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Forward Protons from the SPS to the LHC

Forward Protons from the SPS to the LHC. Andrew Brandt, University of Texas at Arlington. Thanks to Albert de Roeck, Brian Cox, Dino Goulianos, Mike Albrow, Michele Arneodo, Michael Strang, and others for slides DOE, NSF, UTA, Texas ARP for support. Physics Seminar Mar 2, 2006 SLAC.

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Forward Protons from the SPS to the LHC

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  1. Forward Protons from the SPS to the LHC Andrew Brandt, University of Texas at Arlington Thanks to Albert de Roeck, Brian Cox, Dino Goulianos, Mike Albrow, Michele Arneodo, Michael Strang, and others for slides DOE, NSF, UTA, Texas ARP for support Physics Seminar Mar 2, 2006 SLAC

  2. What is Diffraction? I P • Diffraction in high energy hadron physics encompasses those phenomena in which no quantum numbers are exchanged between interacting particles • Surviving particles have same quantum numbers as incident particles • Exchanging quanta of the vacuum is synonymous with Pomeron () exchange • Named after Russian physicist I.Y. Pomeranchuk • Virtual particle which carries no net charge, isospin, baryon number or color • Couples through internal structure • Signatures of diffraction include rapidity gaps (regions of the detector with no particles) and intact final state beam particle(s) which can be tagged with a forward proton detector

  3. Examples of Soft Diffraction Elastic Single Diffraction • Modeled by Regge Theory • Analysis of poles in the complex angular momentum plane give rise to trajectories that describe particle exchange • P.D.B. Collins, An Introduction to Regge Theory and High Energy Physics, Cambridge Univ. Press, Cambridge 1977 • Non-perturbative QCD

  4. Elastic Scattering • The particles after scattering are the same as the incident particles • The cross section can be written as: • This has the same form as light diffracting from a small absorbing disk, hence the name diffractive phenomena Elastic “dip” Structure from Phys. Rev. Lett. 54, 2180 (1985).

  5. Learning about the Pomeron • QCD is theory of strong interactions, but 40% of total cross section is attributable to Pomeron exchange -- not calculable and poorly understood • Does it have partonic structure? Soft? Hard? Super-hard? Quark? Gluon? Is it universal -- same in ep and ? Is it the same with and withoutjet production? • Answer questions in HEP tradition -- collide it with something that you understand to learn its structure • Note: variables of diffraction aret (momentum transfer) and x ~ M2 • (fractional momentum loss) with a proton detector measure • without one just measure s

  6. Ingelman-Schlein A* A P J2 X J1 B • Factorization allows us to look at the diffractive reaction as a two step process. Hadron A emits a Pomeron (pomeron flux) then partons in the Pomeron interact with hadron B. • The Pomeron to leading order is proposed to have a minimal structure of two gluons in order to have quantum numbers of the vacuum G. Ingelman and P. Schlein, Phys. Lett. B 152, 256 (1985)

  7. UA8

  8. UA8 = UA2 + Roman-pot Spectrometer

  9. UA8 Dijet Production in Diffraction A. Brandt et al., P.L. B 297 (1992) 417 (196 citations!) Hard Diffraction exists! Pomeron has a “super-hard” component. x(2-jet)

  10. Q2 = virtuality of photon = = (4-momentum exchanged at e vertex)2 t = (4-momentum exchanged at p vertex)2 typically: |t|<1 GeV2 W = invariant mass of photon-proton system xIP = fraction of proton’s momentum taken by Pomeron= x in Fermilab jargon b = Bjorken’s variable for the Pomeron = fraction of Pomeron’s momentum carried by struck quark e’ e Q2 e g* p Proton energy = 920 GeV Electron energy = 27.5 GeV s=318 GeV W X LRG IP p p’ t HERA ZEUS X e p 27.5 GeV e 920 GeV Dh s  320 GeV Diffractive Deep Inelastic Scattering

