Nuclear Theory·nucl-th

Tuesday·January 26, 2021

12 papers—4 primary·8 cross-listed

05
Chirality imbalance and chiral magnetic effect under a parallel electromagnetic field
Hayato Aoi🇯🇵 · Katsuhiko Suzuki🇯🇵
We study the time evolution of the chirality imbalance $n_{5}$ and the chiral magnetic effect (CME) under the external parallel electromagnetic fields without assuming the artificial chiral asymmetric source. We adopt the time-dependent Sauter-type electric and constant magnetic field, and obtain analytical solutions of the Dirac equation for a massive fermion. We use the point-split regularization to calculate the vacuum contribution in the gauge invariant way. As a result, we find that $n_{5}$ and CME current increase substantially as the electric field increases, and stay finite after the electric field is switched off. The chirality imbalance and CME current are shown to consist of a dominant contribution, which is essentially proportional to relativistic velocity, and a small oscillating part. We find a simple analytical relation between $n_{5}$ and the fermion pair-production rate from the vacuum. We also discuss dynamical origin of the chirality imbalance in detail.
↳ hep-phnucl-thPRD(2021)·5 citations
06
Novel pentaquark picture for singly heavy baryons from chiral symmetry
Daiki Suenaga🇯🇵 · Atsushi Hosaka🇯🇵
We propose a new type of structure for singly heavy baryons of $Qq q q ˉ q$ in addition to the conventional one of $Qq q$ . Based on chiral symmetry of the light quarks, we show that the $Qq q q ˉ q$ baryon offers a novel picture for heavy quark spin-singlet and flavor-antisymmetric baryons. By making use of the effective Lagrangian approach, we find $Λ_{c} (2765)$ and $Ξ_{c} (2967)$ are mostly $Qq q q ˉ q$ while $Λ_{c} (2286)$ and $Ξ_{c} (2470)$ are mostly $Qq q$ . The masses of negative-parity baryons are predicted. We also derive a sum rule and the extended Goldberger-Treiman relation that the masses of the baryons satisfy. Furthermore, a mass degeneracy of parity partners of the baryons with the restoration of chiral symmetry is discussed. These are the unique features that the conventional picture of radial excitation in the quark model does not accommodate. Our findings provide useful information not only for future experiments but also for future lattice simulations on diquarks.
↳ hep-phnucl-thPRD(2021)·22 citations
07
Hydrodynamic fluctuations and long-time tails in a fluid on an anisotropic background
Ashish Shukla🇨🇦
The effective low-energy late-time description of many body systems near thermal equilibrium provided by classical hydrodynamics in terms of dissipative transport phenomena receives important corrections once the effects of stochastic fluctuations are taken into account. One such physical effect is the occurrence of long-time power law tails in correlation functions of conserved currents. In the hydrodynamic regime $k \to 0$ this amounts to non-analytic dependence of the correlation functions on the frequency $ω$ . In this article, we consider a relativistic fluid with a conserved global $U (1)$ charge in the presence of a strong background magnetic field, and compute the long-time tails in correlation functions of the stress tensor. The presence of the magnetic field renders the system anisotropic. In the absence of the magnetic field, there are three out-of-equilibrium transport parameters that arise at the first order in the hydrodynamic derivative expansion, all of which are dissipative. In the presence of a background magnetic field, there are ten independent out-of-equilibrium transport parameters at the first order, three of which are non-dissipative and the rest are dissipative. We provide the most general linearized equations about a given state of thermal equilibrium involving the various transport parameters in the presence of a magnetic field, and use them to compute the long-time tails for the fluid.
↳ hep-thcond-mat.str-elhep-phnucl-th+1NPB(2021)·6 citations
08
Application of the Uniformized Mittag-Leffler Expansion to $Λ (1405)$
Wren Yamada🇯🇵 · Osamu Morimatsu🇯🇵
We study the pole properties of $Λ (1405)$ in a model-independent manner by applying the Uniformized Mittag-Leffler expansion proposed in our previous paper. The resonant energy, width and residues are determined by expanding the observable as a sum of resonant-pole pairs under an appropriate parameterization which expresses the observable to be single-valued, and fitting it to experimental data of the invariant-mass distribution of $π^{+} Σ^{-}$ , $π^{-} Σ^{+}$ , $π^{0} Σ^{0}$ final states in the reaction, $γ p \to K^{+} π Σ$ , and the elastic and inelastic cross section, $K^{-} p \to K^{-} p$ , $K ˉ^{0} n$ , $π^{+} Σ^{-}$ , $π^{-} Σ^{+}$ . As we gradually increase the number of pairs from one to three, the first pair converges while the second and third pairs emerge further and further away from the first pair, implying that the Uniformized Mittag-Leffler expansion with three pairs is almost convergent in the vicinity of the $Λ (1405)$ . The broad peak structure between the $π Σ$ and $K ˉ N$ thresholds regarded to be $Λ (1405)$ is explained by a single pair with a resonant energy of 1420 $\pm$ 1 MeV, and a half width of 48 $\pm$ 2 MeV, which is consistent with the single-pole picture of $Λ (1405)$ . We conclude that the Uniformized Mittag-Leffler expansion turns out to be a very powerful method to obtain resonance energy, width and residues from the near-threshold spectrum.
