Mon·Nov 21, 2022Monday·November 21, 2022

1. 01*

   Negative heat capacity for hot nuclei: confirmation with formulation from the microcanonical ensemble

   B. Borderie · S. Piantelli · J. D. Frankland · N. Le Neindre

   By using freeze-out properties of multifragmenting hot nuclei produced in quasifusion central ${}^{129}$Xe+${}^{nat}$Sn collisions at different beam energies (32, 39, 45 and 50 AMeV) which were estimated by means of a simulation based on experimental data collected by the $4\pi$ INDRA multidetector, heat capacity in the thermal excitation energy range 4 - 12.5 AMeV was calculated from total kinetic energies and multiplicities at freeze-out. The microcanonical formulation was employed. Negative heat capacity which indicates a first order phase transition for finite systems is observed and confirms previous results using a different method.

   nucl-exnucl-thNuovo Cim.C(2022)·0 citations
2. 02*

   Ground and excited quarkonium states as probes of MPI in small systems with ALICE

   Theraa Tork (for the ALICE collaboration)🇫🇷

   Quarkonia represent excellent tools for understanding the role of multiparton interactions (MPI) in small systems, i.e., pp and p-A collisions. Probing MPI with quarkonia can be done directly by looking at quarkonium associated production, or indirectly by studying the multiplicity dependence of quarkonium production. In these proceedings, the results from the ALICE experiment on direct and indirect MPI probes are discussed. The self-normalized yields of charmonium production as a function of the charged-particle multiplicity in pp and p--Pb collisions at \sqrt{s} = 13 TeV and \sqrt{s_{NN} = 8.16 TeV, respectively, are discussed. Additionally, the corresponding measurements of the charmonium self-normalized excited-to-ground state ratio as a function of the charged-particle multiplicity are reported. The new measurement of the double J/\psi production at forward rapidity in pp collisions at \sqrt{s} = 13 TeV TeV is presented. Finally, the multiplicity dependence of the bottomonium production in pp collisions at \sqrt{s} = 13 TeV is discussed. The comparison to the available theoretical calculations is reported.

   nucl-exhep-exPoS(2022)·0 citations
3. 03*

   A new avenue in the search for CP violation: Moessbauer spectroscopy of 227-Ac

   M.Scheck · R. Chapman · J.Dobaczewski · C.Ederer · P.Ivanov · G.Lorusso · D.O'Donnell · Ch.Schroeder

   This work proposes a new avenue in the search for CP-violating odd-electric and even-magnetic nuclear moments. A promising candidate to find such moments in the ground state is the quadrupole-deformed and octupole-correlated nucleus 227-actinium. In this nucleus, the 27.4-keV $E1$~transition that connects the $3/2^{+}$ parity-doublet partner and the $3/2^{-}$ ground state is perfectly suited to apply the sensitive technique of recoil-free selfabsorption, commonly known as Mössbauer spectroscopy. In this experimental approach, the lifetime of the $3/2^{+}$ upper parity-doublet partner allows an estimate of the lower limit of $\Delta E=2\cdot {\Gamma }_{\gamma }$= $23.7(1)\times 10^{-9}$ eV for the achievable energy resolution to be made. This resolution must be exceeded by the interaction of a CP-violating moment and the corresponding multipole moment of the field distribution in the lattice. This work presents the first ideas for patterns caused by CP-violating moments on the expected quadrupole splitting and nuclear Zeeman effect.

   nucl-exnucl-thEPJA(2023)·6 citations
4. 04*

   Rare ${}^{40}$K decay with implications for fundamental physics and geochronology

   M. Stukel🇨🇦 · L. Hariasz🇨🇦 · P.C.F. Di Stefano🇨🇦 · B.C. Rasco🇺🇸 · K.P. Rykaczewski🇺🇸 · N.T. Brewer🇺🇸 · D.W. Stracener🇺🇸 · Y. Liu🇺🇸 · Z. Gai🇺🇸 · C. Rouleau🇺🇸 · J. Carter🇺🇸 · J. Kostensalo🇫🇮 and 15 other authors

   Potassium-40 is a widespread, naturally occurring isotope whose radioactivity impacts subatomic rare-event searches, nuclear structure theory, and estimated geological ages. A predicted electron-capture decay directly to the ground state of argon-40 has never been observed. The KDK (potassium decay) collaboration reports strong evidence of this rare decay mode. A blinded analysis reveals a non-zero ratio of intensities of ground-state electron-captures ($I_{{\text{EC}}^0}$) over excited-state ones ($I_{\text{EC*}}$) of $I_{{\text{EC}}^0}/I_{\text{EC*}}=0.0095\stackrel{\text{stat}}{\pm }0.0022\stackrel{\text{sys}}{\pm }0.0010$ (68% C.L.), with the null hypothesis rejected at 4$\sigma$. In terms of branching ratio, this signal yields $I_{{\text{EC}}^0}=0.098\%\stackrel{\text{stat}}{\pm }0.023\%\stackrel{\text{sys}}{\pm }0.010\%$, roughly half of the commonly used prediction, with consequences for various fields [L. Hariasz et al., companion paper, DOI: 10.1103/PhysRevC.108.014327].

   nucl-exhep-exPRL(2023)·7 citations
5. 05*

   White Paper on the TUNL Nuclear Astrophysics Program

   Christian Iliadis🇺🇸 · Art E. Champagne🇺🇸 · Akaa D. Ayangeakaa🇺🇸 · Robert V. F. Janssens🇺🇸 · Richard Longland🇺🇸