  11. VM, g, exclusive dijets…Higgs g* x x’ GPD p p Two fundamental physics quantities can be accessed in diffractive DIS: dPDFs and GPDs e’ 1) Diffractive PDFs: probability to find a parton of given x in the proton under condition that proton stays intact – sensitive to low-x partons in proton, complementary to standard PDFs (ingredient for all inclusive diffractive processes at Tevatron and LHC) e dPDF IP p p’ Rather than IP exchange: probe diffractive PDFs of proton • 2) Generalised Parton Distributions (GPD) • quantify correlations between parton • momenta in the proton; t-dependence • sensitive to parton distribution in • transverse plane • When x’=x, GPDs are proportional to the • square of the usual PDFs • (ingredient for all exclusive diffractive processes)

  12. xIPF2D(3) xIPF2D(3) Q2 b Positive scaling violations: lots of gluons ! Weak b dependence – not a “normal” hadron ! Diffractive Structure Function vs b, Q2

  13. F2D Extrapolation from HERA CDF data Applying dPDFs to FNAL/LHC Requires Care GPDs and diffractive PDFs measured at HERA cannot be used blindly in pp (or ppbar) interactions. In addition to the hard diffractive scattering, there are soft interactions among spectator partons. They fill the rapidity gap and reduce the rate of diffractive events. Multi-Pomeron-exchange effects (a.k.a. “renormalization”, “screening”,“shadowing”, “damping”, “absorption”)

  14. CDF Run 1-0 (1988-89) Elastic, single diffractive, and total cross sections @ 546 and 1800 GeV Roman Pot Spectrometers • Roman Pot Detectors • Scintillation trigger counters • Wire chamber • Double-sided silicon strip detector Additional Detectors Trackers up to |h| = 7 • Results • Total cross section stot ~ se • Elastic cross section ds/dt ~ exp[2a’ lns]  shrinking forward peak • Single diffraction Breakdown of Regge factorization

  15. SSC is a four letter word in Texas

  16. f Dh h h E   DØ Run I Gaps • Pioneered central gaps between jets: Color-Singlet fractions at s = 630 & 1800 GeV; Color-Singlet Dependence on Dh, ET, s (parton-x).PRL 72, 2332(1994); PRL 76, 734 (1996); • PLB 440, 189 (1998) • Observed forward gaps in jet events at s = 630 & 1800 GeV. Rates much smaller than expected from naïve Ingelman-Schlein model. Require a different normalization and significant soft component to describe data. Large fraction of proton momentum frequently involved in collision. • PLB 531, 52 (2002) • Observed W and Z boson events with gaps: measured fractions, properties first observation of diffractive Z. • PLB 574, 169 (2003) • Observed jet events with forward/backward • gaps at s = 630 and 1800 GeV

  17. Diffractive W Boson CDF {PRL 78 2698 (1997)} measured RW = 1.15 ± 0.55% where RW = Ratio of diffractive/non-diffractive W a significance of 3.8 DIFFW signal

  18. DØ Observation of Diffractive W/Z Diffractive W and Z Boson Signals • Phys. Lett. B 574, 169 (2003) • Observed clear Diffractively produced W and Zbosonsignals • Events have typical W/Z characteristics • Background from fake W/Z gives negligible change in gap fractions nL0 ncal nL0 ncal Central electron W Forward electron W Sample Diffractive Probability Background All Fluctuates to Data Central W (1.08 + 0.19 - 0.17)% 7.7s Forward W (0.64 + 0.18 - 0.16)% 5.3s All W(0.89 + 0.19 – 0.17)% 7.5s All Z (1.44 + 0.61 - 0.52)% 4.4s nL0 ncal All Z

  19. DØ Run II Diffractive Topics Soft Diffraction and Elastic Scattering: Inclusive Single Diffraction Elastic scattering (t dependence) Inclusive double pomeron Search for glueballs/exotics Hard Diffraction: Diffractive jet Diffractive b,c ,t Diffractive W/Z Diffractive photon Other hard diffractive topics Double Pomeron + jets Other Hard Double Pomeron topics Exclusive Production of Dijets Topics in RED were studied with gaps only in Run I

