1. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 1 Diffractive Higgs searches: The Pomeron as little helper in tracking down the Higgs ? - The FP420 project Monika Grothe U Turin/ U Wisconsin Johns-Hopkins workshop Heidelberg August 2007 Why ? How in principle ? What’s available already ? Specific challenges ? Current status ?

2. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 2 Why bother with diffraction at the LHC ?

3. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 3 Suppose you want to detect a light SM Higgs (say M H =120 GeV) at the LHC... SM Higgs with ~120 GeV: gg  H, H  b bbar highest BR But signal swamped by gg  jet jet Best bet with CMS: H   Vacuum quantum numbers “Double Pomeron exchange” shields color charge of other two gluons Central exclusive production pp  pXp Suppression of gg  jet jet because of selection rules forcing central system to be (to good approx) J PC = 0 ++

4. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 4 Diffraction as tool for discovery physics: Central exclusive production pp  pXp Experimental assets of central exclusive production:  Selection rules: central system is J PC = 0 ++ (to good approx) I.e. a particle produced with proton tags has known quantum #  Excellent mass resolution achievable from protons, independent of decay products of X in central detector: “CEP as superior lineshape analyser”  CP quantum numbers and CP violation in Higgs sector directly measurable from azimuthal asymmetry of the protons: “CEP as spin-parity analyzer”  Proton tagging improves S/B for SM Higgs dramatically Case in point: pp  pHp with H(120 GeV)  b bbar In non-diffractive production hopeless, signal swamped by QCD di-jet background  CEP may be discovery channel in certain regions in MSSM where the Xsection can be much larger than in SM

5. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 5 H b jets : M H = 120 GeV;  = 2 fb (uncertainty factor ~ 2.5) M H = 140 GeV;  = 0.7 fb M H = 120 GeV : 11 signal / O(10) background in 30 fb -1 with detector cuts WW * : M H = 120 GeV;  = 0.4 fb M H = 140 GeV;  = 1 fb M H = 140 GeV : 8 signal / O(3) background in 30 fb -1 with detector cuts Standard Model Higgs Generator studies with detector cuts Central exclusive production: Standard Model light Higgs Note: This H decay channel is impossible in non-CEP production ! Note: Use semi-leptonic decays for measurement

6. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 6 Search for exclusive  3 candidate events found 1 (+2/-1) predicted from ExHuME MC* Same type of diagrams as for Higgs  validation of KMR model ! hep-ex/0707237 Central exclusive production: Observation at Fermilab

7. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 7 How go about measuring central exclusive production ?

8. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 8 Measuring central exclusive production: Experimental signature

9. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 9 Measuring central exclusive production: Principle of measurement beam p’ roman pots dipole Needed: Proton spectrometer using the LHC beam magnets Detect protons that are very slightly off-momentum wrt beam protons, i.e. detection needed inside of beam pipe Diffractively scattered protons survive interaction intact and lose only a small fraction of their initial momentum in the process

10. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 10 Measuring central exclusive production: Where to put the detectors  =0 (beam)  =0.002  =0.015  1  2 s = M 2 With √s=14TeV, M=120GeV on average:   0.009  1% With nominal LHC optics:  fractional momentum loss of the proton beam p’ roman pots dipole

11. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 11 Nominal LHC beam optics Low  * (0.5m): Lumi 10 33 -10 34 cm -2 s -1 @220m: 0.02 <  < 0.2 @420m: 0.002 <  < 0.02  1  2 s = M 2 With √s=14TeV, M=120GeV on average:   0.009  1% Detectors at 420m complement acceptance of 220m detectors needed to extend acceptance down to low  values, i.e. low MHiggs Detectors closer to IP, e.g. ~220m optimize acceptance (tails of  distr.) can be used in L1 trigger, while 420m too far away for detector signals to reach L1 trigger within latency Measuring central exclusive production: Where to put the detectors (II)

12. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 12 Current experimental situation at the ATLAS and CMS IP’s: ALFA and TOTEM Possible extension of the ATLAS/CMS baseline detectors : FP420

13. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 13 TOTEM x L =P’/P beam =  det @420 d  (ep  eXp)/dx L [nb] Existing proton tagging detectors CMS IP: TOTEM  Approved experiment for  tot,  elastic meas.  Uses same IP as CMS  Roman-pot housed Silicon tracking detectors at 180m and 220m from IP  TOTEM’s trigger/DAQ system will be integrated with those of CMS, i.e. common data taking CMS + TOTEM possible  However, operation at highest LHC lumi would require rad hard upgrade of Totem Si ATLAS IP: ALFA  Detectors to determine absolute luminosity by way of measuring elastic scattering in Coulomb interference region  Approved part of ATLAS experiment  Roman-pot housed scintillating fiber detectors at 240m from IP  Operation at nominal LHC lumi requires rad-hard upgrade - option subject of an R&D effort by several ATLAS groups data points from ZEUS

14. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 14 The FP420 R&D project Proposal to the LHCC in June 2005: CERN-LHCC-2005-025 “FP420: An R&D Proposal to Investigate the Feasibility of Installing Proton Tagging Detectors in the 220m Region at LHC” Signed by 29 institutes from 11 countries The aim of FP420 is to install high precision silicon tracking and fast timing detectors close to the beams at 420m from ATLAS and / or CMS “The LHCC acknowledges the scientific merit of the FP420 physics program and the interest in its exploring its feasibility.” - LHCC

15. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 15 FP420 project: How to integrate detectors into the cold section of the LHC Turin / Cockcroft Institute / CERN 420m from the IP is in the cold section of the LHC Modify LHC Arc Termination Modules for cold-to-warm transition such that detectors can be operated at ~ room temperature scattered protons emerge here

16. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 16 FP420: How to move detectors close to the beam Turin / Louvain / Helsinki Movable beam-pipe with detector stations attached Move detectors toward beam envelope once beam is stable Gastof or Quartic Silicon detector box Beam position monitor

17. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 17 FP420: Which technology for the detectors 3D edgeless Silicon detectors:  Edgeless, i.e. distance to beam envelope can be minimized  Radiation hard, can withstand 5 years at 10 35 cm -2 s -1  Use ATLAS pixel chip (rad hard) for readout Active edges: the edge is itself an electrode, so dead volume at the edge < 5 . Electrodes are processed inside the detector bulk instead of being implanted on the wafer’s surface. Manchester / Stanford  Prototype in CERN testbeams 2006 and 2007  Technology is candidate for ATLAS tracker SLHC upgrade

18. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 18 FP420 project: Silicon Detector Stations Manchester / Mullard Space Science Lab 7.2 mm x 24mm 3 detector stations with 8 layers each 8 mm

19. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 19 FP420 project: Fast timing detectors Protons PMT Lens? (focusing) Mirror Cerenkov medium (ethane) ~ 15 cm ~ 5 cm (Flat or Spherical?) Aluminium pump Injection of gas (~ atmospheric pressure) Ejection of gas ~ 10 cm GASTOF (UC Louvain) Cherenkov medium is a gas Micro channel plate photo-multiplier tubes (MCP-PMT) were successfully employed in building Cherenkov-light based TOF detector with resolution of ~10ps (NIM A 528(2004) 763) Would translate in z-vertex resolution of better than 3mm  Needed to veto protons from pile-up events Two technologies; both in FERMILAB test beams 2006 and 2007 QUARTIC (U Texas-Arlington): Cherenkov medium is fused Silica proton Cherenkov light

20. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 20 Benoît Florins, Krzysztof Piotrzkowski, Guido Ryckewaert ATM Vacuum Space BPM Pockets ATM Line X Bus Bar Cryostat BPM Vacuum Space Transport side QRL Fixed Beampipe FP420 project: Putting it all together

21. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 21 FP420: What resolution does one achieve ? Si pitch 40-50  m x and y orientation  (x) ~  (y) ~15  m Glasgow / Manchester S/B for 120GeV Higgs  b bbar depends critically on mass window width around signal peak CMS IP ATLAS IP CEP of Higgs:

22. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 22 Central problems to solve in the analysis of diffractive events at the LHC

