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ATLAS Forward Protons and Trigger

ATLAS Forward Protons and Trigger. Andrew Brandt (UT-Arlington). Who am I? B.S. College of William&Mary 1985 PH.D. UCLA/CERN (UA8 Experiment-discovered hard diffraction) 1992 1992-1999 Post-doc and Wilson Fellow at Fermilab -Discovered hard color singlet exchange JGJ

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ATLAS Forward Protons and Trigger

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  1. ATLAS Forward Protons and Trigger Andrew Brandt (UT-Arlington) • Who am I? • B.S. College of William&Mary 1985 • PH.D. UCLA/CERN (UA8 Experiment-discovered hard diffraction) 1992 • 1992-1999 Post-doc and Wilson Fellow at Fermilab • -Discovered hard color singlet exchange JGJ • -1997 PECASE Award for contributions to diffraction • -Proposed and built (with collaborators from Brazil) • DØ Forward Proton Detector • -QCD and Run I Physics Convenor • -Trigger Meister, QCDTrigger Board Rep., Designed Run II Trigger List • 1999-2004 present UTA Assistant Prof 2004-present Assoc. Prof • -OJI, MRI, ARP awards for DØ FPD • -2005 started fast timing work (ARP, DOE ADR) • -2008 sabbatical on ATLAS • ATLAS Forward Protons • ATLAS Trigger • Miscellaneous related stuff DOE Review Nov. 14, 2008 Arlington, TX

  2. -jet gap gap H h p p -jet beam dipole dipole p’ roman pots p’ Forward Protons at LHC (FP420, AFP) Central Exclusive Higgs production pp p H p : 3-10 fb E.g. V. Khoze et al M. Boonekamp et al. B. Cox et al. V. Petrov et al… Levin et al… M = O(2.0) GeV I had a major editorial role in both documents and am on the Management Board of both groups ``The FP420 R&D Project: Higgs and New Physics with Forward Protons at the LHC,'' FP420 R&D, arXiv:0806.0302 [hep-ex]. ``Letter of Intent for ATLAS FP: A project to install forward proton detectors at 220 m and 420 m upstream and downstream of the ATLAS detector,'' A. Brandt, B. Cox, C. Royon et al., AFP Collaboration, http://www.cern.ch/jenni/AFP.loi\_atlas.pdf.

  3. Physics of AFP • At lowish luminosity (30-60 fb-1) we can : • Establish the quantum numbers of SM Higgs • Be the discovery channel in certain regions of the MSSM • Make high precision measurements of WW / ZZ couplings • Perform interesting QCD measurements (0.002 < xIP < 0.015 ) • In addition, at higher luminosity (> 100 fb-1) we can : • Discover exotic bound states such as gluinoballs • Make direct observation of CP violation in some SUSY Higgs scenarios • Disentangle wide range of SUSY scenarios, including ~degenerate Higgs • FP420 turns the LHC into a energy tunable glue-glue (and ) collider

  4. FP420 Components • Modified Cryostat to create space for detectors and allow detector movement close to the beam • 3D silicon detector for position measurement (also being developed as a solution for ATLAS upgrade silicon detector due to rad hardness) • Fast TOF counter for pileup rejection

  5. Pileup Background • Example: 3 interactions, one with hard scatter, and two with diffractive protons • This is a huge concern due to high rates of single diffraction (1% of diffractive protons give a hit within the detectors) • At UTA we (Brandt, Duarte, Pal, Spivey, Howley) have been addressing this issue in two ways: 1) By studying exclusive Higgs signal and pileup backgrounds, developing and testing new pileup rejection variables 2) By developing a timing detector to reject events where the protons do not come from the central vertex

  6. Test Beam Studies for FP420 Fast Timing Developers: UTA (Brandt), Louvain, Alberta, FNAL WHO? TB shifters: UTA, UC-London, Louvain, Prague WHY? Pileup Background Rejection Use time difference between protons to measure z-vertex and compare with tracking z-vertex measured with silicon detector How? 10 picoseconds original design goal (light travels 3mm in 10 psec!) gives large factor of background rejection; phased plan, start with 20 ps (<2 year timescale), need better than 10 ps for full machine luminosity (<4 years) How Fast?

