak broadens during this evolution. The corresponding chemical potential rises due to simultaneous decrease of density and temperature. We compared the cases with and without dissipation for the order parameter and also the standard hydrodynamics without order parameter. We found that the corresponding effects on temperature and chemical potential can be understood from the conservation laws and different speeds of equilibration of the order parameter in the three cases.
Proton radioactivity half-lives with nuclear asymmetry factor
A. Soylu, F. Koyuncu, G. Gangopadhyay, V. Dehghani, S. A. Alavi
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The dependence of proton emission half-lives on the nuclear asymmetry parameter is investigated using the WKB method and two types of empirical formula. Using the single-folding formalism with asymmetry-dependent nuclear radius and surface diffuseness of nuclear matter, the nuclear potential and consequently the half-life are functions of the asymmetry factor. Despite small values of asymmetry in neutron-deficient proton emitters, noticeable changes in the half-lives are observed. The addition of an asymmetry parameter term to the two forms of empirical formulas leads to a reduction in the rms error for ground state and isomeric transitions. A noticeable reduction of about 43% is obtained for isomeric transitions in the second form of the empirical formula. Considering ground state transitions in two categories, odd-even and odd-odd emitters, and adopting deformation and asymmetry-dependent empirical formulas, the rms decreases remarkably. The lowest values of rms errors, viz. 0.1492, 0.2312, and 0.1999, are obtained for the aforementioned empirical formulas for ground state transitions of odd-even and odd-odd emitters and for all isomeric transitions, respectively.
Exotic ΩΩ dibaryon states in a molecular picture
Xiao-Hui Chen, Qi-Nan Wang, Wei Chen, Hua-Xing Chen
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We investigate the exotic $\Omega\Omega$ dibaryon states with $J^P=0^+$ and $2^+$ in a molecular picture. We construct a tensor $\Omega$$\Omega$ molecular interpolating current and calculate the two-point correlation function within the method of QCD sum rules. Our calculations indicate that the masses of the scalar and tensor dibaryon states are $m_{\Omega\Omega, \, 0^+} = $ $ (3.33\pm 0.51) \,{\rm{GeV}}$ and $m_{\Omega\Omega,\, 2^+}=(3.15\pm0.33)\, {\rm{GeV}}$, respectively, which are below the $2m_\Omega$ threshold. Within error, these results do not negate the existence of loosely bound molecular $\Omega\Omega$ dibaryon states. These exotic strangeness $S=-6$ and doubly-charged $\Omega\Omega$ dibaryons, if they exist, may be identified in heavy-ion collision processes in the future.
Probing tqZ anomalous couplings in the trilepton signal at the HL-LHC, HE-LHC, and FCC-hh
Yao-Bei Liu, Stefano Moretti
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We investigate the prospect of discovering the Flavour Changing Neutral Current (FCNC) $ tqZ $ couplings via two production processes yielding trilepton signals: top quark pair production $ pp\to t\bar{t} $ with one top quark decaying to the Z boson and one light jet and the anomalous single top quark plus Z boson production process $ pp\to tZ $. We study these channels at various successors of the Large Hadron Collider (LHC), i.e., the approved High-Luminosity LHC (HL-LHC) as well as the proposed High-Energy LHC (HE-LHC) and Future Circular Collider in hadron-hadron mode (FCC-hh). We perform a full simulation for the signals and the relevant Standard Model (SM) backgrounds and obtain limits on the Branching Ratios (BRs) of $ t\to qZ\; (q = u,c) $, eventually yielding a trilepton final state through the decay modes $ t\to b W^{+}\to b\ell^{+}\nu_{\ell} $ and $ Z\to \ell^{+}\ell^{-} $. The upper limits on these FCNC BRs at 95% Confidence Level (CL) are obtained at the HL-LHC with $ \sqrt s = 14 $ TeV and 3 ab−1, at the HE-LHC with $ \sqrt s = 27 $ TeV and 15 ab−1, and at the FCC-hh with $ \sqrt s = 100 $ TeV and 30 ab−1.
