Wed·Apr 14, 2021Wednesday·April 14, 2021

1. 01*

   Fundamental physics at the strangeness frontier at DA{\Phi}NE. Outline of a proposal for future measurements

   C. Curceanu🇮🇹 · C. Guaraldo🇮🇹 · A. Scordo🇮🇹 · D. Sirghi🇮🇹 · K. Piscicchia🇮🇹 · C. Amsler🇦🇹 · J. Zmeskal🇦🇹 · D. Bosnar🇭🇷 · S. Eidelman🇷🇺 · H. Ohnishi🇯🇵 · Y. Sada🇯🇵

   The DA{\Phi}NE collider at INFN-LNF is a unique source of low-energy kaons, which was used by the DEAR, SIDDHARTA and AMADEUS collaborations for unique measurements of kaonic atoms and kaon-nuclei interactions. Presently, the SIDDHARTA-2 collaboration is underway to measure the kaonic deuterium exotic atom. With this document we outline a proposal for fundamental physics at the strangeness frontier for future measurements of kaonic atoms and kaon-nuclei interactions at DA{\Phi}NE, which is intended to stimulate discussions within the broad scientific community performing research directly or indirectly related to this field.

   nucl-ex10 citations
2. 02*

   Structure in the Event-by-Event Energy-Dependent Neutron-Gamma Multiplicity Correlations in ${}^{252}\text{Cf}$(sf)

   Stefano Marin🇺🇸 · Mustapha Stephan Okar🇺🇸 · Eoin P. Sansevero🇺🇸 · Isabel E. Hernandez🇺🇸 · Catherine A. Ballard🇺🇸 · Ramona Vogt🇺🇸 · Jørgen Randrup🇺🇸 · Patrick Talou🇺🇸 · Amy E. Lovell🇺🇸 · Ionel Stetcu🇺🇸 · Olivier Serot🇫🇷 · Olivier Litaize🇫🇷 and 4 other authors

   The emission of neutrons and gamma rays by fission fragments reveal important information about the properties of fragments immediately following scission. The initial fragment properties, correlations between fragments, and emission competition give rise to correlations in neutron-gamma emission. Neutron-gamma correlations are important in nonproliferation applications because the characterization of fissionable samples relies on the identification of signatures in the measured radiation. Furthermore, recent theoretical and experimental advances have proposed to explain the mechanism of angular momentum generation in fission. In this paper, we present a novel analysis method of neutrons and gamma rays emitted by fission fragments that allows us to discern structure in the observed correlations. We have analyzed data collected on \ce{^{252}Cf}(sf) at the Chi-Nu array at the Los Alamos Neutron Science Center. Through our analysis of the energy-differential neutron-gamma multiplicity covariance, we have observed enhanced neutron-gamma correlations, corresponding to rotational band gamma-ray transitions, at gamma-ray energies of $0.7$ and $1.2$ MeV. To shed light on the origin of this structure, we compare the experimental data with the predictions of three model calculations. The origin of the observed correlation structure is understood in terms of a positive spin-energy correlation in the generation of angular momentum in fission.

   nucl-exnucl-thPRC(2021)·13 citations
3. 03*

   Ambiguities in the hadro-chemical freeze-out of Au+Au collisions at SIS18 energies and how to resolve them

   Anton Motornenko🇩🇪 · Jan Steinheimer🇩🇪 · Volodymyr Vovchenko🇺🇸 · Reinhard Stock🇩🇪 · Horst Stoecker🇩🇪

   The thermal fit to preliminary HADES data of Au+Au collisions at $\sqrt{s_{{}_{NN}}}=2.4$ GeV shows two degenerate solutions at $T\approx 50$ MeV and $T\approx 70$ MeV. The analysis of the same particle yields in a transport simulation of the UrQMD model yields the same features, i.e. two distinct temperatures for the chemical freeze-out. While both solutions yield the same number of hadrons after resonance decays, the feeddown contribution is very different for both cases. This highlights that two systems with different chemical composition can yield the same multiplicities after resonance decays. The nature of these two minima is further investigated by studying the time-dependent particle yields and extracted thermodynamic properties of the UrQMD model. It is confirmed, that the evolution of the high temperature solution resembles cooling and expansion of a hot and dense fireball. The low temperature solution displays an unphysical evolution: heating and compression of matter with a decrease of entropy. These results imply that the thermal model analysis of systems produced in low energy nuclear collisions is ambiguous but can be interpreted by taking also the time evolution and resonance contributions into account.

   ↳ hep-phnucl-exnucl-thPLB(2021)·27 citations
4. 04*

   Addendum to: Combined Constraints on First Generation Leptoquarks

   Andreas Crivellin · Luc Schnell

   In this addendum to arXiv:2101.07811 we discuss the implications of the recent CMS analysis of lepton flavour universality violation in non-resonant di-lepton pairs for first generation leptoquarks. As CMS finds more electron events than expected from background, this analysis prefers the LQ representations ${\tilde{S}}_1,S_2,S_3,{\tilde{V}}_1,V_2({\kappa }_2^{RL}\ne 0)$ and $V_3$ which lead to constructive interference with the SM. In principle the excess could also be (partially) explained by the representations ${\tilde{S}}_2,V_1({\kappa }_1^R\ne 0),V_2({\kappa }_2^{LR}\ne 0),{\tilde{V}}_2$ which are interfering destructively, as this would still lead to the right effect in bins with high invariant mass where the new physics contribution dominates. However, in these cases large couplings would be required which are excluded by other observables. The representations $S_1,V_1({\kappa }_1^L\ne 0)$ cannot improve the fit to the CMS data compared to the SM.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2021)·68 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.