Mon·Jan 8, 2018Monday·January 8, 2018

1. 01*

   Separated Kaon Electroproduction Cross Section and the Kaon Form Factor from 6 GeV JLab Data

   M. Carmignotto🇺🇸 · S. Ali🇺🇸 · K. Aniol🇺🇸 · J. Arrington🇺🇸 · B. Barrett🇨🇦 · E.J. Beise🇺🇸 · H.P. Blok🇳🇱 · W. Boeglin🇺🇸 · E.J. Brash🇺🇸 · H. Breuer🇺🇸 · C.C. Chang🇺🇸 · M.E. Christy🇺🇸 and 48 other authors

   The ${}^{1}H$($e,e^{\prime }{K}^{+}$)$\Lambda$ reaction was studied as a function of the Mandelstam variable $-t$ using data from the E01-004 (FPI-2) and E93-018 experiments that were carried out in Hall C at the 6 GeV Jefferson Lab. The cross section was fully separated into longitudinal and transverse components, and two interference terms at four-momentum transfers $Q^2$ of 1.00, 1.36 and 2.07 GeV${}^2$. The kaon form factor was extracted from the longitudinal cross section using the Regge model by Vanderhaeghen, Guidal, and Laget. The results establish the method, previously used successfully for pion analyses, for extracting the kaon form factor. Data from 12 GeV Jefferson Lab experiments are expected to have sufficient precision to distinguish between theoretical predictions, for example recent perturbative QCD calculations with modern parton distribution amplitudes. The leading-twist behavior for light mesons is predicted to set in for values of $Q^2$ between 5-10 GeV${}^2$, which makes data in the few GeV regime particularly interesting. The $Q^2$ dependence at fixed $x$ and $-t$ of the longitudinal cross section we extracted seems consistent with the QCD factorization prediction within the experimental uncertainty.

   nucl-exPRC(2018)·38 citations
2. 02*

   Proton charge radius from electron scattering

   Ingo Sick🇨🇭

   The rms-radius $R$ of the proton charge distribution is a fundamental quantity needed for precision physics. This radius, traditionally determined from elastic electron-proton scattering via the slope of the Sachs form factor $G_e(q^2)$ extrapolated to momentum transfer $q^2$=0, shows a large scatter. We discuss the approaches used to analyze the e-p data, partly redo these analyses in order to identify the sources of the discrepancies, and explore alternative parameterizations. The problem lies in the model dependence of the parameterized $G(q)$ needed for the extrapolation. This shape of $G(q<q_{min})$ is closely related to the shape of the charge density $\rho (r)$ at large radii $r$, a quantity which is ignored in most analyses. When using our {\em physics} knowledge about this large-$r$ density together with the information contained in the high-$q$ data, the model dependence of the extrapolation is reduced and different parameterizations of the pre-2010 data yield a consistent value for $R=0.887\pm 0.012fm$. This value disagrees with the more precise value $0.8409\pm 0.0004fm$ determined from the Lamb shift in muonic hydrogen.

   nucl-exnucl-thAtoms(2018)·45 citations
3. 03*

   Bulk Properties of the Matter Produced at Energies of the Beam Energy Scan Program

   Yu. B. Ivanov🇷🇺 · A. A. Soldatov🇷🇺

   Recent STAR data on the bulk observables in the energy range of the Beam-Energy Scan Program at the Relativistic Heavy-Ion Collider are analyzed within the model of the three-fluid dynamics (3FD). The simulations are performed with different equations of state (EoS). The purely hadronic EoS fails to reproduce the data. A good, though imperfect, overall reproduction of the data is found within the deconfinement scenarios. The crossover EoS turns out to be slightly preferable. For this reproduction a fairly strong baryon stopping in the quark-gluon phase is required. The 3FD model does not need two separate freeze-outs (i.e. kinetic and chemical ones) to describe the STAR data. A unified freeze-out is applied at all energies.

   ↳ nucl-thhep-phnucl-exPRC(2018)·15 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.