Diagonal reflection symmetries and universal four-zero texture
Masaki J. S. Yang
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In this paper, we consider a set of new symmetries in the SM: diagonal reflection symmetries $R \, m_{u,\nu}^{*} \, R = m_{u,\nu}, m_{d,e}^{*} = m_{d,e}$ with $R =$ diag $(-1,1,1)$. These generalized $CP$ symmetries predict the Majorana phases to be $\alpha_{2,3} /2 = 0$ or $\pi /2$. Realization of diagonal reflection symmetries implies a broken chiral $U(1)_{\rm{PQ}}$ symmetry only for the first generation. The axion scale is suggested to be $\langle {\theta_{u,d}} \rangle \sim \Lambda_{\rm{GUT}} \, \sqrt{m_{u,d} \, m_{c,s}} / v \sim 10^{12} $ [GeV]. By combining the symmetries with the four-zero texture, the mass eigenvalues and mixing matrices of quarks and leptons are reproduced well. This scheme predicts the normal hierarchy, the Dirac phase $\delta _{CP} \simeq 203^{\circ},$ and $|m_{1}| \simeq 2.5$ or $6.2 $ [meV]. In this scheme, the type-I seesaw mechanism and a given neutrino Yukawa matrix $Y_{\nu}$ completely determine the structure of the right-handed neutrino mass $M_{R}$. A $u-\nu$ unification predicts the mass eigenvalues to be $ (M_{R1} \, , M_{R2} \, , M_{R3}) = (O (10^{5}) \, , O (10^{9}) \, , O (10^{14})) $ [GeV].
Effect of momentum anisotropy on quark matter in the quark-meson model
He-Xia Zhang, Ben-Wei Zhang
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We investigate the chiral phase structure of quark matter with spheroidal momentum-space anisotropy specified by one anisotropy parameter $\xi$ in the 2+1 flavor quark-meson model. We find that the chiral phase diagram and the location of the critical endpoint (CEP) are significantly affected by the value of $\xi$. With an increase in $\xi$, the CEP is shifted to lower temperatures and higher quark chemical potentials. In addition, the temperature of the CEP is more sensitive to the anisotropy parameter than the corresponding quark chemical potential, which is the opposite to that from the finite system volume effect. The effects of the momentum anisotropy on the thermodynamic properties and scalar (pseudoscalar) meson masses are also studied at the vanishing quark chemical potential. The numerical results reveal that an increase in $\xi$ can hinder the restoration of chiral symmetry. We also find that shear viscosity and electrical conductivity decrease as $\xi$ increases. However, the bulk viscosity exhibits a significant non-trivial behavior with $\xi$ in the entire temperature domain of interest.
Geometrical reconstruction of fluorescence events observed by the LHAASO experiment
F. Aharonian, Q. An, Axikegu, L. X. Bai, Y. X. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, H. Cai, J. T. Cai, Z. Cao, J. Chang, J. F. Chang, X. C. Chang, B. M. Chen, J. Chen, L. Chen, M. J. Chen, M. L. Chen, Q. H. Chen, S. H. Chen, S. Z. Chen, T. L. Chen, X. L. Chen, Y. Chen, N. Cheng, Y. D. Cheng, S. W. Cui, X. H. Cui, Y. D. Cui, B. Z. Dai, H. L. Dai, Z. G. Dai, Danzengluobu, D. della Volpe, B. D'Ettorre Piazzoli, X. J. Dong, J. H. Fan, Y. Z. Fan, Z. X. Fan, J. Fang, K. Fang, C. F. Feng, L. Feng, S. H. Feng, Y. L. Feng, B. Gao, C. D. Gao, Q. Gao, W. Gao, M. M. Ge, L. S. Geng, G. H. Gong, Q. B. Gou, M. H. Gu, J. G. Guo, X. L. Guo, Y. Q. Guo, Y. Y. Guo, Y. A. Han, H. H. He, H. N. He, J. C. He, S. L. He, X. B. He, Y. He, M. Heller, Y. K. Hor, C. Hou, X. Hou, H. B. Hu, S. Hu, S. C. Hu, X. J. Hu, D. H. Huang, Q. L. Huang, W. H. Huang, X. T. Huang, Z. C. Huang, F. Ji, X. L. Ji, H. Y. Jia, K. Jiang, Z. J. Jiang, C. Jin, D. Kuleshov, K. Levochkin, B. B. Li, C. Li, F. Li, H. B. Li, H. C. Li, H. Y. Li, J. Li, K.