  7. Fast Timing Is Hard! ISSUES Time resolution for the full detector system: 1. Intrinsec detector time resolution 2. Jitter in PMT's 3. Electronics (AMP/CFD/TDC) • 3 mm =10 ps • Detector • Phototube • Electronics • Reference timing • Rad Hardness of detector, phototube and electronics, where to put electronics in tunnel • Lifetime and recovery time of tube, grounding • Background in detector and MCP • Multiple proton timing

  8. FP420 Baseline Plan 2 QUARTICs 1 GASTOF Lots of 3D silicon • Two types of Cerenkov detector are employed: • GASTOF – a gas Cerenkov detector that makes a single measurement • QUARTIC – two QUARTIC detectors each with 4 rows of 8 fused silica bar allowing up to a 4-fold improvement over the single bar resolution • Both detectors use Micro Channel Plate PMTs (MCP-PMTs)

  9. The Detectors : 1) GASTOF (Louvain) Not so much light since use gas, but full Cerenkov cone is captured. Simulations show yield of about 10 pe accepted within few ps! 1 measurement of ~10 ps

  10. The Detectors : 2) QUARTIC proton 4x8 array of 6 mm2 fused silica bars UTA, Alberta, FNAL Only need 40 ps measurement if you can do it 16 times (2 detectors with 8 bars each)! photons

  11. Updated station layout. 3D silicon + GASTOF or QUARTIC Mobile BPM welded on station and calibrated with respect to pockets

  12. Test Beam Layout

  13. Latest QUARTIC Prototype HC HH HE Testing long bars 90 mm (HE to HH) and mini bars 15 mm (HA to HD) Long bars more light from total internal reflection vs. losses from reflection in air light guide, but more time dispersion due to n()

  14. QUARTIC Ray Tracing ~ 5 pe’s accepted in 40 ps 15mm Quartz/75 mm air 20 ps 90mm Quartz ~ 10 pe’s accepted in 40 ps 40 ps 40 ps

  15. QUARTIC: Photonis Planacon 10 m pore 8x8 Gastof: Hamamatsu 6 m pore single channel or equivalent Photek MCP-PMT Fast Scope Preamplifier LCFD SMA SMA Lemo SMA Fast Scope Electronics Louvain Custom CFD (LCFD) • Experiment channel Mini-circuits ZX60 6 GHZ or equivalent HPTDC board (Alberta) interfaces to ATLAS Rod For GASTOF replace CFD/TDCwith single photon counter (b) or (c) TB channel

  16. FP420 Timing Setup G2 G1 Q1 Amplifiers

  17. Data Acquisition • Lecroy 8620A 6 GHz 20 Gs (UTA) • Lecroy 7300A 3 GHz 20/10 Gs (Louvain) • Remotely operated from control room using TightVNC • Transfer data periodically with external USB drive UTA funding from DOE ADR grant and Texas ARP grant

  18. Good Event 5 ns/major division

  19. Online Screen Capture one histo is 10 ps per bin others are 20 ps histogram delta time between channels FWHM<100 so /2.36 ->dt~40 ps

  20. overflow -> switch from 100 to 200 mv scale acceptance Offline Analysis • Too cumbersome, not getting results in timely manner • I implement streamlined approach + round the clock analysis shifts (one data taking shifter, one analysis shifter: Nicolas, Vlasta, Shane) -start with basics -plot pulses -pulse heights -low threshold cut -raw times -time differences -add tracking later

  21. Determining Pulse Time Hamamatsu(G1) Burle (HF) LCFD (HFc) Linear fit, use 50% time

  22. QUARTIC Long Bars after LCFD Dt 56.6/1.4=40 ps/bar including CFD! Time difference between two 9 cm quartz bars after constant fraction discrimination is 56 ps, implies a single bar resolution of 40 ps

  23. LCFD Resolution Split signal, take difference of raw time and CFD time-> LCFD resolution <27 ps This implies detector+tube ~30 ps

  24. Tracking /Scope Synchronization (a) (b) Events All tracks HEc On 6mm (c) Efficiency Use tracking to determine that QUARTIC bar efficiency is high and uniform 6 mm Strip #

  25. GASTOF Displaced 19 mm All tracks Multiple scattering effects in 400 um wide, 30 cm long stainless steel edge of GASTOF (cause veto)! 1mm depletion implies tracking projection issues, detector tilted slightly, or both GASTOF On dip ~1 mm wide edge

  26. Laser Tests mirror PMT Howley, Hall, Lim laser diode lenses filter splitter Debugging laser setup currently 25 ps resolution for a channels of 4 channel 25 m tube, will study as fct. of filter and HV

