Thu·Dec 18, 2014Thursday·December 18, 2014

1. 01*

   Separated Response Functions in Exclusive, Forward ${\pi }^{\pm }$ Electroproduction on Deuterium

   G.M. Huber · H.P. Blok · C. Butuceanu · D. Gaskell · T. Horn · D.J. Mack · D. Abbott · K. Aniol · H. Anklin · C. Armstrong · J. Arrington · K. Assamagan and 77 other authors

   Background: Measurements of forward exclusive meson production at different squared four-momenta of the exchanged virtual photon, $Q^2$, and at different four-momentum transfer, t, can be used to probe QCD's transition from meson-nucleon degrees of freedom at long distances to quark-gluon degrees of freedom at short scales. Ratios of separated response functions in ${\pi }^{-}$ and ${\pi }^{+}$ electroproduction are particularly informative. The ratio for transverse photons may allow this transition to be more easily observed, while the ratio for longitudinal photons provides a crucial verification of the assumed pole dominance, needed for reliable extraction of the pion form factor from electroproduction data. Method: Data were acquired with 2.6-5.2 GeV electron beams and the HMS+SOS spectrometers in Jefferson Lab Hall C, at central $Q^2$ values of 0.6, 1.0, 1.6 GeV${}^2$ at W=1.95 GeV, and $Q^2$=2.45 GeV${}^2$ at W=2.22 GeV. There was significant coverage in $\varphi$ and $ϵ$, which allowed separation of ${\sigma }_{L,T,LT,TT}$. Results: ${\sigma }_L$ shows a clear signature of the pion pole, with a sharp rise at small -t. In contrast, ${\sigma }_T$ is much flatter versus t. The longitudinal/transverse ratios evolve with $Q^2$ and t, and at the highest $Q^2$=2.45 GeV${}^2$ show a slight enhancement for ${\pi }^{-}$ production compared to ${\pi }^{+}$. The ${\pi }^{-}/{\pi }^{+}$ ratio for transverse photons exhibits only a small $Q^2$-dependence, following a nearly universal curve with t, with a steep transition to a value of about 0.25, consistent with s-channel quark knockout. The ${\sigma }_{TT}/{\sigma }_T$ ratio also drops rapidly with $Q^2$, qualitatively consistent with s-channel helicity conservation. The ${\pi }^{-}/{\pi }^{+}$ ratio for longitudinal photons indicates a small isoscalar contamination at W=1.95 GeV, consistent with what was observed in our earlier determination of the pion form factor at these kinematics.

   nucl-exPRC(2015)·3 citations
2. 02*

   MesonNet 2014 International Workshop. Mini-proceedings

   P. Adlarson🇸🇪 · M. Bashkanov🇩🇪 · J. Bijnens🇸🇪 · L. Caldeira Balkeståhl🇸🇪 · B. Cao🇸🇪 · G. Colangelo🇨🇭 · F. Curciarello🇮🇹 · V. De Leo🇮🇹 · K. Demmich🇩🇪 · G. Eichmann🇩🇪 · S. Eidelman🇷🇺 · S. Fang🇨🇳 and 34 other authors

   The MesonNet International Workshop was held in the Laboratori Nazionali di Frascati from September the 29th to October the 1st, 2014, being the concluding meeting of the MesonNet research network within EU HadronPhysics3 project. MesonNet is a research network focused on light meson physics gathering experimentalist and theoreticians from Europe and abroad. An overview of the research projects related to the scope of the network is presented in these mini-proceedings.

   nucl-exhep-exhep-phnucl-th15 citations
3. 03*

   Kinetic freeze out from an anisotropic fluid in high-energy heavy-ion collisions: particle spectra, Hanbury Brown-Twiss radii, and anisotropic flow

   Nicolas Borghini🇩🇪 · Steffen Feld🇩🇪 · Christian Lang🇩🇪

   Dissipative relativistic fluid-dynamical descriptions of the extended fireball formed in high-energy heavy-ion collisions are quite successful, yet require a prescription for converting the fluid into particles. We present arguments in favour of using a locally anisotropic momentum distribution for the particles emitted from the fluid, so as to smooth out discontinuities introduced by the usual conversion prescriptions. Building on this ansatz, we investigate the effect of the asymmetry on several observables of heavy ion physics.

   ↳ nucl-thhep-phnucl-exEPJC(2015)·2 citations
4. 04*

   Charge Symmetry Breaking in Electromagnetic Nucleon Form Factors in Elastic Parity-Violating Electron-Nucleus Scattering

   Gerald A. Miller🇺🇸

   The effects of charge symmetry breaking in nucleon electromagnetic form factors on parity- violating elastic electron-12C scattering is studied, and found to be much smaller than other known effects. The analysis of a planned experiment is discussed.

   ↳ nucl-thhep-phnucl-exPRC(2015)·2 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.