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The LHAASO-WFCTA experiment, which aims to observe cosmic rays in the sub-EeV range using the fluorescence technique, uses a new generation of high-performance telescopes. To ensure that the experiment has excellent detection capability associated with the measurement of the energy spectrum, the primary composition of cosmic rays, and so on, an accurate geometrical reconstruction of air-shower events is fundamental. This paper describes the development and testing of geometrical reconstruction for stereo viewed events using the WFCTA (Wide Field of view Cherenkov/Fluorescence Telescope Array) detectors. Two approaches, which take full advantage of the WFCTA detectors, are investigated. One is the stereo-angular method, which uses the pointing of triggered SiPMs in the shower trajectory, and the other is the stereo-timing method, which uses the triggering time of the fired SiPMs. The results show that both methods have good geometrical resolution; the resolution of the stereo-timing method is slightly better than the stereo-angular method because the resolution of the latter is slightly limited by the shower track length.
Measurements of dihadron correlations relative to the event plane in Au+Au collisions at ${\sqrt {{{ s}_{{\bf{NN}}}}}{\bf{ = 200}}}$ GeV
H. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, D. Arkhipkin, G. S. Averichev, J. Balewski, D. R. Beavis, N. K. Behera, R. Bellwied, M. J. Betancourt, R. R. Betts, A. Bhasin, A. K. Bhati, H. Bichsel, J. Bielcik, J. Bielcikova, B. Biritz, L. C. Bland, W. Borowski, J. Bouchet, E. Braidot, A. V. Brandin, A. Bridgeman, S. G. Brovko, E. Bruna, S. Bueltmann, I. Bunzarov, T. P. Burton, X. Z. Cai, H. Caines, M. Calderón de la Barca Sánchez, D. Cebra, R. Cendejas, M. C. Cervantes, Z. Chajecki, P. Chaloupka, S. Chattopadhyay, H. F. Chen, J. H. Chen, J. Y. Chen, L. Chen, J. Cheng, M. Cherney, A. Chikanian, K. E. Choi, W. Christie, P. Chung, M. J. M. Codrington, R. Corliss, J. G. Cramer, H. J. Crawford, S. Dash, A. Davila Leyva, L. C. De Silva, R. R. Debbe, T. G. Dedovich, A. A. Derevschikov, R. Derradi de Souza, L. Didenko, P. Djawotho, S. M. Dogra, X. Dong, J. L. Drachenberg, J. E. Draper, J. C. Dunlop, L. G. Efimov, M. Elnimr, J. Engelage, G. Eppl
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Dihadron azimuthal correlations containing a high transverse momentum ($ p_{T} $) trigger particle are sensitive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the traversing parton and the medium, i.e. jet-quenching. Previous measurements revealed a strong modification to dihadron azimuthal correlations in Au+Au collisions with respect to p+p and d+Au collisions. The modification increases with the collision centrality, suggesting a path-length or energy density dependence to the jet-quenching effect. This paper reports STAR measurements of dihadron azimuthal correlations in mid-central (20%-60%) Au+Au collisions at $ \sqrt{s_{\rm{NN}}} = 200 $ GeV as a function of the trigger particle's azimuthal angle relative to the event plane, $ \phi_{s} = | \phi_{t}- \psi_{{\rm{EP}}}| $. The azimuthal correlation is studied as a function of both the trigger and associated particle $ p_{T} $. The subtractions of the combinatorial background and anisotropic flow, assuming Zero Yield At Minimum (ZYAM), are described. The correlation results are first discussed with subtraction of the even harmonic (elliptic and quadrangular) flow backgrounds. The away-side correlation is strongly modified, and the modification varies with $ \phi_{s} $, with a double-peak structure for out-of-plane trigger particles. The near-side ridge (long range pseudo-rapidity $ \Delta\eta $ correlation) appears to drop with increasing $ \phi_{s} $ while the jet-like component remains approximately constant. The correlation functions are further studied with the subtraction of odd harmonic triangular flow background arising from fluctuations. It is found that the triangular flow, while responsible for the majority of the amplitudes, is not sufficient to explain the $ \phi_{s} $-dependence of the ridge or the away-side double-peak structure. The dropping ridge with $ \phi_{s} $ could be attributed to a $ \phi_{s} $-dependent elliptic anisotropy; however, the physics mechanism of the ridge remains an open question. Even with a $ \phi_{s} $-dependent elliptic flow, the away-side correlation structure is robust. These results, with extensive systematic studies of the dihadron correlations as a function of $ \phi_{s} $, trigger and associated particle $ p_{T} $, and the pseudo-rapidity range $ \Delta\eta $, should provide stringent inputs to help understand the underlying physics mechanisms of jet-medium interactions in high energy nuclear collisions.
