Nuclear Theory·nucl-th

Thursday·July 9, 2020

12 papers—5 primary·7 cross-listed

06
Lattice QCD evaluation of the Compton amplitude employing the Feynman-Hellmann theorem
K. U. Can🇦🇺 · A. Hannaford-Gunn🇦🇺 · R. Horsley🇬🇧 · Y. Nakamura🇯🇵 · H. Perlt🇩🇪 · P. E. L. Rakow🇬🇧 · G. Schierholz🇩🇪 · K. Y. Somfleth🇦🇺 · H. Stüben🇩🇪 · R. D. Young🇦🇺 · J. M. Zanotti🇦🇺
The forward Compton amplitude describes the process of virtual photon scattering from a hadron and provides an essential ingredient for the understanding of hadron structure. As a physical amplitude, the Compton tensor naturally includes all target mass corrections and higher twist effects at a fixed virtuality, $Q^{2}$ . By making use of the second-order Feynman-Hellmann theorem, the nucleon Compton tensor is calculated in lattice QCD at an unphysical quark mass across a range of photon momenta $3 ≲ Q^{2} ≲ 7$ GeV $^{2}$ . This allows for the $Q^{2}$ dependence of the low moments of the nucleon structure functions to be studied in a lattice calculation for the first time. The results demonstrate that a systematic investigation of power corrections and the approach to parton asymptotics is now within reach.
↳ hep-lathep-phhep-thnucl-thPRD(2020)·57 citations
07
Spectral functions and dynamic critical behavior of relativistic $Z_{2}$ theories
Dominik Schweitzer🇩🇪 · Sören Schlichting🇩🇪 · Lorenz von Smekal🇩🇪
We investigate the dynamic critical behaviour of a relativistic scalar field theory with $Z_{2}$ symmetry by calculating spectral functions of the order parameter at zero and non-vanishing momenta from first-principles classical-statistical lattice simulations in real-time. We find that at temperatures above the critical point $(T > T_{c})$ , the spectral functions are well described by relativistic quasi-particle peaks. Close to the transition temperature $(T \sim T_{c})$ , we observe strong infrared contributions building up. In the ordered phase at low temperatures $(T < T_{c})$ , in addition to the quasi-particle peak, we observe a soft mode with a dispersion relation indicative of collective excitations. Investigating the spectral functions close to $T_{c}$ , we demonstrate that the behavior in the vicinity of the critical point is controlled by dynamic scaling functions and the dynamic critical exponent $z$ , which we determine from our simulations. By considering the equations of motion for a closed system and a system coupled to a heat bath, we extract the dynamic critical behavior for two different dynamic universality classes (Models A & C) in two and three spatial dimensions.
↳ hep-latcond-mat.stat-mechhep-phnucl-thNPB(2020)·35 citations
08
Correlated Energy Uncertainties in Reaction Rate Calculations
Richard Longland🇺🇸 · Nicolas de Séréville🇫🇷
Context. Monte Carlo methods can be used to evaluate the uncertainty of a reaction rate that arises from many uncertain nuclear inputs. However, until now no attempt has been made to find the effect of correlated energy uncertainties in input resonance parameters. Aims. To investigate the impact of correlated energy uncertainties on reaction rates. Methods. Using a combination of numerical and Monte Carlo variation of resonance energies, the effect of correlations are investigated. Five reactions are considered: two fictional, illustrative cases and three reactions whose rates are of current interest. Results. The effect of correlations in resonance energies depends on the specific reaction cross section and temperatures considered. When several resonances contribute equally to a reaction rate, and are located either side of the Gamow peak, correlations between their energies dilute their effect on reaction rate uncertainties. If they are both located above or below the maximum of the Gamow peak, however, correlations between their resonance energies can increase the reaction rate uncertainties. This effect can be hard to predict for complex reactions with wide and narrow resonances contributing to the reaction rate.
↳ astro-ph.IMnucl-thAstron.Astrophys.(2020)·2 citations
09
Cumulants of multiple conserved charges and global conservation laws
Volodymyr Vovchenko🇺🇸 · Roman V. Poberezhnyuk🇺🇦 · Volker Koch🇺🇸
We analyze the behavior of cumulants of conserved charges in a subvolume of a thermal system with exact global conservation laws by extending a recently developed subensemble acceptance method (SAM) [V. Vovchenko et al., arXiv:2003.13905] to multiple conserved charges. Explicit expressions for all diagonal and off-diagonal cumulants up to sixth order that relate them to the grand canonical susceptibilities are obtained. The derivation is presented for an arbitrary equation of state with an arbitrary number of different conserved charges. The global conservation effects cancel out in any ratio of two second order cumulants, in any ratio of two third order cumulants, as well as in a ratio of strongly intensive measures $Σ$ and $Δ$ involving any two conserved charges, making all these quantities particularly suitable for theory-to-experiment comparisons in heavy-ion collisions. We also show that the same cancellation occurs in correlators of a conserved charge, like the electric charge, with any non-conserved quantity such as net proton or net kaon number. The main results of the SAM are illustrated in the framework of the hadron resonance gas model. We also elucidate how net-proton and net- $Λ$ fluctuations are affected by conservation of electric charge and strangeness in addition to baryon number.
