Nuclear Theory·nucl-th

Tuesday·June 14, 2022

12 papers—6 primary·6 cross-listed

01
[Submitted on 10 Jun 2022]
Impact of nuclear deformation on collective flow observables in relativistic U+U collisions
Niseem Magdy🇺🇸
A Multi-Phase Transport (AMPT) model is used to investigate the efficacy of several flow observables to constrain the initial-state deformation of the Uranium nuclei in U $+$ U collisions at nucleon-nucleon center-of-mass energy $s_{N N}$ = 193 GeV. The multiparticle azimuthal cumulant method is used to investigate the sensitivity of (I) a set of quantities that are sensitive to both initial- and final-state effects as well as (II) a set of dimensionless quantities that are more sensitive to initial-state effects to the Uranium nuclei quadrupole shape deformation. We find that the combined use of the flow harmonics, flow fluctuations and correlations, linear and non-linear flow correlations to the quadrangular flow harmonic, and the correlations between elliptic flow and the mean-transverse momentum could serve to constrain the nuclear deformation of the Uranium nuclei. Therefore, a comprehensive set of measurements of such observables can provide a quantifying tool for the quadrupole shape deformation via data-model comparisons.
Comments:
9 pages and 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2206.05332 [pdf]
EPJA(2023)·29 citations
02
[Submitted on 10 Jun 2022]
Nuclear Josephson-like $γ$ -emission
R. A. Broglia · F. Barranco · L. Corradi · G. Potel · S. Szilner · E. Vigezzi
Josephson-like junctions, transiently established in heavy ion collisions between superfluid nuclei, few MeV below the Coulomb barrier, allow for the back and forth transfer of a nuclear Cooper pair of effectively charged nucleons and thus the emission of $γ$ -rays. The second order DWBA $T$ -matrix formulation of single Cooper pair alternating current is shown to contain the gauge phases and gauge rotational frequencies as required by the Josephson (ac) effect, in keeping with the derivation of the transfer (tunneling) Hamiltonian in a gauge invariant representation. We describe the emergence of two strongly convergent parameters (conserved quantities) within the time the abnormal densities of the two superfluid nuclei overlap: a) the correlation length (dc); b) the number of emitted $γ$ -rays per cycle (ac), and thus the dipole moment of the successively transferred nucleons. Result which leads to a nuclear parallel with the direct current (dc) and alternating current (ac) Josephson effects, and which testifies to the validity of BCS theory of superconductivity down to few Cooper pair condensates, and single Cooper pair alternating currents. The physics at the basis of a quantitative description of Cooper pair tunneling between weakly coupled superconductors or superfluid nuclei at energies below the Coulomb barrier, is that the process is dominated by the successive transfer of the two partner fermions entangled over distances of the order of the coherence length, $\approx 1 0^{4}$ Å in the case of lead, and 13.5 fm in the case of the reaction $^{116} Sn +^{60} Ni \to^{114} Sn(gs) +^{62} Ni(gs)$ at few MeV below the Coulomb barrier.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2206.05351 [pdf]
1 citation
03
[Submitted on 11 Jun 2022]
The European Muon Collaboration effect in Light-Front Hamiltonian Dynamics
Emanuele Pace (Rome Univ. "Tor Vergata")🇮🇹 · Matteo Rinaldi (Perugia Univ.)🇮🇹 · Giovanni Salme` (INFN - Rome)🇮🇹 · Sergio Scopetta (Perugia Univ.)🇮🇹
A rigorous light-front formalism for electron deep inelastic scattering on unpolarized nuclei, in Bjorken limit, is reported. It preserves Poincaré covariance, macroscopic locality, both number of particles and momentum sum rules. The scheme is applied to the A=3 iso-doublet, very relevant in view of the planned operation with unpolarized and polarized beams at the Electron-Ion Collider. At variance with previous light-front estimates, our procedure, including a realistic nuclear description and free-nucleon structure functions, predicts a sizeable European Muon Collaboration effect for $^{3}$ He. This will allow to analyze deviations from the proposed baseline in terms of genuine QCD effects. The extension to heavier nuclei is straightforward, although numerically challenging.
Comments:
7 pages and 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2206.05485 [pdf]
PLB(2023)·10 citations
04
[Submitted on 11 Jun 2022]
Ab initio estimation of $E 2$ strengths in $^{8}$ Li and its neighbors by normalization to the measured quadrupole moment
