Nuclear Theory·nucl-th

Tuesday·November 5, 2019

20 papers—12 primary·8 cross-listed

01
Beyond the charge radius: the information content of the fourth radial moment
P.-G. Reinhard🇩🇪 · W. Nazarewicz🇺🇸 · R.F. Garcia Ruiz🇨🇭
Measurements of atomic transitions in different isotopes offer key information on the nuclear charge radius. The anticipated high-precision experimental techniques, augmented by atomic calculations, will soon enable extraction of the higher-order radial moments of the charge density distribution. To assess the value of such measurements for nuclear structure research, we study the information content of the fourth radial moment $\rf$ by means of nuclear density functional theory and a multiple correlation analysis. We show that $\rf$ can be directly related to the surface thickness of nuclear density, a fundamental property of the atomic nucleus that is difficult to obtain for radioactive systems. Precise knowledge of these radial moments is essential to establish reliable constraints on the existence of new forces from precision isotope shift measurements .
nucl-thPRC(2020)·49 citations
02
Probing the partonic degrees of freedom in high multiplicity p-Pb collisions at $s_{N N} =$ 5.02 TeV
Wenbin Zhao🇨🇳 · Che Ming Ko🇺🇸 · Yu-Xin Liu🇨🇳 · Guang-You Qin🇨🇳 · Huichao Song🇨🇳
We investigate the role of partonic degrees of freedom in high multiplicity p-Pb collisions at $s_{N N} =$ 5.02 TeV carried out at the Large Hadron Collider (LHC) by studying the production and collective flow of identified hadrons at intermediate $p_{T}$ via the coalescence of soft and hard partons generated from viscous hydrodynamics (VISH2+1) and the energy loss model (LBT), respectively. We find that combining the intermediate $p_{T}$ hadrons from the coalescence with the low $p_{T}$ hadrons from hydrodynamics and high $p_{T}$ hadrons from the jet fragmentation, our Hydro-Coal-Frag model provides a nice description of the measured $p_{T}$ -spectra and the differential elliptic flow $v_{2} (p_{T})$ of pions, kaons and protons over the $p_{T}$ range from 0 to 6 GeV. We further demonstrate the necessity of including the quark coalescence contribution to reproduce the experimentally observed approximate number of constituent quark scaling of hadron $v_{2}$ at intermediate $p_{T}$ . Our results thus indicate the importance of partonic degrees of freedom and also hint at the possible formation of quark-gluon plasma in high multiplicity p+Pb collisions at the LHC.
nucl-thhep-phnucl-exPRL(2020)·100 citations
03
Pion-nucleon scattering to $O (p^{3})$ in heavy baryon SU(3) chiral perturbation theory
Bo-Lin Huang🇨🇳 · Jing Ou-Yang🇨🇳
We calculate the complete $T$ -matrices of pion-nucleon ( $π N$ ) scattering to the third order in heavy baryon SU(3) chiral perturbation theory. The baryon mass in the chiral limit $M_{0}$ and the low-energy constants are determined by fitting to phase shifts of $π N$ and the experimental octet-baryon masses simultaneously. By using these constants, we obtain the pion-nucleon sigma terms, $σ_{π N} = (34.57 \pm 11.85)$ MeV. We also find that a very small strangeness content of the proton, $y ≃ 0$ . The scattering lengths and the scattering volumes are predicted, which turn out to be in good agreement with those of other approaches and the available experiment data. The contributions from the third-order amplitudes are discussed in detail. We find that the contributions from the internal kaon lines of one-loop diagrams and the counterterms of the third order are sizeable. In addition, the issue of convergence is also discussed.
nucl-thhep-phPRD(2020)·16 citations
04
Hyperon interaction with dense nuclear matter and link to neutron stars
Laura Tolos🇩🇪
The theoretical status of the hyperon-nucleon and hyperon-hyperon interactions is reviewed, paying a special attention to chiral effective field theories. Results on hyperons in dense matter are presented and the consequences for the properties of neutron stars are analyzed.
nucl-thastro-ph.HEhep-phSpringer Proc.Phys.(2020)·0 citations
05
Neutron Shell Closure at N=32 and N=40 in Ar and Ca Isotopes
M. El Adri · M. Oulne
In this paper, we investigate features of the ground state of some nuclei far from the stability for isotope chains with proton numbers Z=18 and 20. Our aim is to predict the eventual existence of magic numbers in these exotic nuclei. For this purpose, we use two methods: the non relativistic Hartree-Fock-Bogoliubov (HFB) approach based on SLy4 Skyrme functional and the relativistic (so-called covariant) density functional theory (CDFT) by using the DD-ME2 force parametrization. We compare our results with the available experimental data and with the predictions of other models such as Finite Range Droplet Model (FRDM). Our present investigation predicts that N=32 and N=40 are magic numbers for Ar and Ca isotopes.
