Nuclear Theory·nucl-th

Monday·July 25, 2022

9 papers—2 primary·7 cross-listed

01
The European Muon Collaboration effect from short-range correlated nucleons in a $x$ -rescaling model
Rong Wang🇨🇳 · Na-Na Ma🇨🇳 · Tao-Feng Wang🇨🇳
In this paper, we examine the hypothesis that the nuclear EMC effect comes merely from the N-N SRC pairs inside the nucleus and that the properties of N-N SRC pair are universal among the various nuclei, using the conventional $x$ -rescaling model for the EMC effect. With the previously determined effective mass of the short-range correlated nucleon and the number of N-N SRC pairs estimated, we calculate the EMC effect of various nuclei within the $x$ -rescaling approach. From our calculations, the nuclear EMC effect due to the mass deficits of the SRC nucleons is not enough to reproduce the observed EMC effect in experiments. We speculate that the internal structure of the mean-field single nucleon is also obviously modified, or there are more origins of the EMC effect beyond the N-N SRC configuration (such as the $α$ cluster), or the universality of N-N SRC pair is violated noticeably from light to heavy nuclei.
nucl-thhep-phCPC(2023)·12 citations
02
Ab initio calculation of the $β$ decay spectrum of $^{6}$ He
Garrett B. King🇺🇸 · Alessandro Baroni🇺🇸 · Vincenzo Cirigliano🇺🇸 · Stefano Gandolfi🇺🇸 · Leendert Hayen🇺🇸 · Emanuele Mereghetti🇺🇸 · Saori Pastore🇺🇸 · Maria Piarulli🇺🇸
We calculate the $β$ spectrum in the decay of $^{6}$ He using Quantum Monte Carlo methods with nuclear interactions derived from chiral Effective Field Theory and consistent weak vector and axial currents. We work at second order in the multipole expansion, retaining terms suppressed by $O (q^{2} / m_{π}^{2})$ , where $q$ denotes low-energy scales such as the reaction's $Q$ -value or the electron energy, and $m_{π}$ the pion mass. We go beyond the impulse approximation by including the effects of two-body vector and axial currents. We estimate the theoretical error on the spectrum by using four potential models in the Norfolk family of local two- and three-nucleon interactions, which have different cut-off, fit two-nucleon data up to different energies and use different observables to determine the couplings in the three-body force. We find the theoretical uncertainty on the $β$ spectrum, normalized by the total rate, to be well below the permille level, and to receive contributions of comparable size from first and second order corrections in the multipole expansion. We consider corrections to the $β$ decay spectrum induced by beyond-the-Standard Model charged-current interactions in the Standard Model Effective Field Theory, with and without sterile neutrinos, and discuss the sensitivity of the next generation of experiments to these interactions.
nucl-thhep-phnucl-exPRC(2023)·36 citations
03
The Fast Flavor Instability in Hypermassive Neutron Star Disk Outflows
Rodrigo Fernández🇨🇦 · Sherwood Richers🇺🇸 · Nicole Mulyk🇨🇦 · Steven Fahlman🇨🇦
We examine the effect of neutrino flavor transformation by the fast flavor instability (FFI) on long-term mass ejection from accretion disks formed after neutron star mergers. Neutrino emission and absorption in the disk set the composition of the disk ejecta, which subsequently undergoes $r$ -process nucleosynthesis upon expansion and cooling. Here we perform 28 time-dependent, axisymmetric, viscous-hydrodynamic simulations of accretion disks around hypermassive neutron stars (HMNSs) of variable lifetime, using a 3-species neutrino leakage scheme for emission and an annular-lightbulb scheme for absorption. We include neutrino flavor transformation due the FFI in a parametric way, by modifying the absorbed neutrino fluxes and temperatures, allowing for flavor mixing at various levels of flavor equilibration, and also in a way that aims to respect the lepton-number preserving symmetry of the neutrino self-interaction Hamiltonian. We find that for a promptly-formed black hole (BH), the FFI lowers the average electron