Thu·Apr 7, 2016Thursday·April 7, 2016

1. 01*

   Time-reversal-invariance-violating nucleon-nucleon potential in the 1/N_c expansion

   Daris Samart🇹🇭 · Carlos Schat🇦🇷 · Matthias R. Schindler🇺🇸 · Daniel R. Phillips🇺🇸

   We apply the large-$N_c$ expansion to the time-reversal-invariance-violating (TV) nucleon-nucleon potential. The operator structures contributing to next-to-next-to-leading order in the large-$N_c$ counting are constructed. For the TV and parity-violating case we find a single operator structure at leading order. The TV but parity-conserving potential contains two leading-order terms, which however are suppressed by 1/$N_c$ compared to the parity-violating potential. Comparison with phenomenological potentials, including the chiral EFT potential in the TV parity-violating case, leads to large-$N_c$ scaling relations for TV meson-nucleon and nucleon-nucleon couplings.

   ↳ nucl-thhep-phnucl-exPRC(2016)·19 citations
2. 02*

   Evolving images of the proton: Hadron physics over the past 40 years

   Michael R. Pennington🇺🇸

   Once upon a time, the world was simple: the proton contained three quarks, two {\it ups} and a {\it down}. How these give the proton its mass and its spin seemed obvious. Over the past forty years the proton has become more complicated, and how even these most obvious of its properties is explained in a universe of quarks, antiquarks and gluons remains a challenge. That this should be so should come as no surprise. Quantum Chromodynamics, the theory of the strong interaction, is seemingly simple, and its consequences are straightforward in the domain of hard scattering where perturbation theory applies. However, the beauty of the hadron world is its diversity. The existence of hadrons, their properties, and their binding into nuclei do not appear in the Lagrangian of QCD. They all emerge as a result of its strong coupling. Strong coupling QCD creates complex phenomena, much richer than known 40 years ago: a richness that ensures colour confinement and accounts for more than 95\% of the mass of the visible Universe. How strong coupling QCD really works requires a synergy between experiment and theory. A very personal view of these fascinating developments in cold QCD is presented.

   ↳ hep-phhep-exnucl-exnucl-thJ.Phys.G(2016)·13 citations
3. 03*

   Radii of neutron drops probed via the neutron skin thickness of nuclei

   P. W. Zhao🇺🇸 · S. Gandolfi🇺🇸

   Multi-neutron systems are crucial to understanding the physics of neutron-rich nuclei and neutron stars. Neutron drops, neutrons confined in an external field, are investigated systematically in both non-relativistic and relativistic density functional theories and with ab initio calculations. We demonstrate a strong linear correlation, which is universal in the realm of mean-field models, between the rms radii of neutron drops and the neutron skin thickness of Pb-208 and Ca-48; i.e., the difference between the neutron and proton rms radii of a nucleus. Due to its high quality, this correlation can be used to deduce the radii of neutron drops from the measured neutron skin thickness in a model-independent way, and the radii obtained for neutron drops can provide a useful constraint for realistic three neutron forces. This correlation, together with high- precision measurements of the neutron skin thicknesses of Pb-208 and Ca-48, will have an enduring impact on the understanding of multi-neutron interactions, neutron-rich nuclei, neutron stars, etc.

   ↳ nucl-thnucl-exPRC(2016)·33 citations
4. 04*

   A measurement of the time profile of scintillation induced by low energy gamma-rays in liquid xenon with the XMASS-I detector

   XMASS Collaboration: H. Takiya🇯🇵 · K. Abe🇯🇵 · K. Hiraide🇯🇵 · K. Ichimura🇯🇵 · Y. Kishimoto🇯🇵 · K. Kobayashi🇯🇵 · M. Kobayashi🇯🇵 · S. Moriyama🇯🇵 · M. Nakahata🇯🇵 · T. Norita🇯🇵 · H. Ogawa🇯🇵 · H. Sekiya🇯🇵 and 27 other authors

