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ATLAS Forward Protons: A (10) Picosecond Window on the Higgs Boson

ATLAS Forward Protons: A (10) Picosecond Window on the Higgs Boson. Andrew Brandt, University of Texas at Arlington. A picosecond is a trillionth of a second. This door opens ~once a second, if it opened every 10 picoseconds it would open a hundred

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ATLAS Forward Protons: A (10) Picosecond Window on the Higgs Boson

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  1. ATLAS Forward Protons: A (10) Picosecond Window on the Higgs Boson Andrew Brandt, University of Texas at Arlington A picosecond is a trillionth of a second. This door opens ~once a second, if it opened every 10 picoseconds it would open a hundred billion times in one second (100,000,000) Light can travel 7 times around the earth in one second but can only travel 3 mm in 10 psec Yes, I know it’s a door, not a window! Andrew Brandt SLAC Seminar

  2. Outline • Part I: Introduction to ATLAS Forward Proton • (AFP) proposal and physics motivation • Part II: Details of the AFP fast timing system Andrew Brandt SLAC Seminar

  3. NEW ATLAS Forward Protons (AFP) AFP: Proposes to use double proton tagging in conjunction with the ATLAS detector as a means to measure properties of Higgs (quantum numbers+mass) and other new physics Central Exclusive Production (QCD) Central Exclusive Production (QED) CEP: Momentum lost by protons goes entirely into mass of central system

  4. Central Exclusive Higgs AFP concept: adds new ATLAS sub-detectors at 220 and 420 m upstream and downstream of central detector to precisely measure the scattered protons to complement ATLAS discovery program. These detectors are designed to run at a luminosity of 1034 cm-2s-1 and operate with standard optics (need high luminosity for discovery physics) H 220 m 420 m beam LHC magnets You might ask: “Why build a 14 TeV collider and have 99% of your energy taken away by the protons, are you guys crazy or what??” p’ p’ AFP Detector The answer is “or what”!—ATLAS is always (or at least for a few weeks last December) losing energy down the beam pipe, we just measure it accurately!!! Note: the quest for optimal S/B can take you to interesting places: Ex. The leading discovery channel for light SM Higgs, H , has a branching ratio of 0.002!

  5. SM Higgs Branching Ratio • We know (we think) • that the Higgs gives particles mass through their coupling to the Higgs field • Theory constraints imply that the Higgs is “light” < 200 GeV • (not soooo light) • Various channels contribute discovery sensitivity depending on the exact Higgs mass MH= 140 GeV Andrew Brandt SLAC Seminar

  6. AFP Evolution • 2000 Khoze, Martin, Ryskin (KMR): Exclusive Higgs prediction Eur.Phys.J.C14:525-534,2000, hep-ph/0002072 • 2003-2004: joint CMS/ATLAS FP420 R&D collaboration forms • 2005 FP420 LOI presented to LHCC CERN-LHCC-2005-0254 “LHCC acknowledges the scientific merit of the FP420 physics programme and the interest in exploring its feasibility” • 2006-2007 Significant R&D funding in UK, modest funding in U.S. and other countries, major technical progress, RP220 formed • 2008 RP220 and AFP420 merge to form AFP, R&D continues, Cryostat design finalized with CERN, LOI to ATLAS submitted • 2009 “AFP year in review”, FP420 R&D document published in J. Inst (2009_JINST_4_T10001) • Nov. 2009 ATLAS approves AFP to develop a Technical Proposal Andrew Brandt SLAC Seminar

  7. Who is AFP? Other institutions have expressed interest—there is plenty to do! Andrew Brandt SLAC Seminar

  8. What is AFP? • Impressive array of rad-hard edgeless 3D silicon detectors (same sensors to be used in IBL upgrade) with resolution ~10 m, 1rad • Timing detectors with ~10 ps resolution for overlap background • rejection (SD+JJ+SD)—more on this in Part Deux • 3) New Connection Cryostat at 420m • 4) “Hamburg Beam Pipe” instead of Roman Pots • AFP is a rather vanilla name for this precision instrument: • I prefer VF3DSPDwithPST! • (Very Forward 3-D Silicon Proton Detector with Picosecond Timing) For more information: e-mail me at brandta@uta.edu or better yet, come to bonus session Su Dong has arranged at 3 pm Andrew Brandt SLAC Seminar

