Nuclear Theory·nucl-th

Friday·September 13, 2019

8 papers—3 primary·5 cross-listed

01
Effect of the repulsive core in the proton-neutron potential on deuteron elastic breakup cross sections
Yuen Sim Neoh · Mengjiao Lyu · Yoshiki Chazono · Kazuyuki Ogata
The role of the short-range part (repulsive core) of the proton-neutron ( $p n$ ) potential in deuteron elastic breakup processes is investigated. A simplified one-range Gaussian potential and the Argonne V4' (AV4') central potential are adopted in the continuum-discretized coupled-channels (CDCC) method. The deuteron breakup cross sections calculated with these two potentials are compared. The repulsive core is found not to affect the deuteron breakup cross sections at energies from 40 MeV to 1 GeV. To understand this result, an analysis of the peripherality of the elastic breakup processes concerning the $p$ - $n$ relative coordinate is performed. It is found that for the breakup processes populating the $p n$ continua with orbital angular momentum $ℓ$ different from 0, the reaction process is peripheral, whereas it is not for the breakup to the $ℓ = 0$ continua (the s-wave breakup). The result of the peripherality analysis indicates that the whole spatial region of deuteron contributes to the s-wave breakup.
nucl-thPRC(2020)·3 citations
02
Particle Production via Strings and Baryon Stopping within a Hadronic Transport Approach
Justin Mohs🇩🇪 · Sangwook Ryu🇩🇪 · Hannah Elfner🇩🇪
The stopping of baryons in heavy ion collisions at beam momenta of $p_{lab} = 20 - 160 A$ GeV is lacking a quantitative description within theoretical calculations. Heavy ion reactions at these energies are experimentally explored at the Super Proton Synchrotron (SPS) and the Relativistic Heavy Ion Collider (RHIC) and will be studied at future facilities such as FAIR and NICA. Since the net baryon density is determined by the amount of stopping, this is the pre-requisiste for any investigation of other observables related to structures in the QCD phase diagram such as a first-order phase transition or a critical endpoint. In this work we employ a string model for treating hadron-hadron interactions within a hadronic transport approach (SMASH, Simulating Many Accelerated Strongly-interacting Hadrons). Free parameters of the string excitation and decay are tuned to match experimental measurements in elementary proton-proton collisions, where some mismatch in the $x_{F}$ distribution of protons is still present. Afterwards, the model is applied to heavy ion collisions, where the experimentally observed change of the shape of the proton rapidity spectrum from a single peak structure to a double peak structure with increasing beam energy is reproduced. Heavy ion collisions provide the opportunity to study the formation process of string fragments in terms of formation times and reduced interaction cross-sections for pre-formed hadrons. A good agreement with the measured rapidity spectra of protons and pions is achieved while insights on the fragmentation process are obtained. In the future, the presented approach can be used to create event-by-event initial conditions for hybrid calculations.
nucl-thJ.Phys.G(2020)·74 citations
03
Probing uncertainties of nuclear structure corrections in light muonic atoms
Oscar Javier Hernandez🇩🇪 · Chen Ji🇨🇳 · Sonia Bacca🇩🇪 · Nir Barnea🇮🇱
Recent calculations of nuclear structure corrections to the Lamb shift in light muonic atoms are based on an expansion in a parameter eta, where only terms up to second order are retained. The parameter eta can be shown to be proportional to the square root of the muon/proton mass ratio, so that it is small and the expansion is expected to converge. However, practical implementations show that the eta convergence may be slower than expected. In this work we probe the uncertainties due to this expansion using a different formalism, which is based on a multipole expansion of the longitudinal and transverse response functions and was first introduced by Leidemann and Rosenfelder. We refer to this alternative expansion as the eta-less formalism. We generalize this formalism to account for the cancellation of elastic terms such as the third Zemach moment (or Friar moment) and embed it in a computationally efficient framework. We implement and test this approach in the case of muonic deuterium. The comparison of results in the point nucleon limit for both methods achieve sub-percent agreement. When nucleon form factors are introduced we find a 4% and 2% difference in the third Zemach moment and nuclear polarizability, respectively, compared to the eta-less expansion, indicating that the nucleon form factor approximations should be improved. However, we find that the sum of these terms removes this dependence and the uncertainty due to the eta-expansion and the related second-order approximation in the nucleon form factors amounts only to 0.2% and thus is fully justified in muonic deuterium. This computationally efficient framework paves the way to further studies in light muonic systems with more than two nucleons, where controlling and reducing uncertainties in nuclear structure corrections is key to the experimental efforts of the CREMA collaboration.
nucl-thphysics.atom-phPRC(2019)·20 citations
04
Role of vector channel in different classes of (non) magnetized neutron stars
Luiz L. Lopes🇧🇷 · Debora P. Menezes🇧🇷
We study how the magnetic field and non-standard vector channels affect hadronic, quarkionic and hybrid stars. In the hadronic phase, we use the QHD model, within its standard $σ ω ρ$ mesons, and compare the results with the ones obtained with the inclusion of the strangeness hidden $ϕ$ meson. In the quark phase, we use the standard SU(3) NJL and compare the results with the version that takes into account the vector channel $G_{v} (ψ ˉ γ^{μ} ψ)$ . Magnetic fields are taken into account via chaotic magnetic field approximation.
↳ astro-ph.HEnucl-thEPJA(2020)·31 citations
05
The breaking of continuous scale invariance to discrete scale invariance: a universal quantum phase transition
Omrie Ovdat · Eric Akkermans
We provide a review on the physics associated with phase transitions in which continuous scale invariance is broken into discrete scale invariance. The rich features of this transition characterized by the abrupt formation of a geometric ladder of eigenstates, low energy universality without fixed points, scale anomalies and Berezinskii-Kosterlitz-Thouless scaling is described. The important role of this transition in various celebrated single and many body quantum systems is discussed along with recent experimental realizations. Particular focus is devoted to a recent realization in graphene.
↳ cond-mat.mes-hallmath-phmath.MPquant-ph1 citation
06
Finite Size Scaling in Time Evolution During the Colorless-QCD Confining Phase Transition
Salah Cherif🇩🇿 · Madjid Lakhdar Hamou Ladrem🇸🇦 · Z.Z. Alfull🇸🇦 · M.A.A. Ahmed🇲🇾
The time evolution of the expanding Colorless Partonic Matter, created in Ultra-Relativistic Heavy Ion Collisions and undergoing the confining phase transition towards a Hadronic Gas, is discussed in the context of a unified model combining our Colorless QCD-MIT Bag Model with the boost invariant Bjorken expansion. The Bjorken Equation in the case of a longitudinal expansion scenario of a non-ideal relativistic medium in finite volume is solved using certain initial conditions $(τ_{i}, T (τ_{i}))$ and their effect is studied in detail. The evolution of the temperature as a function of the proper time $T (τ, V)$ is then obtained at different volumes. Different times characterising different scales of the whole time evolution, like the time of the finite volume transition point $τ_{0} (V)$ , the hadronic time $τ_{H} (V)$ at which the hadronization is completed, the lifetime of the Colorless Partonic Plasma $Δ τ_{C P P} (V)$ and the lifetime of the confining phase transition $Δ τ_{P T} (V)$ are calculated and their finite size scaling properties are studied in detail. New finite size scaling laws are derived. Also, the time evolution of some Thermal Response Functions as the order parameter $H (τ, V)$ , energy density $ϵ (τ, V)$ , pressure $P (τ, V)$ and the sound velocity $C_{s} (τ, V)$ are investigated and studied in detail. We find that the time evolution of our system is really affected by the colorlessness requirement and the initial conditions of the partonic matter: the closer the volume is to the thermodynamic limit, the longer are the times and the lifetimes of the system. A detailed analysis of the temporal decreasing, in negative power, of the energy density $ϵ (τ, V) \propto τ^{- θ}$ in each of the three stages of the Bjorken expansion is carried out.
↳ hep-phnucl-th1 citation
07
Three-body unitarity versus finite-volume $π^{+} π^{+} π^{+}$ spectrum from lattice QCD
M. Mai🇺🇸 · M. Döring🇺🇸 · C. Culver🇺🇸 · A. Alexandru🇺🇸
Strong three-body interactions above threshold govern the dynamics of many exotics and conventional excited mesons and baryons. Three-body finite-volume energies calculated from lattice QCD promise an ab-initio understanding of these systems. We calculate the three- $π^{+}$ spectrum unraveling the three-body dynamics that is tightly intertwined with the $S$ -matrix principle of three-body unitarity and compare it with recent lattice QCD results. For this purpose, we develop a formalism for three-body systems in moving frames and apply it numerically.
↳ hep-latnucl-thPRD(2020)·106 citations
08
Role of event multiplicity on hadronic phase lifetime and QCD phase boundary in ultrarelativistic collisions at energies available at the BNL Relativistic Heavy Ion Collider and CERN Large Hadron Collider
Dushmanta Sahu🇮🇳 · Sushanta Tripathy🇮🇳 · Girija Sankar Pradhan🇮🇳 · Raghunath Sahoo🇮🇳
Hadronic resonances, having very short lifetime, like $K^{* 0}$ , can act as useful probes to understand and estimate lifetime of hadronic phase in ultra-relativistic proton-proton, p--Pb and heavy-ion collisions. Resonances with relatively longer lifetime, like $ϕ$ meson, can serve as a tool to locate the QGP phase boundary. We estimate a lower limit of hadronic phase lifetime in Cu--Cu and Au--Au collisions at RHIC, and in pp, p--Pb and Pb--Pb collisions at different LHC collision energies. Also, we obtain the effective temperature of $ϕ$ meson using Boltzmann-Gibbs Blast-Wave function, which gives an insight to locate the QGP phase boundary. We observe that the hadronic phase lifetime strongly depends on final state charged-particle multiplicity, whereas the QGP phase and hence the QCD phase boundary shows a very weak multiplicity dependence. This suggests that the hadronisation from a QGP state starts at a similar temperature irrespective of charged-particle multiplicity, collision system and collision energy, while the endurance of hadronic phase is strongly dependent on final state charge-particle multiplicity, system size and collision energy.
↳ hep-phhep-exnucl-exnucl-thPRC(2020)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE