Fri·Apr 26, 2019Friday·April 26, 2019

1. 01*

   First observation of two-neutrino double electron capture in ${}^{124}$Xe with XENON1T

   E. Aprile · J. Aalbers · F. Agostini · M. Alfonsi · L. Althueser · F. D. Amaro · M. Anthony · V. C. Antochi · F. Arneodo · L. Baudis · B. Bauermeister · M. L. Benabderrahmane and 119 other authors

   Two-neutrino double electron capture ($2\nu$ECEC) is a second-order Weak process with predicted half-lives that surpass the age of the Universe by many orders of magnitude. Until now, indications for $2\nu$ECEC decays have only been seen for two isotopes, ${}^{78}$Kr and ${}^{130}$Ba, and instruments with very low background levels are needed to detect them directly with high statistical significance. The $2\nu$ECEC half-life provides an important input for nuclear structure models and its measurement represents a first step in the search for the neutrinoless double electron capture processes ($0\nu$ECEC). A detection of the latter would have implications for the nature of the neutrino and give access to the absolute neutrino mass. Here we report on the first direct observation of $2\nu$ECEC in ${}^{124}$Xe with the XENON1T Dark Matter detector. The significance of the signal is $4.4\sigma$ and the corresponding half-life $T_{1/2}^{2\nu \text{ECEC}}=(1.8\pm 0.5_{\text{stat}}\pm 0.1_{\text{sys}})\times 10^{22}\text{y}$ is the longest ever measured directly. This study demonstrates that the low background and large target mass of xenon-based Dark Matter detectors make them well suited to measuring other rare processes as well, and it highlights the broad physics reach for even larger next-generation experiments.

   nucl-exNature(2019)·181 citations
2. 02*

   Gai Reply to Comment by Schumann et al. (arXiv:1904.03023v1)

   Moshe Gai🇺🇸

   Statements included in the comment published by Schumann et al. (arXiv:1904.03023v1) are contradicted by documents that were communicated to one of the co-authors of the comment (Dr. Koester). These documents are reviewed but cannot be disclosed here due to copyright (they are available on request). A summary of the scientific dispute between the collaboration and Dr. Schumann, was submitted on September 24, 2018, to the Directorate Support of the Paul Scherrer Institute (PSI) and can be provided on request.

   nucl-ex0 citations
3. 03*

   Implications of the mass $M=2.17_{-0.10}^{+0.11}$M${}_{\odot }$ of PSR~J0740+6620 on the Equation of State of Super-Dense Neutron-Rich Nuclear Matter

   Nai-Bo Zhang🇨🇳 · Bao-An Li🇺🇸

   We study implications of the very recently reported mass $M=2.17_{-0.10}^{+0.11}$M${}_{\odot }$ of PSR~J0740+6620 on the Equation of State (EOS) of super-dense neutron-rich nuclear matter with respect to existing constraints on the EOS based on the mass $M=2.01\pm 0.04$M${}_{\odot }$ of PSR~J0348+0432, the maximum tidal deformability of GW170817 and earlier results of various terrestrial nuclear laboratory experiments. The lower limit of the skewness $J_0$ measuring the stiffness of super-dense isospin-symmetric nuclear matter is raised raised from about -220 MeV to -150 MeV, reducing significantly its current uncertainty range. The lower bound of the high-density symmetry energy also increases appreciably leading to a rise of the minimum proton fraction in neutron stars at $\beta$-equilibrium from about 0 to 5\% around three times the saturation density of nuclear matter. The difficulties for some of the most widely used and previously well tested model EOSs to predict simultaneously both a maximum mass higher than 2.17 M${}_{\odot }$ and a pressure consistent with that extracted from GW170817 present some interesting new challenges for nuclear theories.

   ↳ nucl-thastro-ph.HEgr-qcnucl-exApJ(2019)·81 citations
4. 04*

   Causal hydrodynamic fluctuations in non-static and inhomogeneous backgrounds

   Koichi Murase🇯🇵

   To integrate hydrodynamic fluctuations, namely thermal fluctuations of hydrodynamics, into dynamical models of high-energy nuclear collisions based on relativistic hydrodynamics, the property of the hydrodynamic fluctuations given by the fluctuation-dissipation relation should be carefully investigated. The fluctuation-dissipation relation for causal dissipative hydrodynamics with the finite relaxation time is naturally given in the integral form of the constitutive equation by the linear-response theory. While, the differential form of the constitutive equation is commonly used in analytic investigations and dynamical calculations for practical reasons. We give the fluctuation-dissipation relation for the general linear-response differential form and discuss the restrictions to the structure of the differential form, which comes from the causality and the positive semi-definiteness of the noise autocorrelation, and also the relation of those restrictions to the cutoff scale of the hydrodynamic fluctuations. We also give the fluctuation-dissipation relation for the integral form in non-static and inhomogeneous background by introducing new tensors, the pathline projectors. We find new modification terms to the fluctuation-dissipation relation for the differential form in non-static and inhomogeneous background which are particularly important in dynamical models to describe rapidly expanding systems.

