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Different production sources of light nuclei inultra-relativistic heavy-ion collisions
Rui-Qin Wang, Jun Song, Gang Li, Feng-Lan Shao
Published: , doi: 10.1088/1674-1137/43/2/024101
Abstract:
We systematically study different production sources of light nuclei in ultra-relativistic heavy-ion collisions with a new method, an exclusive quark combination model + an inclusive hadron recombination model. We take deuterons and 3He produced in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV as examples to show the contribution of different production sources by studying their rapidity densities ${\rm d}N/{\rm d}y$ , yield ratios and transverse momentum ( $p_T$ ) spectra just after hadronization and at the final kinetic freeze-out. We find that about a half of $d$ and a fourth of 3He created just after hadronization can survive after the hadronic evolution process. Nucleons from $\Delta$ resonance decays make a much larger contribution to the regeneration of light nuclei at the hadronic phase stage, and this contribution is about 77% and 90% for $d$ and 3He, respectively, calculated at the final kinetic freeze-out. In addition, we give an explanation for the constant behaviors of yield ratios $d/p$ and 3He $/p$ as a function of the averaged charged multiplicity in Pb-Pb collisions and also provide a possible explanation for the observation that $d/p$ in Pb-Pb collisions is larger by a factor of about two than in pp collisions at LHC energies.
Study of the Standard Model and Majorana neutrino contributions to ${ B}^{{ +}} { \to} { K}^{{ (*){ \pm}}}{ \mu}^{ +}{ \mu}^{{ \mp}}$
Hong-Lei Li, Peng-Cheng Lu, Cong-Feng Qiao, Zong-Guo Si, Ying Wang
Published: , doi: 10.1088/1674-1137/43/2/023101
Abstract:
Lepton number violation processes can be induced by the Majorana neutrino exchange, which provide evidence for the Majorana nature of neutrinos. In addition to the natural explanation of the small neutrino masses, Type-I seesaw mechanism predicts the existence of Majorana neutrinos. The aim of this work is to study the B meson rare decays $B^{+} \to K^{(*)+}\mu^+\mu^-$ in the Standard Model and its extensions, and then to investigate the same-sign decay process $B^{+}\to K^{(*)-}\mu^{+}\mu^+$ . The corresponding dilepton invariant mass distributions are calculated. It is found that the dilepton angular distributions could shed light on the properties of new interactions induced by Majorana neutrinos.
PARTICLES AND FIELDS
Entanglement in simple spin networks with a boundary
Yi Ling;Meng-He Wu;Yikang Xiao
Published:
Abstract:
We investigate the bipartite entanglement for the boundary states in a simple type of spin networks with dangling edges, in which the two complementary parts are linked by two or more edges. Firstly, the spin entanglement is considered in the absence of the intertwiner entanglement. By virtue of numerical simulations, we find that the entanglement entropy usually depends on the group elements. More importantly, when the intertwiner entanglement is taken into account, we find that it is in general impossible to separate the total entanglement entropy into the contribution from spins on edges and the contribution from intertwiners at vertices. These situations are in contrast to the case when the two vertices are linked by a single edge.
A discussion on vacuum polarization correction to the cross-section of ${e^+e^-\to\gamma^\ast/\psi\to\mu^+\mu^-}$
Hong-Dou Jin;Li-Peng Zhou;Bing-Xin Zhang;Hai-Ming Hu
Published:
Abstract:
Vacuum polarization is a part of the initial-state radiative correction for the cross-section of $e^+e^-$ annihilation processes. In the energy region in the vicinity of narrow resonances $J/\psi$ and $\psi(3686)$, the vacuum polarization contribution from the resonant component has a significant effect on the line-shape of the lepton pair production cross-section. This paper discusses some basic concepts and describes an analytical calculation of the cross-section of $e^+e^-\to\gamma^\ast/\psi\to\mu^+\mu^-$ considering the single and double vacuum polarization effect of the virtual photon propagator. Moreover, it presents some numerical comparisons with the traditional treatments.
