http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Evidence for the onset of color transparency in ρ<sup>0</sup> electroproduction off nuclei
CLAS Collaboration,El Fassi, L.,Zana, L.,Hafidi, K.,Holtrop, M.,Mustapha, B.,Brooks, W.K.,Hakobyan, H.,Zheng, X.,Adhikari, K.P.,Adikaram, D.,Aghasyan, M.,Amaryan, M.J.,Anghinolfi, M.,Arrington, J.,Ava North-Holland Pub. Co 2012 Physics letters: B Vol.712 No.4
We have measured the nuclear transparency of the incoherent diffractive A(e,e<SUP>'</SUP>ρ<SUP>0</SUP>) process in <SUP>12</SUP>C and <SUP>56</SUP>Fe targets relative to <SUP>2</SUP>H using a 5 GeV electron beam. The nuclear transparency, the ratio of the produced ρ<SUP>0</SUP>@?s on a nucleus relative to deuterium, which is sensitive to ρA interaction, was studied as function of the coherence length (l<SUB>c</SUB>), a lifetime of the hadronic fluctuation of the virtual photon, and the four-momentum transfer squared (Q<SUP>2</SUP>). While the transparency for both <SUP>12</SUP>C and <SUP>56</SUP>Fe showed no l<SUB>c</SUB> dependence, a significant Q<SUP>2</SUP> dependence was measured, which is consistent with calculations that included the color transparency effects.
Near-threshold photoproduction of φ mesons from deuterium
CLAS Collaboration,Qian, X.,Chen, W.,Gao, H.,Hicks, K.,Kramer, K.,Laget, J.M.,Mibe, T.,Qiang, Y.,Stepanyan, S.,Tedeschi, D.J.,Xu, W.,Adhikari, K.P.,Amaryan, M.,Anghinolfi, M.,Ball, J.,Battaglieri, M. North-Holland Pub. Co 2011 Physics letters: B Vol.696 No.4
We report the first, kinematically-complete measurement of the differential cross section of φ-meson photoproduction from deuterium near the production threshold for a proton using the CLAS detector and a tagged-photon beam in Hall B at Jefferson Lab. The measurement was carried out by a triple coincidence detection of a proton, K<SUP>+</SUP> and K<SUP>-</SUP> near the theoretical production threshold of 1.57 GeV. The extracted differential cross sections dσdt for the initial photon energy range of 1.65-1.75 GeV are consistent with predictions based on a quasifree mechanism. Our finding is different from recent LEPS results on φ-meson photoproduction from deuterium in a similar incident photon energy range, but in a different momentum transfer region.
CLAS Collaboration,Pereira, S.A.,Mirazita, M.,Rossi, P.,De Sanctis, E.,Niculescu, G.,Niculescu, I.,Stepanyan, S.,Adhikari, K.P.,Aghasyan, M.,Anghinolfi, M.,Baghdasaryan, H.,Ball, J.,Battaglieri, M.,Be North-Holland Pub. Co 2010 Physics letters: B Vol.688 No.4
<P>Differential cross sections of the reaction gamma d -> K+Sigma(-)(p) have been measured with the CLAS detector at Jefferson Lab using incident photons with energies between 1.1 and 3.6 GeV. This is the first complete set of strangeness photoproduction data on the neutron covering a broad angular range. At energies close to threshold and up to E-gamma similar to 1.8 GeV. the shape of the angular distribution is suggestive of the presence of s-channel production mechanisms. For E-gamma > 1.8 GeV, a clear forward peak appears and becomes more prominent as the photon energy increases, suggesting contributions from t-channel production mechanisms. These data can be used to constrain future analysis of this reaction. (c) 2010 Elsevier B.V. All rights reserved.</P>
Dey, B.,Collaboration, CLAS THE AMERICAN PHYSICAL SOCIETY 2014 PHYSICAL REVIEW C - Vol.89 No.5
High-statistics measurements of differential cross sections and spin density matrix elements for the reaction gamma p -> phi p have been made using the CLAS detector at Jefferson Lab. We cover center-of-mass energies (v s) from 1.97 to 2.84 GeV, with an extensive coverage in the phi production angle. The high statistics of the data sample made it necessary to carefully account for the interplay between the f natural lineshape and effects of the detector resolution, that are found to be comparable in magnitude. We study both the charged-(phi -> K+ K-) and neutral( phi ->(KsKL0)-K-0) K (K) over bar decay modes of the phi Further, for the charged mode, we differentiate between the cases where the final K-track is directly detected or its momentum reconstructed as the total missing momentum in the event. The two charged-mode topologies and the neutral-mode have different resolutions and are calibrated against each other. Extensive usage is made of kinematic fitting to improve the reconstructed f mass resolution. Our final results are reported in 10- and mostly 30-MeV-wide root s bins for the charged-and the neutral-modes, respectively. Possible effects from K+Lambda* channels with pK (K) over bar final states are discussed. These present results constitute the most precise and extensive phi photoproduction measurements to date and in conjunction with the omega photoproduction results recently published by CLAS, will greatly improve our understanding of low energy vector meson photoproduction.
North-Holland Pub. Co 2015 Physics letters: B Vol.750 No.-
First results from the longitudinally polarized frozen-spin target (FROST) program are reported. The double-polarization observable E, for the reaction γ→p→→π<SUP>+</SUP>n, has been measured using a circularly polarized tagged-photon beam, with energies from 0.35 to 2.37 GeV. The final-state pions were detected with the CEBAF Large Acceptance Spectrometer in Hall B at the Thomas Jefferson National Accelerator Facility. These polarization data agree fairly well with previous partial-wave analyses at low photon energies. Over much of the covered energy range, however, significant deviations are observed, particularly in the high-energy region where high-L multipoles contribute. The data have been included in new multipole analyses resulting in updated nucleon resonance parameters. We report updated fits from the Bonn-Gatchina, Julich-Bonn, and SAID groups.