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451. Polarization components in π0 photoproduction at photon energies up to 5.6 GeV.

Author

Luo W, Brash EJ, Gilman R, Jones MK, Meziane M, Pentchev L, Perdrisat CF, Puckett AJ, Punjabi V, Wesselmann FR, Ahmidouch A, Albayrak I, Aniol KA, Arrington J, Asaturyan A, Ates O, Baghdasaryan H, Benmokhtar F, Bertozzi W, Bimbot L, Bosted P, Boeglin W, Butuceanu C, Carter P, Chernenko S, Christy ME, Commisso M, Cornejo JC, Covrig S, Danagoulian S, Daniel A, Davidenko A, Day D, Dhamija S, Dutta D, Ent R, Frullani S, Fenker H, Frlez E, Garibaldi F, Gaskell D, Gilad S, Goncharenko Y, Hafidi K, Hamilton D, Higinbotham DW, Hinton W, Horn T, Hu B, Huang J, Huber GM, Jensen E, Kang H, Keppel C, Khandaker M, King P, Kirillov D, Kohl M, Kravtsov V, Kumbartzki G, Li Y, Mamyan V, Margaziotis DJ, Markowitz P, Marsh A, Matulenko Y, Maxwell J, Mbianda G, Meekins D, Melnik Y, Miller J, Mkrtchyan A, Mkrtchyan H, Moffit B, Moreno O, Mulholland J, Narayan A, Nuruzzaman, Nedev S, Piasetzky E, Pierce W, Piskunov NM, Prok Y, Ransome RD, Razin DS, Reimer PE, Reinhold J, Rondon O, Shabestari M, Shahinyan A, Shestermanov K, Širca S, Sitnik I, Smykov L, Smith G, Solovyev L, Solvignon P, Strakovsky II, Subedi R, Suleiman R, Tomasi-Gustafsson E, Vasiliev A, Veilleux M, Wood S, Ye Z, Zanevsky Y, Zhang X, Zhang Y, Zheng X, and Zhu L

Abstract

We present new data for the polarization observables of the final state proton in the (1)H(γ,p)π(0) reaction. These data can be used to test predictions based on hadron helicity conservation and perturbative QCD. These data have both small statistical and systematic uncertainties and were obtained with beam energies between 1.8 and 5.6 GeV and for π(0) scattering angles larger than 75° in the center-of-mass frame. The data extend the polarization measurements database for neutral pion photoproduction up to E(γ)=5.6 GeV. The results show a nonzero induced polarization above the resonance region. The polarization transfer components vary rapidly with the photon energy and π(0) scattering angle in the center-of-mass frame. This indicates that hadron helicity conservation does not hold and that the perturbative QCD limit is still not reached in the energy regime of this experiment.

Published
2012
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452. New precision limit on the strange vector form factors of the proton.

Author

Ahmed Z, Allada K, Aniol KA, Armstrong DS, Arrington J, Baturin P, Bellini V, Benesch J, Beminiwattha R, Benmokhtar F, Canan M, Camsonne A, Cates GD, Chen JP, Chudakov E, Cisbani E, Dalton MM, de Jager CW, De Leo R, Deconinck W, Decowski P, Deng X, Deur A, Dutta C, Franklin GB, Friend M, Frullani S, Garibaldi F, Giusa A, Glamazdin A, Golge S, Grimm K, Hansen O, Higinbotham DW, Holmes R, Holmstrom T, Huang J, Huang M, Hyde CE, Jen CM, Jin G, Jones D, Kang H, King P, Kowalski S, Kumar KS, Lee JH, LeRose JJ, Liyanage N, Long E, McNulty D, Margaziotis D, Meddi F, Meekins DG, Mercado L, Meziani ZE, Michaels R, Muñoz-Camacho C, Mihovilovic M, Muangma N, Myers KE, Nanda S, Narayan A, Nelyubin V, Nuruzzaman, Oh Y, Pan K, Parno D, Paschke KD, Phillips SK, Qian X, Qiang Y, Quinn B, Rakhman A, Reimer PE, Rider K, Riordan S, Roche J, Rubin J, Russo G, Saenboonruang K, Saha A, Sawatzky B, Silwal R, Sirca S, Souder PA, Sperduto M, Subedi R, Suleiman R, Sulkosky V, Sutera CM, Tobias WA, Urciuoli GM, Waidyawansa B, Wang D, Wexler J, Wilson R, Wojtsekhowski B, Zhan X, Yan X, Yao H, Ye L, Zhao B, and Zheng X

