Fri·Jul 17, 2020Friday·July 17, 2020

1. 01*

   Beta-decay studies for applied and basic nuclear physics

   A. Algora🇪🇸 · J. L. Tain🇪🇸 · B. Rubio🇪🇸 · M. Fallot🇫🇷 · W. Gelletly🇬🇧

   In this review we will present the results of recent beta-decay studies using the total absorption technique that cover topics of interest for applications, nuclear structure and astrophysics. The decays studied were selected primarily because they have a large impact on the prediction of a) the decay heat in reactors, important for the safety of present and future reactors and b) the reactor electron antineutrino spectrum, of interest for particle/nuclear physics and reactor monitoring. For these studies the total absorption technique was chosen, since it is the only method that allows one to obtain beta decay probabilities free from a systematic error called the Pandemonium effect. The measurements presented and discussed here were performed mainly at the IGISOL facility of the University of Jyvaskyla (Finland) using isotopically pure beams provided by the JYFLTRAP Penning trap. Examples are presented to show that the results of our measurements on selected nuclei have had a large impact on predictions of both the decay heat and the anti-neutrino spectrum from reactors. Some of the cases involve beta delayed neutron emission thus one can study the competition between gamma- and neutron-emission from states above the neutron separation energy. The gamma-to-neutron emission ratios can be used to constrain neutron capture (n,gamma)cross sections for unstable nuclei of interest in astrophysics. The information obtained from the measurements can also be used to test nuclear model predictions of half-lives and Pn values for decays of interest in astrophysical network calculations. These comparisons also provide insights into aspects of nuclear structure in particular regions of the nuclear chart.

   nucl-exEPJA(2021)·42 citations
2. 02*

   Pion-kaon femtoscopy and the lifetime of the hadronic phase in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV

   ALICE Collaboration

   In this paper, the first femtoscopic analysis of pion-kaon correlations at the LHC is reported. The analysis was performed on the Pb-Pb collision data at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV recorded with the ALICE detector. The non-identical particle correlations probe the spatio-temporal separation between sources of different particle species as well as the average source size of the emitting system. The sizes of the pion and kaon sources increase with centrality, and pions are emitted closer to the centre of the system and/or later than kaons. This is naturally expected in a system with strong radial flow and is qualitatively reproduced by hydrodynamic models. ALICE data on pion-kaon emission asymmetry are consistent with (3+1)-dimensional viscous hydrodynamics coupled to a statistical hadronization model, resonance propagation, and decay code THERMINATOR 2 calculation, with an additional time delay between 1 and 2 fm$/c$ for kaons. The delay can be interpreted as evidence for a significant hadronic rescattering phase in heavy-ion collisions at the LHC.

   nucl-exhep-exPLB(2021)·38 citations
3. 03*

   Search for $hep$ solar neutrinos and the diffuse supernova neutrino background using all three phases of the Sudbury Neutrino Observatory

   B. Aharmim🇨🇦 · S. N. Ahmed🇨🇦 · A. E. Anthony🇺🇸 · N. Barros🇵🇹 · E. W. Beier🇺🇸 · A. Bellerive🇨🇦 · B. Beltran🇨🇦 · M. Bergevin🇺🇸 · S. D. Biller🇬🇧 · E. Blucher🇺🇸 · R. Bonventre🇺🇸 · K. Boudjemline🇨🇦 and 120 other authors

   A search has been performed for neutrinos from two sources, the $hep$ reaction in the solar $pp$ fusion chain and the ${\nu }_e$ component of the diffuse supernova neutrino background (DSNB), using the full dataset of the Sudbury Neutrino Observatory with a total exposure of 2.47 kton-years after fiducialization. The $hep$ search is performed using both a single-bin counting analysis and a likelihood fit. We find a best-fit flux that is compatible with solar model predictions while remaining consistent with zero flux, and set a one-sided upper limit of ${\Phi }_{hep}<30\times 10^3{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$ [90% credible interval (CI)]. No events are observed in the DSNB search region, and we set an improved upper bound on the ${\nu }_e$ component of the DSNB flux of ${\Phi }_{{\nu }_e}^{\mathrm{DSNB}}<19{\text{cm}}^{-2}{\text{s}}^{-1}$ (90% CI) in the energy range $22.9<E_{\nu }<36.9$~MeV.

