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Forward Proton Tagging at the LHC as a Means to Search for New Physics

V.A. Khoze (IPPP, Durham)

main aims to illustrate the theoretical motivations behind the recent proposals to add the Forward Proton Taggers to the LHC experiments.

to show that the Central Exclusive Diffractive Processes may provide an exceptionally clean environment to search for and to identify the nature of new objects at the LHC

FP-420

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CMS & ATLAS were designed and optimised to look beyond the SM

High -pt signatures in the central region

But… incomplete

• Main physics ‘goes Forward’

•Difficult background conditions.

• The precision measurements are limited by systematics (luminosity goal of δL ≤5%)

Lack of :

•Threshold scanning , resolution of nearly degenerate states (e.g. MSSM Higgs sector)•Quantum number analysing

ILC chartered territory•Handle on CP-violating effects in the Higgs sector•Photon – photon reactions

Is there a way out?

☺ YES-> Forward Proton Tagging

Rapidity Gaps Hadron Free Zones

matching Δ Mx ~ δM (Missing Mass)

RG

RG

X

p

p p

p

talk by A. De Roeck

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Forward Proton Taggers as a gluonic Aladdin’s Lamp (Old and New Physics menu)

•Higgs Hunting (the LHC ‘core business’) K(KMR)S- 97-04

•Photon-Photon, Photon - Hadron Physics

• ‘Threshold Scan’: ‘Light’ SUSY … KMR-02 • Various aspects of Diffractive Physics (soft & hard ). KMR-01

(strong interest from cosmic rays people ) High intensity Gluon Factory (underrated gluons) KMR-00, KMR-01 QCD test reactions, dijet P-luminosity monitor

•Luminometry KMOR-01

•Searches for new heavy gluophilic states KMR-02, KMRS-04

FPTWould provide a unique additional tool to complement the conventional strategies at the LHC and ILC.

Higgs is only a part of the broad EW, BSM and diffractive program@LHC (A.De Roeck) wealth of QCD studies, glue-glue collider, photon-hadron, photon-photon interactions…

FPT will open up an additional rich physics menu ILC@LHC

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The basic ingredients of the KMR

approach (1997-2005)

Interplay between the soft and hard dynamics

Bialas-Landshoff- 91 rescattering/absorptive ( Born -level ) effects

Main requirements:•inelastically scattered protons remain intact

•active gluons do not radiate in the course of evolution up to the scale M

•<Qt> >>/\QCD in order to go by pQCD book(CDPE) ~ 10 * (incl)

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RG signature for Higgs hunting (Dokshitzer, Khoze, Troyan, 1987). Developed and promoted by Bjorken (1992-93)

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Higgs boson

REWARD 2.5 billion

LHC cost

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Current consensus on the LHC Higgs search prospects

•SM Higgs : detection is in principle guaranteed for any mass. ☺

•In the MSSM h-boson most probably cannot escape detection, and in

large areas of parameter space other Higgses can be found. ☺

•But there are still troublesome areas of the parameter space: intense coupling regime of MSSM, MSSM with CP-violation…..

•More surprises may arise in other SUSYnon-minimal extensions: NMSSM……

• After discovery stage (Higgs Identification):

The ambitious program of precise measurements of the Higgs mass, width, couplings, and, especially of the quantum numbers and CP properties would require an interplay with a ILC

What about the H- quantum numbers and the Hbb coupling ?

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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 ;C , P-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 ‘readily’ available

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

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

• For some (troublesome) areas of the MSSM parameter space may become a discovery channel

• H →WW*/WW - an added value especially for SM Higgs with M≥ 135GeV,

- ‘an advantageous investment’

New run of the MSSM studies is underway (with G. Weiglein et al)

• New leverage –proton momentum correlations

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

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

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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.– bb-mode requires special attention.

Uncertainties in the theory

(Unusually) large higher-order effects, model dependence of

predictions (soft hadronic physics is involved after all)

There is still a lot to learn from present and future Tevatron diffractive data (KKMRS- friendly so far).

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The intense coupling regime is where the masses of the 3 neutral Higgs bosons are

close to each other and tan is large suppressed

enhanced

0++ selection rule suppresses A production:

CEDP ‘filters out’ pseudoscalar production, leaving pure H sample for studyMA = 130 GeV, tan = 50

Mh = 124 GeV :70 signal / (3-10) background in 30 fb-1

MH = 135 GeV : 125 signal / (2-5) background in 30 fb-1

MA = 130 GeV : 3 signal / (2-5) background in 30 fb-1

Well known difficult region for conventional channels, tagged proton channel may well be the discovery channel , and is certainly a powerful spin/parity filter

The MSSM can be very proton tagging friendly

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● 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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Ongoing studies (together with S. Heinemeyer, M.Ryskin, W..J. Stirling, M.Tasevsky and G. Weiglein)

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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.

● small and controllable backgrounds

● Hunting the CP-odd boson, A

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

pp p + X +A +Y +p

At the moment the situation looks borderline

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MSSM

V.A.Khoze, S.Heinemeyer, W.J.Stirling, M.Ryskin M. Tesevsky and G. Weiglein in progress

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EXPERIMENTAL CHECKS

Up to now the diffractive production data are consistent with K(KMR)S results Still more work to be done to constrain the uncertainties

• Rate of CED high-Et dijets, observed yield of Central Inelastic dijets. (CDF: Run I, Run II) data up to (Et)min>50 GeV, ( K.Terashi’s talk)

• ‘Factorization breaking’ between the effective diffractive structure functions measured at the Tevatron and HERA.

(KKMR-01 ,a quantitative description of the results, both in normalization and the shape of the distribution)

•The ratio of high Et dijets in production with one and two rapidity gaps

• Preliminary CDF results on exclusive charmonium CEDP. Higher statistics is underway.

•Energy dependence of the RG survival (D0, CDF)

• CDP of γγ

(in line with the KMRS calculations)

BREAKING NEWS, CDF

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CONCLUSION

Forward Proton Tagging would significantly extend the physics reach of the ATLAS and CMS detectors by giving access to a wide

range of exciting new physics channels. FPT has the potential to make measurements which are unique at

LHC and challenging even at a ILC.

For certain BSM scenarios the FPT may be the Higgs discovery channel within the first three years of low luminosity running

FPT offers a sensitive probe of the CP structure of the Higgs sector.

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

The R&D studies must be completed within 12 months (only limited time-scale and manpower available)

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FP-420

The LHC start-up is approaching

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From the LHCC minutes (November 2005)

The LHCC heard a report from the FP420 referee. In its Letter of Intent,the FP420 Collaboration puts forward an R&D proposal to investigate the feasibility of installing proton tagging detectors in the 420 m. region at the LHC. By tagging both outgoing protons at 420 m. a varied QCD,electroweak, Higgs and Beyond the Standard Model physics programme becomes accessible. A prerequisite for the FP420 project is to assess the feasibility of replacing the 420 m. interconnection cryostat to facilitate access to the beam pipes and therefore allow proton tagging detectors to be installed. The LHCC acknowledges the scientific merit of the FP420 physics program and theinterest in its exploring its feasibility.

LOI-submitted to the LHCC: CERN-LHCC-2005-025 LHCC-I-015

FP420 : An R&D Proposal to Investigate the Feasibility of Installing Proton Tagging Detectors in the 420m Region at LHC.

FP420 (58 physicists from 29 institutes in 11 countries)

Sub-detectors of either or both of ATLAS & CMS (common R&D route).

First opportunity –autumn 2008 (planned LHC shutdown)

FP420 detector will replace the 420m interconnection cryostat