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Bosted, P. E.,Amaryan, M. J.,Anefalos Pereira, S.,Avakian, H.,Badui, R. A.,Ball, J.,Baltzell, N. A.,Battaglieri, M.,Batourine, V.,Bedlinskiy, I.,Biselli, A. S.,Briscoe, W. J.,Bü,ltmann, S.,Burkert American Physical Society 2017 Physical Review C Vol.95 No.3
<P>Beam-target double-spin asymmetries and target single-spin asymmetries were measured for the exclusive pi(+) electroproduction reaction. gamma(*) p -> n pi(+). The results were obtained from scattering of 6-GeV longitudinally polarized electrons off longitudinally polarized protons using the CEBAF Large Acceptance Spectrometer at Jefferson Laboratory. The kinematic range covered is 1.1 < W < 3 GeV and 1 < Q(2) < 6 GeV2. Results were obtained for about 6000 bins in W, Q(2), cos(theta(*)), and phi(*). Except at forward angles, very large target-spin asymmetries are observed over the entire W region. Reasonable agreement is found with phenomenological fits to previous data for W < 1.6 GeV, but very large differences are seen at higher values of W. A generalized parton distributions (GPD)-based model is in poor agreement with the data. When combined with cross-sectional measurements, the present results provide powerful constraints on nucleon resonance amplitudes at moderate and large values of Q(2), for resonances with masses as high as 2.4 GeV.</P>
Beam-target double-spin asymmetry in quasielastic electron scattering off the deuteron with CLAS
Mayer, M.,Kuhn, S. E.,Adhikari, K. P.,Akbar, Z.,Anefalos Pereira, S.,Asryan, G.,Avakian, H.,Badui, R. A.,Ball, J.,Baltzell, N. A.,Battaglieri, M.,Bedlinskiy, I.,Biselli, A. S.,Boiarinov, S.,Bosted, P. American Physical Society 2017 Physical Review C Vol.95 No.2
<P>Conclusions: Final-state interactions seem to play a lesser role for polarization observables in deuteron two-body electrodisintegration than for absolute cross sections. Our data, while limited in statistical power, indicate that PWIA models work reasonably well to understand the asymmetries at lower missing momenta. In turn, this information can be used to extract the product of beam and target polarization (PbPt) from quasielastic electron-deuteron scattering, which is useful for measurements of spin observables in electron-neutron inelastic scattering. However, at the highest missing (neutron) momenta, FSI effects become important and must be accounted for.</P>
Photoproduction of the<sub>f1</sub>(1285)meson
Dickson, R.,Schumacher, R. A.,Adhikari, K. P.,Akbar, Z.,Amaryan, M. J.,Anefalos Pereira, S.,Badui, R. A.,Ball, J.,Battaglieri, M.,Batourine, V.,Bedlinskiy, I.,Biselli, A.,Boiarinov, S.,Briscoe, W. J. American Physical Society 2016 Physical Review C Vol.93 No.6
<P>The f(1)(1285) meson withmass 1281.0 +/- 0.8MeV/c(2) and width 18.4 +/- 1.4MeV (full width at half maximum) was measured for the first time in photoproduction from a proton target using CLAS at Jefferson Lab. Differential cross sections were obtained via the eta pi(+)pi(-), K+(K) over bar (0) pi(-), and (K-K0)pi(+) decay channels from threshold up to a center-of-mass energy of 2.8 GeV. The mass, width, and an amplitude analysis of the eta pi(+)pi(-) final-state Dalitz distribution are consistent with the axial-vector J(P) = 1(+) f(1)(1285) identity, rather than the pseudoscalar 0(-) eta(1295). The production mechanism is more consistent with s-channel decay of a high-mass N* state and not with t-channel meson exchange. Decays to eta pi pi go dominantly via the intermediate a(0)(+/-) (980)pi(-/+) states, with the branching ratio Gamma [a(0)pi (no (K) over barK)]/Gamma[eta pi pi (all)] = 0.74 +/- 0.09. The branching ratios Gamma (K (K) over bar pi)/Gamma(eta pi pi) = 0.216 +/- 0.033 and Gamma (gamma rho(0))/Gamma(eta pi pi) = 0.047 +/- 0.018 were also obtained. The first is in agreement with previous data for the f(1)(1285), while the latter is lower than the world average.</P>
Kim, A.,Avakian, H.,Burkert, V.,Joo, K.,Kim, W.,Adhikari, K.P.,Akbar, Z.,Anefalos Pereira, S.,Badui, R.A.,Battaglieri, M.,Batourine, V.,Bedlinskiy, I.,Biselli, A.S.,Boiarinov, S.,Bosted, P.,Briscoe, W North-Holland Pub. Co 2017 Physics letters. Section B Vol.768 No.-
<P><B>Abstract</B></P> <P>The target and double spin asymmetries of the exclusive pseudoscalar channel e → p → → e p <SUP> π 0 </SUP> were measured for the first time in the deep-inelastic regime using a longitudinally polarized 5.9 GeV electron beam and a longitudinally polarized proton target at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS). The data were collected over a large kinematic phase space and divided into 110 four-dimensional bins of <SUP> Q 2 </SUP> , <SUB> x B </SUB> , −<I>t</I> and <I>ϕ</I>. Large values of asymmetry moments clearly indicate a substantial contribution to the polarized structure functions from transverse virtual photon amplitudes. The interpretation of experimental data in terms of generalized parton distributions (GPDs) provides the first insight on the chiral-odd GPDs <SUB> H ˜ T </SUB> and <SUB> E T </SUB> , and complement previous measurements of unpolarized structure functions sensitive to the GPDs <SUB> H T </SUB> and <SUB> E ¯ T </SUB> . These data provide a crucial input for parametrizations of essentially unknown chiral-odd GPDs and will strongly influence existing theoretical calculations based on the handbag formalism.</P>
Photoproduction ofΛand<sup>Σ0</sup>hyperons using linearly polarized photons
Paterson, C. A.,Ireland, D. G.,Livingston, K.,McKinnon, B.,Adhikari, K. P.,Adikaram, D.,Akbar, Z.,Amaryan, M.,Anefalos Pereira, S.,Badui, R. A.,Ball, J.,Baltzell, N. A.,Battaglieri, M.,Bedlinskiy, I. American Physical Society 2016 Physical review. C Vol.93 No.6
<P>Background: Measurements of polarization observables for the reactions (gamma) over right arrowp -> K+ Lambda and (gamma) over right arrowp -> K+ Sigma(0) have been performed. This is part of a program of measurements designed to study the spectrum of baryon resonances in particular, and nonperturbative QCD in general. Purpose: The accurate measurement of several polarization observables provides tight constraints for phenomenological fits, which allow the study of strangeness in nucleon and nuclear systems. Beam-recoil observables for the (gamma) over right arrowp -> K+ Sigma(0) reaction have not been reported before now. Method: Themeasurements were carried out using linearly polarized photon beams incident on a liquid hydrogen target, and the CLAS detector at the Thomas Jefferson National Accelerator Facility. The energy range of the results is 1.71 < W < 2.19 GeV, with an angular range -0.75 < cos theta(K)* < +0.85. Results: The observables extracted for both reactions are beam asymmetry Sigma, target asymmetry T, and the beam-recoil double polarization observables O-x and O-z. Conclusions: Comparison with theoretical fits indicates that, in the regions where no previous data existed, the new data contain significant new information, and strengthen the evidence for the set of resonances used in the latest Bonn-Gatchina fit.</P>