↳ hep-phhep-exnucl-thPRC(2021)·13 citations
09
Double-strangeness production in $Λ p \to K^{+} X$ reaction
Jung Keun Ahn🇰🇷 · Seung-il Nam🇰🇷
We investigate $S = - 2$ production from the $Λ p \to K^{+} X$ reactions within the effective Lagrangian approach. The $Λ p \to K^{+} ΛΛ$ and $Λ p \to K^{+} Ξ^{-} p$ reactions are considered to find the lightest $S = - 2$ system, which is $H$ -dibaryon. We assume that the $H (2250) \to ΛΛ$ , and $H (2270) \to Ξ^{-} p$ decays with the intrinsic decay width of 1 MeV. According to our calculations, the total cross-sections for $Λ p \to K^{+} ΛΛ$ and $Λ p \to K^{+} Ξ^{-} p$ reactions were found to be of the order of a few $μ$ b in the $Λ$ beam momentum range of up to 5 GeV $/ c$ . Furthermore, the direct access of information regarding the interference patterns between the $H$ -dibaryon and non-resonant contributions was demonstrated.
↳ hep-phhep-exnucl-exnucl-thPRD(2021)·8 citations
10
Neutronics Analysis for MSR Cell with Different Fuel Salt Channel Geometry
Shihe Yu · Yafen Liu · Pu Yang · Ruimin Ji · Guifeng Zhu Bo Zhou · Xuzhong Kang · Rui Yan · Yang Zou · Ye Dai
The neutronic properties of Molten Salt Reactor are different from that of traditional solid-fuel reactors due to its nuclear fuel particularity. Based upon MCNP code, the influence of the size and shape of fuel salt channel on neutron physics of MSR cell was studied systematically in this work. The results show that the infinite multiplication factors increases first and then decreases with the change of graphite cell size under the condition of given fuel volume fraction. In the case of the same FVF and average chord length, when the average chord length is relatively small, the k values with different fuel salt channel shapes are in good agreement; when the average chord length is relatively large, the k values with different fuel salt channel shapes are greatly different. In addition, some examples of practical application of this work are illustrated in the end, including cell selection for the core and thermal expansion displacement analysis of the cell.
↳ physics.app-phnucl-thNucl.Sci.Tech.(2021)·0 citations
11
CASCADE3 A Monte Carlo event generator based on TMDs
S. Baranov🇷🇺 · A. Bermudez Martinez🇩🇪 · L.I. Estevez Banos🇩🇪 · F. Guzman🇨🇺 · F. Hautmann🇧🇪 · H. Jung🇩🇪 · A. Lelek🇧🇪 · J. Lidrych🇩🇪 · A. Lipatov🇷🇺 · M. Malyshev🇷🇺 · M. Mendizabal🇩🇪 · S. Taheri Monfared🇩🇪 and 3 other authors
The CASCADE3 Monte Carlo event generator based on Transverse Momentum Dependent (TMD) parton densities is described. Hard processes which are generated in collinear factorization with LO multileg or NLO parton level generators are extended by adding transverse momenta to the initial partons according to TMD densities and applying dedicated TMD parton showers and hadronization. Processes with off-shell kinematics within $k_{t}$ -factorization, either internally implemented or from external packages via LHE files, can be processed for parton showering and hadronization. The initial state parton shower is tied to the TMD parton distribution, with all parameters fixed by the TMD distribution.
↳ hep-phnucl-thEPJC(2021)·114 citations
12
A Trailhead for Quantum Simulation of SU(3) Yang-Mills Lattice Gauge Theory in the Local Multiplet Basis
Anthony Ciavarella🇺🇸 · Natalie Klco🇺🇸 · Martin J. Savage🇺🇸
Maintaining local interactions in the quantum simulation of gauge field theories relegates most states in the Hilbert space to be unphysical -- theoretically benign, but experimentally difficult to avoid. Reformulations of the gauge fields can modify the ratio of physical to gauge-variant states often through classically preprocessing the Hilbert space and modifying the representation of the field on qubit degrees of freedom. This paper considers the implications of representing SU(3) Yang-Mills gauge theory on a lattice of irreducible representations in both a global basis of projected global quantum numbers and a local basis in which controlled-plaquette operators support efficient time evolution. Classically integrating over the internal gauge space at each vertex (e.g., color isospin and color hypercharge) significantly reduces both the qubit requirements and the dimensionality of the unphysical Hilbert space. Initiating tuning procedures that may inform future calculations at scale, the time evolution of one- and two-plaquettes are implemented on one of IBM's superconducting quantum devices, and early benchmark quantities are identified. The potential advantages of qudit environments, with either constrained 2D hexagonal or 1D nearest-neighbor internal state connectivity, are discussed for future large-scale calculations.
↳ quant-phhep-lathep-phnucl-thPRD(2021)·288 citations

Affiliations

first authorsco-authorsvia INSPIRE