Thu·Dec 22, 2022Thursday·December 22, 2022

1. 01*

   Final Measurement of the U235 Antineutrino Energy Spectrum with the PROSPECT-I Detector at HFIR

   M. Adriamirado · A. B. Balantekin🇺🇸 · C. D. Bass🇺🇸 · D. E. Bergeron🇺🇸 · E. P. Bernard🇺🇸 · N. S. Bowden🇺🇸 · C. D. Bryan🇺🇸 · R. Carr🇺🇸 · T. Classen🇺🇸 · A. J. Conant🇺🇸 · G. Deichert🇺🇸 · A. Delgado🇺🇸 and 52 other authors

   This Letter reports one of the most precise measurements to date of the antineutrino spectrum from a purely U235-fueled reactor, made with the final dataset from the PROSPECT-I detector at the High Flux Isotope Reactor. By extracting information from previously unused detector segments, this analysis effectively doubles the statistics of the previous PROSPECT measurement. The reconstructed energy spectrum is unfolded into antineutrino energy and compared with both the Huber-Mueller model and a spectrum from a commercial reactor burning multiple fuel isotopes. A local excess over the model is observed in the 5MeV to 7MeV energy region. Comparison of the PROSPECT results with those from commercial reactors provides new constraints on the origin of this excess, disfavoring at 2.2 and 3.2 standard deviations the hypotheses that antineutrinos from U235 are solely responsible and non-contributors to the excess observed at commercial reactors respectively.

   nucl-exhep-exPRL(2023)·29 citations
2. 02*

   Angular distribution of $\gamma$-rays from a neutron-induced $p$-wave resonance of ${}^{132}$Xe

   T. Okudaira🇯🇵 · Y. Tani · S. Endo🇯🇵 · J. Doskow · H. Fujioka🇯🇵 · K. Hirota🇯🇵 · K. Kameda · A. Kimura🇯🇵 · M. Kitaguchi🇯🇵 · M. Luxnat🇺🇸 · K. Sakai🇯🇵 · D. Schaper🇺🇸 and 7 other authors

   A neutron-energy dependent angular distribution was measured for individual $\gamma$-rays from the 3.2 eV $p$-wave resonance of ${}^{131}$Xe+$n$, that shows enhanced parity violation owing to a mixing between $s$- and $p$-wave amplitudes. The $\gamma$-ray transitions from the $p$-wave resonance were identified, and the angular distribution with respect to the neutron momentum was evaluated as a function of the neutron energy for 7132 keV $\gamma$-rays, which correspond to a transition to the 1807 keV excited state of ${}^{132}$Xe. The angular distribution is considered to originate from the interference between $s$- and $p$-wave amplitudes, and will provide a basis for a quantitative understanding of the enhancement mechanism of the fundamental parity violation in compound nuclei.

   nucl-exPRC(2023)·5 citations
3. 03*

   Neutrinoless Double Beta Decay

   C. Adams🇺🇸 · K. Alfonso🇺🇸 · C. Andreoiu🇨🇦 · E. Angelico🇺🇸 · I.J. Arnquist🇺🇸 · J.A.A. Asaadi🇺🇸 · F.T. Avignone🇺🇸 · S. N. Axani🇺🇸 · A.S. Barabash🇷🇺 · P.S. Barbeau🇺🇸 · L. Baudis🇨🇭 · F. Bellini🇮🇹 and 220 other authors

   This White Paper, prepared for the Fundamental Symmetries, Neutrons, and Neutrinos Town Meeting related to the 2023 Nuclear Physics Long Range Plan, makes the case for double beta decay as a critical component of the future nuclear physics program. The major experimental collaborations and many theorists have endorsed this white paper.

