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V.A. Khoze (IPPP, Durham)

Disclaimer : some of the results are (very) preliminary and should be taken only as a snapshot of the current understanding. Studies are still ongoing.

(in collaboration with S. Heinemeyer, M. Ryskin, W.J. Stirling, M. Tasevsky and G. Weiglein )

Main aims -to demonstrate that Double Proton Tagging @LHC is especially beneficial for the detailed studies of the MSSM Higgs bosons -to illustrate and to compare the salient features of the three main decay channels (bb, WW, ) for studies in the forward proton mode

- hunting the CP-odd Higgs in the diffractive environment

☻If the potential experimental challenges are resolved, then there is a very

real chance that for some areas of the MSSM parameter space the DPT could be the LHC Higgs discovery channel !

Diffractive processes at the LHC as a means to study SUSY Higgs sectorFP-420

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Main motivations

addressing the issues of :

current theoretical understanding of the MSSM Higgs sector, ( e.g. CHWW-05 )

impact on the CP-even SUSY Higgs searches in the DPT mode in various regions of the parameter space ( defining the ‘best case’ scenarios)

update of attempts to account for the real-life reduction factors for the observable signal (trigger, tagging efficiencies, angular cuts… ) help from Monika and Albert

(first studies DKMROR-02 , a lot of activity since then )

evaluation of the bb- backgrounds in the more realistic conditions (e.g., current understanding of the RP acceptances...).

hunting the CP-odd boson A in diffractive events.

(P. Bussey, Manch. wksp-05)

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The advantages of CED Higgs production

• Prospects for high accuracy mass measurements irrespectively of the decay mode. ( H-width and even missing mass lineshape in some BSM scenarios).

• Valuable quantum number filter/analyzer. ( 0++ dominance ;CP -even)

difficult or even impossible to explore the light Higgs CP at the LHC conventionally.

(selection rule - an important ingredient of pQCD approach,

• H bb opens up (Hbb Yukawa coupling)

(gg)CED bb LO (NLO,NNLO) BG’s -> studied

SM Higgs S/B~3(1GeV/M), M 3 complimentary information to the conventional studies.

☻ MSSM Higgs (with large tan) CED –friendly .

• H →WW*/WW - an added value - potential of an ‘ advantageous investment’ ● NMSSM (with J. Gunion et al. ) e. g., H4 (2- trigger)

• unique leverage –proton momentum (energy flows) correlations

(probes of QCD dynamics, pseudoscalar ID , CP- violation effects) KMR-02; J.Ellis et al -05

LHC : ‘after discovery stage’, Higgs ID……

to warm-up:

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☻Experimental Advantages

- Measure the Higgs mass via the missing mass technique

- Mass measurements do not involve Higgs decay products

- Cleanness of the events in the central detectors.

Experimental Challenges

– Tagging the leading protons– Selection of exclusive events & backgrounds– Triggering at L1 in the LHC experiments

Uncertainties in the theory

Unusually large higher-order effects, model dependence of

prediction (soft hadronic physics is involved after all)

There is still a lot to learn from present and future Tevatron diffractive data (KMRS- friendly so far). BREAKING NEWS, -CDF (Dec.2005)

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Theoretical InputRecall

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(h SM-like, H/A- degenerate.)

7(theoretical expectations –more on the conservative side)

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(KMR- based estimates)

(more on the pessimistic side, studies based on the CMS Higgs group procedure –still to come)

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(2 jet +L1 trigger condition)

-10% muon-rich final states (no RP condition)

, 300fb -1

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(600fb )-1

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Current Experimental Understanding and Assumptions

bb mode

Triggering on H (120 GeV) – currently a special challenge.. Necessitates L1 jet ET as low as 40 GeV . QCD background saturating the available output bandwidth.

●2j+ L1 trigger condition can be kept on acceptable level by requiring single-sided 220 m RP condition (up to L=2*10^33), Signal efficiencies ~10-15%.

●10% of the bb events can be retained by exploiting muon-rich final states (no RP requirements). At M=120 GeV an overall reduction factor (combined effect of trigger/tagging efficiencies, angular cut…) R(120 GeV)~13 (more on the optimistic side).

Assume R=13 at M<180 GeV.

