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Exploring Central Exclusive Production in Particle Collisions

Delve into the phenomenon of Central Exclusive Production at the Tevatron and LHC, measuring simple systems like π+π- and more. This study, led by Mike Albrow at Fermilab, showcases first 2-photon measurements in hadron collisions, testing production mechanisms and calibration techniques. Compare Higgs studies through p+H+p, WW, and ZZ with FP420 R&D project for ATLAS & CMS extensions. Discover the clean environment of CDF Central Exclusive Production, emphasizing Higgs characteristics and possible collider applications across various machines. Uncover the detailed processes and outcomes of Central Exclusive Production in different particle collision scenarios, offering insights into new physics discoveries.

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Exploring Central Exclusive Production in Particle Collisions

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  1. Central Exclusive Production at the Tevatron (CDF) Mike Albrow (Fermilab) for the CDF Collaboration pp  p X p where X is a simple system completely measured VeryFewParticle Introduction ISR : π+ π- etc. Tevatron: e+e-, γγ, μ+μ-, J/ψ, ψ(2S), χ_c, Υ …. Z? LHC: Z, H, W+W-, … JJ

  2. ISR – Tevatron -- LHC p p p p G? H? p p p p • Central Exclusive Production: • LHC: Study of Higgs through p + H + p, WW and ZZ + + + • FP420: R&D project; proposing extensions to ATLAS & CMS. Our measurements are the first 2-photon in hadron-hadron, and test both the production mechanisms and calibration techniques. ~ same diagram

  3. Central Exclusive Production in Different Machines In collisions (through LEP energies  I L C) :  hadrons, and at high energy: WW  WW, WW  Z,H ; WZ  W In ep collisions (HERA) : gamma-IP  vector mesons ( too but buried?) In (ISR  Tevatron and LHC) : IP IP  hadrons (can be single hadron), Higgs, -IP  vector mesons (.. ,Y, Z(allowed but tiny))  l+l- ( too but buried?) In AA (RHIC, LHC) mainly (E-fields) -IP and IP+IP New in CDF

  4. Central Exclusive Production is very clean, ~ no backgrounds p ~ -7.4 ~ 7.4 |y| < 1 Rapidity y p With rapidity gaps > 6 on both sides, t-channel exchanges are very limited: Charge Q = 0, No color, and spin J >= 1.0 Allowed exchanges: only photons, IP = pomeron {~gg} Odderon {~ggg} not yet observed, Z (but p would always break up!) t only from IP, OIP(?) only from , continuum. only from IPIP.

  5. Central Exclusive Production of Higgs Higgs has vacuum quantum numbers, vacuum has Higgs field. So pp  p+H+p is possible. Allowed states: Process is gg  H through t-loop as usual with another g-exchange to cancel color and even leave p’s in ground state. If measure p’s: J >= 2 strongly suppressed at small p angle (t) t H 4-vectors ! MGA+Rostovtsev: hep-ph/0009336 Aim: be limited by incoming beam momentum spread

  6. Central Exclusive Production at ISR = 63 GeV (AFS) Axial Field Spectrometer (R807) Added very forward drift chambers D.P.E. & Search for “Glueballs” p p data ALSO 3500 events/25 MeV G(1710)?? Structures not well understood beyond f(980) Not studied at higher DPE  would be great for G-spectroscopy. Waiting to be done at Tevatron! Student?

  7. CDF Detector at Fermilab Tevatron Muon Chambers Calorimeters MiniPlugs 980 GeV pbar 980 GeV p

  8. Installed very forward Beam Shower Counters (BSC) for rapidity gaps and scintillating fiber trackers in Roman pots for pbar detection Not at all to scale! Roman pot detectors 20mm x 20mm 55 m downstream. Beam Shower Counters BSC tight around pipe. Full coverage –7.4 < < +7.4 by beam shower counters In this talk I do not use Roman pots; do not have acceptance for low mass

  9. Exclusive Electron-Positron Production in Hadron Collisions (CDF) Phys.Rev.Lett 98,112001(2007) 16 events QED process : collisions in pp Monte Carlos : LPAIR, GRAPE, STARLIGHT

  10. Exclusive H Theory Calibration: Exclusive 2-Photon MGA et al. (2001) hep-ex/0511057 Khoze, Martin and Ryskin, hep-ph/0111078, Eur.Phys.J. C23: 311 (2002) KMR+Stirling hep-ph/0409037 QCD diagram identical to pHp Tevatron 36 fb Claim factor ~ 3 uncertainty ; Correlated to p+H+p

  11. Exclusive Production in Hadron-Hadron Collisions Phys.Rev.Lett. 99,242002 (2007) 3 candidates observed: s Prediction V.A.Khoze et al. Eur. Phys. J C38, 475 (2005) (our cuts) = (36 +72 – 24) fb = 0.8 +1.6 –0.5 events. Cannot yet claim “discovery” as b/g study a posteriori, 2 events corresponds to ~ 90 fb, agreeing with Khoze et al. ExHuME Monte Carlo James Monk & Andy Pilkington (MCR) It means exclusive H must happen (if H exists) and probably ~ 5 fb within factor ~ 3. is higher in MSSM

  12. New Results, hot off the press: Region rich in physics. First observations in (elastic) hadron-hadron: 1) 2) 3) 1 & 2 ) Forward proton momenta precisely known: calibrate momentum scale of forward spectrometers for p + p  p + H + p at LHC. 3) Calibrate theory (x-sn) of p + H + p

  13. There are 4, maybe 5, physics processes in this data! IP = pomeron • 2-photon (QED) production of the continuum (no resonances) • We published this in 2007 for e+e- [ee] with M > 10 GeV(16 events as in QED) • Photon + IP  … photoproduction, as in ep at HERA • Photon + IP  … photoproduction, as in ep at HERA • IP + IP  or 1) 2,3) 4)

  14. Data: Feb 2002 – March 2007 Luminosity (Good Runs) = 1.48/fb (+/- 6%) Trigger = muon + track +BSC1 gaps  2 muons Number of events on tape: ~ 1.6 million ) Reject cosmic ray events (ToF, colinearity) … 100% efficient Exclusivity: Require all detectors < noise cuts except in mumu direction

  15. Exclusivity cuts Want to be sure no other particles were produced. Take 0-bias = bunch crossing data. Put in two classes: non-interaction (dominated), no tracks, no CLC hits, no muon stubs interaction (dominated), all others For each sub-detector: 5 calorimeter regions, 3 BSC counter hodoscopes Find largest signal and plot it as [Log_10 max ADC counts] We did this for each of (11) periods of data, finding cut efficient at selecting “nothing” i.e. noise thresholds. Red mini-peak is not ineffiency, mainly mini-gaps with no pile-up. 500 ADC counts

  16. 36 bunch x bunch crossings Have different luminosities Distribution over a “period” Exclusive efficiency Exclusive efficiency x L(bunch) Integral = L_1(effective) – no PU Eff(excl) = 0.093 , 1.48/fb  (139 +/- 8) /pb (6%)

  17. Single muon acceptance > 90% for pT > 1.5 GeV. Lower pT range out in calorimeters Very well fit by empirical function: F = 0.1 at M = 3.05 F = 0.6 asymptotically

  18. 402 events Fit: 2 Gaussians + QED continuum. Masses 3.09, 3.68 GeV == PDG Widths 15.8,16.7 MeV=resolution. QED = generator x acceptance 3 amplitudes floating Paper in preparation

  19. x QED spectrum ~ Only normalization A floating STARLIGHT & LPAIR MCs Good description: v.low pT

  20. photoproduction (or possible odderon exchange) Kinematics well described by STARLIGHT MC Much broader pT,dphi than

  21. photoproduction (or possible odderon exchange) Kinematics well described by STARLIGHT MC Much broader pT,dphi than

  22. Dissociation background: Take (90 +/- 10%) for eff (BSC) (10 +/- 3)% Indication of small non-exclusive b/g as not described by MC Non-exclusive correction: QED: 0.91 +/- 0.05 J/psi, psi’ 0.97 +/- 0.03

  23. Exclusive (<80 MeV) Best fit is with ~ 1/3 but with very large uncertainty Interpretations: (1) Large component (not supported by Method 2) (2) Decay simulations not precise (3) 1.5 sigma fluctuation (4) An odderon component (also  larger )

