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

1. 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 based on works in collaboration withB. Cox, A. De Roeck, A. Kaidalov, A. Martin, R. Orava, M. Ryskin and W.J. Stirling (New studies of the MSSM Higgs sector with G. Weiglein et al., in progress) FP-420

2. CMS & ATLASwere 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 • (luminositygoal ofδL ≤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 p p RG Is there a way out? ☺YES-> Forward Proton Tagging Rapidity Gaps  Hadron Free Zones matchingΔ Mx ~δM (Missing Mass) X RG p p

3. Forward Proton Taggersas a gluonicAladdin’s Lamp • (Old and NewPhysics menu) • Higgs Hunting(the LHC ‘core business’)K(KMR)S- 97-04 • Photon-Photon, Photon - HadronPhysics • ‘Threshold Scan’:‘Light’ SUSY …KMR-02 • Various aspects of DiffractivePhysics (soft & hard ). KMR-01 • (strong interest from cosmic rays people) • High intensityGluon Factory(underrated gluons)KMR-00, KMR-01 • QCD test reactions, dijet P-luminosity monitor • Luminometry KMOR-01 • Searches for new heavy gluophilic statesKMR-02, KMRS-04 • FPT • Would provide a unique additional tool to complement the conventionalstrategies at theLHCandILC. Higgs is only a part of the broad EW, BSM and diffractiveprogram@LHC • wealth of QCD studies, glue-glue collider, photon-hadron, photon-photon interactions… FPT  will open upan additional richphysics menu ILC@LHC

4. The basic ingredients of the KMR approach(1997-2005) Interplay between the soft and hard dynamics RGsignature for Higgs hunting(Dokshitzer, Khoze, Troyan, 1987). Developed and promoted by Bjorken (1992-93) • Bialas-Landshoff- 91rescattering/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> >>/\QCDin order to go by pQCD book - 4 (CDPE) ~ 10 *  (incl)

5. High price to pay for such a clean environment: σ (CEDP) ~ 10 -4 σ( inclus.) Rapidity Gapsshould survive hostilehadronicradiation damagesand ‘partonic pile-up ‘ W = S² T² Colour charges of the ‘digluon dipole’ are screened only at rd ≥ 1/ (Qt)ch GAP Keepers (Survival Factors) , protecting RG against: the debris of QCD radiation with 1/Qt≥ ≥ 1/M(T) soft rescattering effects (necessitated by unitariy) (S) How would you explain it to your (grand) children ? Forcing two (inflatable) camels to go through the eye of a needle H P P

6. Higgs boson LHC cost 2.5 billion REWARD

7. Current consensus on the LHC Higgs search prospects • SM Higgs : detection is in principle guaranteed for any mass. ☺ • In the MSSMh-boson most probably cannot escape detection, and in large areas of parameter space other Higgses can be found.☺ • But there are still troublesomeareas of the parameter space: • intense coupling regime of MSSM, MSSM with CP-violation….. • More surprises may arise in other SUSY • non-minimal extensions: NMSSM…… • After discovery stage(HiggsIdentification): • 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(G. Weiglein ‘s talk)

8. The advantages of CED Higgs production • Prospects for high accuracy mass measurements irrespectively of the decay mode. • (H-widthand evenmissing masslineshape in some BSM scenarios). • Valuable quantum number filter/analyzer. • ( 0++dominance ;C , P-even) • difficult or even impossible to explore thelight HiggsCPat theLHCconventionally. • (selection rule - an important ingredient of pQCD approach, • H ->bb ‘readily’ available • (gg)CED bbLO (NLO,NNLO) BG’s -> studied • SM HiggsS/B~3(1GeV/M) • complimentary information to the conventional studies. • For some (troublesome)areas of the MSSM parameter space may becomea discovery channel • H→WW*/WW - an added valueespecially 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……

9. ☻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 (KMRS- friendly so far).

10. Exclusive SM Higgs production b jets : MH = 120 GeV s = 2 fb (uncertainty factor ~2.5) MH = 140 GeV s = 0.7 fb MH = 120 GeV :10 signal / O(10) background in 30 fb-1 (with detector cuts) optimistically WW* : MH = 120 GeV s = 0.4 fb MH = 140 GeV s = 1 fb MH = 140 GeV :5-6 signal / O(3) background in 30 fb-1 H (with detector cuts) • The b jet channel is possible, with a good understanding of detectors and clever level 1 trigger ( μ-trigger from the central detector at L1 or/and RP(220) +jet condition) • TheWW channel is extremely promising : no trigger problems, better mass resolution at higher masses (even in leptonic / semi-leptonic channel), weaker dependence on jet finding algorithms • The  mode looks advantageous • If we see SM-like Higgs + p- tags the quantum numbers are 0++ H

11. suppressed enhanced The MSSM can be very proton tagging friendly The intense coupling regime is where the masses of the 3 neutral Higgs bosons are close to each other and tan  is large 0++ selection rule suppresses A production: CEDP ‘filters out’ pseudoscalar production, leaving pure H sample for study MA = 130 GeV, tan b = 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 thediscovery channel,and is certainly a powerful spin/parity filter

12. 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 • Very low rate of CED high-Et dijets, observed yield of Central Inelastic dijets. • (CDF: Run I, Run II) data up to (Et)min>50 GeV • ‘Factorization breaking’ between the effective diffractive structure functions measured at the Tevatron and HERA. • (KKMR-01 ,a quantitative description of the results, both in normalizationand the shapeof thedistribution) • 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 ofγγ • (in line with the KMRS calculations) BREAKING NEWS, CDF

13. CONCLUSION Forward Proton Taggingwouldsignificantlyextend the physics reachof the ATLASand 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 BSMscenarios theFPT may be the Higgs discoverychannel 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 theexperimentalists & engineers comeFORWARDand do theREAL WORK . The R&D studies must be completed within 12 months (only limited time-scale and manpower available)

14. FP420 (58 physicists from 29 institutes in 11 countries) Sub-detectors of either or both of ATLAS & CMS(common R&D route). The UK groups lead the studies. 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. 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 the interest in its exploring its feasibility. FP420 detector will replace the 420m interconnection cryostat First opportunity –autumn 2008(planned LHC shutdown)

15. FP-420 The LHC start-up is approaching