共查询到20条相似文献,搜索用时 15 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.
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
3.
Abe F Amidei D Apollinari G Atac M Auchincloss P Baden AR Bamberger A Barbaro-Galtieri A Barnes VE Bedeschi F Behrends S Belforte S Bellettini G Bellinger J Bensinger J Beretvas A Berge JP Bertolucci S Bhadra S Binkley M Blair R Blocker C Booth AW Brandenburg G Brown D Buckley E Byon A Byrum KL Campagnari C Campbell M Carey R Carithers W Carlsmith D Carroll JT Cashmore R Cervelli F Chadwick K Chiarelli G Chinowsky W Cihangir S Clark AG Connor D Contreras M Cooper J Cordelli M Crane D Curatolo M 《Physical review D: Particles and fields》1991,44(1):29-52
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.
Blaylock GT Bolton T Brown JS Bunnell KO Burnett TH Cassell RE Coffman D Cook V Coward DH Dorfan DE Dubois GP Eigen G Eisenstein BI Freese T Gladding G Grab C Heusch CA Hitlin DG Izen JM Köpke L Li A Lockman WS Mallik U Matthews CG Mir R Mockett PM Mozley RF Nemati B Odian A Parker J Parrish L Partridge R Pitman D Sadrozinski HF Scarlatella M Schalk TL Schindler RH Seiden A Simopoulos C Stockdale IE Stockhausen W Thaler JJ Toki W Tripsas B Villa F Wasserbaech S Wattenberg A Weinstein AJ 《Physical review letters》1987,58(21):2171-2174
6.
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
7.
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
8.
9.
Rvachev MM Benmokhtar F Penel-Nottaris E Aniol KA Bertozzi W Boeglin WU Butaru F Calarco JR Chai Z Chang CC Chen JP Chudakov E Cisbani E Cochran A Cornejo J Dieterich S Djawotho P Duran W Epstein MB Finn JM Fissum KG Frahi-Amroun A Frullani S Furget C Garibaldi F Gayou O Gilad S Gilman R Glashausser C Hansen JO Higinbotham DW Hotta A Hu B Iodice M Iomni R de Jager CW Jiang X Jones MK Kelly JJ Kox S Kuss M Laget JM De Leo R Lerose JJ Liatard E Lindgren R Liyanage N Lourie RW Malov S 《Physical review letters》2005,94(19):192302
We have studied the quasielastic 3He(e,e(')p)2H reaction in perpendicular coplanar kinematics, with the energy and the momentum transferred by the electron fixed at 840 MeV and 1502 MeV/c, respectively. The 3He(e,e(')p)2H cross section was measured for missing momenta up to 1000 MeV/c, while the A(TL) asymmetry was extracted for missing momenta up to 660 MeV/c. For missing momenta up to 150 MeV/c, the cross section is described by variational calculations using modern 3He wave functions. For missing momenta from 150 to 750 MeV/c, strong final-state interaction effects are observed. Near 1000 MeV/c, the experimental cross section is more than an order of magnitude larger than predicted by available theories. The A(TL) asymmetry displays characteristic features of broken factorization with a structure that is similar to that generated by available models. 相似文献
10.
Bai JZ Ban Y Bian JG Chen AD Chen HF Chen HS Chen JC Chen XD Chen YB Cheng BS Chi SP Chu YP Choi JB Cui XZ Dai YS Dong LY Du ZZ Dunwoodie W Fu HY Fu LP Gao CS Gu SD Guo YN Guo ZJ Han SW Han Y Harris FA He J He JT He KL He M He X Hong T Heng YK Hu GY Hu HM Hu QH Hu T Huang GS Huang XP Huang YZ Izen JM Ji XB Jiang CH Jin Y Jones BD Kang JS Ke ZJ Kim HJ Kim SK Kim TY Kong D Lai YF Li D Li HB Li HH Li J Li JC Li PQ Li QJ Li RY Li W Li WG Li XN Li XQ Liu B Liu F Liu F Liu HM Liu J Liu JP Liu TR 《Physical review letters》2002,88(10):101802
We report values of R = sigma(e(+)e(-)-->hadrons)/sigma(e(+)e(-)-->mu(+)mu(-)) for 85 center-of-mass energies between 2 and 5 GeV measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider. 相似文献
11.
We report high-precision calculations that correctly include the rearrangement channels by solving the modified Faddeev equations for energies between the Ps(n = 2) and H(n = 3) thresholds, which involve six and eight open channels. We find that 99% of the antihydrogen is formed in H(n = 2). Just above the Ps(n = 2) threshold the S, P, and D partial waves contribute nearly 1400pi(a(2)0) near the maximum. We find evidence that the induced long-range dipole potential is responsible for such a large H formation cross section. The possibility of utilizing this resonance to synthesize low-energy H is discussed. 相似文献
12.
Abe F Albrow MG Amendolia SR Amidei D Antos J Anway-Wiese C Apollinari G Areti H Atac M Auchincloss P Azfar F Azzi P Bacchetta N Badgett W Bailey MW Bao J de Barbaro P Barbaro-Galtieri A Barnes VE Barnett BA Bartalini P Bauer G Baumann T Bedeschi F Behrends S Belforte S Bellettini G Bellinger J Benjamin D Benlloch J Bensinger J Benton D Beretvas A Berge JP Bertolucci S Bhatti A Biery K Binkley M Bird F Bisello D Blair RE Blocker C Bodek A Bokhari W Bolognesi V Bortoletto D Boswell C Boulos T 《Physical review D: Particles and fields》1995,52(5):2624-2655
13.
