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Search Results: 1 - 10 of 191276 matches for " D. Spayde "
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Parity Violation in Elastic Electron-Proton Scattering and the Proton's Strange Magnetic Form Factor
SAMPLE collaboration,D. T. Spayde
Physics , 1999, DOI: 10.1103/PhysRevLett.84.1106
Abstract: We 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 +- 0.73 ppm 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.
The Strange Quark Contribution to the Proton's Magnetic Moment
SAMPLE collaboration,D. T. Spayde
Physics , 2003, DOI: 10.1016/j.physletb.2004.01.002
Abstract: 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 GAe to determine the strange form factor GMs(Q2=0.1)=0.37 +- 0.20 +- 0.26 +- 0.07. The extrapolation of GMs to its Q2=0 limit and comparison with calculations is also discussed.
The SAMPLE Experiment and Weak Nucleon Structure
E. J. Beise,M. L. Pitt,D. T. Spayde
Physics , 2004, DOI: 10.1016/j.ppnp.2004.07.002
Abstract: One of the key elements to understanding the structure of the nucleon is the role of its quark-antiquark sea in its ground state properties such as charge, mass, magnetism and spin. In the last decade, parity-violating electron scattering has emerged as an important tool in this area, because of its ability to isolate the contribution of strange quark-antiquark pairs to the nucleon's charge and magnetism. The SAMPLE experiment at the MIT-Bates Laboratory, which has been focused on s-sbar contributions to the proton's magnetic moment, was the first of such experiments and its program has recently been completed. In this paper we give an overview of some of the experimental aspects of parity-violating electron scattering, briefly review the theoretical predictions for strange quark form factors, summarize the SAMPLE measurements, and place them in context with the program of experiments being carried out at other electron scattering facilities such as Jefferson Laboratory and the Mainz Microtron.
An Energy Feedback System for the MIT/Bates Linear Accelerator
D. H. Barkhuff,S. P. Wells,T. Averett,D. H. Beck,E. J. Beise,D. Cheever,G. Dodson,S. Kowalski,R. D. McKeown,B. A. Mueller,M. Pitt,D. Spayde,C. Tschalaer,A. Zolfaghari
Physics , 1999, DOI: 10.1016/S0168-9002(00)00260-6
Abstract: We report the development and implementation of an energy feedback system for the MIT/Bates Linear Accelerator Center. General requirements of the system are described, as are the specific requirements, features, and components of the system unique to its implementation at the Bates Laboratory. We demonstrate that with the system in operation, energy fluctuations correlated with the 60 Hz line voltage and with drifts of thermal origin are reduced by an order of magnitude.
Measurement of the vector analyzing power in elastic electron-proton scattering as a probe of double photon exchange amplitudes
S. P. Wells,T. Averett,D. Barkhuff,D. H. Beck,E. J. Beise,C. Benson,H. Breuer,R. Carr,S. Covrig,J. DelCorso,G. Dodson,C. Eppstein,M. Farkhondeh,B. W. Filippone,T. Forest,P. Frasier,R. Hasty,T. M. Ito,C. Jones,W. Korsch,S. Kowalski,P. Lee,E. Maneva,K. McCarty,R. D. McKeown,J. Mikell,B. Mueller,P. Naik,M. L. Pitt,J. Ritter,V. Savu,D. T. Spayde,M. Sullivan,R. Tieulent,E. Tsentalovich,B. Yang,T. Zwart
Physics , 2000, DOI: 10.1103/PhysRevC.63.064001
Abstract: We report the first measurement of the vector analyzing power in inclusive transversely polarized elastic electron-proton scattering at Q^2 = 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 electromagnetic 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.