  24. Events with EM shower Good fits to mumu kinematics with only chi_c’s, if EM shower

  25. EmEt spectrum with J/psi mass cut: Empirical functional form: Fit shown (ET in MeV): A = 0.00025 B = 2.5 C = 0.0125 (per MeV) Fraction under 80 MeV small: 2.8 below 80 MeV (1% of J/psi) From varying A,B,C (1 +/- 1)% &  # chi_c = 68 +/- 8 Combine (1) and (2) : f = (1.9 +2.8 -1.9) % Total number of chi_c = 68.2 (65.2 are above 80 MeV cut)

  26. Run,Evt: 220182.13272933 M=3.101, pT=1.54, dphi=2.18 CENTRAL DRIFT CHAMBER CALORIMETERS: LEGO PLOT BSC empty CLC W empty CLC E empty Note: CLC and BSC all empty although we did not require that.

  27. Summary of Results

  28. Summary of Results Assumed Suppressed by J_z=0 rule

  29. Search for Odderon exchange Odderon O, C = -1 partner to IP … at least 3 gluons In QCD but not yet observed. Possibly O + IP  & Signature: Excess of exclusive & and Upsilons Y over rate expected from photoproduction (tuned to HERA data). t(p)-distribution would be flatter and hence VM should have larger <pT> and Kinematic behavior different, but not well known. not known

  30. Some predictions for J/psi photoproduction: e.g. Schafer and Szczurek: arXiv:0705.2887 [hep-ph] Machado,Goncalves 3.0 nb Khoze, Martin, Ryskin Motyka and Watt: 3.4 nb Schafer & Szczurek ~ 2.8 nb Nystrand 2.2 nb Our result: 3.96 +- 0.64 nb Machado is considered too high by KMR Take 3.0 +- 0.8 We are consistent, & so we can put a limit on odderon exchange. If theory gets more precise, our limit can change

  31. Odderon Limits and ratios

  32. Invariant Mass Distribution- Upsilon Region Trigger: μ+μ- |η|<0.6 , pT(μ) > 4 GeV/c CDF Run II Preliminary Inclusive Photo-production of Y, Y’ (first observation in hadron-hadron) Y(1S) Invariant Mass (nassoc_tracks = 0) pT(μμ) < 6GeV/c CDF Run II Preliminary Y(2S)

  33. Exclusive Upsilon(1S) candidateRun/Event: 204413/8549136 M ~ 9.4 GeV R-z, Muon hits Lego, threshold ET > 10 MeV Plugs, Miniplugs, CLC, BSC empty

  34. Search for Exclusive Z, and observe high mass lepton pairs. Spectrum extends to M(ll) > 100 GeV! We have observed a candidate exclusive event with M ~ 64 GeV, which appears to be exclusive. Run 166529 Event 10107956 Forward counters both sides CLC and BSC were empty. Roman pot had pbar track This is exactly the type of event for calibrating p(FP420)

  35. FP420 : Forward Protons 420m downstream of CMS & ATLAS CMS: Inner Vacuum Tank insertion CMS ||| ||| ||| ||| 420 & 220m 220 & 420m ATLAS

  36. Summary We have observed the following exclusive states X in p + X + p at the Tevatron with CDF: These are all “first observations” for hadron-hadron “elastic”. (unless you call {A,Z} a hadron) processes agree with QED predictions Photoproduction of V agree with expectations & HERA. Hence limit on odderon exchange, near theory. IP+IP  within theoretical uncertainties, and demonstrates that exclusive H should happen, if H. Furthermore, exclusive di-leptons provide a calibration of forward p – spectrometers, momentum scale and resolution

  37. BACK UPS

  38. Cosmic rays would be at 0

  39. What is exclusive H cross section? Calculation involves: gg  H (perturbative, standard, NLO) Unintegrated gluon densities Prob.(no other parton interaction) (“Gap survival”) Proton form factor Prob.(no gluon radiation  no hadrons) Sudakov Suppression H ~ 3 fb (M(H)=125 GeV) “factor ~ 3 uncertainty” 30 fb^-1  ~ 100 Ae events (Ae = acceptance, efficiency) But other estimates differ by “large” amounts! Need to “calibrate” theory! Exclusive Durham Gp: Khoze, Martin, Ryskin, Stirling hep-ph/0505240 ++

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