Mon·Nov 17, 2014Monday·November 17, 2014

1. 01*

   The Neutron Lifetime

   F. E. Wietfeldt🇺🇸

   The decay of the free neutron into a proton, electron, and antineutrino is the prototype semileptonic weak decay and the simplest example of nuclear beta decay. The nucleon vector and axial vector weak coupling constants G_V and G_A determine the neutron lifetime as well as the strengths of weak interaction processes involving free neutrons and protons that are important in astrophysics, cosmology, solar physics and neutrino detection. In combination with a neutron decay angular correlation measurement, the neutron lifetime can be used to determine the first element of the CKM matrix Vud. Unfortunately the two main experimental methods for measuring the neutron lifetime currently disagree by almost 4 sigma. I will present a brief review of the status of the neutron lifetime and prospects for the future.

   nucl-ex13 citations
2. 02*

   Proton Charge Radius and Precision Tests of QED

   Jan C. Bernauer🇺🇸

   The "proton radius puzzle" remains unsolved since it was established in 2010. This paper summarizes the current state and gives an overview over upcoming experiments.

   nucl-exhep-phnucl-th5 citations
3. 03*

   Two-neutrino double-beta decay of ${}^{150}$Nd to excited final states in ${}^{150}$Sm

   Mary F. Kidd🇺🇸 · James H. Esterline🇺🇸 · Sean W. Finch🇺🇸 · Werner Tornow🇺🇸

   Double-beta decay is a rare nuclear process in which two neutrons in the nucleus are converted to two protons with the emission of two electrons and two electron anti-neutrinos. We measured the half life of the two-neutrino double-beta decay of ${}^{150}$Nd to excited final states of ${}^{150}$Sm by detecting the de-excitation gamma rays of the daughter nucleus. This study yields the first detection of the coincidence gamma rays from the 0${}_1^{+}$ excited state of ${}^{150}$Sm. These gamma rays have energies of 333.97 keV and 406.52 keV, and are emitted in coincidence through a 0${}_1^{+}\to$2${}_1^{+}\to$0${}_{gs}^{+}$ transition. The enriched Nd${}_2$O${}_3$ sample consisted of 40.13 g ${}^{150}$Nd and was observed for 642.8 days at the Kimballton Underground Research Facility, producing 21.6 net events in the region of interest. This count rate gives a half life of $T_{1/2}=(1.07_{-0.25}^{+0.45}(stat)\pm 0.07(syst.))\times 10^{20}$ years. The effective nuclear matrix element was found to be 0.0465${}_{-0.0054}^{+0.0098}$. Finally, lower limits were obtained for decays to higher excited final states. Our half-life measurement agrees within uncertainties with another recent measurement in which no coincidence was employed. Our nuclear matrix element calculation may have an impact on a recent neutrinoless double-beta decay nuclear matrix element calculation which implies the decay to the first excited state in ${}^{150}$Sm is favored over that to the ground state.

   nucl-exphysics.ins-detPRC(2014)·40 citations
4. 04*

   Consistency of Perfect Fluidity and Jet Quenching in semi-Quark-Gluon Monopole Plasmas

   Jiechen Xu🇺🇸 · Jinfeng Liao🇺🇸 · Miklos Gyulassy🇺🇸

   We utilize a new framework, CUJET3.0, to deduce the energy and temperature dependence of jet transport parameter, $\hat{q}(E>10\mathrm{GeV},T)$, from a combined analysis of available data on nuclear modification factor and azimuthal asymmetries from RHIC/BNL and LHC/CERN on high energy nuclear collisions. Extending a previous perturbative-QCD based jet energy loss model (known as CUJET2.0) with (2+1)D viscous hydrodynamic bulk evolution, this new framework includes three novel features of nonperturbative physics origin: (1) the Polyakov loop suppression of color-electric scattering (aka "semi-QGP" of Pisarski et al) and (2) the enhancement of jet scattering due to emergent magnetic monopoles near $T_c$ (aka "magnetic scenario" of Liao and Shuryak) and (3) thermodynamic properties constrained by lattice QCD data. CUJET3.0 reduces to v2.0 at high temperatures $T>400$ MeV, but greatly enhances $\hat{q}$ near the QCD deconfinement transition temperature range. This enhancement accounts well for the observed elliptic harmonics of jets with $p_T>10$ GeV. Extrapolating our data-constrained $\hat{q}$ down to thermal energy scales, $E\sim 2$ GeV, we find for the first time a remarkable consistency between high energy jet quenching and bulk perfect fluidity with $\eta /s\sim T^3/\hat{q}\sim 0.1$ near $T_c$.

   ↳ hep-phnucl-exnucl-thChin.Phys.Lett.(2015)·139 citations
5. 05*

   Systematic Investigation of Negative Cooper-Frye Contributions in Heavy Ion Collisions Using Coarse-grained Molecular Dynamics

   D. Oliinychenko🇺🇦 · P.Huovinen🇩🇪 · H. Petersen🇩🇪

   In most heavy ion collision simulations involving relativistic hydrodynamics, the Cooper-Frye formula is applied to transform the hydrodynamical fields to particles. In this article the so-called negative contributions in the Cooper-Frye formula are studied using a coarse-grained transport approach. The magnitude of negative contributions is investigated as a function of hadron mass, collision energy in the range of $E_{\mathrm{lab}}=5$--$160A$ GeV, collision centrality and the energy density transition criterion defining the hypersurface. The microscopic results are compared to negative contributions expected from hydrodynamical treatment assuming local thermal equilibrium. The main conclusion is that the number of actual microscopic particles flying inward is smaller than the negative contribution one would expect in an equilibrated scenario. The largest impact of negative contributions is found to be on the pion rapidity distribution at midrapidity in central collisions. For this case negative contributions in equilibrium constitute 8--13\% of positive contributions depending on collision energy, but only 0.5--4\% in cascade calculation. The dependence on the collision energy itself is found to be non-monotonous with a maximum at 10-20$A$ GeV.

   ↳ nucl-thhep-phnucl-exPRC(2015)·18 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.