Production of hidden-charm and hidden-bottom pentaquark states in electron-proton collisions
Ya-Ping Xie, Xu Cao, Yu-Tie Liang, Xurong Chen
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Electro-production of several pentaquark states is investigated in this study. The eSTARlight package is adapted to study the electro-production of $J/\psi$ and $\Upsilon (1S)$ via pentaquark $P_c$ and $P_b$ resonance channels in $e p \to e J/\psi p$ and $e p \to \Upsilon(1S) p$ scattering processes at the proposed electron-ion colliders (EICs). The results obtained in this study are compared to those of non-resonance t-channels, which are described in the pomeron exchange model developed in our studies. Some pseudo-rapidity and rapidity distributions of $J/\psi$ and $\Upsilon(1S)$ are presented for the proposed EICs, including EicC and EIC-US. It is found that EicC is a good platform to identify $P_b$ states in the future.
Nucleon stripping in deuteron-induced spallation reactions at hundreds MeV/nucleon
Qu-Fei Song, Su-Yang Xu, Jun Su
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Abstract:
A nucleon-nucleus dynamics model was developed to investigate the proton-, neutron-, and deuteron-induced reactions at hundreds of MeV/nucleon. In this model, the trajectory of incident nucleon is described by classical mechanics, and the probability of reaction between the nucleon and nucleus is calculated by exponential damping. It is shown that the total reaction cross sections calculated by the model agree in general with the predictions by the CDCC and the experimental data. The model was applied to investigate the nucleon stripping in deuteron-induced reactions and its symmetry energy dependence.
Double-heavy tetraquark states with heavy diquark-antiquark symmetry
Jian-Bo Cheng, Shi-Yuan Li, Yan-Rui Liu, Zong-Guo Si, Tao Yao
Published:
Abstract:
We calculate the masses of the $QQ\bar{q}\bar{q}$ ($Q=c,b$; $q=u,d,s$) tetraquark states with the aid of heavy diquark-antiquark symmetry (HDAS) and the chromomagnetic interaction (CMI) model. The masses of the highest-spin ($J=2$) tetraquarks that have only the $(QQ)_{\bar{3}_c}(\bar{q}\bar{q})_{3_c}$color structure are related with those of conventional hadrons using HDAS. Thereafter, the masses of their partner states are determined with the mass splittings in the CMI model. Our numerical results reveal that (i) the lightest $cc\bar{n}\bar{n}$ ($n=u,d$) is an $I(J^P)=0(1^+)$ state around 3929 MeV (53 MeV above the $DD^*$ threshold), and none of the double-charm tetraquarks are stable; (ii) the stable double-bottom tetraquarks are the lowest $0(1^+)$ $bb\bar{n}\bar{n}$ around 10488 MeV ($\approx116$ MeV below the $\bar{B}\bar{B}^*$ threshold) and the lowest $1/2(1^+)$ $bb\bar{n}\bar{s}$ around 10671 MeV ($\approx20$ MeV below the $\bar{B}\bar{B}_s^*/\bar{B}_s\bar{B}^*$ threshold); and (iii) the two lowest $bc\bar{n}\bar{n}$ tetraquarks, namely the lowest $0(0^+)$ around 7167 MeV and the lowest $0(1^+)$ around 7223 MeV, are in the near-threshold states. Moreover, we discuss the constraints on the masses of double-heavy hadrons. Specifically, for the lowest nonstrange tetraquarks, we obtain $T_{cc} < 3965$ MeV, $T_{bb} < 10627$ MeV, and $T_{bc} < 7199$ MeV.
Bubble dynamics in a strong first-order quark-hadron transition
Shuying Zhou, Song Shu, Hong Mao
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Abstract:
We investigate the dynamics of a strong first-order quark-hadron transition driven by cubic interactions via homogeneous bubble nucleation in the Friedberg-Lee model. The one-loop effective thermodynamic potential of the model and the critical bubble profiles have been calculated at different temperatures and chemical potentials. By taking the temperature and the chemical potential as variables, the evolutions of the surface tension, the typical radius of the critical bubble, and the shift in the coarse-grained free energy in the presence of a nucleation bubble are obtained, and the limit on the reliability of the thin-wall approximation is also addressed accordingly. Our results are compared to those obtained for a weak first-order quark-hadron phase transition; in particular, the spinodal decomposition is relevant.
A transient process observation method based on the non-homogeneous Poisson process model
Kuo Zhao, Xiao-Ping Ouyang, Hui-Ping Guo, Liang Chen, Lei-Dang Zhou, Jin-Lu Ruan, Han Wang, Ning Lv, Run-Long Gao
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Abstract:
The current-mode-counting method is a new approach to observing transient processes, especially in transient nuclear fusion, based on the non-homogeneous Poisson process (NHPP) model. In this paper, a new measurement process model of the pulsed radiation field produced by transient nuclear fusion is built based on the NHPP. A simulated measurement is performed using the model, and the current signal from the detector is obtained by simulation based on Poisson process thinning. The neutron time spectrum is reconstructed and is in good agreement with the theoretical value, with its maximum error of a characteristic parameter less than 2.3%. Verification experiments were carried out on a CPNG-6 device at the China Institute of Atomic Energy, with a detection system with a nanosecond response time. The experimental charge amplitude spectra are in good agreement with those obtained by the traditional counting mode, and the characteristic parameters of the time spectrum are in good agreement with the theoretical values. This shows that the current-mode-counting method is effective for the observation of transient nuclear fusion processes.
Search for the rare decay B0J/ψϕ
R. Aaij, C. Abellán Beteta, T. Ackernley, B. Adeva, M. Adinolfi, H. Afsharnia, C.A. Aidala, S. Aiola, Z. Ajaltouni, S. Akar, J. Albrecht, F. Alessio, M. Alexander, A. Alfonso Albero, Z. Aliouche, G. Alkhazov, P. Alvarez Cartelle, S. Amato, Y. Amhis, L. An, L. Anderlini, A. Andreianov, M. Andreotti, F. Archilli, A. Artamonov, M. Artuso, K. Arzymatov, E. Aslanides, M. Atzeni, B. Audurier, S. Bachmann, M. Bachmayer, J.J. Back, S. Baker, P. Baladron Rodriguez, V. Balagura, W. Baldini, J. Baptista Leite, R.J. Barlow, S. Barsuk, W. Barter, M. Bartolini, F. Baryshnikov, J.M. Basels, G. Bassi, B. Batsukh, A. Battig, A. Bay, M. Becker, F. Bedeschi, I. Bediaga, A. Beiter, V. Belavin, S. Belin, V. Bellee, K. Belous, I. Belov, I. Belyaev, G. Bencivenni, E. Ben-Haim, A. Berezhnoy, R. Bernet, D. Berninghoff, H.C. Bernstein, C. Bertella, E. Bertholet, A. Bertolin, C. Betancourt, F. Betti, M.O. Bettler, Ia. Bezshyiko, S. Bhasin, J. Bhom, L. Bian, M.S. Bieker, S. Bifani, P. Billoir, M. Birch, F.C.R. Bishop, A. Bizzeti, M. Bj
Published:
Abstract:
A search for the rare decay $ B^0\to J/ \psi\phi$ is performed using $ pp$ collision data collected with the LHCb dete-ctor at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. No significant signal of the decay is observed and an upper limit of $ 1.1 \times 10^{-7}$ at 90% confidence level is set on the branching fraction.
Isovector giant dipole resonances in proton-rich Ar and Ca isotopes
Ling Liu, Shuai Liu, Shi-Sheng Zhang, Li-Gang Cao
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Abstract:
The isovector giant dipole resonances (IVGDR) in proton-rich Ar and Ca isotopes have been systematically investigated using the resonant continuum Hartree-Fock+BCS (HF+BCS) and quasiparticle random phase approximation (QRPA) methods. The Skyrme SLy5 and density-dependent contact pairing interactions are employed in the calculations. In addition to the giant dipole resonances at energy around 18 MeV, pygmy dipole resonances (PDR) are found to be located in the energy region below 12 MeV. The calculated energy-weighted moments of PDR in nuclei close to the proton drip-line exhaust about 4% of the TRK sum rule. The strengths decrease with increasing mass number in each isotopic chain. The transition densities of the PDR states show that motions of protons and neutrons are in phase in the interiors of nuclei, while the protons give the main contribution at the surface. By analyzing the QRPA amplitudes of proton and neutron 2-quasiparticle configurations for a given low-lying state, we find that only a few proton configurations give significant contributions. They contribute about 95% to the total QRPA amplitudes, which indicates that the collectivity of PDR states is not strong in proton-rich nuclei in the present study.