Abstract

The parity-violating cross-section asymmetry in the elastic scattering of polarized electrons from unpolarized protons has been measured at a four-momentum transfer squared Q2 = 0.624  GeV2 and beam energy E(b) = 3.48  GeV to be A(PV) = -23.80 ± 0.78(stat) ± 0.36(syst) parts per million. This result is consistent with zero contribution of strange quarks to the combination of electric and magnetic form factors G(E)(s) + 0.517G(M)(s) = 0.003 ± 0.010(stat) ± 0.004(syst) ± 0.009(ff), where the third error is due to the limits of precision on the electromagnetic form factors and radiative corrections. With this measurement, the world data on strange contributions to nucleon form factors are seen to be consistent with zero and not more than a few percent of the proton form factors.

Published
2012
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453. New measurements of high-momentum nucleons and short-range structures in nuclei.

Author

Fomin N, Arrington J, Asaturyan R, Benmokhtar F, Boeglin W, Bosted P, Bruell A, Bukhari MH, Christy ME, Chudakov E, Clasie B, Connell SH, Dalton MM, Daniel A, Day DB, Dutta D, Ent R, El Fassi L, Fenker H, Filippone BW, Garrow K, Gaskell D, Hill C, Holt RJ, Horn T, Jones MK, Jourdan J, Kalantarians N, Keppel CE, Kiselev D, Kotulla M, Lindgren R, Lung AF, Malace S, Markowitz P, McKee P, Meekins DG, Mkrtchyan H, Navasardyan T, Niculescu G, Opper AK, Perdrisat C, Potterveld DH, Punjabi V, Qian X, Reimer PE, Roche J, Rodriguez VM, Rondon O, Schulte E, Seely J, Segbefia E, Slifer K, Smith GR, Solvignon P, Tadevosyan V, Tajima S, Tang L, Testa G, Trojer R, Tvaskis V, Vulcan WF, Wasko C, Wesselmann FR, Wood SA, Wright J, and Zheng X

Abstract

We present new measurements of electron scattering from high-momentum nucleons in nuclei. These data allow an improved determination of the strength of two-nucleon correlations for several nuclei, including light nuclei where clustering effects can, for the first time, be examined. The data also include the kinematic region where three-nucleon correlations are expected to dominate.

Published
2012
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454. Search for effects beyond the born approximation in polarization transfer observables in e(over→)p elastic scattering.

Author

Meziane M, Brash EJ, Gilman R, Jones MK, Luo W, Pentchev L, Perdrisat CF, Puckett AJ, Punjabi V, Wesselmann FR, Ahmidouch A, Albayrak I, Aniol KA, Arrington J, Asaturyan A, Ates O, Baghdasaryan H, Benmokhtar F, Bertozzi W, Bimbot L, Bosted P, Boeglin W, Butuceanu C, Carter P, Chernenko S, Christy E, Commisso M, Cornejo JC, Covrig S, Danagoulian S, Daniel A, Davidenko A, Day D, Dhamija S, Dutta D, Ent R, Frullani S, Fenker H, Frlez E, Garibaldi F, Gaskell D, Gilad S, Goncharenko Y, Hafidi K, Hamilton D, Higinbotham DW, Hinton W, Horn T, Hu B, Huang J, Huber GM, Jensen E, Kang H, Keppel C, Khandaker M, King P, Kirillov D, Kohl M, Kravtsov V, Kumbartzki G, Li Y, Mamyan V, Margaziotis DJ, Markowitz P, Marsh A, Matulenko Y, Maxwell J, Mbianda G, Meekins D, Melnik Y, Miller J, Mkrtchyan A, Mkrtchyan H, Moffit B, Moreno O, Mulholland J, Narayan A, Nuruzzaman, Nedev S, Piasetzky E, Pierce W, Piskunov NM, Prok Y, Ransome RD, Razin DS, Reimer PE, Reinhold J, Rondon O, Shabestari M, Shahinyan A, Shestermanov K, Širca S, Sitnik I, Smykov L, Smith G, Solovyev L, Solvignon P, Subedi R, Suleiman R, Tomasi-Gustafsson E, Vasiliev A, Vanderhaeghen M, Veilleux M, Wojtsekhowski BB, Wood S, Ye Z, Zanevsky Y, Zhang X, Zhang Y, Zheng X, and Zhu L

