Nuclear Theory

Rodkin, Dmitry;Tchuvil'sky, Yury

doi: 10.48550/arXiv.2204.08256pmid: N/A

Abstract: The spectrum, partial and total decay widths of the states of the exotic 10Li nucleus are studied in an ab initio approach. The spectrum is calculated using No-Core Shell Model and corresponding extrapolation procedure. The calculations use the well-proven Daejeon16 potential. The NCSM-based approach, which includes a method for constructing the basis of functions of cluster channels and a procedure for matching the cluster form factors obtained within this method with the asymptotic wave functions, is applied to compute the widths of the levels. The results obtained quite adequately reproduce the pattern given by the most advanced experiments. Detailed predictions of the spectral characteristics of 10Li nucleus states are given.

Cucinotta, Francis A.;Pak, Sungmin

doi: 10.48550/arXiv.2204.10800pmid: N/A

Abstract: Proton interactions with 16O nuclei are the most frequent nuclear interaction leading to secondary radiation in tissues for space radiation and cancer therapy with protons. In addition, 16O has the largest fluence of galactic cosmic rays, and interacts with hydrogen in tissue or water and polyethylene shielding. The fragmentation of oxygen produces a large number of heavy ion (A>4) target fragments (TF) with high ionization density. Here we develop an analytical model of energy dependent proton-16O cross sections. We introduce corrections to measurements of total charge changing cross sections to extend data on nuclear absorption cross sections. Using experimental data and a 2nd order optical model an accurate formula for the p-16O absorption cross section from <10 MeV/n to >10 GeV/N is obtained. The energy dependence of the isotopic cross sections is modeled as multiplicities scaled to absorption cross section resulting in an accurate model over the full energy range.

Somasundaram, Rahul;Tews, Ingo;Margueron, Jérôme

doi: 10.48550/arXiv.2204.14039pmid: N/A

Abstract: We construct a physics-agnostic approach to the neutron star (NS) equation of state (EoS) based on a sound speed model, which connects both low-density information from nuclear theory and high-density constraints from perturbative QCD (pQCD). Using this approach, we study the impact of pQCD calculations on NS EoS that have been constrained by astrophysical observations. We find that pQCD affects the EoS mainly beyond the densities realised in NS. Furthermore, we observe an interesting interplay between pQCD and astrophysical constraints, with pQCD preferring softer EoS for the heaviest NS while recent NICER observations suggest the EoS to be stiffer. We explore the sensitivity of our findings to pQCD uncertainties and study the constraining power of pQCD if future observations of heavy NS were to suggest radii larger than 13 km.

Khadkikar, Sanika;Mangat, Chatrik Singh;Banik, Sarmistha

doi: 10.48550/arXiv.2204.01778pmid: N/A

Abstract: In this work, we study the effect of differential rotation, finite temperature and strangeness on the quasi stationary sequences of hyper massive neutron stars (HMNS). We generate constant rest mass sequences of differentially rotating and uniformly rotating stars. The nucleonic matter relevant to the star interior is described within the framework of the relativistic mean field model with the DD2 parameter set. We also consider the strange $\Lambda$ hyperons using the BHB$\Lambda\phi$ equation of state (EoS). Additionally, we probe the behaviour of neutron stars (NS) with these compositions at different temperatures. We report that the addition of hyperons to the EoS produces a significant boost to the spin-up phenomenon. Moreover, increasing the temperature can make the spin-up more robust. We also study the impact of strangeness and thermal effects on the T/W instability. Finally, we analyse equilibrium sequences of a NS following a stable transition from differential rotation to uniform rotation. The decrease in frequency relative to angular momentum loss during this transition is significantly smaller for EoS containing hyperons, compared to nucleonic EoS.

Flambaum, V. V.;Mansour, A. J.

doi: N/Apmid: N/A

Abstract: Nuclei with an octupole deformation have a non-zero electric octupole moment, electric dipole moment (EDM), Schiff moment and magnetic quadrupole moment (MQM) in the intrinsic frame which rotates with the nucleus. In a state with definite angular momentum in the laboratory frame, these moments are forbidden by parity (P) and time reversal invariance (T) conservation, meaning their expectation values vanish due to nuclear rotation. However, nuclei with an octupole deformation have doublets of close opposite parity rotational states with the same spin, which are mixed by T,P-odd nuclear forces. This mixing produces the orientation of the nuclear axis along nuclear spin and all moments existing in the intrinsic frame appear in the laboratory frame (provided the nuclear spin I is sufficiently large to allow such moment). Such a mechanism produces enhanced T,P-violating nuclear moments. This enhancement also takes place in nuclei with a soft octupole vibration mode. Schiff moments in such nuclei have been calculated in previous works. In the present paper we consider the magnetic quadrupole moment which appears in isotopes with nuclear spin $I \geq 1$. Magnetic interaction between the nuclear MQM and electrons produces an atomic EDM and T,P-violating nuclear spin - molecular axis interaction constants for molecules in electronic states with non-zero electron angular momentum. Measurements of these constants may be used to test CP-violation theories and search for axion dark matter in atomic, molecular and solid state experiments. Potential candidate nuclei include 153Eu, 161Dy, 221Fr, 223Fr, 223Ra, 223Rn, 225Ac, 227Ac, 229Th, 229Pa, 233U and 235U. We subsequently consider molecules containing these nuclei (EuO, EuN+, RaF, AcO, AcN+, AcF+, ThO and ThF+).

