Nuclear Theory·nucl-th

Thursday·December 12, 2019

16 papers—6 primary·10 cross-listed

07
[Submitted on 6 Dec 2019] (cross-list from physics.ins-det)
Monte Carlo simulations of the S-shaped neutron guide
Luiz P. de Oliveira · Alexandre P.S. Souza · Fabiano Yokaichiya · Frederico A. Genezini · Margareth K.K.D. Franco
Neutron transport along guides is governed by the Liouville theorem and the technology involved has advanced in recent decades. Computer simulations have proven to be useful tools in the design and conception of neutron guide systems in facilities. In this study, we use a Monte Carlo method to perform simulations for an S-shaped neutron guide with different dimensions for a Small-Angle Neutron Scattering (SANS) instrument, through the MCSTAS software. A wavelength cutoff is observed and shown to be dependent on the geometrical parameters of the guide. Results for the neutron flux at sample position are presented and a greater sensitivity of cutoffs concerning the curvatures of the guides than to their lengths is noticed. Our results are in agreement with those obtained from the Acceptance Diagram method and we analyze the beam divergence behavior along the S-shaped guide.
Comments:
15 pages, 10 figures, Accepted in Journal of Instrumentation
Subjects:
Instrumentation and Detectors (physics.ins-det); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1912.03081 [pdf]
JINST(2020)·2 citations
08
[Submitted on 9 Dec 2019] (cross-list from hep-ph)
Hyperon resonances and meson-baryon interactions in isospin 1
K. P. Khemchandani🇧🇷 · A. Martinez Torres🇧🇷 · J. A. Oller🇪🇸
In this work we extend our formalism to study meson-baryon interactions by including $s$ - and $u$ -channel diagrams for pseudoscalar-baryon systems. We study the coupled systems with strangeness $- 1$ and focus on studying the isospin-1 resonance(s), especially in the energy region around 1400 MeV. By constraining the model parameters to fit the cross section data available on several processes involving relevant channels, we find resonances in the isoscalar as well as the isovector sector in the energy region around 1400 MeV.
Comments:
Contribution to the Hadron 2019 conference proceedings
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1912.04329 [pdf]
1 citation
09
[Submitted on 10 Dec 2019] (cross-list from hep-lat)
Renormalization of a Contact Interaction on a Lattice
Christopher Körber🇺🇸 · Evan Berkowitz🇩🇪 · Thomas Luu🇩🇪
Contact interactions can be used to describe a system of particles at unitarity, contribute to the leading part of nuclear interactions and are numerically non-trivial because they require a proper regularization and renormalization scheme. We explain how to tune the coefficient of a contact interaction between non-relativistic particles on a discretized space in 1, 2, and 3 spatial dimensions such that we can remove all discretization artifacts. By taking advantage of a latticized Lüscher zeta function, we can achieve a momentum-independent scattering amplitude at any finite lattice spacing.
Comments:
Data & code provided at https://github.com/ckoerber/luescher-nd (release v1.0.0). Upload v2 added references
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
arXiv:
1912.04425 [pdf]
7 citations
10
[Submitted on 10 Dec 2019] (cross-list from hep-ph)
Towards a full solution of relativistic Boltzmann equation for quark-gluon matter on GPUs
Jun-Jie Zhang🇨🇳 · Hong-Zhong Wu🇨🇳 · Shi Pu🇨🇳 · Guang-You Qin🇨🇳 · Qun Wang🇨🇳
We have developed a numerical framework for a full solution of the relativistic Boltzmann equations for the quark-gluon matter using the multiple Graphics Processing Units (GPUs) on distributed clusters. Including all the $2 \to 2$ scattering processes of 3-flavor quarks and gluons, we compute the time evolution of distribution functions in both coordinate and momentum spaces for the cases of pure gluons, quarks and the mixture of quarks and gluons. By introducing a symmetrical sampling method on GPUs which ensures the particle number conservation, our framework is able to perform the space-time evolution of quark-gluon system towards thermal equilibrium with high performance. We also observe that the gluons naturally accumulate in the soft region at the early time, which may indicate the gluon condensation.
Comments:
32 pages, 12 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
arXiv:
1912.04457 [pdf]
PRD(2020)·11 citations
11
[Submitted on 10 Dec 2019] (cross-list from hep-ph)
Dynamic Structure of Hadrons in ChPT
A. Aleksejevs🇨🇦 · S. Barkanova
The Chiral Perturbation Theory (ChPT) has been very successful in describing low-energy hadronic properties in the non-perturbative regime of Quantum Chromodynamics. The results of ChPT, many of which are currently under active experimental investigation, provide stringent predictions of many fundamental properties of hadrons, including quantities such as electromagnetic polarizabilities. The paper outlines our semi-automated calculations in ChPT, the corresponding results for the electric and magnetic polarizabilities of the proton and our predictions for Compton differential cross sections.
Comments:
Lepton Photon 2019
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1912.04767 [pdf]
PoS(2019)·0 citations
12
[Submitted on 10 Dec 2019] (cross-list from hep-lat)
Constraining the QCD phase diagram at finite temperature and density
Owe Philipsen🇩🇪
Neither the chiral limit nor finite baryon density can be simulated directly in lattice QCD, which severely limits our understanding of the QCD phase diagram. In this review I collect results for the phase structure in an extended parameter space of QCD, with varying numbers of flavours, quark masses, colours, lattice spacings, imaginary and isospin chemical potentials. Such studies help in understanding the underlying symmetries and degrees of freedom, and are beginning to provide a consistent picture constraining the possibilities for the physical phase diagram.
