共查询到20条相似文献,搜索用时 31 毫秒
1.
Vlahovic B Voskanyan H Wijesooriya K Wojtsekhowski BB Woo RJ Xiong F Zainea GD Zhou Z 《Physical review letters》2000,84(7):1398-1402
The ratio of the proton's elastic electromagnetic form factors, G(E(p))/G(M(p)), was obtained by measuring P(t) and P(l), the transverse and the longitudinal recoil proton polarization, respectively. For elastic e-->p-->ep-->, G(E(p))/G(M(p)) is proportional to P(t)/P(l). Simultaneous measurement of P(t) and P(l) in a polarimeter provides good control of the systematic uncertainty. The results for the ratio G(E(p))/G(M(p)) show a systematic decrease as Q2 increases from 0.5 to 3.5 GeV2, indicating for the first time a definite difference in the spatial distribution of charge and magnetization currents in the proton. 相似文献
2.
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 《Physical review letters》2003,91(5):052301
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. 相似文献
3.
Madey R Semenov AY Taylor S Plaster B Aghalaryan A Crouse E MacLachlan G Tajima S Tireman W Yan C Ahmidouch A Anderson BD Arenhövel H Asaturyan R Baker OK Baldwin AR Barkhuff D Breuer H Carlini R Christy E Churchwell S Cole L Danagoulian S Day D Eden T Elaasar M Ent R Farkhondeh M Fenker H Finn JM Gan L Garrow K Gasparian A Gueye P Howell CR Hu B Jones MK Kelly JJ Keppel C Khandaker M Kim WY Kowalski S Lai A Lung A Mack D Manley DM Markowitz P Mitchell J Mkrtchyan H Opper AK Perdrisat C 《Physical review letters》2003,91(12):122002
We report new measurements of the ratio of the electric form factor to the magnetic form factor of the neutron, G(n)(E)/G(n)(M), obtained via recoil polarimetry from the quasielastic 2H(e-->,e(')n-->)1H reaction at Q2 values of 0.45, 1.13, and 1.45 (GeV/c)(2) with relative statistical uncertainties of 7.6% and 8.4% at the two higher Q2 points, which points have never been achieved in polarization measurements. 相似文献
4.
De Vita R Anghinolfi M Burkert VD Dodge GE Minehart R Taiuti M Weller H Adams G Amaryan MJ Anciant E Armstrong DS Asavapibhop B Asryan G Audit G Auger T Avakian H Bagdasaryan H Ball JP Barrow S Battaglieri M Beard K Bektasoglu M Bianchi N Biselli AS Boiarinov S Bonner BE Bosted P Bouchigny S Branford D Brooks WK Bueltmann S Calarco JR Capitani GP Carman DS Carnahan B Cazes A Ciciani L Cole PL Coleman A Connelly J Cords D Corvisiero P Crabb D Crannell H Cummings JP De Sanctis E Degtyarenko PV 《Physical review letters》2002,88(8):082001
The double spin asymmetry in the (-->)e(-->)p --> e(prime)pi(+)n reaction has been measured for the first time in the resonance region for four-momentum transfer Q2 = 0.35-1.5 GeV(2). Data were taken at Jefferson Lab with the CLAS detector using a 2.6 GeV polarized electron beam incident on a polarized solid NH3 target. Comparison with predictions of phenomenological models shows strong sensitivity to resonance contributions. Helicity-1/2 transitions are found to be dominant in the second and third resonance regions. The measured asymmetry is consistent with a faster rise with Q(2) of the helicity asymmetry A1 for the F(15)(1680) resonance than expected from the analysis of the unpolarized data. 相似文献
5.
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 《Physical review letters》2001,86(14):2959-2962
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. 相似文献
6.
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 Wojtsekhowski BB 《Physical review letters》2002,89(6):062301
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. 相似文献
7.