Abstract

Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, G(E)/G(M), obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, we report measurements of polarization transfer observables in the elastic H(e[over →],e(')p[over →]) reaction for three different beam energies at a Q(2)=2.5  GeV(2), spanning a wide range of the kinematic parameter ε. The ratio R, which equals μ(p)G(E)/G(M) in the Born approximation, is found to be independent of ε at the 1.5% level. The ε dependence of the longitudinal polarization transfer component P(ℓ) shows an enhancement of (2.3±0.6)% relative to the Born approximation at large ε., (© 2011 American Physical Society)

Published
2011
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455. Precise extraction of the induced polarization in the 4He(e,e'p)3H reaction.

Author

Malace SP, Paolone M, Strauch S, Albayrak I, Arrington J, Berman BL, Brash EJ, Briscoe B, Camsonne A, Chen JP, Christy ME, Chudakov E, Cisbani E, Craver B, Cusanno F, Ent R, Garibaldi F, Gilman R, Glamazdin O, Glister J, Higinbotham DW, Hyde-Wright CE, Ilieva Y, de Jager CW, Jiang X, Jones MK, Keppel CE, Khrosinkova E, Kuchina E, Kumbartzki G, Lee B, Lindgren R, Margaziotis DJ, Meekins D, Michaels R, Park K, Pentchev L, Perdrisat CF, Piasetzky E, Punjabi VA, Puckett AJ, Qian X, Qiang Y, Ransome RD, Saha A, Sarty AJ, Schulte E, Solvignon P, Subedi RR, Tang L, Tedeschi D, Tvaskis V, Udias JM, Ulmer PE, Vignote JR, Wesselmann FR, Wojtsekhowski B, and Zhan X

Abstract

We measured with unprecedented precision the induced polarization P(y) in (4)He(e,e'p)(3)H at Q(2)=0.8 and 1.3  (GeV/c)(2). The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are overestimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin-independent charge-exchange term in the latter calculation.

Published
2011
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456. Scaling of the F2 structure function in nuclei and quark distributions at x>1.

Author

Fomin N, Arrington J, Day DB, Gaskell D, Daniel A, Seely J, Asaturyan R, Benmokhtar F, Boeglin W, Boillat B, Bosted P, Bruell A, Bukhari MH, Christy ME, Chudakov E, Clasie B, Connell SH, Dalton MM, Dutta D, Ent R, El Fassi L, Fenker H, Filippone BW, Garrow K, Hill C, Holt RJ, Horn T, Jones MK, Jourdan J, Kalantarians N, Keppel CE, Kiselev D, Kotulla M, Lindgren R, Lung AF, Malace S, Markowitz P, McKee P, Meekins DG, Miyoshi T, Mkrtchyan H, Navasardyan T, Niculescu G, Okayasu Y, Opper AK, Perdrisat C, Potterveld DH, Punjabi V, Qian X, Reimer PE, Roche J, Rodriguez VM, Rondon O, Schulte E, Segbefia E, Slifer K, Smith GR, Solvignon P, Tadevosyan V, Tajima S, Tang L, Testa G, Trojer R, Tvaskis V, Vulcan WF, Wasko C, Wesselmann FR, Wood SA, Wright J, and Zheng X

