Mon·Apr 10, 2017Monday·April 10, 2017

1. 01*

   Probing Proton Spin Structure: A Measurement of g2p at Four-momentum Transfer of 2 to 6 GeV^2

   James Davis Maxwell🇺🇸

   The Spin Asymmetries of the Nucleon Experiment investigated the spin structure of the proton via inclusive electron scattering at the Continuous Electron Beam Accelerator Facility at Jefferson Laboratory in Newport News, VA. A double--polarization measurement of polarized asymmetries was performed using the University of Virginia solid polarized ammonia target with target polarization aligned longitudinal and near transverse to the electron beam, allowing the extraction of the spin asymmetries $A_1$ and $A_2$, and spin structure functions $g_1$ and $g_2$. Polarized electrons of energies of 4.7 and 5.9 GeV were scattered to be viewed by a novel, non-magnetic array of detectors observing a four-momentum transfer range of 2 to 6 GeV${}^2$. This document addresses the extraction of the spin asymmetries and spin structure functions, with a focus on spin structure function $g_2$, which we have measured as a function of $x$ and $W$ in four $Q^2$ bins.

   nucl-exphysics.ins-det1 citation
2. 02*

   Vorticity in the QGP liquid and $\Lambda$ polarization at the RHIC Beam Energy Scan

   Iu. Karpenko🇺🇦 · F. Becattini🇮🇹

   Polarization of $\Lambda$ hyperons and their antiparticles is calculated in a 3+1 dimensional viscous hydrodynamic model with initial state from UrQMD hadron/string cascade. We find that, along with recent results from STAR, the mean polarization at fixed centrality decreases as a function of collision energy from 1.5% at $\sqrt{s_{\mathrm{NN}}}=7.7$ GeV to 0.2% at $\sqrt{s_{\mathrm{NN}}}=200$ GeV. We explore the effects which lead to such collision energy dependence, feed-down corrections and a difference between $\Lambda$ and $\bar{\Lambda }$.

   ↳ nucl-thhep-phnucl-exNPA(2017)·20 citations
3. 03*

   Transition from vibrational to rotational characters in low-lying states of hypernuclei

   H. Mei🇯🇵 · K. Hagino🇯🇵 · J. M. Yao🇺🇸 · T. Motoba🇯🇵

   In order to clarify the nature of hypernuclear low-lying states, we carry out a comprehensive study for the structure of ${}_{\Lambda }^{144-154}$Sm-hypernuclei, which exhibit a transition from vibrational to rotational characters as the neutron number increases. To this end, we employ a microscopic particle-core coupling scheme based on a covariant density functional theory. We find that the positive-parity ground-state band in the hypernuclei shares a similar structure to that of the corresponding core nucleus. That is, regardless of whether the core nucleus is spherical or deformed, each hypernuclear state is dominated by the single configuration of the $\Lambda$ particle in the $s_{1/2}$ state ($\Lambda s_{1/2}$) coupled to one core state of the ground band. In contrast, the low-lying negative-parity states mainly consist of $\Lambda p_{1/2}$ and $\Lambda p_{3/2}$ configurations coupled to plural nuclear core states. We show that, while the mixing amplitude between these configurations is negligibly small in spherical and weakly-deformed nuclei, it strongly increases as the core nucleus undergoes a transition to a well-deformed shape, being consistent with the Nilsson wave functions. We demonstrate that the structure of these negative-parity states with spin $I$ can be well understood based on the $LS$ coupling scheme, with the total orbital angular momentum of $L=[I\otimes 1]$ and the spin angular momentum of $S=1/2$.

   ↳ nucl-thnucl-exPRC(2017)·7 citations
4. 04*

   Improved Determination of the ${}^{235}\text{U}$ and ${}^{239}\text{Pu}$ Reactor Antineutrino Cross Sections per Fission

   Carlo Giunti🇮🇹

   We present the results of a combined fit of the reactor antineutrino rates and the Daya Bay measurement of ${\sigma }_{f,235}$ and ${\sigma }_{f,239}$. The combined fit leads to a better determination of the two cross sections per fission: ${\sigma }_{f,235}=6.29\pm 0.08$ and ${\sigma }_{f,239}=4.24\pm 0.21$ in units of $10^{-43}{\text{cm}}^2/\text{fission}$, with respective uncertainties of about $1.2\%$ and $4.9\%$. Since the respective deviations from the theoretical cross sections per fission are $2.5\sigma$ and $0.7\sigma$, we conclude that, if the reactor antineutrino anomaly is not due to active-sterile neutrino oscillations, it is likely that it can be solved with a revaluation of the ${}^{235}\text{U}$ reactor antineutrino flux. However, the ${}^{238}\text{U}$, ${}^{239}\text{Pu}$, and ${}^{241}\text{Pu}$ fluxes, which have larger uncertainties, could also be significantly different from the theoretical predictions.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2017)·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.