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POMWIG: Advanced Diffractive Interactions in HERWIG Framework

POMWIG is a modified version of HERWIG specifically designed for diffractive collisions, utilizing measured structure functions and offering hard matrix elements for IP, IR, and electron interactions. With minimal changes to HERWIG, POMWIG provides routines for photon flux, structure functions, pomeron structure, and more. It allows for running exclusive processes like Double Diffractive Dijets and Higgs Production, offering insights into potential Higgs discovery channels. The tool accurately reproduces differential distributions at HERA and the Tevatron, making it valuable for detector corrections and research. Consider utilizing POMWIG for studying exclusive contributions in double diffractive processes and exploring new physics scenarios.

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POMWIG: Advanced Diffractive Interactions in HERWIG Framework

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  1. POMWIG – Herwig for Diffractive interactions Brian Cox and Jeff Forshaw Comput.Phys.Commun.144:104-110,2002 (hep-ph/0010303) http://www.pomwig.com • Simple modification to HERWIG (doesn’t affect functionality at Tevatron) which makes all HERWIG features available in diffractive collisions • IP P, IR P, IP IP ,IR IR, e IP, e IR collisions with all HERWIG hard matrix elements

  2. WHAT IS POMWIG ? • No doubt that Ingelman – Schlein (Regge factorisation) works at HERA • Pomwig uses measured structure functions and flux from H1 OR user defined structure functions / flux

  3. QCD Hard scattering factorisation : conditional proton parton densities for particular xIP, t Regge factorisation :

  4. Modifications to Herwig • Philosophy : make as few changes as possible, do not change common blocks • MODIFIED ROUTINES : • HWEGAM : photon flux routine • HWSFUN : structure functions • NEW ROUTINES • H1QCD : H1 pomeron structure • FLUX : pomeron and reggeon fluxes • POMSTR : user defined structure functions

  5. How to run POMWIG • Select electron for beam particle to emit pomeorn / reggeon • Q2WWMN  TMIN, Q2WWMX  TMAX • YWWMIN  XpomMIN, YWWMAX  XpomMAX • NSTRU=6 (H1 pomeron), 7 (Reggeon), 8 (user defined)

  6. Double Diffractive Dijets and Higgs Production POMWIG : “Central-inelastic” process p+p p + gap + H + X + gap + p • Is this really a contender for a light Higgs discovery channel ? • We won’t see DD Higgs at Tevatron, BUT we do see DD dijets • Question : Can we see the exclusive contributions in the DD dijets ? • Answer: Not yet, but we should (if it exists) in RunII. “exclusive” Khoze, Martin & Ryskin, hep-ph/0207313, Eur.Phys.J. C23 (2002) 311-327Cox, Forshaw & Heinemann, Phys.Lett.B540:263-268,2002 De Rouke, Khoze, Martin, Orava & Ryskin hep-ph/0207042 Albrow and Rostovtsev, hep-ph/0009336 …

  7. Double Diffractive Higgs in POMWIG

  8. IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS 1 E+ -11101 0 0 4 5 0.00 0.00 980.0 980.0 0.00 2 E- 11 102 0 0 6 7 0.00 0.00 -980.0 980.0 0.00 3 CMF 0 103 4 6 0 0 0.01 -1.05 -31.1 163.0 160.02 4 GAMMA 22 3 1 0 0 0 0.07 -0.81 65.9 65.9 -0.84 5 E+ -11 1 1 0 0 0 -0.07 0.81 914.1 914.1 0.00 6 GAMMA 22 3 2 0 0 0 -0.06 -0.24 -97.1 97.1 -0.27 7 E- 11 1 2 0 0 0 0.06 0.24 -882.9 882.9 0.00 ---HARD SUBPROCESS--- IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS 8 GLUON 21 121 10 9 11 9 0.05 -0.62 50.8 50.9 0.75 9 GLUON 21 122 10 8 15 8 -0.04 -0.16 -65.0 65.0 0.75 10 HIGGS 25 120 8 9 67 67 14.85 -6.11 -14.4 117.0 115.01 ---H/W/Z BOSON DECAYS--- IHEP ID IDPDG IST MO1 MO2 DA1 DA2 P-X P-Y P-Z ENERGY MASS 79 BQRK 5 123 67 80 81 80 25.96 -26.45 -57.1 68.2 4.95 80 BBAR -5 124 67 79 86 79 -11.11 20.34 42.6 48.8 4.95 Double Diffractive Higgs

  9. Double Diffractive Dijets Appleby & Forshaw, Phys.Lett.B451:108-114,2002 CDF Phys. Rev. Lett 85 4215 (2000)

  10. Gap Survival (factorisation breakdown) • Its possible that the gap destruction mechanism is largely independent of the diffractive sub process • Means that POMWIG gets the differential distributions correct at the Tevatron , up to a (process independent) normalisation factor

  11. KEY POINTS • POMWIG makes state of the art matrix elements available in diffraction (if you keep HERWIG up to date) . • POMWIG is a simple modification to HERWIG which does not affect normal operation at Tevatron (only photoproduction routines changed). • As far as we can tell at present, all differential distributions in diffractive processes at HERA and Tevatron are correctly reproduced, with a universal overall normalisation factor of about 0.1 applied to account for gap survival. • This means that it doesn’t matter whether or not you like Regge factorisation - POMWIG is a useful tool for detector corrections etc. • Double diffractive dijets are one of the most interesting processes to measure at RunII, if only because double diffractive Higgs at the LHC may turn out to be a competitive discovery channel for light Higgs.

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