Abstract

We present new data on electron scattering from a range of nuclei taken in Hall C at Jefferson Lab. For heavy nuclei, we observe a rapid falloff in the cross section for x>1, which is sensitive to short-range contributions to the nuclear wave function, and in deep inelastic scattering corresponds to probing extremely high momentum quarks. This result agrees with higher energy muon scattering measurements, but is in sharp contrast to neutrino scattering measurements which suggested a dramatic enhancement in the distribution of the "superfast" quarks probed at x>1. The falloff at x>1 is noticeably stronger in 2H and 3He, but nearly identical for all heavier nuclei.

Published
2010
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457. Polarization transfer in the 4He(e,e'p)3H reaction at Q2=0.8 and 1.3 (GeV/c)2.

Author

Paolone M, Malace SP, Strauch S, Albayrak I, Arrington J, Berman BL, Brash EJ, Briscoe B, Camsonne A, Chen JP, Christy ME, Chudakov E, Cisbani E, Craver B, Cusanno F, Ent R, Garibaldi F, Gilman R, Glamazdin O, Glister J, Higinbotham DW, Hyde-Wright CE, Ilieva Y, de Jager CW, Jiang X, Jones MK, Keppel CE, Khrosinkova E, Kuchina E, Kumbartzki G, Lee B, Lindgren R, Margaziotis DJ, Meekins D, Michaels R, Park K, Pentchev L, Perdrisat CF, Piasetzky E, Punjabi VA, Puckett AJ, Qian X, Qiang Y, Ransome RD, Saha A, Sarty AJ, Schulte E, Solvignon P, Subedi RR, Tang L, Tedeschi D, Tvaskis V, Udias JM, Ulmer PE, Vignote JR, Wesselmann FR, Wojtsekhowski B, and Zhan X

Abstract

Proton recoil polarization was measured in the quasielastic 4He(e,e'p)3H reaction at Q{2}=0.8 and 1.3  (GeV/c){2} with unprecedented precision. The polarization-transfer coefficients are found to differ from those of the 1H(e,e'p) reaction, contradicting a relativistic distorted-wave approximation and favoring either the inclusion of medium-modified proton form factors predicted by the quark-meson coupling model or a spin-dependent charge-exchange final-state interaction. For the first time, the polarization-transfer ratio is studied as a function of the virtuality of the proton.

Published
2010
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458. Recoil polarization measurements of the proton electromagnetic form factor ratio to Q2 = 8.5  GeV2.

Author

Puckett AJ, Brash EJ, Jones MK, Luo W, Meziane M, Pentchev L, Perdrisat CF, Punjabi V, Wesselmann FR, Ahmidouch A, Albayrak I, Aniol KA, Arrington J, Asaturyan A, Baghdasaryan H, Benmokhtar F, Bertozzi W, Bimbot L, Bosted P, Boeglin W, Butuceanu C, Carter P, Chernenko S, Christy E, Commisso M, Cornejo JC, Covrig S, Danagoulian S, Daniel A, Davidenko A, Day D, Dhamija S, Dutta D, Ent R, Frullani S, Fenker H, Frlez E, Garibaldi F, Gaskell D, Gilad S, Gilman R, Goncharenko Y, Hafidi K, Hamilton D, Higinbotham DW, Hinton W, Horn T, Hu B, Huang J, Huber GM, Jensen E, Keppel C, Khandaker M, King P, Kirillov D, Kohl M, Kravtsov V, Kumbartzki G, Li Y, Mamyan V, Margaziotis DJ, Marsh A, Matulenko Y, Maxwell J, Mbianda G, Meekins D, Melnik Y, Miller J, Mkrtchyan A, Mkrtchyan H, Moffit B, Moreno O, Mulholland J, Narayan A, Nedev S, Nuruzzaman, Piasetzky E, Pierce W, Piskunov NM, Prok Y, Ransome RD, Razin DS, Reimer P, Reinhold J, Rondon O, Shabestari M, Shahinyan A, Shestermanov K, Sirca S, Sitnik I, Smykov L, Smith G, Solovyev L, Solvignon P, Subedi R, Tomasi-Gustafsson E, Vasiliev A, Veilleux M, Wojtsekhowski BB, Wood S, Ye Z, Zanevsky Y, Zhang X, Zhang Y, Zheng X, and Zhu L