First Determination of the Weak Charge of the Proton
Qweak Collaboration,D. Androic,D. S. Armstrong,A. Asaturyan,T. Averett,J. Balewski,J. Beaufait,R. S. Beminiwattha,J. Benesch,F. Benmokhtar,J. Birchall,R. D. Carlini,G. D. Cates,J. C. Cornejo,S. Covrig,M. M. Dalton,C. A. Davis,W. Deconinck,J. Diefenbach,J. F. Dowd,J. A. Dunne,D. Dutta,W. S. Duvall,M. Elaasar,W. R. Falk,J. M. Finn,T. Forest,D. Gaskell,M. T. W. Gericke,J. Grames,V. M. Gray,K. Grimm,F. Guo,J. R. Hoskins,K. Johnston,D. Jones,M. Jones,R. Jones,M. Kargiantoulakis,P. M. King,E. Korkmaz,S. Kowalski,J. Leacock,J. Leckey,A. R. Lee,J. H. Lee,L. Lee,S. MacEwan,D. Mack,J. A. Magee,R. Mahurin,J. Mammei,J. W. Martin,M. J. McHugh,D. Meekins,J. Mei,R. Michaels,A. Micherdzinska,A. Mkrtchyan,H. Mkrtchyan,N. Morgan,K. E. Myers,A. Narayan,L. Z. Ndukum,V. Nelyubin,Nuruzzaman,W. T. H van Oers,A. K. Opper,S. A. Page,J. Pan,K. D. Paschke,S. K. Phillips,M. L. Pitt,M. Poelker,J. F. Rajotte,W. D. Ramsay,J. Roche,B. Sawatzky,T. Seva,M. H. Shabestari,R. Silwal,N. Simicevic,G. R. Smith,P. Solvignon,D. T. Spayde,A. Subedi,R. Subedi,R. Suleiman,V. Tadevosyan,W. A. Tobias,V. Tvaskis,B. Waidyawansa,P. Wang,S. P. Wells,S. A. Wood,S. Yang,R. D. Young,S. Zhamkochyan
Physics , 2013, DOI: 10.1103/PhysRevLett.111.141803
Abstract: The Qweak experiment has measured the parity-violating asymmetry in polarized e-p elastic scattering at Q^2 = 0.025(GeV/c)^2, employing 145 microamps of 89% longitudinally polarized electrons on a 34.4cm long liquid hydrogen target at Jefferson Lab. The results of the experiment's commissioning run are reported here, constituting approximately 4% of the data collected in the experiment. From these initial results the measured asymmetry is Aep = -279 +- 35 (statistics) +- 31 (systematics) ppb, which is the smallest and most precise asymmetry ever measured in polarized e-p scattering. The small Q^2 of this experiment has made possible the first determination of the weak charge of the proton, QpW, by incorporating earlier parity-violating electron scattering (PVES) data at higher Q^2 to constrain hadronic corrections. The value of QpW obtained in this way is QpW(PVES) = 0.064 +- 0.012, in good agreement with the Standard Model prediction of QpW(SM) = 0.0710 +- 0.0007. When this result is further combined with the Cs atomic parity violation (APV) measurement, significant constraints on the weak charges of the up and down quarks can also be extracted. That PVES+APV analysis reveals the neutron's weak charge to be QnW(PVES+APV) = -0.975 +- 0.010.
Early Results from the Qweak Experiment
D. Androic,D. S. Armstrong,A. Asaturyan,T. Averett,J. Balewski,J. Beaufait,R. S. Beminiwattha,J. Benesch,F. Benmokhtar,J. Birchall,R. D. Carlini,G. D. Cates,J. C. Cornejo,S. Covrig,M. M. Dalton,C. A. Davis,W. Deconinck,J. Diefenbach,J. F. Dowd,J. A. Dunne,D. Dutta,W. S. Duvall,M. Elaasar,W. R. Falk,J. M. Finn,T. Forest,D. Gaskel,M. T. W. Gericke,J. Grames,V. M. Gray,K. Grimm,F. Guo,J. R. Hoskins,K. Johnston,D. Jones,M. Jones,R. Jones,M. Kargiantoulakis,P. M. King,E. Korkmaz,S. Kowalski,J. Leacock,J. Leckey,A. R. Lee,J. H. Lee,L. Lee,S. MacEwan,D. Mack,J. A. Magee,R. Mahurin,J. Mammei,J. Martin,M. J. McHugh,D. Meekins,J. Mei,R. Michaels,A. Micherdzinska,A. Mkrtchyan,H. Mkrtchyan,N. Morgan,K. E. Myers,A. Narayan,L. Z. Ndukum,V. Nelyubin,Nuruzzaman,W. T. H van Oers,A. K. Opper,S. A. Page,J. Pan,K. Paschke,S. K. Phillips,M. L. Pitt,M. Poelker,J. F. Rajotte,W. D. Ramsay,J. Roche,B. Sawatzky,T. Seva,M. H. Shabestari,R. Silwal,N. Simicevic,G. R. Smith,P. Solvignon,D. T. Spayde,A. Subedi,R. Subedi,R. Suleiman,V. Tadevosyan,W. A. Tobias,V. Tvaskis,B. Waidyawansa,P. Wang,S. P. Wells,S. A. Wood,S. Yang,R. D. Young,S. Zhamkochyan
Physics , 2013, DOI: 10.1051/epjconf/20146605002
Abstract: A subset of results from the recently completed Jefferson Lab Qweak experiment are reported. This experiment, sensitive to physics beyond the Standard Model, exploits the small parity-violating asymmetry in elastic ep scattering to provide the first determination of the protons weak charge Qweak(p). The experiment employed a 180 uA longitudinally polarized 1.16 GeV electron beam on a 35 cm long liquid hydrogen target. Scattered electrons corresponding to Q2 of 0.025 GeV2 were detected in eight Cerenkov detectors arrayed symmetrically around the beam axis. The goals of the experiment were to provide a measure of Qweak(p) to 4.2 percent (combined statistical and systematic error), which implies a measure of sin2(thetaw) at the level of 0.3 percent, and to help constrain the vector weak quark charges C1u and C1d. The experimental method is described, with particular focus on the challenges associated with the worlds highest power LH2 target. The new constraints on C1u and C1d provided by the subset of the experiments data analyzed to date will also be shown, together with the extracted weak charge of the neutron.
