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LPC VBF Workshop

LPC VBF Workshop. Welcome and Introduction Dan Green Fermilab. Welcome. We are pleased to host a LHC Physics Center (LPC) Workshop – especially on VBF since the US physicists took large responsibility for the HF = tag jets

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LPC VBF Workshop

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  1. LPC VBF Workshop • Welcome • and • Introduction • Dan Green • Fermilab

  2. Welcome • We are pleased to host a LHC Physics Center (LPC) Workshop – especially on VBF since the US physicists took large responsibility for the HF = tag jets • If we find a “Higgs”, VBF will be an indispensible tool for exploring properties and isolating couplings. • There is an exciting program at this Workshop – and we hope you enjoy it.

  3. QED – “VBF” at a Few GeV Electron-positron annihilation into 1 photon “decaying “ into a lepton pair. Single s channel photon cross section falls with s. The 2 photon cross section has additional coupling constants but rises with s. At 100 GeV the cross section for dimuon production ( 90 pb) is comparable to the 2 photon production of ηc ( 33 pb). In general the 2 photon cross section exceeds the single photon at a few GeV

  4. Two Photon Physics • e are light so that WW radiative processes begin to dominate at a few GeV • Compare 1 photon production of mu pairs to 2 photon production of eta mesons: • Ratio is ~ 10% at 10 GeV CM energy, rising faster than linearly with s.

  5. EW – W Emission Weizacher-Williams approx – virtual W. Source function has coupling strength, EW, and a radiative 1/x behavior. Transverse virtual W dominate Luminosity of transverse W >> that for longitudinal W – but H couples preferentially to longitudinal W. Luminosity of WW in quark- antiquark pair, WW mass M

  6. WW in pp Luminosity of WW in pp system and cross section to produce X through VBF in pp reactions. VBF of H has a WW width which grows a cube of H mass – cancels the cross section falloff as M cubed. Falloff of H cross section via VBF with energy is slow. At high enough energy VBF is the dominant process.

  7. Numerical • For a mass of 0.5 TeV in 14 TeV pp collisions: • tau ~ 0.0013 • dl/dtau ~ 0.005 • pp cross section via VBF is ~ 1.3 pb. This is a substantial fraction of the total H production cross section.

  8. VBF at a Few TeV The e/p mass ratio is ~ 2000. Radiative processes begin to be important ( e.g. p radiation in the LHC must be carried by the beam pipe) at a few TeV.

  9. CALCHEP – VBF, H(180) Run CALCHEP for H(180) in pp 7+7 TeV. Tag jet separation in y is not all that large. – no cuts made on sample. Need to use all the topological characteristics of the VBF process.

  10. Tag Jets Tag jet Pt ~ MW/2. Tag jets are opposite in azimuth – assuming SM Higgs CP assignment. Mass of tag jet pair is fairly large. Perhaps use more sophisticated statistical methods – NN ?

  11. WW Scattering Use VBF to study WW scattering at all WW masses. If H mass is large, effectively study strong WW scattering as unitarity limit is approached – photon, H and Z - s channel and t channel and W quartic coupling. Can we use VBF to explore strong WW scattering?

  12. WW Scattering - H(200) Sharp t channel peak – photon, Z exchange. Cross section vs E is for H mass of 200 GeV. Large resonant WW peak unitarizes the weak cross section. In this case the resonance is the focus.

  13. WW – Heavy Higgs, H(2000) Set H mass = 2 TeV – WW cross section in SM decreases smoothly. Look for high mass deviations from SM is no Higgs found. Isolate WW -> WW using VBF?

  14. Other “VBF” Contributions ? Compared to VBF the simple vertex counting gives: The width are ~ For a light H the ratio of cross sections is of order 1, so there may be other terms in “VBF”. In fact, the strong production backgrounds make a “standard candle” for VBF using Z instead of H not possible – as far as I can tell

  15. Evolution of VBF Searches • More discriminating data driven ( e.g. jet veto uncertainties) methods are going to be used. • NN or the like will use the distinctive features of VBF to maximum advantage. • The CMS community for VBF is active and enthused • Good hunting!

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