  20. DØ Forward Proton Detector Nine independent spectrometers each consisting of two detectors Scattered antiprotons Scattered Protons AUP Spectrometer PUP Spectrometer Dipole Magnets Quadrupole Magnets Quadrupole Magnets Separator Separator z [m] Dipole Spectrometer IP ADOWN Spectrometer PDOWN Spectrometer  Reconstruct particle tracks from detector (scintillating fiber) hits Dipole SpectrometerQuadrupole Spectrometers |t| ~ 0.0 GeV2 |t| > 0.8 GeV2 x > 0.04 x > 0.0  18 Pots integrated into DØ readout and inserted every store since Jan 2004 Simultaneously tag/reconstruct protons and antiprotons

  21. FPD Castles/Detectors • All 6 castles with 18 Roman pots comprising the FPD were constructed in Brazil, • installed in the Tevatron in fall of 2000, and have been functioning as designed. • 20 detectors built over a 2+ year period at UTA • In 2001-2002, 10 of the 18 Roman pots were instrumented with detectors. • During the fall 2003 shutdown the final eight detectors and associated readout • electronics were installed. A2 Quadrupole castle with all four detectors installed

  22. FPD Detectors • 6 planes per detector in 3 frames and a trigger scintillator • U and V at 45 degrees to X, 90 degrees to each other • U and V planes have 20 fibers, X planes have 16 fibers • Planes in a frame offset by ~2/3 fiber • Each channel filled with four fibers • 2 detectors in a spectrometer 17.39 mm V’ V Trigger X’ X U’ U 17.39 mm 1 mm 0.8 mm 3.2 mm

  23. Diffractive Z Production Event Selection:Z→μ+μ- Events Two Good (PT > 15GeV) Oppositely Charged Tracks Both Identified as muons BKGD Rejection: Min one muon Isolated in Tracker and Calorimeter (suppress Heavy Flavour BKGD), Cosmic Ray Rejection. Demand Activity North and South Forward Gap (North or South) DØ Prelim DØ Prelim Candidate Diffractive Z Events

  24. Large * Store Large * Two day run of accelerator at injection tune *=1.6 m 1x1 bunch Lum=0.5E30 • Physics Goals: • Low-t elastic scattering • Low-t single diffractive • and double pomeron • scattering

  25. Hit Maps from 1x1 Store Large b* store (4647) (no low b squeeze) Typical Store

  26. FP420 Joint ATLAS/CMS R&D project with 58 members from 11 countries Spokespersons : B.Cox (Manchester), A. DeRoeck (CERN) Technical Co-ordinator : C. DaVia (Brunel) Management Committee : A. Brandt (UTA), Mike Albrow (FNAL), M. Arneodo (Turin / INFN), K. Piotrzkowski (Louvain), R. Orava (Helsinki) LHC Interface: Keith Potter (CERN) will join Manchester / Cockcroft Inst. LOI submitted to the LHCC 6/05:CERN-LHCC-2005-025; LHCC-I-015 FP420 : An R&D Proposal to Investigate the Feasibility of Installing Proton Tagging Detectors in the 420m Region at LHC From the LHCC minutes : The LHCC heard a report from the FP420 referee. In its Letter of Intent,the FP420 Collaboration puts forward an R&D proposal to investigate the feasibility of installing proton tagging detectors in the 420 m region at the LHC. By tagging both outgoing protons at 420 m a varied QCD,electroweak, Higgs and Beyond the Standard Model physics programme becomes accessible. A prerequisite for the FP420 project is to assess the feasibility of replacing the 420 m interconnection cryostat to facilitate access to the beam pipes and therefore allow proton tagging detectors to be installed. The LHCC acknowledges the scientific merit of the FP420 physics programme and the interest in its exploring its feasibility.

