Mon·Jan 30, 2023Monday·January 30, 2023

1. 01*

   ${}^{138}\mathrm{Ba}(d,\alpha )$ study of states in ${}^{136}\mathrm{Cs}$: Implications for new physics searches with xenon detectors

   B. M. Rebeiro🇿🇦 · S. Triambak🇿🇦 · P. E. Garrett🇨🇦 · G. C. Ball🇨🇦 · B. A. Brown🇺🇸 · J. Menéndez🇪🇸 · B. Romeo🇪🇸 · P. Adsley🇺🇸 · B. G. Lenardo🇺🇸 · R. Lindsay🇿🇦 · V. Bildstein🇨🇦 · C. Burbadge🇨🇦 and 12 other authors

   We used the ${}^{138}$Ba$(d,\alpha )$ reaction to carry out an in-depth study of states in ${}^{136}$Cs, up to around 2.5~MeV. In this work, we place emphasis on hitherto unobserved states below the first $1^{+}$ level, which are important in the context of solar neutrino and fermionic dark matter (FDM) detection in large-scale xenon experiments. We identify for the first time candidate metastable states in ${}^{136}$Cs, which would allow a real-time detection of solar neutrino and FDM events in xenon detectors, with high background suppression. Our results are also compared with shell-model calculations performed with three Hamiltonians that were previously used to evaluate the nuclear matrix element (NME) for ${}^{136}$Xe neutrinoless double beta decay. We find that one of these Hamiltonians, which also systematically underestimates the NME compared to the others, dramatically fails to describe the observed low-energy ${}^{136}$Cs spectrum, while the other two show reasonably good agreement.

   nucl-exPRL(2023)·14 citations
2. 02*

   Investigation of the ${\mathbf{\Sigma }}^0$ Production Mechanism in p(3.5 GeV)+p Collisions

   R. Abou Yassine🇩🇪 · O. Arnold🇩🇪 · M. Becker🇩🇪 · P. Bergmann🇩🇪 · A. Blanco🇵🇹 · C. Blum🇩🇪 · M. Böhmer🇩🇪 · N. Carolino🇵🇹 · L. Chlad🇨🇿 · P. Chudoba🇨🇿 · I. Ciepał🇵🇱 · J. Dreyer🇩🇪 and 79 other authors

   The production of ${\Sigma }^0$ hyperons in proton proton collisions at a beam kinetic energy of 3.5 GeV impinging on a liquid hydrogen target was investigated using data collected with the HADES setup. The total production cross section is found to be $\sigma (\mathrm{p}{\mathrm{K}}^{+}{\mathrm{\Sigma }}^0)[\mu \mathrm{b}]=17.7\pm 1.7(\mathrm{stat})\pm 1.6(\mathrm{syst})$. Differential cross section distributions of the exclusive channel $\mathrm{pp}\to \mathrm{p}{\mathrm{K}}^{+}{\mathrm{\Sigma }}^0$ were analyzed in the center-of-mass, Gottfried-Jackson and helicity reference frames for the first time at the excess energy of 556 MeV. The data support the interplay between pion and kaon exchange mechanisms and clearly demonstrate the contribution of interfering nucleon resonances decaying to ${\mathrm{K}}^{+}{\mathrm{\Sigma }}^0$. The Bonn-Gatchina partial wave analysis was employed to analyse the data. Due to the limited statistics, it was not possible to obtain an unambiguous determination of the relative contribution of intermediate nucleon resonances to the final state. However nucleon resonances with masses around 1.710 $GeV/{\mathrm{c}}^2$ (${\mathrm{N}}^{\ast }(1710)$) and 1.900 $GeV/{\mathrm{c}}^2$ (${\mathrm{N}}^{\ast }(1900)$ or ${\mathrm{\Delta }}^{\ast }(1900)$) are preferred by the fit.

   nucl-exEPJA(2024)·7 citations
3. 03*

   Observation of low-lying isomeric states in ${}^{136}$Cs: a new avenue for dark matter and solar neutrino detection in xenon detectors

   Scott J. Haselschwardt🇺🇸 · Brian G. Lenardo🇺🇸 · Timothy Daniels🇺🇸 · Sean W. Finch🇺🇸 · Forrest Q. L. Friesen🇺🇸 · Calvin R. Howell🇺🇸 · Collin R. Malone🇺🇸 · Ethan Mancil🇺🇸 · Werner Tornow🇺🇸

   We report on new measurements establishing the existence of low-lying isomeric states in ${}^{136}$Cs using $\gamma$ rays produced in ${}^{136}$Xe(p,n)${}^{136}$Cs reactions. Two states with $\mathcal{O}(100)$~ns lifetimes are placed in the decay sequence of the ${}^{136}$Cs levels that are populated in charged-current interactions of solar neutrinos and fermionic dark matter with ${}^{136}$Xe. Xenon-based experiments can therefore exploit a delayed-coincidence tag of these interactions, greatly suppressing backgrounds to enable spectroscopic studies of solar neutrinos and dark matter.

   nucl-exhep-exPRL(2023)·9 citations
4. 04*

   Particle Interferometry in a Moat Regime

   Fabian Rennecke🇩🇪 · Robert D. Pisarski🇺🇸 · Dirk H. Rischke🇩🇪

   Dense strongly interacting matter can exhibit regimes with spatial modulations, akin to crystalline phases. In this case particles can have a moat spectrum with minimal energy at nonzero momentum. We show that particle interferometry is a sensitive probe of such a regime in heavy-ion collisions. To this end, we develop a field-theoretical formalism that relates particle spectra to in-medium real-time correlation functions of quantum fields on curved hypersurfaces of spacetime. This is then applied to the study of Bose-Einstein correlations in a moat regime in heavy-ion collisions. The resulting two-particle spectra exhibit peaks at nonzero average pair momentum, in contrast to the two-particle spectra in a normal phase, which peak at zero momentum. These peaks lead to non-trivial structures in the ratio of two-particle correlation functions, which should be experimentally measurable if the resolution in the direction of average pair momentum is sufficiently large. We propose these structures in the correlation-function ratios as clear signature of a moat regime and spatially modulated phases in quantum chromodynamics (QCD).

   ↳ hep-phnucl-exnucl-thPRD(2023)·38 citations
5. 05*

   Time-of-flight spectroscopy of ultracold neutrons at the PSI UCN source

   G. Bison🇨🇭 · W. Chen🇨🇭 · P.-J. Chiu🇨🇭 · M. Daum🇨🇭 · C. B. Doorenbos🇨🇭 · K. Kirch🇨🇭 · V. Kletzl🇨🇭 · B. Lauss🇨🇭 · D. Pais🇨🇭 · I. Rienäcker🇨🇭 · P. Schmidt-Wellenburg🇨🇭 · G. Zsigmond🇨🇭

   The ultracold neutron (UCN) source at the Paul Scherrer Institute (PSI) provides high intensities of storable neutrons for fundamental physics experiments. The neutron velocity spectrum parallel to the beamline axis was determined by time-of-flight spectroscopy using a neutron chopper. In particular, the temporal evolution of the spectrum during neutron production and UCN storage in the source storage volume was investigated and compared to Monte Carlo simulation results. A softening of the measured spectrum from a mean velocity of 7.7(1) m s${}^{-1}$ to 5.1(1) m s${}^{-1}$ occurred within the first 30 s after the proton beam pulse had impinged on the spallation target. A spectral hardening was observed over longer time scales of one measurement day, consistent with the effect of surface degradation of the solid deuterium moderator.

   ↳ physics.ins-detnucl-exEPJA(2023)·7 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.