Mark A. Caprio · Patrick J. Fasano
For electric quadrupole ( $E 2$ ) observables, which depend on the large-distance tails of the nuclear wave function, ab initio no-core configuration interaction (NCCI) calculations converge slowly, making meaningful predictions challenging to obtain. Nonetheless, the calculated values for different $E 2$ matrix elements, particularly those involving levels with closely-related structure (e.g., within the same rotational band) are found to be robustly proportional. This observation suggests that a known value for one observable may be used to determine the overall scale of $E 2$ strengths, and thereby provide predictions for others. In particular, we demonstrate that meaningful predictions for $E 2$ transitions may be obtained by calibration to the ground-state quadrupole moment. We test this approach for well-measured low-lying $E 2$ transitions in $^{7}$ Li and $^{9}$ Be, then provide predictions for transitions in $^{8}$ Li and $^{9}$ Li. In particular, we address the $2^{+} \to 1^{+}$ transition in $^{8}$ Li, for which the reported measured strength exceeds ab initio Green's function Monte Carlo (GFMC) predictions by over an order of magnitude.
Comments:
10 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2206.05628 [pdf]
PRC(2022)·12 citations
05
[Submitted on 13 Jun 2022]
Laurent+Pietarinen Partial Wave Analysis
A. Svarc🇭🇷 · R. L. Workman🇺🇸
A new energy-dependent fit strategy, independent of any specific microscopic theory, is applied to kaon photoproduction data with center-of-mass energies ranging from 1625 MeV to 2296 MeV. Experimental data are fitted in terms of a modified Laurent expansion (Laurent+Pietarinen expansion) which previously has been successfully applied to multipoles. The present aim is to extract resonance pole parameters directly from the data, rather than from sets of multipoles. A constrained single-energy fit is then used to search for missing structures. In this proof-of-principle study, the data are well-described by the initial L+P fit, and it is shown that only a moderate amount of structure, mostly in higher multipoles, is missing from the original fit. Problems due to an unmeasurable overall phase, plaguing single-channel multipole analyses, are mitigated by implementing a form of phase limitation, fixing the initial values of fit parameters using a multi-channel analysis.
Comments:
23 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2206.05978 [pdf]
PRC(2023)·4 citations
06
[Submitted on 13 Jun 2022]
Speed of sound in dense strong-interaction matter
Jens Braun🇩🇪 · Andreas Geißel🇩🇪 · Benedikt Schallmo🇩🇪
We study the speed of sound in strong-interaction matter at zero temperature and in density regimes which are expected to be governed by the presence of a color-superconducting gap. At (very) high densities, our analysis indicates that the speed of sound approaches its asymptotic value associated with the non-interacting quark gas from below, in agreement with first-principles studies which do not take the presence of a color-superconducting gap into account. Towards lower densities, however, the presence of a gap induces an increase of the speed of sound above its asymptotic value. Importantly, even if gap-induced corrections to the pressure may appear small, we find that derivatives of the gap with respect to the chemical potential can still be sizeable and lead to a qualitative change of the density dependence of the speed of sound. Taking into account constraints on the density dependence of the speed of sound at low densities, our general considerations suggest the existence of a maximum in the speed of sound. Interestingly, we also observe that specific properties of the gap can be related to characteristic properties of the speed of sound which are indirectly constrained by observations.
Comments:
11 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2206.06328 [pdf]
SciPost Phys.Core(2024)·35 citations

Affiliations

first authorsco-authorsvia INSPIRE

Impact of nuclear deformation on collective flow observables in relativistic U+U collisions

Nuclear Josephson-like γ-emission

The European Muon Collaboration effect in Light-Front Hamiltonian Dynamics

Ab initio estimation of E2 strengths in 8Li and its neighbors by normalization to the measured quadrupole moment

Laurent+Pietarinen Partial Wave Analysis

Speed of sound in dense strong-interaction matter

Affiliations

Nuclear Josephson-like $γ$ -emission

Ab initio estimation of $E 2$ strengths in $^{8}$ Li and its neighbors by normalization to the measured quadrupole moment