Double proton tagging at the LHC UK HEP Forum, Coseners house 25th April 2004 Brian Cox Improved mass resolution Only 0 ++ (or 2 ++ ) systems produced bb background strongly suppressed Very schematically its a glue – glue collider where you know the beam energy of the gluons - so any 0 ++ state which couples strongly to glue is a possibility … Forward physics with proton taggers at the Tevatron and LHC Dec 2004 glodwick.hep.man.ac.uk/conference s >> M 2,t, (a) & (b) cancel in limit m b -> 0

The Experimental Challenges M 2 = S Where are the fractional momentum losses of the outgoing protons horizontal offset = D x To get ~ proton (M ~ 70 GeV) 2.5mm from beam (10 ) pots must be > 250 m from IP -> cold region, & level 1 trigger not possible K. Österberg 420 m308 m215 m

The Standard model Higgs Alan Martin

Particularly promising scenarios for CEDP If the coupling of the Higgs-like object to gluons is large, double proton tagging becomes very attractive Difficult regions of the MSSM The MSSM with explicit CP violation (CPX)

An example : The intense coupling regime of the MSSM 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 Kaidalov, Khoze, Martin, Ryskin hep-ph/ selection rule suppresses A production: CEDP filters out pseudoscalar production, leaving pure H sample for study For 5 with 300 (30) fb -1 e.g. m A = 130 GeV, tan = 50 (difficult for conventional detection, but exclusive diffractive favourable) L = 30 fb -1, M = 1 GeV S B m h = GeV 71 3 events m H = GeV m A = 130 GeV 1 2 Alan Martin Manchester Dec 2003

The MSSM with explicit CP violation - the CPX scenario M. Carena, J. Ellis, S. Mrenna, A. Pilaftsis and C. E. M. Wagner, Nucl. Phys B659 (2003) 145 there are small regions of parameter space in which none of the neutral Higgs bosons can be detected at the Tevatron and the LHC Medium grey Dark grey In the CPX scenario, the three neutral MSSM Higgs bosons, (CP even) h 0 and H 0, and (CP odd) a mix to produce 3 physical mass eigenstates H 1, H 2 and H 3 with mixed CP Imagine a light scalar which couples predominantly to glue, and decays to b jets … would we see it at LEP, Tevatron or LHC?

B.C., Forshaw, Lee, Monk and Pilaftsis Phys. Rev D68 (2003) Khoze, Martin and Ryskin hep-ph/ CPX MSSM Higgs QCD Background ~ 0 ++ Selection ruleAlso, since resolution of taggers > Higgs width: But mode has only QED background in fb CP even CP odd active at non-zero t Direct evidence for CP violation in Higgs sector

The Tevatron will provide valuable information Appleby and Forshaw Phys.Lett.B541: ,2002 CDF Phys. Rev. Lett. 85, 4215 (2000) Pomerons remnants Central exclusive - no remnants The exclusive cross section ~ factorises … Hard subprocess cross section Effective luminosity for production of mass M at rapidity y … so can be checked by measuring higher rate processes at Tevatron and LHC -> See Angela Wyatts talk D S Q2Q2 Q3Q3 Q4Q4 S A1A1 A2A2 P 1U P 2I P 2O P 1D D2 D Veto Q4Q4 Q3Q3 Q2Q2

Summary and work in progress Real discovery potential in certain scenarios Possibility to measure Higgs branching ratio to e.g. b or - complementary information to conventional searches Azimuthal asymmetries allow direct measurement of CP violation in Higgs sector Assuming CP conservation, any object seen with 2 tagged protons has positive C parity, is (most probably) 0 +, and is a colour singlet Need independent theoretical and experimental verification of the cross section and background predictions (Manchester and Durham collaborating) Need more work on level 1 trigger - can we do it? (see e.g Monika Grothe at LHC / HERA workshop) Need independent detailed studies of mass resolution and acceptance of pots Need a well presented physics case and must prove the experimental needs lead to minimal disruption to current LHC program