Ovisnost nuklearne prozirnosti o Q2 za nekoherentnu elektrotvorbu ρ0

Measurements of exclusive incoherent electroproduction of ρ0 (770) meson from 2H, 12C, and 63Cu targets up to Q2 = 4 GeV2 are proposed using the CLAS detector at Jefferson Lab. The objective of these measurements is to determine the Q2 dependence of the nuclear transparency ratio for the two nuclear targets: 12C and 63Cu at fixed coherence length of quark-antiquark fluctuations of the virtual photon. A sizeable rise of the nuclear transparency is predicted and can be measured in this experiment. A relatively large increase of the nuclear transparency can be considered as a signature of the onset of color transparency.Predlažemo mjerenja ekskluzivne elektrotvorbe ρ0 (770) mezona u metama 2H, 12C i 63Cu, za Q2 = 4 GeV2 , pomoću detektora CLAS u Jeffersonovom Labu. Cilj mjerenja je određivanje nuklearne prozirnosti u ovisnosti o Q2 za dvije nuklearne mete, 12C i 63Cu, pri određenoj koherentnoj duljini fluktuacija kvark-antikvark virtualnog fotona. Predviđa se znatno povećanje nuklearne prozirnosti koje se može mjeriti u predloženom eksperimentu. Znatan porast nuklearne prozirnosti bi se smatrao znakom za pojavu prozirnosti boje

Ovisnost nuklearne prozirnosti o Q2 za nekoherentnu elektrotvorbu ρ0

Measurements of exclusive incoherent electroproduction of ρ0 (770) meson from 2H, 12C, and 63Cu targets up to Q2 = 4 GeV2 are proposed using the CLAS detector at Jefferson Lab. The objective of these measurements is to determine the Q2 dependence of the nuclear transparency ratio for the two nuclear targets: 12C and 63Cu at fixed coherence length of quark-antiquark fluctuations of the virtual photon. A sizeable rise of the nuclear transparency is predicted and can be measured in this experiment. A relatively large increase of the nuclear transparency can be considered as a signature of the onset of color transparency.Predlažemo mjerenja ekskluzivne elektrotvorbe ρ0 (770) mezona u metama 2H, 12C i 63Cu, za Q2 = 4 GeV2 , pomoću detektora CLAS u Jeffersonovom Labu. Cilj mjerenja je određivanje nuklearne prozirnosti u ovisnosti o Q2 za dvije nuklearne mete, 12C i 63Cu, pri određenoj koherentnoj duljini fluktuacija kvark-antikvark virtualnog fotona. Predviđa se znatno povećanje nuklearne prozirnosti koje se može mjeriti u predloženom eksperimentu. Znatan porast nuklearne prozirnosti bi se smatrao znakom za pojavu prozirnosti boje

First measurement of the helicity asymmetry E in eta photoproduction on the proton

Results are presented for the first measurement of the double-polarization helicity asymmetry E for the eta photoproduction reaction gamma p - \u3e eta p. Data were obtained using the FROzen Spin Target (FROST) with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of center-of-mass energy W from threshold to 2.15 GeV and a large range in center-of-mass polar angle. As an initial application of these data, the results have been incorporated into the Julich-Bonn model to examine the case for the existence of a narrow N* resonance between 1.66 and 1.70 GeV. The addition of these data to the world database results in marked changes in the predictions for the Eobservable from that model. Further comparison with several theoretical approaches indicates these data will significantly enhance our understanding of nucleon resonances. (C) 2016 Published by Elsevier B.V

First measurement of the polarization observable E in the (p)over-right-arrow((gamma)over-right-arrow, pi(+))n reaction up to 2.25 GeV

First results from the longitudinally polarized frozen-spin target (FROST) program are reported. The double-polarization observable E, for the reaction (p) over right arrow((gamma) over right arrow, pi( + ))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, Jfilich-Bonn, and SAID groups. (C) 2015 The Authors. Published by Elsevier B.V

Exclusive pi(0) electroproduction at W \u3e 2 GeV with CLAS

Exclusive neutral-pion electroproduction (ep -\u3e e\u27p\u27pi(0)) was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections d(4)sigma/dtdQ(2)dx(B)d phi(pi) and structure functions sigma(T) + sigma(L), sigma(TT), and sigma(LT) as functions of t were obtained over a wide range of Q(2) and x(B). The data are compared with Regge and handbag theoretical calculations. Analyses in both frameworks find that a large dominance of transverse processes is necessary to explain the experimental results. For the Regge analysis it is found that the inclusion of vector meson rescattering processes is necessary to bring the magnitude of the calculated and measured structure functions into rough agreement. In the handbag framework, there are two independent calculations, both of which appear to roughly explain the magnitude of the structure functions in terms of transversity generalized parton distributions

Transverse polarization of Sigma(+)(1189) in photoproduction on a hydrogen target in CLAS

Experimental results on the Sigma(+)(1189) hyperon transverse polarization in photoproduction on a hydrogen target using the CLAS detector at Jefferson Laboratory are presented. The Sigma(+)(1189) was reconstructed in the exclusive reaction gamma + p -\u3e K-s(0) + Sigma(+)(1189) via the Sigma(+) -\u3e p pi(0) decay mode. The K-s(0) was reconstructed in the invariant mass of two oppositely charged pions with the pi(0) identified in the missing mass of the detected p pi(+)pi(-) final state. Experimental data were collected in the photon energy range E-gamma = 1.0-3.5 GeV (root s range 1.66-2.73 GeV). We observe a large negative polarization of up to 95%. As the mechanism of transverse polarization of hyperons produced in unpolarized photoproduction experiments is still not well understood, these results will help to distinguish between different theoretical models on hyperon production and provide valuable information for the searches of missing baryon resonances

Time Dependent Hadronization via HERMES and EMC Data Consistency

Using QCD-inspired time dependent cross sections for pre-hadrons we provide a combined analysis of available experimental data on hadron attenuation in DIS off nuclei as measured by HERMES with 12 and 27 GeV and by EMC with 100 and 280 GeV lepton beam energies. We extract the complete four-dimensional evolution of the pre-hadrons using the JETSET-part of PYTHIA. We find a remarkable sensitivity of nuclear attenuation data to the details of the time-evolution of cross sections. Only cross sections evolving linearly in time describe the available data in a wide kinematical regime. Predictions for experimental conditions at JLAB (5 and 12 GeV beam energies) are included.Comment: version as publishe

Evidence for the onset of color transparency in rho(0) electroproduction off nuclei

We have measured the nuclear transparency of the incoherent diffractive A(e,e\u27 rho(0)) process in C-12 and Fe-56 targets relative to H-2 using a 5 GeV electron beam. The nuclear transparency, the ratio of the produced rho(0,)s on a nucleus relative to deuterium, which is sensitive to rho A interaction, was studied as function of the coherence length (l(c)), a lifetime of the hadronic fluctuation of the virtual photon, and the four-momentum transfer squared (Q(2)). While the transparency for both C-12 and Fe-56 showed no lc dependence, a significant Q(2) dependence was measured, which is consistent with calculations that included the color transparency effects. (C) 2012 Elsevier B.V. All rights reserved