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Status of diffractive Higgs studies

Status of diffractive Higgs studies. Marta, Monika, Michele. -jet. gap. gap. H. h. p. p. -jet. b. b. H. Khoze Martin Ryskin Eur. Phys.J. C23, 311 (2002) C25, 391 (2002) C26, 229 (2002). t. b. b. b. H. b. Exclusive diffractive Higgs @ LHC.

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Status of diffractive Higgs studies

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  1. Status of diffractive Higgs studies Marta, Monika, Michele -jet gap gap H h p p -jet CMS Torino Meeting

  2. b b H Khoze Martin Ryskin Eur. Phys.J. C23, 311 (2002) C25, 391 (2002) C26, 229 (2002) t b b b H b Exclusive diffractive Higgs @ LHC • For light Higgs (120 GeV) gg  H, H  bbar mode has highest branching ratio, but signal swamped by gg  bbar • Signal-to-background ratio improves dramatically • for 2 rapidity gaps and/or outgoing protons tagged • (LO background gg  bbar suppressed by JZ selection rule) • - s = 2-10 fb, for 30 fb-1 11 events • - S/B ~ 3 p gap b p gap M(bbar) p p MH= Mmissing if protons tagged, Δmmiss~ 1 GeV ! CMS Torino Meeting

  3. CMS/TOTEM forward physics project • EOI Gennaio 2004 • HERALHC workshop • http://www.desy.de/~heralhc • http://agenda.cern.ch/fullAgenda.php?ida=a05611 • (e.g. presentazioni di Albert de Roeck e Brian Cox) • Letter Of Intent CMS-TOTEM: • programma di fisica comune CMS-TOTEM • prevista per Giugno 2005 • Collaborazione internazionale per R&D delle stazioni a 420 m • membri di ATLAS, CMS, TOTEM, LHC • PPARC ha gia’ stanziato dei fondi, recentemente coinvolti USA e DESY • Statement Of Interest per LHCC prima dell’estate CMS Torino Meeting

  4. Forward detectors CMS IP T1/T2RPs @ 150mRPs @ 220m RPs@420m TOTEM detectors: T1 (CSC) in CMS endcaps T2(GEM) in shielding behind HF T1 + T2: 3 ≤ || ≤ 6.8 Roman pots(Si) on 2 sides at up to220 m Acc. for nominal LHC optics:0.02 < xi < 0.2 TOTEM fully integrated into CMS DAQ/trigger CMS:Castor calorimeter, downstream of T2 Under discussion:RPs at 420 m Acc. for nominal LHC optics:0.002 < xi < 0.2 T2 T1 T2 CMS Torino Meeting xi = 1-P’/Pbeam

  5. L1 and acceptance trigger studies: people • CMS: • Wisconsin(Sridhara Dasu, Creighton Hogg, MG) • Turin(MR, MG, MA) • Bristol(Richard Croft, Dave Newbold) • Anversa(Marek Tasevsky ) • Totem: • Helsinki(Ken Osterberg, Fredrik Oljemark) • Genova(Fabrizio Ferro) • CERN (Valentina Avati, Mario Deile) Weekly “CMS/TOTEM L1” meetings on Thursday at 4 pm! Though the focus for now is on L1 questions, the meeting has already proved to be a very good forum for information exchange with TOTEM CMS Torino Meeting

  6. Experimental challenges • Major but not insurmountable experimental difficulties: • event pile-up at high lumi is mostly elastic and diffractive • trigger: • on central Higgs: • L1 trigger tables require pT > 150 GeV and would reject • all such events which have max pT ~ 60 GeV • -> new strategies required • on protons (detected in T1/T2): • no acceptance at low xi • on protons (detected with Roman Pots at 420 m): • is the signal in time for L1? CMS Torino Meeting

  7. L1 and acceptance trigger studies: ingredients • Signal EDDE MC • Signal EXUME MC (based on KMR model ) • QCD background (PYTHIA) • Diffractive and elastic pileup (PYTHIA) • RP acceptance numbers (FAMOS) Numbers currently used have only xi-dependence New calculation with xi- and t-dependence available • T1/T2 OSCAR output ntuple CMS Torino Meeting

