Tue·Dec 29, 2020Tuesday·December 29, 2020

1. 01*

   Laser spectroscopy of neutron-rich ${}^{207,208}$Hg isotopes: Illuminating the kink and odd-even staggering in charge radii across the $N=126$ shell closure

   T. Day Goodacre🇬🇧 · A.V. Afanasjev🇺🇸 · A.E. Barzakh🇷🇺 · B.A. Marsh🇨🇭 · S. Sels🇨🇭 · P. Ring🇩🇪 · H. Nakada🇯🇵 · A.N. Andreyev🇬🇧 · P. Van Duppen🇧🇪 · N.A. Althubiti🇬🇧 · B. Andel🇧🇪 · D. Atanasov🇩🇪 and 32 other authors

   The mean-square charge radii of ${}^{207,208}$Hg ($Z=80,N=127,128$) have been studied for the first time and those of ${}^{202,203,206}$Hg ($N=122,123,126$) remeasured by the application of in-source resonance-ionization laser spectroscopy at ISOLDE (CERN). The characteristic \textit{kink} in the charge radii at the $N=126$ neutron shell closure has been revealed, providing the first information on its behavior below the $Z=82$ proton shell closure. A theoretical analysis has been performed within relativistic Hartree-Bogoliubov and non-relativistic Hartree-Fock-Bogoliubov approaches, considering both the new mercury results and existing lead data. Contrary to previous interpretations, it is demonstrated that both the kink at $N=126$ and the odd-even staggering (OES) in its vicinity can be described predominately at the mean-field level, and that pairing does not need to play a crucial role in their origin. A new OES mechanism is suggested, related to the staggering in the occupation of the different neutron orbitals in odd- and even-$A$ nuclei, facilitated by particle-vibration coupling for odd-$A$ nuclei.

   nucl-exnucl-thPRL(2021)·79 citations
2. 02*

   Investigation of pair-correlated $0^{+}$ states in ${}^{134}$Ba via the ${}^{136}$Ba($p,t$) reaction

   J. C. Nzobadila Ondze🇿🇦 · B. M. Rebeiro🇿🇦 · S. Triambak🇿🇦 · L. Atar🇩🇪 · G. C. Ball🇨🇦 · V. Bildstein🇨🇦 · C. Burbadge🇨🇦 · A. Diaz Varela🇨🇦 · T. Faestermann🇩🇪 · P. E. Garrett🇨🇦 · R. Hertenberger🇩🇪 · M. Kamil🇿🇦 and 4 other authors

   We performed a high resolution study of $0^{+}$ states in ${}^{134}$Ba using the ${}^{136}$Ba($p,t$) two-neutron transfer reaction. Our experiment shows a significant portion of the $L=0$ pair-transfer strength concentrated at excited $0^{+}$ levels in ${}^{134}$Ba. Potential implications in the context of ${}^{136}$Xe $\to$ ${}^{136}$Ba neutrinoless double beta decay matrix element calculations are briefly discussed.

   nucl-exPRC(2021)·7 citations
3. 03*

   Measurement of the neutron decay electron-antineutrino angular correlation by the aCORN experiment

   M. T. Hassan🇺🇸 · W. A. Byron🇺🇸 · G. Darius🇺🇸 · C. DeAngelis🇺🇸 · F. E. Wietfeldt🇺🇸 · B. Collett🇺🇸 · G. L. Jones🇺🇸 · A. Komives🇺🇸 · G. Noid🇺🇸 · E. J. Stephenson🇺🇸 · F. Bateman🇺🇸 · M. S. Dewey🇺🇸 and 3 other authors

   The aCORN experiment measures the neutron decay electron-antineutrino correlation ($a$-coefficient) using a novel method based on an asymmetry in proton time-of-flight for events where the beta electron and recoil proton are detected in delayed coincidence. We report the data analysis and result from the second run at the NIST Center for Neutron Research, using the high-flux cold neutron beam on the new NG-C neutron guide end position: $a=-0.10758\pm 0.00136(\text{mbox}stat)\pm 0.00148(\text{mbox}sys)$. This is consistent within uncertainties with the result from the first aCORN run on the NG-6 cold neutron beam. Combining the two aCORN runs we obtain $a=-0.10782\pm 0.00124(\text{mbox}stat)\pm 0.00133(\text{mbox}sys)$, which has an overall relative standard uncertainty of 1.7 \%. The corresponding result for the ratio of weak coupling constants $\lambda =G_A/G_V$ is $\lambda =-1.2796\pm 0.0062$.

   nucl-exPRC(2021)·38 citations
4. 04*

   Calculating the initial energy density in heavy ion collisions by including the finite nuclear thickness

   Todd Mendenhall🇺🇸 · Zi-Wei Lin🇺🇸

   The initial energy density produced in heavy ion collisions can be estimated with the Bjorken energy density formula after choosing a proper formation time $\tau {}_{\mathrm{F}}$. However, the Bjorken formula breaks down at low energies because it neglects the finite nuclear thickness. Here we include both the finite time duration and finite longitudinal extension of the initial energy production. When $\tau {}_{\mathrm{F}}$ is not too much smaller than the crossing time of the two nuclei, our results are similar to those from a previous study that only considers the finite time duration. In particular, we find that at low energies the initial energy density has a much lower maximum value but evolves much longer than the Bjorken formula, while at large-enough $\tau {}_{\mathrm{F}}$ and/or high-enough energies our result approaches the Bjorken formula. We also find a qualitative difference in that our maximum energy density ${ϵ}^{\max }$ at $\tau {}_{\mathrm{F}}=0$ is finite, while the Bjorken formula diverges as $1/\tau {}_{\mathrm{F}}$ and the previous result diverges as $\ln (1/\tau {}_{\mathrm{F}})$ at low energies but as $1/\tau {}_{\mathrm{F}}$ at high energies. Furthermore, our solution of the energy density approximately satisfies a scaling relation. As a result, the $\tau {}_{\mathrm{F}}$-dependence of ${ϵ}^{\max }$ determines the $A$-dependence, and the weaker $\tau {}_{\mathrm{F}}$-dependence of ${ϵ}^{\max }$ in our results at low energies means a slower increase of ${ϵ}^{\max }$ with $A$.

