Nuclear Theory·nucl-th

Thursday·January 14, 2021

13 papers—4 primary·9 cross-listed

01
[Submitted on 13 Jan 2021]
Unexpectedly enhanced $α$ -particle preformation in $^{48}$ Ti probed by the $(p, p α)$ reaction
Yasutaka Taniguchi🇯🇵 · Kazuki Yoshida🇯🇵 · Yohei Chiba🇯🇵 · Yoshiko Kanada-En'yo🇯🇵 · Masaaki Kimura🇯🇵 · Kazuyuki Ogata🇯🇵
The formation of $α$ particle on nuclear surface has been a fundamental problem since the early age of nuclear physics. It strongly affects the $α$ decay lifetime of heavy and superheavy elements, level scheme of light nuclei, and the synthesis of the elements in stars. However, the $α$ -particle formation in medium-mass nuclei has been poorly known despite its importance. Here, based on the $^{48} Ti (p, p α)^{44} Ca$ reaction analysis, we report that the $α$ -particle formation in a medium-mass nucleus $^{48} Ti$ is much stronger than that expected from a mean-field approximation, and the estimated average distance between $α$ particle and the residue is as large as 4.5 fm. This new result poses a challenge of describing four nucleon correlations by microscopic nuclear models.
Comments:
6 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2101.04820 [pdf]
PRC(2021)·21 citations
02
[Submitted on 13 Jan 2021]
Exploring effects of tensor force and its strength via neutron drops
Zhiheng Wang · Tomoya Naito · Haozhao Liang · Wen Hui Long
The tensor-force effects on the evolution of the spin-orbit splittings in the neutron drops are investigated within the framework of the relativistic Hartree-Fock theory. For fair comparisons on the pure mean-field level, the results of the relativistic Brueckner-Hartree-Fock calculation with the Bonn A interaction are adopted as meta-data. Through a quantitative analysis, we certify that the $π$ -pseudovector ( $π$ -PV) coupling affects the evolutionary trend through the tensor force embedded. The strength of the tensor force is explored by enlarging the strength $f_{π}$ of the $π$ -PV coupling. It is found that weakening the density dependence of $f_{π}$ is slightly better than enlarging it with a factor. We thus provide a semiquantitative support for the \textit{renormalization persistency} of the tensor force within the framework of density functional theory. This will serve as an important guidance for the further development of the relativistic effective interactions with particular focus on the tensor force.
Comments:
9 pages, 4 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2101.04860 [pdf]
CPC(2021)·5 citations
03
[Submitted on 13 Jan 2021]
Impact of strong magnetic fields on the inner crust of neutron stars
S. S. Bao🇨🇳 · J. N. Hu🇨🇳 · H. Shen🇨🇳
We study the impact of strong magnetic fields on the pasta phases that are expected to exist in the inner crust of neutron stars. We employ the relativistic mean field model to describe the nucleon interaction and use the self-consistent Thomas-Fermi approximation to calculate the nonuniform matter in neutron star crust. The properties of pasta phases and crust-core transition are examined. It is found that as the magnetic field strength $B$ is less than $1 0^{17}$ G, the effects of magnetic field are not evident comparing with the results without magnetic field. As $B$ is stronger than $1 0^{18}$ G, the onset densities of pasta phases and crust-core transition density decrease significantly, and the density distributions of nucleons and electrons are also changed obviously.
