Diffractive Higgs Production. Overview Calculating cross-sections SM Higgs SUSY Higgs Tevatron data. Jeff Forshaw Manchester Meeting Dec 2005. Diffractive Higgs production (exclusive case). Detect the four-momenta of the protons using detectors situated 420m from the interaction point.
Manchester Meeting Dec 2005
Detect the four-momenta of the protons using detectors situated 420m from the interaction point
Woefully short on references: see my review on hep-ph/0508274
i.e. colliding gluons must have equal helicity
Start by computing the quark level amplitude…..
becomes…(after integrating over the proton transverse momenta)
Since the suppression factor vanishes faster than any power of the integral is rendered finite.
The probability of emitting a gluon off a fusing gluon is logarithmically enhanced:
Summing the large logarithms to all orders gives an exponential for the probability NOT to emit:
We must include this non-emission probability in the amplitude:
It is crucial to sum to LLA accuracy…
It’s ok to use perturbation theory… right…..
Not much sensitivity to the ambiguity relating to the right…..infra-red behaviour of the gluon distribution functions:
Extrapolation into this regionbut cross-section not sensitive to it.
Assume that there is a single mechanism which fillsgaps (“an inelastic scatter”) and assume that it isindependent of anything else in the event.
Same b as before: partial cancellation of uncertainty in totalrate.
Combined with the optical theorem this implies that
Hence one can fit the eikonal factor using data.
This model is the basis behind the underlying event generation in PYTHIA andalso the “JIMMY” underlying event model in HERWIG. Both have been testedsuccessfully against data (from HERA and Tevatron). [Sjostrand & Skands;Borozan & Seymour; Odagiri; Butterworth; Field.]
More sophisticated eikonal models: Kaidalov, Khoze, Martin, Ryskin; Gotsman, Levin, Maor et al.
Hybrids: Bzdak; Petrov &Ryutin.
But it does not contain Sudakov suppression
Would be flat if right…..
Full Monte Carlostudy neededusing ExHuME and POMWIGStandard Model Higgs
b quark decay channel
Easy to trigger (require at least one W to decay leptonically)
Small numbers of events but backgrounds under control leptonically)
Don’t need many events to measure the mass and establishcleanly that Higgs is a scalar particle.
Full Monte Carlo of the gg initiated backgrounds to be done, leptonically) first calculations indicate S/B > 1 without anything fancy…
Boos, Djouadi, Muhlleitner, Vologdin, Nikitenko
Very large cross-sections leptonically) and can detect in theb-quark decay channel
Kaidalov, Khoze, Martin, Ryskin
J-S.Lee, Pilaftsis, J. Ellis,Carena, Wagner, Mrenna,Choi, Hagiwara, Drees
J. Ellis, J-S. Lee, A. Pilaftsis leptonically)
Note that cross-sectionsare much bigger than
Cox, JF, J-S. Lee, Monk, Pilaftsis leptonically)
Durham Group analysis of backgrounds:all cross-sections in fb
Analysis of background rates reveals that taudecay channel is a possibility.
Also the possibility of using the azimuthaldependence of the tagged protons to form a CP asymmetry:
Total Higgs production cross-section at
LHC (solid) and Tevatron (broken).
Central dijet production can be used totest the theory:
CDF lower bound on exclusive dijets:
Durham group predicts 40 pb.
Preliminary result leptonically)
[Uncorrected CDF data]
Cox & Pilkington
A “standard candle” at the Tevatron leptonically)
Analysis underway on CDF
CDF has observed a dozen central J/ψ events at a rateconsistent with predictions. But not really perturbative.
Khoze, Martin, Ryskin, Stirling