Nuclear Theory·nucl-th

Friday·September 2, 2022

7 papers—3 primary·4 cross-listed

01
Variational Monte Carlo Calculations of n+3H Scattering
Abraham R. Flores · Kenneth M. Nollett
A paramount goal in the field of nuclear physics is to unify ab-initio treatments of bound and unbound states. The position-space quantum Monte Carlo (QMC) methods have a long history of successful bound state calculations in light systems but so far have seen very little application to unbound systems. Here we introduce a numerical method to improve the efficiency and accuracy of unbound-state calculations in QMC, and as an initial application we compute scattering observables for the neutron-triton system using variational Monte Carlo (VMC) wave functions. The method consists of inferring long-range amplitudes in the wave function from integrals over the short-ranged region where all the particles interact. This approach using integral relations is well established in the literature; here we develop it for the QMC framework. We validate our code with a consistency check between short-range spectroscopic overlap functions computed from direct evaluation and from the integral relations; scattering amplitudes are long-range asymptotics of those overlaps. Comparison against published benchmark calculations using the same potential demonstrates that the integral method, when applied to the current VMC wave functions, produces more accurate scattering observables than direct evaluation from the same variational wave function. However, it still differs noticeably from exact results. We then present phase shifts and mixing parameters for the neutron-triton system using various interactions. Application of the integral method here paves the way for its use in Green's function Monte Carlo (GFMC) calculations. In GFMC the wave functions are more precise, but high-precision convergence of their tails is slow, and there are additional difficulties in reading out amplitudes. The integral methods will address both of those remaining problems.
nucl-thPRC(2023)·15 citations
02
Imprints of clustering in multiplicity fluctuations
A. Bazgir🇵🇱 · V.Z. Reyna Ortiz🇵🇱 · M. Rybczynski🇵🇱 · U. Shah🇵🇱 · Z. Wlodarczyk🇵🇱
In this paper, we investigate the multiplicity fluctuations of charged particles observed in high-energy nuclear collisions and relate them to the size of hadronizing systems which happen during such processes. We use the average multiplicities $⟨ N ⟩$ and variances $V a r (N)$ of multiplicity distributions of charged particles produced in centrality selected collisions of relativistic heavy-ion nuclei to evaluate the dynamic variable $Ω$ and study its dependence on the size of colliding nuclei. We connect the observed system-size dependence of multiplicity fluctuations with the clustering phenomena and the finiteness of the hadronizing sources and the thermal bath.
nucl-thhep-phEPJA(2023)·0 citations
03
Directed flow in relativistic resistive magneto-hydrodynamic expansion for symmetric and asymmetric collision systems
Kouki Nakamura🇯🇵 · Takahiro Miyoshi🇯🇵 · Chiho Nonaka🇯🇵 · Hiroyuki R. Takahashi🇯🇵
We construct a dynamical model for high-energy heavy-ion collision based on the relativistic resistive magneto-hydrodynamic framework. Using our newly developed (3+1)-dimensional relativistic resistive magneto-hydrodynamics code, we investigate magneto-hydrodynamic expansion in symmetric and asymmetric collision systems as a first application to high-energy heavy-ion collisions. As a realistic initial condition for electromagnetic fields, we consider the solutions of the Maxwell equations with the source term of point charged particles moving in the direction of the beam axis, including finite constant electrical conductivity of the medium. We evaluate the directed flow in the symmetric and asymmetric collisions at RHIC energy. We find a significant effect of finite electrical conductivity on the directed flow in the asymmetric collision system. We confirm that a certain amount of energy transfer by dissipation associated with Ohmic conduction occurs in the asymmetric collision system because of asymmetry of the electric field produced by two different colliding nuclei. Because this energy transfer makes the pressure gradient of the medium flatter, the growth of directed flow decreases.
nucl-thhep-phnucl-exPRC(2023)·18 citations
04
SQM2022: Theoretical Summary
Berndt Müller🇺🇸
Written version of the theoretical summary lecture presented at the Strangeness in Quark Matter 2022 conference.
↳ hep-phnucl-thEPJ Web Conf.(2023)·2 citations
05
Qubitization strategies for bosonic field theories
