Mon·Jun 12, 2017Monday·June 12, 2017

1. 01*

   Prospect for Measuring $G_E^n$ at High Momentum Transfers

   B. Wojtsekhowski🇺🇸

   Experiment E02-013, approved by PAC21, will measure the neutron electric form factor at \qsq~up to 3.4 \gvsq, which is twice that achieved to date. The main features of the new experiment will be the use of the electron spectrometer BigBite, a large array of neutron detectors, and a polarized \he3~target. We present the parameters and optimization of the experimental setup. A concept of an experiment for \GEN~where precision \GEP~data is used for calibration of the systematics of a Rosenbluth type measurement is also discussed. A concept of the circulating gas flow in the polarized He${}^3$ target is presented.

   ↳ physics.ins-detnucl-ex2 citations
2. 02*

   Partial correlation analysis method in ultra-relativistic heavy-ion collisions

   Adam Olszewski🇵🇱 · Wojciech Broniowski🇵🇱

   We argue that statistical data analysis of two-particle longitudinal correlations in ultra-relativistic heavy-ion collisions may be efficiently carried out with the technique of partial covariance. In this method, the spurious event-by-event fluctuations due to imprecise centrality determination are eliminated via projecting out the component of the covariance influenced by the centrality fluctuations. We bring up the relationship of the partial covariance to the conditional covariance. Importantly, in the superposition approach, where hadrons are produced independently from a collection of sources, the framework allows us to impose centrality constraints on the number of sources rather than hadrons, that way unfolding of the trivial fluctuations from statistical hadronization and focusing better on the initial-state physics. We show, using simulated data from hydrodynamics followed with statistical hadronization, that the technique is practical and very simple to use, giving insight into the correlations generated in the initial stage. We also discuss the issues related to separation of the short- and long-range components of the correlation functions, and show that in our example the short-range component from the resonance decays is largely reduced by considering pions of the same sign. We demonstrate the method explicitly on the cases where centrality is determined with a single central control bin, or with two peripheral control bins.

   ↳ nucl-thnucl-exPRC(2017)·17 citations
3. 03*

   The nucleon spin and momentum decomposition using lattice QCD simulations

   C. Alexandrou (Univ. of Cyprus & Cyprus Inst.)🇨🇾 · M. Constantinou (Temple Univ.)🇺🇸 · K. Hadjiyiannakou (Cyprus Inst.)🇨🇾 · K. Jansen (DESY-Zeuthen)🇩🇪 · C. Kallidonis (Cyprus Inst.)🇨🇾 · G. Koutsou (Cyprus Inst.)🇨🇾 · A. Vaquero Avilés-Casco (Univ. of Utah)🇺🇸 · C. Wiese (DESY-Zeuthen)🇩🇪

   We determine within lattice QCD, the nucleon spin carried by valence and sea quarks, and gluons. The calculation is performed using an ensemble of gauge configurations with two degenerate light quarks with mass fixed to approximately reproduce the physical pion mass. We find that the total angular momentum carried by the quarks in the nucleon is $J_{u+d+s}=0.408(61{)}_{stat.}(48{)}_{syst.}$ and the gluon contribution is $J_g=0.133(11{)}_{stat.}(14{)}_{syst.}$ giving a total of $J_N=0.54(6{)}_{stat.}(5{)}_{syst.}$ consistent with the spin sum. For the quark intrinsic spin contribution we obtain $\frac{1}{2}\Delta {\Sigma }_{u+d+s}=0.201(17{)}_{stat.}(5{)}_{syst.}$. All quantities are given in the $\overline{\text{MS}}$ scheme at 2~GeV. The quark and gluon momentum fractions are also computed and add up to $⟨x{⟩}_{u+d+s}+⟨x{⟩}_g=0.804(121{)}_{stat.}(95{)}_{syst.}+0.267(12{)}_{stat.}(10{)}_{syst.}=1.07(12{)}_{stat.}(10{)}_{syst.}$ satisfying the momentum sum.

   ↳ hep-lathep-exhep-phnucl-ex+1PRL(2017)·172 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.