At M180 GeV we may avoid the RP condition in the trigger, and the reduction factor can become R 5. Prospects to work at higher luminosities. believable (Albert, Peter)

Assume R=5 at M>180 GeV.

thanks to Monika, Albert , Michele & Peter

But mass resolution is muchpoorer when combining with 220m RP

the situation may be even better… though no detailed studies so far

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☻1/R should rise with increasing M, partially compensating decreasing

(CED).

(saturation probably somewhere around 200-250 GeV)

●increasing RP acceptance (e.g. factor of ~1.3 when going from 120 to 180)

● b-tagging efficiency, mass resolution improve for larger masses.

● trigger efficiency should increase for larger M,

Mass resolution is critical for the S/B for the SM 120 GeV Higgs. Less critical at larger masses.

Note, the existing estimates assume current hardware…

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mode

●A sub-sample of the general dijet sample. Assume reduction factor R= 13; situation may be (much) better, especially at larger M. ●Trigger thresholds are lower than for the general category.

● Might be possible to find the signatures allowing to avoid the RP condition. semileptonic decays, missing ET… …..event topology (Monika, Albert) No dedicated studies yet.

●Irreducible bkgds (QED) are small and controllable. QCD bkgd is small if g/- misidentification is <0.02 (currently ~0.007 for -jet efficiency 0.60)

Trigger cocktail - combined statistics (especially for searches and CP-ID purposes) bb and are taken on the L1 simultaneously

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WW mode (detailed studies in B. Cox et al. hep-ph/0505240)

No trigger problems for final states rich in higher pT leptons.Efficiencies ~20% (including Br) if standard leptonic (and dileptonic) trigger thresholds are applied.

Extra 10-15% from L1 jet +RP condition.Further improvements, e.g. dedicated -decay trigger.

Much less sensitive to the mass resolution.

Irreducible backgrounds are small and controllable.

Within 30fb^-1 of delivered lumi about 5 events of SM H(140 GeV); 1.5 events of H(120GeV).

Statistics may double if some realistic changes to leptonic triggerthresholds are made.

The h- rate can rise by about a factor of 3.5-4 in some MSSM

models (e.g., small eff scenario).

Pile-up is not such a severe problem as one might expect.

The centrally –tagged data may be analysed efficiently even at 10^34 lumi, using the timing technique. FP-420

(Monika)

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mhmax scenario, =200 GeV, MSUSY =1000 GeVhbb

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Hbb

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h

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H

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small eff scenario

for the SM Higgs at M = 120 GeV = 0.4 fb, at M= 140 GeV = 1 fb

mh 121-123 GeV

hWW

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Current understanding of the bb backgrounds for CED production

for reference purposes SM (120 GeV)Higgs in terms of S/B ratio (various uncrt. cancel) First detailed studies by De Roeck et al. (DKMRO-2002)

Preliminary results and guesstimates – work still in progress

S/B1 at ΔM 4 GeV

Four main sources (~1/4 each)

gluon-b misidentification (assumed 1% probability) Prospects to improve in the CEDP environment ? Better for larger M.

NLO 3-jet contribution Correlations, optimization -to be studied.

admixture of |Jz|=2 contribution

b-quark mass effects in dijet events Further studies of the higher-order QCD in progress

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The complete background calculations are still in progress (unusually large high-order QCD and b-quark mass effects).

Optimization, MC simulation- still to be done

Mass dependence of the SM(CEDP): SH~1/M³ Bkgd :ΔM/M for ,

ΔM/M for

( ΔM ,triggering, tagging etc improving with rising M)

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h bb, assume currently = S/S+B, mhmax scenario, =200 GeV (MS) MSSM

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Hbb

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h

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H

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Resume

● Hbb in the high mass range (MA180-250 GeV)

-unique signature for the MSSM, cross-sections overshoot the SM case by orders of magnitude.-possibility to measure the Hbb Yukawa coupling,-nicely complements the conventional Higgs searches - CP properties, separation of H from A, -unique mass resolution,-may open a possibility to probe the ‘wedge region’ !?-further improvements needed ( going to high lumi ?....) (more detailed theoretical studies required )

● h, Hbb, in the low mass range (MA < 180 GeV)

-coverage mainly in the large tan and low MA region, -further improvements (trigger efficiency….) needed in order to increase coverage

-

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● h,H in the low mass range (MA<180 GeV)-essentially bkgd –free production,-need further improvements, better understanding.., -possibility to combine with the bb-signal(trigger cocktail …)

-can we trigger on without the RP condition ?

