Nuclear Theory·nucl-th

Tuesday·October 3, 2023

11 papers—5 primary·6 cross-listed

01
Isoscalar Giant Monopole Resonance in Mo-100: TDHF calculations and ground state deformation
P. D Stevenson · Abhishek · Yue Shi
The isoscalar giant monopole resonance in molybdenum-100 has been measured in recent alpha scattering experiments and its strength function extracted. By performing time-dependent Hartree-Fock calculations with Skyrme effective interactions, we are able to reproduce the gross features of the observed strength. The details of the structure are found to be dependent on the ground state shape. We use a measure of fit to determine which ground state shape correlates with the observed strength and find evidence for triaxiality in this nucleus.
nucl-thNuovo Cim.C(2024)·0 citations
02
Contrasting Features of Parton Energy Loss in Heavy-ion Collisions at RHIC and the LHC
Thomas Marshall🇺🇸 · Philip Suh🇺🇸 · Gang Wang🇺🇸 · Huan Zhong Huang🇺🇸
Energetic quarks and gluons lose energy as they traverse the hot and dense medium created in high-energy heavy-ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC). The nuclear modification factor ( $R_{AA}$ ) of leading particles quantifies parton energy loss in such collisions, with the particle spectrum in $p + p$ collisions as a reference. Previous $R_{AA}$ measurements at RHIC energies have revealed an approximately constant trend at high transverse momenta ( $p_{T}$ ), implying a scenario where parton energy loss, $Δ p_{T}$ , scales proportionally with $p_{T}$ , a feature naively expected from energy loss dynamics in elastic collisions. In this study, we investigate the LHC $R_{AA}$ measurements which exhibit a pronounced $p_{T}$ dependence of $R_{AA}$ for various particle species, and our analysis attributes this behavior to $Δ p_{T}$ being approximately proportional to $p_{T}$ . These distinct features are consistent with model calculations of dominant radiative energy loss dynamics at the LHC, in contrast to the dominance of collisional energy loss at RHIC. Additionally, the linear increase of fractional energy loss with medium density at different $p_{T}$ magnitudes affirms the previous empirical observation that the magnitude of the energy loss depends mostly on the initial entropy density, with no significant path-length dependence. Implications on the dynamical scenarios of parton energy loss and future experimental investigations will also be discussed.
nucl-thhep-exhep-phnucl-exCPC(2025)·2 citations
03
Determination of the moments of the proton charge density: is there a proton radius puzzle?
M. Atoui · M.B. Barbaro · M. Hoballah · C. Keyrouz · R. Kunne · M. Lassaut · D. Marchand · G. Quemener · E. Voutier
The charge radius of the proton can be determined using two different kinds of experiments: the spectroscopy technique, measuring the hyperfine structure of hydrogen atoms, and the scattering technique, deducing the radius from elastic lepton scattering off a proton target. These two methods lead to quite different results, a discrepancy known as the "proton radius puzzle ". To shed light on this problem, we have proposed a novel method for the determination of spatial moments from densities expressed in the momentum space. This method provides a direct access not only to the second order moment, directly related to the proton radius, but to all moments of any real order larger than -3. The method is applied to the global analysis of proton electric form factor experimental data from Rosenbluth separation and low- $Q^{2}$ experiments, paying specific attention to the evaluation of the systematic errors. Within this analysis, the integer order moments of the proton charge density are evaluated, the moment of second order leading to a new determination of the proton charge radius.
nucl-thhep-phnucl-exNucl.Theor.(2023)·1 citation
04
Shell-model study of $β^{+}$ /EC-decay half-lives for $Z = 21 - 30$ nuclei
Vikas Kumar · Praveen C. Srivastava
In the present work, we have reported $β^{+}$ /EC-decay half-lives for $Z = 21 - 30$ nuclei using large-scale shell-model. %and N $\leq$ A recent study shows that some proton-rich nuclei in this region belong to the island of inversion. We have performed calculations for these nuclei using KB3G effective interaction, while for Ni, Cu, and Zn nuclei we have used JUN45 effective interaction in the $f_{5/2} p g_{9/2}$ model space. The calculated quenching factors for $f p$ and $f_{5/2} p g_{9/2}$ space using KB3G and JUN45 effective interactions are also reported. Shell-model results of $β$ -decay half-lives, excitation energies, log $f t$ values, and branching fractions are discussed and compared with the available experimental data. We have obtained a reasonable agreement with the available data.