23. Experimental challenge: Trigger The difficulty of triggering on a 120GeV Higgs Note: 220m proton taggers usable in L1 trigger, 420m taggers only on HLT because 420m too far away from IP for signal to arrive within L1 latency of 3.2  s Trigger at ATLAS/CMS based on high p T /E T jet and lepton candidates in event In order to keep output rate at acceptable level, for example at 2x 10 33 cm -1 s -1:  L1 2-jet trigger threshold O(100 GeV) per jet But: 120 GeV Higgs decays preferably into 2 b-jets with ~60 GeV each Possible strategies:  Rely on muon trigger only, where 2-muon trigger thresholds are 3 GeV  Take hit in statistics  Allow lower jet thresholds by assigning bigger chunk of available bandwidth  Could be considered once Higgs has been found and one knows where to look  Allow lower jet thresholds without increase in assigned bandwidth by combining central detector jet condition with condition on forward proton taggers

24. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 24 → Trigger thresholds for nominal LHC running too high for diffractive events → Use information of forward detectors to lower in particular CMS jet trigger thresholds → The CMS trigger menus now foresee a dedicated forward detectors trigger stream with 1% of the total bandwidth on L1 and HLT (1 kHz and 1 Hz) single-sided 220m condition without and with cut on  Achievable total reduction: 10 (single-sided 220m) x 2 (jet iso) x 2 (2 jets same hemisphere as p) = 40 Experimental challenge: Trigger A dedicated forward detectors L1 trigger stream Demonstrated that for luminosities up to 2x 10 33 cm -1 s -1 including 220m detectors into the L1 trigger provides a rate reduction sufficient to lower the 2-jet threshold substantially, to 40GeV, while requiring only 1% of L1 bandwidth !

25. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 25 H(120 GeV) → b bbar L1 trigger threshold [GeV] Efficiency 420m 220m 420+420m 420+220m Experimental challenge: Trigger Trigger Efficiency for central exclusive Higgs production Central exclusive production pp  pHp with H (120GeV)  bb: Assuming 1% of total bandwidth available: Di-jet trigger threshold of 40GeV & single-sided 220m condition possible, would retain 10% of the events This would double the efficiency provided by the CMS muon trigger (no fwd detectors condition) Central exclusive production pp  pHp with H (140GeV)  WW: Same efficiency as non-CEP production, no improvement from fwd detectors jet trigger condition

26. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 26 Experimental challenge: Pile-up background !

27. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 27 TOTEM x L =P’/P beam =  det@420 d  (ep  eXp)/dx L [nb] Number of PU events with protons within acceptance of near-beam detectors on either side: ~2 % with p @ 420m ~6 % with p @ 220m Coincidence of non-diffractive event with protons from pile-up events in the near-beam detectors:  fake double-Pomeron exchange signature Experimental challenge: Pile-up background Pile-up background (II) Non-diffractive event with signature in the central CMS detector identical to some DPE signal event: At 2x 10 33 cm -2 s -1 10% of these non-diffractive events will be mis-identified as DPE event. This is independent of the specific signal. Diff events characterized by low fractional proton momentum loss diffractive peak

28. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 28 Can be reduced on the High Level trigger: Requiring correlation between ξ, M measured in the central detector and ξ, M measured by the near-beam detectors Fast timing detectors that can determine whether the protons seen in the near-beam detector came from the same vertex as the hard scatter within 3mm Further offline cuts possible: Condition that no second vertex be found within 3mm vertex window left open by fast timing detectors Exploiting difference in multiplicity between diff signal and non-diff background Experimental challenge: Pile-up background Handles against pile-up background ;  1  2 s = M 2 (p tagger) (jets) CEP H(120)  bb incl QCD di-jets + PU M(2-jets)/M(p’s) CEP of H(120 GeV) → b bbar and H(140 GeV) → WW: S/B of unity for a SM Higgs

29. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 29 Experimental issues of detecting diffractive processes at the LHC discussed in: Prospects for diffractive and forward physics at the LHC, CERN/LHC 2006-039/G-124 Written by CMS and TOTEM to express interest in carrying out a joint program of diffractive and forward physics as part of the routine data taking at the CMS IP, i.e. up to the highest available luminosities and spanning the full lifetime of the LHC. Side remark: CMS + Totem (+ FP420) program Program covers in addition to central exclusive production: Diffraction in the presence of a hard scale: “Looking at the proton through a lense that filters out anything but the vacuum quantum numbers Diffractive structure functions Soft rescattering effects/underlying event and rapidity gap survival factor Low x BJ structure of the proton Saturation, color glass condensates Rich program of  and  p physics Validation of cosmic ray air shower MC

30. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 30 Current status of FP420 and Summary

31. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 31  FP420 is an R&D collaboration with members from ATLAS, CMS and the LHC  FP420 aims at providing the necessary tools for measuring central exclusive production at the LHC under nominal LHC running conditions  FP420 suggests to instrument the location 420m from the ATLAS/CMS IP with Silicon tracking detectors and fast TOF detectors FP420 will extend the physics potential of the ATLAS/CMS baseline detectors:  For the SM Higgs, FP420 makes feasible observing a light SM Higgs in the bb decay channel  For the MSSM Higgs, in certain parts of the parameter space FP420 has discoverypotential  FP420 renders possible a direct measurement of the Higgs quantum numbers  Both in ATLAS and CMS internal evaluation of FP420 proposal has started  FP420 is preparing a Technical Design Proposal with the results of R&D studies  If approved by ATLAS (CMS) as proper ATLAS (CMS) project, independent Technical Design Proposals for ATLAS-FP420 and CMS-FP420, building on common R&D Installation could take place in 2009/2010, i.e. no interference with LHC start-up

32. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 32 BACKUP

33. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 33 The physics case for FP420 MSSM: intense coupling regime Intense-coupling regime of the MSSM: M h ~M A ~ M H ~ O(100GeV): their coupling to, WW*, ZZ* strongly suppressed  discovery very challenging at the LHC Cross section of two scalar (0+) Higgs bosons enhanced compared to SM Higgs Production of pseudo-scalar (O-) Higgs suppressed because of J Z selection rule Superior missing mass resolution from tagged protons allows to separate h, H Spin-partity of Higgs can be determined from the azimuthal angles between the two tagged protons (recall J Z rule only approximate)  CEP as discovery channel see Kaidalov et al, hep-ph/0307064, hep-ph/0311023 100 fb 1 fb 120 140 

34. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 34 The physics case for FP420 MSSM: intense coupling regime 100 fb 1 fb Azimuthal angle between outgoing protons sensitive to Higgs spin-parity: J P =0 + vs J P =0 - (recall J Z selection rule only approximate)     Kaidalov et al., hep-ph/0307064

35. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 35 MSSM Scenario Studies M A = 130 GeV tan  = 50 H  bb S. Heinemeyer et al to appear Contours of ratio of signal events in the MSSM over the SM No-mixing scenario

36. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 36 TOTEM x L =P’/P beam =  det @420 d  (ep  eXp)/dx L [nb] CMS + TOTEM (+ FP420) Unprecedented kinematic coverage TOTEM T2: GEM tracking detector CMS Castor thungsten/quartz Cherenkov calorimeter CMS ZDC thungsten/quartz Cherenkov calorimeter TOTEM Silicon tracking det. housed in Roman pots Castor ZDC

37. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 37 ALFA and LUCID ALFA: Absolute Luminosity for ATLAS 2 stations at 240m from ATLAS IP approaching the beam to within 1.2mm 10+10 planes of scintillating fibre detectors  spatial resolution 30  m  edge <100  m Installation of detectors during first long LHC shutdown (2009 ?) LUCID: Luminosity measurement with a Cherenkov Integrating Detector Aluminium tubes filled with isobutane in cylinder (length 1.5m, diameter 13.7cm) around beam pipe 17 m from ATLAS IP Absolute lumi measurement at ~ 10 -27 cm -2 s -1 Extrapolation from there to luminosity at nominal LHC running via track counting in LUCID

38. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 38 Forward detectors at ATLAS/CMS IP’s possible upgrade RP220 with Si detectors possible addition SLHC

39. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 39 cc c c H proceeds via the same diagram but t-loop instead of c-loop Important for calibrating models on diffractive Higgs M J/  pp pp J  cc On the way to diffractive Higgs production: 10 candidate events (but unknown background)   49  18 (stat)  39 (syst) pb for exclusive  c production for |y|<0.6 CDF: exclusive processes at Fermilab (II)

40. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 40 Online: Beam-Position Monitors plus a wire- positioning system: aiming for 10 micron precision on beam-detector separation. Alignment

41. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007 41