Comments:
20 pages,15 figures; Plenary talk given at the 37th International Symposium on Lattice Field Theory-Lattice 2019, 16-22 June 2019, Wuhan, China
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1912.04827 [pdf]
PoS(2019)·60 citations
13
[Submitted on 10 Dec 2019] (cross-list from hep-ph)
Radiative contribution to $p_{⊥}$ -broadening of fast partons in a quark-gluon plasma
B.G. Zakharov🇷🇺
The contribution of radiative processes to $p_{⊥}$ -broadening of fast partons in a quark-gluon plasma is investigated. Calculations are performed beyond the soft gluon approximation. It is shown that the radiative correction to $⟨ p_{⊥}^{2} ⟩$ for conditions of heavy ion collisions at RHIC and LHC is negative and can be comparable in absolute value with the nonradiative contribution. This prediction differs radically from the essentially positive contribution of radiative processes to $p_{⊥}$ -broadening, which was predicted earlier in the literature.
Comments:
24 pages, 2 figures. Published in the jubilee issue of JETP devoted to the centenary of Academician I.M. Khalatnikov
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1912.04875 [pdf]
J.Exp.Theor.Phys.(2019)·6 citations
14
[Submitted on 10 Dec 2019] (cross-list from hep-ph)
Chemical freeze-out conditions from net-kaon fluctuations at RHIC
Jamie M. Stafford🇺🇸
We compare the mean-over-variance ratio of the net-kaon distribution calculated within a state-of-the-art hadron resonance gas model to the latest experimental data from the Beam Energy Scan at RHIC by the STAR collaboration. Our analysis indicates that it is not possible to reproduce the experimental results using the freeze-out parameters from the existing combined fit of net-proton and net-electric charge mean-over-variance. The strange mesons need about 10-15 MeV higher temperatures than the light hadrons at the highest collision energies. In view of the recent lambda fluctuation measurements, we predict the net-lambda variance-over-mean at the light and strange chemical freeze-out parameters. We observe that the lambda fluctuations are sensitive to the difference in the freeze-out temperatures established in this analysis. Our results have implications for other phenomenological models in the field of relativistic heavy-ion collisions.
Comments:
5 pages, 3 figures, contribution to the proceedings of the FAIR next generation scientists workshop (FAIRNESS), 6th edition, 20-24 May 2019, Arenzano, Italy
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1912.04928 [pdf]
J.Phys.Conf.Ser.(2020)·0 citations
15
[Submitted on 11 Dec 2019] (cross-list from hep-ph)
Effect of color reconnection on forward-backward multiplicity and mean transverse momentum correlation
Sourav Kundu🇮🇳 · Bedangadas Mohanty🇮🇳 · Dukhishyam Mallick🇮🇳
Color reconnection (CR) mechanism in PYTHIA model has been reported to be essential to describe the flow-like collective effect observed in high multiplicity $p$ + $p$ and $p$ +Pb collisions. In this work, we test this mechanism towards explaining the Forward-Backward multiplicity correlation (b $_{cor}$ ) measurements in $p$ + $p$ collisions at the LHC energies. Out of the three different CR schemes implemented in PYTHIA, (a) MPI based CR (default mechanism), (b) QCD based CR and (c) Gluon moved CR, we found that the QCD based CR scheme describes relatively better the ALICE measurements of b $_{cor}$ in $p$ + $p$ collisions at $s$ = 0.9 and 7 TeV. In addition, we have tuned the parameters of the default CR mechanism in PYTHIA to describe simultaneously the measured charged particle multiplicity pseudo-rapidity ( $η$ ) distribution and b $_{cor}$ . We found that an average number of multipartonic interactions ( $⟨ N_{MPI} ⟩$ ) between 2.5 to 3 and CR range between 0.9 to 2.5 best describes the experimental data. Finally, we have presented a study using PYTHIA events for $p$ + $p$ collisions at $s$ = 7 TeV which shows that the strength of Forward-Backward mean transverse momentum correlation (b $_{cor}^{⟨ p_{T} ⟩ ⟨ p_{T} ⟩}$ ) is found to increase with CR in contrast to decrease of b $_{cor}$ values with CR effect. Hence, simultaneously studying the b $_{cor}^{⟨ p_{T} ⟩ ⟨ p_{T} ⟩}$ and b $_{cor}$ in the experiments will help in establishing the arguments either in favour or in disfavour of CR effect in the measurements.
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1912.05176 [pdf]
8 citations
16
[Submitted on 11 Dec 2019] (cross-list from cond-mat.quant-gas)
Nontrivially Topological Phase Structure of Ideal Bose Gas System within Different Boundary Conditions
Yonghui Xia · Hongtao Feng · Hongshi Zong
The phase structure of ideal Bose gas system within different boundary conditions, i.e., the periodic boundary condition and Dirichlet boundary condition in this work, in an infinite volume, is investigated. It is found that the ground states of ideal Bose gas within those two boundary conditions are both topologically nontrivial, which can not be classified by the traditional symmetry breaking theory. The ground states are different topological phases corresponding to those two boundary conditions, which can be distinguished by the off--diagonal particle number susceptibility. Moreover, this result is universal. The boundary condition may play an important role in pining the critical endpoint of QCD diagram on the approach of the lattice simulations and the computation of some solvable statistical models .
Comments:
I found some mistakes in this version manuscript
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
1912.05218 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE