Thu·Feb 3, 2022Thursday·February 3, 2022

1. 01*

   Evolution of the isoscalar giant monopole resonance in the Ca isotope chain

   S. D. Olorunfunmi (1)🇿🇦 · R. Neveling (2)🇿🇦 · J. Carter (1)🇿🇦 · P. von Neumann-Cosel (3)🇩🇪 · I. T. Usman (1)🇿🇦 · P. Adsley (1,2,4,5)🇿🇦 · A. Bahini (1)🇿🇦 · L. P. L. Baloyi (1)🇿🇦 · J. W. Brümmer (4)🇿🇦 · L. M. Donaldson (2)🇿🇦 · H. Jivan (1)🇿🇦 · N. Y. Kheswa (1)🇿🇦 and 16 other authors

   Two recent studies of the evolution of the isoscalar giant monopole resonance (ISGMR) within the calcium isotope chain report conflicting results. One study suggests that the monopole resonance energy, and thus the incompressibility of the nucleus $K_A$ increase with mass, which implies that $K_{\tau }$, the asymmetry term in the nuclear incompressibility, has a positive value. The other study reports a weak decreasing trend of the energy moments, resulting in a generally accepted negative value for $K_{\tau }$. An independent measurement of the central region of the ISGMR in the Ca isotope chain is provided to gain a better understanding of the origin of possible systematic trends. Inelastically scattered $\alpha$ particles from a range of calcium targets (${}^{40,42,44,48}\mathrm{Ca}$), observed at small scattering angles including 0${}^{\circ }$, were momentum analyzed in the K600 magnetic spectrometer at iThemba LABS, South Africa. Monopole strengths spanning an excitation-energy range between 9.5 and 25.5 MeV were obtained using the difference-of-spectra (DoS) technique. The structure of the $E0$ strength distributions of ${}^{40,42,44}$Ca agrees well with the results from the previous measurement that supports a weak decreasing trend of the energy moments, while no two datasets agree in the case of ${}^{48}$Ca. Despite the variation in the structural character of $E0$ strength distribution from different studies, we find for all datasets that the moment ratios, calculated from the ISGMR strength in the excitation-energy range that defines the main resonance region, display at best only a weak systematic sensitivity to a mass increase. Different trends observed in the nuclear incompressibility are caused by contributions to the $E0$ strength outside of the main resonance region, and in particular for high excitation energies.

   nucl-exPRC(2022)·18 citations
2. 02*

   Electric monopole transitions and low-lying level structure in 106Pd

   N. Marchini🇮🇹 · A. Nannini🇮🇹 · M. Ottanelli🇮🇹 · A. Saltarelli · G. Benzoni🇮🇹 · E. R. Gamba🇮🇹 · A. Goasduff🇮🇹 · A. Gottardo🇮🇹 · J. Ha🇰🇷 · T. Krings🇩🇪 · M. Perri · M. Polettini🇮🇹 · M. Rocchini🇨🇦 · P. Sona🇮🇹

   The structure of 106Pd, populated in the EC/beta+ decay of 106Ag, was investigated at the INFN Legnaro National Laboratories using the Spes Low-energy Internal Conversion Electron Spectrometer (SLICES). The K-internal conversion coefficients of some transitions have been measured and the electric monopole transition strengths, between low-lying 2+ and 0+ states, have been deduced. These experimental data combined with the results from internal conversion electron measurement on 104Pd previously performed by the Florence spectroscopy group were compared with the theoretical values calculated in the framework of the interacting proton-neutron boson model. Good agreement between experimental and theoretical values is found when interpreting the 0+3 level as an intruder state.

   nucl-ex0 citations
3. 03*

   Measurement of beauty production via non-prompt ${\mathrm{D}}^0$ mesons in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   ALICE Collaboration

