Nuclear Theory·nucl-th

Thursday·December 27, 2018

22 papers—12 primary·10 cross-listed

13
Baryonic susceptibilities, quark-diquark models, and quark-hadron duality at finite temperature
E. Megias🇪🇸 · E. Ruiz Arriola🇪🇸 · L.L. Salcedo🇪🇸
Fluctuations of conserved charges such as baryon number, electric charge and strangeness may provide a test for completeness of states in lattice QCD for three light flavors. We elaborate on the idea that the corresponding susceptibilities can be saturated with excited baryonic states with an underlying quark-diquark structure with a linearly confining interaction. Using Polyakov-loop correlators we show that in the static limit, the quark-diquark potential coincides with the quark-antiquark potential in marked agreement with recent lattice studies. We thus study in a quark-diquark model the baryonic fluctuations of electric charge, baryon number and strangeness: $χ_{B Q}$ , $χ_{B B}$ and $χ_{B S}$ ; by considering a realization of the hadron resonance gas model in the light flavor sector of QCD. These results have been obtained by using the baryon spectrum computed within a relativistic quark-diquark model, leading to an overall good agreement with the spectrum obtained with other quark models and with lattice data for the fluctuations.
↳ hep-phhep-latnucl-thPRD(2019)·4 citations
14
Role of the spectator system in electromagnetic effects
K. Mazurek🇵🇱 · A. Rybicki🇵🇱 · A. Szczurek🇵🇱 · V. Ozvenchuk🇵🇱 · P.N. Nadtochy🇷🇺 · A. Kelic🇩🇪 · A. Marcinek🇵🇱
The electromagnetic effects on charged pion ( $π^{+}, π^{-}$ ) spectra provide new, independent information on the space-time evolution of the ultrarelativistic heavy ion collision. The spectator life time and its excitation energy may also be of importance for the understanding of the space-time evolution of the participant zone. This paper gives an overview of our coordinated effort to understand the interplay between electromagnetic phenomena and processes related to the fragmentation of the spectator system at forward rapidity in peripheral $P b$ + $P b$ collisions at top CERN SPS energies. Our study includes on one hand the experimental analysis of electromagnetic effects and corresponding phenomenological Monte Carlo simulations, and on the other hand dedicated theoretical calculations based on the Abrasion-Ablation model ABRABLA and the 4D Langevin approach.
↳ hep-phnucl-th0 citations
15
Tri-meson bound state $B B B^{*}$ via delocalized $π$ ~Bond
Li Ma🇩🇪 · Qian Wang🇩🇪 · Ulf-G. Meißner🇩🇪
During the last decades, numerous exotic states which cannot be explained by the conventional quark model have been observed in experiment. Some of them can be understood as two-body hadronic molecules, such as the famous $X (3872)$ , analogous to deuteron in nuclear physics. Along the same line, the existence of the triton leaves an open question whether there is a bound state formed by three hadrons. Since, for a given potential, a system with large reduced masses is more easier to form a bound state, we study the $B B B^{*}$ system with the one-pion exchange potential as an exploratory step by solving the three-body Schrödinger Equation. We predict that a tri-meson molecular state for the $B B B^{*}$ system is probably existent as long as the molecular states of its two-body subsystem $B B^{*}$ exist.
↳ hep-phnucl-thPRD(2019)·13 citations
16
Comparing treatments of weak reactions with nuclei in simulations of core-collapse supernovae
Hiroki Nagakura🇺🇸 · Shun Furusawa🇯🇵 · Hajime Togashi🇯🇵 · Sherwood Richers🇺🇸 · Kohsuke Sumiyoshi🇯🇵 · Shoichi Yamada🇯🇵