  8. Slide from Monika presentation @ HERALHC workshop Ongoing studies and their goal To answer: What can be done with central CMS L1 condition alone What can be done with (central CMS + RP at 220/420m) L1 cond. What can be won by adding T1/T2as veto condition on L1 With respect to: L1 QCD background rates L1 signal efficiency Pile-up events Reference luminosities: a) for signal events No pile-up case (e.g. for L=1032) (EDDE and Exhume L = 1033generators) L = 2x 1033 b) for QCD background L = 1034events (pythia) CMS Torino Meeting

  9. Slide from Monika presentation @ HERALHC workshop L1 2-jet rate for QCD background L1 rate (integrated) in kHz as function of 2-jet ET cutoff L = 1033 with full pile-up (including diff and elastics) L1 jet calibration applied Plot Creighton Hogg Blue: no HT cut Red:∑ (2-jetET)/HT > 0.9 Black: ∑ (2-jet ET)/HT > 0.95 2 isolated jet at L1 Algorithm: 2 jets in central Cal (|| <3) with∑(ET 2 jets) / HT > threshold HT = sum of the scalar ET of all jets in the event with ET(jet)>threshold Clearly needed additional L1 condition for 2-jet ET cutoff around 40GeV Note: L1 jet ET resolution ~30%, b pair from Higgs decay has ET < 60GeV First preliminary result with RP request: rate down by a factor 100! CMS Torino Meeting

  10. Slide from Monika presentation @ HERALHC workshop L1 efficiency studies for diff Higgs EDDE MC No RP cond. EXHUME MC No RP cond. Plots Richard Croft Signal L1 efficiency (integrated) as function of L1 2-jet ET cutoff for 2 central jets L1 jet ET calibration applied No pile-up CMS Torino Meeting

  11. Diffractive and elastic pileup • Soft diffractive & elastic events contribute substantially to pile-up • Crucial to study impact of pile-up on RP L1 condition. • Default CMS pile-up does include diffractive but not elastic events. Generated our own. • 55.2 mb standard Pythia • 22.2 mb elastic scattering • 7.2 mb single diffraction • 7.2 mb single diffraction • 9.7 mb double diffraction • Total cross section = 101,5 mb 46% of total cross section ! Example: @ L = 1033 3.22 events/b.crossing @ L = 1033 including elastic + diffractive 1.75 events/b.crossing excluding elastic + diffractive CMS Torino Meeting

  12. Slide from Monika presentation @ HERALHC workshop Pileup studies (I) Plot Marta Diffractive peak Prerequisite: Realistic MC simulation of diffractive events in pile-up Pile-up in CMS generated with Pythia, compare to HERA and pp leading proton data Leading protons xL= P’/Pbeam= 1-xi of fastest proton in event CMS Torino Meeting

  13. Slide from Monika presentation @ HERALHC workshop Pileup studies (II) xL= P’/Pbeam= 1-xi • Pythia too low outside diff peak • Pythia approx ok in diff peak • after taking shrinkage • (b = b0 + 4 alphaI ln s) • into account xL=P’/Pbeam= 1-xi • Pythia wrong in shape & normal. outside diff peak (~ factor 2-3) • Pythia approx ok in diffractive peak Plots Marta Ruspa CMS Torino Meeting

  14. In conclusione… • Il nostro contributo alla LOI: • Che cosa siamo realmente in grado di fare con TOTEM e CMS cosi’ come sono, sia in termini di trigger rate, sia in termini di efficienza? • Se ci sara’ tempo: • Di quanto migliorerebbero le cose se si aggiungessero altri rivelatori? • H (140 GeV)  W W* CMS Torino Meeting

