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Comments to the calculation of transverse beam spin asymmetry for electron proton elastic scattering
Kuraev, E. A.;Tomasi-Gustafsson, E.;Bakmaev, S.;Bystritskiy, Yu. M.;Bytev, V. V.
High Energy Physics - Phenomenology , 2007,
Abstract: The transverse beam spin induced asymmetry is calculated for the scattering of transversally polarized electrons on a proton target within a realistic model. Such asymmetry is due to the interference between the Born amplitude and the imaginary part of two photon exchange amplitude. In particular, the contribution of non-excited hadron state (elastic) to the two photon amplitude is calculated. The elastic contribution requires infrared divergences regularization and can be expressed in terms of numerical integrals of the target form factor. The inelastic channel corresponding to the one pion hadronic state contribution is enhanced by squared logarithmic terms. We show that the ratio of elastic over inelastic channel is of the order of 0.3 and cannot be ignored. Enhancement effects due to the decreasing of form factors bring the transverse beam asymmetry to values as large as $10^{-4}$ for particular kinematical conditions.
Transverse Beam Spin Asymmetries at Backward Angles in Elastic Electron-Proton and Quasi-elastic Electron-Deuteron Scattering  [PDF]
The G0 Collaboration,D. Androi?,D. S. Armstrong,J. Arvieux,S. L. Bailey,D. H. Beck,E. J. Beise,J. Benesch,F. Benmokhtar,L. Bimbot,J. Birchall,P. Bosted,H. Breuer,C. L. Capuano,Y. -C. Chao,A. Coppens,C. A. Davis,C. Ellis,G. Flores,G. Franklin,C. Furget,D. Gaskell,M. T. W. Gericke,J. Grames,G. Guillard,J. Hansknecht,T. Horn,M. K. Jones,P. M. King,W. Korsch,S. Kox,L. Lee,J. Liu,A. Lung,J. Mammei,J. W. Martin,R. D. McKeown,A. Micherdzinska,M. Mihovilovic,H. Mkrtchyan,M. Muether,S. A. Page,V. Papavassiliou,S. F. Pate,10 S. K. Phillips,P. Pillot,M. L. Pitt,M. Poelker,B. Quinn,W. D. Ramsay,J. -S. Real,J. Roche,P. Roos,J. Schaub,T. Seva,N. Simicevic,G. R. Smith,D. T. Spayde,M. Stutzman,R. Suleiman,V. Tadevosyan,W. T. H. van Oers,M. Versteegen,E. Voutier,W. Vulcan,S. P. Wells,S. E. Williamson,S. A. Wood,B. Pasquini,M. Vanderhaeghen
Physics , 2011, DOI: 10.1103/PhysRevLett.107.022501
Abstract: We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely polarized electrons from the proton, and performed the first measurement in quasi-elastic scattering on the deuteron, at backward angles (lab scattering angle of 108 degrees) for Q2 = 0.22 GeV^2/c^2 and 0.63 GeV^2/c^2 at beam energies of 362 MeV and 687 MeV, respectively. The asymmetry arises due to the imaginary part of the interference of the two-photon exchange amplitude with that of single photon exchange. Results for the proton are consistent with a model calculation which includes inelastic intermediate hadronic (piN) states. An estimate of the beam-normal single-spin asymmetry for the scattering from the neutron is made using a quasi-static deuterium approximation, and is also in agreement with theory.
Azimuthal Asymmetry and Transverse Momentum in Deep Inelastic Muon Scattering  [PDF]
Mark D. Baker for the Fermilab E665 Collaboration
Physics , 2013,
Abstract: The azimuthal asymmetry and the transverse momentum of forward produced charged hadrons in deep inelastic muon scattering have been studied as a function of the event kinematics and of the hadron variables. Primordial $k_T$ of the struck parton and O($\alpha_s$) corrections to the cross-section are expected to contribute to the transverse momentum and the azimuthal asymmetry of hadrons. The data show some unexpected dependences not present in a Monte Carlo simulation which includes the theoretical parton-level azimuthal asymmetry.
Single transverse-spin asymmetry for $D$-meson production in semi-inclusive deep inelastic scattering  [PDF]
Zhong-Bo Kang,Jian-Wei Qiu
Physics , 2008, DOI: 10.1103/PhysRevD.78.034005
Abstract: We study the single-transverse spin asymmetry for open charm production in the semi-inclusive lepton-hadron deep inelastic scattering. We calculate the asymmetry in terms of the QCD collinear factorization approach for $D$ mesons at high enough $P_{h\perp}$, and find that the asymmetry is proportional to the twist-three tri-gluon correlation function in the proton. With a simple model for the tri-gluon correlation function, we estimate the asymmetry for both COMPASS and eRHIC kinematics, and discuss the possibilities of extracting the tri-gluon correlation function in these experiments.
Transverse momentum-weighted Sivers asymmetry in semi-inclusive deep inelastic scattering at next-to-leading order  [PDF]
Zhong-Bo Kang,Ivan Vitev,Hongxi Xing
Physics , 2012, DOI: 10.1103/PhysRevD.87.034024
Abstract: We study the next-to-leading order perturbative QCD corrections to the transverse momentum-weighted Sivers asymmetry in semi-inclusive hadron production in lepton-proton deep inelastic scattering. The corresponding differential cross section is evaluated as a convolution of a twist-three quark-gluon correlation function, often referred to as Qiu-Sterman function, the usual unpolarized fragmentation function, and a hard coefficient function. By studying the collinear divergence structure, we identify the evolution kernel for the Qiu-Sterman function. The hard coefficient function, which is finite and free of any divergence, is evaluated at one-loop order.
New Measurements of the Transverse Beam Asymmetry for Elastic Electron Scattering from Selected Nuclei  [PDF]
The HAPPEX,PREX Collaborations,:,S. Abrahamyan,A. Acha,A. Afanasev,Z. Ahmed,H. Albataineh,K. Aniol,D. S. Armstrong,W. Armstrong,J. Arrington,T. Averett,B. Babineau,S. L. Bailey,J. Barber,A. Barbieri,A. Beck,V. Bellini,R. Beminiwattha,H. Benaoum,J. Benesch,F. Benmokhtar,P. Bertin,T. Bielarski,W. Boeglin,P. Bosted,F. Butaru,E. Burtin,J. Cahoon,A. Camsonne,M. Canan,P. Carter,C. C. Chang,G. D. Cates,Y. C. Chao,C. Chen,J. P. Chen,Seonho Choi,E. Chudakov,E. Cisbani,B. Craver,F. Cusanno,M. M. Dalton,R. De Leo,K. de Jager,W. Deconinck,P. Decowski,D. Deepa,X. Deng,A. Deur,D. Dutta,A. Etile,C. Ferdi,R. J. Feuerbach,J. M. Finn,D. Flay,G. B. Franklin,M. Friend,S. Frullani,E. Fuchey,S. A. Fuchs,K. Fuoti,F. Garibaldi,E. Gasser,R. Gilman,A. Giusa,A. Glamazdin,L. E. Glesener,J. Gomez,M. Gorchtein,J. Grames,K. Grimm,C. Gu,O. Hansen,J. Hansknecht,O. Hen,D. W. Higinbotham,R. S. Holmes,T. Holmstrom,C. J. Horowitz,J. Hoskins,J. Huang,T. B. Humensky,C. E. Hyde,H. Ibrahim,F. Itard,C. M. Jen,E. Jensen,X. Jiang,G. Jin,S. Johnston,J. Katich,L. J. Kaufman,A. Kelleher,K. Kliakhandler,P. M. King,A. Kolarkar,S. Kowalski,E. Kuchina,K. S. Kumar,L. Lagamba,D. Lambert,P. LaViolette,J. Leacock,J. Leckey IV,J. H. Lee,J. J. LeRose,D. Lhuillier,R. Lindgren,N. Liyanage,N. Lubinsky,J. Mammei,F. Mammoliti,D. J. Margaziotis,P. Markowitz,M. Mazouz,K. McCormick,A. McCreary,D. McNulty,D. G. Meekins,L. Mercado,Z. E. Meziani,R. W. Michaels,M. Mihovilovic,B. Moffit,P. Monaghan,N. Muangma,C. Munoz-Camacho,S. Nanda
Physics , 2012, DOI: 10.1103/PhysRevLett.109.192501
Abstract: We have measured the beam-normal single-spin asymmetry $A_n$ in the elastic scattering of 1-3 GeV transversely polarized electrons from $^1$H and for the first time from $^4$He, $^{12}$C, and $^{208}$Pb. For $^1$H, $^4$He and $^{12}$C, the measurements are in agreement with calculations that relate $A_n$ to the imaginary part of the two-photon exchange amplitude including inelastic intermediate states. Surprisingly, the $^{208}$Pb result is significantly smaller than the corresponding prediction using the same formalism. These results suggest that a systematic set of new $A_n$ measurements might emerge as a new and sensitive probe of the structure of heavy nuclei.
Large Logarithms in the Beam Normal Spin Asymmetry of Elastic Electron--Proton Scattering  [PDF]
Andrei Afanasev,N. P. Merenkov
Physics , 2004, DOI: 10.1103/PhysRevD.70.073002
Abstract: We study a parity-conserving single-spin beam asymmetry of elastic electron-proton scattering induced by an absorptive part of the two-photon exchange amplitude. It is demonstrated that excitation of inelastic hadronic intermediate states by the consecutive exchange of two photons leads to logarithmic and double-logarithmic enhancement due to contributions of hard collinear quasi-real photons. The asymmetry at small electron scattering angles is expressed in terms of the total photoproduction cross section on the proton, and is predicted to reach the magnitude of 20-30 parts per million. At these conditions and fixed 4-momentum transfers, the asymmetry is rising logarithmically with increasing electron beam energy, following the high-energy diffractive behavior of total photoproduction cross section on the proton.
Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering
G0 Collaboration;Armstrong, D. S.
High Energy Physics - Phenomenology , 2007, DOI: 10.1103/PhysRevLett.99.092301
Abstract: We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely-polarized 3 GeV electrons from unpolarized protons at Q^2 = 0.15, 0.25 (GeV/c)^2. The results are inconsistent with calculations solely using the elastic nucleon intermediate state, and generally agree with calculations with significant inelastic hadronic intermediate state contributions. A_n provides a direct probe of the imaginary component of the 2-gamma exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments.
Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering  [PDF]
G0 Collaboration,D. S. Armstrong
Physics , 2007, DOI: 10.1103/PhysRevLett.99.092301
Abstract: We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely-polarized 3 GeV electrons from unpolarized protons at Q^2 = 0.15, 0.25 (GeV/c)^2. The results are inconsistent with calculations solely using the elastic nucleon intermediate state, and generally agree with calculations with significant inelastic hadronic intermediate state contributions. A_n provides a direct probe of the imaginary component of the 2-gamma exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments.
QED correction to asymmetry for polarized ep-scattering from the method of the electron structure functions  [PDF]
A. V. Afanasev,I. Akushevich,N. P. Merenkov
Physics , 2001, DOI: 10.1134/1.1705692
Abstract: The electron structure function method is applied to calculate model-independent radiative corrections to an asymmetry of electron-proton scattering. The representations for both spin-independent and spin-dependent parts of the cross-section are derived. Master formulae take into account the leading corrections in all orders and the main contribution of the second order next-to-leading ones and have accuracy at the level of one per mille. Numerical calculations illustrate our analytical results for both elastic and deep inelastic events.
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