We perform an extensive study of the influence of nuclear weak interactions on core-collapse supernovae (CCSNe), paying particular attention to consistency between nuclear abundances in the equation of state (EOS) and nuclear weak interactions. We compute properties of uniform matter based on the variational method. For inhomogeneous nuclear matter, we take a full ensemble of nuclei into account with various finite-density and thermal effects and directly use the nuclear abundances to compute nuclear weak interaction rates. To quantify the impact of a consistent treatment of nuclear abundances on CCSN dynamics, we carry out spherically symmetric CCSN simulations with full Boltzmann neutrino transport, systematically changing the treatment of weak interactions, EOSs, and progenitor models. We find that the inconsistent treatment of nuclear abundances between the EOS and weak interaction rates weakens the EOS dependence of both the dynamics and neutrino signals. We also test the validity of two artificial prescriptions for weak interactions of light nuclei and find that both prescriptions affect the dynamics. Furthermore, there are differences in neutrino luminosities by ~10% and in average neutrino energies by 0.25-1 MeV from those of the fiducial model. We also find that the neutronization burst neutrino signal depends on the progenitor more strongly than on the EOS, preventing a detection of this signal from constraining the EOS.
↳ astro-ph.HEnucl-thAstrophys.J.Suppl.(2019)·52 citations
17
Possible bound states with hidden bottom from $K ˉ^{(*)} B^{(*)} B ˉ^{(*)}$ systems
Xiu-Lei Ren🇩🇪 · Zhi-Feng Sun🇨🇳
We study the three-body systems of $K ˉ^{(*)} B^{(*)} B ˉ^{(*)}$ by solving the Faddeev equations in the fixed-center approximation, where the light particle $K ˉ^{(*)}$ interacts with the heavy bound states of $B B ˉ$ ( $B^{*} B ˉ^{*}$ ) forming the clusters. In terms of the very attractive $K ˉ^{*} B$ and $K ˉ^{*} B^{*}$ subsystems, which are constrained by the observed $B_{s 1} (5830)$ and $B_{s 2}^{*} (5840)$ states in experiment, we find two deep bound states, containing the hidden-bottom components, with masses $11002 \pm 63$ MeV and $11078 \pm 57$ MeV in the $K ˉ^{*} B B ˉ$ and $K ˉ^{*} B^{*} B ˉ^{*}$ systems, respectively. The two corresponding states with higher masses of the above systems are also predicted. In addition, using the constrained two-body amplitudes of $K ˉ B^{(*)}$ and $K ˉ B ˉ^{(*)}$ via the hidden gauge symmetry in the heavy-quark sector, we also find two three-body $K ˉ B B ˉ$ and $K ˉ B^{*} B ˉ^{*}$ bound states.
↳ hep-phnucl-thPRD(2019)·13 citations
18
Chiral kinetic theory in curved spacetime
Yu-Chen Liu🇨🇳 · Lan-Lan Gao🇨🇳 · Kazuya Mameda🇨🇳 · Xu-Guang Huang🇨🇳
Many-body systems with chiral fermions exhibit anomalous transport phenomena originated from quantum anomalies. Based on quantum field theory, we derive the kinetic theory for chiral fermions interacting with an external electromagnetic field and a background curved geometry. The resultant framework respects the covariance under the U(1) gauge, local Lorentz, and diffeomorphic transformations. It is particularly useful to study the gravitational or non-inertial effects for chiral systems. As the first application, we study the chiral dynamics in a rotating coordinate and clarify the roles of the Coriolis force and spin-vorticity coupling in generating the chiral vortical effect (CVE). We also show that the CVE is an intrinsic phenomenon of a rotating chiral fluid, and thus independent of observer's frame.
↳ hep-thcond-mat.mes-hallgr-qcnucl-thPRD(2019)·107 citations
19
Spin Polarization and Chiral Condensation in 2+1 flavor Nambu-Jona-Lasinio model at finite temperature and baryon chemical potential
Aman Abhishek🇮🇳 · Arpan Das🇮🇳 · Hiranmaya Mishra🇮🇳 · Ranjita K. Mohapatra🇮🇳
We investigate the ferromagnetic (spin polarization) condensation in (2+1) flavor Nambu Jona-Lasinio(NJL) model with non-zero current quark masses at finite temperature and density which may be relevant in the context of neutron stars. The spin polarization condensation arises due to a tensor type interaction which may be generated due to non-perturbative effects in Quantum Chromodynamics(QCD). In this investigation we have shown the interplay between chiral condensate and spin polarization condensation for different values of tensor coupling. Spin polarization in the case of 2+1 flavor is different from two flavor case because of additional F $_{8}$ condensate associated with $λ_{8}^{f}$ flavor generator. We find a non-zero value of the two spin condensates in the chirally restored phase. Beyond a certain temperature the spin polarization condensates vanish for rather large quark chemical potentials. The spin condensates affect the chiral phase transition, quark masses, and the quark dispersion relation. The spin polarization condensate appears only in the chiral restored phase for light quarks. For large enough tensor couplings, it is observed that the spin polarization condensate acts as a catalyst for chiral symmetry restoration. Thermodynamic behavior of $F_{3}$ and $F_{8}$ are found to be different and they affect the quark masses differently.
