Tue·Jan 24, 2023Tuesday·January 24, 2023

1. 01*

   A new direct detection electron scattering experiment to search for the X17 particle

   D. Dutta (1) · H. Gao (2) · A. Gasparian (3) · T. J. Hague (3 and 4) · N. Liyanage (5) · R. Paremuzyan (6) · C. Peng (7) · W. Xiong (8) · P. Achenbach (6) · A. Ahmidouch (3) · S. Ali (5) · H. Avakian (6) and 49 other authors

   A new electron scattering experiment (E12-21-003) to verify and understand the nature of hidden sector particles, with particular emphasis on the so-called X17 particle, has been approved at Jefferson Lab. The search for these particles is motivated by new hidden sector models introduced to account for a variety of experimental and observational puzzles: excess in $e^{+}{e}^{-}$ pairs observed in multiple nuclear transitions, the 4.2$\sigma$ disagreement between experiments and the standard model prediction for the muon anomalous magnetic moment, and the small-scale structure puzzle in cosmological simulations. The aforementioned X17 particle has been hypothesized to account for the excess in $e^{+}{e}^{-}$ pairs observed from the ${}^8$Be M1, ${}^4$He M0, and, most recently, ${}^{12}$C E1 nuclear transitions to their ground states observed by the ATOMKI group. This experiment will use a high resolution electromagnetic calorimeter to search for or set new limits on the production rate of the X17 and other hidden sector particles in the $3-60$ MeV mass range via their $e^{+}{e}^{-}$ decay (or $\gamma \gamma$ decay with limited tracking). In these models, the $1-100$ MeV mass range is particularly well-motivated and the lower part of this range still remains unexplored. Our proposed direct detection experiment will use a magnetic-spectrometer-free setup (the PRad apparatus) to detect all three final state particles in the visible decay of a hidden sector particle for an effective control of the background and will cover the proposed mass range in a single setting. The use of the well-demonstrated PRad setup allows for an essentially ready-to-run and uniquely cost-effective search for hidden sector particles in the $3-60$ MeV mass range with a sensitivity of 8.9$\times$10${}^{-8}$ - 5.8$\times$10${}^{-9}$ to ${ϵ}^2$, the square of the kinetic mixing interaction constant between hidden and visible sectors.

   nucl-ex7 citations
2. 02*

   Neutron lifetime anomaly and mirror matter theory

   Wanpeng Tan🇺🇸

   This paper reviews the puzzles in modern neutron lifetime measurements and related unitarity issues in the CKM matrix. It is not a comprehensive and unbiased compilation of all historic data and studies, but rather a focus on compelling evidence leading to new physics. In particular, the largely overlooked nuances of different techniques applied in material and magnetic trap experiments are clarified. Further detailed analysis shows that the ``beam'' approach of neutron lifetime measurements is likely to give the ``true'' $\beta$-decay lifetime, while discrepancies in ``bottle'' measurements indicate new physics at play. The most feasible solution to these puzzles is a newly proposed ordinary-mirror neutron ($n-n^{\prime }$) oscillation model under the framework of mirror matter theory. This phenomenological model is reviewed and introduced, and its explanations of the neutron lifetime anomaly and possible non-unitarity of the CKM matrix are presented. Most importantly, various new experimental proposals, especially lifetime measurements with small/narrow magnetic traps or under super-strong magnetic fields, are discussed in order to test the surprisingly large anomalous signals that are uniquely predicted by this new $n-n^{\prime }$ oscillation model.

   nucl-exUniverse(2023)·13 citations
3. 03*

   Separating signal from combinatorial jets in a high background environment

   P. Steffanic🇺🇸 · C. Hughes🇺🇸 · C. Nattrass🇺🇸

   We study procedures for discriminating combinatorial jets in a high background environment, such as a heavy ion collision, from signal jets arising from a hard-scattering. We investigate a population of jets clustered from a combined PYTHIA+TennGen event, focusing on jets which can unambiguously be classified as signal or combinatorial jets. By selecting jets based on their kinematic properties, we investigate whether it is possible to separate signal and combinatorial jets without biasing the signal population significantly. We find that, after a loose selection on the jet area, surviving combinatorial jets are dominantly imposters, combinatorial jets with properties indistinguishable from signal jets. We also find that, after a loose selection on the leading hadron momentum, surviving combinatorial jets are still dominantly imposters. We use rule extraction, a machine learning technique, to extract an optimal kinematic selection from a random forest trained on our population of jets. In general, this technique found a stricter kinematic selection on the jet's leading hadron momentum to be optimal. We find that it is possible to suppress combinatorial jets significantly using this machine learning based selection, but that some signal is removed as well. Due to this stricter kinematic selection, we find that the surviving signal is biased towards quark-like jets. Since similar selections are used in many measurements, this indicates that those measurements are biased towards quark-like jets as well. These studies should motivate an increased emphasis on assumptions made when suppressing and subtracting combinatorial background and the biases introduced by methods for doing so.

