Fri·Sep 23, 2022Friday·September 23, 2022

1. 01*

   Modeling Backgrounds for the MAJORANA DEMONSTRATOR

   C.R. Haufe🇺🇸 · I.J. Arnquist🇺🇸 · F.T. Avignone III🇺🇸 · A.S. Barabash🇷🇺 · C.J. Barton🇺🇸 · K.H. Bhimani🇺🇸 · E. Blalock🇺🇸 · B. Bos🇺🇸 · M. Busch🇺🇸 · M. Buuck🇺🇸 · T.S. Caldwell🇺🇸 · Y-D. Chan🇺🇸 and 46 other authors

   The MAJORANA DEMONSTRATOR is a neutrinoless double-beta decay ($0\nu \beta \beta$) experiment containing $\sim$30 kg of p-type point contact germanium detectors enriched to 88% in 76Ge and $\sim$14 kg of natural germanium detectors. The detectors are housed in two electroformed copper cryostats and surrounded by a graded passive shield with active muon veto. An extensive radioassay campaign was performed prior to installation to insure the use of ultra-clean materials. The DEMONSTRATOR achieved one of the lowest background rates in the region of the $0\nu \beta \beta$ Q-value, 15.7 $\pm$ 1.4 cts/(FWHM t y) from the low-background configuration spanning most of the 64.5 kg-yr active exposure. Nevertheless this background rate is a factor of five higher than the projected background rate. This discrepancy arises from an excess of events from the 232Th decay chain. Background model fits aim to understand this deviation from assay-based projections, potentially determine the source(s) of observed backgrounds, and allow a precision measurement of the two-neutrino double-beta decay half-life. The fits agree with earlier simulation studies, which indicate the origin of the 232Th excess is not from a near-detector component and have informed design decisions for the next-generation LEGEND experiment. Recent findings have narrowed the suspected locations for the excess activity, motivating a final simulation and assay campaign to complete the background model.

   nucl-exAIP Conf.Proc.(2023)·2 citations
2. 02*

   New anomaly observed in ${}^{12}$C supports the existence and the vector character of the hypothetical X17 boson

   A.J. Krasznahorkay🇭🇺 · A. Krasznahorkay🇭🇺 · M. Begala🇭🇺 · M. Csatlós🇭🇺 · L. Csige🇭🇺 · J. Gulyás🇭🇺 · A. Krakó🇭🇺 · J. Timár🇭🇺 · I. Rajta🇭🇺 · I. Vajda🇭🇺 · N.J. Sas🇭🇺

   Employing the ${}^{11}$B(p,$\gamma$)${}^{12}$C nuclear reaction, the angular correlation of $e^{+}{e}^{-}$ pairs was investigated in the angular range of $40^{\circ }\Theta \le 175^{\circ }$ for five different proton energies between E${}_p$ = 1.50 - 2.50 MeV. At small angles ($\Theta \le 120^{\circ }$), the results can be well interpreted by the internal pair creation process of electromagnetic radiations with E1 and M1 multipolarities and by the external pair creation in the target backing. However, at angles greater than $120^{\circ }$, additional count excess and anomalies were observed, which could be well accounted for by the existence of the previously suggested hypotetical X17 particle. Our results show that the X17 particle was generated mainly in E1 radiation. The derived mass of the particle is $m_{\mathrm{X}}{c}^2$=17.03$\pm 0.11(stat)\pm 0.20(syst)$ MeV. According to the mass, and to the derived branching ratio ($B_x=3.6(3)\times 10^{-6}$), this is likely the same X17 particle, which we recently suggested for describing the anomaly observed in the decay of ${}^8$Be and ${}^4$He.

   nucl-exhep-exPRC(2022)·118 citations
3. 03*

   Imaging the initial condition of heavy-ion collisions and nuclear structure across the nuclide chart

   Jiangyong Jia🇺🇸 · Giuliano Giacalone🇩🇪 · Benjamin Bally🇫🇷 · James Daniel Brandenburg🇺🇸 · Ulrich Heinz🇺🇸 · Shengli Huang🇺🇸 · Dean Lee · Yen-Jie Lee · Wei Li🇺🇸 · Constantin Loizides🇺🇸 · Matthew Luzum🇧🇷 · Govert Nijs🇺🇸 and 9 other authors

