Thu·Jan 13, 2022Thursday·January 13, 2022

1. 01*

   A search for neutron to mirror neutron oscillation using neutron electric dipole moment measurements

   Prajwal Mohanmurthy🇺🇸 · Albert R. Young🇺🇸 · Jeff A. Winger🇺🇸 · Geza Zsigmond🇨🇭

   Baryon number violation is a key ingredient of baryogenesis. It has been hypothesized that there could also be a parity-conjugated copy of the standard model particles, called mirror particles. The existence of such a mirror universe has specific testable implications, especially in the domain of neutral particle oscillation, viz. the baryon number violating neutron to mirror-neutron ($n-n^{\prime }$) oscillation. Consequently, there were many experiments that have searched for $n-n^{\prime }$ oscillation, and imposed constraints upon the parameters that describe it. All the previous efforts searched for $n-n^{\prime }$ oscillation by comparing the relative number of ultracold neutrons that survive after a period of storage for one or both of the two cases: (i) comparison of zero applied magnetic field to a non-zero applied magnetic field, and (ii) comparison where the orientation of the applied magnetic field was reversed. However, $n-n^{\prime }$ oscillations also lead to variations in the precession frequency of polarized neutrons upon flipping the direction of the applied magnetic field. For the first time, we used the data from the latest search for the neutron electric dipole moment [Phys. Rev. Lett. 124, 081803 (2020)] to constrain $n-n^{\prime }$ oscillation. After compensating for the systematic effects that affect the ratio of precession frequencies of ultracold neutrons and cohabiting ${}^{199}$Hg-atoms, chief among which was due to their motion in non-uniform magnetic field, we constrained any further perturbations due to $n-n^{\prime }$ oscillation. We thereby provide a lower limit on the $n-n^{\prime }$ oscillation time constant of ${\tau }_{n{n}^{\prime }}/\sqrt{|\cos (\beta )|}>5.7$s, $0.36\mu$T'$<B^{\prime }<1.01\mu$T' (95\% C.L.), where $\beta$ is the angle between the applied magnetic field and the ambient mirror magnetic field. This constraint is the best available in the range of $0.36\mu$T'$<B^{\prime }<0.40\mu$T'.

   nucl-exhep-exSymmetry(2022)·11 citations
2. 02*

   Large enhancement of total reaction cross sections at the edge of the island of inversion in Ti, Cr, and Fe isotopes

   W. Horiuchi🇯🇵 · T. Inakura🇯🇵 · S. Michimasa🇯🇵

   A systematic analysis of nuclear deformation is made for neutron-rich Ti, Cr, and Fe isotopes to explore the nuclear structure in the island of inversion near N = 40, where strong nuclear deformation is predicted. The nuclear ground states are obtained by the Skyrme Hartree-Fock method in three-dimensional coordinate space, which properly describes any nuclear shape. Three types of Skyrme interactions are employed to generate various deformed states in its isotopic chain. We find that in the island of inversion the occupation of highly elongated intruder orbits induces not only large quadrupole deformation but also large hexadecapole deformation. This appears as a sizable enhancement of the nuclear matter radius, showing the characteristic shell effect of the density profile near the nuclear surface. We show that the edge of the island of inversion, where the intruder orbit starts being occupied, can be determined by measuring the enhancement of the total reaction cross section at high incident energy. The possibility of constraining the hexadecapole deformation by a measurement of the total reaction cross sections is discussed.

   ↳ nucl-thnucl-exPRC(2022)·14 citations
3. 03*

   Global $\Lambda$ polarization in heavy-ion collisions at energies 2.4--7.7 GeV: Effect of Meson-Field Interaction

   Yu. B. Ivanov🇷🇺 · A. A. Soldatov🇷🇺

   Based on the three-fluid model, the global $\Lambda$ polarization in Au+Au collisions at 2.4 $\le \sqrt{s_{NN}}\le$ 7.7 GeV is calculated, including its rapidity and centrality dependence. Contributions from the thermal vorticity and meson-field term (proposed by Csernai, Kapusta and Welle) to the global polarization are considered. The results are compared with data from recent and ongoing STAR and HADES experiments. It is predicted that the polarization maximum is reached at $\sqrt{s_{NN}}\approx$ 3 GeV, if the measurements are performed with the same acceptance. The value of the polarization is very sensitive to interplay of the aforementioned contributions. In particular, the thermal vorticity results in quite strong increase of the polarization from the midrapidity to forward/backward rapidities, while the meson-field contribution considerably flattens the rapidity dependence. The polarization turns out to be very sensitive to details of the equation of state. While collision dynamics become less equilibrium with decreasing collision energy, the present approach to polarization is based on the assumption of thermal equilibrium. It is found that equilibrium is achieved at the freeze-out stage, but this equilibration takes longer at moderately relativistic energies.

   ↳ nucl-thhep-phnucl-exPRC(2022)·17 citations
4. 04*

   The yield ratio of anti-nuclei and nuclei of relativistic nuclear collisions in the central rapidity region

   A.I Malakhov🇷🇺 · A.A. Zaitsev🇷🇺

   This article describes calculations of the yield ratio of anti-particles to the yield of particles ($\bar{p}/p$, $\bar{d}/d$,$\overline{{}^3\mathrm{He}}$/${}^3$He) in proton-proton and nuclear-nuclear interactions using the self-similarity parameter in the central rapidity region. The used approach is based on the study of relativistic nuclear interactions in the four-velocity space. The results of the calculations are compared with the existing experimental data in a wide center-of-mass energy range ($SPS$, $RHIC$, $LHC$). Within this approach the inclusive spectra of pions and kaons and ratios of their yields in $pp$ collisions have been successfully described earlier.

   ↳ nucl-thnucl-exJ.Exp.Theor.Phys.(2022)·2 citations
5. 05*

   Theoretical Methods for Giant Resonances

   Gianluca Colo'🇮🇹

   The Random Phase Approximation (RPA) and its variations and extensions are, without any doubt, the most widely used tools to describe Giant Resonances within a microscopic theory. In this chapter, we will start by discussing how RPA comes out naturally if one seeks a state with a harmonic time dependence in the space of one particle-one hole excitations on top of the ground state. It will be also shown that RPA is the simplest approach in which a ``collective'' state emerges. These are basic arguments that appear in other textbooks but are also unavoidable as a starting point for further discussions. In the rest of the chapter, we will give emphasis to developments that have taken place in the last decades: alternatives to RPA like the Finite Amplitude Method (FAM), state-of-the-art calculations with well-established Energy Density Functionals (EDFs), and progress in {\em ab initio} calculations. We will discuss extensions of RPA using as a red thread the various enlargements of the one particle-one hole model space. The importance of the continuum, and the exclusive observables like the decay products of Giant Resonances, will be also touched upon.

   ↳ nucl-thnucl-ex6 citations
6. 06*

   Spin Asymmetries in Electron-jet Production at the EIC

   Zhong-Bo Kang🇺🇸 · Kyle Lee🇺🇸 · Ding Yu Shao🇨🇳 · Fanyi Zhao🇺🇸

   We investigate all the possible spin asymmetries that can occur in back-to-back electron-jet production with hadron observed inside a jet in electron-proton collisions. We derive the factorization formalism for all spin asymmetries and perform phenomenological studies for the future electron ion collider kinematics. We illustrate that the back-to-back electron-jet production opens up new opportunities to study transverse momentum dependent fragmentation functions and distribution functions.

   ↳ hep-phhep-exnucl-exnucl-thJPS Conf.Proc.(2022)·8 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.