E02-013: at high Q 2 Status of Analysis Sergey Abrahamyan Yerevan Physics Institute for the E collaboration

Overview  Form factors  E Experiment  1.2 GeV 2 analysis  Status 2Hall A Collaboration Meeting6/11/2009

E Collaboration Universität Basel, CH-4056 Basel, Switzerland; University of Virginia, Charlottesville, VA 22903; Yerevan Physics Institute, Yerevan , Armenia; North Carolina A&T State University, Greensboro, NC 27411; Tel Aviv University, Tel Aviv, Israel; Florida International University, Miami, FL 33199; University of Maryland, College Park, Maryland 20742; Ohio University, Athens, OH 45071; Thomas Jefferson National Accelerator Facility, Newport News, VA 23606; Mississippi State University, Mississippi State, MI 39762; Hampton University, Hampton, VA 23668; Southern University at New Orleans, New Orleans, LU 70126; Louisiana Tech University, Ruston, LU 71272; North Carolina Central University, Durham, NC 27707; Syracuse University, Syracuse, NY 13244; Kent State University, Kent, OH 44242; Norfolk State University, Norfolk, VA 23504; Old Dominion University, Norfolk, VA 23529; Carnegie Mellon University, Pittsburgh, PA 15213; University of Glasgow, Glasgow G12 8QQ, Scotland, U.K.; California State University Los Angeles Los Angeles, CA 90032; Massachusetts Institute of Technology, Cambridge, MA 02139; Budker Institute for Nuclear Physics Novosibirsk , Russia; Institute for Nuclear Physics Tomsk , Russia; University of New Hampshire, Durham, NH 03824; College of William and Mary, Williamsburg, VA 23187; Temple University, Philadelphia, PA 19122; Kharkov Institute of Physics and Technology Kharkov 61108, Ukraine; St. Petersburg Nuclear Physics Institute Gatchina, , Russia; Duke University and TUNL, Durham, NC 27708; Université Blaise Pascal/IN2P3, F Aubière, France; IPN Orsay B.P. n ○ 1, F-91406, Orsay, France; CEA Saclay, DAPNIA/SPhN, F Gif sur Yvette, France; University of Maryland, College Park, MD 20742; INFN, Sezione di Sanitá and Institute Superiore di Sanitá, I Rome Italy; Rutgers, The State University of New Jersey, Piscataway, NJ 08854; University of Massachusetts, Amherst, MA 01003; Kyungpook National University, Taegu City, South Korea; Madrid University, Madrid, Spain; University of Kentucky, Lexington, KY 40506; Argonne National Laboratory, Argonne, IL /11/2009Hall A Collaboration Meeting3

Analysis group Spokespersons: – Gordon Cates, University of Virginia – Nilanga Liyanage, University of Virginia – Bogdan Wojtsekhowski, Jefferson Laboratory Post Docs and analysis coordinators: – Robert Feuerbach, Jefferson Laboratory, College of William and Mary – Seamus Riordan, University of Virginia PhD Students: – Sergey Abrahamyan, Yerevan Physics Institute – Brandon Craver, University of Virginia – Aidan Kelleher, College of William and Mary – Ameya Kolarkar, University of Kentucky (graduated 2007) – Jonathan Miller, University of Maryland – Seamus Riordan, Carnegie Mellon University (graduated 2008) Master Students: – Tim Ngo, University of California (graduated 2007) 4Hall A Collaboration Meeting6/11/2009

Form Factors For electron scattering on point-like spin ½ unpolarized particle cross-section is: where and is Mott cross-section for electron scattering. 5Hall A Collaboration Meeting6/11/2009

Form Factors  Cross-section for electron scattering on structured particle in terms of Dirac and Pauli form factors is  In terms of Sachs form factors 6Hall A Collaboration Meeting6/11/2009 Fourier transform of charge and magnetization density distributions in Breit frame

Measurement Technique extracted by measuring quasielastic cross-section asymmetry in reaction. 7Hall A Collaboration Meeting6/11/2009

Experimental Setup Neutron Arm 7 scintillator planes for hadron detection 2 veto-detector planes for charge identification BigBite Dipole Magnet (1.0 T·m) 15 MWDC planes Scintillator (timing) plane 2-plane Electromagnetic Calorimeter 8Hall A Collaboration Meeting6/11/2009 Polarized 3 He Target spin exchange between optically pumped Rb-K mixture and 3 He gas 50% polarization achieved

E E experiment ran February-May Hall A Collaboration Meeting6/11/2009

Results 10Hall A Collaboration Meeting6/11/2009 Q 2 = 1.7, 2.5 and 3.5 GeV 2 The behavior of S = Q 2 F 2 /F 1 for u and d quarks is completely different from that of the proton and neutron. PRL 105, (2010) arXiv: v1(accepted for PRL)

Calibration BigBite Optics Calibration. Vertex Z position (mm) Resolution ~ 7 mm Vertex Z vs Vertical position on magnet No dependence except very extreme region 6/11/2009Hall A Collaboration Meeting11 Q 2 = 1.2 GeV 2

Calibration. BigBite momentum δp/p ~ 1% Momentum vs Vertical position on magnet No dependence except very extreme region 6/11/2009Hall A Collaboration Meeting12 Q 2 = 1.2 GeV 2

Quasielastic Events Selection Q 2 = 1.2 GeV 2 Quasielastic selection based on 13Hall A Collaboration Meeting6/11/2009 P miss,|| vs WP miss, ┴ vs W

Charge Identification Cluster in NA should be correlated with veto-signal in space and in time No N 2 data for 1.2 GeV 2 point. Proton contamination to neutron sample due to charge conversion before veto plane evaluated through MC. 14Hall A Collaboration Meeting6/11/2009 Due to charge conversion in material before veto-layers charge misidentification may occur. D p = 0.844

Physics Asymmetry and  To extract a physics asymmetry raw experimental asymmetry corrected on:  Accidental background  Proton contamination to neutron sample  Nitrogen dilution  Target Polarization  Beam Polarization  Extraction of includes:  Finite acceptance correction  FSI 15Hall A Collaboration Meeting6/11/2009

Preliminary Results 16Hall A Collaboration Meeting6/11/2009 Q 2 = 1.2 GeV 2 No FSI correction

Status Done  Q 2 = 1.7, 2.5, 3.5 GeV 2 results published  Reasonable calibration achieved for Q 2 = 1.2 GeV 2  Most of dilution factors needed for final result calculated  Preliminary 1.2 GeV 2 result achieved Need to be finalized  Final calibration  FSI correction  Final results for Q 2 = 1.2 GeV 2  Long paper 17Hall A Collaboration Meeting6/11/2009

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Preliminary Results 20Hall A Collaboration Meeting6/11/2009 Q 2 = 1.2 GeV 2 No FSI correction

FSI 6/11/2009Hall A Collaboration Meeting21 Isobar CurrentMeson Exchange Current FSIImpulse Approximation IC – the virtual photon produces isobar which reinteracts with residual nuclear system producing final hadronic state MEC – the virtual photon interacts with the exchanged (between two-nucleon system) mesons IA – virtual photon knocks-out the bound nucleon which propagates to the final state without further interactions FSI – in which the knocked-out nucleon reinteracts with residual hadronic system FSI and Charge Exchange effects will be calculated using the Generalized Eikonal Approximation (Misak Sargsian)