Comments:
13 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2101.04868 [pdf]
PRC(2021)·10 citations
04
[Submitted on 13 Jan 2021]
Vorticity and Polarization in Heavy Ion Collisions: Hydrodynamic Models
Iurii Karpenko🇨🇿
Fluid dynamic approach is a workhorse for modelling collective dynamics in relativistic heavy-ion collisions. The approach has been successful in describing various features of the momentum distributions of hadrons produced in the heavy-ion collisions, such as $p_{T}$ spectra, flow coefficients $v_{n}$ etc. As such, the description of the phenomenon of polarization of $Λ$ hyperons in heavy-ion collisions has to be incorporated into the hydrodynamic approach. We start this chapter by introducing different definitions of vorticity in relativistic fluid dynamics. Then we present a derivation of the polarization of spin 1/2 fermions in the relativistic fluid. The latter is directly applied to compute the spin polarization of the $Λ$ hyperons, which are produced from the hot and dense medium, described with fluid dynamics. It is followed by a review of the existing calculations of global or local polarization of $Λ$ hyperons in different hydrodynamic models of relativistic heavy-ion collisions. We particularly focus on the explanations of the collision energy dependence of the global $Λ$ polarization from the different hydrodynamic models, the polarization component in the beam direction as well as on the origins of the global and local $Λ$ polarization.
Comments:
39 pages; to appear in "Strongly Interacting Matter under Rotation", edited by F. Becattini, J. Liao and M. Lisa, Lecture Notes in Physics series. Due to the nature of the review, there is a text overlap with arXiv:1501.04468, arXiv:1610.04717, arXiv:1610.02506, arXiv:1707.07984, arXiv:1810.02706
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2101.04963 [pdf]
14 citations
05
[Submitted on 4 Jun 2020] (cross-list from nucl-ex)
Comment on "Search for $η^{'}$ Bound Nuclei in the $^{12} C (γ, p)$ Reaction with Simultaneous Detection of Decay Products"
H. Fujioka · K. Itahashi · V. Metag · M. Nanova · Y.K. Tanaka
We comment on a recent paper by the LEPS2/BGOegg Collaboration [Phys. Rev. Lett. 124, 202501 (2020), arXiv:2005.03449].
Comments:
accepted for publication in Physical Review Letters
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2006.02912 [pdf]
PRL(2021)·5 citations
06
[Submitted on 12 Jan 2021] (cross-list from hep-ph)
Quarkonium propagation in the quark gluon plasma
Rishi Sharma🇮🇳
In relativistic heavy ion collisions at RHIC and the LHC, a quark gluon plasma (QGP) is created for a short duration of about 10fm/c. Quarkonia (bound states of $c c ˉ$ and $b b ˉ$ ) are sensitive probes of this phase on length scales comparable to the size of the bound states which are less than 1fm. Observations of quarkonia in these collisions provide us with a lot of information about how the presence of a QGP affects various quarkonium states. This has motivated the development of the theory of heavy quarks and their bound states in a thermal medium, and its application to the phenomenology of quarkonia in heavy ion collisions. We review some of these developments here.
Comments:
34 pages, 7 figures, Invited review article for EPJ ST
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2101.04268 [pdf]
Eur.Phys.J.ST(2021)·25 citations
07
[Submitted on 12 Jan 2021] (cross-list from hep-ph)
Dynamic Jet Charge
Zhong-Bo Kang🇺🇸 · Xiaohui Liu🇨🇳 · Sonny Mantry🇺🇸 · M.C. Spraker🇺🇸 · Tyler Wilson🇺🇸
We propose a modified definition of the jet charge, the "dynamic jet charge", where the constant jet momentum fraction weighting parameter, $κ$ , in the standard jet charge definition is generalized to be a function of a dynamical property of the jet or the individual jet constituents. The dynamic jet charge can complement analyses based on the standard definition and give improved discrimination between quark and gluon initiated jets and between jets initiated by different quark flavors. We focus on the specific scenario where each hadron in the jet contributes to the dynamic jet charge with a $κ$ -value dynamically determined by its jet momentum fraction. The corresponding dynamic jet charge distributions have qualitatively distinct features and are typically characterized by a multiple peak structure. For proton-proton collisions, compared to the standard jet charge, the dynamic jet charge gives significantly improved discrimination between quark and gluon initiated jets and comparable discrimination between $u$ - and $d$ -quark initiated jets. In Pythia simulations of heavy ion collisions, the dynamic jet charge is found to have higher jet discrimination power compared to the standard jet charge, remaining robust against the increased contamination from underlying event. We also present phenomenological applications of the dynamic jet charge to probe nuclear flavor structure.