nucl-thnucl-exEPJA(2023)·5 citations
05
Electric dipole transitions in the relativistic quasiparticle random phase approximation at finite temperature
Amandeep Kaur · Esra Yüksel · Nils Paar
Finite temperature results in various effects on the properties of nuclear structure and excitations of relevance for nuclear processes in hot stellar environments. Here we introduce the self-consistent finite temperature relativistic quasiparticle random phase approximation (FT-RQRPA) based on relativistic energy density functional with point coupling interaction for describing the temperature effects in electric dipole (E1) transitions. We perform a study of E1 excitations in the temperature range $T =$ 0-2 MeV for the selected closed- and open-shell nuclei ranging from $^{40}$ Ca to $^{60}$ Ca and $^{100}$ Sn to $^{140}$ Sn by including both thermal and pairing effects. The isovector giant dipole resonance strength is slightly modified for the considered range of temperature, while new low-energy peaks emerge for $E <$ 12 MeV with non-negligible strength in neutron-rich nuclei at high temperatures. The analysis of relevant two-quasiparticle configurations discloses how new excitation channels open due to thermal unblocking of states at finite temperature. The study also examines the isospin and temperature dependence of electric dipole polarizability ( $α_{D}$ ), resulting in systematic increase in the values of $α_{D}$ with increasing temperature, with a more pronounced effect observed in neutron-rich nuclei. The FT-RQRPA introduced in this work will open perspectives for microscopic calculation of $γ$ -ray strength functions at finite temperatures relevant for nuclear reaction studies.
nucl-thPRC(2024)·11 citations
06
Zemach and Friar radii of the proton and neutron from lattice QCD
Dalibor Djukanovic🇩🇪 · Georg von Hippel🇩🇪 · Harvey B. Meyer🇩🇪 · Konstantin Ottnad🇩🇪 · Miguel Salg🇩🇪 · Hartmut Wittig🇩🇪
We present the first lattice-QCD result for the Zemach and Friar radii of the proton and neutron. Our calculation includes both quark-connected and -disconnected diagrams and assesses all sources of systematic uncertainties arising from excited-state contributions, finite-volume effects and the continuum extrapolation. At the physical point, we obtain for the proton $r_{Z}^{p} = (1.013 \pm 0.010 (stat) \pm 0.012 (syst)) fm$ and $r_{F}^{p} = (1.301 \pm 0.012 (stat) \pm 0.014 (syst)) fm$ . These numbers suggest small values of the Zemach and Friar radii of the proton, but are compatible with most of the experimental studies.
↳ hep-lathep-phnucl-thPRD(2024)·9 citations
07
Quantum Field Theory in Large N Wonderland: Three Lectures
Paul Romatschke🇺🇸
In these lecture notes, I review how to use large N techniques to solve quantum field theories in various dimensions. In particular, the case of N-dimensional quantum mechanics, non-relativistic cold and dense neutron matter, and scalar field theory in four dimensions are covered. A recurring theme is that large N solutions are fully non-perturbative, and can be used to reliably access quantum field theory for parameter regions where weak-coupling expansions simply fail.
↳ hep-thhep-phnucl-thActa Phys.Polon.B(2024)·18 citations
08
Scalar boson emission from a magnetized relativistic plasma
Jorge Jaber-Urquiza🇲🇽 · Igor A. Shovkovy🇺🇸
We investigate the differential emission rate of neutral scalar bosons from a highly magnetized relativistic plasma. We show that three processes contribute at the leading order: particle splitting ( $ψ \to ψ + ϕ$ ), antiparticle splitting ( $ψ ˉ \to ψ ˉ + ϕ$ ), and particle-antiparticle annihilation ( $ψ + ψ ˉ \to ϕ$ ). This is in contrast to the scenario with zero magnetic field, where only the annihilation processes contribute to boson production. We examine the impact of Landau-level quantization on the energy dependence of the rate and investigate the angular distribution of emitted scalar bosons. The differential rate resulting from both (anti)particle splitting and annihilation processes are typically suppressed in the direction of the magnetic field and enhanced in perpendicular directions. Overall, the background magnetic field significantly amplifies the total emission rate. We speculate that our model calculations provide valuable theoretical insights with potentially important applications.
