Nuclear Theory·nucl-th

Friday·March 19, 2021

13 papers—4 primary·9 cross-listed

05
[Submitted on 17 Mar 2021] (cross-list from astro-ph.HE)
Implications of Lithium to Oxygen AMS-02 spectra on our understanding of cosmic-ray diffusion
Michael Korsmeier🇸🇪 · Alessandro Cuoco🇮🇹
We analyze recent AMS-02 comic-ray measurements of Lithium, Beryllium, Boron, Carbon, Nitrogen and Oxygen. The emphasis of the analysis is on systematic uncertainties related to propagation and nuclear cross sections. To investigate the uncertainties in the propagation scenario, we consider five different frameworks, differing with respect to the inclusion of a diffusion break at a few GV, the presence of reacceleration, and the presence of a break in the injection spectra of primaries. For each framework we fit the diffusion equations of cosmic rays and explore the parameter space with Monte Carlo methods. At the same time, the impact of the uncertainties in the nuclear production cross sections of secondaries is explicitly considered and included in the fit through the use of nuisance parameters. We find that all the considered frameworks are able to provide a good fit. In particular, two competing scenarios, one including a break in diffusion but no reacceleration and the other with reacceleration but no break in diffusion are both allowed. The inclusion of cross-section uncertainties is, however, crucial, to this result. Thus, at the moment, these uncertainties represent a fundamental systematic preventing a deeper understanding of the properties of CR propagation. We find, nonetheless, that the slope of diffusion at intermediate rigidities is robustly constrained in the range $δ ≃ 0.45 - 0.5$ in models without convection, or $δ ≃ 0.4 - 0.5$ if convection is included in the fit. Furthermore, we find that the use of the AMS-02 Beryllium data provides a lower limit on the vertical size of the Galactic propagation halo of $z_{h} ≳ 3$ kpc.
Comments:
26 pages, 11 figures; v2: updated to the published version, results are unchanged
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2103.09824 [pdf]
PRD(2021)·63 citations
06
[Submitted on 17 Mar 2021] (cross-list from hep-ph)
On the transition form factors of the axial-vector resonance $f_{1} (1285)$ and its decay into $e^{+} e^{-}$
Marvin Zanke🇩🇪 · Martin Hoferichter🇨🇭 · Bastian Kubis🇩🇪
Estimating the contribution from axial-vector intermediate states to hadronic light-by-light scattering requires input on their transition form factors (TFFs). Due to the Landau-Yang theorem, any experiment sensitive to these TFFs needs to involve at least one virtual photon, which complicates their measurement. Phenomenologically, the situation is best for the $f_{1} (1285)$ resonance, for which information is available from $e^{+} e^{-} \to e^{+} e^{-} f_{1}$ , $f_{1} \to 4 π$ , $f_{1} \to ρ γ$ , $f_{1} \to ϕ γ$ , and $f_{1} \to e^{+} e^{-}$ . We provide a comprehensive analysis of the $f_{1}$ TFFs in the framework of vector meson dominance, including short-distance constraints, to determine to which extent the three independent TFFs can be constrained from the available experimental input, a prerequisite for improved calculations of the axial-vector contribution to hadronic light-by-light scattering. In particular, we focus on the process $f_{1} \to e^{+} e^{-}$ , evidence for which has been reported recently by SND for the first time, and discuss the impact that future improved measurements will have on the determination of the $f_{1}$ TFFs.
Comments:
60 pages, 14 figures; v2: Appendix D on alternative $f_{1} \to 4 π$ mechanism added, references updated, version published in JHEP
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2103.09829 [pdf]
JHEP(2021)·97 citations
07
[Submitted on 18 Mar 2021] (cross-list from hep-ph)
$N^{*}$ states with hidden charm and a three-body nature
Brenda B. Malabarba🇧🇷 · K. P. Khemchandani🇧🇷 · A. Martinez Torres🇧🇷
In this work we study the formation of $N^{*}$ 's as a consequence of the dynamics involved in the $N D D ˉ^{*} - N D ˉ D^{*}$ system when the $D D ˉ^{*} - D ˉ D^{*}$ subsystem generates $X (3872)$ in isospin 0 and $Z_{c} (3900)$ in isospin 1. States with isospin $I = 1/2$ and mass in the energy region $4400 - 4600$ MeV are found to arise with spin-parity $J^{P} = 1/ 2^{+}$ and $3/ 2^{+}$ , leading to predictions in this way of the existence of $N^{*}$ resonances with hidden charm and a three-body nature. We also discuss the possibility of the existence of $Δ_{c}$ states, i.e., $Δ$ 's with hidden charm.
Comments:
Published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2103.09978 [pdf]
EPJA(2022)·13 citations
08
[Submitted on 18 Mar 2021] (cross-list from hep-ph)
Light-front holography with chiral symmetry breaking
Yang Li🇨🇳 · James P. Vary🇺🇸
We present an analytically solvable 3D light-front Hamiltonian model for hadrons that extends light-front holography by including finite mass quarks and a longitudinal confinement term. We propose that the model is suitable as an improved analytic approximation to QCD at a low resolution scale. We demonstrate that it preserves desired Lorentz symmetries and it produces improved agreement with the experimental mass spectroscopy and other properties of the light mesons. Importantly, the model also respects chiral symmetry and the Gell-Mann-Oakes-Renner relation.
Comments:
7 pages, 3 figures, see ancillary for additional information, accepted for publication in Physics Letters B
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2103.09993 [pdf]
PLB(2022)·50 citations
09
[Submitted on 18 Mar 2021] (cross-list from hep-ph)
Relativistic spin sum rules and the role of the pivot
Cédric Lorcé (Ecole Polytechnique, CPHT)🇫🇷
Spin sum rules depend on the choice of a pivot, i.e. the point about which the angular momentun is defined, usually identified with the center of the nucleon. The latter is however not unique in a relativistic theory and has led to apparently contradictory results in the literature. Using the recently developed phase-space approach, we compute for the first time the contribution associated with the motion of the center of the nucleon, and we derive a general spin sum rule which reduces to established results after appropriate choices for the pivot and the spin component.
Comments:
16 pages, 1 figure, 1 table
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2103.10100 [pdf]
EPJC(2021)·24 citations
10
[Submitted on 18 Mar 2021] (cross-list from cond-mat.quant-gas)
Microscopic derivation of the Boltzmann equation for transport coefficients of resonating fermions at high temperature
Keisuke Fujii🇯🇵 · Yusuke Nishida🇯🇵
Motivated by the recently observed failure of the kinetic theory for the bulk viscosity, we in turn revisit the shear viscosity and the thermal conductivity of two-component fermions with a zero-range interaction both in two and three dimensions. In particular, we show that their Kubo formula evaluated exactly in the high-temperature limit to the lowest order in fugacity is reduced to the linearized Boltzmann equation. Previously, such a microscopic derivation of the latter was achieved only incompletely corresponding to the relaxation-time approximation. Here, we complete it by resuming all contributions that are naively higher orders in fugacity but become comparable in the zero-frequency limit due to the pinch singularity, leading to a self-consistent equation for a vertex function identical to the linearized Boltzmann equation. We then compute the shear viscosity and the thermal conductivity in the high-temperature limit for an arbitrary scattering length and find that the Prandtl number exhibits a nonmonotonic behavior slightly below the constant value in the relaxation-time approximation.
Comments:
12 pages, 7 figures; (v2) numerical results in Sec $.$ IV corrected; (v3) published version
Subjects:
Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th)
arXiv:
2103.10123 [pdf]
PRA(2021)·5 citations
11
[Submitted on 18 Mar 2021] (cross-list from cond-mat.mes-hall)
Half-integer anomalous currents in 2D materials from a QFT viewpoint
D. Dudal🇧🇪 · F. Matusalem🇧🇷 · A. J. Mizher🇨🇱 · A. R. Rocha🇧🇷 · C. Villavicencio🇨🇱