nucl-thEur.Phys.J.Plus(2020)·11 citations
06
$K^{-} p$ Correlation Function from High-Energy Nuclear Collisions and Chiral SU(3) Dynamics
Yuki Kamiya🇨🇳 · Tetsuo Hyodo🇯🇵 · Kenji Morita🇯🇵 · Akira Ohnishi🇯🇵 · Wolfram Weise🇩🇪
The two-particle momentum correlation function of a K^-p pair from high-energy nuclear collisions is evaluated in the KbarN-piSigma-piLambda coupled-channels framework. The effects of all coupled channels together with the Coulomb potential and the threshold energy difference between K^-p and Kbar0 n are treated completely for the first time. Realistic potentials based on the chiral SU(3) dynamics are used which fit the available scattering data. The recently measured correlation function is found to be well reproduced by allowing variations of the source size and the relative weight of the source function of piSigma with respect to that of KbarN. The predicted K^-p correlation function from larger systems, which is less affected by the piSigma source function, indicates that the investigation of its source size dependence is useful in providing further constraints in the study of the KbarN interaction.
nucl-thhep-phPRL(2020)·85 citations
07
Absorption of $ω$ and $ϕ$ mesons in the inclusive photonuclear reaction
Swapan Das🇮🇳
The $ω$ and $ϕ$ mesons dominantly decay outside the nucleus because the decay-lengths of them are much larger than the dimension of the nucleus. Therefore, the medium modification of the above mesons is studied through their absorption in the nucleus. CLAS collaboration at Jefferson Laboratory (Jlab) has investigated the absorption of the $ω$ and $ϕ$ mesons by measuring the nuclear transparency ratios for them in the $γ A \to ω (ϕ) X \to e^{+} e^{-} X$ reaction. The nuclear transparency ratios for both $ω$ and $ϕ$ mesons in the above reactions have been calculated, and those are compared with the experimental findings, reported from Jlab, to estimate the $ω$ meson nucleon and $ϕ$ meson nucleon cross sections in the nucleus.
nucl-thnucl-exEPJA(2019)·6 citations
08
Influence of surface effects on neutron skin in atomic nuclei
S.V. Lukyanov · A.I. Sanzhur
The influence of the diffuse surface layer of a finite nucleus on the mean square radii and their isotopic shift is investigated. We present the calculations within the Gibbs-Tolman approach using the experimental values of the nucleon separation energies. Results are compared with that obtained by means of direct variational method based on Fermi-like trial functions.
nucl-thNucl.Phys.Atom.Energy(2020)·1 citation
09
Dynamical freeze-out phenomena: The case of $K^{\pm}, ϕ$ transverse momentum spectra in collisions of Au(1.23 A GeV) + Au
B. Rabe🇩🇪 · B. Kämpfer🇩🇪
We argue on a continuous (dynamical) kinetic freeze-out of $K^{\pm}, ϕ$ observed at midrapidity in collisions Au(1.23 A GeV) + Au. The simulations by means of a transport model of BUU type point to time independent transverse momentum slope parameters after 20 fm/c. The complex interplay of expansion dynamics and strangeness production/exchange/absorption as well as elastic scatterings involved in the reaction network does not support the previous interpretation of a late freeze-out of $K^{-}$ due to larger cross sections.
nucl-thParticles(2019)·0 citations
10
Quark number scaling of $p_{T}$ spectra for $Ω$ and $ϕ$ in relativistic heavy-ion collisions
Jun Song🇨🇳 · Feng-lan Shao🇨🇳 · Zuo-tang Liang🇨🇳
We show that the experimental data of transverse momentum ( $p_{T}$ ) spectra of $Ω$ baryon and $ϕ$ meson at mid-rapidity in heavy-ion collisions exhibit the constituent quark number scaling in a wide energy range from RHIC to LHC. Such a scaling behavior is a direct consequence of quark combination mechanism via equal velocity combination and provides a very convenient way to extract the $p_{T}$ spectrum of strange quarks at hadronization. We present the results of strange quarks obtained from the available data and study the properties in particular the energy dependence of the averaged transverse momentum $⟨ p_{T} ⟩$ and the transverse radial flow velocity $⟨ β ⟩$ with a hydrodynamics-motivated blast-wave model.
nucl-thnucl-exPRC(2020)·16 citations
11
Theory Summary at Strangeness in Quark Matter 2019
Jacquelyn Noronha-Hostler🇺🇸
This is the theory summary of Strangeness in Quark Matter 2019 conference. Results include the state-of-the-art updates to the Quantum Chromodynamics (QCD) phase diagram with contributions both from heavy-ion collisions and nuclear astrophysics, studies on the QCD freeze-out lines, and several aspects regarding small systems including collectivity, heavy flavor dynamics, strangeness, and hard probes.