Pedlar TK Cronin-Hennessy D Gao KY Gong DT Hietala J Kubota Y Klein T Lang BW Li SZ Poling R Scott AW Smith A Dobbs S Metreveli Z Seth KK Tomaradze A Zweber P Ernst J Arms K Severini H Dytman SA Love W Mehrabyan S Mueller JA Savinov V Li Z Lopez A Mendez H Ramirez J Huang GS Miller DH Pavlunin V Sanghi B Shipsey IP Adams GS Anderson M Cummings JP Danko I Napolitano J He Q Muramatsu H Park CS Thorndike EH Coan TE Gao YS Liu F Artuso M Boulahouache C Blusk S Butt J Dorjkhaidav O Li J Menaa N 《Physical review letters》2005,95(26):261803
Using 20.7 pb(-1) of e(+)e(-) annihilation data taken at sq.rt(r) = 3.671 GeV with the CLEO-c detector, precision measurements of the electromagnetic form factors of the charged pion, charged kaon, and proton have been made for timelike momentum transfer of |Q(2)| = 13.48 GeV(2) by the reaction e(+)e(-) --> h(+)h(-). The measurements are the first ever with identified pions and kaons of |Q(2)| > 4 GeV(2), with the results F(13.48 GeV(2)) = 0.075 +/- 0.008(stat) +/- 0.005(syst) and F(K)(13.48 GeV(2)) = 0.063 +/- 0.004(stat) +/- 0.001(syst). The result for the proton, assuming G(p)(E) = G(p)(M), is G(p)(M)(13.48 GeV(2)) = 0.014 +/- 0.002(stat) +/- 0.001(syst), which is in agreement with earlier results. 相似文献
8.
Formaggio JA Yu J Adams T Alton A Avvakumov S de Barbaro L de Barbaro P Bernstein RH Bodek A Bolton T Brau J Buchholz D Budd H Bugel L Conrad JM Drucker RB Fleming BT Foster J Frey R Goldman J Goncharov M Harris DA Johnson RA Kim JH Koutsoliotas S Lamm MJ Marsh W Mason D McDonald J McFarland KS McNulty C Naples D Nienaber P Romosan A Sakumoto WK Schellman HM Shaevitz MH Spentzouris P Stern EG Suwonjandee N Vakili M Vaitaitis A Yang UK Zeller GP Zimmerman ED 《Physical review letters》2001,87(7):071803
The NuTeV experiment at Fermilab has used a sign-selected neutrino beam to perform a search for the lepton number violating process nu(mu)e(-)-->mu(-)nu(e), and to measure the cross section of the standard model inverse muon decay process nu(mu)e(-)-->mu(-)nu(e). NuTeV measures the inverse muon decay asymptotic cross-section slope sigma/E to be (13.8 +/- 1.2 +/- 1.4) x 10(-42) cm(2)/GeV. The experiment also observes no evidence for lepton number violation and places one of the most restrictive limits on the cross-section ratio sigma(nu(mu)e(-)-->mu(-)nu(e))/sigma(nu(mu)e(-)-->mu(-)nu(e)) < or = 1.7% at 90% C.L. for V-A couplings and < or = 0.6% for scalar couplings. 相似文献
9.
Crawford CB Sindile A Akdogan T Alarcon R Bertozzi W Booth E Botto T Calarco J Clasie B Degrush A Donnelly TW Dow K Dutta D Farkhondeh M Fatemi R Filoti O Franklin W Gao H Geis E Gilad S Haeberli W Hasell D Hersman W Holtrop M Karpius P Kohl M Kolster H Lee T Maschinot A Matthews J McIlhany K Meitanis N Milner RG Redwine RP Seely J Shinozaki A Sirca S Six E Smith T Tonguc B Tschalaer C Tsentalovich E Turchinetz W van den Brand JF van der Laan J Wang F Wise T Xiao Y Xu W Zhang C Zhou Z Ziskin V 《Physical review letters》2007,98(5):052301
We report the first precision measurement of the proton electric to magnetic form factor ratio from spin-dependent elastic scattering of longitudinally polarized electrons from a polarized hydrogen internal gas target. The measurement was performed at the MIT-Bates South Hall Ring over a range of four-momentum transfer squared Q2 from 0.15 to 0.65 (GeV/c)(2). Significantly improved results on the proton electric and magnetic form factors are obtained in combination with existing cross-section data on elastic electron-proton scattering in the same Q2 region. 相似文献
10.
Joo K Smith LC Burkert VD Minehart R Aznauryan IG Elouadrhiri L Stepanyan S Adams GS Amaryan MJ Anciant E Anghinolfi M Armstrong DS Asavapibhop B Audit G Auger T Avakian H Barrow S Bagdasaryan H Battaglieri M Beard K Bektasoglu M Bertozzi W Bianchi N Biselli AS Boiarinov S Bonner BE Brooks WK Calarco JR Capitani GP Carman DS Carnahan B Cole PL Coleman A Cords D Corvisiero P Crabb D Crannell H Cummings J De Sanctis E De Vita R Degtyarenko PV Demirchyan RA Denizli H Dennis LC Deppman A 《Physical review letters》2002,88(12):122001
Models of baryon structure predict a small quadrupole deformation of the nucleon due to residual tensor forces between quarks or distortions from the pion cloud. Sensitivity to quark versus pion degrees of freedom occurs through the Q2 dependence of the magnetic (M1+), electric (E1+), and scalar (S1+) multipoles in the gamma*p-->Delta(+)-->p pi(0) transition. We report new experimental values for the ratios E(1+)/M(1+) and S(1+)/M(1+) over the range Q2 = 0.4-1.8 GeV2, extracted from precision p(e,e(')p)pi(0) data using a truncated multipole expansion. Results are best described by recent unitary models in which the pion cloud plays a dominant role. 相似文献
11.