  15. BACK UP CMS Torino Meeting

  16. Slide from Monika presentation @ HERALHC workshop Level-1 Jets and HT HCAL Trigger tower ECAL • HT = sum of scalar ET of all jets • Advantage over total scalar ET: • Sums only over ET around local energy maxima • More robust against noise and minimum bias events Diff Higgs at L1: L1 cut on ET(2jets)/HT t veto patterns PbWO4 crystal • 4x4 trigger towers = region • Search for jets with sliding 3x3 regions window • Jet = 3x3 region with ET in central region above some threshold and with ET> ET in any of 8 outer regions • Jet = t if t veto off in all 9 regions CMS Torino Meeting

  17. Slide from Monika presentation @ HERALHC workshop L1 trigger studies: the challenge 2 x 1033 cm-2 s-1 jet trigger rates Our poster-child process: H (120 GeV, DD prod)  b bbar L1 signature without fwd detectors: 2 jets in CMS cal, each ET < 60 GeV Calibrated L1 jet ET cut and resulting L1 2-jet rate: 110 GeV -- 1 kHz 60 GeV -- 10 kHz Target L1 output rate 75 kHz Need additional conditions to trigger a 120 GeV Higgs with L1: Forward detectors ! Note: Importance of studies goes beyond DD Higgs case to more general question of how to trigger with L1 on states with comparatively low ET CMS Torino Meeting

  18. Slide from Monika presentation @ LOI meeting Beam halo background in RPs Estimates available (M. Deile) for L = 0.5x 1033, 1.2x 1033 and 2x 1033 Example: Beam halo at L = 2x 1033 Estimates valid for RPs at 220 m and 420 m a) 2808 bunches with 0.52 x 1011 p/bunch single-arm rate: 0.7 MHz = 0.02/bunch double-arm coincidence: 16 kHz = 0.0005/BX b) 936 bunches with 0.90 x 1011 p/bunch single-arm rate: 0.4 MHz = 0.04/bunch double-arm coincidence: 18kHz = 0.0018/BX Precise numbers forthcoming, thanks to new and improved infos from HERA machine people CMS Torino Meeting

  19. Slide from Monika presentation @ LOI meeting Current MC situation • Available at U Wisconsin • 100k H (120) EDDE, for 1x1033, 2x1033, 1x1034 no pile-up • 100k H (140) EDDE, for 1x1033, 2x1033, 1x1034 no pile-up • 20k H(120) Exhume beta-version, no pile-up • 500k full pile-up events • 1 M QCD background events, pythia, no pile-up • In production at U Wisconsin: • 100k each: H (120) EDDE for 1x1033, 2x1033, 1x1034 with full pile-up • 1 M each: • QCD background events, pythia, • for 1x1033, 2x1033, 1x1034 with full pile-up • Coming soon: • 100k H (120) Exhume 1.0.0, • for no pile-up and for 1x1033, 2x1033, 1x1034 with full pile-up CMS Torino Meeting

  20. Slide from Monika presentation @ HERALHC workshop So far not addressed at all • So far discussed H (120 GeV)  b bbar only Another interesting case: H (140 GeV)  W W* • So far discussed Cal triggers only: Lepton triggers ? • Alignment trigger for the RPs at nominal LHC optics and luminosities ? In low lumi, special optics runs alignment w.r.t. beam line with elastics But even there may need additional method to align w.r.t. CMS • Question of minimum bias trigger: If request min. SumET in Cal: How low can one go before noise starts dominating ? For no pile-up case could request activity in T1/T2 ? CMS Torino Meeting

  21. Slide from Monika presentation @ HERALHC workshop Signal efficiency (integrated) as function of L1 2-jet ET cutoff for 2 central jets in CMS + RP cond L1 jet ET calibration applied No pile-up White: no HT cut Sum(2-jet ET)/HT > 0.7 red > 0.95 yellow Plots Richard Croft EXHUME MC Track on 1 side in 220m pots xi< 0.1 EDDE MC Track on 1 side in 220m pots xi< 0.1 EXHUME MC Track on 1 side in 420m pots xi< 0.05 EDDE MC Track on 1 side in 420m pots xi< 0.05 RP condition reduces 2-jet L1 trigger signal efficiency by factor ~2 Result of limited acceptance of RPs in diffractive peak region CMS Torino Meeting

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