Nuclear Theory·nucl-th

Tuesday·October 15, 2019

22 papers—13 primary·9 cross-listed

14
Inhomogeneous chiral condensates in three-flavor quark matter
Stefano Carignano🇪🇸 · Michael Buballa🇩🇪
We investigate the effect of strange quark degrees of freedom on the formation of inhomogeneous chiral condensates in a three-flavor Nambu--Jona-Lasinio model in mean-field approximation. A Ginzburg-Landau study complemented by a stability analysis allow us to determine in a general way the location of the critical and Lifshitz points, together with the phase boundary where the (partially) chirally restored phase becomes unstable against developing inhomogeneities, without resorting to specific assumptions on the shape of the chiral condensate. We discuss the resulting phase structure and study the influence of the bare strange-quark mass $m_{s}$ and the axial anomaly on the size and location of the inhomogeneous phase compared to the first-order transition associated with homogeneous matter. We find that, as a consequence of the axial anomaly, critical and Lifshitz point split. For realistic strange-quark masses the effect is however very small and becomes sizeable only for small values of $m_{s}$ .
↳ hep-phnucl-thPRD(2020)·40 citations
15
Large Sound Speed in Dense Matter and the Deformability of Neutron Stars
Brendan Reed🇺🇸 · C. J. Horowitz🇺🇸
The historic first detection of the binary neutron star merger GW170817 by the LIGO-Virgo collaboration has set a limit on the gravitational deformability of neutron stars. In contrast, radio observations of PSR J0740+6620 find a very massive neutron star. Tension between the small deformability and the large maximum mass may suggest that the pressure rises rapidly with density and thus the speed of sound in dense matter is likely a large fraction of the speed of light. We use these observations and simple constant sound-speed model equations of state to set a lower bound on the maximum speed of sound in neutron stars. If the tidal deformability of a 1.4 $M_{⊙}$ neutron star is less than 600, as is suggested by subsequent analyses of GW170817, we find that the sound speed in the cores of neutron stars is likely larger than the conformal limit of $c / 3$ . Implications of this for our understanding of both hadronic and quark-gluon descriptions of dense matter are discussed.
↳ astro-ph.HEgr-qcnucl-thPRC(2020)·66 citations
16
New Insight about the Effective Restoration of U_A(1) Symmetry
Xiang Li🇨🇳 · Wei-jie Fu🇨🇳 · Yu-xin Liu🇨🇳
The effective restoration of the U_{A}(1) symmetry is revisited by implementing the functional renormalization group approach combining with the 2+1 flavor Polyakov-loop quark-meson model. A temperature-dependent 't Hooft term is taken to imitate the restoration of the U_{A}(1) symmetry. Order parameters, meson spectrum and mixing angles, especially the pressure and the entropy density of the system are calculated to explore the effects of different U_{A}(1) symmetry restoration patterns. We show then that the temperature for the restoration of the U_{A}(1) symmetry is much higher than that for the chiral symmetry SU_{A}(3).
↳ hep-phnucl-thPRD(2020)·10 citations
17
Precision Measurements of Fundamental Interactions with (Anti)Neutrinos
R. Petti🇺🇸
We discuss the main limitations of past neutrino scattering experiments and possible ways to address them in a next-generation program of precision measurements of fundamental interactions with (anti)neutrinos. A reduction of the longstanding precision gap with respect to electron scattering experiments could provide interesting synergies with the existing efforts in the fixed-target, collider, and nuclear physics communities.
↳ hep-exhep-phnucl-exnucl-th13 citations
18
Mass structure and pressure forces inside the nucleon
Cédric Lorcé (Ecole Polytechnique and CNRS)🇫🇷
We summarize recent works on the question of the nucleon mass decomposition and the 2D relativistic distribution of pressure forces on the light front. All these mechanical properties are encoded in the energy-momentum tensor of the system which can be constrained using various types of high-energy lepton-nucleon scatterings. Some further developments for targets with spin $> 1/2$ are also reported.
