Fri·Dec 13, 2019Friday·December 13, 2019

1. 01*

   Results of the MAJORANA DEMONSTRATOR's Search for Double-Beta Decay of ${}^{76}$Ge to Excited States of ${}^{76}$Se

   I.S. Guinn🇺🇸 · I.J. Arnquist🇺🇸 · F.T. Avignone III🇺🇸 · A.S. Barabash🇷🇺 · C.J. Barton🇺🇸 · F.E. Bertrand🇺🇸 · B. Bos🇺🇸 · M. Busch🇺🇸 · M. Buuck🇺🇸 · T.S. Caldwell🇺🇸 · Y-D. Chan🇺🇸 · C.D. Christofferson🇺🇸 and 48 other authors

   The MAJORANA DEMONSTRATOR is searching for double-beta decay of ${}^{76}$Ge to excited states (E.S.) in ${}^{76}$Se using a modular array of high purity Germanium detectors. ${}^{76}$Ge can decay into three E.S.s of ${}^{76}$Se. The E.S. decays have a clear event signature consisting of a $\beta \beta$-decay with the prompt emission of one or two $\gamma$-rays, resulting in with high probability in a multi-site event. The granularity of the DEMONSTRATOR detector array enables powerful discrimination of this event signature from backgrounds. Using 21.3 kg-y of isotopic exposure, the DEMONSTRATOR has set world leading limits for each E.S. decay, with 90% CL lower half-life limits in the range of $(0.56-2.1)\cdot 10^{24}$ y. In particular, for the $2\nu$ transition to the first $0^{+}$ E.S. of ${}^{76}$Se, a lower half-life limit of $0.68\cdot 10^{24}$ at 90% CL was achieved.

   nucl-exJ.Phys.Conf.Ser.(2020)·6 citations
2. 02*

   Jets as precision probes in electron-nucleus collisions at the Electron-Ion Collider

   Miguel Arratia🇺🇸 · Youqi Song🇺🇸 · Felix Ringer🇺🇸 · Barbara V. Jacak🇺🇸

   We discuss the prospects of using jets as precision probes in electron-nucleus collisions at the future Electron-Ion Collider. Jets produced in deep-inelastic scattering can be calibrated by a measurement of the scattered electron. Such electron-jet "tag and probe" measurements call for an approach that is orthogonal to most HERA jet measurements as well as previous studies of jets at the future EIC. We present observables such as the electron-jet momentum balance, azimuthal correlations and jet substructure, which can provide constraints on the parton transport coefficient in nuclei. We compare simulations and analytical calculations and provide estimates of the expected medium effects. Implications for detector design at the future EIC are discussed.

   nucl-exhep-exhep-phnucl-thPRC(2020)·66 citations
3. 03*

   ${}^{78}$Ni revealed as a doubly magic stronghold against nuclear deformation

   R. Taniuchi🇯🇵 · C. Santamaria🇫🇷 · P. Doornenbal🇯🇵 · A. Obertelli🇫🇷 · K. Yoneda🇯🇵 · G. Authelet🇫🇷 · H. Baba🇯🇵 · D. Calvet🇫🇷 · F. Château🇫🇷 · A. Corsi🇫🇷 · A. Delbart🇫🇷 · J.-M. Gheller🇫🇷 and 59 other authors

   Nuclear magic numbers, which emerge from the strong nuclear force based on quantum chromodynamics, correspond to fully occupied energy shells of protons, or neutrons inside atomic nuclei. Doubly magic nuclei, with magic numbers for both protons and neutrons, are spherical and extremely rare across the nuclear landscape. While the sequence of magic numbers is well established for stable nuclei, evidence reveals modifications for nuclei with a large proton-to-neutron asymmetry. Here, we provide the first spectroscopic study of the doubly magic nucleus ${}^{78}$Ni, fourteen neutrons beyond the last stable nickel isotope. We provide direct evidence for its doubly magic nature, which is also predicted by ab initio calculations based on chiral effective field theory interactions and the quasi-particle random-phase approximation. However, our results also provide the first indication of the breakdown of the neutron magic number 50 and proton magic number 28 beyond this stronghold, caused by a competing deformed structure. State-of-the-art phenomenological shell-model calculations reproduce this shape coexistence, predicting further a rapid transition from spherical to deformed ground states with ${}^{78}$Ni as turning point.

   nucl-exnucl-thNature(2019)·186 citations
4. 04*

   Comment on "Direct Observation of Proton Emission in ${}^{11}$Be"

