Nuclear Theory·nucl-th

Friday·May 4, 2018

13 papers—7 primary·6 cross-listed

08
Effective kinetic description of event-by-event pre-equilibrium dynamics in high-energy heavy-ion collisions
Aleksi Kurkela🇨🇭 · Aleksas Mazeliauskas🇩🇪 · Jean-François Paquet🇺🇸 · Sören Schlichting🇺🇸 · Derek Teaney🇺🇸
We develop a macroscopic description of the space-time evolution of the energy-momentum tensor during the pre-equilibrium stage of a high-energy heavy-ion collision. Based on a weak coupling effective kinetic description of the microscopic equilibration process (à la "bottom-up"), we calculate the non-equilibrium evolution of the local background energy-momentum tensor as well as the non-equilibrium linear response to transverse energy and momentum perturbations for realistic boost-invariant initial conditions for heavy ion collisions. We demonstrate how this framework can be used on an event-by-event basis to propagate the energy momentum tensor from far-from-equilibrium initial state models, e.g. IP-Glasma, to the time $τ_{hydro}$ when the system is well described by relativistic viscous hydrodynamics. The subsequent hydrodynamic evolution becomes essentially independent of the hydrodynamic initialization time $τ_{hydro}$ as long as $τ_{hydro}$ is chosen in an appropriate range where both kinetic and hydrodynamic descriptions overlap. We find that for $s_{N N} = 2.76 TeV$ central Pb-Pb collisions, the typical time scale when viscous hydrodynamics with shear viscosity over entropy ratio $η / s = 0.16$ becomes applicable is $τ_{hydro} \sim 1 fm/c$ after the collision.
↳ hep-phnucl-thPRC(2019)·248 citations
09
Eta Decay and Muonic Puzzles
Yu-Sheng Liu🇨🇳 · Ian C. Cloët🇺🇸 · Gerald A. Miller🇺🇸
New physics motivated by muonic puzzles (proton radius and muon $g - 2$ discrepancies) is studied. Using a light scalar boson $ϕ$ , assuming Yukawa interactions, accounts for these muonic puzzles simultaneously. Our previous work limits the existence of such a scalar boson's mass $m_{ϕ}$ from about 160 keV to 60 MeV. We improve this result by including the influence of all of the possible particles that couple to the $ϕ$ in computing the decay rate. Doing this involves including the strong interaction physics, involving quarks, necessary to compute the $η π ϕ$ vertex function. The Nambu-Jona-Lasinio model, which accounts for the spontaneous symmetry breaking that yields the constituent mass is employed to represent the relevant strong-interaction physics. We use the $η π ϕ$ vertex function to reanalyze the electron beam dump experiments. The result is that the allowed range of $m_{ϕ}$ lies between about 160 keV and 3.5 MeV. This narrow range represents an inviting target for ruling out or discovering this scalar boson. A possible UV completion of our phenomenological model is discussed.
↳ hep-phhep-exnucl-exnucl-th+1NPB(2019)·11 citations
10
Uncertainties in s-process nucleosynthesis in low mass stars determined from Monte Carlo variations
G. Cescutti · R. Hirschi · N. Nishimura · J. W. den Hartogh · T. Rauscher · A. St. J. Murphy · S. Cristallo
The main s-process taking place in low mass stars produces about half of the elements heavier than iron. It is therefore very important to determine the importance and impact of nuclear physics uncertainties on this process. We have performed extensive nuclear reaction network calculations using individual and temperature-dependent uncertainties for reactions involving elements heavier than iron, within a Monte Carlo framework. Using this technique, we determined the uncertainty in the main s-process abundance predictions due to nuclear uncertainties link to weak interactions and neutron captures on elements heavier than iron. We also identified the key nuclear reactions dominating these uncertainties. We found that $β$ -decay rate uncertainties affect only a few nuclides near s-process branchings, whereas most of the uncertainty in the final abundances is caused by uncertainties in neutron capture rates, either directly producing or destroying the nuclide of interest. Combined total nuclear uncertainties due to reactions on heavy elements are in general small (less than 50%). Three key reactions, nevertheless, stand out because they significantly affect the uncertainties of a large number of nuclides. These are $^{56}$ Fe(n, $γ$ ), $^{64}$ Ni(n, $γ$ ), and $^{138}$ Ba(n, $γ$ ). We discuss the prospect of reducing uncertainties in the key reactions identified in this study with future experiments.
↳ astro-ph.SRnucl-exnucl-thMNRAS(2018)·32 citations
11
Exclusive production of pions and the pion distribution amplitude
D. A. Fagundes🇧🇷 · E. G. S. Luna🇧🇷 · A. A. Natale🇧🇷 · M. Pelaez🇧🇷
Considering, as a limit case, an approximately flat pion distribution amplitude, which is determined from the hardest, in momentum space, solution of the Bethe-Salpeter equation for the pion wave function, we compute the pion transition form factor $F_{π γ γ^{*}} (Q^{2})$ and the pion form factor $F_{π} (Q^{2})$ , taking into account the LO as well as NLO form of the hard coefficient function entering the leading-twist factorization formula. We also compute the exclusive photoproduction of pions pairs at high energies, $γ γ \to π^{+} π^{-}$ , where perturbative QCD can be used to compute the hard scattering matrix elements. We verify that the existent data for exclusive pion production can be reasonably described as a function of such flat distribution amplitude.
↳ hep-phhep-exnucl-thJ.Phys.G(2020)·1 citation
12
The maximum mass of dark matter existing in compact stars based on the self-interacting fermionic model
X. D. Wang · B. Qi · N. B. Zhang · S. Y. Wang
By assuming that only gravitation acts between dark matter (DM) and normal matter (NM), we studied DM admixed neutron stars (DANSs) using the two-fluid TOV equations. The NM and DM of compact stars are simulated by the relativistic mean field (RMF) theory and non-self-annihilating self-interacting fermionic model, respectively. The effects of the particle mass of fermionic DM $m_{f}$ and the interaction strength parameter $y$ on the properties of DANSs are investigated in detail. $m_{f}$ and $y$ are considered as the free parameters due to the lack of information about the particle nature of DM so far. For a DANS, we suggest a simple universal relationship $M_{D}^{m a x} = (0.267 y + 0.627 - 3.21 \frac{M _{N}}{\M _{⊙}}) (\frac{1 \GeV}{m _{f}})^{2} \M_{⊙}$ for $y > 100$ , where $M_{D}^{m a x}$ is the maximum mass of DM existing in DANSs and $M_{N}$ is the mass of the neutron star without DM. For free fermion DM model ( $y$ =0), the relationship becomes $M_{D}^{m a x} = (0.627 - 0.027 \frac{M _{N}^{2}}{\M _{⊙}^{2}}) (\frac{1 \GeV}{m _{f}})^{2} \M_{⊙}$ . The radius of DM $R_{D}$ shows a linear relationship with $M_{D}^{m a x}$ in DANSs, namely $R_{D} = (7.02 \frac{M _{D}^{m a x}}{\M _{⊙}} + 1.36)$ ~km. These conclusions are independent of the different NM EOSs from RMF theory. Such a kind of universal relationship connecting the nature of DM particle and mass of stars might shed light on the constraining the nature of the DM by indirect method.
↳ astro-ph.COnucl-thInt.J.Mod.Phys.D(2019)·9 citations
13
Benchmarking the variational reduced density matrix theory in the doubly-occupied configuration interaction space with integrable pairing models
A. Rubio-Garcia · D. R. Alcoba · P. Capuzzi · J. Dukelsky
The variational reduced density matrix theory has been recently applied with great success to models within the truncated doubly-occupied configuration interaction space, which corresponds to the seniority zero subspace. Conservation of the seniority quantum number restricts the Hamiltonians to be based on the SU(2) algebra. Among them there is a whole family of exactly solvable Richardson-Gaudin pairing Hamiltonians. We benchmark the variational theory against two different exactly solvable models, the Richardson-Gaudin-Kitaev and the reduced BCS Hamiltonians. We obtain exact numerical results for the so-called PQGT N-representability conditions in both cases for systems that go from 10 to 100 particles. However, when random single-particle energies as appropriate for small superconducting grains are considered, the exactness is lost but still a high accuracy is obtained.
↳ cond-mat.str-elcond-mat.supr-connucl-thquant-phJ.Chem.Theor.Comput.(2018)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE

Effective kinetic description of event-by-event pre-equilibrium dynamics in high-energy heavy-ion collisions

Eta Decay and Muonic Puzzles

Uncertainties in s-process nucleosynthesis in low mass stars determined from Monte Carlo variations

Exclusive production of pions and the pion distribution amplitude

The maximum mass of dark matter existing in compact stars based on the self-interacting fermionic model

Benchmarking the variational reduced density matrix theory in the doubly-occupied configuration interaction space with integrable pairing models

Affiliations