   nucl-exnucl-th48 citations
4. 04*

   Search for Light Neutral Bosons in the TREK/E36 Experiment at J-PARC

   Dongwi H. Dongwi🇺🇸

   The Standard Model (SM) represents our best description of the subatomic world and it has been very successful in explaining how elementary particles interact under the influence of the fundamental forces. Despite its far reaching success in describing the building blocks of matter, the SM is still incomplete; falling short to explain dark matter, baryogenesis, neutrino masses and much more. The E36 experiment conducted at J-PARC in Japan, allows for sensitivity to search for light $U(1)$ gauge bosons, in the muonic $K^{+}$ decay channel. Such $U(1)$ bosons could be associated with dark matter or explain established muon-related anomalies such as the muon $g_{\mu }-2$ value, and the proton radius puzzle. A scintillating fiber target was used to stop a beam of positively charged $K$ mesons. The $K^{+}$ products were detected with a large-acceptance toroidal spectrometer capable of tracking charged particles with high resolution, combined with a large solid angle CsI(TI) photon detector and particle ID systems. A realistic simulation was employed to search for these rare decays in the mass range of 20$-$100 MeV/$c^2$. Preliminary results of the upper limits for the $A^{\prime }$ branching ratio $\mathcal{B}r(A^{\prime })$ extracted at 95\% CL, will be discussed.

   ↳ hep-exnucl-exJ.Phys.Conf.Ser.(2022)·3 citations
5. 05*

   High Power Cyclotrons: The Bridge Between Beyond the Standard Model Physics, Computation, and Medical Applications

   Loyd Waites🇺🇸

   The IsoDAR cyclotron is a 60 MeV cyclotron designed to output 10mA of protons in order to be a driver for a neutrino experiment. Coupling the high flux generated by the IsoDAR system with a kiloton neutrino detector will provide sterile neutrino exclusion searches covering anomalous regions indicated by short baseline experiments. Simultaneously, the coupling of a high power target and kiloton detector allows for the investigation of dark matter candidates, namely axion-like particles. We have shown that nuclear excitations within the IsoDAR target create a unique opportunity to produce axions and detect monoenergetic peaks with the nearby kiloton detector. Beyond this, the high power produced by the IsoDAR cyclotron can be used for applications beyond particle physics. The IsoDAR cyclotron accelerates and extracts H${}_2^{+}$, which allows the beam to be split downstream, a versatile and important development to alleviate the problem of producing high-power targets for the medical isotope community. This thesis presents a proposal for production of an more than an order of magnitude higher rates than are available at present for certain highly-need medical isotopes, including Ac-225. In this thesis, we report results from a multi-cusp ion source that meets these requirements and produces a record level of high purity, low emittance H${}_2^{+}$ current. The second has been to design a radio-frequency quadrupole (RFQ) that will allow for gentle bunching of the high current before injection. This is the first use of axial direct injection with a compact cyclotron. This thesis reports the first application of machine learning to the RFQ design. These tools enable the high currents required by IsoDAR cyclotron, leading to important impact on the accelerator, medical, and physics communities.

   ↳ physics.acc-phhep-exnucl-ex2 citations
6. 06*

   Measurement of ${}^{nat}$Pb(${\nu }_e$,X$n$) production with a stopped-pion neutrino source

   COHERENT Collaboration · P. An · C. Awe · P.S. Barbeau · B. Becker · S.W. Belling · V. Belov · I. Bernardi · C. Bock · A. Bolozdynya · R. Bouabid · A. Brown and 75 other authors

   Using neutrinos produced at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL), the COHERENT collaboration has studied the Pb(${\nu }_e$,X$n$) process with a lead neutrino-induced-neutron (NIN) detector. Data from this detector are fit jointly with previously collected COHERENT data on this process. A combined analysis of the two datasets yields a cross section that is $0.29_{-0.16}^{+0.17}$ times that predicted by the MARLEY event generator using experimentally-measured Gamow-Teller strength distributions, consistent with no NIN events at 1.8$\sigma$. This is the first inelastic neutrino-nucleus process COHERENT has studied, among several planned exploiting the high flux of low-energy neutrinos produced at the SNS.

   ↳ hep-exnucl-exPRD(2023)·27 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.