Thu·Sep 8, 2011Thursday·September 8, 2011

1. 01*

   Nucleon Resonance Electrocouplings from the CLAS Data on Exclusive Meson Electroproduction off Protons

   Victor I. Mokeev🇺🇸 · Inna G. Aznauryan🇦🇲 · Volker D. Burkert🇺🇸

   ${\gamma }_{v}N{N}^{\ast }$ transition helicity amplitudes (electrocouplings) of several prominent excited proton states are determined for the first time in independent analyses of ${\pi }^{+}n$, ${\pi }^{0}p$, and ${\pi }^{+}{\pi }^{-}p$ electroproduction off protons. Analysis of ${\pi }^{+}{\pi }^{-}p$ electroproduction has extended considerably information on electrocouplings of high lying N* states, which decay preferentially to the $N\pi \pi$ final states.

   nucl-exhep-exhep-ph5 citations
2. 02*

   Reexamination of phenomenological two-photon exchange corrections to the proton form factors and e+-p scattering

   I. A. Qattan🇦🇪 · A. Alsaad🇯🇴 · J. Arrington🇺🇸

   We extract the two-photon exchange (TPE) contributions to electron--proton elastic scattering using two parametrizations and compare the results to different phenomenological extractions and direct calculations of the TPE effects. We find that many of the extractions give similar results, and highlight the common assumptions and the impact of not including such assumptions. We provide a simple parametrization of the TPE contribution to the unpolarized cross section, along with an estimate of the fit uncertainties and the uncertainties associated with the assumptions made in the extraction. We look at the contributions as extracted from various e--p elastic scattering observables, and make predictions for ratio $R^{e^{+}{e}^{-}}$ of positron-proton to electron-proton elastic scattering cross sections.

   nucl-exnucl-thPRC(2011)·49 citations
3. 03*

   Gluon saturation effects on the color singlet J/Psi production in high energy dA and AA collisions

   F. Dominguez🇺🇸 · D.E. Kharzeev🇺🇸 · E.M. Levin🇮🇱 · A.H. Mueller🇺🇸 · K. Tuchin🇺🇸

   We derive the formulae for the cross section of J/Psi production in high energy pA and AA collisions taking into account the gluon saturation/color glass condensate effects. We then perform the numerical calculations of the corresponding nuclear modification factors and find a good agreement between our calculations and the experimental data on J/Psi production in dA collisions. We also observe that cold nuclear modification effects alone cannot describe the data on J/Psi production in AA collisions. Additional final state suppression (at RHIC) and enhancement (at LHC) mechanisms are required to explain the experimental observations.

   ↳ hep-phnucl-exnucl-thPLB(2012)·32 citations
4. 04*

   Anomalous dipion invariant mass distribution of the ${\rm Y}(4S)$ decays into ${\rm Y}(1S){\pi }^{+}{\pi }^{-}$ and ${\rm Y}(2S){\pi }^{+}{\pi }^{-}$

   Dian-Yong Chen🇨🇳 · Xiang Liu🇨🇳 · Xue-Qian Li🇨🇳

   To solve the discrepancy between the experimental data on the partial widths and lineshapes of the dipion emission of ${\rm Y}(4S)$ and the theoretical predictions, we suggest that there is an additional contribution which was not taken into account in previous calculations. Noticing that the mass of ${\rm Y}(4S)$ is above the production threshold of $B\bar{B}$, the contribution of the sequential process ${\rm Y}(4S)\to B\bar{B}\to {\rm Y}(nS)+S\to {\rm Y}(nS)+{\pi }^{+}{\pi }^{-}$ ($n=1,2$) may be sizable, and its interference with that from the direct production would be important. The goal of this work is to investigate if a sum of the two contributions with a relative phase indeed reproduces the data. Our numerical results on the partial widths and the lineshapes $d\Gamma ({\rm Y}(4S)\to {\rm Y}(2S,1S){\pi }^{+}{\pi }^{-})/d(m_{{\pi }^{+}{\pi }^{-}})$ are satisfactorily consistent with the measurements, thus the role of this mechanism is confirmed. Moreover, with the parameters obtained by fitting the data of the Belle and Babar collaborations, we predict the distributions $d\Gamma ({\rm Y}(4S)\to {\rm Y}(2S,1S){\pi }^{+}{\pi }^{-})/d\cos \theta$ which have not been measured yet.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2011)·19 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.