Andrei Alexandru🇺🇸 · Paulo F. Bedaque🇺🇸 · Andrea Carosso🇺🇸 · Michael J. Cervia🇺🇸 · Andy Sheng🇺🇸
Quantum simulations of bosonic field theories require a truncation in field space to map the theory onto finite quantum registers. Ideally, the truncated theory preserves the symmetries of the original model and has a critical point in the same universality class. In this paper, we explore two different truncations that preserve the symmetries of the 1+1-dimensional $O (3)$ non-linear $σ$ -model - one that truncates the Hilbert space for the unit sphere by setting an angular momentum cutoff and a fuzzy sphere truncation inspired by non-commutative geometry. We compare the spectrum of the truncated theories in a finite box with the full theory. We use open boundary conditions, a novel method that improves on the correlation lengths accessible in our calculations. We provide evidence that the angular-momentum truncation fails to reproduce the $σ$ -model and that the anti-ferromagnetic fuzzy model agrees with the full theory.
↳ hep-lathep-thnucl-thquant-phPRD(2023)·21 citations
06
Amplitude/Operator Basis in Chiral Perturbation Theory
Ian Low🇺🇸 · Jing Shu🇨🇳 · Ming-Lei Xiao🇺🇸 · Yu-Hui Zheng🇨🇳
We establish a systematic construction of the on-shell amplitude/operator basis for Chiral Perturbation Theory (ChPT) in $D = 4$ spacetime dimensions and with an arbitrary number of flavors $N_{f}$ . For kinematic factors, we employ spinor-helicity variables to construct the soft blocks, which are local amplitudes satisfying the Adler's zero condition, as well as to take into account the reduction in the kinematic basis due to the Gram determinant, which arises at $O (p^{10})$ when the number of multiplicity $N$ in an amplitude becomes large: $N > D$ . For flavor factors, we include group-theoretic relations at small $N_{f}$ , $N_{f} \leq N$ , which decreases the flavor basis. The result is obtained by adapting the Young tensor method of constructing the operator basis for generic effective field theories to the case of non-linearly realized symmetries. Working in the massless quark limit, we present purely mesonic operators for both even- and odd-parity at $O (p^{6})$ and $O (p^{8})$ for $N = 6$ and arbitrary $N_{f}$ , and establish a direct correspondence between the amplitude basis and the operator basis. Furthermore, the redundancy due to the Gram determinant is studied at $O (p^{10})$ for $N = 6, 8$ and 10.
↳ hep-phhep-thnucl-thJHEP(2023)·17 citations
07
Longitudinal momentum fraction of heavy-flavor mesons in jets in high-energy nuclear collisions
Yao Li🇨🇳 · Sa Wang🇨🇳 · Ben-Wei Zhang🇨🇳
Heavy-flavor jets are powerful tools to gain insight into the in-medium partonic energy-loss mechanisms and the quark-gluon plasma's (QGP) transport properties in high-energy nuclear collisions. In this work we present the first theoretical study of the longitudinal momentum fraction $z_{∣∣}$ carried by heavy-flavor mesons in jets in Pb+Pb collisions at $s_{NN}$ = 5.02 TeV. The p+p baseline is provided by POWHEG+PYTHIA8, which matches the next-to-leading-order hard processes with the parton shower. We employ a Monte Carlo transport model, which considers the collisional and radiative partonic energy loss, to simulate the evolution of heavy-flavor jets in the expanding QGP medium. We observe steeper $z_{∣∣}$ distributions of $B^{0}$ jets compared to those of $D^{0}$ jets at the same kinematics region in p+p collisions, which may be a hint of the harder jet fragmentation function of b jets compared to c jets in vacuum. In A+A collisions, it is shown that the jet quenching effect would generally decrease the values of $z_{∣∣}$ . We have made a systematical study on how several factors, including jet $p_{T}$ , jet radius $R$ , and collision centrality, would influence the medium modification of $z_{∣∣}$ distributions of a $D^{0}$ jet. In addition, we predict visibly stronger nuclear modifications of $B^{0}$ -jet $z_{∣∣}$ distributions compared to a $D^{0}$ jet within the same $p_{T}$ windows as a result of the much steeper initial $z_{∣∣}$ distribution of the $B^{0}$ jet in vacuum.
↳ hep-phnucl-thPRC(2023)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE

Variational Monte Carlo Calculations of n+3H Scattering

Imprints of clustering in multiplicity fluctuations

Directed flow in relativistic resistive magneto-hydrodynamic expansion for symmetric and asymmetric collision systems

SQM2022: Theoretical Summary

Qubitization strategies for bosonic field theories

Amplitude/Operator Basis in Chiral Perturbation Theory

Longitudinal momentum fraction of heavy-flavor mesons in jets in high-energy nuclear collisions

Affiliations