   High-energy nuclear collisions encompass three key stages: the structure of the colliding nuclei informed by low-energy nuclear physics, the initial condition (IC) leading to the formation of quark-gluon plasma (QGP), and the hydrodynamic expansion and hadronization of the QGP leading to final-state hadrons observed experimentally. Recent advances in experimental and theoretical methods have ushered in a precision era, enabling an increasingly accurate understanding of these stages. However, most approaches involve simultaneously determining both QGP properties and initial conditions from a single collision system, creating complexity due to the coupled contributions of various stages to the final-state observables. To avoid this, we propose leveraging known knowledge of low-energy nuclear structure and hydrodynamic observables to constrain the IC independently. By conducting comparative studies of collisions involving isobar-like nuclei - species with similar mass numbers but different structures - we disentangle the initial condition's impacts from the QGP properties. This approach not only refines our understanding of the IC but also turns high-energy experiments into a precision tool for imaging nuclear structures, offering insights that complement traditional low-energy approaches. Opportunities for carrying out such comparative experiments at the LHC and other facilities could significantly advance both high-energy and low-energy nuclear physics. Additionally, this approach has implications for the future EIC. While the possibilities are extensive, we focus on selected proposals that could benefit both the high-energy and low-energy nuclear physics communities. Originally prepared as input for the long-range plan of U.S. nuclear physics, this white paper reflects the status as of September 2022, with a brief update on developments since then.

   nucl-exhep-phnucl-thNucl.Sci.Tech.(2024)·128 citations
4. 04*

   Updated and novel limits on double beta decay and dark matter-induced processes in platinum

   B. Broerman🇨🇦 · M. Laubenstein🇮🇹 · S. Nagorny🇨🇦 · S. Nisi🇮🇹 · N. Song🇬🇧 · A.C. Vincent🇨🇦

   A 510 day long-term measurement of a 45.3 g platinum foil acting as the sample and high voltage contact in an ultra-low-background high purity germanium detector was performed at Laboratori Nazionali del Gran Sasso (Italy). The data was used for a detailed study of double beta decay modes in natural platinum isotopes. Limits are set in the range $\mathcal{O}(10^{14}-10^{19})$ yr (90% C.L.) for several double beta decay transitions to excited states confirming, and partially extending existing limits. The highest sensitivity of the measurement, greater than $10^{19}$ yr, was achieved for the two neutrino and neutrinoless double beta decay modes of the isotope ${}^{198}$Pt. Additionally, novel limits for inelastic dark matter scattering on ${}^{195}$Pt are placed up to mass splittings of approximately 500 keV. We analyze several techniques to extend the sensitivity and propose a few approaches for future medium-scale experiments with platinum-group elements.

   nucl-exEPJC(2023)·0 citations
5. 05*

   Charge Symmetry Breaking Effects on Neutron Beta Decay in Non-Relativistic Quark Models

   Jacob W. Crawford🇺🇸 · Gerald A. Miller🇺🇸

   A formalism for the study of charge symmetry breaking (CSB) effects is discussed and used to analyze the effects of charge symmetry breaking on neutron beta decay. The effect of including CSB reduces the beta decay matrix element by an amount on the order of $10^{-4}$, a value much larger than the previous estimate. A much smaller contribution due to proton recoil is treated as well, which is found to be on the order of $10^{-6}$. The current uncertainty in the value of $V_{ud}$ is also of order $10^{-4}$. An improvement of that uncertainty by an order of magnitude would require that charge symmetry breaking effects should be included in future analyses.

   ↳ nucl-thhep-phnucl-exPRC(2022)·9 citations
6. 06*

   Microscopic description of the torque acting on fission fragments

   Guillaume Scamps🇧🇪

   When two fragments are created in a fission decay, any torque due to nuclear and Coulomb interaction can change the fragment's angular momentum. This article explores the character and magnitude of the angular momentum as a function of the initial conditions around the scission point using the time-dependent Hartree-Fock theory. To understand the torque acting on the fragments, the Frozen Hartree-Fock method is also used to determine the collective potential at scission. Two ${}^{240}$Pu fission channel ( ${}^{132}$Sn+${}^{108}$Ru and ${}^{144}$Ba+${}^{96}$Sr ) are studied. These two channels cover different shapes (spherical, quadrupole, and octupole deformation) of the fragments. It is found that the angular momentum generated by the Coulomb interaction after fission is mainly collective, while this is not the case for the angular momentum generated at scission. The competition between rotational modes (bending, wriggling, and twisting) is discussed and shows that the angular momentum is generated mainly perpendicular to the fission axis.

   ↳ nucl-thnucl-exPRC(2022)·18 citations
7. 07*

   A Better Angle on Hadron Transverse Momentum Distributions at the EIC

   Anjie Gao🇺🇸 · Johannes K. L. Michel🇺🇸 · Iain W. Stewart🇺🇸 · Zhiquan Sun🇺🇸

   We propose an observable $q_{\ast }$ sensitive to transverse momentum dependence (TMD) in $eN\to ehX$, with $q_{\ast }/E_N$ defined purely by lab-frame angles. In 3D measurements of confinement and hadronization this resolves the crippling issue of accurately reconstructing small transverse momentum $P_{hT}$. We prove factorization for $\mathrm{d}{\sigma }_h/\mathrm{d}{q}_{\ast }$ for $q_{\ast }\ll Q$ with standard TMD functions, enabling $q_{\ast }$ to substitute for $P_{hT}$. A double-angle reconstruction method is given which is exact to all orders in QCD for $q_{\ast }\ll Q$. $q_{\ast }$ enables an order-of-magnitude improvement in the expected experimental resolution at the EIC.

   ↳ hep-phnucl-exnucl-thPRD(2023)·16 citations
8. 08*

   Resolving the Scales of the Quark-Gluon Plasma with Energy Correlators

   Carlota Andres🇫🇷 · Fabio Dominguez🇪🇸 · Raghav Kunnawalkam Elayavalli🇺🇸 · Jack Holguin🇫🇷 · Cyrille Marquet🇫🇷 · Ian Moult🇺🇸

   Jets provide us with ideal probes of the quark-gluon plasma (QGP) produced in heavy-ion collisions, since its dynamics at its different scales is imprinted into the multi-scale substructure of the final state jets. We present a new approach to jet substructure in heavy-ion collisions based on the study of correlation functions of energy flow operators. By analysing the two-point correlator of an in-medium quark jet, we demonstrate that the spectra of correlation functions robustly identify the scales defined by the properties of the QGP, particularly those associated with the onset of colour coherence.

   ↳ hep-phhep-exnucl-exnucl-thPRL(2023)·129 citations
9. 09*

   Design report of the KISS-II facility for exploring the origin of uranium

   Takamichi Aoki · Yoshikazu Hirayama · Hironobu Ishiyama · SunChan Jeong · Sota Kimura · Yasuhiro Makida🇯🇵 · Hiroari Miyatake · Momo Mukai · Shunji Nishimura🇯🇵 · Katsuhisa Nishio🇯🇵 · Toshitaka Niwase · Tatsuhiko Ogawa🇯🇵 and 5 other authors

   One of the critical longstanding issues in nuclear physics is the origin of the heavy elements such as platinum and uranium. The r-process hypothesis is generally supported as the process through which heavy elements are formed via explosive rapid neutron capture. Many of the nuclei involved in heavy-element synthesis are unidentified, short-lived, neutron-rich nuclei, and experimental data on their masses, half-lives, excited states, decay modes, and reaction rates with neutron etc., are incredibly scarce. The ultimate goal is to understand the origin of uranium. The nuclei along the pathway to uranium in the r-process are in "Terra Incognita". In principle, as many of these nuclides have more neutrons than 238U, this region is inaccessible via the in-flight fragmentation reactions and in-flight fission reactions used at the present major facilities worldwide. Therefore, the multi-nucleon transfer (MNT) reaction, which has been studied at the KEK Isotope Separation System (KISS), is attracting attention. However, in contrast to in-flight fission and fragmentation, the nuclei produced by the MNT reaction have characteristic kinematics with broad angular distribution and relatively low energies which makes them non-amenable to in-flight separation techniques. KISS-II would be the first facility to effectively connect production, separation, and analysis of nuclides along the r-process path leading to uranium. This will be accomplished by the use of a large solenoid to collect MNT products while rejecting the intense primary beam, a large helium gas catcher to thermalize the MNT products, and an MRTOF mass spectrograph to perform mass analysis and isobaric purification of subsequent spectroscopic studies. The facility will finally allow us to explore the neutron-rich nuclides in this Terra Incognita.

   ↳ physics.ins-detnucl-ex3 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.