fraction of the disk outflow due to a decrease in neutrino absorption, driven primarily by a drop in electron neutrino/antineutrino flux upon flavor mixing. For a long-lived HMNS, the disk emits more heavy lepton neutrinos and reabsorbs more electron neutrinos than for a BH, with a smaller drop in flux compensated by a higher neutrino temperature upon flavor mixing. The resulting outflow has a broader electron fraction distribution, a more proton-rich peak, and undergoes stronger radiative driving. Disks with intermediate HMNS lifetimes show results that fall in between these two limits. In most cases, the impact of the FFI on the outflow is moderate, with changes in mass ejection, average velocity, and average electron fraction of order $\sim 10%$ , and changes in the lanthanide/actinide mass fraction of up to a factor $\sim 2$ .
↳ astro-ph.HEastro-ph.SRgr-qcnucl-thPRD(2022)·76 citations
04
Effective-theory description of heavy-flavored hadrons and their properties in a hot medium
Glòria Montaña🇪🇸
This dissertation investigates exotic hadrons with heavy-quark content that may be understood as being generated dynamically from the hadron-hadron interaction. This interaction is derived from a suitable effective Lagrangian and properly unitarized in a full coupled-channel basis. In particular, we discuss the possible interpretation of some of the {\Omega}c* excited states recently discovered at LHCb as being meson-baryon molecular states. We also discuss the dynamical generation of excited open-charm mesons from the scattering of pseudoscalar and vector charmed mesons off light mesons. We show that a double-pole structure is predicted for the D0*(2300) state, as well as for the D1(2430), while the Ds0*(2317) and the Ds1(2460) may be interpreted as molecular bound states. Extensions of these calculations to the bottom sector are also presented. Furthermore, we investigate the thermal modification of the open heavy-flavor mesons in a hot medium. By means of an extension to finite temperature of the unitarized effective interactions with the light mesons, we obtain the in-medium spectral properties of the D, D*, Ds, and Ds* ground-state mesons. We also analyze the temperature dependence of the masses and the decay widths of the dynamically generated states. Additionally, we provide results for the bottomed mesons by exploiting the heavy-quark spin-flavor symmetry of the Lagrangian. We employ the temperature-dependent spectral functions to compute charm Euclidean correlators. We also present calculations of off-shell transport coefficients in the hadronic phase implementing in-medium scattering amplitudes and the thermal dependence of the heavy-meson spectral properties.
↳ hep-phnucl-th5 citations
05
Spatial densities of momentum and forces in spin-one hadrons
Adam Freese🇺🇸 · Wim Cosyn🇺🇸
Densities associated with the energy-momentum tensor are calculated for spin-one targets. These calculations are done in a light front formalism, which accounts for relativistic effects due to boosts and allows for arbitrary spatial localization of the target. These densities include the distribution of momentum, angular momentum, and pressures over a two-dimensional plane transverse to the light front. Results are obtained for both longitudinally and transversely polarized targets, and the formalism is tailored to allow the possibility of massless targets. The momentum density and pressure distributions are calculated for a deuteron target in a light cone convolution model, with which the properties of this model (such as helicity dependence of the densities) is illustrated.
↳ hep-phnucl-thPRD(2022)·23 citations
06
Spatial densities of the photon on the light front
Adam Freese🇺🇸 · Wim Cosyn🇺🇸