   ↳ nucl-thhep-phnucl-exAnnals Phys.(2019)·19 citations
5. 05*

   Determining the Diffusivity for Light Quarks from Experiment

   Scott Pratt🇺🇸 · Chris Plumberg🇸🇪

   Charge balance functions reflect the evolution of charged pair correlations throughout the stages of pair production, dynamical diffusion, and hadronization in heavy-ion collisions. Microscopic modeling of these correlations in the full collision volume shows that the balance functions are sensitive to the diffusivity of light quarks when studied as functions of relative azimuthal angle. By restricting our analysis to K+,K- and p,pbar pairs, we find that the diffusivity of light quarks, a fundamental property not currently well understood, can be constrained by experimental measurement.

   ↳ nucl-thnucl-exPRC(2020)·35 citations
6. 06*

   The muon intensity in the Felsenkeller shallow underground laboratory

   F. Ludwig🇩🇪 · L. Wagner🇩🇪 · T. Al-Abdullah · G. G. Barnaföldi🇭🇺 · D. Bemmerer🇩🇪 · D. Degering🇩🇪 · K. Schmidt🇫🇷 · G. Surányi · T. Szücs🇩🇪 · K. Zuber🇩🇪

   The muon intensity and angular distribution in the shallow-underground laboratory Felsenkeller in Dresden, Germany have been studied using a portable muon detector based on the close cathode chamber design. Data has been taken at four positions in Felsenkeller tunnels VIII and IX, where a new 5 MV underground ion accelerator is being installed, and in addition at four positions in Felsenkeller tunnel IV, which hosts a low-radioactivity counting facility. At each of the eight positions studied, seven different orientations of the detector were used to compile a map of the upper hemisphere with 0.85{\deg} angular resolution. The muon intensity is found to be suppressed by a factor of 40 due to the 45 m thick rock overburden, corresponding to 140 meters water equivalent. The angular data are matched by two different simulations taking into account the known geodetic features of the terrain: First, simply by determining the cutoff energy using the projected slant depth in rock and the known muon energy spectrum, and second, in a Geant4 simulation propagating the muons through a column of rock equal to the known slant depth. The present data are instrumental for studying muon-induced effects at these depths and also in the planning of an active veto for accelerator-based underground nuclear astrophysics experiments.

   ↳ physics.ins-detnucl-exAstropart.Phys.(2019)·17 citations
7. 07*

   Neutrino event generators: foundation, status and future

   Ulrich Mosel🇩🇪

   Neutrino event generators are an essential tool needed for the extraction of neutrino mixing parameters, the mass hierarchy and a CP violating phase from long-baseline experiments. In this article I first describe the theoretical basis and the approximations needed to get to present-days generators. I also discuss the strengths and limitations of theoretical models used to describe semi-inclusive neutrino-nucleus reactions. I then confront present day's generators with this theoretical basis by detailed discussions of the various reaction processes. Finally, as examples I then show for various experiments results of the generator GiBUU for lepton semi-inclusive cross sections as well as particle spectra. I also discuss features of these cross sections in terms of the various reaction components, with predictions for DUNE. Finally, I argue for the need for a new neutrino generator that respects our present-day knowledge of both nuclear theory and nuclear reactions and is as much state-of-the-art as the experimental equipment. I outline some necessary requirements for such a new generator.

   ↳ hep-exhep-phnucl-exnucl-thJ.Phys.G(2019)·75 citations
8. 08*

   Correlations far from equilibrium in charged strongly coupled fluids subjected to a strong magnetic field

   Casey Cartwright🇺🇸 · Matthias Kaminski🇺🇸

   Within a holographic model, we calculate the time evolution of 2-point and 1-point correlation functions (of selected operators) within a charged strongly coupled system of many particles. That system is thermalizing from an anisotropic initial charged state far from equilibrium towards equilibrium while subjected to a constant external magnetic field. One main result is that thermalization times for 2-point functions are significantly (approximately three times) larger than those of 1-point functions. Magnetic field and charge amplify this difference, generally increasing thermalization times. However, there is also a competition of scales between charge density, magnetic field, and initial anisotropy, which leads to an array of qualitative changes on the 2- and 1-point functions. There appears to be a strong effect of the medium on 2-point functions at early times, but approximately none at later times. At strong magnetic fields, an apparently universal thermalization time emerges, at which all 2-point functions appear to thermalize regardless of any other scale in the system. Hence, this time scale is referred to as saturation time scale. As extremality is approached in the purely charged case, 2- and 1-point functions appear to equilibrate at infinitely late time. We also compute 2-point functions of charged operators. Our results can be taken to model thermalization in heavy ion collisions, or thermalization in selected condensed matter systems.

   ↳ hep-thcond-mat.str-elhep-phnucl-ex+1JHEP(2019)·23 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.