Nuclear Theory·nucl-th

Monday·June 6, 2022

11 papers—5 primary·6 cross-listed

01
A new Microscopic Model for $J / ψ$ Production in Heavy Ion Collisions
Denys Yen Arrebato Villar🇫🇷 · Jiaxing Zhao🇫🇷 · Joerg Aichelin🇫🇷 · Pol Bernard Gossiaux🇫🇷
We present a new model for the creation of \J mesons in ultrarelativistic heavy ion collisions, which allows to follow the individual heavy quarks from their creation until the detector through the Quark Gluon Plasma (QGP), which is formed in these collisions and described by the EPOS2 event generator. The \cc quarks interact via a potential, based on results of lattice gauge calculations. The annihilation and creation of \J is described by a density matrix approach whose time evolution is studied in the expanding system. The comparison with PbPb data at $s$ =5.02 TeV shows that this model can describe simultaneously the nuclear modification factor $R_{AA}$ and the elliptic flow $v_{2}$ of the \J at low transverse momen
nucl-thPRC(2023)·26 citations
02
Single-particle properties of the near-threshold proton-emitting resonance in $^{11}$ B
Le-Anh Nguyen · Minh-Loc Bui · Naftali Auerbach · Vladimir Zelevinsky
The excitation function of proton elastic scattering from $^{10}$ Be at keV energy is calculated using the self-consistent Skyrme Hartree-Fock in the continuum method. The calculation successfully reproduces the narrow near-threshold proton-emitting resonance ( $E_{x} = 11.4$ MeV, $Γ = 6$ keV, and quantum number $J^{π} = 1/ 2^{+}$ ) in $^{11}$ B relevant to the $β$ -delayed proton emission of $^{11}$ Be. This supports the recent experimental result of Y. Ayyad \textit{et al.} at the ReA3 re-accelerator facility of the National Superconducting Cyclotron Laboratory (NSCL) at the Michigan State University. The resonance is interpreted as the $s_{1/2}$ single-proton resonance state in the Skyrme Hartree-Fock mean-field theory.
nucl-thnucl-exPRC(2022)·11 citations
03
Radiative proton capture on $^{15} N$ within effective field theory
Sangyeong Son · Shung-Ichi Ando · Yongseok Oh
The astrophysical $S$ factor for the radiative proton capture process on the $^{15} N$ nucleus, i.e., $^{15} N (p, γ)^{16} O$ , at stellar energies are studied within the framework of the cluster effective field theory. The thermonuclear $^{15} N (p, γ)^{16} O$ reaction links the type-I to type-II cycles of the carbon-nitrogen-oxygen cycle and affects the abundances of elements in the univere. For investigating this reaction in the effective field theory formalism, we first construct an effective Lagrangian that is appropriate for this reaction at low-energies. Since the intermediate excited states of the $^{16} O$ nucleus have a crucial role in this reaction, we include these resonances in the formalism. The corresponding radiative capture amplitudes and cross section are calculated, which lead to the astrophysical $S$ factor. The low energy constants introduced in the effective Lagrangian are determined by fitting the theoretical results to the observed $S$ factors in the range of $130 keV < E_{p} < 2500 keV$ using three different experimental data sets. Considering the recent data sets, we obtain $S (0) = 29.8 \mbox - 34.1 keV b$ , which is in a good agreement with the estimates from $R$ -matrix approaches in the literature. The values of $S$ at the Gamow energy are found to be larger than $S (0)$ values by about $10%$ .
nucl-thnucl-exPRC(2022)·5 citations
04
New insights into the oscillation of the nucleon electromagnetic form factors
Qin-He Yang🇨🇳 · Ling-Yun Dai🇨🇳 · Di Guo🇨🇳 · Johann Haidenbauer🇩🇪 · Xian-Wei Kang🇨🇳 · Ulf-G. Meißner🇩🇪
The electromagnetic form factors of the proton and the neutron in the timelike region are investigated. Electron-positron annihilation into antinucleon-nucleon ( $N ˉ N$ ) pairs is treated in distorted wave Born approximation, including the final-state interaction in the $N ˉ N$ system. The latter is obtained by a Lippmann-Schwinger equation for $N ˉ N$ potentials derived within SU(3) chiral effective field theory. By fitting to the phase shifts and (differential) cross section data, a high quality description is achieved. With these amplitudes, the oscillations of the electromagnetic form factors of the proton and the neutron are studied. It is found that each of them can be described by two fractional oscillators. One is characterized as \lq overdamped' and dominates near the threshold, while the other is \lq underdamped' and plays an important role in the high-energy region. These two oscillators are essential to understand the distributions of polarized electric charges induced by hard photons for the nucleons.
