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Brian Cox and Jeff Forshaw Comput.Phys.Commun.144:104-110,2002 (hep-ph/0010303) pomwig

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

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Brian Cox and Jeff Forshaw Comput.Phys.Commun.144:104-110,2002 (hep-ph/0010303) pomwig

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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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