Nuclear Theory·nucl-th

Tuesday·October 6, 2020

13 papers—8 primary·5 cross-listed

09
Jet Wake from Linearized Hydrodynamics
Jorge Casalderrey-Solana🇪🇸 · José Guilherme Milhano🇵🇹 · Daniel Pablos🇳🇴 · Krishna Rajagopal🇺🇸 · Xiaojun Yao🇺🇸
We explore how to improve the hybrid model description of the particles originating from the wake that a jet produced in a heavy ion collision leaves in the droplet of quark-gluon plasma (QGP) through which it propagates, using linearized hydrodynamics on a background Bjorken flow. Jet energy and momentum loss described by the hybrid model become currents sourcing linearized hydrodynamics. By solving the linearized hydrodynamic equations numerically, we investigate the development of the wake in the dynamically evolving droplet of QGP, study the effect of viscosity, scrutinize energy-momentum conservation, and check the validity of the linear approximation. We find that linearized hydrodynamics works better in the viscous case because diffusive modes damp the energy-momentum perturbation produced by the jet. We calculate the distribution of particles produced from the jet wake by using the Cooper-Frye prescription and find that both the transverse momentum spectrum and the distribution of particles in azimuthal angle are similar in shape in linearized hydrodynamics and in the hybrid model. Their normalizations are different because the momentum-rapidity distribution in the linearized hydrodynamics analysis is more spread out, due to sound modes. Since the Bjorken flow has no transverse expansion, we explore the effect of transverse flow by using local boosts to add it into the Cooper-Frye formula. After including the effects of transverse flow in this way, the transverse momentum spectrum becomes harder: more particles with transverse momenta bigger than $2$ GeV are produced than in the hybrid model. Although we defer implementing this analysis in a jet Monte Carlo, as would be needed to make quantitative comparisons to data, we gain a qualitative sense of how the jet wake may modify jet observables by computing proxies for two example observables: the lost energy recovered in a cone of varying open angle, and the fragmentation function. We find that linearized hydrodynamics with transverse flow effects added improves the description of the jet wake in the hybrid model in just the way that comparison to data indicates is needed. Our study illuminates a path to improving the description of the wake in the hybrid model, highlighting the need to take into account the effects of both transverse flow and the broadening of the energy-momentum perturbation in spacetime rapidity on particle production.
↳ hep-phnucl-thJHEP(2021)·64 citations
10
Patchy nuclear chain reactions
Eric Dumonteil🇫🇷 · Rian Bahran🇺🇸 · Theresa Cutler🇺🇸 · Benjamin Dechenaux🇫🇷 · Travis Grove🇺🇸 · Jesson Hutchinson🇺🇸 · George McKenzie🇺🇸 · Alexander McSpaden🇺🇸 · Wilfried Monange🇫🇷 · Mark Nelson🇺🇸 · Nicholas Thompson🇺🇸 · Andrea Zoia🇫🇷
Stochastic fluctuations of the neutron population within a nuclear reactor are typically prevented by operating the core at a sufficient power, since a deterministic behavior of the neutron population is required by automatic safety systems to detect unwanted power excursions. Recent works however pointed out that, under specific circumstances, non-Poissonian patterns could affect neutron spatial distributions. This motivated an international program to experimentally detect and characterize such fluctuations and correlations, which took place in 2017 at the Rensselaer Polytechnic Institute Reactor Critical Facility. The main findings of this program will indeed unveil patchiness in snapshots of neutron spatial distributions -- obtained with a dedicated numerical twin of the reactor -- that support this first experimental characterization of the 'neutron clustering' phenomenon, while a stochastic model based on reaction-diffusion processes and branching random walks will reveal the key role played by the reactor intrinsic sources in understanding neutron spatial correlations.
↳ physics.ins-detnucl-exnucl-th0 citations
11
Second order relativistic viscous hydrodynamics within an effective description of hot QCD medium
Samapan Bhadury🇮🇳 · Manu Kurian🇮🇳 · Vinod Chandra🇮🇳 · Amaresh Jaiswal🇮🇳
