skip to main content

Title: Deeply virtual Compton scattering at 6 GeV

The authors propose a measurement of the Deep Virtual Compton Scattering process (DVCS) ep {yields} ep{gamma} in Hall A at Jefferson Lab with a 6 GeV beam. The authors are able to explore the onset of Q{sup 2} scaling, by measuring a beam helicity asymmetry for Q{sup 2} ranging from 1.5 to 2.5 GeV{sup 2} at x{sub B} {approx} 0.35. At this kinematics, the asymmetry is dominated by the DVCS Bethe-Heitler (BH) interference, which is proportional to the imaginary part of the DVCS amplitude amplified by the full magnitude of the BH amplitude. The imaginary part of the DVCS amplitude is expected to scale early. Indeed, the imaginary part of the forward Compton amplitude measured in deep inelastic scattering (via the optical theorem) scales at Q{sup 2} as low as 1 GeV{sup 2}. If the scaling regime is reached, they make an 8% measurement of the skewed parton distributions (SPD) contributing to the DVCS amplitude. Also, this experiment allows them to separately estimate the size of the higher-twist effects, since they are only suppressed by an additional factor 1/Q compared to the leading-twist term, and have a different angular dependence. They use a polarized electron beam and detect the scatteredmore » electron in the HRSe, the real photon in an electromagnetic calorimeter (under construction) and the recoil proton in a shielded scintillator array (to be constructed). This allows them to determine the difference in cross-sections for electrons of opposite helicities. This observable is directly linked to the SPD's. The authors estimate that 25 days of beam (600 hours) are needed to achieve this goal.« less
Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; « less
Publication Date:
OSTI Identifier:
835025
Report Number(s):
JLAB-PHY-00-79; DOE/ER/40150-3033
TRN: US0407424
DOE Contract Number:
AC05-84ER40150
Resource Type:
Journal Article
Resource Relation:
Other Information: No journal information given for this preprint; PBD: 1 Jun 2000
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (US)
Sponsoring Org:
USDOE Office of Energy Research (ER) (US)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; AMPLITUDES; ASYMMETRY; CALORIMETERS; COMPTON EFFECT; CONSTRUCTION; CROSS SECTIONS; DEEP INELASTIC SCATTERING; ELECTRON BEAMS; ELECTRONS; HELICITY; OPTICAL THEOREM; PARTONS; PHOSPHORS; PHOTONS; PROTONS