↳ hep-phnucl-th1 citation
19
Strong decays of the higher excited $Λ_{Q}$ and $Σ_{Q}$ baryons
Qi-Fang Lü🇨🇳 · Xian-Hui Zhong🇨🇳
In this work, we preform a systematic study of the strong decays for the higher singly heavy baryon resonances $Λ_{Q} (3 S)$ , $Λ_{Q} (2 P)$ , $Λ_{Q} (2 D)$ , $Λ_{Q} (1 F)$ , $Σ_{Q} (3 S)$ , $Σ_{Q} (2 P)$ , $Σ_{Q} (2 D)$ , and $Σ_{Q} (1 F)$ within the $^{3} P_{0}$ model. Our results show that most of the $λ -$ mode higher excited $Λ_{Q}$ and $Σ_{Q}$ states have a relatively narrow width, and mainly decay into two-body final states with one heavy meson plus one light baryon. Our calculations provide abundant theoretical information and demonstrate the general feature for these higher states, which may be valuable for future experimental searches and establishing the singly heavy baryon spectrum.
↳ hep-phhep-exnucl-thPRD(2020)·36 citations
20
Two-Photon-Exchange effects in $e p \to e n π^{+}$ and their corrections to separated cross sections $σ_{L,T,LT,TT}$ at small $- t$
Hui-Yun Cao🇨🇳 · Hai-Qing Zhou🇨🇳
In this work, the two-photon-exchange (TPE) effects in $e p \to e n π^{+}$ at small $- t$ are discussed within a hadronic model. Under the pion dominance approximation the TPE contribution to the amplitude can be described by a scalar function in the limit $m_{e} \to 0$ . The TPE contributions to the amplitude and the unpolarized differential cross section are both estimated when only the elastic intermediate state is considered. We find that the TPE corrections to the unpolarized differential cross section are about from $- 4%$ to $- 20%$ at $Q^{2} = 1$ -- $1.6$ GeV $^{2}$ . After considering the TPE corrections to the experimental data sets of unpolarized differential cross section, we analyze the TPE corrections to the separated cross sections $σ_{L,T,LT,TT}$ . We find that the TPE corrections (at $Q^{2} = 1$ -- $1.6$ GeV $^{2}$ ) to $σ_{L}$ are about from $- 10%$ to $- 30%$ , to $σ_{T}$ are about $20%$ , and to $σ_{LT,TT}$ are much larger. By these analysis, we conclude that the TPE contributions in $e p \to e n π^{+}$ at small $- t$ are important to extract the separated cross sections $σ_{L,T,LT,TT}$ and the electromagnetic magnetic form factor of $π^{+}$ in the experimental analysis.
↳ hep-phnucl-exnucl-thPRC(2020)·5 citations
21
Different space-time freeze-out picture -- an explanation of different $Λ$ and $Λ ˉ$ polarization?
O. Vitiuk🇳🇴 · L. Bravina🇳🇴 · E. Zabrodin🇳🇴
Thermal vorticity in non-central Au+Au collisions at energies $7.7 \leq s \leq 62.4$ GeV is calculated within the UrQMD transport model. Tracing the $Λ$ and $Λ ˉ$ hyperons back to their last interaction point we were able to obtain the temperature and the chemical potentials at the time of emission by fitting the extracted bulk characteristics of hot and dense medium to statistical model of ideal hadron gas. Then the polarization of both hyperons was calculated. The polarization of $Λ$ and $Λ ˉ$ increases with decreasing energy of nuclear collisions. The stronger polarization of $Λ ˉ$ is explained by the different space-time distributions of $Λ$ and $Λ ˉ$ and by different freeze-out conditions of both hyperons.
↳ hep-phnucl-exnucl-thPLB(2020)·81 citations
22
Quantum Tomography Measures Entanglement in Collider Reactions
John C. Martens🇺🇸 · John P. Ralston🇺🇸 · Daniel Tapia Takaki🇺🇸
Entanglement in high energy and and nuclear reactions is receiving great attention. A proper description of these reactions uses density matrices, and the express of entanglement in terms of {\it separability}. Quantum tomography bypasses field-theoretic formalism to determine density matrices in terms of experimental observables. We review recent work applying quantum tomography to practical experimental data analysis. We discuss the relation between separability, as defined in quantum information science, and factorization, as defined in high energy physics. When factorization applies, it comes from using separable probes, which tomographically determine separable projections of entangled density matrices.
↳ hep-phnucl-thquant-ph1 citation

Affiliations

first authorsco-authorsvia INSPIRE