Wed·Apr 5, 2017Wednesday·April 5, 2017

1. 01*

   Workshop on High-Intensity Photon Sources (HIPS2017) Mini-Proceedings

   S. Ali · L. Allison · M. Amaryan · R. Benimiwattha · A. Camsonne · D. Day · P. Degtiarenko · D. Dutta · R. Ent · J.L. Goity · D. Hamilton · O. Hen and 30 other authors

   This workshop aimed at producing an optimized photon source concept with potential increase of scientific output at Jefferson Lab, and at refining the science for hadron physics experiments benefitting from such a high-intensity photon source. The workshop brought together the communities directly using such sources for photo-production experiments, or for conversion into $K_L$ beams. The combination of high precision calorimetry and high intensity photon sources greatly enhances scientific benefit to (deep) exclusive processes like wide-angle and time-like Compton scattering. Potential prospects of such a high-intensity source with modern polarized targets were also discussed. The availability of $K_L$ beams would open new avenues for hadron spectroscopy, for example for the investigation of "missing" hyperon resonances, with potential impact on QCD thermodynamics and on freeze-out both in heavy ion collisions and in the early universe.

   nucl-ex10 citations
2. 02*

   Multiplicity fluctuations in Ar+Sc collisions at the CERN SPS from NA61/SHINE

   Andrey Seryakov (for the NA61/SHINE Collaboration)🇷🇺

   Multiplicity fluctuations were investigated in Ar+Sc collisions at 13A, 19A, 30A, 40A, 75A, 150A GeV/c using the NA61/SHINE detector at the SPS. Centrality selection is based on the nucleon-spectator energy in the forward hemisphere as measured by the Projectile spectator detector. Preliminary results on the scaled variance {\omega} and the strongly intensive measure {\Omega} were obtained for the multiplicity distribution of all, negatively and positively charged hadrons. Results are discussed and compared with p+p results and Pb+Pb data of NA49 and EPOS 1.99 simulations.

   ↳ hep-exnucl-exActa Phys.Polon.Supp.(2017)·4 citations
3. 03*

   Relativistic effects in heavy-ion Coulomb scattering

   Ravinder Kumar🇺🇸 · C.A. Bertulani🇺🇸 · G. Robinson🇺🇸

   The role of relativistic corrections in Coulomb scattering of heavy ions at intermediate energy collisions ($E_{lab}\gtrsim 50$ MeV/n) is investigated by numerically solving a full set of coupled equations. We compare two methods, (a) one involving an exact account of interaction retardation with (b) a method based on the expansion of effective Lagrangians in powers of the ion velocities, $v/c$.Our study makes it possible to infer the relevance of kinematic corrections, retardation, and magnetic interactions such as the Darwin force. We show that analytical formulas are able to describe all aspects of experimental interest in relativistic effects in heavy-ion Coulomb scattering at intermediate energies without having to solve numerically the coupled equations.

   ↳ nucl-thnucl-exPRC(2017)·1 citation
4. 04*

   Evolution of the Reactor Antineutrino Flux and Spectrum at Daya Bay

   F. P. An🇨🇳 · A. B. Balantekin🇺🇸 · H. R. Band🇺🇸 · M. Bishai🇺🇸 · S. Blyth🇹🇼 · D. Cao🇨🇳 · G. F. Cao🇨🇳 · J. Cao🇨🇳 · Y. L. Chan🇨🇳 · J. F. Chang🇨🇳 · Y. Chang🇹🇼 · H. S. Chen🇨🇳 and 193 other authors

   The Daya Bay experiment has observed correlations between reactor core fuel evolution and changes in the reactor antineutrino flux and energy spectrum. Four antineutrino detectors in two experimental halls were used to identify 2.2 million inverse beta decays (IBDs) over 1230 days spanning multiple fuel cycles for each of six 2.9 GW${}_{\text{th}}$ reactor cores at the Daya Bay and Ling Ao nuclear power plants. Using detector data spanning effective ${}^{239}$Pu fission fractions, $F_{239}$, from 0.25 to 0.35, Daya Bay measures an average IBD yield, ${\bar{\sigma }}_f$, of $(5.90\pm 0.13)\times 10^{-43}$ cm${}^2$/fission and a fuel-dependent variation in the IBD yield, $d{\sigma }_f/d{F}_{239}$, of $(-1.86\pm 0.18)\times 10^{-43}$ cm${}^2$/fission. This observation rejects the hypothesis of a constant antineutrino flux as a function of the ${}^{239}$Pu fission fraction at 10 standard deviations. The variation in IBD yield was found to be energy-dependent, rejecting the hypothesis of a constant antineutrino energy spectrum at 5.1 standard deviations. While measurements of the evolution in the IBD spectrum show general agreement with predictions from recent reactor models, the measured evolution in total IBD yield disagrees with recent predictions at 3.1$\sigma$. This discrepancy indicates that an overall deficit in measured flux with respect to predictions does not result from equal fractional deficits from the primary fission isotopes ${}^{235}$U, ${}^{239}$Pu, ${}^{238}$U, and ${}^{241}$Pu. Based on measured IBD yield variations, yields of $(6.17\pm 0.17)$ and $(4.27\pm 0.26)\times 10^{-43}$ cm${}^2$/fission have been determined for the two dominant fission parent isotopes ${}^{235}$U and ${}^{239}$Pu. A 7.8% discrepancy between the observed and predicted ${}^{235}$U yield suggests that this isotope may be the primary contributor to the reactor antineutrino anomaly.

   ↳ hep-exnucl-exphysics.ins-detPRL(2017)·274 citations
5. 05*

   An accurate calculation of the nucleon axial charge with lattice QCD

   Evan Berkowitz🇺🇸 · David Brantley🇺🇸 · Chris Bouchard🇬🇧 · Chia Cheng Chang🇺🇸 · M. A. Clark🇺🇸 · Nicholas Garron🇬🇧 · Balint Joo🇺🇸 · Thorsten Kurth🇺🇸 · Chris Monahan🇺🇸 · Henry Monge-Camacho🇺🇸 · Amy Nicholson🇺🇸 · Kostas Orginos🇺🇸 and 3 other authors

   We report on a lattice QCD calculation of the nucleon axial charge, $g_A$, using Möbius Domain-Wall fermions solved on the dynamical $N_f=2+1+1$ HISQ ensembles after they are smeared using the gradient-flow algorithm. The calculation is performed with three pion masses, $m_{\pi }\sim \{310,220,130\}$ MeV. Three lattice spacings ($a\sim \{0.15,0.12,0.09\}$ fm) are used with the heaviest pion mass, while the coarsest two spacings are used on the middle pion mass and only the coarsest spacing is used with the near physical pion mass. On the $m_{\pi }\sim 220$ MeV, $a\sim 0.12$ fm point, a dedicated volume study is performed with $m_{\pi }L\sim \{3.22,4.29,5.36\}$. Using a new strategy motivated by the Feynman-Hellmann Theorem, we achieve a precise determination of $g_A$ with relatively low statistics, and demonstrable control over the excited state, continuum, infinite volume and chiral extrapolation systematic uncertainties, the latter of which remains the dominant uncertainty. Our final determination at 2.6\% total uncertainty is $g_A=1.278(21)(26)$, with the first uncertainty including statistical and systematic uncertainties from fitting and the second including model selection systematics related to the chiral and continuum extrapolation. The largest reduction of the second uncertainty will come from a greater number of pion mass points as well as more precise lattice QCD results near the physical pion mass.

   ↳ hep-lathep-phnucl-exnucl-th72 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.