   ↳ nucl-thnucl-exPRC(2021)·17 citations
5. 05*

   Shape of 13C studied by the real-time evolution method

   S. Shin🇰🇷 · B. Zhou🇯🇵 · M. Kimura🇯🇵

   Background : Recently, Bijker et al. [Phys. Rev. Lett. 122, 162501 (2019)] explained the rotation-vibration spectrum of 13C by assuming triangular nuclear shape with D'3h symmetry. Purpose : The purpose of this work is to test the shape and symmetry of 13C based on a microscopic nuclear model without assumption of nuclear shape. Method : We have applied the real-time evolution method to 13C. By using the equation-of-motion of clusters, the model describes the 3alpha+n system without any assumption of symmetry. Results : REM described the low-lying states more accurately than the previous cluster model studies. The analysis of the wave functions showed that the ground band has approximate triangular symmetry, while the excited bands deviate from it. Conclusion : This work confirmed that the ground band has the intrinsic structure with the triangular arrangement of three alpha particles.

   ↳ nucl-thnucl-exPRC(2021)·10 citations
6. 06*

   Prospects for quarkonium studies at the high-luminosity LHC

   Emilien Chapon🇨🇳 · David d'Enterria🇨🇭 · Bertrand Ducloue🇬🇧 · Miguel G. Echevarria🇪🇸 · Pol-Bernard Gossiaux🇫🇷 · Vato Kartvelishvili🇬🇧 · Tomas Kasemets🇩🇪 · Jean-Philippe Lansberg🇫🇷 · Ronan McNulty🇮🇪 · Darren D. Price🇬🇧 · Hua-Sheng Shao🇫🇷 · Charlotte Van Hulse🇮🇪 and 39 other authors

   Prospects for quarkonium-production studies accessible during the upcoming high-luminosity phases of the CERN Large Hadron Collider operation after 2021 are reviewed. Current experimental and theoretical open issues in the field are assessed together with the potential for future studies in quarkonium-related physics. This will be possible through the exploitation of the huge data samples to be collected in proton-proton, proton-nucleus and nucleus-nucleus collisions, both in the collider and fixed-target modes. Such investigations include, among others, those of: (i) J/psi and Upsilon produced in association with other hard particles; (ii) chi(c,b) and eta(c,b) down to small transverse momenta; (iii) the constraints brought in by quarkonia on gluon PDFs, nuclear PDFs, TMDs, GPDs and GTMDs, as well as on the low-x parton dynamics; (iv) the gluon Sivers effect in polarised-nucleon collisions; (v) the properties of the quark-gluon plasma produced in ultra-relativistic heavy-ion collisions and of collective partonic effects in general; and (vi) double and triple parton scatterings.

   ↳ hep-phhep-exnucl-exnucl-thPPNP(2022)·169 citations
7. 07*

   Nuclear dependence of light neutral meson production in p-A collisions at 400 GeV with NA60

   R. Arnaldi🇮🇹 · K. Banicz🇨🇭 · K. Borer🇨🇭 · J. Castor🇫🇷 · B. Chaurand🇫🇷 · W. Chen🇺🇸 · C. Cicalò🇮🇹 · A. Colla🇮🇹 · P. Cortese🇮🇹 · S. Damjanovic🇨🇭 · A. David🇨🇭 · A. De Falco🇮🇹 and 42 other authors

   The NA60 experiment has studied low-mass muon pair production in proton-nucleus collisions with a system of Be, Cu, In, W, Pb and U targets, using a 400 GeV proton beam at the CERN SPS. The transverse momentum spectra of the $\rho /\omega$ and $\varphi$ mesons are measured in the full $p_{\mathrm{T}}$ range accessible, from $p_{\mathrm{T}}=0$ up to 2 GeV/$c$. The nuclear dependence of the production cross sections of the $\eta$, $\omega$ and $\varphi$ mesons has been found to be consistent with the power law ${\sigma }_{\mathrm{pA}}\propto {\mathrm{A}}^{\alpha }$, with the $\alpha$ parameter increasing as a function of $p_{\mathrm{T}}$ for all the particles, and an approximate hierarchy ${\alpha }_{\eta }\approx {\alpha }_{\varphi }>{\alpha }_{\omega }$. The cross section ratios ${\sigma }_{\eta }/{\sigma }_{\omega }$, ${\sigma }_{\rho }/{\sigma }_{\omega }$ and ${\sigma }_{\varphi }/{\sigma }_{\omega }$ have been studied as a function of the size A of the production target, and an increase of the $\eta$ and $\varphi$ yields relative to the $\omega$ is observed from p-Be to p-U collisions.

   ↳ hep-exnucl-exEPJC(2019)·5 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.