↳ hep-phnucl-exnucl-thJHEP(2020)·53 citations
10
Fireball tomography from bottomonia elliptic flow in relativistic heavy-ion collisions
Partha Pratim Bhaduri🇮🇳 · Mubarak Alqahtani🇸🇦 · Nicolas Borghini🇩🇪 · Amaresh Jaiswal🇮🇳 · Michael Strickland🇺🇸
We calculate the elliptic flow of bottomonia produced in Pb $+$ Pb collisions at $s_{NN} = 5.02$ TeV. We consider temperature-dependent decay widths for the anisotropic escape of various bottomonium states and observe that the transverse momentum dependence of bottomonia elliptic flow provides a tomographic information about the QGP fireball at different stages of its evolution. For the space-time evolution of the fireball, we employ simulation results from the 3+1D quasiparticle anisotropic hydrodynamic model. We find that our results for transverse momentum dependence of bottomonia elliptic flow are in reasonable agreement with experimental results from the ALICE and CMS collaborations.
↳ hep-phhep-exhep-thnucl-thEPJC(2021)·21 citations
11
Properties of the QCD thermal transition with $N_{f} = 2 + 1$ flavours of Wilson quark
G. Aarts🇬🇧 · C. Allton🇬🇧 · J. Glesaaen🇬🇧 · S. Hands🇬🇧 · B. Jäger🇩🇰 · S. Kim🇰🇷 · M. P. Lombardo🇮🇹 · A. A. Nikolaev🇬🇧 · S. M. Ryan🇮🇪 · J.-I. Skullerud🇮🇪 · L.-K. Wu🇨🇳
We study properties of the thermal transition in QCD, using anisotropic, fixed-scale lattice simulations with $N_{f} = 2 + 1$ flavours of Wilson fermion. Observables are compared for two values of the pion mass, focusing on chiral properties. Results are presented for the Polyakov loop, various susceptibilities, the chiral condensate and its susceptibility, and the onset of parity doubling in the light and strange baryonic sector.
↳ hep-lathep-phnucl-thPRD(2022)·55 citations
12
Deciphering QCD dynamics in small collision systems using event shape and final state multiplicity at the Large Hadron Collider
Suman Deb🇮🇳 · Sushanta Tripathy🇮🇳 · Golam Sarwar🇮🇳 · Raghunath Sahoo🇮🇳 · Jan-e Alam🇮🇳
The high-multiplicity pp collisions at the Large Hadron Collider energies with various heavy-ion-like signatures have warranted a deeper understanding of the underlying physics and particle production mechanisms. It is a common practice to use experimental data on the hadronic transverse momentum ( $p_{T}$ ) spectra to extract thermodynamical properties of the system formed in heavy ion and high multiplicity pp collisions. The non-availability of event topology dependent experimental data for pp collisions at $s$ = 13 TeV on the spectra of non-strange and strange hadrons constrains us to use the PYTHIA8 simulated numbers to extract temperature-like parameters to study the event shape and multiplicity dependence of specific heat capacity, conformal symmetry breaking measure (CSBM) and speed of sound. The observables show a clear dependence on event multiplicity and event topology. Thermodynamics of the system is largely governed by the light particles because of their relatively larger abundances. In this regards, a threshold in the particle production, $N_{ch} ≃$ (10-20) in the final state multiplicity emerges out from the present study, confirming some of the earlier findings in this direction. As for heavier hadrons with relatively small abundances, a similar threshold is observed for $⟨ N_{ch} ⟩ ≃$ 40 hinting towards formation of a thermal bath where all the heavier hadrons are in equilibrium.
↳ hep-phhep-exnucl-exnucl-thEPJA(2020)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE

Lattice QCD evaluation of the Compton amplitude employing the Feynman-Hellmann theorem

Spectral functions and dynamic critical behavior of relativistic Z2​ theories

Correlated Energy Uncertainties in Reaction Rate Calculations

Cumulants of multiple conserved charges and global conservation laws

Fireball tomography from bottomonia elliptic flow in relativistic heavy-ion collisions

Properties of the QCD thermal transition with Nf​=2+1 flavours of Wilson quark

Deciphering QCD dynamics in small collision systems using event shape and final state multiplicity at the Large Hadron Collider

Affiliations

Spectral functions and dynamic critical behavior of relativistic $Z_{2}$ theories

Properties of the QCD thermal transition with $N_{f} = 2 + 1$ flavours of Wilson quark