Zhu H Ahmidouch A Anklin H Arenhövel H Armstrong C Bernet C Boeglin W Breuer H Brindza P Brown D Bültmann S Carlini R Chant N Cowley A Crabb D Danagoulian S Day DB Eden T Ent R Farah Y Fatemi R Garrow K Harris C Hauger M Honegger A Jourdan J Kaufmann M Khandaker M Kubon G Lichtenstadt J Lindgren R Lourie R Lung A Mack D Malik S Markowitz P McFarlane K McKee P McNulty D Milanovich G Mitchell J Mkrtchyan H Mühlbauer M Petitjean T Prok Y Rohe D Rollinde E Rondon OA Roos P Sawafta R Sick I Smith C 《Physical review letters》2001,87(8):081801
We report the first measurement using a solid polarized target of the neutron electric form factor G(n)(E) via d-->(e-->,e(')n)p. G(n)(E) was determined from the beam-target asymmetry in the scattering of longitudinally polarized electrons from polarized deuterated ammonia ( 15ND3). The measurement was performed in Hall C at Thomas Jefferson National Accelerator Facility in quasifree kinematics with the target polarization perpendicular to the momentum transfer. The electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle segmented detector. We find G(n)(E) = 0.04632+/-0.00616(stat)+/-0.00341(syst) at Q2 = 0.495 (GeV/c)(2). 相似文献
12.
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 《Physical review letters》2002,88(14):142001
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. 相似文献
13.
Egiyan KS Asryan G Gevorgyan N Griffioen KA Laget JM Kuhn SE Adams G Amaryan MJ Ambrozewicz P Anghinolfi M Audit G Avakian H Bagdasaryan H Baillie N Ball JP Baltzell NA Barrow S Batourine V Battaglieri M Bedlinskiy I Bektasoglu M Bellis M Benmouna N Berman BL Biselli AS Blaszczyk L Bouchigny S Boiarinov S Bradford R Branford D Briscoe WJ Brooks WK Bültmann S Burkert VD Butuceanu C Calarco JR Careccia SL Carman DS Cazes A Chen S Cole PL Collins P Coltharp P Cords D Corvisiero P Crabb D Crede V 《Physical review letters》2007,98(26):262502
The reaction 2H(e,e'p)n has been studied with full kinematic coverage for photon virtuality 1.75NN transition is the primary contribution at higher momenta. 相似文献
14.
Ungaro M Stoler P Aznauryan I Burkert VD Joo K Smith LC Adams G Amarian M Ambrozewicz P Anghinolfi M Asryan G Audit G Avakian H Bagdasaryan H Ball JP Baltzell NA Barrow S Batourine V Battaglieri M Bedliski I Bektasoglu M Bellis M Benmouna N Berman BL Biselli AS Bonner BE Bouchigny S Boiarinov S Bradford R Branford D Briscoe WJ Brooks WK Bültmann S Butuceanu C Calarco JR Careccia SL Carman DS Cazes A Chen S Cole PL Coltharp P Cords D Corvisiero P Crabb D Cummings JP Sanctis ED Devita R 《Physical review letters》2006,97(11):112003
We report a new measurement of the exclusive electroproduction reaction gamma(*)p-->pi(0)p to explore the evolution from soft nonperturbative physics to hard processes via the Q(2) dependence of the magnetic (M(1+)), electric (E(1+)), and scalar (S(1+)) multipoles in the N-->Delta transition. 9000 differential cross section data points cover W from threshold to 1.4 GeV/c(2), 4pi center-of-mass solid angle, and Q(2) from 3 to 6 GeV(2)/c(2), the highest yet achieved. It is found that the magnetic form factor G(M)(*) decreases with Q(2) more steeply than the proton magnetic form factor, the ratio E(1+)/M(1+) is small and negative, indicating strong helicity nonconservation, and the ratio S(1+)/M(1+) is negative, while its magnitude increases with Q(2). 相似文献
15.
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 《Physical review letters》2007,99(20):202002
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. 相似文献
16.