The second-order hydrodynamic equations for evolution of shear and bulk viscous pressure have been derived within the framework of covariant kinetic theory based on the effective fugacity quasiparticle model. The temperature-dependent fugacity parameter in the equilibrium distribution function leads to a mean field term in the Boltzmann equation which affects the interactions in the hot QCD matter. The viscous corrections to distribution function, up to second-order in gradient expansion, have been obtained by employing a Chapman-Enskog like iterative solution of the effective Boltzmann equation within the relaxation time approximation. The effect of mean field contributions to transport coefficients as well as entropy current has been studied up to second-order in gradients. In contrast to the previous calculations, we find non-vanishing entropy flux at second order. The effective description of relativistic second-order viscous hydrodynamics, for a system of interacting quarks and gluons, has been quantitatively analyzed in the case of the $1 + 1 -$ dimensional boost invariant longitudinal expansion. We study the proper time evolution of temperature, pressure anisotropy, and viscous corrections to entropy density for this simplified expansion. The second order evolution of quark-gluon plasma is seen to be affected significantly with the inclusion of mean field contributions and the realistic equation of state.
↳ hep-phhep-thnucl-thJ.Phys.G(2021)·12 citations
12
Lepton angular distribution of $W$ boson productions
Yang Lyu🇺🇸 · Wen-Chen Chang🇹🇼 · Randall Evan McClellan🇺🇸 · Jen-Chieh Peng🇺🇸 · Oleg Teryaev🇷🇺
The lepton angular distribution coefficients $A_{i}$ for $Z$ boson production in $pp$ and $p ˉ p$ collisions have been measured at the LHC and the Tevatron. A recent study showed that many features of the measured angular distribution coefficients, including the transverse momentum ( $q_{T}$ ) and rapidity dependencies and the violation of the Lam-Tung relation, can be well described using an intuitive geometric approach. In this paper, we extend this geometric approach to describe the angular distribution coefficients for $W$ boson produced in $p ˉ p$ collisions at the Tevatron. We first compare the data with a perturbative QCD calculation at $O (α_{s}^{2})$ . We then show that the data and QCD calculations can be well described with the geometric approach. Implications for future studies at the LHC energy are also discussed.
↳ hep-phhep-exnucl-exnucl-thPRD(2021)·5 citations
13
GW190814: On the properties of the secondary component of the binary
Bhaskar Biswas · Rana Nandi · Prasanta Char · Sukanta Bose · Nikolaos Stergioulas
We show that the odds of the mass-gap (secondary) object in GW190814 being a neutron star (NS) improve if one allows for a stiff high-density equation of state (EoS) or a large spin. Since its mass is $\in (2.50, 2.67) M_{⊙}$ , establishing its true nature will make it either the heaviest NS or the lightest black hole (BH), and can have far-reaching implications on NS EoS and compact object formation channels. When limiting oneself to the NS hypothesis, we deduce the secondary's properties by using a Bayesian framework with a hybrid EoS formulation that employs a parabolic expansion-based nuclear empirical parameterization around the nuclear saturation density augmented by a generic 3-segment piecewise polytrope (PP) model at higher densities and combining a variety of astrophysical observations. For the slow-rotation scenario, GW190814 implies a very stiff EoS and a stringent constraint on the EoS specially in the high-density region. On the other hand assuming the secondary object is a rapidly rotating NS, we constrain its rotational frequency to be $f = 117 0_{- 495}^{+ 389}$ Hz, within a $90%$ confidence interval. In this scenario, the secondary object in GW190814 would qualify as the fastest rotating NS ever observed. However, for this scenario to be viable, rotational instabilities would have to be suppressed both during formation and the subsequent evolution until merger, otherwise the secondary of GW190814 is more likely to be a BH.
↳ astro-ph.HEgr-qcnucl-thMNRAS(2021)·78 citations

Affiliations

first authorsco-authorsvia INSPIRE

Jet Wake from Linearized Hydrodynamics

Patchy nuclear chain reactions

Second order relativistic viscous hydrodynamics within an effective description of hot QCD medium

Lepton angular distribution of W boson productions

GW190814: On the properties of the secondary component of the binary

Affiliations

Lepton angular distribution of $W$ boson productions