nucl-thastro-ph.HEhep-lathep-phSpringer Proc.Phys.(2020)·2 citations
12
D meson sensitivity to a system size scan at LHC
Roland Katz🇫🇷 · Jacquelyn Noronha-Hostler🇺🇸 · Caio A. G. Prado🇨🇳 · Alexandre A. P. Suaide🇧🇷
Experimental measurements in pA collisions indicate no D meson suppression ( $R_{pPb} \sim 1$ ) but a surprisingly large $v_{2}$ . To better understand these results we propose a system size scan at the LHC involving $^{16}$ OO, $^{40}$ ArAr, $^{129}$ XeXe and $^{208}$ PbPb collisions. Using Trento+ v-USPhydro+DAB-MOD to make predictions, we find that the $R_{AA}$ tends towards unity when the system size is decreased, but nonetheless, in the most central collisions $v_{2} {2}$ is almost independent of the colliding system. These results are analyzed in light of path length and initial eccentricity variations.
nucl-thhep-exhep-phSpringer Proc.Phys.(2020)·1 citation
13
The range of elementary interactions: a criticism of the standard classroom approach
B. Hernández-Bermejo
The finite scope of the some elementary interactions is usually presented to Physics students as a natural consequence of the time-energy uncertainty relation. It is demonstrated that this heuristic derivation is not a priori valid. Accordingly, it is argued the doubtful usefulness of this "proof" in the classroom, for it may lead to misconceptions.
↳ physics.pop-phnucl-thphysics.ed-phEur.J.Phys.(1997)·0 citations
14
Soft contribution to the damping rate of a hard photon in a weakly magnetized hot medium
Ritesh Ghosh🇮🇳 · Bithika Karmakar🇮🇳 · Munshi G Mustafa🇮🇳
We consider weakly magnetized hot QED plasma comprising electrons and positrons. There are three distinct dispersive (longitudinal and two transverse) modes of a photon in a thermo-magnetic medium. At lowest order in coupling constant, photon is damped in this medium via Compton scattering and pair creation process. We evaluate the damping rate of hard photon by calculating the imaginary part of the each transverse dispersive modes in a thermo-magnetic QED medium. We note that one of the fermions in the loop of one-loop photon self-energy is considered as soft and the other one is hard. Considering the resummed fermion propagator in a weakly magnetized medium for the soft fermion and the Schwinger propagator for hard fermion, we calculate the soft contribution to the damping rate of hard photon. In weak field approximation the thermal and thermo-magnetic contributions to damping rate get separated out for each transverse dispersive mode. The total damping rate for each dispersive mode in presence of magnetic field is found to be reduced than that of the thermal one. This formalism can easily be extended to QCD plasma.
↳ hep-phhep-latnucl-thPRD(2020)·17 citations
15
Nonperturbative renormalization of staple-shaped Wilson line operators in lattice QCD
Phiala Shanahan🇺🇸 · Michael L. Wagman🇺🇸 · Yong Zhao🇺🇸
Quark bilinear operators with staple-shaped Wilson lines are used to study transverse-momentum-dependent parton distribution functions (TMDPDFs) from lattice quantum chromodynamics (QCD). Here, the renormalization factors for the isovector operators, including all mixings between operators with different Dirac structures, are computed nonperturbatively in the regularization-independent momentum subtraction scheme for the first time. This study is undertaken in quenched QCD with three different lattice spacings. With Wilson flow applied to the gauge fields in the calculations, the operator mixing pattern due to chiral symmetry breaking with the lattice regularization is found to be significantly different from that predicted by one-loop lattice perturbation theory calculations. These results constitute a critical step towards the systematic extraction of TMDPDFs from lattice QCD.
↳ hep-lathep-phnucl-thPRD(2020)·80 citations
16
Chiral magnetic response to arbitrary axial imbalance
Miklos Horvath🇨🇳 · Defu Hou🇨🇳 · Jinfeng Liao🇺🇸 · Hai-cang Ren🇺🇸
The response of chiral fermions to time and space dependent axial imbalance & constant magnetic field is analyzed. The axialvector-vector-vector (AVV) three-point function is studied using a real-time approach at finite temperature in the weak external field approximation. The chiral magnetic conductivity is given analytically for noninteracting fermions. It is pointed out that local charge conservation plays an important role when the axial imbalance is inhomogeneous. Proper regularization is needed which makes the constant axial imbalance limit delicate: for static but spatially oscillating chiral charge the current of the chiral magnetic effect (CME) vanishes. In the homogeneous (but possible time-dependent) limit of the axial imbalance the CME current is determined solely by the chiral anomaly. As a phenomenological consequence, the observability of the charge asymmetry caused by the CME turns out to be a matter of interplay between various scales of the system. Possible plasma instabilities resulting from the gradient corrections to the CME current are also pointed out.