14.
15.
Widhalm L Adachi I Aihara H Aushev T Bakich AM Balagura V Barberio E Bay A Bedny I Bhardwaj V Bitenc U Blyth S Bozek A Bracko M Brodzicka J Browder TE Chao Y Chen A Chen WT Cheon BG Chistov R Cho IS Choi Y Dalseno J Dash M Drutskoy A Eidelman S Goldenzweig P Golob B Ha H Haba J Hayasaka K Hayashii H Hazumi M Heffernan D Hoshi Y Hou WS Hsiung YB Hyun HJ Iijima T Inami K Ishikawa A Ishino H Itoh R Iwasaki M Iwasaki Y Kah DH Kang JH Kapusta P Katayama N Kawai H Kawasaki T Kichimi H Kim SK Kim YJ 《Physical review letters》2008,100(24):241801
We present a measurement of the branching fraction B(D{s}{+}-->mu{+}nu{mu}) using a 548 fb{-1} data sample collected by the Belle experiment at the KEKB e{+}e{-} collider. The D{s} momentum is determined by reconstruction of the system recoiling against DKgammaX in events of the type e{+}e{-}-->D{s}{*}DKX, D{s}{*}-->D{s}gamma, where X represents additional pions or photons from fragmentation. This full-reconstruction method provides high resolution in the neutrino momentum and thus good background separation, equivalent to that achieved by experiments at the tau-charm factories. We obtain the branching fraction B(D{s}{+}-->mu{+}nu{mu})=[6.44+/-0.76(stat)+/-0.57(syst)]x10{-3}, implying a D{s} decay constant of f{D{s}}=[275+/-16(stat)+/-12(syst)] MeV. 相似文献
16.
One of the most challenging open problems in heavy quarkonium physics is the double charm production in e+e- annihilation at B factories. The measured cross section of e+e- --> J/psi + eta(c) is much larger than leading order (LO) theoretical predictions. With the nonrelativistic QCD factorization formalism, we calculate the next-to-leading order (NLO) QCD correction to this process. Taking all one loop self-energy, triangle, box, and pentagon diagrams into account, and factoring the Coulomb-singular term into the cc bound state wave function, we get an ultraviolet and infrared finite correction to the cross section of e+e- --> J/psi + eta(c) at sqrt[s] = 10:6 GeV. We find that the NLO QCD correction can substantially enhance the cross section with a K factor (the ratio of NLO to LO) of about 1.8-2.1; hence, it greatly reduces the large discrepancy between theory and experiment. 相似文献
17.
Besson D Pedlar TK Cronin-Hennessy D Gao KY Gong DT Hietala J Kubota Y Klein T Lang BW 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 Li J Menaa N Mountain R 《Physical review letters》2006,96(9):092002
We measure the cross section for e+e- -->psi(3770) -->hadrons at Ec.m.=3773 MeV to be (6.38+/-0.08(+0.41)(-0.30) nb using the CLEO detector at the CESR e+e- collider. The difference between this and the e+e- -->psi(3770) -->DD cross section at the same energy is found to be (-0.01+/-0.08(+0.41)(-0.30) nb. With the observed total cross section, we extract Gamma(ee)(psi(3770))=(0.204+/-0.003(+0.041)(-0.027) keV. Uncertainties shown are statistical and systematic, respectively. 相似文献
18.
Th. Pospischil P. Bartsch D. Baumann R. Böhm K. Bohinc M. Ding S. Derber M.O. Distler D. Elsner I. Ewald J. Friedrich J.M. Friedrich S. Grözinger S. Hedicke P. Jennewein J. Jourdan M. Kahrau F. Klein K.W. Krygier J. Lac A. Liesenfeld S. Malov J. McIntyre H. Merkel P. Merle U. Müller R. Neuhausen M. Potokar R.D. Ransome D. Rohe G. Rosner J. Sanner H. Schmieden M. Seimetz S. Širca I. Sick O. Strähle A. Süle A. Wagner Th. Walcher M. Weis 《The European Physical Journal A - Hadrons and Nuclei》2001,12(1):125-127
The polarization transfer from longitudinally polarized electrons to protons in the elastic scattering p(
e, e'
p) has been measured around Q2 = 0.4 (GeV/c)2 with the three-spectrometer facility at the Mainz microtron MAMI. From this polarization transfer the ratio G
Ep/(G
Mp/μp) has been determined. The ratio is found to be slightly less than unity in agreement with recent results from other laboratories
and from the Rosenbluth separation of cross-sections measured with unpolarized electrons.
Received: 26 July 2001 / Accepted: 25 September 2001 相似文献
19.
Abe F Albrow MG Amendolia SR Amidei D Antos J Anway-Wiese C Apollinari G Areti H Atac M Auchincloss P Azfar F Azzi P Bacchetta N Badgett W Bailey MW Bao J de Barbaro P Barbaro-Galtieri A Barnes VE Barnett BA Bartalini P Bauer G Baumann T Bedeschi F Behrends S Belforte S Bellettini G Bellinger J Benjamin D Benlloch J Bensinger J Benton D Beretvas A Berge JP Bertolucci S Bhatti A Biery K Binkley M Bird F Bisello D Blair RE Blocker C Bodek A Bokhari W Bolognesi V Bortoletto D Boswell C Boulos T 《Physical review letters》1996,76(17):3070-3075
20.
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