Comments:
22 pages, 28 figures. Extended discussion and figures added towards the end of section V. New section (VII) added with likelihood ratio analysis of jet charge discrimination. Version to appear in Physical Review D
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2101.04304 [pdf]
PRD(2021)·21 citations
08
[Submitted on 12 Jan 2021] (cross-list from hep-ph)
Quantum Anomalous Energy Effects on the Nucleon Mass
Xiangdong Ji🇺🇸 · Yizhuang Liu🇨🇳
Apart from the quark and gluon kinetic and potential energies, the nucleon mass includes a novel energy of pure quantum origin resulting from anomalous breaking of scale symmetry. We demonstrate the effects of this quantum anomalous energy (QAE) in QED, as well as in a toy 1+1 dimensional non-linear sigma model where it contributes non-perturbatively, in a way resembling the Higgs mechanism for the masses of matter particles in electro-weak theory. The QAE contribution to the nucleon mass can be explained using a similar mechanism, in terms of a dynamical response of the gluonic scalar field through Higgs-like couplings between the nucleon and scalar resonances. In addition, the QAE sets the scale for other energies in the nucleon through a relativistic virial theorem, and contributes a negative pressure to confine the colored quarks.
Comments:
5 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2101.04483 [pdf]
SCPMA(2021)·40 citations
09
[Submitted on 12 Jan 2021] (cross-list from hep-ph)
Simultaneous Monte Carlo analysis of parton densities and fragmentation functions
E. Moffat🇺🇸 · W. Melnitchouk🇺🇸 · T. C. Rogers🇺🇸 · N. Sato🇺🇸
We perform a comprehensive new Monte Carlo analysis of high-energy lepton-lepton, lepton-hadron and hadron-hadron scattering data to simultaneously determine parton distribution functions (PDFs) in the proton and parton to hadron fragmentation functions (FFs). The analysis includes all available semi-inclusive deep-inelastic scattering and single-inclusive $e^{+} e^{-}$ annihilation data for pions, kaons and unidentified charged hadrons, which allows the flavor dependence of the fragmentation functions to be constrained. Employing a new multi-step fitting strategy and more flexible parametrizations for both PDFs and FFs, we assess the impact of different data sets on sea quark densities, and confirm the previously observed suppression of the strange quark distribution. The new fit, which we refer to as "JAM20-SIDIS", will allow for improved studies of universality of parton correlation functions, including transverse momentum dependent (TMD) distributions, across a wide variety of process, and the matching of collinear to TMD factorization descriptions.
Comments:
34 pages, 13 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2101.04664 [pdf]
PRD(2021)·145 citations
10
[Submitted on 12 Jan 2021] (cross-list from hep-th)
Hydrodynamics of spin currents
Domingo Gallegos🇳🇱 · Umut Gursoy🇳🇱 · Amos Yarom🇮🇱
We study relativistic hydrodynamics in the presence of a non vanishing spin chemical potential. Using a variety of techniques we carry out an exhaustive analysis, and identify the constitutive relations for the stress tensor and spin current in such a setup, allowing us to write the hydrodynamic equations of motion to second order in derivatives. We then solve the equations of motion in a perturbative setup and find surprisingly good agreement with measurements of global $Λ$ -hyperon polarization carried out at RHIC.