   The White Paper describes the nuclear astrophysics program at the Triangle Universities Nuclear Laboratory (TUNL), with the intent of providing input for the 2023 NSAC Long Range planning process. TUNL is operated jointly by North Carolina Central University, North Carolina State University, The University of North Carolina at Chapel Hill, and Duke University. TUNL houses three world-class facilities for nuclear astrophysics research: the Laboratory for Experimental Nuclear Astrophysics (LENA); the Enge Magnetic Spectrograph; and the High-Intensity gamma-ray Source (HIgS). We discuss past successes, the present status, and future plans.

   nucl-ex1 citation
6. 06*

   Evidence for ground-state electron capture of ${}^{40}$K

   L. Hariasz🇨🇦 · M. Stukel🇨🇦 · P.C.F. Di Stefano🇨🇦 · B.C. Rasco🇺🇸 · K.P. Rykaczewski🇺🇸 · N.T. Brewer🇺🇸 · D.W. Stracener🇺🇸 · Y. Liu🇺🇸 · Z. Gai🇺🇸 · C. Rouleau🇺🇸 · J. Carter🇺🇸 · J. Kostensalo🇫🇮 and 15 other authors

   Potassium-40 is a widespread isotope whose radioactivity impacts estimated geological ages spanning billions of years, nuclear structure theory, and subatomic rare-event searches - including those for dark matter and neutrinoless double-beta decay. The decays of this long-lived isotope must be precisely known for its use as a geochronometer, and to account for its presence in low-background experiments. There are several known decay modes for ${}^{40}$K, but a predicted electron-capture decay directly to the ground state of argon-40 has never been observed, while theoretical predictions span an order of magnitude. The KDK Collaboration reports on the first observation of this rare decay, obtained using a novel combination of a low-threshold X-ray detector surrounded by a tonne-scale, high-efficiency $\gamma$-ray tagger at Oak Ridge National Laboratory. A blinded analysis reveals a distinctly nonzero ratio of intensities of ground-state electron-captures ($I_{{\text{EC}}^0}$) over excited-state ones ($I_{{\text{EC}}^{\ast }}$) of $I_{{\text{EC}}^0}/I_{{\text{EC}}^{\ast }}=0.0095\stackrel{\text{stat}}{\pm }0.0022\stackrel{\text{sys}}{\pm }0.0010$ (68% CL), with the null hypothesis rejected at 4$\sigma$ [Stukel et al., DOI:10.1103/PhysRevLett.131.052503]. This unambiguous signal yields a branching ratio of $I_{{\text{EC}}^0}=0.098\%\stackrel{\text{stat}}{\pm }0.023\%\stackrel{\text{sys}}{\pm }0.010$, roughly half of the commonly used prediction. This first observation of a third-forbidden unique electron capture improves understanding of low-energy backgrounds in dark-matter searches and has implications for nuclear-structure calculations. A shell-model based theoretical estimate for the $0\nu \beta \beta$ decay half-life of calcium-48 is increased by a factor of $7_{-2}^{+3}$. Our nonzero measurement shifts geochronological ages by up to a percent; implications are illustrated for Earth and solar system chronologies.

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

   Origin of the Proton Mass

   Craig D. Roberts🇨🇳

   Atomic nuclei lie at the core of everything visible; and at the first level of approximation, their atomic weights are simply the sum of the masses of all the neutrons and protons (nucleons) they contain. Each nucleon has a mass $m_N\approx 1\mathrm{GeV}\approx 2000$-times the electron mass. The Higgs boson -- discovered at the large hadron collider in 2012, a decade ago -- produces the latter, but what generates the nucleon mass? This is a pivotal question. The answer is widely supposed to lie within quantum chromodynamics (QCD), the strong-interaction piece of the Standard Model. Yet, it is far from obvious. In fact, removing Higgs-boson couplings into QCD, one arrives at a scale invariant theory, which, classically, can't support any masses at all. This contribution sketches forty years of developments in QCD, which suggest a solution to the puzzle, and highlight some of the experiments that can validate the picture.

   ↳ hep-phhep-exhep-latnucl-ex+1EPJ Web Conf.(2023)·25 citations
8. 08*

   Dispersive formalism for the nuclear structure correction ${\delta }_{\mathrm{NS}}$ to the $\beta$ decay rate

   Chien-Yeah Seng🇺🇸 · Mikhail Gorchtein🇩🇪

   We analyze the axial $\gamma W$-box diagram for $I(J^P)=1(0^{+})$ nuclei and provide a dispersion representation of the nuclear-structure correction ${\delta }_{\text{NS}}$ including its energy-dependent part. We also summarize useful isospin rotation formula and representations in nuclear theory that could facilitate the calculation of the parity-odd nuclear structure function $F_3(\nu ,Q^2)$. They provide a rigorous theory framework for the future, high-precision calculation of the nuclear structure correction ${\delta }_{\text{NS}}$ necessary for the extraction of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{ud}|$ from superallowed nuclear $\beta$ decays.

   ↳ nucl-thhep-exhep-lathep-ph+1PRC(2023)·41 citations
9. 09*

   Particle Physics at the European Spallation Source

   H. Abele🇦🇹 · A. Alekou🇨🇭 · A. Algora🇪🇸 · K. Andersen🇺🇸 · S. Baessler🇺🇸 · L. Barron-Palos🇲🇽 · J. Barrow🇺🇸 · E. Baussan🇫🇷 · P. Bentley🇸🇪 · Z. Berezhiani🇮🇹 · Y. Bessler🇩🇪 · A. K. Bhattacharyya🇸🇪 and 167 other authors

   Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world's brightest neutron source. As such, it has the potential for a particle physics program with a unique reach and which is complementary to that available at other facilities. This paper describes proposed particle physics activities for the ESS. These encompass the exploitation of both the neutrons and neutrinos produced at the ESS for high precision (sensitivity) measurements (searches).

   ↳ physics.ins-dethep-exhep-phnucl-exPhys.Rept.(2023)·66 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.