The Qweak Experiment: A Search for New Physics at the TeV Scale via a Measurement of the Proton's Weak Charge
R. D. Carlini,J. M. Finn,S. Kowalski,S. A. Page,D. S. Armstrong,A. Asaturyan,T. Averett,J. Benesch,J. Birchall,P. Bosted,A. Bruell,C. L. Capuano,G. Cates,C. Carrigee,S. Chattopadhyay,S. Covrig,C. A. Davis,K. Dow,J. Dunne,D. Dutta,R. Ent,J. Erler,W. Falk,H. Fenker,T. A. Forest,W. Franklin,D. Gaskell,M. Gericke,J. Grames,K. Grimm,F. W. Hersman,D. Higinbotham,M. Holtrop,J. R. Hoskins,K. Johnston,E. Ihloff,M. Jones,R. Jones,K. Joo,J. Kelsey,C. Keppel,M. Khol,P. King,E. Korkmaz,J. Leacock,J. P. Leckey,L. Lee,A. Lung,D. Mack,S. Majewski,J. Mammei,J. Martin,D. Meekins,A. Micherdzinska,A. Mkrtchyan,H. Mkrtchyan,N. Morgan,K. E. Myers,A. Narayan,A. K. Opper,J. Pan,K. Paschke,M. Pitt,M. Poelker,Y. Prok,W. D. Ramsay,M. Ramsey-Musolf,J. Roche,N. Simicevic,G. Smith,T. Smith,P. Souder,D. Spayde,B. E. Stokes,R. Suleiman,V. Tadevosyan,E. Tsentalovich,W. T. H. van Oers,W. Vulcan,P. Wang,S. Wells,S. A. Wood,S. Yang,R. Young,H. Zhu,C. Zorn
Physics , 2012,
Abstract: We propose a new precision measurement of parity-violating electron scattering on the proton at very low Q^2 and forward angles to challenge predictions of the Standard Model and search for new physics. A unique opportunity exists to carry out the first precision measurement of the proton's weak charge, $Q_W =1 - 4\sin^2\theta_W$. A 2200 hour measurement of the parity violating asymmetry in elastic ep scattering at Q^2=0.03 (GeV/c)^2 employing 180 $\mu$A of 85% polarized beam on a 35 cm liquid Hydrogen target will determine the proton's weak charge with approximately 4% combined statistical and systematic errors. The Standard Model makes a firm prediction of $Q_W$, based on the running of the weak mixing angle from the Z0 pole down to low energies, corresponding to a 10 sigma effect in this experiment.
Transverse Beam Spin Asymmetries at Backward Angles in Elastic Electron-Proton and Quasi-elastic Electron-Deuteron Scattering
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.
First Measurement of the Neutral Current Excitation of the Delta Resonance on a Proton Target
G0 Collaboration,D. Androic,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,J. Grames,M. T. W. Gericke,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,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
Physics , 2012,
Abstract: The parity-violating asymmetry arising from inelastic electron-nucleon scattering at backward angle (~95 degrees) near the Delta(1232) resonance has been measured using a hydrogen target. From this asymmetry, we extracted the axial transition form factor G^A_{N\Delta}, a function of the axial Adler form factors C^A_i. Though G^A_{N\Delta} has been previously studied using charged current reactions, this is the first measurement of the weak neutral current excitation of the Delta using a proton target. For Q^2 = 0.34 (GeV/c)^2 and W = 1.18 GeV, the asymmetry was measured to be -33.4 \pm (5.3)_{stat} \pm (5.1)_{sys} ppm. The value of G^A_{N\Delta} determined from the hydrogen asymmetry was -0.05 \pm (0.35)_{stat} \pm (0.34)_{sys} \pm (0.06)_{theory}. These findings agree within errors with theoretical predictions for both the total asymmetry and the form factor. In addition to the hydrogen measurement, the asymmetry was measured at the same kinematics using a deuterium target. The asymmetry for deuterium was determined to be -43.6 \pm (14.6)_{stat} \pm (6.2)_{sys} ppm.
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