Radiative Corrections for polarized H(e,ep)

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Radiative Corrections for polarized H(e,ep)

• Chris Crawford
• Mass. Inst. of Tech.
• Jan. 24, 2002

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Outline

• Existing software
• SIMC (Hall C)
• MASCARAD
• Calculations
• Remaining work

• Introduction
• Higher order diagrams
• Hard vs. Soft photons
• Approximations
• Radiative cross section

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Internal Processes
Born
Bremsstrahlung
Vertex correction
Vacuum polarization
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External Processes

• Bremsstrahlung
• Multiple scattering
• Landau straggling
• Energy loss
• Simulate these with BLASTMC

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Hard v.s. Soft Photons

• Soft Photons within detector energy resolution
  ?E
• Multiple photon emission dominates at low
• Hard photons modify kinematics

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Radiative Cross Section

• Bethe Heitler, P.R.S.L. A146, 83 (1934)
• J. Schwinger, Phys. Rev. 76, 790 (1949)
• Mo Tsai, Rev. Mod. Phys. 41, 205 (1969)
• Inclusive cross section
• Soft photon approximation
• Peaking approximation
• Cutoff parameter ?E

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SIMC

• R. Ent et. al., Phys.Rev.C 64 054610 (2001)
• Soft photon approximation
• Multiple photon emission
• Two unphysical divergences

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SIMC

• Peaking approximation
• Radiation along initial, final electron
• Used for applying vertex correction

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MASCARAD

• A. Afanasev et. al., Phys.Rev.D 64, 113009
• Bardin Shumeiko, Nucl.Phys. B127, 242
• Covariant, no cutoff parameter

S.P.A.
Hard Photons
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MASCARAD

• The asymmetry is insensitive to ?

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Phase Space

• Change of variables for

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Coincidence

• Integrate over proton acceptance A
• Sharply peaked in ? and ?k

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Results from MASCARAD
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Results from MASCARAD
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Results from MASCARAD
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Results from MASCARAD
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Other Methods

• Reconstruction in hadronic variables
• Simplifies integration
• C code PRC, by Feng Xiong
• Based on POLRAD 2.0
• Others

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Remaining Work

• Incorporate into BLASTMC (userGen)
• Use external physics of GEANT
• Simulate proton acceptance
• Improvements
• Use peaking approx. residual
• Add arbitrary polarization angle
• Simulate e-p elastic experiments
• Generalize to other BLAST reactions