Physics
Permanent URI for this communityhttp://hdl.handle.net/1903/2269
Browse
10 results
Search Results
Item Strange-Quark Contributions to Parity-Violating Asymmetries in the Forward G0 Electron-Proton Scattering Experiment(American Physical Society, 2005-08-26) Armstrong, D.S.; Arvieux, J.; Asaturyan, R.; Averett, T.; Bailey, S.L.; Batigne, G.; Beck, D.H.; Beise, E.J.; Benesch, J.; Bimbot, L.; Birchall, J.; Korsch, W.; Kox, S.; Kuhn, J.; Lachniet, J.; Lee, L.; Lenoble, J.; Liatard, E.; Liu, J.; Loupias, B.; G0 Collaboration; Lung, A.; MacLachlan, G.A.; Marchand, D.; Martin, J.W.; McFarlane, K.W.; McKee, D.W.; McKeown, R.D.; Merchez, F.; Mkrtchyan, H.; Moffit, B.; Morlet, M.; Nakagawa, I.; Nakahara, K.; Nakos, M.; Neveling, R.; Niccolai, S.; Ong, S.; Page, S.; Papavassiliou, V.; Pate, S.F.; Phillips, S.K.; Pitt, M.L.; Poelker, M.; Porcelli, T.A.; Quemener, G.; Quinn, B.; Ramsay, W.D.; Rauf, A.W.; Real, J.-S.; Roche, J.; Roos, P.; Rutledge, G.A.; Secrest, J.; Simicevic, N.; Smith, G.R.; Spayde, D.T.; Stepanyan, S.; Stutzman, M.; Sulkosky, V.; Tadevosyan, V.; Tieulent, R.; van de Wiele, J.; van Oers, W.; Voutier, E.; G0 Collaboration; Vulcan, W.; Warren, G.; Wells, S.P.; Williamson, S.E.; Wood, S.A.; Yan, C.; Yun, J.; Zeps, V.; Biselli, A.; Bosted, P.; Boukobza, E.; Breuer, H.; Carlini, R.; Carr, R.; Chant, N.; Chao, Y.-C.; Chattopadhyay, S.; Clark, R.; Covrig, S.; Cowley, A.; Dale, D.; Davis, C.; Falk, W.; Finn, J.M.; Forest, T.; Franklin, G.; Furget, C.; Gaskell, D.; Grames, J.; Griffioen, K.A.; Grimm, K.; Guillon, B.; Guler, H.; Hannelius, L.; Hasty, R.; Hawthorne Allen, A.; Horn, T.; Johnston, K.; Jones, M.; Kammel, P.; Kazimi, R.; King, P.M.; Kolarkar, A.; Korkmaz, E.We have measured parity-violating asymmetries in elastic electron-proton scattering over the range of momentum transfers 0.12≤Q2≤1.0 GeV2. These asymmetries, arising from interference of the electromagnetic and neutral weak interactions, are sensitive to strange-quark contributions to the currents of the proton. The measurements were made at Jefferson Laboratory using a toroidal spectrometer to detect the recoiling protons from a liquid hydrogen target. The results indicate nonzero, Q2 dependent, strange-quark contributions and provide new information beyond that obtained in previous experiments.Item Cross-Section Measurement of Charged-Pion Photoproduction from Hydrogen and Deuterium(American Physical Society, 2003-06-11) Zhu, L.Y.; Arrington, J.; Averett, T.; Beise, E.; Calarco, J.; Chang, T.; Chen, J.P.; Chudakov, E.; Coman, M.; Clasie, B.; Crawford, C.; Dieterich, S.; Dohrmann, F.; Dutta, D.; Fissum, K.; Frullani, S.; Gao, H.; Gilman, R.; Glashausser, C.; Gomez, J.; Hafidi, K.; Hansen, J.-O.; Higinbotham, D.W.; Holt, R.J.; de Jager, C.W.; Jiang, X.; Kinney, E.; Kramer, K.; Kumbartzki, G.; LeRose, J.; Liyanage, N.; Mack, D.; Markowitz, P.; McCormick, K.; Meekins, D.; Meziani, Z.-E.; Michaels, R.; Mitchell, J.; Nanda, S.; Potterveld, D.; Ransome, R.; Reimer, P.E.; Reitz, B.; Saha, A.; Schulte, E.C.; Seely, J.; Sirca, S.; Strauch, S.; Sulkosky, V.; Vlahovic, B.; Weinstein, L.B.; Wijesooriya, K.; Williamson, C.F.; Wojtsekhowski, B.; Xiang, H.; Xiong, F.; Xu, W.; Zeng, J.; Zheng, X.; Jefferson Lab Hall A ColloborationWe have measured the differential cross section for the γn→π-p and γp→π+n reactions at θc.m.=90° in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at Eγ≳3.3 GeV exhibit a global scaling behavior for both π- and π+ photoproduction, consistent with the constituent counting rule and the existing π+ photoproduction data. Possible oscillations around the scaling value are suggested by these new data. The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive π- to π+ photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.Item Parity Violation in Elastic Electron-Proton Scattering and the Proton's Strange Magnetic Form Factor(American Physical Society, 2000-02-07) Spayde, D.T.; Averett, T.; Barkhuff, D.; Beck, D.H.; Beise, E.J.; Benson, C.; Breuer, H.; Carr, R.; Covrig, S.; DelCorso, J.; Dodson, G.; Dow, K.; Eppstein, C.; Farkhondeh, M.; Filippone, B.W.; Frazier, P.; Hasty, R.; Ito, T.M.; Jones, C.E.; Korsch, W.; Kowalski, S.; Lee, P.; Maneva, E.; McCarty, K.; McKeown, R.D.; Mikell, J.; Mueller, B.; Naik, P.; Pitt, M.; Ritter, J.; Savu, V.; Sullivan, M.; Tieulent, R.; Tsentalovich, E.; Wells, S.P.; Yang, B.; Zwart, T.; SAMPLE CollaborationWe report a new measurement of the parity-violating asymmetry in elastic electron scattering from the proton at backward scattering angles. This asymmetry is sensitive to the strange magnetic form factor of the proton as well as electroweak axial radiative corrections. The new measurement of A = -4.92±0.61±0.73ppm provides a significant constraint on these quantities. The implications for the strange magnetic form factor are discussed in the context of theoretical estimates for the axial corrections.Item Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering(American Physical Society, 2007-07-31) Armstrong, D.S.; Arvieux, J.; Asaturyan, R.; Averett, T.; Bailey, S.L.; Batigne, G.; Beck, D.H.; Beise, E.J.; Benesch, J.; Bimbot, L.; Birchall, J.; Roche, J.; Roos, P.; Rutledge, G.A.; Secrest, J.; Simicevic, N.; Smith, G.R.; Spayde, D.T.; Stepanyan, S.; Stutzman, M.; Sulkosky, V.; Tadevosyan, V.; Tieulent, R.; Van de Wiele, J.; van Oers, W.T.H.; Voutier, E.; Vulcan, W.; Warren, G.; Wells, S.P.; Williamson, S.E.; Wood, S.A.; Yan, C.; Yun, J.; Zeps, V.; G0 Collaboration; Biselli, A.; Bosted, P.; Boukobza, E.; Breuer, H.; Carlini, R.; Carr, R.; Chant, N.; Chao, Y.-C.; Chattopadhyay, S.; Clark, R.; Covrig, S.; Cowley, A.; Dale, D.; Davis, C.; Falk, W.; Finn, J.M.; Forest, T.; Franklin, G.; Furget, C.; Gaskell, D.; Grames, J.; Griffioen, K.A.; Grimm, K.; Guillon, B.; Guler, H.; Hannelius, L.; Hasty, R.; Hawthorne Allen, A.; Horn, T.; Johnston, K.; Jones, M.; Kammel, P.; Kazimi, R.; King, P.M.; Kolarkar, A.; Korkmaz, E.; Korsch, W.; Kox, S.; Kuhn, J.; Lachniet, J.; Lee, L.; Lenoble, J.; Liatard, E.; Liu, J.; Loupias, B.; Lung, A.; Marchand, D.; Martin, J.W.; McFarlane, K.W.; McKee, D.W.; McKeown, R.D.; Merchez, F.; Mkrtchyan, H.; Moffit, B.; Morlet, M.; Nakagawa, I.; Nakahara, K.; Neveling, R.; Ong, S.; Page, S.; Papavassiliou, V.; Pate, S.F.; Phillips, S.K.; Pitt, M.L.; Poelker, M.; Porcelli, T.A.; Quéméner, G.; Quinn, B.; Ramsay, W.D.; Rauf, A.W.; Real, J.