↳ hep-phnucl-thPRD(2019)·3 citations
20
Ultrahigh-energy cosmic-ray nuclei and neutrinos from engine-driven supernovae
B. Theodore Zhang🇨🇳 · Kohta Murase🇺🇸
Transrelativistic supernovae (SNe), which are likely driven by central engines via jets or winds, have been among candidate sources of ultrahigh-energy cosmic rays (UHECRs). We investigate acceleration and survival of UHECR nuclei in the external reverse shock scenario. With composition models used in Zhang et al. (2018), we calculate spectra of escaping cosmic rays and secondary neutrinos. If their local rate is $\sim 1$ % of the core-collapse supernova rate, the observed UHECR spectrum and composition can be explained with the total cosmic-ray energy $E_{cr} \sim 1 0^{51}$ erg. The maximum energy of UHECR nuclei can reach $\sim 1 0^{20} - 10^{21} eV$ . The diffuse flux of source neutrinos is predicted to be $\sim 1 0^{- 11} - 1 0^{- 10} GeV cm^{- 2} s^{- 1} sr^{- 1}$ in the 0.1-1 EeV range, satisfying nucleus-survival bounds. The associated cosmogenic neutrino flux is calculated, and shown to be comparable or even higher than the source neutrino flux. These ultrahigh-energy neutrinos can be detected by ultimate detectors such as the Giant Radio Askaryan Neutrino Detector and Probe Of Extreme Multi-Messenger Astrophysics.
↳ astro-ph.HEastro-ph.SRhep-phnucl-thPRD(2019)·44 citations
21
Proton and neutron electromagnetic form factors from lattice QCD
C. Alexandrou (Univ. of Cyprus & The Cyprus Inst.)🇨🇾 · S. Bacchio (Univ. of Cyprus)🇨🇾 · M. Constantinou (Temple Univ.)🇺🇸 · J. Finkenrath (The Cyprus Inst.)🇨🇾 · K. Hadjiyiannakou (The Cyprus Inst.)🇨🇾 · K. Jansen (DESY-Zeuthen)🇩🇪 · G. Koutsou (The Cyprus Inst.)🇨🇾 · A. Vaquero Aviles Casco (Univ. of Utah)🇺🇸
The electromagnetic form factors of the proton and the neutron are computed within lattice QCD using simulations with quarks masses fixed to their physical values. Both connected and disconnected contributions are computed. We analyze two new ensembles of $N_{f} = 2$ and $N_{f} = 2 + 1 + 1$ twisted mass clover-improved fermions and determine the proton and neutron form factors, the electric and magnetic radii, and the magnetic moments. We use several values of the sink-source time separation in the range of 1.0 fm to 1.6 fm to ensure ground state identification. Disconnected contributions are calculated to an unprecedented accuracy at the physical point. Although they constitute a small correction, they are non-negligible and contribute up to 15% for the case of the neutron electric charge radius.
↳ hep-latnucl-exnucl-thPRD(2019)·130 citations
22
The Sea of Quarks and Antiquarks in the Nucleon: a Review
D. F. Geesaman🇺🇸 · P. E. Reimer🇺🇸
The quark and gluon structure of the proton has been under intense experimental and theoretical investigation for five decades. Even for the distributions of the well-studied valence quarks, challenges such as the value of the down quark to up quark ratio at high fractional momenta remain. Much of the sea of quark-antiquark pairs emerges from the splitting of gluons and is well described by perturbative evolution in quantum chromodynamics. However, experiments confirm that there is a non-perturbative component to the sea that is not well understood and hitherto has been difficult to calculate with ab initio non-perturbative methods. This non-perturbative structure shows up, perhaps most directly, in the flavor dependence of the sea antiquark distributions. While some of the general trends can be reproduced by models, there are features of the data that do not seem to be well described. This article discusses the experimental situation, the status of calculations and models, and the directions where these studies will progress in the near future.
↳ nucl-exnucl-thRept.Prog.Phys.(2019)·38 citations

Affiliations

first authorsco-authorsvia INSPIRE