  27. NEW 0++ Selection rule QCD Background ~ FP420 Overview FP420: Double proton tagging at 420m as a means to discover new physics • Tagging the protons means excellent mass resolution (~ 1 to few GeV) independent of decay channel • Selection rules mean that central system is dominantly 0++ (CP even) • If you see a new particle in any decay channel with proton tags, you know its quantum numbers • CP violation in the couplings shows up directly as an azimuthal asymmetry in the tagged protons • Proton tagging may be THE discovery channel in certain regions of the MSSM Used to be called Double Pomeron Exchange now Central Exclusive Diffraction

  28. -jet gap gap H h p p -jet beam dipole dipole p’ p’ roman pots roman pots Central Exclusive Higgs Production 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… Idea: M. Albrow & A. Rostovtsev forTevatron M = O(1.0 - 2.0) GeV

  29. Higgs Acceptance vs. Mass (MH) 220m RP Helsinki Group study for TOTEM and FP420 Model Dependence! Need HERA and/or Tevatron to referee Otherwhise wait for LHC data Low *: (0.5m): Lumi 1033-1034cm-2s-1 220m: 0.02 <  < 0.2 400m: 0.002 <  < 0.02 RPs in the cold region/FP420 are needed to access the low  values

  30. 420-220 ATLAS CMS 420-420 Latest Acceptance + Resolution 420-420 P. Bussey / A. Pilkington / J. Monk

  31. Central Exclusive Higgs Production Standard Model Higgs b jets : MH = 120 GeV s = 2 fb (uncertainty factor ~ 2.5) MH = 140 GeV s = 0.7 fb MH = 120 GeV :11 signal / O(10) background in 30 fb-1 with detector cuts H H WW* : MH = 120 GeV s = 0.4 fb MH = 140 GeV s = 1 fb MH = 140 GeV :8 signal / O(3) background in 30 fb-1 with detector cuts • The b jet channel is possible, with a good understanding of detectors and clever level 1 trigger (need trigger from the central detector at Level-1) • The WW* (ZZ*) channel is extremely promising : no trigger problems, better mass resolution at higher masses (even in leptonic / semi-leptonic channel) • If we see SM Higgs + tags - the quantum numbers are 0++ See e.g. J. Forshaw HERA/LHC workshop

  32. Higgs Studies 100 fb 1fb 120 140 Cross section factor ~ 10-20 larger in MSSM (high tan) Kaidalov et al., hep-ph/0307064 Study correlations between the outgoing protons to analyze the spin-parity structure of the produced boson A way to get information on the spin of the Higgs ADDED VALUE TO LHC

  33. Lineshape Analysis J. Ellis et al. hep-ph/0502251 Scenario with CP violation in the Higgs sector and tri-mixing

  34. CDF Exclusive Dijets in Run I Dijet Mass fraction PRL 85 (2000) 4215 Expected shape of signal events Exclusive dijet limit: sjj (excl.) < 3.7 nb (95% CL) Theoretical expectation (KMR) ~1 nb

  35. CDF Exclusive Dijets in Run II exclusive?

  36. CDF Exclusive Di-photons in Run II The e+e- and 2-photon events are interpreted as completely different processes: QCD + QED : QED : + soft gluon exchange, Sudakov effect Monte Carlo: LPAIR Expect 9 +- 3 events 10 candidates Monte Carlo: ExHume (Durham) Expect 1 (+ 3,-0.7) events 3 candidates

  37. DØExclusive Dijets in Run II

  38. Key Components of FP420 • Space in LHC tunnel for detectors (cryostat mods) • Edgeless silicon detector • Trigger and readout • “Roman pot” mechanics to house and move detector • Fast TOF detector Not discussed here UTA Focus

  39. Connection Cryostat IP1/5 124.5 mm 420 m CONNECTION CRYOSTAT Consists of 15 m long drift space Provides a continuity of beam and insulation vacuum, electrical powering, cryogenic circuits, thermal and radiation shielding Provides connection between the arcs and DS zones

