E02-013: at high Q2 Status of Analysis

Sergey Abrahamyan

Yerevan Physics Institute

for the E02-013 collaboration

Overview

Form factors

E02-013 Experiment

1.2 GeV2 analysis

Status

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E02-013 CollaborationUniversität Basel, CH-4056 Basel, Switzerland; University of Virginia, Charlottesville, VA 22903; Yerevan

Physics Institute, Yerevan 375036, Armenia; North Carolina A&T State University, Greensboro, NC 27411; Tel Aviv University, Tel Aviv, 69978 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 630090, Russia; Institute for Nuclear Physics Tomsk 634050, 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, 188350, Russia; Duke University and TUNL, Durham, NC 27708; Université Blaise Pascal/IN2P3, F-63177 Aubière, France; IPN Orsay B.P. n○1, F-91406, Orsay, France; CEA Saclay, DAPNIA/SPhN, F-91191 Gif sur Yvette, France; University of Maryland, College Park, MD 20742; INFN, Sezione di Sanitá and Institute Superiore di Sanitá, I-00161 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 60439.

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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, Carnegie Mellon University (graduated 2008),

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

• Master Students:– Tim Ngo, University of California (graduated 2007)

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Form FactorsFor electron scattering on point-like spin ½ unpolarized particle cross-section is:

where and

is Mott cross-section for electron scattering.

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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

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Fourier transform of charge and magnetization density distributions in Breit frame

Measurement Technique extracted by measuring quasielastic cross-sectionasymmetry in reaction.

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E02-013

E02-013 experiment ran February-May 2006

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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

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• Polarized 3He Target• spin exchange between optically pumped Rb-K mixture and 3He gas• 50% polarization achieved

Calibration

BigHand TOF calibration for

bars in 1-st plane, scale in ns.

Resolution ~ 350 ps

BigBite DC U1 plane resolution with new time offsets and positions.

Resolution < 200µm

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Quasielastic Events Selection

Q2 = 1.7 GeV2

Quasielastic selection based on

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Pmiss,|| vs W Pmiss,┴ vs W

Quasielastic Events SelectionNeutron arm momentum resolution on higher Q2 becomes less effective due to higher γ-factor

Q2 = 3.5 GeV2

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Pmiss,|| vs W Pmiss,┴ vs W

Quasielastic Events Selection Quasielastic selection based on

Q2 = 3.5 GeV2

Q2 = 1.7 GeV2

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Mmiss vs W

Quasielastic Cuts Summary

To select quasieleastic cuts applied on

Q2 = 1.7 GeV2 Q2 = 2.5 GeV2

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Q2 = 3.5 GeV2

Charge Identification

Cluster in NA should be correlated with veto-signal in space and in time

Proton contamination to neutron sample due to charge conversion before veto plane evaluated through uncharged/charged ratios for different targets

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Due to charge conversion in material before veto-layers charge misidentification may occur.

Proton contamination measured to be 10-25% which is within 5% agreement with MC

Target Polarization

50% Target polarization was achieved during E02-013 experiment.

For most part of the experiment value of target polarization was over 45%.

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Inelastic contribution and MC

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MC shows a good agreement with data on the lowest Q2=1.7 GeV2 point in both quasielastic and inelastic region.

Developed MC-simulation will be used to eliminate a proper cuts for quasielastic events selection on higher Q2 kinematic points.

FSI

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Isobar CurrentMeson Exchange Current

FSI Impulse 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 nucleonreinteracts with residual hadronic system

FSI and Charge Exchange effects will be calculated using the Generalized Eikonal Approximation (Misak Sargsian)

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 (not included in current results)

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Results

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StatusDone

BigHand and BigBite calibrations finalized 3 higher Q2 kinematic points data replayed with new

calibration for both electron and hadron detectors. Semifinal results for Q2 = 1.7, 2.5, 3.5 GeV2

Need to be finalized (end of June) Pion asymmetry contribution FSI correction Wider cuts (based on MC) to improve statistics Final results for Q2 = 1.7, 2.5, 3.5 GeV2

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