1. Central Exclusive Production of BSM Higgs bosons decaying to jets
Andrew Pilkington
The University of Manchester
Presented at Forward Physics at the LHC, Manchester, 6th December 2008
Overview
Higgs bosons in a triplet model
Trigger strategies for jets
Combinatorial background rejection
Results

2. Central Exclusive Production
Defined as the process pp p +  + p.
Protons remain intact, scatter through small angles.
All of momentum lost by protons goes into the production of the central system, .
 obeys a Jz=0, C-even, P-even selection rule
Direct quantum number measurement of resonance to be JPC=0++.
Di-quark production suppressed by mq2/ M2
FP420 + detectors at 200m from IP used to tag outgoing protons.

3. Higgs bosons in a triplet model
Extend SM by addition of higher representations of Higgs sector in addition to the doublet.
One real and one complex triplet chosen ala Georgi and Machacek.
4 neutral scalar Higgs’ bosons, charged and doubly charged Higgs also.
Enhancement of Higgs-fermion-antifermion coupling by 1/cH2 where cH is a doublet-triplet mixing parameter.
Large enhancement in CEP production cross section for cH < 1 (top-loop).
LEP constraints on Higgs mass weaker as coupling to weak bosons reduced by cH2.
Tevatron will be able to access cH=0.2 in tau-tau decay channel in near future.

4. CEP Triplet Higgs (II) Forward detector information
Chaichian, Huitu, Khoze, A.P.
in preparation.
Forward detector information
Level 1 (L1): Information from detectors at 220m from IP is available.
Level 2 (L2): Full forward proton tagging information available.
Jet L1 triggers for CEP
Use final state muon if final state has b-jets. (10% efficient for triplet signal if muon pT>6GeV).
1 jet (ET>40GeV) and 1 proton tagged at 220m. Rate<1kHz up to L~2x1033cm-2s-1. Could allow fixed rate trigger of 5 kHz or 10 kHz up to higher luminosities.
2 jets at L1 with high rate. Reduced at L2 by full proton tagging information. Rejection ~20000 (140) for L=1033 (1034) cm-2s-1.

5. Overlap backgrounds
Dijet cross sections, ET > 40 GeV
10ps timing resolution
At high luminosity, many proton-proton interactions in the same bunch crossing.
Can have, one di-jet event plus two events that produce forward protons, [p][X][p].
TOF gives us an estimate of the primary vertex location - z=c(t2-t1)/2
10ps timing resolution is equivalent to a vertex measurement accurate to 2.1mm

6. Kinematic matching
Compare mass and rapidity, measured by forward detectors, to mass and rapidity measured in central detector.
For jets:
Measurement of mass from leading jet (ET,).
Measurement of rapidity from jet directions

7. Charged Tracking Variables: Jets
Tagged protons imply no multiple parton-parton interactions in CEP/DPE events.
However, [p][X][p] events have a pp→X interaction as the primary vertex.
Increased track multiplicity at main vertex.
Di-jet events
Construct back-to-back jets:
Require few tracks in the transverse region (perpendicular to jets).
Can also look for total number of tracks outside of jet cones.

8. Results: Triplet Higgs production
mH=120 GeV
cH=0.2
mH=150 GeV
cH=0.2
mH=120 GeV
cH=0.5
mH=150 GeV
cH=0.5

9. Summary Forward proton tagging at ATLAS
1) CEP plus forward proton tagging offers both discovery and precision physics.
2) Experimentally the process should be well defined by ‘exclusivity’ requirements.
Triplet Higgs production - Precision physics
1) Mass measurement to an accuracy of approximately 1GeV.
2) Determination of quantum numbers of observed resonance.