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Radiative Corrections for polarized H(e,ep)

This presentation by Chris Crawford from MIT explores the intricate world of radiative corrections in polarized H(e,ep) reactions. It delves into higher-order diagrams, distinguishing between hard and soft photons, and discusses their impact on the radiative cross-section. The study also reviews existing software tools like SIMC and MASCARAD, showcasing their capabilities in simulating internal and external processes such as bremsstrahlung and vacuum polarization. The session highlights the challenges that remain, including improvements needed in simulation accuracy and the versatility of the tools for various experimental scenarios.

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Radiative Corrections for polarized H(e,ep)

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  1. Radiative Corrections for polarized H(e,ep) Chris Crawford Mass. Inst. of Tech. Jan. 24, 2002

  2. Introduction Higher order diagrams Hard vs. Soft photons Approximations Radiative cross section Existing software SIMC (Hall C) MASCARAD Calculations Remaining work Outline

  3. Internal Processes Born Bremsstrahlung Vertex correction Vacuum polarization

  4. External Processes • Bremsstrahlung • Multiple scattering • Landau straggling • Energy loss • Simulate these with BLASTMC

  5. Soft Photons: within detector energy resolution E Multiple photon emission dominates at low Hard photons modify kinematics Hard v.s. Soft Photons

  6. 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

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

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

  9. 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

  10. MASCARAD • The asymmetry is insensitive to 

  11. Phase Space • Change of variables for

  12. Coincidence • Integrate over proton acceptance A • Sharply peaked in  and k

  13. Results from MASCARAD

  14. Results from MASCARAD

  15. Results from MASCARAD

  16. Results from MASCARAD

  17. Other Methods • Reconstruction in hadronic variables • Simplifies integration • C++ code PRC, by Feng Xiong • Based on POLRAD 2.0 • Others

  18. 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

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