  9. proton AFP in Pictures New connection cryostat with integrated movable beam pipe houses 3-D silicon and timing detectors Timing detectors to reject background where protons and central system come from different interactions in same bunch crossing Movable beam pipe houses 3-D silicon and timing detectors Test Beam photons 1 Cryostat (warm-cold transition) 2 Support table for movable beampipe 3 Detector station 4 Vacuum valve QUARTIC Andrew Brandt SLAC Seminar

  10. What does AFP Provide? • Mass and rapidity of centrally system • where 1,2 are the fractional momentum loss of the protons (ex. =0 for elastic proton) • Mass resolution of 3-5 GeVper event Acceptance >40% for wide range of resonance mass Combination of 220 and 420 is key to physics reach! 420- 420 420- 220 220- 220 Allows ATLAS to use LHC as a tunable s glu-glu or  collider while simultaneously pursuing standard ATLAS physics program

  11. What is Special about CEP? Typical Higgs Production “+” “=” CEP Higgs pp  gg  H +x pp p+H+p • Extra “screening ” gluon conserves color, keeps proton intact (and reduces your ) • CEP defined as ppp+X+p , where protons are scattered at small angles, but remain intact, with all of their lost energy going towards production of the system X • Central system produced in Jz=0++ (C-even, P-even) state, this results in di-quark production being suppressed • More importantly: if you observe any resonance (for ex. Higgs), you automatically know its quantum numbers are 0++ Find a CEP resonance and you have measured its quantum numbers!!

  12. Does CEP Process Exist? CDF says yes! 1) Observation of Exclusive Dijets : (CDF) PR D77, 052004 (2008) σ(excl, jetETmin = 15 GeV) 112+84-50 pb. In agreement with ExHuME MC which incorporates Khoze, Martin, Ryskin (KMR) model for CEP (x3 theor. uncertainty) Why we care: same diagram as Higgs but with u/d loop instead of top loop 2) Observation of Exclusive χc : (CDF) PRL 102, 242001 (2009) dσ/dy(y=0) = 76 +/- 10 +/- 10 pb. Prediction (KMRS) = 90 pb Why we care: same diagram as Higgs but with c loop instead of top loop These support the prediction of KMR for standard model Higgs at the LHC (3 fb @ 120 GeV)

  13. Phenomenological Studies of BSM Higgs Since the KMR SM Higgs cross section prediction is pretty small: ~3fb, most of the recent theoretical work has focused on BSM Higgs, which can lead to enhanced cross sections for 1) MSSM (H->bb, H->ττ, H->WW*) • Heinemeyer, Khoze, Ryskin, Stirling, Tasevsky, Weiglein [Eur.Phys.J.C53:231-256,2008] • Cox, Loebinger, Pilkington [JHEP 0710:090,2007] 2) NMSSM (H->4τ) • Forshaw, Gunion, Hodgkinson, Papaefstathiou, Hodgkinson, Pilkington [JHEP 0804:090,2008] 3) CP-violating Higgs sector (H->bb, H->ττ) • Ellis, Lee, Pilaftsis [Phys.Rev.D71:075007,2005] • Cox, Forshaw, Lee, Monk, Pilaftsis [Phys.Rev.D68:075004,2003] 4) Triplet Higgs (H->bb) • Chaichian, Hoyer, Huitu, Khoze, Pilkington [JHEP 0905:011, 2009] • I will go through a few details of MSSM • and then get back to the SM Higgs Andrew Brandt SLAC Seminar