   ↳ hep-exnucl-exPRD(2020)·31 citations
4. 04*

   Second-forbidden nonunique ${\beta }^{-}$ decays of ${}^{24}$Na and ${}^{36}$Cl assessed by the nuclear shell model

   Anil Kumar🇮🇳 · Praveen C. Srivastava🇮🇳 · Joel Kostensalo🇫🇮 · Jouni Suhonen🇫🇮

   We have performed a systematic study of the log$ft$ values, shape factors and electron spectra for the second-forbidden nonunique ${\beta }^{-}$ decays of ${}^{24}$Na$(4^{+}){\to }^{24}$Mg$(2^{+})$ and ${}^{36}$Cl$(2^{+}){\to }^{36}$Ar$(0^{+})$ transitions under the framework of the nuclear shell model. We have performed the shell model calculations in the $sd$ model space, using more recent microscopic effective interactions such as Daejeon16, chiral N3LO, and JISP16. These interactions are derived from the no-core shell model wave functions using Okubo-Lee-Suzuki transformation.For comparison, we have also shown the results obtain from the phenomenological USDB interaction. To test the predictive power of these interactions first we have computed low-lying energy spectra of parent and daughter nuclei involved in these transitions. The computed results for energy spectra, nuclear matrix elements, log$ft$ values, shape factors, electron spectra and decomposition of the integrated shape factor are reported and compare with the available experimental data.

   ↳ nucl-thnucl-exPRC(2020)·36 citations
5. 05*

   Coherent elastic neutrino-nucleus scattering: EFT analysis and nuclear responses

   Martin Hoferichter🇨🇭 · Javier Menéndez🇪🇸 · Achim Schwenk🇩🇪

   The cross section for coherent elastic neutrino-nucleus scattering (CE$\nu$NS) depends on the response of the target nucleus to the external current, in the Standard Model (SM) mediated by the exchange of a $Z$ boson. This is typically subsumed into an object called the weak form factor of the nucleus. Here, we provide results for this form factor calculated using the large-scale nuclear shell model for a wide range of nuclei of relevance for current CE$\nu$NS experiments, including cesium, iodine, argon, fluorine, sodium, germanium, and xenon. In addition, we provide the responses needed to capture the axial-vector part of the cross section, which does not scale coherently with the number of neutrons, but may become relevant for the SM prediction of CE$\nu$NS on target nuclei with nonzero spin. We then generalize the formalism allowing for contributions beyond the SM. In particular, we stress that in this case, even for vector and axial-vector operators, the standard weak form factor does not apply anymore, but needs to be replaced by the appropriate combination of the underlying nuclear structure factors. We provide the corresponding expressions for vector, axial-vector, but also (pseudo-)scalar, tensor, and dipole effective operators, including two-body-current effects as predicted from chiral effective field theory. Finally, we update the spin-dependent structure factors for dark matter scattering off nuclei according to our improved treatment of the axial-vector responses.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2020)·187 citations
6. 06*

   Near-threshold $K^{\ast }(892{)}^{+}$ meson production in the interaction of ${\pi }^{-}$ mesons with nuclei

   E. Ya. Paryev🇷🇺

   We study the inclusive strange vector meson $K^{\ast }(892{)}^{+}$ production in ${\pi }^{-}A$ reactions at near-threshold laboratory incident pion momenta of 1.4--2.0 GeV/c within a nuclear spectral function approach. The approach accounts for incoherent primary ${\pi }^{-}$ meson--proton ${\pi }^{-}p\to K^{\ast }(892{)}^{+}{\Sigma }^{-}$ production processes as well as the influence of the scalar $K^{\ast }(892{)}^{+}$--nucleus potential (or the $K^{\ast }(892{)}^{+}$ in-medium mass shift) on these processes. We calculate the absolute differential and total cross sections for the production of $K^{\ast }(892{)}^{+}$ mesons off carbon and tungsten nuclei at laboratory angles of 0${}^{\circ }$--45${}^{\circ }$ and at these momenta within five scenarios for the above shift. We show that the $K^{\ast }(892{)}^{+}$ momentum distributions and their excitation functions (absolute and relative) possess a high sensitivity to changes in the in-medium $K^{\ast }(892{)}^{+}$ mass shift in the low-momentum region of 0.1--0.6 GeV/c. Therefore, the measurement of such observables in a dedicated experiment at the GSI pion beam facility in the near-threshold momentum domain will allow to get valuable information on the $K^{\ast }(892{)}^{+}$ in-medium properties.

   ↳ nucl-thhep-phnucl-exCPC(2020)·6 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.