Fine structure of α decay in 222Pa
Wei Hua, Zhiyuan Zhang, Long Ma, Zaiguo Gan, Huabin Yang, Cenxi Yuan, Minghui Huang, Chunli Yang, Mingming Zhang, Yulin Tian, Xiaohong Zhou
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Abstract:
With the help of the gas-filled recoil spectrometer SHANS and a digital data acquisition system, the fine structure of the $\alpha$ decay for $^{222}$Pa was studied. The nuclides were produced through the 1p3n evaporation channel via the heavy-ion induced fusion evaporation reaction $^{40}$Ar + $^{186}$W. Based on the ER-$\alpha 1$-$\alpha 2$-$\alpha 3$ and $\alpha$-$\gamma$ correlation measurement, three new $\alpha$ decays were observed in addition to the three branches known previously. The one with the largest $\alpha$ decay energy was regarded as the ground state to ground state transition. The newly measured $\alpha$ decay properties of $^{222}$Pa were examined in a framework of reduced width.
Exploring the uncertainties in theoretical predictions of nuclear β-decay half-lives
M. Shi, J. Y. Fang, Z. M. Niu
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Abstract:
Nuclear $ \beta $-decay half-lives are predicted based on an empirical formula and the mass predictions from various nuclear models. It is found that the empirical formula can reproduce the nuclear $ \beta $-decay half-lives well, especially for short-lived nuclei with $ T_{1/2}< 1 $ s. The theoretical half-life uncertainties from $ \beta $-decay energies and the parameters of the empirical formula are further investigated. It is found that the uncertainties of the half-lives are relatively large for heavy nuclei and nuclei near the neutron-drip line. For nuclei on the r-process path, the uncertainties for those with $ N = 126 $ are about one order of magnitude, which are much larger than the uncertainties for those with $ N = 50 $ and $ 82 $. However, theoretical uncertainties from the parameters of the empirical formula are relatively small for the nuclei on the r-process path, which indicates that the empirical formula is very suitable for predicting the $ \beta $-decay half-lives in r-process simulations.
Systematic study of the Woods-Saxon potential parametersbetween heavy-ions
Lin Gan, Zhi-Hong Li, Hui-Bin Sun, Shi-Peng Hu, Er-Tao Li, Jian Zhong
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Abstract:
Experimental elastic scattering angular distributions of 11B, 12C, and 16O + heavy-ions are used to study the Woods-Saxon potential parameters. Best fitted values of the diffuseness parameters are found for each system, and a linear relationship is expressed between the diffuseness parameters and $A_1^{1/3}+A_2^{1/3}$ . The correlation of the potential depth and radius parameters with $A_1^{1/3}+A_2^{1/3}$ is also revealed within the limitations of the diffuseness parameter formula. Because the incident energies of most of the analyzed reactions are below or around the Coulomb barrier, the energy dispersion relation between the real and imaginary potentials is considered in order to investigate the ratio between the imaginary and real potential well depths, resulting in an expression of $W/V$ . Within the limitation of the volume integrals calculated with the S$\tilde{a}$o Paulo potential, parameterized formulas for the depth and radius parameters are obtained. The systematic Woods-Saxon potential parameters derived in the present work can reproduce not only the experimental data of elastic scattering angular distributions induced by 11B, 12C, and 16O but also some elastic scattering induced by other heavy-ions.
Analytic continuation and reciprocity relation for collinear splitting in QCD
Hao Chen, Tong-Zhi Yang, Hua Xing Zhu, Yu Jiao Zhu
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Abstract:
It is well-known that direct analytic continuation of the DGLAP evolution kernel (splitting functions) from space-like to time-like kinematics breaks down at three loops. We identify the origin of this breakdown as due to splitting functions not being analytic functions of external momenta. However, splitting functions can be constructed from the squares of (generalized) splitting amplitudes. We establish the rules of analytic continuation for splitting amplitudes, and use them to determine the analytic continuation of certain holomorphic and anti-holomorphic part of splitting functions and transverse-momentum dependent distributions. In this way we derive the time-like splitting functions at three loops without ambiguity. We also propose a reciprocity relation for singlet splitting functions, and provide non-trivial evidence that it holds in QCD at least through three loops.