  14. 3 are absorbed from the H mechanism and give masses to W± and Z (as for SM Higgs) 5 physical Higgs bosons 8 degrees of freedom MSSM Higgs sector • In order to implement electroweak symmetry breaking into the MSSM, two Higgs doublets (H1, H2) are needed. • 2 CP even (h, H), 1 CP odd (A) and 2 charged H± • The MSSM Higgs sector (at tree level) is determined by 2 free parameters: MAand tanβ=v2/v1( the ratio of the vacuum expectation values of the 2 Higgs doublets) Courtesy of GiorgosDedes Seminar : Physik am Large Hadron Collider (LHC) Andrew Brandt SLAC Seminar

  15. MSSM and CEP • Models with extended Higgs sectors, such as the MSSM, typically produce a light Higgs (h) with SM-like properties and a heavy Higgs (H) which decouples from Gauge boson. This implies: • no HVV coupling (V=W, Z) • no weak boson fusion • no HZZ • big enhancement in • pseudoscalar A does not • couple to CEP R=(MSSMH)/(SMH) H→bb, mhmax, μ = 200 GeV R=300 mA (GeV) For the MSSM and related models, AFP is likely to provide the only way to determine the Higgs quantum #’s and the coupling to b-quarks, and will provide an excellent mass measurement.

  16. MSSM Higgs discovery/exclusion • Heinemeyer et al. studied CEP coverage of MSSM parameter space in mA-tan plane. • Plots show the 5σ contours for the light Higgs scalar boson (above) and heavy (below) for 60fb-1 and 600fb-1. • For large tan , Tevatron can already exclude part of the region. h/H→bb, mhmax, μ = 200 GeV TeV 5 contours, Hbb LEP

  17. Better pileup rejection Observing Higgs in the MSSM Cox. et.al. (JHEP 0710:090,2 007) • Pick: tan=40, mA=120 GeV, mh=120 GeV (MSSM h/SM H =8) and do detailed analysis including experimental efficiencies determined using TDR resolutions. Andrew Brandt SLAC Seminar

  18. H4 in the NMSSM • NMSSM Higgs sector consists of 3 neutral scalars and 2 neutral pseudo-scalars (and charged Higgs). • Most ‘natural’ part of parameter space results in light scalar Higgs (~100 GeV) Haa (`a’ is lightest pseudo-scalar) • Preferred decay of pseudo-scalar is a (thus two a’s4 taus). • ATLAS standard search channels are difficult and likely cannot measure the Higgs quantum numbers • Predict approx 7 CEP events after ~100fb-1 with no appreciable background (JHEP 0804:090,2008). (Trigger on e tau decays) • BONUS: information from forward protons gives good pseudo-scalar mass measurement! Andrew Brandt SLAC Seminar

  19. HWW* in the SM and MSSM • Cox et.al. (Eur.Phys.J.C45:401-407,2006) showed that the semi-leptonic decay of SM HWW* was possible for 130< mH<200GeV, using single muon/electron triggers for 30fb-1 of data. • Also have golden fully leptonic decay channel: small signal but negligible background. • Note: in the MSSM, cross section can be enhanced for lighter Higgs boson in the WW* channel as well by up to a factor of 4 relative to SM cross section. Enhancement with respect to SM Andrew Brandt SLAC Seminar

  20. AFP Internal Studies • AFP manpower primarily dedicated to detector R&D and technical studies, however… • We performed ATLFast and Full Sim studies over the last few years to validate • the predictions choosing 120 GeV for and 160 GeV for • We validated the exclusivity cuts needed to reduce the overlap background, including • tracking rejection with full detector simulation, trigger studies etc., but I can’t tell you • about that yet! Andrew Brandt SLAC Seminar

  21. Central Exclusive Photon-Photon Does it exist? Yes. Q.E.D. (a little Latin humor) Exclusive two-photon processes are characterized by exchange of virtual photons from protons. Photon fusion results in a system X of particles centrally produced and two intact protons, scattered at small angles.[1] For pair production, significant cross-sections (fb-level) are expected [2], with clean and unambiguous final states. Offers a novel possibility for the search of BSM particles [1] K. Piotrzkowski, Phys.Rev.D63(2001) 071502: Tagging two-photon production at LHC [2] Louvain photon group, arXiv: 0908.2020, High-energy photon interactions at the LHC