   ↳ hep-phnucl-exPRC(2023)·4 citations
4. 04*

   STRASSE: A Silicon Tracker for Quasi-free Scattering Measurements at the RIBF

   H. N. Liu🇩🇪 · F. Flavigny🇫🇷 · H. Baba🇯🇵 · M. Boehmer🇩🇪 · U. Bonnes🇩🇪 · V. Borshchov🇺🇦 · P. Doornenbal🇯🇵 · N. Ebina🇯🇵 · M. Enciu🇩🇪 · A. Frotscher🇩🇪 · R. Gernhäuser🇩🇪 · V. Girard-Alcindor🇫🇷 and 26 other authors

   STRASSE (Silicon Tracker for RAdioactive nuclei Studies at SAMURAI Experiments) is a new detection system under construction for quasi-free scattering (QFS) measurements at 200-250 MeV/nucleon at the RIBF facility of the RIKEN Nishina Center. It consists of a charged-particle silicon tracker coupled with a dedicated thick liquid hydrogen target (up to 150-mm long) in a compact geometry to fit inside large scintillator or germanium arrays. Its design was optimized for two types of studies using QFS: missing-mass measurements and in-flight prompt $\gamma$-ray spectroscopy. This article describes (i) the resolution requirements needed to go beyond the sensitivity of existing systems for these two types of measurements, (ii) the conceptual design of the system using detailed simulations of the setup and (iii) its complete technical implementation and challenges. The final tracker aims at a sub-mm reaction vertex resolution and is expected to reach a missing-mass resolution below 2 MeV in $\sigma$ for $(p,2p)$ reactions when combined with the CsI(Na) CATANA array.

   ↳ physics.ins-detnucl-exEPJA(2023)·10 citations
5. 05*

   Measurement of cosmic-ray muon spallation products in a xenon-loaded liquid scintillator with KamLAND

   KamLAND-Zen Collaboration: S. Abe🇯🇵 · S. Asami🇯🇵 · M. Eizuka🇯🇵 · S. Futagi🇯🇵 · A. Gando🇯🇵 · Y. Gando🇯🇵 · T. Gima🇯🇵 · A. Goto🇯🇵 · T. Hachiya🇯🇵 · K. Hata🇯🇵 · K. Hosokawa🇯🇵 · K. Ichimura🇯🇵 and 53 other authors

   Cosmic-ray muons produce various radioisotopes when passing through material. These spallation products can be backgrounds for rare event searches such as in solar neutrino, double-beta decay, and dark matter search experiments. The KamLAND-Zen experiment searches for neutrinoless double-beta decay in 745kg of xenon dissolved in liquid scintillator. The experiment includes dead-time-free electronics with a high efficiency for detecting muon-induced neutrons. The production yields of different radioisotopes are measured with a combination of delayed coincidence techniques, newly developed muon reconstruction and xenon spallation identification methods. The observed xenon spallation products are consistent with results from the FLUKA and Geant4 simulation codes.

   ↳ hep-exnucl-exphysics.ins-detPRC(2023)·19 citations
6. 06*

   Nuclear three-body short-range correlations in coordinate space

   Ronen Weiss🇺🇸 · Stefano Gandolfi🇺🇸

   We study the effects of three-nucleon short-range correlations on nuclear coordinate-space densities. For this purpose, novel three-body densities are calculated for ground state nuclei using the auxiliary-field diffusion Monte Carlo method. The results are analyzed in terms of the Generalized Contact Formalism, extended to include three-body correlations, revealing the universal behavior of nucleon triplets at short distances. We identify the quantum numbers of such correlated triplets and extract scaling factors of triplet abundances that can be compared to upcoming inclusive electron scattering data.

   ↳ nucl-thnucl-exPRC(2023)·5 citations
7. 07*

   Understanding Jet Charge

   Zhong-Bo Kang🇺🇸 · Andrew J. Larkoski🇺🇸 · Jinghong Yang🇨🇳

   The jet charge is an old observable that has proven uniquely useful for discrimination of jets initiated by different flavors of light quarks, for example. In this Letter, we propose an approach to understanding the jet charge by establishing simple, robust assumptions that hold to good approximation non-perturbatively, such as isospin conservation and large particle multiplicity in the jets, forgoing any attempt at a perturbative analysis. From these assumptions, the jet charge distribution with fixed particle multiplicity takes the form of a Gaussian by the central limit theorem and whose mean and variance are related to fractional-power moments of single particle energy distributions. These results make several concrete predictions for the scaling of the jet charge with the multiplicity, explaining many of the results already in the literature, and new results we validate in Monte Carlo simulation.

   ↳ hep-phhep-exnucl-exnucl-thPRL(2023)·22 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.