-S.We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely polarized 3 GeV electrons from unpolarized protons at Q2=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. An provides a direct probe of the imaginary component of the 2γ exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments.Item Cross section measurements of charged pion photoproduction in hydrogen and deuterium from 1.1 to 5.5 GeV(2005-04) Zhu, L.Y.; Arrington, J.; Averett, T.; Beise, E.; Calarco, J.; Chang, T.; Chen, J.P.; Chudakov, E.; Coman, M.; Clasie, B.; Crawford, C.; Dieterich, S.; Dohrmann, F.; Dutta, D.; Fissum, K.; Frullani, S.; Gao, H.; Gilman, R.; Glashausser, C.; Gomez, J.; Hafidi, K.; Hansen, O.; Higinbotham, D.W.; Holt, R.J.; de Jager, C.W.; Jiang, X.; Kinney, E.; Kramer, K.; Kumbartzki, G.; LeRose, J.; Liyanage, N.; Mack, D.; Markowitz, P.; McCormick, K.; Meekins, D.; Meziani, Z.-E.; Michaels, R.; Mitchell, J.; Nanda, S.; Potterveld, D.; Ransome, R.; Reimer, P.E.; Reitz, B.; Saha, A.; Schulte, E.C.; Seely, J.; Sirca, S.; Strauch, S.; Sulkosky, V.; Vlahovic, B.; Weinstein, L.B.; Wijesooriya, K.; Williamson, C.; Wojtsekhowski, B.; Xiang, H.; Xiong, F.; Xu, W.; Zeng, J.; Zheng, X.; Jefferson Lab Hall A Collaboration; Jefferson Lab E94-104 CollaborationThe differential cross sections for the γn→π-p and the γp→π+n processes were measured at Jefferson Lab. The photon energies ranged from 1.1 to 5.5 GeV, corresponding to center-of-mass energies from 1.7 to 3.4 GeV. The pion center-of-mass angles varied from 50° to 110°. The π- and π+ photoproduction data both exhibit a global scaling behavior at high energies and high transverse momenta, consistent with the constituent counting rule prediction and the existing π+ data. The data suggest possible substructure of the scaling behavior, which might be oscillations around the scaling value. The data show an enhancement in the scaled cross section at center-of-mass energy near 2.2 GeV. The differential cross section ratios [dσ/dt(γn→π-p)/dσ/dt(γp→π+n)] at high energies and high transverse momenta can be described by calculations based on one-hard-gluon-exchange diagrams.Item Nuclear transparency with the γn⃗π-p process in 4He(2003-08) Dutta, D.; Xiong, F.; Zhu, L.Y.; Arrington, J.; Averett, T.; Beise, E.; Calarco, J.; Chang, T.; Chen, J.P.; Chudakov, E.; Coman, M.; Clasie, B.; Crawford, C.; Dieterich, S.; Dohrmann, F.; Fissum, K.; Frullani, S.; Gao, H.; Gilman, R.; Glashausser, C.; Gomez, J.; Hafidi, K.; Hansen, J.-O.; Higinbotham, D.W.; Holt, R.J.; de Jager, C.W.; Jiang, X.; Kinnery, E.; Kramer, K.; Kumbartzki, G.; LeRose, J.; Liyanage, N.; Mack, D.; Markowitz, P.; McCormick, K.; Meziani, Z.-E.; Michaels, R.; Nanda, S.; Potterveld, D.; Ransome, R.; Reimer, P.E.; Reitz, B.; Saha, A.; Schulte, E.C.; Seely, J.; Sirca, S.; Strauch, S.; Sulkosky, V.; Vlahovic, B.; Weinstein, L.B.; Wijesooriya, K.; Williamson, C.F.; Wojtsekhowski, B.; Xiang, H.; Xu, W.; Zeng, J.; Zheng, X.; Jefferson Lab E94104 CollaborationWe have measured the nuclear transparency of the fundamental process γn⃗π-p in 4He. These measurements were performed at Jefferson Lab in the photon energy range of 1.6–4.5 GeV and at