Doubly-charged scalar in four-body decays of neutral flavored mesons
Tian-Hong Wang;Geng Li;Yue Jiang;Guo-Li Wang
Published:
Abstract:
We study the four-body decays of neutral flavored mesons, including $\bar K^0$, $D^0$, $\bar B^0$, and $\bar B_s^0$. These processes, which could be induced by a hypothetical doubly-charged scalar particle, do not conserve the lepton number. Assuming, as an example, that the mass of the doubly-charged particle is 1000 GeV, and using the upper bounds of the couplings, we calculate the branching ratios of different channels. For $\bar K^0\rightarrow h_1^+h_2^+e^-e^-$, $D^0\rightarrow h_1^-h_2^-e^+e^+$, and $\bar B_{d,s}^0\rightarrow h_1^+h_2^+e^-e^-$, it is of the order of $10^{-30}$, $10^{-32}$--$10^{-29}$, and $10^{-33}$--$10^{-28}$, respectively. Based on the experimental results for the $D^0\rightarrow h_1^-h_2^-l_1^+l_2^+$ channels, we also find the upper limit for the quantity $\frac{s_\Delta h_{ij}}{M_\Delta^2}$.
Probing  anomalous top-Higgs couplings at the HL-LHC via ${H\to WW^{\ast}}$ decay channels
Yao-Bei Liu;Stefano Moretti
Published:
Abstract:
We study the prospects of probing the anomalous $tHq$~($q= u, c$) couplings via SS2L or 3L signatures at the High Luminosity (HL-LHC) run of the 14 TeV CERN collider. We focus on signals of the  $tH$ associated production followed by the decay modes $t\to b\ell^{+}\nu_{\ell}$ and $H\to WW^{\ast}$, and $t\bar{t}$ production followed by the decay modes $t\to b\ell^{+}\nu_{\ell}$ and $\bar{t}\to H(\to WW^{\ast})\bar{q}$, where $\ell=e, \mu$. Based on two types of  $H\to WW^{\ast}$ decay topologies, one assuming the semileptonic decay mode $H\to WW^{\ast}\to \ell^{+}\nu jj $ and the other the fully leptonic decay mode $H\to WW^{\ast}\to \ell^{+}\nu \ell^{-}\bar{\nu}$, we perform a full simulation for signals and backgrounds. It is shown that, at the future HL-LHC, the branching ratio $Br(t\to uh)~(Br(t\to ch))$ can be  probed to $1.17~(1.56)\times 10^{-3}$ for the same-sign di-lepton channel, and to $7.1~\times 10^{-4}~(1.39~\times 10^{-3})$ for the 3L channel at $3\sigma$ sensitivity.
Fermion bound states in geometrically deformed backgrounds
D. Bazeia;A. Mohammadi;D. C. Moreira
Published:
Abstract:
This work deals with the behavior of fermions in the background of kinklike structures in the two-dimensional spacetime. The kinklike structures appear from bosonic scalar field models that engender distinct profiles and interact with the fermion fields via the standard Yukawa coupling. We first consider two models that engender parity symmetry, one leading to the exclusion of fermion bound states, and the other to the inclusion of bound states, when the parameter that controls the bosonic structure varies from zero to unity. We then investigate a third model where the kinklike solution explicitly breaks parity symmetry, leading to fermion bound states that are spatially asymmetric.
A non-relativistic model for the ${[cc][\bar{c}\bar{c}]}$ tetraquark
V. R. Debastiani;F S. Navarra
Published:
Abstract:
We use a non-relativistic model to study the  spectroscopy of a tetraquark composed of $[cc][\bar{c}\bar{c}]$ in a diquark-antidiquark configuration. By numerically solving the Schr\"{o}dinger equation with a Cornell-inspired potential, we separate the four-body problem into three two-body problems. Spin-dependent terms (spin-spin, spin-orbit and tensor) are used to describe the splitting structure of the $c\bar{c}$ spectrum and are also extended to the interaction between diquarks. Recent experimental data on charmonium states are used to fix the parameters of the model and a satisfactory description of the spectrum is obtained. We find that the spin-dependent interaction is sizable in the diquark-antidiquark system, despite  the heavy diquark mass, and also that the diquark has a finite size if treated in the same way as the $c\bar{c}$ systems. We find that the lowest $S$-wave $T_{4c}$ tetraquarks might be below their thresholds of spontaneous dissociation into low-lying charmonium pairs, while orbital and radial excitations would be mostly above the corresponding charmonium pair thresholds. Finally,  we repeat the  alculations without the confining part of the potential and obtain bound diquarks and bound tetraquarks. This might be relevant to the study of  exotic charmonium in the quark-gluon plasma. The $T4c$ states could be investigated in the forthcoming experiments at the LHC and Belle II.