● h WW -significant (~4) enhancement as compared to the SM casein some favourable regions of the MSSM parameter space.

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Hunting the CP-odd boson, A

(LO) selection rule – an attractive feature of the CEDP processes, but……

the flip side to this coin: strong ( factor of ~ 10² )suppression of the CED production of the A boson.

A way out : to allow incoming protons to dissociate (E-flow ET>10-20 GeV) KKMR-04

pp p + X +H/A +Y +p (CDD)

in LO azim. angular dependence: cos² (H), sin² (A), bkgd- flat

challenges: bb mode – bkgd conditions -mode- small (QED)bkgd, but low Br

A testing ground for CP-violation studies in the CDD processes (KMR-04)

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within the (MS) MSSM, e.g. mh scenarios with =±200 (500) GeV, tan=30-50

CDD(A->bb) ~ 1-3 fb, CDD(A->) ~ 0.1-03 fb CDD(H)~-CDD(A)

max

bb mode –challenging bkgd conditions (S/B ~1/50).

-mode- small (QED) bkgd, but low Br

situation looks borderline at best

‘best case’ (extreme) scenario

mh with =-700 GeV , tan =50, mg =10³GeV

max

CDD results at (RG) >3, ET>20 GeV

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A

in this extreme case : (Agg) Br(Abb) 22-24 MeV at MA=160-200 GeV ,tan 50,

CDD (A bb) is decreasing from 65fb to 25fb (no angular

cuts)

CDD (A) 0.8-0.3 fb

S/B ~ (A->gg) Br (A->bb) / MCD

5.5 /MCD (GeV)

currently MCD ~ 20-30 GeV…(12GeV at 120 GeV)

Prospects of A- searches strongly depend, in particular, on the possible progress with improving MCD in the Rap. Gap environment

There is no easy solution here, we must work hard in order to find way out .

We have to watch closely the Tevatron exclusion zones

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Proton Dissociative Production (experimental issues)

thanks to Monika, Michele & Albert

Measurement of the proton diss. system with ET of 20 GeV and 3<<5 -probably OK for studying the azimuthal distributions (HF or FCAL calorimeters)

Trigger is no problem if there is no pile up (Rap Gaps at Level 1); 4jet at 2*10³³ lumi- borderline

Maybe we can think about adding RPs into the trigger ( no studies so far) Maybe neutrons triggered with the ZDC (Michele )?

Can we discriminate between the cos² and sin² experimentally ?

From both the theoretical and experimental perspectives

the situation with searches for the A in diffractive processes looks

at best borderline, but the full simulation should be performed before arriving at a definite conclusion.

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Known Unknowns or Unknown Unknowns ? (challenges, questions, miscommunication, misinterpretation, mis…… )

Triggering on the bb- channel without RP condition at M 180 GeV ? Electrons in the bb –trigger ?Triggering on the - channel without RP condition at lower M values ?

Mass dependence of the signal reduction factor for the bb-channel ?

Trigger cocktail for the searches + CP ID purposes.

Experimental perspectives for the CP-odd Higgs studies in the p-dissociation modes ?

Mass window MCD from the Central Detector only (bb, modes) in the Rap Gap environment?Can we do better than MCD ~20-30 GeV? Mass dependence of MCD ?

How to trigger on events with both protons in the 420m RP ? Increase in L1 trigger latency (SLHC) ? Special running modes ?....

Going to higher luminosities (up to 10^34) ? Pile-up…. ?

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CONCLUSION

Forward Proton Tagging would significantly extend the Higgs study reach

of the ATLAS and CMS detectors. FPT has a potential to perform measurements

which are unique at LHC and complementary to ILC.

For certain BSM scenarios the FPT may be the

Higgs discovery channel. (even with the current hardware)

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FP-420

The LHC start-up is approaching

Nothing would happen before the experimentalists and engineers come FORWARD and do the REAL WORK

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