θcmπ=70° and 90°. These measurements are the first of their kind in the study of nuclear transparency in photoreactions. They also provide a benchmark test of Glauber calculations based on traditional models of nuclear physics. The transparency results suggest deviations from the traditional nuclear physics picture. The momentum transfer dependence of the measured nuclear transparency is consistent with Glauber calculations that include the quantum chromodynamics phenomenon of color transparency.Item Strange Quark Contributions to Parity-Violating Asymmetries in the Forward G0 Electron-Proton Scattering Experiment(2010-01) Armstrong, D.S.; Arvieux, J.; Asaturyan, R.; Averett, T.; Bailey, S.L.; Batigne, G.; Beck, D.H.; Beise, E.J.; Benesch, J.; Bimbot, L.; Birchall, J.; Hannelius, L.; Hasty, R.; Hawthorne-Allen, A.; Horn, T.; Johnston, K.; Jones, M.; Kammel, P.; Kazimi, R.; King, P.M.; Kolarkar, A.; Korkmaz, E.; Korsch, W.; Kox, S.; Kuhn, J.; Lachniet, J.; Lee, L.; Lenoble, J.; Liatard, E.; Liu, J.; Loupias, B.; Lung, A.; MacLachlan, G.A.; Marchand, D.; Martin, J.W.; McFarlane, K.W.; McKee, D.W.; McKeown, R.D.; Merchez, F.; Mkrtchyan, H.; Moffit, B.; Morlet, M.; Nakagawa, I.; Nakahara, K.; Nakos, M.; Neveling, R.; Niccolai, S.; Ong, S.; Page, S.; Papavassiliou, V.; Pate, S.F.; Phillips, S.K.; Pitt, M.L.; Poelker, M.; Porcelli, T.A.; Quemener, G.; Quinn, B.; Ramsay, W.D.; Rauf, A.W.; Real, J.S.; Roche, J.; Roos, P.; Rutledge, G.A.; Secrest, J.; Simicevic, N.; Smith, G.R.; Spayde, D.T.; Stepanyan, S.; Stutzman, M.; Sulkosky, V.; Tadevosyan, V.; Tieulent, R.; van de Wiele, J.; van Oers, W.; Voutier, E.; Vulcan, W.; Warren, G.; Wells, S.P.; Williamson, S.E.; Wood, S.A.; Yan, C.; Yun, J.; Zeps, V.; Biselli, A.; Bosted, P.; Boukobza, E.; Breuer, H.; Carlini, R.; Carr, R.; Chant, N.; Chao, Y.C.; Chattopadhyay, S.; Clark, R.; Covrig, S.; Cowley, A.; Dale, D.; Davis, C.; Falk, W.; Finn, J.M.; Forest, T.; Franklin, G.; Furget, C.; Gaskell, D.; Grames, J.; Griffioen, K.A.; Grimm, K.; Guillon, B.; Guler, H.We have measured parity-violating asymmetries in elastic electron-proton scattering over the range of momentum transfers 0.12 ≤ Q2 ≤ 1.0 GeV2. These asymmetries, arising from interference of the electromagnetic and neutral weak interactions, are sensitive to strange quark contributions to the currents of the proton. The measurements were made at JLab using a toroidal spectrom- eter to detect the recoiling protons from a liquid hydrogen target. The results indicate non-zero, Q2 dependent, strange quark contributions and provide new information beyond that obtained in previous experiments.Item The Strange Quark Contribution to the Proton’s Magnetic Moment(2004-03) Spayde, D.T.; Averett, T.; Barkhuff, D.; Beck, D.H.; Beise, E.J.; Breuer, H.; Carr, R.; Covrig, S.; Dodson, G.; Dow, K.; Farkhondeh, M.; Filippone, B.W.; Franklin, W.; Hasty, R.; Ito, T.M.; Korsch, W.; Kowalski, S.; McKeown, R.D.; Mueller, B.; Pitt, M.L.; Ramsey-Musolf, M.J.; Ritter, J.; Tieulent, R.; Tsentalovich, E.; Wells, S.P.; Yang, B.; Zwart, T.We report a new determination of the strange quark contribution to the proton’s magnetic form factor at a four-momentum transfer Q2 = 0.1(GeV/c)2 from parity-violating e-p elastic scattering. The result uses a revised analysis of data from the SAMPLE experiment which was carried out at the MIT-Bates Laboratory. The data are combined with a calculation of the proton’s axial form factor GeA to determine the strange form factor GsM (Q2=0.1)=0.37±0.20±0.26±0.07. The extrapolation of GsM to its Q2 = 0 limit and comparison with calculations is also discussed.Item Parity-violating Electron Deuteron Scattering and the Proton’s Neutral Weak Axial Vector Form Factor(2004-03) Ito, T.M.; Averett, T.; Barkhuff, D.; Batigne, G.; Beck, D.H.; Beise, E.J.; Blake, A.; Breuer, H.; Carr, R.; Clasie, B.; Covrig, S.; Danagoulian, A.; Dodson, G.; Dow, K.; Dutta, D.; Farkhondeh, M.; Filippone, B.W.; Franklin, W.; Furget, C.; Gao, H.; Gao, J.; Gustafsson, K.; Hannelius, L.; Hasty, R.; Hawthorne-Allen, A.M.; Herda, M.C.; Jones, C.E.; King, P.; Korsch, W.; Kowalski, S.; Kox, S.; Kramer, K.; Lee, P.; Liu, J.; Martin, J.W.; McKeown, R.D.; Mueller, B.; Pitt, M.L.; Plaster, B.; Quemener, G.; Real, J. S.; Ritter, J.; Roche, J.; Savu, V.; Schiavilla, R.; Seely, J.; Spayde, D.; Suleiman, R.; Taylor, S.; Tieulent, R.; Tipton, B.; Tsentalovich, E.; Wells, S.P.; Yang, B.; Yuan, J.; Yun, J.; Zwart, T.; SAMPLE CollaborationWe report on a new measurement of the parity-violating asymmetry in quasielastic electron scat- tering from the deuteron at backward angles at Q2 = 0.038 (GeV/c)2. This quantity provides a de- termination of the neutral weak axial vector form factor of the nucleon, which can potentially receive large electroweak corrections. The measured asymmetry A = −3.51 ± 0.57 (stat) ± 0.58 (sys) ppm is consistent with theoretical predictions. We also report on updated results of the previous experiment at Q2 = 0.091 (GeV/c)2, which are also consistent with theoretical predictions.Item Measurement of the vector analyzing power in elastic electron-proton scattering as a probe of double photon exchange amplitudes(2001-05) Wells, S.P.; Averett, T.; Barkhuff, D.; Beck, D.H.; Beise, E.J.; Benson, C.; Breuer, H.; Carr, R.; Covrig, S.; DelCorso, J.; Dodson, G.; Eppstein, C.; Farkhondeh, M.; Filippone, B.W.; Forest, T.; Frasier, P.; Hasty, R.; Ito, T.M.; Jones, C.; Korsch, W.; Kowalski, S.; Lee, P.; Maneva, E.; McCarty, K.; McKeown, R.D.; Mikell, J.; Mueller, B.; Naik, P.; Pitt, M.L; Ritter, J.; Savu, V.; Spayde, D.T.; Sullivan, M.; Tieulent, R.; Tsentalovich, E.; Yang, B.; Zwart, T.; SAMPLE CollaborationWe report the first measurement of the vector analyzing power in inclusive transversely polarized elastic electron-proton scattering at Q2 = 0.1 (GeV/c)2 and large scattering angles. This quantity should vanish in the single virtual photon exchange, plane wave impulse approximation for this reaction, and can therefore provide information on double photon exchange amplitudes for electro- magnetic interactions with hadronic systems. We find a non-zero value of A=-15.4±5.4 ppm. No calculations of this observable for nuclei other than spin 0 have been carried out in these kinematics, and the calculation using the spin orbit interaction from a charged point nucleus of spin 0 cannot describe these data.