H. Schmieden 《The European Physical Journal A - Hadrons and Nuclei》1998,1(4):427-433
The recoil proton polarization in the π0 production off the proton with longitudinally polarized electron beam has been studied as a means to measure quadrupole components
in the N to Δ transition. On top of the Δ resonance a high sensitivity to a possible Coulomb quadrupole excitation is found
in parallel kinematics. The ratio of S
1+/M
1+ multipole amplitudes can be determined from the ratio of the two in-scattering-plane recoil proton polarization components.
Avoiding the absolute measurement of the polarizations, such a ratio allows small experimental uncertainties. Furthermore,
the electron helicity independent proton polarization component enables the characterization of resonant and non-resonant
pieces.
Received: 3 November 1997 相似文献
17.
Qattan IA Arrington J Segel RE Zheng X Aniol K Baker OK Beams R Brash EJ Calarco J Camsonne A Chen JP Christy ME Dutta D Ent R Frullani S Gaskell D Gayou O Gilman R Glashausser C Hafidi K Hansen JO Higinbotham DW Hinton W Holt RJ Huber GM Ibrahim H Jisonna L Jones MK Keppel CE Kinney E Kumbartzki GJ Lung A Margaziotis DJ McCormick K Meekins D Michaels R Monaghan P Moussiegt P Pentchev L Perdrisat C Punjabi V Ransome R Reinhold J Reitz B Saha A Sarty A Schulte EC Slifer K Solvignon P Sulkosky V 《Physical review letters》2005,94(14):142301
We report the results of a new Rosenbluth measurement of the proton electromagnetic form factors at Q2 values of 2.64, 3.20, and 4.10 GeV2. Cross sections were determined by detecting the recoiling proton, in contrast to previous measurements which detected the scattered electron. Cross sections were determined to 3%, with relative uncertainties below 1%. The ratio mu(p)G(E)/G(M) was determined to 4%-8% and showed mu(p)G(E)/G(M) approximately 1. These results are consistent with, and much more precise than, previous Rosenbluth extractions. They are inconsistent with recent polarization transfer measurements of similar precision, implying a systematic difference between the techniques. 相似文献
18.
Maas FE Achenbach P Aulenbacher K Baunack S Capozza L Diefenbach J Grimm K Imai Y Hammel T von Harrach D Kabuss EM Kothe R Lee JH Lorente A Lopes Ginja A Nungesser L Schilling E Stephan G Weinrich C Altarev I Arvieux J Collin B Frascaria R Guidal M Kunne R Marchand D Morlet M Ong S van de Wiele J Kowalski S Plaster B Suleiman R Taylor S 《Physical review letters》2004,93(2):022002
We report on a measurement of the parity-violating asymmetry in the scattering of longitudinally polarized electrons on unpolarized protons at a Q2 of 0.230 (GeV/c)(2) and a scattering angle of theta (e) = 30 degrees - 40 degrees. Using a large acceptance fast PbF2 calorimeter with a solid angle of delta omega = 0.62 sr, the A4 experiment is the first parity violation experiment to count individual scattering events. The measured asymmetry is A(phys)=(-5.44+/-0.54(stat)+/-0.26(sys))x10(-6). The standard model expectation assuming no strangeness contributions to the vector form factors is A(0) = (-6.30+/-0.43) x 10(-6). The difference is a direct measurement of the strangeness contribution to the vector form factors of the proton. The extracted value is G(s)(E) + 0.225G(s)(M) = 0.039+/-0.034 or F(s)(1) + 0.130F(s)(2) = 0.032+/-0.028. 相似文献
19.
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 《Physical review letters》2011,106(13):132501
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(?) shows an enhancement of (2.3±0.6)% relative to the Born approximation at large ε. 相似文献
20.
F.H. Heimlich E. Rössle M. Köbberling J. Moritz K.H. Schmidt D. Wegener D. Zeller J.K. Bienlein J. Bleckwenn H. Dinter 《Nuclear Physics A》1974,228(3):478-492
Coincidence cross sections for the reactions 6Li(e, e′p) and 6Li(e, e′d) have been measured in the region of quasi-elastic scattering. Using incident electrons of 2.5 and 2.7 GeV, the four-momentum transfers to the proton were 6.6 fm?2, 10.0 fm?2 and 11.6 fm?2. The proton coincidence data agree with shell-model distributions assuming a Woods-Saxon potential and including short-range nucleon-nucleon correlations. The best fit to the deuteron coincidence data is obtained with a cluster wave function for the p-nucleons and a harmonic oscillator wave function for the s-nucleons taking into account the deuteron yield from the s-shell. The ratio of the deuteron cross section from 6Li divided by the elastic e-d scattering cross section depends only slightly on the four-momentum transfer and has a value of ≈ 2. 相似文献