Abstract

Among the most fundamental observables of nucleon structure, electromagnetic form factors are a crucial benchmark for modern calculations describing the strong interaction dynamics of the nucleon's quark constituents; indeed, recent proton data have attracted intense theoretical interest. In this Letter, we report new measurements of the proton electromagnetic form factor ratio using the recoil polarization method, at momentum transfers Q2=5.2, 6.7, and 8.5  GeV2. By extending the range of Q2 for which G(E)(p) is accurately determined by more than 50%, these measurements will provide significant constraints on models of nucleon structure in the nonperturbative regime.

Published
2010
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459. Probing cold dense nuclear matter.

Author

Subedi R, Shneor R, Monaghan P, Anderson BD, Aniol K, Annand J, Arrington J, Benaoum H, Benmokhtar F, Boeglin W, Chen JP, Choi S, Cisbani E, Craver B, Frullani S, Garibaldi F, Gilad S, Gilman R, Glamazdin O, Hansen JO, Higinbotham DW, Holmstrom T, Ibrahim H, Igarashi R, de Jager CW, Jans E, Jiang X, Kaufman LJ, Kelleher A, Kolarkar A, Kumbartzki G, Lerose JJ, Lindgren R, Liyanage N, Margaziotis DJ, Markowitz P, Marrone S, Mazouz M, Meekins D, Michaels R, Moffit B, Perdrisat CF, Piasetzky E, Potokar M, Punjabi V, Qiang Y, Reinhold J, Ron G, Rosner G, Saha A, Sawatzky B, Shahinyan A, Sirca S, Slifer K, Solvignon P, Sulkosky V, Urciuoli GM, Voutier E, Watson JW, Weinstein LB, Wojtsekhowski B, Wood S, Zheng XC, and Zhu L

Abstract

The protons and neutrons in a nucleus can form strongly correlated nucleon pairs. Scattering experiments, in which a proton is knocked out of the nucleus with high-momentum transfer and high missing momentum, show that in carbon-12 the neutron-proton pairs are nearly 20 times as prevalent as proton-proton pairs and, by inference, neutron-neutron pairs. This difference between the types of pairs is due to the nature of the strong force and has implications for understanding cold dense nuclear systems such as neutron stars.

Published
2008
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460. Measurements of the proton elastic-form-factor ratio mu pG p E/G p M at low momentum transfer.

Author

Ron G, Glister J, Lee B, Allada K, Armstrong W, Arrington J, Beck A, Benmokhtar F, Berman BL, Boeglin W, Brash E, Camsonne A, Calarco J, Chen JP, Choi S, Chudakov E, Coman L, Craver B, Cusanno F, Dumas J, Dutta C, Feuerbach R, Freyberger A, Frullani S, Garibaldi F, Gilman R, Hansen O, Higinbotham DW, Holmstrom T, Hyde CE, Ibrahim H, Ilieva Y, de Jager CW, Jiang X, Jones MK, Kang H, Kelleher A, Khrosinkova E, Kuchina E, Kumbartzki G, LeRose JJ, Lindgren R, Markowitz P, May-Tal Beck S, McCullough E, Meekins D, Meziane M, Meziani ZE, Michaels R, Moffit B, Norum BE, Oh Y, Olson M, Paolone M, Paschke K, Perdrisat CF, Piasetzky E, Potokar M, Pomatsalyuk R, Pomerantz I, Puckett A, Punjabi V, Qian X, Qiang Y, Ransome R, Reyhan M, Roche J, Rousseau Y, Saha A, Sarty AJ, Sawatzky B, Schulte E, Shabestari M, Shahinyan A, Shneor R, Sirca S, Slifer K, Solvignon P, Song J, Sparks R, Subedi R, Strauch S, Urciuoli GM, Wang K, Wojtsekhowski B, Yan X, Yao H, Zhan X, and Zhu X