nucl-thhep-phSci.Bull.(2023)·28 citations
05
Correcting the $B_{A}$ coalescence factor at GSI-HADES and RHIC-BES energies
Apiwit Kittiratpattana🇩🇪 · Tom Reichert🇩🇪 · Jan Steinheimer🇩🇪 · Christoph Herold🇹🇭 · Ayut Limphirat🇹🇭 · Yupeng Yan🇹🇭 · Marcus Bleicher🇩🇪
We investigate the coalescence factors $B_{2}$ and $B_{3}$ at low collision energies ( $s_{NN} < 6$ GeV) with special focus on the HADES and RHIC-BES experiments. It is shown that, in order to properly interpret the coalescence factors $B_{A}$ , two important corrections are necessary: I) $B_{2}$ has to be calculated using the proton $\times$ neutron yields in the denominator, instead of the square of the proton yield, and II) the primordial proton (neutron) densities have to be used for the normalization and not the final state (free) protons (neutrons). Both effects lead to a drastic reduction of $B_{2}$ and $B_{3}$ at low energies. This reduction decreases the discrepancy between the volumes extracted from HBT measurements and the volumes extracted from the coalescence factor ( $V \propto 1/ B_{2}$ ). While at HADES and low RHIC-BES energies these corrections are substantial, they become irrelevant above $s_{NN} > 6$ GeV. The proposed correction method is model independent and is only based on the measurement of protons, clusters and charged pions.
nucl-thnucl-exPRC(2022)·10 citations
06
Chiral anomaly induces superconducting baryon crystal
Geraint W. Evans🇬🇧 · Andreas Schmitt🇬🇧
It was previously shown within chiral perturbation theory that the ground state of QCD in a sufficiently large magnetic field and at nonvanishing, but not too large, baryon chemical potential is a so-called chiral soliton lattice. The crucial ingredient of this observation was the chiral anomaly in the form of a Wess-Zumino-Witten term, which couples the baryon chemical potential to the magnetic field and the gradient of the neutral pion field. It was also shown that the chiral soliton lattice becomes unstable towards charged pion condensation at larger magnetic fields. We point out that this instability bears a striking resemblance to the second critical magnetic field of a type-II superconductor, however with the superconducting phase appearing upon increasing the magnetic field. The resulting phase has a periodically varying charged pion condensate that coexists with a neutral pion supercurrent. We construct this phase analytically in the chiral limit and show that it is energetically preferred. Just like an ordinary type-II superconductor, it exhibits a hexagonal array of magnetic flux tubes, and, due to the chiral anomaly, a spatially oscillating baryon number of the same crystalline structure.
↳ hep-thhep-phnucl-thJHEP(2022)·39 citations
07
An Improved Method for Coupling Hydrodynamics with Astrophysical Reaction Networks
M. Zingale · M. P. Katz · A. Nonaka · M. Rasmussen
Reacting astrophysical flows can be challenging to model because of the difficulty in accurately coupling hydrodynamics and reactions. This can be particularly acute during explosive burning or at high temperatures where nuclear statistical equilibrium is established. We develop a new approach based on the ideas of spectral deferred corrections (SDC) coupling of explicit hydrodynamics and stiff reaction sources as an alternative to operator splitting that is simpler than the more comprehensive SDC approach we demonstrated previously. We apply the new method to a double detonation problem with a moderately-sized astrophysical nuclear reaction network and explore the timestep size and reaction network tolerances to show that the simplified-SDC approach provides improved coupling with decreased computational expense compared to traditional Strang operator splitting. This is all done in the framework of the Castro hydrodynamics code, and all algorithm implementations are freely available.