Pradeep, Maneesha;Rajagopal, Krishna;Stephanov, Mikhail;Yin, Yi

doi: 10.48550/arXiv.2204.00639pmid: N/A

Abstract: We introduce a freeze-out procedure to convert the critical fluctuations in a droplet of quark-gluon plasma (QGP) that has, as it expanded and cooled, passed close to a posited critical point on the phase diagram into cumulants of hadron multiplicities that can subsequently be measured. The procedure connects the out-of-equilibrium critical fluctuations described in concert with the hydrodynamic evolution of the droplet of QGP by extended hydrodynamics, known as Hydro+, with the subsequent kinetic description in terms of observable hadrons. We introduce a critical scalar isoscalar field sigma whose fluctuations cause correlations between observed hadrons due to the couplings of the sigma field to the hadrons via their masses. We match the QGP fluctuations obtained by solving the Hydro+ equations describing the evolution of critical fluctuations before freeze-out to the correlations of the sigma field. In turn, these are imprinted onto correlations and fluctuations in the multiplicity of hadrons, most importantly protons, after freeze-out via the generalization of the familiar half-century-old Cooper-Frye freeze-out prescription which we introduce. The proposed framework allows us to study the effects of critical slowing down and the consequent deviation of the observable predictions from equilibrium expectations quantitatively. We also quantify the suppression of cumulants due to conservation of baryon number. We demonstrate the procedure in practice by freezing out a Hydro+ simulation in an azimuthally symmetric and boost invariant background that includes radial flow discussed in arXiv:1908.08539.

Vovchenko, Volodymyr;Koch, Volker

doi: N/Apmid: N/A

Abstract: We develop a framework to relate proton number cumulants measured in heavy-ion collisions within a momentum space acceptance to the susceptibilities of baryon number, assuming that particles are emitted from a fireball with uniform distribution of temperature and baryochemical potential, superimposed on a hydrodynamic flow velocity profile. The rapidity acceptance dependence of proton cumulants measured by the HADES Collaboration in $\sqrt{s_{\rm NN}} = 2.4$ GeV Au-Au appears to be consistent with thermal emission of nucleons from a grand-canonical heat bath, with the extracted baryon number susceptibilities exhibiting an hierarchy $\chi_4^B \gg -\chi_3^B \gg \chi_2^B \gg \chi_1^B$. Naively, this could indicate large non-Gaussian fluctuations that might point to the presence of the QCD critical point close to the chemical freeze-out at $T \sim 70$ MeV and $\mu_B \sim 850-900$ MeV. However, the description of the experimental data at large rapidity acceptances becomes challenging once the effect of exact baryon number conservation is incorporated, suggesting that more theoretical and experimental studies are needed to reach a firm conclusion.

Feng, Yan-ting;Shao, Feng-lan;Song, Jun

doi: 10.1103/PhysRevC.106.034910pmid: N/A

Abstract: We compile experimental data for the averaged transverse momentum ($\left\langle p_{T}\right\rangle $) of proton, $\Lambda$, $\Xi^{-}$, $\Omega^{-}$ and $\phi$ at mid-rapidity in Au+Au collisions at $\sqrt{s_{NN}}=$ 200, 39, 27, 19.6, 11.5, 7.7 GeV and in Pb+Pb collisions at $\sqrt{s_{NN}}=$ 2.76 TeV, and find that experimental data of these hadrons exhibit systematic correlations. We apply a quark combination model with equal-velocity combination approximation to derive analytic formulas of hadronic $\left\langle p_{T}\right\rangle $ in the case of exponential form of quark $p_{T}$ spectra at hadronization. We use them to successfully explain the systematic correlations exhibited in $\left\langle p_{T}\right\rangle $ data of $p\Lambda$, $\Lambda\Xi^{-}$, $\Xi^{-}\Omega^{-}$ and $\Xi^{-}\phi$ pairs. We also use them to successfully explain the regularity observed in $\left\langle p_{T}\right\rangle $ of these hadrons as the function of $(dN_{ch}/dy)/(N_{part}/2)$ at mid-rapidity in central heavy-ion collisions at both RHIC and LHC energies. Our results suggest that the constituent quark degrees of freedom and the equal-velocity combination of these constituent quarks at hadronization play important role in understanding the production of baryons and $\phi$ meson at these RHIC and LHC energies.

Custódio, Tiago;Pais, Helena;Providência, Constança

doi: 10.48550/arXiv.2204.02260pmid: N/A

Abstract: The production of light nuclei and hypernuclei together with heavy baryons, both hyperons and $\Delta$-baryons, in low density matter as found in stellar environments such as supernova or binary mergers is studied within relativistic mean-field models. Five light nuclei were considered together with three light hypernuclei. The presence of both hyperons and $\Delta$-baryons shift the dissolution of clusters to larger densities and increase the abundance of clusters. This effect is larger the smaller the charge fraction and the higher the temperature. The couplings of the $\Delta$-baryons were chosen imposing that the nucleon effective mass remains finite inside neutron stars.

Brown, B. Alex;Minamisono, Kei

doi: 10.48550/arXiv.2204.06995pmid: N/A

Abstract: Root-mean-square charge radii are discussed in terms of spherical Energy Density Functional (EDF) models corrected for quadrupole deformations. Comparisons between experiment and theory are made for the absolute radii of all even-even nuclei, for the isotonic shift between cadmium and tin isotopes, the isotopic shifts of the calcium isotopes and the isotonic shift for nuclei with $ N=28 $. We conclude that the data are well described in this approach, except for the sharp rise just after the neutron magic numbers.