Abstract

High-precision measurements of the proton elastic form-factor ratio, mu pG p E/G p M, have been made at four-momentum transfer, Q2, values between 0.2 and 0.5 GeV2. The new data, while consistent with previous results, clearly show a ratio less than unity and significant differences from the central values of several recent phenomenological fits. By combining the new form-factor ratio data with an existing cross-section measurement, one finds that in this Q2 range the deviation from unity is primarily due to G p E being smaller than expected.

Published
2007
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461. Longitudinal-transverse separations of deep-inelastic structure functions at low Q2 for hydrogen and deuterium.

Author

Tvaskis V, Christy ME, Arrington J, Asaturyan R, Baker OK, Blok HP, Bosted P, Boswell M, Bruell A, Cochran A, Cole L, Crowder J, Dunne J, Ent R, Fenker HC, Filippone BW, Garrow K, Gasparian A, Gomez J, Jackson HE, Keppel CE, Kinney E, Lapikás L, Liang Y, Lorenzon W, Lung A, Mack DJ, Martin JW, McIlhany K, Meekins D, Milner RG, Mitchell JH, Mkrtchyan H, Moreland B, Nazaryan V, Niculescu I, Opper A, Piercey RB, Potterveld DH, Rose B, Sato Y, Seo W, Smith G, Spurlock K, van der Steenhoven G, Stepanyan S, Tadevosian V, Uzzle A, Vulcan WF, Wood SA, Zihlmann B, and Ziskin V

Abstract

We report on a study of the longitudinal to transverse cross section ratio, R=sigmaL/sigmaT, at low values of x and Q2, as determined from inclusive inelastic electron-hydrogen and electron-deuterium scattering data from Jefferson Laboratory Hall C spanning the four-momentum transfer range 0.06

Published
2007
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462. Precision measurements of the nucleon strange form factors at Q2 approximately 0.1 GeV2.

Author

Acha A, Aniol KA, Armstrong DS, Arrington J, Averett T, Bailey SL, Barber J, Beck A, Benaoum H, Benesch J, Bertin PY, Bosted P, Butaru F, Burtin E, Cates GD, Chao YC, Chen JP, Chudakov E, Cisbani E, Craver B, Cusanno F, De Leo R, Decowski P, Deur A, Feuerbach RJ, Finn JM, Frullani S, Fuchs SA, Fuoti K, Gilman R, Glesener LE, Grimm K, Grames JM, Hansen JO, Hansknecht J, Higinbotham DW, Holmes R, Holmstrom T, Ibrahim H, de Jager CW, Jiang X, Katich J, Kaufman LJ, Kelleher A, King PM, Kolarkar A, Kowalski S, Kuchina E, Kumar KS, Lagamba L, LaViolette P, LeRose J, Lindgren RA, Lhuillier D, Liyanage N, Margaziotis DJ, Markowitz P, Meekins DG, Meziani ZE, Michaels R, Moffit B, Nanda S, Nelyubin V, Otis K, Paschke KD, Phillips SK, Poelker M, Pomatsalyuk R, Potokar M, Prok Y, Puckett A, Qian X, Qiang Y, Reitz B, Roche J, Saha A, Sawatzky B, Singh J, Slifer K, Sirca S, Snyder R, Solvignon P, Souder PA, Stutzman ML, Subedi R, Suleiman R, Sulkosky V, Tobias WA, Ulmer PE, Urciuoli GM, Wang K, Whitbeck A, Wilson R, Wojtsekhowski B, Yao H, Ye Y, Zhan X, Zheng X, Zhou S, and Ziskin V