The light front densities of momentum, angular momentum, and intrinsic pressure are calculated for the photon, both in the free case and at leading order in quantum electrodynamics. In the latter case, we moreover decompose the form factors into photon and electron contributions. Circularly and linearly polarized photons are both considered, with the latter containing significant azimuthal modulations in both the momentum density and in intrinsic stresses. We find that the D-term of the photon is positive instead of negative, and accordingly the intrinsic radial pressure of the photon is negative. Despite this, the radiation pressure exerted by the photon is positive. We illustrate through explicit calculation how the intrinsic pressure associated with the D-term and the radiation pressure exerted by the photon are different quantities.
↳ hep-phnucl-thPRD(2022)·14 citations
07
Study of elastic and inelastic scattering of $^{7}$ Be + $^{12}$ C at 35 MeV
K. Kundalia🇮🇳 · D. Gupta🇮🇳 · Sk M. Ali🇮🇳 · Swapan K Saha🇮🇳 · O. Tengblad🇪🇸 · J.D. Ovejas🇪🇸 · A. Perea🇪🇸 · I. Martel🇪🇸 · J. Cederkall🇸🇪 · J. Park🇸🇪 · S. Szwec🇫🇮 · A. M. Moro
The elastic and inelastic scattering of $^{7}$ Be from $^{12}$ C have been measured at an incident energy of 35 MeV. The inelastic scattering leading to the 4.439 MeV excited state of $^{12}$ C has been measured for the first time. The experimental data cover an angular range of $θ_{c m}$ = 15 $^{\circ}$ -120 $^{\circ}$ . Optical model analyses were carried out with Woods-Saxon and double-folding potential using the density dependent M3Y (DDM3Y) effective interaction. The microscopic analysis of the elastic data indicates breakup channel coupling effect. A coupled-channel analysis of the inelastic scattering, based on collective form factors, show that mutual excitation of both $^{7}$ Be and $^{12}$ C is significantly smaller than the single excitation of $^{12}$ C. The larger deformation length obtained from the DWBA analysis could be explained by including the excitation of $^{7}$ Be in a coupled-channel analysis. The breakup cross section of $^{7}$ Be is estimated to be less than 10 $%$ of the reaction cross section. The intrinsic deformation length obtained for the $^{12}$ C $^{*}$ (4.439 MeV) state is $δ_{2}$ = 1.37 fm. The total reaction cross section deduced from the analysis agrees very well with Wong's calculations for similar weakly bound light nuclei on $^{12}$ C target.
↳ nucl-exnucl-thPLB(2022)·19 citations
08
Transport properties of the QCD medium
Jacopo Ghiglieri🇫🇷
I present an overview of recent developments in the microscopic description of the quark-gluon plasma. I will concentrate on medium-induced emission and transverse momentum broadening. These are two key ingredients of the theory of jet modifications in the QCD medium and of the kinetic theory used for transport and thermalisation. The main focus is on progress towards a better understanding of theory and of its uncertainties.
↳ hep-phnucl-thActa Phys.Polon.Supp.(2023)·1 citation
09
The $P_{ψ s}^{Λ} (4338)$ pentaquark and its partners in the molecular picture
Mao-Jun Yan🇨🇳 · Fang-Zheng Peng🇨🇳 · Mario Sánchez Sánchez🇫🇷 · Manuel Pavon Valderrama🇨🇳
The LHCb collaboration has detected a new hidden-charm pentaquark with the quantum numbers of a $Λ$ baryon: the $P_{ψ s}^{Λ} (4338)$ . This pentaquark will be interpreted as a $D ˉ_{s} Λ_{c}$ - $D ˉ Ξ_{c}$ resonance within a contact-range theory. Here we briefly comment on the relation of the new $P_{ψ s}^{Λ} (4338)$ with the $P_{ψ s}^{Λ} (4459)$ . We find that the $P_{ψ s}^{Λ} (4338)$ and $P_{ψ s}^{Λ} (4459)$ both accept a common description in terms of the same parameters, which predicts the existence of a few additional $P_{ψ}^{N}$ , $P_{ψ s}^{Λ}$ , $P_{ψ s}^{Σ}$ and $P_{ψ ss}^{Ξ}$ molecular pentaquarks composed of a charmed antimeson and an antitriplet charmed baryon. The most robust of these predicted pentaquarks is a $P_{ψ s}^{Λ}$ with a mass in the $(4235 - 4255) MeV$ range, while other two interesting ones are a $P_{ψ}^{N} (4150)$ and a $P_{ψ}^{Σ} (4335)$ , the latter basically at the same mass as the $P_{ψ}^{Λ} (4338)$ , with which it might mix owing to isospin symmetry breaking effects.
↳ hep-phhep-exnucl-thPRD(2023)·47 citations

Affiliations

first authorsco-authorsvia INSPIRE