E12 07 108 gmp precision measurement of the proton elastic cross section at high q 2
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E12-07-108 : ( GMp ) Precision Measurement of the Proton Elastic Cross Section at High Q 2. Vincent Sulkosky Massachusetts Institute of Technology f or the E12-07-108 Collaboration Spokespeople: J. Arrington, E. Christy, S. Gilad , B. Moffit , V. Sulkosky , B. Wojtsekhowski

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E12-07-108 : ( GMp ) Precision Measurement of the Proton Elastic Cross Section at High Q 2

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E12 07 108 gmp precision measurement of the proton elastic cross section at high q 2

E12-07-108: (GMp)Precision Measurement of theProton Elastic Cross Sectionat High Q2

Vincent Sulkosky

Massachusetts Institute of Technology

for the E12-07-108 Collaboration

Spokespeople: J. Arrington, E. Christy, S. Gilad, B. Moffit,

V. Sulkosky, B. Wojtsekhowski

Hall A CollaborationMeeting

December 10th, 2012


Introduction

Introduction


Goals for gmp

Goals forGMp

  • Accurately measure e-p elastic cross section in

    kinematics similar to other JLab form factor

    measurements

  • Improve accuracy of the cross section by as much as a

    factor of 4 (< 2%) over previous measurements

  • Key input to all form factors and many of other

    experiments, where elastic scattering is a background

  • Provide measurement of power scaling for GMp

    in the range Q2 = 7-14 GeV2

  • Approved for 24 PAC days


E12 07 108 gmp precision measurement of the proton elastic cross section at high q 2

Kinematics


E12 07 108 gmp precision measurement of the proton elastic cross section at high q 2

Kinematics

PAC Approved 24 days


Control of systematics

Control of Systematics

Planned improvements

  • Tracking efficiency

    • Include front chambers of FPP as third wire chamber

      with VDCs

  • Target density

    • Use precise optics to provide software cuts on vertex

    • Use race-track cell targets with vertical flow to

      minimize fluctuations

  • Solid Angle

    • A benefit of improved optics

    • Precise determination of target location using

      swing arm


Hrs detector stacks

HRS Detector Stacks

Use standard detectors including one plane of FPP

for additional tracking


Fpp front chambers

FPP (front chambers)

Problems: gas consumption

> 50 l/h HV trips often

due to gas, many dead

wires/some electronics

Done: repair of dead electronics

built parallel gas

distribution tests of each

wire/disconnect dead

Still to do: HV distribution in one

layer; gas distribution

should be as wide as a

straw block; tension test

for each wire

~ 100 wires need to

be restrung


E12 07 108 gmp precision measurement of the proton elastic cross section at high q 2

VDC Improvements

  • Upgrade electronics to use

    1877S, which allows sparsification

  • Replace aging A/D cards and will reuse MAD cards

  • Provide very good stability against

    oscillations and rate capability

    of 8 MHz (in full chamber)


E12 07 108 gmp precision measurement of the proton elastic cross section at high q 2

Gas Cherenkov Improvements

  • Reflectivity measurements of HRS GCC mirrors will begin this month

  • After initial measurements, recoating of mirrors

  • Check and replace PMTs as needed

  • Cosmic mirror calibration


E12 07 108 gmp precision measurement of the proton elastic cross section at high q 2

Target Configuration

LH2: 15 cm Racetrack:

  • Vertical flow design

  • Dedicated studies of density

  • Luminosity monitors in

    datastream

    Solid Al Foils (Dummy):

    Endcap subtraction

    Carbon Optics Targets:

    1-2 cm spacing along zvertex for extended target acceptance

Solid targets/Endcaps measured with x-ray attenuation


Hrs optics and angle

HRS Optics and Angle

Wire target on strong arm, reproducibility of 100 microns sufficient, 20 microns is likely achievable


Expected precision

Expected Precision


Systematic uncertainties

Systematic Uncertainties


Systematic uncertainties1

Systematic Uncertainties


Tasks responsibilities

Tasks & Responsibilities


Tasks responsibilities cont

Tasks & Responsibilities (cont.)


Commitments in manpower

Commitments in Manpower

  • FPP work: Albert Shahinyan, GalustSargsyan and Karen (YerPHI)

  • HRS detectors:

    • Milan Dukic (NCCU technician) for three weeks

    • HamzaAtac (Temple) for two weeks

    • NSU student for one month

    • LongwuOu (MIT student) for one month

    • Kai Pan (UVa student) for two weeks

    • PuneetKhetarpal (FIU postdoc) for two weeks

    • John LeRose (JLab) part time

    • Mohamed NuhHashirRashad (ODU); DVCS graduate student

    • JinJin Pan (HU); graduate student (potential GMp student)

    • Yang Wang (WM); graduate student (potential GMp student)


Potential physics prospects

Potential Physics Prospects


Summary

Summary

  • Firstexperiment to run in the 12-GeV era with DVCS.

  • GMp will provide a baseline for the 21st century level of accuracy in form factor measurements by precisely measuring the cross section at Q2 up to 14 GeV2.

  • It is the only measurement of the cross section; key input to all form factors and many of other experiments

  • The DVCS luminosity × HRS-R solid angle (1/8 of GMpproposal) and restricted angle range of HRS-R allows for some parallel running of GMp during DVCS data taking.

  • Collaborators are welcome to participate; much work is required before 2014.


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