Abstract

We report new measurements of the parity-violating asymmetry A(PV) in elastic scattering of 3 GeV electrons off hydrogen and 4He targets with approximately 6.0 degrees . The 4He result is A(PV)=(+6.40+/-0.23(stat)+/-0.12(syst))x10(-6). The hydrogen result is A(PV)=(-1.58+/-0.12(stat)+/-0.04(syst))x10(-6). These results significantly improve constraints on the electric and magnetic strange form factors G(E)(s) and G(M)(s). We extract G(E)(s)=0.002+/-0.014+/-0.007 at =0.077 GeV2, and G(E)(s)+0.09G(M)(s)=0.007+/-0.011+/-0.006 at =0.109 GeV2, providing new limits on the role of strange quarks in the nucleon charge and magnetization distributions.

Published
2007
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463. Parity-violating electron scattering from 4He and the strange electric form factor of the nucleon.

Author

Aniol KA, Armstrong DS, Averett T, Benaoum H, Bertin PY, Burtin E, Cahoon J, Cates GD, Chang CC, Chao YC, Chen JP, Choi S, Chudakov E, Craver B, Cusanno F, Decowski P, Deepa D, Ferdi C, Feuerbach RJ, Finn JM, Frullani S, Fuoti K, Garibaldi F, Gilman R, Glamazdin A, Gorbenko V, Grames JM, Hansknecht J, Higinbotham DW, Holmes R, Holmstrom T, Humensky TB, Ibrahim H, de Jager CW, Jiang X, Kaufman LJ, Kelleher A, Kolarkar A, Kowalski S, Kumar KS, Lambert D, LaViolette P, LeRose J, Lhuillier D, Liyanage N, Margaziotis DJ, Mazouz M, McCormick K, Meekins DG, Meziani ZE, Michaels R, Moffit B, Monaghan P, Munoz-Camacho C, Nanda S, Nelyubin V, Neyret D, Paschke KD, Poelker M, Pomatsalyuk R, Qiang Y, Reitz B, Roche J, Saha A, Singh J, Snyder R, Souder PA, Subedi R, Suleiman R, Sulkosky V, Tobias WA, Urciuoli GM, Vacheret A, Voutier E, Wang K, Wilson R, Wojtsekhowski B, and Zheng X

Abstract

We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 4He at an average scattering angle = 5.7 degrees and a four-momentum transfer Q2 = 0.091 GeV2 . From these data, for the first time, the strange electric form factor of the nucleon G(E)s can be isolated. The measured asymmetry of A(PV) = (6.72 +/- 0.84(stat) +/- 0.21(syst) x 10(-6) yields a value of G(E)s = -0.038 +/- 0.042(stat) +/- 0.010(syst), consistent with zero.

Published
2006
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464. Recoil polarization for delta excitation in pion electroproduction.

Author

Kelly JJ, Roché RE, Chai Z, Jones MK, Gayou O, Sarty AJ, Frullani S, Aniol K, Beise EJ, Benmokhtar F, Bertozzi W, Boeglin WU, Botto T, Brash EJ, Breuer H, Brown E, Burtin E, Calarco JR, Cavata C, Chang CC, Chant NS, Chen JP, Coman M, Crovelli D, De Leo R, Dieterich S, Escoffier S, Fissum KG, Garde V, Garibaldi F, Georgakopoulus S, Gilad S, Gilman R, Glashausser C, Hansen JO, Higinbotham DW, Hotta A, Huber GM, Ibrahim H, Iodice M, de Jager CW, Jiang X, Klimenko A, Kozlov A, Kumbartzki G, Kuss M, Lagamba L, Laveissière G, Lerose JJ, Lindgren RA, Liyanage N, Lolos GJ, Lourie RW, Margaziotis DJ, Marie F, Markowitz P, McAleer S, Meekins D, Michaels R, Milbrath BD, Mitchell J, Nappa J, Neyret D, Perdrisat CF, Potokar M, Punjabi VA, Pussieux T, Ransome RD, Roos PG, Rvachev M, Saha A, Sirca S, Suleiman R, Strauch S, Templon JA, Todor L, Ulmer PE, Urciuoli GM, Weinstein LB, Wijesooriya K, Wojtsekhowski B, Zheng X, and Zhu L

Abstract

We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W = 1.23 GeV at Q(2) = 1.0 (GeV/c)(2), obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re (S(1+)/M(1+)) = -(6.84 +/- 0.15)% and Re (E(1+)/M(1+)) = -(2.91 +/- 0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and ll(pi) < or = 1 truncation.

Published
2005
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465. Polarization transfer in the 4He(e-->,e'p-->)3H reaction up to Q2=2.6 (GeV/c)2.

Author

Strauch S, Dieterich S, Aniol KA, Annand JR, Baker OK, Bertozzi W, Boswell M, Brash EJ, Chai Z, Chen JP, Christy ME, Chudakov E, Cochran A, De Leo R, Ent R, Epstein MB, Finn JM, Fissum KG, Forest TA, Frullani S, Garibaldi F, Gasparian A, Gayou O, Gilad S, Gilman R, Glashausser C, Gomez J, Gorbenko V, Gueye PL, Hansen JO, Higinbotham DW, Hu B, Hyde-Wright CE, Ireland DG, Jackson C, de Jager CW, Jiang X, Jones C, Jones MK, Kellie JD, Kelly JJ, Keppel CE, Kumbartzki G, Kuss M, LeRose JJ, Livingston K, Liyanage N, Malov S, Margaziotis DJ, Meekins D, Michaels R, Mitchell JH, Nanda SK, Nappa J, Perdrisat CF, Punjabi VA, Ransome RD, Roché R, Rosner G, Rvachev M, Sabatie F, Saha A, Sarty A, Udias JM, Ulmer PE, Urciuoli GM, van den Brand JF, Vignote JR, Watts DP, Weinstein LB, Wijesooriya K, and Wojtsekhowski B

Abstract

We have measured the proton recoil polarization in the 4He(e-->,e(')p-->)4H reaction at Q(2)=0.5, 1.0, 1.6, and 2.6 (GeV/c)(2). The measured ratio of polarization transfer coefficients differs from a fully relativistic calculation, favoring the inclusion of a medium modification of the proton form factors predicted by a quark-meson coupling model. In addition, the measured induced polarizations agree reasonably well with the fully relativistic calculation indicating that the treatment of final-state interactions is under control.

Published
2003
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466. 2H(e,e(')p)n reaction at high recoil momenta.

Author

Ulmer PE, Aniol KA, Arenhövel H, Chen JP, Chudakov E, Crovelli D, Finn JM, Fissum KG, Gayou O, Gomez J, Hansen JO, De Jager CW, Jeschonnek S, Jones MK, Kuss M, LeRose JJ, Liang M, Lindgren RA, Malov S, Meekins D, Michaels R, Mitchell J, Perdrisat CF, Punjabi V, Roché R, Sabatie F, Saha A, Suleiman R, Todor L, and Wojtsekhowski BB

Abstract

The 2H(e,e(')p)n cross section was measured in Hall A of the Thomas Jefferson National Accelerator Facility near the top of the quasielastic peak (x(Bj)=0.964) at a four-momentum transfer squared, Q(2)=0.665 (GeV/c) (2) (omega=0.368 GeV, W=2.057 GeV), and for recoil momenta up to 550 MeV/c. The measured cross section deviates by 1-2sigma from a state-of-the-art calculation at low recoil momenta. At high recoil momenta the cross section is well described by the same calculation; however, in this region, final-state interactions and interaction currents are predicted to be large, and alternative choices of nucleon-nucleon potential and nucleon current operator may result in significant spread in the calculations.

Published
2002
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