  22. Anomalous Quartic Gauge Couplings Event counting: for AFP trigger on2 high pT leptons (WW) • 95% CL limits for the AQGC for L=30fb-1: • >103 improvement over LEP limits, and 3-8x ATLAS w/o AFP • The inclusion of AFP is critical for rejection of background from parton-parton production of W pairs. (cross-section x BR x lepton acceptance = 1pb)‏ • Potentially sensitive to Higgsless models or other new physics • P.J. Bell, arXiv:0907.5299 • C. Royon, E. Chapon, O. Kepka, arXiv:0909.5237 ; O. Kepka,, C. Royon, (DAPNIA, Saclay) Phys. Rev. D78:073005,2008.

  23. Charged SUSY Production • Photon-photon production of charged SUSY pairs investigated in arXiv:0806.1097. • Benchmark points consistent with WMAP data examined. • Fully leptonic final states considered: • Two forward protons measured in forward detectors • Two leptons with opposite charge. (pTe > 10GeV, pT > 7GeV). 5 discovery with 25 fb-1 for light SUSY scenarios N.Schul and K.Piotrzkowski, arXiv: 0806.1097, Detection of two-photon exclusive production of susy pairs at the LHC

  24. But Wait, There’s More… • CEP dijets: measure unintegrated PDFs and can be used to calibrate jet energy scale • Diffraction: extends studies at HERA and Tevatron on dPDFs, survival probabilities (relevant to VBF) • Hard SD and DPE: dijets - sensitive to gluon dPDFs SD B-meson -sensitive to gluon dPDFs SD W/Z - sensitive to quark dPDFs SD Top – because we can • p: jet production to study the factorisation breaking in direct and resolved processes observed by H1, extend to xp<0.1 • single top: measure CKM matrix element V_tb • anomalous single-top: study anomalous single-top coupling • Odderon interaction in  • Charged Higgs in  Andrew Brandt SLAC Seminar

  25. AFP Summary AFP will provide ATLAS with a new sub-detector enabling a rich complementary physics program (our physics is your physics) Central Exclusive Production (QCD) • With sufficient luminosity, BSM Higgs bosons can be observed in CEP in a variety of mainstream models, many of them non-trivial for standard ATLAS techniques • The WW* channel looks very promising for SM Higgs of 130 GeV or above. • CEP provides excellent mass resolution • Observing CEP Higgs determines quantum numbers (0++) Central Exclusive Production (QED) • Superb anomalous quartic gauge coupling sensitivity could uncover new physics • Complementary SUSY sensitivity . Plus a variety of SM physics and speculative physics. Note: theoretical investigations of AFP capabilities are still in early stages. Andrew Brandt SLAC Seminar

  26. FP420/AFP Fast Timing UT-Arlington (Brandt), Alberta, UC-London, Prague, Saclay, Stonybrook, Giessen, Manchester, Fermilab, Louvain, Kansas WHO? WHY? Background Rejection for Diffractive Higgs Ex: Two b-jets from one interaction and two protons from another Use time difference between protons to measure z-vertex and compare with tracking z-vertex measured with silicon detector How? How Fast? 10 ps or better (to get x20 rejection) Andrew Brandt SLAC Seminar

  27. Ultra-fast Timing Issues Time resolution for the full detector system: 1. Intrinsec detector time resolution 2. Jitter in PMT's 3. Electronics (AMP/CFD/TDC) 4. Reference Timing • 3 mm =10 ps • Radiation hardness of all components of system • Lifetime and recovery time of tube • Backgrounds • Multiple proton timing Andrew Brandt SLAC Seminar

  28. Timing System Requirements • 10 ps or better resolution • Robust: capable of operating with little or no intervention in radiation environment (tunnel) • High efficiency • Acceptance over full range of proton x+y • Segmented (multi-proton timing) • Two main options: 1) one very precise measurement (GASTOF) 2) multiple less precise measurements (QUARTIC) Andrew Brandt SLAC Seminar