↳ astro-ph.IMnucl-thApJ(2022)·7 citations
08
Information field based global Bayesian inference of the jet transport coefficient
Man Xie🇨🇳 · Weiyao Ke🇺🇸 · Hanzhong Zhang🇨🇳 · Xin-Nian Wang🇺🇸
Bayesian statistical inference is a powerful tool for model-data comparisons and extractions of physical parameters that are often unknown functions of system variables. Existing Bayesian analyses often rely on explicit parametrizations of the unknown function. It can introduce long-range correlations that impose fictitious constraints on physical parameters in regions of the variable space that are not probed by the experimental data. We develop an information field (IF) approach to modeling the prior distribution of the unknown function that is free of long-range correlations. We apply the IF approach to the first global Bayesian inference of the jet transport coefficient $q^$ as a function of temperature ( $T$ ) from all existing experimental data on single-inclusive hadron, di-hadron and $γ$ -hadron spectra in heavy-ion collisions at RHIC and LHC energies. The extracted $q^/ T^{3}$ exhibits a strong $T$ -dependence as a result of the progressive constraining power when data from more central collisions and at higher colliding energies are incrementally included. The IF method guarantees that the extracted $T$ -dependence is not biased by a specific functional form.
↳ hep-phnucl-thPRC(2023)·66 citations
09
Towards a theory of hadron resonances
Maxim Mai🇩🇪 · Ulf-G. Meißner🇩🇪 · Carsten Urbach🇩🇪
In this review, we present the current state of the art of our understanding of the spectrum of excited strongly interacting particles and discuss methods that allow for a systematic and model-independent calculation of the hadron spectrum. These are lattice QCD and effective field theories. Synergies between both approaches can be exploited allowing for deeper understanding of the hadron spectrum. Results based on effective field theories and hadron-hadron scattering in lattice QCD or combinations thereof are presented and discussed. We also show that the often used Breit-Wigner parameterization is at odds with chiral symmetry and should not be used in case of strongly coupled channels.
↳ hep-phhep-exhep-latnucl-ex+1Phys.Rept.(2023)·156 citations
10
Electron Mass Singularities in Semileptonic Kaon Decays
Chien-Yeah Seng🇩🇪 · William J. Marciano🇺🇸 · Ulf-G. Meißner🇩🇪
We show that recent improvements in the $O (α)$ long-distance quantum electrodynamics (QED) corrections to the radiative inclusive $K_{e 3}$ decay rate using the Sirlin representation are free from infrared divergences and collinear electron mass singularities in the limit $m_{e} \to 0$ , as predicted by the Kinoshita-Lee-Nauenberg theorem. We also verify that in massless QED with the simultaneous dimensional regularization of QED photon infrared divergences and electron mass singularities leads to the same result for the inclusive rate in the limit of four space-time dimensions. The equivalence of the two approaches results in part from an interesting interplay between a small chirality-breaking effect in the massless electron limit and the generalization of space-time algebra and phase space integrals to $d > 4$ dimensions. Our finding supports the small theoretical uncertainty claimed for $K_{e 3}$ radiative inclusive rates and reaffirms its utility in precision unitarity tests of the quark mixing matrix.
↳ hep-phhep-exhep-latnucl-ex+1PRD(2022)·3 citations
11
Axion effects in the stability of hybrid stars
Bruno S. Lopes🇧🇷 · Ricardo L. S. Farias🇧🇷 · Veronica Dexheimer🇺🇸 · Aritra Bandyopadhyay🇨🇳 · Rudnei O. Ramos🇧🇷
We investigate the effects of including strong charge-parity (CP) violating effects through axion fields in the microscopic equation of state of massive hybrid neutron stars. We assume that their cores contain deconfined quark matter and include the effects of axions via an effective 't Hooft determinant interaction. The hadronic crusts are described using different approaches in order to make our results more general. We find that the presence of axions stabilizes massive hybrid neutron stars against gravitational collapse by weakening the deconfinement phase transition and bringing it to lower densities. This enables to reproduce hybrid neutron stars in agreement with modern astrophysical constraints.
↳ hep-phastro-ph.HEhep-thnucl-thPRD(2022)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE