Nuclear Theory·nucl-th

Friday·February 24, 2023

8 papers—1 primary·7 cross-listed

01
From inclusive to semi-inclusive one-nucleon knockout in neutrino event generators
Alexis Nikolakopoulos🇺🇸 · Steven Gardiner🇺🇸 · Afroditi Papadopoulou🇺🇸 · Stephen Dolan🇨🇭 · Raúl González-Jiménez🇪🇸
In neutrino event generators, for models for neutrino and electron scattering only inclusive cross sections are implemented. When these models are used to describe a semi-inclusive cross section, the event generator attaches the hadron variables based on some assumptions. In this work we compare the nucleon kinematics given by the method used in the GENIE event generator, e.g. in the implementation of the SuSAv2 model, to a fully unfactorized calculation using the relativistic distorted wave impulse approximation (RDWIA). We focus on kinematics relevant to the $e 4 ν$ analysis and show that observables obtained with RDWIA differ significantly from those of the approximate method used in GENIE, the latter should be considered unrealistic.
nucl-thhep-phPhys.Sci.Forum(2023)·11 citations
02
How to measure the reactor neutrino flux below the inverse beta decay threshold with CE $ν$ NS
Jiajun Liao🇨🇳 · Hongkai Liu🇮🇱 · Danny Marfatia🇺🇸
Most antineutrinos produced in a nuclear reactor have energies below the inverse beta decay threshold, and have not yet been detected. We show that a coherent elastic neutrino-nucleus scattering experiment with an ultra-low energy threshold like NUCLEUS can measure the flux of reactor neutrinos below 1.8 MeV. Using a regularized unfolding procedure, we find that a meaningful upper bound can be placed on the low energy flux, but the existence of the neutron capture component cannot be established.
↳ hep-phhep-exnucl-exnucl-thPRD(2023)·3 citations
03
Elliptic flow of identified hadrons in Au+Au collisions at $E_{l ab} = 35 A GeV$ using the PHSD model
B. Towseef🇮🇳 · M. Farooq🇮🇳 · V. Bairathi🇨🇱 · B. Waseem🇮🇳 · S. Kabana🇨🇱 · S. Ahmad🇮🇳
We present elliptic flow ( $v_{2}$ ) of identified hadrons at mid-rapidity ( $∣ y ∣ < 1.0$ ) in Au+Au collisions at $E_{l ab} = 35 A GeV$ using the Parton Hadron String Dynamics (PHSD) model. Transverse momentum ( $p_{T}$ ) dependence of identified hadron $v_{2}$ in minimum bias (0-80%) and three different centrality intervals (0-10%, 10-40%, and 40-80%) are presented. A clear centrality dependence of $v_{2} (p_{T})$ is observed for particles and anti-particles in Au+Au collisions at $E_{l ab} = 35 A GeV$ . We also present $p_{T}$ dependence of $v_{2}$ difference ( $Δ v_{2}$ ) between particles and corresponding antiparticles. A significant difference in $v_{2}$ values for baryons and anti-baryons is observed. The number of constituent quark (NCQ) scaling of $v_{2}$ is discussed in Au+Au collisions at $E_{l ab} = 35 A GeV$ . We also present ratio of $v_{2} (p_{T})$ between the HSD and PHSD modes to explore the effect of hadronic and partonic interactions in the medium. We observe higher $v_{2}$ in PHSD mode than the HSD mode, which suggests the formation of partonic medium in Au+Au collisions at $E_{l ab} = 35 A GeV$ . These predictions are useful for the interpretation of data measured in Beam Energy Scan (BES) program at RHIC and will be useful for the future Compressed Baryonic Matter (CBM) experiment at the Facility for Antiproton and Ion Research (FAIR).
↳ nucl-exhep-phnucl-thEPJC(2023)·2 citations
04
Elliptic flow of inclusive charged hadrons in Au+Au collisions at $E_{l ab} = 35 A GeV$ using the PHSD model
Waseem Bhat🇮🇳 · M. Farooq Mir🇮🇳 · Vipul Bairathi🇨🇱 · Towseef Bhat🇮🇳 · Sonia Kabana🇨🇱 · Shabir Bhat🇮🇳
Elliptic flow ( $v_{2}$ ) measurements of inclusive charged hadrons at mid-rapidity ( $∣ η ∣ <$ 1.0) in Au+Au collisions at $E_{l ab} = 35 A GeV$ using the Parton Hadron String Dynamics (PHSD) model are presented as a function of centrality, transverse momentum ( $p_{T}$ ) and pseudo-rapidity ( $η$ ). The $v_{2}$ results are obtained using the $η$ -sub event plane method with respect to event plane angle ( $ψ_{2}$ ) and participant plane angle ( $ψ_{2}^{P P}$ ). $p_{T}$ -integrated charged hadron $v_{2}$ shows a strong centrality dependence in Au+Au collisions at $E_{l ab} = 35 A GeV$ . The eccentricity scaled elliptic flow ( $v_{2} / ε_{2}$ ) also shows centrality dependence. The higher values of $v_{2} / ε_{2}$ in central collisions suggest development of stronger collectivity. The measurements are compared with the results from Au+Au collisions at $s_{NN} = 7.7 GeV$ published by the STAR experiment at RHIC. We also compare results of HSD and PHSD modes of the model to investigate contribution of hadronic and partonic phases of the medium on the measured $v_{2}$ . The current results serve as a prediction of the collective behavior of the matter produced in baryon rich and moderate temperature conditions for the upcoming Compressed Baryonic Matter (CBM) experiment at the Facility for Antiproton and Ion Research (FAIR). These predictions are also useful for the interpretation of data measured at RHIC Beam Energy Scan (BES) program.
↳ nucl-exhep-phnucl-thJ.Phys.G(2023)·1 citation
05
Regeneration of bottomonia in an open quantum systems approach
Nora Brambilla🇩🇪 · Miguel Ángel Escobedo🇪🇸 · Ajaharul Islam🇺🇸 · Michael Strickland🇺🇸 · Anurag Tiwari🇺🇸 · Antonio Vairo🇩🇪 · Peter Vander Griend🇺🇸
We demonstrate the importance of quantum jumps in the nonequilibrium evolution of bottomonium states in the quark-gluon plasma. Based on nonrelativistic effective field theory and the open quantum system framework, we evolve the density matrix of color singlet and octet pairs. We show that quantum regeneration of singlet states from octet configurations is necessary to understand experimental results for the suppression of both bottomonium ground and excited states. The values of the heavy-quarkonium transport coefficients used are consistent with recent lattice QCD determinations.
↳ hep-phhep-exhep-latnucl-ex+1PRD(2023)·51 citations
06
Nonextensive effects on QCD chiral phase diagram and baryon-number fluctuations within Polyakov-Nambu-Jona-Lasinio model
Ya-Peng Zhao🇨🇳 · Chao-Yong Wang🇨🇳 · Shu-Yu Zuo🇨🇳 · Cheng-Ming Li🇨🇳
In this paper, a version of the Polyakov-Nambu-Jona-Lasinio (PNJL) model based on nonextensive statistical mechanics is presented. This new statistics summarizes all possible factors that violate the assumptions of the Boltzmann-Gibbs (BG) statistics to a dimensionless nonextensivity parameter $q$ , and when $q$ tends to 1, it returns to the BG case. Within the nonextensive PNJL model, we found that as $q$ increases, the location of the critical end point (CEP) exhibits non-monotonic behavior. That is, for $q < 1.15$ , CEP moves in the direction of lower temperature and larger quark chemical potential. But for $q > 1.15$ , CEP turns to move in the direction of lower temperature and lower quark chemical potential. In addition, we studied the moments of the net-baryon number distribution, that is, the variance ( $σ^{2}$ ), skewness (S), and kurtosis ( $κ$ ). Our results are generally consistent with the latest experimental data, especially for $S_{N N} > 19.6 GeV$ , when $q$ is set to $1.07$ .
↳ hep-phnucl-thCPC(2023)·12 citations
07
Probing chiral-even and chiral-odd leading twist quark generalised parton distributions through the exclusive photoproduction of a $γ ρ$ pair
Goran Duplančić🇭🇷 · Saad Nabeebaccus🇫🇷 · Kornelija Passek-Kumerički🇭🇷 · Bernard Pire🇫🇷 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷
We extend our studies of a new class of $2 \to 3$ exclusive processes using the collinear factorisation framework by considering the exclusive photoproduction of a $γ ρ$ pair, in the kinematics where the pair has a large invariant mass, {and the outgoing $ρ$ -meson has a sufficiently large transverse momentum to not resonate with the nucleon}. We cover the whole kinematical range from medium energies in fixed target experiments to very large energies of colliders, by considering the experimental conditions of JLab~12-GeV, COMPASS, future EIC and LHC (in ultra-peripheral collisions) cases. One of the main interest in studying the present process is that it provides access to both chiral-even and chiral-odd GPDs, depending on the polarisation of the outgoing $ρ$ -meson, both at leading twist. Our analysis covers both neutral and charged $ρ$ -mesons. We find that the order of magnitude of the obtained cross sections are sufficiently large for a dedicated experimental analysis to be performed, especially at JLab, for both longitudinally and transversely polarised $ρ$ . Furthermore, we compute the linear photon beam polarisation asymmetry {which is} sizeable for a longitudinally polarised meson. These predictions are obtained for both asymptotic distribution amplitude (DA) and the \textit{holographic} DA.
↳ hep-phhep-exnucl-exnucl-thPRD(2023)·44 citations
08
Impact of pions on binary neutron star mergers
Vimal Vijayan🇩🇪 · Ninoy Rahman🇩🇪 · Andreas Bauswein🇩🇪 · Gabriel Martínez-Pinedo🇩🇪 · Ignacio L. Arbina🇩🇪
We study the impact of pions in simulations of neutron star mergers and explore the impact on gravitational-wave observables. We model charged and neutral pions as a non-interacting Boson gas with a chosen, constant effective mass. We add the contributions of pions, which can occur as a condensate or as a thermal population, to existing temperature and composition dependent equations of state. Compared to the models without pions, the presence of a pion condensate decreases the characteristic properties of cold, non-rotating neutron stars such as the maximum mass, the radius and the tidal deformability. We conduct relativistic hydrodynamical simulations of neutron star mergers for these modified equations of state models and compare to the original models, which ignore pions. Generally, the inclusion of pions leads to a softening of the equation of state, which is more pronounced for smaller effective pion masses. We find a shift of the dominant postmerger gravitational-wave frequency by up to 150~Hz to higher frequencies and a reduction of the threshold binary mass for prompt black-hole formation by up to 0.07~ $M_{⊙}$ . We evaluate empirical relations between the threshold mass or the dominant postmerger gravitational-wave frequency and stellar parameters of nonrotating neutron stars. These relations are constructed to extract these stellar properties from merger observations and are built based on large sets of equation of state models which do not include pions. Comparing to our calculations with pions, we find that these empirical relations remain valid to good accuracy, which justifies their use although they neglect a possible impact of pions. We also address the mass ejection by neutron star mergers and observe a moderate enhancement of the ejecta mass by a few ten per cent. (abridged)
↳ astro-ph.HEnucl-thPRD(2023)·31 citations

Affiliations

first authorsco-authorsvia INSPIRE