  29. FP420/AFP Timing • Two types of Cerenkov detector are employed: • QUARTIC – two QUARTIC detectors each with 4 rows of 8 fused silica bar allowing up to a 4-fold improvement over the single bar 40 ps measurement • GASTOF – a gas Cerenkov detector that makes a single 10 ps measurement • Both detectors use Micro Channel Plate PMTs • (MCP-PMTs) Andrew Brandt SLAC Seminar

  30. Micro-Channel Plate Photomultiplier Tube(MCP-PMT) e- + + photon Faceplate Photocathode Photoelectron DV ~ 200V Dual MCP DV ~ 2000V Gain ~ 106 MCP-PMT DV ~ 200V Anode

  31. ATLAS Solution: Option 2) • Choosing multiple measurements with modest resolution on 30-40 ps scale simplifies requirements in all phases of system 1) We have a readout solution for this option (later) 2) We can have a several meter cable run to a lower radiation area where CFD’s can be located, while TDC’s can be located even further away (the cable distortion is much more significant for sub-10 ps measurement) 3) Segmentation is natural for this type of detector Andrew Brandt SLAC Seminar

  32. 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

  33. QUARTIC Prototype Note: prior to June 2008 test beam, results marginal for QUARTIC 15mm bar: 80 ps/bar 80% efficient; allows you to reach close to 20 ps, but not 10 ps 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()

  34. QUARTIC Timing 2008 CERN TB Dt Npe=(area/rms)2 56.6/1.4=40 ps/bar using Burle 64 channel 10 m pore tube including CFD! Time difference between two 9 cm quartz bars after Louvain constant fraction implies a single bar resolution of 40 ps for about 10 pe’s (expected 10 pe’s from simulations). Need to demonstrate N (more later)

  35. QUARTIC Efficiency CERN TB (a) (b) All tracks (Bonn Silicon Telescope) Tracks with a Quartz bar on Events Shape due to veto counter with 15mm diameter hole 6mm Use tracking (b)/(a) to determine that QUARTIC bar efficiency is high and uniform (c) Efficiency 6 mm Strip #

  36. Timing Progress in 2009 • Established UTA Picosecond Test Facility (PTF) for laser tests • Developed in depth understanding of MCP-PMT performance • Investigated rate and lifetime issues • Formed collaborations with Arradiance, Photek, and Photonis (including submission of UK and UTA funding proposals) • Built a new prototype detector • Validated readout electronics • Albrow obtains 20-30 ps for a single 90 mm QUARTIC bar with single channel Photek 3 m pore PMT (T979 at FNAL) Andrew Brandt SLAC Seminar

  37. Rate and Current Limits • The baseline QUARTIC detector could see rates of up to 15 MHz in the hottest 6mm x 6mm pixel of the MCP-PMT. If the current: Anode Current = proton frequency x number of photo-electrons generated by each proton x charge x gain is too high (~10% of strip current) the tube saturates(gain is reduced) • To keep the current at tolerable levels, lower gain and less pe’s are desirable, but precise timing requires as many pe’s as possible (and conventional wisdom also indicated that high gain was necessary*). Smaller pores both reduces the current in any one pore and improves the timing • With 10 pe’s expected for a QUARTIC bar, if a gain of 5x104 were possible instead of the canonical 106(!), we would require a maximum current of about 3 A/cm2, a factor of several higher than standard MCP-PMT’s, but possible for new generation of Photonis MCP-PMT’s *Stay tuned for laser test results!

  38. Lifetime Issues Lifetime due to positive ions damaging the photocathode is believed to be proportional to extracted charge: Q/year = I*107 sec/year Q at maximum luminosity is up to 35 C/cm2/yr ! (assuming 5x104 gain!) Without a factor of 20 reduction in gain, the current and lifetime issues would make MCP-PMT’s unusable, with it the rate is borderline, but lifetime off by a factor of 50—tube dies every week! Solution: Graduate student camps out in tunnel to exchange tubes as needed. (Sorry Ian)

  39. N. Kishimoto, et al., Nucl. Instr. and Meth. A 564 (2006) 204. Relative QE as function of wavelength shows damage is much less in UV than visible Lifetime Measurements Barrier Aluminum ion barrier layer on top of MCP suppresses positive ions, increases lifetime by x5 to 6 No barrier

  40. Options for Improved Lifetime MCP-PMT • Ion barrier, already demonstrated, this promises a factor 5 to 6 lifetime improvement (at the cost of a 40-50% collection efficiency reduction) • Electron scrubbing, already demonstrated internally by Photonis, promises a factor 5 to 10 lifetime improvement • Z-stack, already demonstrated, this promises a factor of 10 lifetime improvement (A.Yu. Barnyakov, et al., Nucl. Instr. and Meth. A 598 (2009) 160) • Arradiance coated MCP’s, to be demonstrated, this promises a factor of 10 or more lifetime improvement (Grants submitted by UTA and Manchester to fund insertion of Arradiance MCP’s in Photonis and Photek tubes: “Development of a Long Life Microchannel Plate Photomultiplier Tube for High Flux Applications through the Innovative Application of Nanofilms”) • Various combinations of these factors are possible and should give multiplicative improvement factors, except for the electron scrubbing and Arradiance coating, which would be expected to be orthogonal Andrew Brandt SLAC Seminar

  41. Conclusions of Internal Lifetime Note Combination of lower gain running and higher current tube implies that expected rates/currents at 1034 are acceptable with existing technology. After accounting for lower gain running the discrepancy factor for the lifetime required for tube to survive 1 LHC year at 1034 luminosity is about a factor of 50 at 220 m as current QUARTIC detector design require a 35 C/cm2 MCP-PMT Pursuing the funding necessary to develop 50x longer life MCP-PMT’s. Given the different possible lifetime options, we have no doubt that this can be achieved with MCP-PMT technology Andrew Brandt SLAC Seminar

  42. Laser Test Goals • Develop flexible laser test facility • Study properties of MCP-PMT’s • Optimize electronics • Some issues to address: • How does timing depend on gain ? • What is minimum gain for 10 pe’s? Need to validate low gain operations. 3) What is maximum rate at which tube can operate? • Evaluate amp/CFD/TDC choices at detector working point 5) Eventually lifetime tests Andrew Brandt SLAC Seminar

  43. PTF beam splitter LeCroy Wavemaster 6 GHz Oscilloscope mirror Picosecond Test Facility featuring Undergraduate Laser Gang (UGLG) Undergraduate Laser Youths? (UGLY) filter MCP-PMT lenses laser Hamamatsu PLP-10 Laser Power Supply Laser Box Andrew Brandt SLAC Seminar

  44. Timing vs Gain for 10 m Tube Measured with reference tube using CFD’s and x100 mini-circuits amps, with 10 pe’s can operate at ~5E4 Gain (critical for reducing rate and lifetime issues) With further optimization have obtained <25 ps resolution for 10 pe’s.

  45. Timing vs. Number of PE’s No dependence of timing on gain if sufficient amplification!

  46. Transit Time Spread for Burle 64 Channel Planacon (10 m pores) • Jerry Va’vra has measured 32 ps for TTS (SLAC-PUB-13573) so we should have about 10 ps (32/10 for 10 pe’s! ) • This is true only if you ignore 2nd backscattering peak Andrew Brandt SLAC Seminar

  47. UTA Transit Time Spread for Burle 64 Channel Planacon (10 m pores) testing/modelling of response of PMT to late light and evolution of timing from one to several pe’s in progress

  48. Current/area for 10 m Tube Last 2 points are 0.4 and 2.0 μA/cm2; we need to reach about 3 μA/cm2 at 1034Photonis has made Planacon with 10x higher current capability which would meet our rate requirements (even with saturation we still obtain the same time resolution!!!) Andrew Brandt SLAC Seminar

  49. New Multi-Channel Laser Setup Andrew Brandt SLAC Seminar

  50. Rate Tests No rate dependence on number of pixels hit (that’s a good thing!) Andrew Brandt SLAC Seminar

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