↳ hep-phcond-mat.str-elhep-thnucl-thPRD(2020)·18 citations
17
Spectrum of fully-heavy tetraquarks from a diquark+antidiquark perspective
M. A. Bedolla🇲🇽 · J. Ferretti🇺🇸 · C. D. Roberts🇨🇳 · E. Santopinto🇮🇹
Using a relativized diquark model Hamiltonian, we calculate the masses of $J^{P C} = 0^{++}$ ground-state tetraquarks in the following systems: $b s b ˉ s ˉ$ , $bb n ˉ n ˉ$ ( $n = u, d$ ), $bb s ˉ s ˉ$ , $cc c ˉ c ˉ$ , $bb b ˉ b ˉ$ , $b c b ˉ c ˉ$ and $bb c ˉ c ˉ$ . We also compute extensive spectra for the fully-heavy quark flavour combinations. Finally, as a test of the diquark model approach, we compute the masses of fully-heavy baryons in the diquark model. Our results may be compared soon to the forthcoming experimental data for fully-heavy three-quark systems.
↳ hep-phhep-exhep-latnucl-ex+1EPJC(2020)·190 citations
18
The dipole picture and the non-relativistic expansion
Miguel Ángel Escobedo🇫🇮 · Tuomas Lappi🇫🇮
We study exclusive quarkonium production in the dipole picture at next-to-leading order (NLO) accuracy, using the non-relativistic expansion for the quarkonium wavefunction. This process offers one of the best ways to obtain information about gluon distributions at small $x$ , in ultraperipheral heavy ion collisions and in deep inelastic scattering. The quarkonium light cone wave functions needed in the dipole picture have typically been available only at tree level, either in phenomenological models or in the nonrelativistic limit. In this paper, we discuss the compatibility of the dipole approach and the non-relativistic expansion and compute NLO relativistic corrections to the quarkonium light-cone wave function in light-cone gauge. Using these corrections we recover results for the NLO decay width of quarkonium to $e^{+} e^{-}$ and we check that the non-relativistic expansion is consistent with ERBL evolution and with B-JIMWLK evolution of the target. The results presented here will allow computing the exclusive quarkonium production rate at NLO once the one loop photon wave function with massive quarks, currently under investigation, is known.
↳ hep-phnucl-thPRD(2020)·23 citations
19
Jet quenching test of the QCD matter created at RHIC and the LHC needs opacity-resummed medium induced radiation
Xabier Feal🇪🇸 · Carlos A. Salgado🇪🇸 · Ricardo A. Vazquez🇪🇸
After almost two decades of investigation, jet quenching has become a fundamental tool to study the properties of the QCD matter produced in high-energy nuclear collisions. Despite the large progress in both experimental and theoretical tools, several unknowns remain to be solved. In particular the systematics of the QCD matter parameters extracted at different energies and centralities is still puzzling. On the other hand, a lot of attention has been put in the last few years to a correct resummation of the multiple scatterings that the particles of the jet suffer when traversing the QCD matter. Present formalisms have substantially improved the multiple-soft or single hard scattering approximations, common in the last twenty years. We show here that medium parameters extracted with full resummed medium-induced gluon radiation spectra significantly differ from these two extreme approximations, providing a natural systematics for different collision energies and centralities, with no inconsistencies. For the case of the full resummation this ensures that the density of scattering centers as a function of the temperature qualitatively agree with the equation of state computed in lattice QCD.
↳ hep-phnucl-thPLB(2021)·49 citations
20
Time-evolution of magnetic field in hot nuclear matter with fluctuating topological charge
Kirill Tuchin🇺🇸
The time-evolution of the magnetic field in hot homogeneous nuclear matter has two qualitatively different stages separated by the sphaleron transition time $τ_{c}$ . At early times the axial chemical potential and the corresponding chiral conductivity $σ_{χ}$ are slow functions of time. The soft chiral modes $k < σ_{χ}$ of the magnetic field grow exponentially with time, which is known as the chiral instability. At later times $σ_{χ}$ fluctuates due to the sphaleron transitions and can be regarded as a random process. It is argued that the average magnetic field is exponentially damped at later times. The time-evolution of the average magnetic energy is more complicated and depends on the electrical conductivity of the chiral matter but does not depend on chirality. It exhibits instability only if the matter is a poor electrical conductor, such as the quark-gluon plasma near the critical temperature. The precise conditions for the instability and the growth rate of the unstable modes are derived.
↳ hep-phnucl-thPRC(2020)·12 citations

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