↳ hep-phhep-thnucl-thPRD(2023)·5 citations
09
Multibaryon configurations in a simple chromomagnetic model
Aaron Park🇰🇷
In this work, we study the multibaryon configurations in a simple chromomagnetic model. We first construct the wave function of the multibaryon states using the multiquark configuration. We consider all possible quantum numbers assuming the spatial part of the wave function to be totally symmetric. Then, we calculate the color-spin factors for tetrabaryons, pentabaryons and hexabaryons in the flavor SU(3) breaking case.
↳ hep-phnucl-thPRD(2024)·0 citations
10
Gluon PDF of the proton using twisted mass fermions
Joseph Delmar🇺🇸 · Constantia Alexandrou🇨🇾 · Krzysztof Cichy🇵🇱 · Martha Constantinou🇺🇸 · Kyriakos Hadjiyiannakou🇨🇾
In this paper, we present lattice QCD results for the $x$ -dependence of the unpolarized gluon PDF for the proton. We use one ensemble of $N_{f} = 2 + 1 + 1$ maximally twisted mass fermions with a clover improvement, and the Iwasaki improved gluon action. The quark masses are tuned to produce a pion with a mass of 260 MeV. The ensemble has a lattice spacing of $a = 0.093$ fm and a spatial extent of 3 fm. We employ the pseudo-distribution approach, which relies on matrix elements of non-local operators that couple to momentum-boosted hadrons. In this work, we use five values of the momentum boost between 0 and 1.67 GeV. The gluon field strength tensors of the non-local operator are connected with straight Wilson lines of varying length $z$ . The light-cone Ioffe time distribution (ITD) is extracted utilizing data with $z$ up to 0.56 fm and a quadratic parametrization in terms of the Ioffe time at fixed values of $z$ . We explore systematic effects, such as the effect of the stout smearing for the gluon operator, excited states effects, and the dependence on the maximum value of $z$ entering the fits to obtain the gluon PDF. Also, for the first time, the mixing with the quark singlet PDFs is eliminated using matrix elements with non-local quark operators that were previously analyzed within the quasi-PDF framework on the same ensemble. Here, we expand the data set for the quark singlet and reanalyze within the pseudo-PDFs method eliminating the corresponding mixing in the gluon PDF.
↳ hep-lathep-exhep-phnucl-thPRD(2023)·33 citations
11
Broadening of particle distributions in electron- and (anti)neutrino-nucleus scattering from QED interactions
Oleksandr Tomalak🇺🇸 · Ivan Vitev🇺🇸
Proper interpretation of past, current, and future data on lepton-nucleus reactions requires a clear separation between quantum electrodynamics (QED) and strong interaction effects inside the nucleus. First studies of QED in-medium lepton dynamics have set a theoretical framework to derive electron-nucleus and (anti)neutrino-nucleus cross-section corrections. We employ this approach to quantitatively compute the effects of Glauber photon-mediated multiple re-scattering within the nuclear medium. We find that the relativistic charged lepton acquires momentum of order $10 MeV$ transverse to its direction of propagation inside the nucleus. This broadening sizably deflects expected electron tracks and suppresses scattering cross sections. Precise extraction of the nucleon and nuclear structure by electron and muon probes should, thus, take the QED nuclear medium angular redistribution of particles into account. Our results further show that the associated effects in (anti)neutrino-nucleus scattering with measured final-lepton energy are significant only at the kinematical endpoints.
↳ hep-phhep-exnucl-exnucl-thPRD(2023)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE