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Kozlov A, Sarty AJ, Aniol KA, Bartsch P, Baumann D, Bertozzi W, Bohinc K, Böhm R, Chen JP, Dale D, Dennis L, Derber S, Ding M, Distler MO, Dragovitsch P, Ewald I, Fissum KG, Friedrich J, Friedrich JM, Geiges R, Gilad S, Jennewein P, Kahrau M, Kohl M, Krygier KW, Liesenfeld A, Margaziotis DJ, Merkel H, Merle P, Müller U, Neuhausen R, Pospischil T, Potokar M, Riccardi G, Roché R, Rosner G, Rowntree D, Schmieden H, Sirca S, Templon JA, Thompson MN, Wagner A, Walcher T, Weis M, Zhao J, Zhou ZL, Golak J, Glöckle W, Witała H. Measurement of the exclusive 3He(e,e'p) reaction below the quasielastic peak. Phys Rev Lett 2004; 93:132301. [PMID: 15524710 DOI: 10.1103/physrevlett.93.132301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2002] [Revised: 12/16/2003] [Indexed: 05/24/2023]
Abstract
New, high-precision measurements of the 3He(e,e(')p) reaction using the A1 Collaboration spectrometers at the Mainz microtron MAMI are presented. These were performed in antiparallel kinematics at energy transfers below the quasielastic peak, and at a central momentum transfer of 685 MeV/c. Cross sections and distorted momentum distributions were extracted and compared to theoretical predictions and existing data. The longitudinal and transverse behavior of the cross section was also studied. Sizable differences in the cross-section behavior from theoretical predictions based on the plane wave impulse approximation were observed in both the two- and three-body breakup channels. Full Faddeev-type calculations account for some of the observed excess cross-section, but significant differences remain.
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Affiliation(s)
- A Kozlov
- Department of Physics, University of Regina, Regina, SK S4S0A2, Canada and School of Physics, The University of Melbourne, VIC 3010, Australia
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Bartsch P, Baumann D, Bermuth J, Böhm R, Bohinc K, Bosnar D, Ding M, Distler M, Drechsel D, Elsner D, Ewald I, Friedrich J, Friedrich JM, Grözinger S, Hedicke S, Jennewein P, Kahrau M, Kamalov SS, Klein F, Krygier KW, Liesenfeld A, Merkel H, Merle P, Müller U, Neuhausen R, Pospischil T, Potokar M, Rosner G, Schmieden H, Seimetz M, Süle A, Tiator L, Wagner A, Walcher T, Weis M. Measurement of the beam-helicity asymmetry in the p((-->)e,e'p)pi(0) reaction at the energy of the Delta(1232) resonance. Phys Rev Lett 2002; 88:142001. [PMID: 11955140 DOI: 10.1103/physrevlett.88.142001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2001] [Indexed: 05/23/2023]
Abstract
In a p((-->)e,e'p)pi(0) out-of-plane coincidence experiment at the three-spectrometer setup of the Mainz Microtron MAMI, the beam-helicity asymmetry has been precisely measured around the energy of the Delta(1232) resonance and Q(2) = 0.2(GeV/c)(2). The results are in disagreement with three up-to-date model calculations. This is interpreted as a lack of understanding of the nonresonant background, which in dynamical models is related to the pion cloud.
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Affiliation(s)
- P Bartsch
- Institut für Kernphysik, Universität Mainz, D-55099 Mainz, Germany
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Merkel H, Bartsch P, Baumann D, Bermuth J, Bernstein AM, Bohinc K, Böhm R, Clawiter N, Derber S, Ding M, Distler MO, Ewald I, Friedrich JM, Friedrich J, Jennewein P, Kahrau M, Kohl M, Krygier KW, Kuss M, Liesenfeld A, Merle P, Miskimen RA, Müller U, Neuhausen R, Pavan MM, Pospischil T, Potokar M, Rosner G, Schmieden H, Seimetz M, Sirca S, Wagner A, Walcher T, Weis M. Neutral pion threshold production at Q(2) = 0.05 GeV(2)/c(2) and chiral perturbation theory. Phys Rev Lett 2002; 88:012301. [PMID: 11800938 DOI: 10.1103/physrevlett.88.012301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2001] [Indexed: 05/23/2023]
Abstract
New data are presented on the p(e,e'p)pi(0) reaction at threshold at a four-momentum transfer of Q(2) = 0.05 GeV(2)/c(2). The data were taken with the three-spectrometer setup of the A1 Collaboration at the Mainz Microtron MAMI. The complete center of mass solid angle was covered up to a center of mass energy of 4 MeV above threshold. Combined with measurements at three different values of the virtual photon polarization epsilon, the structure functions sigma(T), sigma(L), sigma(TT), and sigma(TL) are determined. The results are compared with calculations in heavy baryon chiral perturbation theory and with a phenomenological model. The measured cross section is significantly smaller than both predictions.
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Affiliation(s)
- H Merkel
- Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany.
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Pospischil T, Bartsch P, Baumann D, Bermuth J, Böhm R, Bohinc K, Derber S, Ding M, Distler M, Drechsel D, Elsner D, Ewald I, Friedrich J, Friedrich JM, Geiges R, Hedicke S, Jennewein P, Kahrau M, Kamalov SS, Klein F, Krygier KW, Lac J, Liesenfeld A, McIntyre J, Merkel H, Merle P, Müller U, Neuhausen R, Potokar M, Ransome RD, Rohe D, Rosner G, Schmieden H, Seimetz M, Sirca S, Sick I, Süle A, Tiator L, Wagner A, Walcher T, Warren GA, Weis M. Measurement of the recoil polarization in the p(e-->, e'p-->)pi(0) reaction at the Delta(1232) resonance. Phys Rev Lett 2001; 86:2959-2962. [PMID: 11290082 DOI: 10.1103/physrevlett.86.2959] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2000] [Indexed: 05/23/2023]
Abstract
The recoil proton polarization has been measured in the p(e-->,e'p-->)pi(0) reaction in parallel kinematics around W = 1232 MeV, Q2 = 0.121 (GeV/c)2, and epsilon = 0.718 using the polarized cw electron beam of the Mainz Microtron. All three proton polarization components, Px/P(e) = (-11.4+/-1.3+/-1.4)%, P(y) = (-43.1+/-1.3+/-2.2)%, and P(z)/P(e) = (56.2+/-1.5+/-2.6)%, could be measured simultaneously. The Coulomb quadrupole to magnetic dipole ratio, CMR = (-6.4+/-0.7(stat)+/-0.8(syst))%, was determined from Px in the framework of the Mainz Unitary Isobar Model. The consistency among the reduced polarizations and the extraction of the ratio of longitudinal-to-transverse response is discussed.
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Affiliation(s)
- T Pospischil
- Institut für Kernphysik, Universität Mainz, Germany
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Roche J, Friedrich JM, Lhuillier D, Bartsch P, Baumann D, Berthot J, Bertin PY, Breton V, Boeglin WU, Bohm R, D'Hose N, Derber S, Degrande N, Ding M, Distler MO, Ducret JE, Ewald I, Fonvieille H, Friedrich J, Guichon PA, Holvoet H, Hyde-Wright CE, Jennewein P, Kahrau M, Kerhoas S, Krygier KW. First determination of generalized polarizabilities of the proton by a virtual compton scattering experiment. Phys Rev Lett 2000; 85:708-711. [PMID: 10991379 DOI: 10.1103/physrevlett.85.708] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2000] [Indexed: 05/23/2023]
Abstract
Absolute differential cross sections for the reaction ep-->epgamma have been measured at a four-momentum transfer with virtuality Q2 = 0.33 GeV2 and polarization epsilon = 0.62 in the range 33.6 to 111.5 MeV/c for the momentum of the outgoing photon in the photon-proton center of mass frame. The experiment has been performed with the high-resolution spectrometers at the Mainz Microtron MAMI. From the photon angular distributions, two structure functions which are a linear combination of the generalized polarizabilities have been determined for the first time.
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Affiliation(s)
- J Roche
- CEA Saclay, DSM/DAPNIA/SPhN, 91191 Gif-sur-Yvette Cedex, France
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Blomqvist KI, Boeglin WU, Böhm R, Distler M, Edelhoff R, Friedrich J, Geiges R, Kahrau M, Korn M, Kramer H, Krygier KW, Kunde V, Kuss M, Laget JM, Liesenfeld A, Merle K, Neuhausen R, Offermann EA, Pospischil T, Potokar M, Rangacharyulu C, Rokavec A, Richter A, Richter AW, Rosner G, Sauer P, Schardt S, Schrieder G, Suda T, Vodenik B, Wagner A, Walcher T, Wolf S. Forward-Angle 3He(e,e' pi +/-) Coincident Electroproduction and the Search for Delta 's in the Ground State of 3He. Phys Rev Lett 1996; 77:2396-2399. [PMID: 10061943 DOI: 10.1103/physrevlett.77.2396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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