  27. ATLAS Forward Proton Summary and Outlook • June TB two weeks of running, tremendous effort • 100+Gb of scope data, sizable fraction synchronized with tracking from Bonn telescope • Demonstrated good data, now finalizing results, plan to write a paper this year • LOI submitted to ATLAS in September • Will need more laser tests, simulation and test beam before design is finalized • Plan to continue tests and help secure ATLAS approval of LOI, build U.S. ATLAS collaboration for Phase 1+2 funding

  28. Sabbatical/Trigger • Major emphasis of Sabbatical was to start new UTA effort on ATLAS trigger (with Sarkisyan+Pal) • Organized Trigger Robustness Workshop • CSC chapter editor • Forward jet commissioning • Minbias Trigger Validation + Low PT tracking • Dijet trigger rates • Diffractive triggers • Chair Trigger Rates group, added to Trigger Coordination Group (continuing responsibility) • Many talks in menu+jet meeting, SM talk, 2 plenary talks, joined Tdaq

  29. Trigger Robustness Workshop organized by: Andrew Brandt (UT-Arlington) Ricardo Goncalo (Royal Holloway) Goals: 1) Evaluate ability of trigger system to cope with readout, detector, and beam related problems 2) Generate list of problems and a strategy to address them was held March 4, 2008 at CERN Successful one day workshop with 25 short talks and lots of discussion Agenda: http://indico.cern.ch/conferenceOtherViews.py?view=standard&confId=29007 Robustness twiki to document progress and follow-up: https://twiki.cern.ch/twiki/bin/view/Atlas/TriggerRobustness

  30. Gordon Watts got us off to a rousing start with a quote from an Infamous American Poet on large experiment Trigger/DAQ The UnknownAs we know, There are known knowns. There are things we know we know. We also know There are known unknowns. That is to say We know there are some things We do not know. But there are also unknown unknowns, The ones we don't know We don't know. Known problems Ununderstood problems Don’t even know you have them problems! —Feb. 12, 2002, Department of Defense news briefing Automated Systems (or shifters) Experts and Detector/Trigger Groups G. Watts (UW/CPPM)

  31. Beam-related Background • Result: Several slices (muon, MET, jet) showed insensitivity to beam backgrounds using halo (from scattering off tertiary collimator) and beam gas events generated by Alden Stradling (Wisc./UTA). -Halo events provide low pT muons but these did not tend to give triggers. Absolute beam gas rates are expected to be very low. -The level of impact on the trigger was consistent with noise in the detector, such that if jet thresholds are at least 10 GeV and MET thresholds at least 25 GeV, then very little impact on trigger is expected, even if backgrounds were to be much worse than anticipated. -Provided important information to ATLAS beam background WG (of which I was a member) • Follow-up: Encouraging results indicate that beam backgrounds are not likely to be a serious issue for trigger, nevertheless HLT algorithms to recognize unphysical patterns of energy deposition are being developed, should the rates turn out to be unexpectedly large. Generation of larger and more complete data samples should be pursued.

  32. Andrew Brandt (UT-Arlington) Dijet Samples: Rates&More 0.4nb-> don’t care about J6-J8! Current trigger rates for experiment at 1031 calculated using a 7 Million event minimum bias sample, gives large rate uncertainty as luminosity goes up, Ex. 1 event = 10 Hz at 1033 (1 nb = 1 Hz at 1033) Started investigating strategy for better rate measurements (see March 19 menu talk, March 26 jet talk, April 9 menu talk, April 16 jet talk) Some of the results may be relevant for Standard Model Jet Physics 8-17 J0(J2) 2(3) M events other samples 400-600k (200k for J8) Big thanks to Edward Sarkisyan-Grinbaum for plots, endless MC generation, Arnab Pal, Marc-Andre, Bilge for rate help SM Meeting May 6, 2008 CERN

  33. Standard Jx Samples Harder than Min Bias Truth Reco Note: sum of Jx’s (black-dashed curve) is greater than blue min bias, for standard dijet samples With some pain we found this was due to MC version; MB was PYTHIA 6.4 while Jx was PYTHIA 6.3

  34. Agreement Between Our J0-J3 and MB We used PYTHIA 6.412 with ATLAS default tune, scaled by number of events and cross section ratio (we used 70 mb for min bias) Note messy features of upper cuts samples: turn-on and turn-off, mixing of bins, statistical fluctuations

  35. PYTHIA 6.3 vs. 6.4 J1 PYTHIA6.3 J0 PYTHIA 6.323 (default sample) J0 PYTHIA 6.403 J1 PYTHIA 6.4 Differences large at low pT small at high pT J3 J2