Search for electron-antineutrinos associated with gravitational-wave events GW150914, GW151012, GW151226, GW170104, GW170608, GW170814, and GW170817 at Daya Bay
F. P. An, A. B. Balantekin, H. R. Band, M. Bishai, S. Blyth, G. F. Cao, J. Cao, J. F. Chang, Y. Chang, H. S. Chen, S. M. Chen, Y. Chen, Y. X. Chen, J. Cheng, Z. K. Cheng, J. J. Cherwinka, M. C. Chu, J. P. Cummings, O. Dalager, F. S. Deng, Y. Y. Ding, M. V. Diwan, T. Dohnal, J. Dove, M. Dvořák, D. A. Dwyer, J. P. Gallo, M. Gonchar, G. H. Gong, H. Gong, W. Q. Gu, J. Y. Guo, L. Guo, X. H. Guo, Y. H. Guo, Z. Guo, R. W. Hackenburg, S. Hans, M. He, K. M. Heeger, Y. K. Heng, A. Higuera, Y. K. Hor, Y. B. Hsiung, B. Z. Hu, J. R. Hu, T. Hu, Z. J. Hu, H. X. Huang, X. T. Huang, Y. B. Huang, P. Huber, D. E. Jaffe, K. L. Jen, X. L. Ji, X. P. Ji, R. A. Johnson, D. Jones, L. Kang, S. H. Kettell, S. Kohn, M. Kramer, T. J. Langford, J. Lee, J. H. C. Lee, R. T. Lei, R. Leitner, J. K. C. Leung, F. Li, J. J. Li, Q. J. Li, S. Li, S. C. Li, W. D. Li, X. N. Li, X. Q. Li, Y. F. Li, Z. B. Li, H. Liang, C. J. Lin, G. L. Lin, S. Lin, J. J. Ling, J. M. Link, L. Littenberg, B. R. Littlejohn, J. C. Liu, J. L. Liu, C. Lu, H. Q. Lu, J. S.
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Abstract:
The establishment of a possible connection between neutrino emission and gravitational-wave (GW) bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge. In the Daya Bay experiment, using the data collected from December 2011 to August 2017, a search was performed for electron-antineutrino signals that coincided with detected GW events, including GW150914, GW151012, GW151226, GW170104, GW170608, GW170814, and GW170817. We used three time windows of ±10, ±500, and ±1000 s relative to the occurrence of the GW events and a neutrino energy range of 1.8 to 100 MeV to search for correlated neutrino candidates. The detected electron-antineutrino candidates were consistent with the expected background rates for all the three time windows. Assuming monochromatic spectra, we found upper limits (90% confidence level) of the electron-antineutrino fluence of (1.13 − 2.44)×1011 cm−2 at 5 MeV to 8.0×107 cm−2 at 100 MeV for the three time windows. Under the assumption of a Fermi-Dirac spectrum, the upper limits were found to be (5.4 − 7.0)×109 cm−2 for the three time windows.
Pattern for flavor-dependent quark-antiquark interaction
Muyang Chen, Lei Chang
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Abstract:
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.
LETTER
Origin of hardening in spectra of cosmic ray nuclei at a few hundred GeV using AMS-02 data
Jia-Shu Niu
Published: , doi: 10.1088/1674-1137/abe03d
Abstract:
Many experiments have confirmed spectral hardening at a few hundred GeV in the spectra of cosmic ray (CR) nuclei. Three different origins have been proposed: primary source acceleration, propagation, and the superposition of different kinds of sources. In this work, a broken power law has been employed to fit each of the spectra of cosmic ray nuclei from AMS-02 directly, for rigidities greater than 45 GeV. The fitting results of the break rigidity and the spectral index differences less than and greater than the break rigidity show complicated relationships among different nuclear species, which cannot be reproduced naturally by a simple primary source scenario or a propagation scenario. However, with a natural and simple assumption, the superposition of different kinds of sources could have the potential to explain the fitting results successfully. Spectra of CR nuclei from a single future experiment, such as DAMPE, will provide us the opportunity to do cross checks and reveal the properties of the different kinds of sources.