   The production of non-prompt ${\mathrm{D}}^0$ mesons from beauty-hadron decays was measured at midrapidity ($\left|y\right|<0.5$) in Pb-Pb collisions at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$ with the ALICE experiment at the LHC. Their nuclear modification factor ($R_{\mathrm{AA}}$), measured for the first time down to $p_{\mathrm{T}}=1\mathrm{GeV}/c$ in the $0-10$% and $30-50$% centrality classes, indicates a significant suppression, up to a factor of about three, for $p_{\mathrm{T}}>5\mathrm{GeV}/c$ in the $0-10$% central Pb-Pb collisions. The data are described by models that include both collisional and radiative processes in the calculation of beauty-quark energy loss in the quark-gluon plasma, and quark recombination in addition to fragmentation as a hadronisation mechanism. The ratio of the non-prompt to prompt ${\mathrm{D}}^0$-meson $R_{\mathrm{AA}}$ is larger than unity for $p_{\mathrm{T}}>4\mathrm{GeV}/c$ in the $0-10$% central Pb-Pb collisions, as predicted by models in which beauty quarks lose less energy than charm quarks in the quark-gluon plasma because of their larger mass.

   nucl-exJHEP(2022)·65 citations
4. 04*

   High accuracy, high resolution 235U(n,f) cross section from n_TOF (CERN) in the thermal to 10 keV energy range

   n_TOF collaboration: M. Mastromarco · S. Amaducci · N. Colonna · P. Finocchiaro · L. Cosentino · O. Aberle · J. Andrzejewski · L. Audouin · M. Bacak · J. Balibrea · M. Barbagallo · F. Bečvář and 109 other authors

   The 235U(n,f) cross section was measured in a wide energy range (25 meV - 170 keV) at the n_TOF facility at CERN, relative to 6Li(n,t) and 10B(n,alpha) standard reactions, with high resolution and accuracy, with a setup based on a stack of six samples and six silicon detectors placed in the neutron beam. In this paper we report on the results in the region between thermal and 10 keV neutron energy. A resonance analysis has been performed up to 200 eV, with the code SAMMY. The resulting fission kernels are compared with the ones extracted on the basis of the resonance parameters of the most recent major evaluated data libraries. A comparison of the n_TOF data with the evaluated cross sections is also performed from thermal to 10 keV neutron energy for the energy-averaged cross section in energy groups of suitably chosen width. A good agreement is found in average between the new results and the latest evaluated data files ENDF-B/VIII and JEFF-3.3, as well as with respect to the IAEA reference files. However, some discrepancies are still present in some specific energy regions. The new dataset here presented, characterized by unprecedented resolution and accuracy, can help improving the evaluations in the Resolved Resonance Region and up to 10 keV, and reduce the uncertainties that affect this region.

   nucl-exEPJA(2022)·4 citations
5. 05*

   Uncovering a chirally suppressed mechanism of $0\nu \beta \beta$ decay with LHC searches

   Michael L. Graesser🇺🇸 · Gang Li🇺🇸 · Michael J. Ramsey-Musolf🇨🇳 · Tianyang Shen🇺🇸 · Sebastián Urrutia-Quiroga🇺🇸

   $\Delta L=2$ lepton number violation (LNV) at the TeV scale could provide an alternative interpretation of positive signal(s) in future neutrinoless double beta $(0\nu \beta \beta )$ decay experiments. An interesting class of models from this point of view are those that at low energies give rise to dimension-9 vector operators and a dimension-7 operator, both of whose $0\nu \beta \beta$-decay rates are "chirally suppressed". We study and compare the sensitivities of $0\nu \beta \beta$-decay experiments and LHC searches to a simplified model in this class of TeV-scale LNV that is also $SU(2{)}_L\times U(1{)}_Y$ gauge invariant. The searches for $0\nu \beta \beta$ decay, which are here diluted by a chiral suppression of the vector operators, are found to be less constraining than LHC searches whose reach is increased by the assumed kinematic accessibility of the mediator particles. For the chirally suppressed dimension-7 operator generated by TeV-scale mediators, in contrast, $0\nu \beta \beta$-decay searches place strong constraints on the size of the new Yukawa coupling. Signals of this model at the LHC and $0\nu \beta \beta$-decay experiments are entirely uncorrelated with the observed neutrinos masses, as these new sources of LNV give negligible contributions to the latter. We find the prospects for the high-luminosity LHC and ton-scale $0\nu \beta \beta$-decay experiments to uncover the chirally-suppressed mechanism with TeV-scale LNV to be promising. We also comment on the sensitivity of the $0\nu \beta \beta$-decay lifetime to certain unknown low-energy constants that in the case of dimension-9 {\it scalar} operators are expected to be large due to non-perturbative renormalization.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2022)·17 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.