  36. PYTIA 6.3 vs. 6.4 Difference • “Weird” events at high pT of PYTHIA 6.3 samples apparently due to new shower model which showers to beam energy cutoff scale instead of hard parton scale. This effect occurs in all bins, but causes most significant problems in low pT bins since these bins have a big weighting factor and the effects are relatively much more significant for low parton pT • Although it is not guaranteed that PYTHIA 6.4 is more correct than 6.3, it is now the default to have less showering and it seems to make better physics sense (see rates)

  37. Trigger Rate Implication • Abnormally high trigger rates clearly due to PYTHIA 6.3 vs 6.4 difference (*my office!) Implies multi-jet rates way over-estimated, and single jet rates over-est. by ~30%

  38. JNu Samples Convinced ATLAS management to try JNu (no uppercut filtered samples) for trigger rate and possibly physics studies (real life has no uppercut!)

  39. Low-pT Tracking Performance Edward Sarkisyan-Grinbaum(UTA) • ATLAS Performance and Physics Workshop (Nov. 5-7, 2008) • Tracking Session & Standard Model Meeting • http://indico.cern.ch/conferenceDisplay.py?confId=41483 • A key ingredient of basic (very) early measurements • Physics interests: early QCD, minbias, diffraction, gaps, jets… • Critical for understanding underlying events, pile-up, precise • measurements background • Practical interest: detector, SW comissioning, tuning models

  40. Why low-pT Tracking Reconstruction is difficult: high curvature of tracks, increased multiple scattering, reduced # of hits Low-Pt tracking completes the full track-finding strategy (global-chi2, Kalman-filter, dynamic noise adjustment, Gaussian-sum filters, deterministic annealing filter, pattern recogn., back track-finding)

  41. Subset of Edward’s Current Activity • Efficiency and fake rates studies based on truth matching • Comparison of different physics processes such as Minbias - SD - DD • Studying hits in different tracking sub-detectors • Rerunning GEANT4 simulations with lower thresholds • Studies to look for secondaries that might be mistaken as primaries (vertex, impact parameter studies) • Minbias Validation • Min bias and gap physics

  42. Diffraction in ATLAS • Diffraction is a top level physics group in CMS, but until very recently, there was almost • no diffraction in ATLAS • Discussion of soft diffraction, but only as background to min bias (that really hurts!) • There was a Luminosity and Forward Detector WG with the idea • of possibly doing diffractive physics with ATLAS pots • Andrew Pilkington (Manchester) and I started grass roots effort early • this year now we have risen to sub-sub group status! • (as part of SM sub-group with QCD+MinBias) • Early focus is on two topics: • 1) Central Exclusive Diffraction • 2) Gaps between jets (ET > 30 GeV, s = 1800 GeV) f Dh jet jet DØ EVENT h

  43. ATLAS Gap Trigger Strategy Standard jet thresholds too highly prescaled for CEP studies. Short term option: Use MBTS information to define a lack of activity in the forward region. Long term goal: Use MBTS, BCM, LUCID and ZDC to define a variety of gap definitions. • Possible gap triggers in 10TeV run: • Require one jet passing J18 (J10 probably too noisy, J35 too high) + veto on MBTS_1_1 (veto of hits on both sides means no hits on one side or no hits on either side). • Investigating other MBTS terms such as inner ring veto on one side + outer ring coincidence on other • Space points at L2 could be used to suppress L1Calo noise

  44. Gap Trigger Efficiency • Gap trigger is ~65% for EXHUME CED signal sample (pT>35 GeV) • Gives 10k rejection of non-diffractive; would bring prescale close to 1 MBTS veto added

  45. Gap Summary • Central exclusive production can be measured with 10-100pb-1 of data. • Helps to understand underlying event, parton distributions, Sudakov suppression • Constrains theoretical models on diffractive Higgs • Forward jet measurements with early data can shed light on the nature of hard color singlet exchange. • Only needs ~10 pb-1 of data. • Helps understand forward jets for VBF studies • Triggers added to default trigger list

  46. ATLAS Activities Summary/Outlook • With excellent support from DOE and UTA, I had a very successful sabbatical opening up new trigger areas, some of which I will continue in coming year (especially trigger rates) • Edward also got fully integrated (joined UTA in Feb.) • Plan to continue with AFP studies and approval • Will pursue project funds for trigger work • Need adequate travel support to allow four trips to CERN + one month in summer to maintain effectiveness in ATLAS

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