Fri·Feb 25, 2022Friday·February 25, 2022

1. 01*

   Fission properties of ${}^{253}$Rf and the stability of neutron-deficient Rf isotopes

   A. Lopez-Martens🇫🇷 · K. Hauschild🇫🇷 · A.I. Svirikhin🇷🇺 · Z. Asfari🇫🇷 · M.L. Chelnokov🇷🇺 · V.I. Chepigin🇷🇺 · O. Dorvaux🇫🇷 · M. Forge🇫🇷 · B. Gall🇫🇷 · A.V. Isaev🇷🇺 · I.N. Izosimov🇷🇺 · K. Kessaci🇫🇷 and 9 other authors

   An analysis of recent experimental data [J. Khuyagbaatar et al., Phys. Rev. C 104, L031303 (2021)] has established the existence of two fissioning states in ${}^{253}$Rf: the ground state and a low-lying isomeric state, most likely involving the same neutron single-particle configurations as in the lighter isotone ${}^{251}$No. The ratio of fission half-lives measured in ${}^{253}$Rf was used to predict the fission properties of the 1/2${}^{+}$ isomeric state in ${}^{251}$No and draw conclusions as to the stability against fission of even lighter Rf systems. This paper focusses again on the fission properties of ${}^{253}$Rf and their impact on the stability of other neutron deficient isotopes, using new and improved data collected from two experiments performed at the Flerov Laboratory of Nuclear Reactions in Dubna, Russia. Two fission activities with half-lives of 52.8(4.4)$\mu$s and 9.9(1.2) ms were measured in the case of ${}^{253}$Rf, confirming the results of J. Kkuyagbaatar et al. A third state, at much higher excitation energy, was also observed through the detection of its electromagnetic decay to the 52.8$\mu$s state. This observation leads to the opposite quantum-configuration assignments for the fissioning states as compared to the ones established by J. Khuyagbaatar et al., namely that the higher-spin state has the shortest fission half-life. This inversion of the ratio of fission hindrances between the low and high-spin states is corroborated in the isotone ${}^{251}$No by the non observation of any substantial fission branch from the low-spin isomer.

   nucl-exPRC(2022)·22 citations
2. 02*

   Ab initio informed evaluation of the radiative capture of protons on ${}^7$Be

   Konstantinos Kravvaris🇺🇸 · Petr Navrátil🇨🇦 · Sofia Quaglioni🇺🇸 · Chloë Hebborn🇺🇸 · Guillaume Hupin🇫🇷

   The radiative capture of protons by ${}^7$Be, which is the source of ${}^8$B that $\beta$-decays emitting the majority of solar neutrinos measured on earth, has not yet been measured at astrophysically relevant energies. The recommended value for its zero-energy S-factor, $S_{17}$(0) = 20.8$\pm$(0.7)exp$\pm$(1.4)theory eV$\cdot$b, relies on theoretical extrapolations from higher-energy measurements, a process that leads to significant uncertainty. We performed a set of first-principle (or, ab initio) calculations of the ${}^7$Be($p$, $\gamma$)${}^8$B reaction to provide an independent prediction of the low-energy S-factor with quantified uncertainties. We demonstrate underlying features in the predicted S-factor allowing the combination of theoretical calculations and measurements to produce an evaluated S-factor of $S_{17}$(0) = 19.8$\pm$0.3 eV$\cdot$b. We expect the calculations and uncertainty quantification process described here to set a new standard for the evaluation of light-ion astrophysical reactions.

   ↳ nucl-thnucl-exPLB(2023)·32 citations
3. 03*

   Nuclear modification of ${\rm Y}$ states in pPb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV

   CMS Collaboration

   Production cross sections of ${\rm Y}$(1S), ${\rm Y}$(2S), and ${\rm Y}$(3S) states decaying into ${\mu }^{+}{\mu }^{-}$ in proton-lead (pPb) collisions are reported using data collected by the CMS experiment at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV. A comparison is made with corresponding cross sections obtained with pp data measured at the same collision energy and scaled by the Pb nucleus mass number. The nuclear modification factor for ${\rm Y}$(1S) is found to be $R_{\mathrm{pPb}}({\rm Y}(1S))$ = 0.806 $\pm$ 0.024 (stat) $\pm$ 0.059 (syst). Similar results for the excited states indicate a sequential suppression pattern, such that $R_{\mathrm{pPb}}({\rm Y}(1S))$ $>$ $R_{\mathrm{pPb}}({\rm Y}(2S))$ $>$ $R_{\mathrm{pPb}}({\rm Y}(3S))$. The suppression is much less pronounced in pPb than in PbPb collisions, and independent of transverse momentum $p_{\mathrm{T}}^{{\rm Y}}$ and center-of-mass rapidity $y_{\mathrm{CM}}^{{\rm Y}}$ of the individual ${\rm Y}$ state in the studied range $p_{\mathrm{T}}^{{\rm Y}}$ $<$ 30 GeV$/c$ and $|y_{\mathrm{CM}}^{{\rm Y}}|$ $<$ 1.93. Models that incorporate sequential suppression of bottomonia in pPb collisions are in better agreement with the data than those which only assume initial-state modifications.

   ↳ hep-exnucl-exPLB(2022)·56 citations
4. 04*

   Exploring the QGP phase above the deconfinement temperature in $pp$ and $A-A$ collisions at LHC energies

   Aditya Nath Mishra🇭🇺 · Guy Paić🇲🇽 · Carlos Pajares🇪🇸 · Rolf P Scharenberg🇺🇸 · Brijesh K Srivastava🇺🇸

   In the present work we have analyzed the transverse momentum spectra of charged particles in high multiplicity $pp$ collisions at LHC energies $\sqrt{s}=$ 5.02 and 13 TeV published by the ALICE Collaboration using the Color String Percolation Model (CSPM). For heavy ions Pb-Pb at $\sqrt{s_{NN}}=$ 2.76 and 5.02 TeV along with Xe-Xe at $\sqrt{s_{NN}}=$ 5.44 TeV have been analyzed. The initial temperature is extracted both in low and high multiplicity events in $pp$ collisions. For $A-A$ collisions the temperature is obtained as a function of centrality. A universal scaling in the temperature from $pp$ and $A-A$ collisions is obtained when multiplicity is scaled by the transverse interaction area.From the measured energy density $\mathbf{\epsilon }$ and the temperature the dimensionless quantity $\mathbf{\epsilon }/T^4$ is obtained. Our results for Pb-Pb and Xe-Xe collisions show a sharp increase in $\mathbf{\epsilon }/T^4$ above T $\sim$ 210 MeV and reaching the ideal gas of quarks and gluons value of $\mathbf{\epsilon }/T^4\sim$ 16 at temperature $\sim$ 230 MeV. In case of $pp$ collisions only $\mathbf{\epsilon }/T^4\sim$ 10 corresponding to $\sim$ 30 degrees of freedom.

   ↳ hep-phhep-exnucl-exNPA(2024)·11 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.