Charge carriers in Dirac/Weyl semi-metals exhibit a relativistic-like behavior. In this work we propose a novel type of intrinsic half-integer Quantum Hall effect in 2D materials, thereby also offering a topological protection mechanism for the current. Its existence is rooted in the 2D parity anomaly, without any need for a perpendicular magnetic field. We conjecture that it may occur in disturbed honeycomb lattices where both spin degeneracy and time reversal symmetry are broken. These configurations harbor two distinct gap-opening mechanisms that, when occurring simultaneously, drive slightly different gaps in each valley, causing a net anomalous conductivity when the chemical potential is tuned to be between the distinct gaps. Some examples of promising material setups that fulfill the prerequisites of our proposal are also listed to motivate looking for the effect at the numerical and experimental level.
Comments:
12 pages, 6 figures, published version, one figure added
Subjects:
Mesoscale and Nanoscale Physics (cond-mat.mes-hall); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2103.10341 [pdf]
Sci.Rep.(2022)·11 citations
12
[Submitted on 18 Mar 2021] (cross-list from nucl-ex)
Revisit the Chiral Magnetic Effect Expectation in Isobaric Collisions at the Relativistic Heavy Ion Collider
Yicheng Feng🇺🇸 · Yufu Lin🇨🇳 · Jie Zhao🇺🇸 · Fuqiang Wang🇺🇸
Isobaric $_{44}^{96}$ Ru+ $_{44}^{96}$ Ru and $_{40}^{96}$ Zr+ $_{40}^{96}$ Zr collisions at $s_{_{N N}} = 200$ GeV have been conducted at the Relativistic Heavy Ion Collider to circumvent the large flow-induced background in searching for the chiral magnetic effect (CME), predicted by the topological feature of quantum chromodynamics (QCD). Considering that the background in isobar collisions is approximately twice that in Au+Au collisions (due to the smaller multiplicity) and the CME signal is approximately half (due to the weaker magnetic field), we caution that the CME may not be detectable with the collected isobar data statistics, within $\sim$ 2 $σ$ significance, if the axial charge per entropy density ( $n_{5} / s$ ) and the QCD vacuum transition probability are system independent. This expectation is generally verified by the Anomalous-Viscous Fluid Dynamics (AVFD) model. While our estimate provides an approximate "experimental" baseline, theoretical uncertainties on the CME remain large.
Comments:
6 pages, 1 multi-panel figure. v2: version after addressing referee comments. Corrected a factor 2 error in the quoted multiplicity; corrected a factor 2 error in the A-dependence exponent of the magnetic field; conclusions unchanged. v3: match published version
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2103.10378 [pdf]
PLB(2021)·22 citations
13
[Submitted on 18 Mar 2021] (cross-list from hep-ph)
Shear-induced spin polarization in heavy-ion collisions
Baochi Fu🇨🇳 · Shuai Y. F. Liu🇨🇳 · Longgang Pang🇨🇳 · Huichao Song🇨🇳 · Yi Yin🇨🇳
We study the spin polarization generated by the hydrodynamic gradients. In addition to the widely studied thermal vorticity effects, we identify an undiscovered contribution from the fluid shear. This shear-induced polarization (SIP) can be viewed as the fluid analog of strain-induced polarization observed in elastic and nematic materials. We obtain the explicit expression for SIP using the quantum kinetic equation and linear response theory. Based on a realistic hydrodynamic model, we compute the differential spin polarization along both the beam direction $z^$ and the out-plane direction $y^$ in non-central heavy-ion collisions at $s_{N N} = 200$ GeV, including both SIP and thermal vorticity effects. We find that SIP contribution always shows the same azimuthal angle dependence as experimental data and competes with thermal vorticity effects. In the scenario that $Λ$ inherits and memorizes the spin polarization of strange quark, SIP wins the competition, and the resulting azimuthal angle dependent spin polarization $P_{y}$ and $P_{z}$ agrees qualitatively with the experimental data.
Comments:
6 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2103.10403 [pdf]
PRL(2021)·238 citations

Affiliations

first authorsco-authorsvia INSPIRE