  40. Diagram S. Marque / D. Dattola FP420 09/11/2005 FP420 Cryostat UK funding initiative (Manchester et al) supporting Cockcroft Institute engineer at CERN to design new cryostat IP 1/5 Cold warm transitions Usable Volume for Detectors No more than 8m warm region

  41. 3D Silicon NIMA 395 (1997) 328 IEEE Trans Nucl Sci 464 (1999) 1224 IEEE Trans Nucl Sci 482 (2001) 189 IEEE Trans Nucl Sci 485 (2001) 1629 IEEE Trans Nucl Sci 48 6 (2001) 2405 CERN Courier, Vol 43, Jan 2003, pp 23-26 NIMA 509 (2003)86-91 3D silicon detectors were proposed in 1995 by S. Parker, and active edges in 1997 by C. Kenney. Combine traditional VLSI processing and MEMS (Micro Electro Mechanical Systems) technology. Electrodes are processed inside the detector bulk instead of being implanted on the Wafer's surface. The edge is an electrode! Dead volume at the Edge < 2 microns! Essential for -Large area coverage -Forward physics

  42. The LONGPOT Concept (Helsinki) Proton Beam Emergency Stops Tilt 13º Stepper Motor Bellows Outer Weld Points Beam Pipe Flange Primary Vacuum Detector Detector movement Detector Pocket CWT (optional) Rest Stops Secondary Vacuum Feedthroughs UTA collaborating with Helsinki

  43. Hamburg Pipe Routinely used at HERA at high L, since 1995… : bellows moving pipe

  44. Hamburg Pipe Working position Bellows Detectors a few m apart For FP420 some modifications needed such as RF shield (through which the detectors approach the beam via narrow slots), to minimise any impedance change on the beam. Parking position RF screen

  45. It’s been done! Fast TOF Can’t put our PMT in 7 TeV beam!

  46. QUARTIC proton  Preliminary UTA drawing of Mike Albrow’s concept for a fast time resolution Cerenkov counter: Initial design used 2 mm2 rods, but not enough light, this drawing shows 6mm2 rods z (mm) =0.21 t (psec) (2.1 mm for t=10 psec) z=c(TR-TL)/2 Microchannel plate PMT

  47. QUARTIC Background Rejection (UTA) • 2 single diffractive protons overlayed with a hard scatter (1% of • interactions have a proton at 420m) 97.4% of events primary vertex and fake vertex from combining proton times more than 2.1mm (1) apart ; 94.8% if 20 psec 2) double pomeron overlayed with a hard scatter 97.8% of time vertices more than 2.1mm apart; 95.6% if 20 psec 3) hard SD overlayed with a soft SD 95.5% of time primary vertex and fake vertex more than 2.1mm apart; 91.0% if 20 psec

  48. Preliminary Time Distributions (UTA): Single  n=1.52 c=49; 7.4% of pe’s in 10 psec 21.3% in 50 psec red= totally internally reflected light green = extra light if aluminized 0.01 • over  including QE 1.9% of pe’s in 10 psec 19.1% in 50 psec 0.01 50 psec Alberta working on GEANT simulations; we plan to use FNAL test beam in summer 50 psec

  49. FP420 Summary: • If you have a sample of Higgs candidates, triggered by any means, accompanied by proton tags, it is a 0++ state. • WW delivers sensitivity to anomalous couplings a factor of 10,000 better than LEP II • In certain regions of MSSM parameter space, S/B > 20, and double tagging is THE discovery channel • In other regions of MSSM parameter space, explicit CP violation in the Higgs sector shows up as e.g. azimuthal asymmetry in the tagged protons -> direct probe of CP structure of Higgs sector at LHC • “Exclusive double diffraction may offer unique possibilities for exploring Higgs physics in ways that would be difficult or even impossible in inclusive Higgs production” J. Ellis et. al. • The big design issues : Installation at 420m (cryogenics + vacuum) • Safe operation within LHC collimation scheme • Funding Email brandta@uta.edu or spokes if interested

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