Comments:
8 pages, 1 figure; v3: references added, typos corrected
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2101.04759 [pdf]
SciPost Phys.(2021)·155 citations
11
[Submitted on 13 Jan 2021] (cross-list from hep-ph)
The $sQ q ˉ q ˉ$ $(q = u, d; Q = c, b)$ tetraquarks in the chiral quark model
Gang Yang🇨🇳 · Jialun Ping🇨🇳 · Jorge Segovia🇪🇸
The low-lying $s Q q ˉ q ˉ$ $(q = u, d, Q = c, b)$ tetraquark states with $J^{P} = 0^{+}$ , $1^{+}$ and $2^{+}$ , and in the isoscalar and isovector sectors, are systematically investigated in the framework of real- and complex-scaling range of a chiral quark model, whose parameters have been fixed in advance describing hadron, hadron-hadron and multiquark phenomenology, and thus all results presented here are pure predictions. Each tetraquark configuration, compatible with the quantum numbers studied, is taken into account; this includes meson-meson, diquark-antidiquark and K-type arrangements of quarks with all possible color wave functions in four-body sector. Among the different numerical techniques to solve the Schrödinger-like 4-body bound state equation, we use a variational method in which the trial wave function is expanded in complex-range Gaussian basis functions, because its simplicity and flexibility. Several compact bound states and narrow resonances are found in both charm-strange $cs q ˉ q ˉ$ and bottom-strange $b s q ˉ q ˉ$ tetraquark sectors, most of them as a product of the strong coupling between the different channels. The so-called $X_{0, 1} (2900)$ signals, recently found by the LHCb collaboration, are unstable in our formalism with several candidates in the single-channel computations.
Comments:
19 pages, 24 Tables, 13 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2101.04933 [pdf]
PRD(2021)·41 citations
12
[Submitted on 13 Jan 2021] (cross-list from hep-lat)
A Demonstration of Hadron Mass Origin from QCD Trace Anomaly
Fangcheng He🇨🇳 · Peng Sun🇨🇳 · Yi-Bo Yang🇨🇳
Quantum chromodynamics (QCD) claims that the major source of the nucleon invariant mass is not the Higgs mechanism but the trace anomaly in QCD energy momentum tensor. Although experimental and theoretical results support such conclusion, a direct demonstration is still absent. We present the first Lattice QCD calculation of the quark and gluon trace anomaly contributions to the hadron masses, using the overlap fermion on the 2+1 flavor dynamical Domain wall quark ensemble at $m_{π} = 340$ MeV and lattice spacing $a =$ 0.1105 fm. The result shows that the gluon trace anomaly contributes to most of the nucleon mass, and the contribution in the pion state is smaller than that in others nearly by a factor $\sim$ 10 since the gluon trace anomaly density inside pion is different from the other hadrons and the magnitude is much smaller. The gluon trace anomaly coefficient $β / g^{3} = - 0.056 (6)$ we obtained is consistent with its regularization independent leading order value $(- 11 + \frac{2 N _{f}}{3}) / (4 π)^{2}$ perfectly.
Comments:
9 pages, 5 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2101.04942 [pdf]
PRD(2021)·25 citations
13
[Submitted on 13 Jan 2021] (cross-list from hep-ph)
Novel twist-three transverse-spin sum rule for the proton and related generalized parton distributions
Yuxun Guo🇺🇸 · Xiangdong Ji🇺🇸 · Kyle Shiells🇺🇸
We derive a new twist-3 partonic sum rule for the transverse spin of the proton, which involves the well-know quark spin structure function $g_{T} (x) = g_{1} (x) + g_{2} (x)$ , the less-studied but known transverse gluon polarization density $Δ G_{T} (x)$ , and quark and gluon canonical orbital angular momentum densities associated with transverse polarization. This is the counter part of the sum rule for the longitudinal spin of the proton derived by Jaffe and Manohar previously. We relate the partonic canonical orbital angular momentum densities to a new class of twist-3 generalized parton distribution functions which are potentially measurable in deep-virtual exclusive processes. We also discuss in detail an important technicality related to the transverse polarization in the infinite momentum frame, i.e., separation of intrinsic contributions from the extrinsic ones. We apply our finding to the transverse-space distributions of partons, angular momentum, and magnetic moment, respectively, in a transversely polarized proton.
Comments:
1 figure, 49 pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2101.05243 [pdf]
NPB(2021)·36 citations

Affiliations

first authorsco-authorsvia INSPIRE