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Monika Grothe U Turin/ U Wisconsin Johns-Hopkins workshop Heidelberg August 2007

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 ?.

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Monika Grothe U Turin/ U Wisconsin Johns-Hopkins workshop Heidelberg August 2007

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

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

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

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

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

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

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

  9. beam dipole dipole p’ roman pots p’ roman pots Measuring central exclusive production:Principle of measurement Diffractively scattered protons survive interaction intact and lose only a small fraction of their initial momentum in the process 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 Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

  10. beam dipole dipole x=0.015 x=0.002 p’ x=0 (beam) roman pots p’ roman pots Measuring central exclusive production:Where to put the detectors With nominal LHC optics: 12 s = M2 With √s=14TeV, M=120GeV on average:  0.009  1% fractional momentum loss of the proton Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

  11. Measuring central exclusive production:Where to put the detectors (II) 12s = M2 With √s=14TeV, M=120GeV on average:  0.009  1% Nominal LHC beam optics Low * (0.5m): Lumi 1033-1034cm-2s-1 @220m: 0.02 <  < 0.2 @420m: 0.002 <  < 0.02 • 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 Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

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

  13. Existing proton tagging detectors TOTEM det @420 d(epeXp)/dxL [nb] xL=P’/Pbeam= 1-x data points from ZEUS • 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 Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

  14. The FP420 R&D project 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 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 LHCC acknowledges the scientific merit of the FP420 physics program and the interest in its exploring its feasibility.” - LHCC Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

  15. FP420 project: How to integrate detectors into the cold section of the LHC scattered protons emerge here 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 Turin / Cockcroft Institute / CERN Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

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

  17. Electrodes are processed inside the detector bulk instead of being implanted on the wafer’s surface. Active edges: the edge is itself an electrode, so dead volume at the edge < 5m. 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 1035 cm-2 s-1 • Use ATLAS pixel chip (rad hard) for readout • Prototype in CERN testbeams 2006 and 2007 • Technology is candidate for • ATLAS tracker SLHC upgrade Manchester / Stanford Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

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

  19. Injection of gas (~ atmospheric pressure) pump Ejection of gas Aluminium Cerenkov medium (ethane) Mirror Protons (Flat or Spherical?) ~ 15 cm ~ 5 cm Lens? (focusing) ~ 10 cm PMT FP420 project: Fast timing detectors 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 proton Cherenkov light QUARTIC (U Texas-Arlington): Cherenkov medium is fused Silica GASTOF (UC Louvain) Cherenkov medium is a gas Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

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

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

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

  23. Experimental challenge: TriggerThe difficulty of triggering on a 120GeV Higgs • Trigger at ATLAS/CMS based on high pT/ET jet and lepton candidates in event • In order to keep output rate at acceptable level, for example at 2x 1033 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 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

  24. Experimental challenge: TriggerA dedicated forward detectors L1 trigger stream → 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 Demonstrated that for luminosities up to 2x 1033 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 Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

  25. Experimental challenge: Trigger Trigger Efficiency for central exclusive Higgs production 420m Efficiency 220m 420+420m 420+220m H(120 GeV) → b bbar L1 trigger threshold [GeV] 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 Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

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

  27. Experimental challenge: Pile-up backgroundPile-up background (II) TOTEM d(epeXp)/dxL [nb] det@420 xL=P’/Pbeam= 1-x Diff events characterized by low fractional proton momentum loss diffractive peak 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 Non-diffractive event with signature in the central CMS detector identical to some DPE signal event: At 2x 1033 cm-2s-1 10% of these non-diffractive events will be mis-identified as DPE event. This is independent of the specific signal. Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

  28. Experimental challenge: Pile-up backgroundHandles against pile-up background Can be reduced on the High Level trigger: Requiring correlation between ξ, M measured in the central detector and ξ, Mmeasured 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 ; 12 s = M2 incl QCD di-jets + PU CEP H(120) bb (jets) (p tagger) CEP of H(120 GeV) → b bbar and H(140 GeV) → WW: S/B of unity for a SM Higgs M(2-jets)/M(p’s) Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

  29. Side remark:CMS + Totem (+ FP420) program 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. 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 xBJ structure of the proton • Saturation, color glass condensates • Rich program of and p physics • Validation of cosmic ray air shower MC Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

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

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

  33. The physics case for FP420MSSM: intense coupling regime • Intense-coupling regime of the MSSM: • Mh~MA ~ MH ~ 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 JZ 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 JZ rule only approximate) • CEP as discovery channel 100 fb see Kaidalov et al, hep-ph/0307064, hep-ph/0311023 - 1 fb 120 140 Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

  34. The physics case for FP420MSSM: intense coupling regime Azimuthal angle between outgoing protons sensitive to Higgs spin-parity: JP=0+ vs JP=0- (recall JZ selection rule only approximate) 100 fb 0 - 1 fb 0 + Kaidalov et al., hep-ph/0307064 Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

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

  36. CMS + TOTEM (+ FP420)Unprecedented kinematic coverage Castor Castor TOTEM det @420 d(epeXp)/dxL [nb] ZDC ZDC xL=P’/Pbeam= 1-x CMS Castor thungsten/quartz Cherenkov calorimeter TOTEM T2: GEM tracking detector CMS ZDC thungsten/quartz Cherenkov calorimeter TOTEM Silicon tracking det. housed in Roman pots 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 Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

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

  39. p p J/y cc g p p c c CDF: exclusive processes at Fermilab (II) On the way to diffractive Higgs production: cc • H proceeds via the same diagram • but t-loop instead of c-loop • Important for calibrating models on • diffractive Higgs 10 candidate events (but unknown background) s< 49  18 (stat)  39 (syst) pb for exclusive cc production for |y|<0.6 MJ/y-g Monika Grothe, Diffractive Higgs searches: The FP420 project, August 2007

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

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

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