Mixed electroweak-QCD corrections to ${e^+e^-\to \mu^+\mu^- H}$ at CEPC with finite-width effect
Wen Chen;Feng Feng;Yu Jia;Wen-Long Sang
Published:
Abstract:
The associated production of Higgs boson with a muon pair, $e^+e^-\to \mu^+\mu^- H$, is one of the golden channels to pin down the properties of the Higgs boson in the prospective Higgs factories exemplified by {CEPC}. The projected accuracy of the corresponding cross section measurement is about per cent level at CEPC. In this work, we investigate both ${\mathcal O}(\alpha)$ weak correction and the ${\mathcal O}(\alpha\alpha_s)$ mixed electroweak-QCD corrections for this channel, appropriately taking into account the effect of finite $Z^0$ width. The $\mu^+\mu^-$ invariant mass spectrum is also predicted. The mixed electroweak-QCD correction turns out to reach 1.5\% of the Born-order result, and thereby must be included in future confrontation with the data. We also observe that, after including higher-order corrections, the simplified prediction for the integrated cross section employing the narrow-width-approximation may deviate from our full result by a few per cents.
NUCLEAR PHYSICS
Empirical pairing gaps and neutron-proton correlations
B. S. Ishkhanov;S. V. Sidorov;T. Yu. Tretyakova;E. V. Vladimirova
Published:
Abstract:
Analysis of various mass formulas related to neutron-proton correlations in atomic nuclei is carried out. Using the example of the $N = Z$ chain it is shown that for self-adjoint nuclei various formulas proposed in literature for estimating the $ np $ pairing energy lead to similar results. Significant differences between the calculation methods arise when  nuclei with $N \ne Z$ are considered, which allows to reveal the complexity of neutron-proton correlations in different types of atomic nuclei and to make assumptions on the correspondence of the mass relation to the real effect of $ np $ pairing. The Shell Model parametrization of the binding energy makes it possible to draw additional conclusions on the structure of mass formulas and their relationship.
Alternative methods for measurement of the global polarization of $\Lambda$ hyperons
Irfan Siddique;Zuo-tang Liang;Michael Annan Lisa;Qun Wang;Zhang-bu Xu
Published:
Abstract:
We propose alternative methods for measurement of the global polarization of $\Lambda$ hyperons. These methods involve event averages of proton and $\Lambda$ momenta in the laboratory frame. We carry out simulations using these methods and show that all of them work equally well in obtaining the global polarization of $\Lambda$ hyperons.
A simple description of the temperature dependence of the width of the fission-fragment mass yield in $\bf^{197}$Au and $\bf^{209}$Bi at intermediate energies
V. Yu. Denisov;O. A. Belyanovska;V. P. Khomenkov;I. Yu. Sedykh;K. M. Sukhyy
Published:
Abstract:
A simple approach is proposed to describe the experimental data for the widths of the fission-fragment mass yields in $^{197}$Au and $^{209}$Bi at low and intermediate energies. The approach is based on the expressions for the temperature dependence of the width of the fission-fragment mass yield and the mass of the most probable fragment. The expression for the width of the fission-fragment mass yield depends on the mass of the most probable fragment, the surface terms of the energy level density parameter, the temperature and the stiffness parameter of the potential related to mass-asymmetric degree of freedom. It is shown that the contribution of the surface term of the energy level density parameter is important for describing the experimental data in a wide range of energies.
Double heavy tri-hadron bound state via delocalized  $\pi$ bond
Li Ma;Qian Wang;Ulf-G. Mei{\ss}ner
Published:
Abstract:
The number of exotic candidates that are beyond the conventional quark model has increased dramatically over recent decades. Some of these can be viewed as analogues of the deuteron. Similarly, the existence of the triton indicates that bound states formed by three hadrons could also exist.  To illustrate this possibility, we study the $DD^*K$ and $BB^*\bar{K}$ systems using the Born-Oppenheimer approximation. To leading order, only one-pion exchange potentials are considered. This means that the three constituents share one virtual pion. This is similar to the role of the delocalized {\it $\pi$ bond} for the formation of benzene in chemistry.  After solving the Schr\"odinger equation, we find two three-body $DD^*K$ and $BB^*\bar{K}$ bound states with masses $4317.92_{-4.32}^{+3.66}~\mathrm{MeV}$ and $11013.65_{-8.84}^{+8.49}~\mathrm{MeV}$, respectively. The masses of their $D\bar{D}^*K$ and $B\bar{B}^*\bar{K}$ analogues are $4317.92_{-6.55}^{+6.13}~\mathrm{MeV}$ and $11013.65_{-9.02}^{+8.68}~\mathrm{MeV}$, respectively. From the experimental side, the $D\bar{D}^*K$ bound state could be found by analyzing the current world data on the $B\to J/\psi\pi\pi K$ process, by focusing on the $J/\psi \pi K$ channel.