   We report the measurement of the emission time profile of scintillation from gamma-ray induced events in the XMASS-I 832 kg liquid xenon scintillation detector. Decay time constant was derived from a comparison of scintillation photon timing distributions between the observed data and simulated samples in order to take into account optical processes such as absorption and scattering in liquid xenon. Calibration data of radioactive sources, ${}^{55}$Fe, ${}^{241}$Am, and ${}^{57}$Co were used to obtain the decay time constant. Assuming two decay components, ${\tau }_1$ and ${\tau }_2$, the decay time constant ${\tau }_2$ increased from 27.9 ns to 37.0 ns as the gamma-ray energy increased from 5.9 keV to 122 keV. The accuracy of the measurement was better than 1.5 ns at all energy levels. A fast decay component with ${\tau }_1\sim 2$ ns was necessary to reproduce data. Energy dependencies of ${\tau }_2$ and the fraction of the fast decay component were studied as a function of the kinetic energy of electrons induced by gamma-rays. The obtained data almost reproduced previously reported results and extended them to the lower energy region relevant to direct dark matter searches.

   ↳ physics.ins-detastro-ph.COhep-exnucl-exNucl.Instrum.Meth.A(2016)·27 citations
5. 05*

   Model for the Cherenkov light emission of TeO${}_2$ cryogenic calorimeters

   Nicola Casali🇮🇹

   The most sensitive process able to probe the Majorana nature of neutrinos and discover Lepton Number Violation is the neutrino-less double beta decay. Thanks to the excellent energy resolution, efficiency and intrinsic radio-purity, cryogenic calorimeters are primed for the search for this process. A novel approach able to improve the sensitivity of the current experiments is the rejection of $\alpha$ interactions, that represents the dominant background source. In TeO${}_2$ calorimeters, $\alpha$ particles can be tagged as, in contrast to electrons, they do not emit Cherenkov light. Nevertheless, the very low amount of detected Cherenkov light undermines the complete rejection of $\alpha$ background. In this paper we compare the results obtained in previous measurements of the TeO${}_2$ light yield with a detailed Monte Carlo simulation able to reproduce the number of Cherenkov photons produced in $\beta /\gamma$ interactions within the calorimeter and their propagation in the experimental set-up. We demonstrate that the light yield detectable from a $5\times 5\times 5$~cm${}^3$ TeO${}_2$ bolometer can be increased by up to 60% by increasing the surface roughness of the crystal and improving the light detector design. Moreover, we study the possibility to disentangle $\alpha$, $\beta$ and $\gamma$ interactions, which represent the ultimate background source. Unfortunately $\gamma$ rejection is not feasible but $\alpha$ rejection can be achieved exploiting high sensitivity light detectors.

   ↳ physics.ins-detnucl-exAstropart.Phys.(2017)·18 citations
6. 06*

   Measurement of the double-beta decay half-life and search for the neutrinoless double-beta decay of ${}^{48}\mathrm{Ca}$ with the NEMO-3 detector

   NEMO-3 Collaboration: R. Arnold (1) · C. Augier (2) · A.M. Bakalyarov (3) · J.D. Baker (4) · A.S. Barabash (5) · A. Basharina-Freshville (6) · S. Blondel (2) · S. Blot (7) · M. Bongrand (2) · V. Brudanin (8 and 9) · J. Busto (10) · A.J. Caffrey (4) and 87 other authors

   The NEMO-3 experiment at the Modane Underground Laboratory has investigated the double-$\beta$ decay of ${}^{48}\mathrm{Ca}$. Using $5.25$ yr of data recorded with a $6.99\mathrm{g}$ sample of ${}^{48}\mathrm{Ca}$, approximately $150$ double-$\beta$ decay candidate events have been selected with a signal-to-background ratio greater than $3$. The half-life for the two-neutrino double-$\beta$ decay of ${}^{48}\mathrm{Ca}$ has been measured to be $T_{1/2}^{2\nu }=[6.4{}_{-0.6}^{+0.7}(stat.){}_{-0.9}^{+1.2}(syst.)]\times 10^{19}\mathrm{yr}$. A search for neutrinoless double-$\beta$ decay of ${}^{48}\mathrm{Ca}$ yields a null result and a corresponding lower limit on the half-life is found to be $T_{1/2}^{0\nu }>2.0\times 10^{22}\mathrm{yr}$ at $90\%$ confidence level, translating into an upper limit on the effective Majorana neutrino mass of $<m_{\beta \beta }><6.0-26$ $\mathrm{eV}$, with the range reflecting different nuclear matrix element calculations. Limits are also set on models involving Majoron emission and right-handed currents.

   ↳ hep-exnucl-exphysics.ins-detPRD(2016)·129 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.