   H.O.U. Fynbo🇩🇰 · Z. Janas🇵🇱 · C. Mazzocchi🇵🇱 · M. Pfuetzner🇵🇱 · J. Refsgaard · K. Riisager🇩🇰 · N. Sokolowska

   We argue that conclusions of [PRL 123, 082501 (2019)] are incorrect. The authors present the direct observation of beta-delayed proton emission in the beta decay of 11Be. From the determined branching ratio for this process and from the energy spectrum of emitted protons the existence of a so far unobserved narrow resonance in 11Be was deduced. The given beta strength for the transition to this state is however wrong. In addition, we show that the combination of peak position and branching ratio is in strong disagreement with models considered by the authors. Furthermore, we identify several deficiencies in the analysis, and we provide possible sources of background, that could explain the error.

   nucl-exnucl-th3 citations
5. 05*

   Towards an ab initio theory for the temperature dependence of electric-field gradient in solids: application to hexagonal lattices of Zn and Cd

   A. V. Nikolaev🇷🇺 · N. M. Chtchelkatchev🇷🇺 · D. A. Salamatin🇷🇺 · A. V. Tsvyashchenko🇷🇺

   Based on ab initio band structure calculations we formulate a general theoretical method for description of the temperature dependence of electric field gradient in solids. The method employs a procedure of averaging multipole electron density component (l \neq 0) inside a sphere vibrating with the nucleus at its center. As a result of averaging each Fourier component (K \neq 0) on the sphere is effectively reduced by the square root of the Debye-Waller factor [exp(-W)]. The electric field gradient related to a sum of K-components most frequently decreases with temperature (T), but under certain conditions because of the interplay between terms of opposite signs it can also increase with T. The method is applied to calculations of the temperature evolution of the electric field gradients of pristine zinc and cadmium crystallized in the hexagonal lattice. For calculations within our model of crucial importance is the temperature dependence of mean-square displacements which can be taken from experiment or obtained from the phonon modes in the harmonic approximation. For the case of Zn we have used data obtained from single crystal x-ray diffraction. In addition, for Zn and Cd we have calculated mean-square displacements with the density functional perturbation treatment of the Quantum Espresso package. With the experimental data for displacements in Zn our calculations reproduce the temperature dependence of the electric field gradient very accurately. Within the harmonic approximation of the Quantum Espresso package the decrease of electric field gradients in Zn and Cd with temperature is overestimated. Our calculations indicate that the anharmonic effects are of considerable importance in the temperature dependence of electric field gradients.

   ↳ cond-mat.mtrl-scicond-mat.othernucl-exPRB(2020)·1 citation
6. 06*

   Issues with Search for Critical Point in QCD with Relativistic Heavy Ion Collisions

   Masayuki Asakawa🇯🇵 · Masakiyo Kitazawa🇯🇵 · Berndt Müller🇺🇸

   A systematic search for a critical point in the phase diagram of QCD matter is underway at the Relativistic Heavy Ion Collider (RHIC) and is planned at several future facilities. Its existence, if confirmed, and its location will greatly enhance our understanding of QCD. In this note we emphasize several important issues that are often not fully recognized in theoretical interpretations of experimental results relevant to the critical point search. We discuss ways in which our understanding on these issues can be improved.

   ↳ nucl-thhep-phnucl-exPRC(2020)·18 citations
7. 07*

   Lepton-Nucleus Cross Section Measurements for DUNE with the LDMX Detector

   Artur M. Ankowski🇺🇸 · Alexander Friedland🇺🇸 · Shirley Weishi Li🇺🇸 · Omar Moreno🇺🇸 · Philip Schuster🇺🇸 · Natalia Toro🇺🇸 · Nhan Tran🇺🇸

   We point out that the LDMX (Light Dark Matter eXperiment) detector design, conceived to search for sub-GeV dark matter, will also have very advantageous characteristics to pursue electron-nucleus scattering measurements of direct relevance to the neutrino program at DUNE and elsewhere. These characteristics include a 4-GeV electron beam, a precision tracker, electromagnetic and hadronic calorimeters with near 2$\pi$ azimuthal acceptance from the forward beam axis out to $\sim$40${}^{\circ }$ angle, and low reconstruction energy threshold. LDMX thus could provide (semi)exclusive cross section measurements, with detailed information about final-state electrons, pions, protons, and neutrons. We compare the predictions of two widely used neutrino generators (GENIE, GiBUU) in the LDMX region of acceptance to illustrate the large modeling discrepancies in electron-nucleus interactions at DUNE-like kinematics. We argue that discriminating between these predictions is well within the capabilities of the LDMX detector.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2020)·31 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.