1 / 28

Central Exclusive Production in CDF Mike Albrow, Fermilab

Central Exclusive Production in CDF Mike Albrow, Fermilab. Search for. e+e- Mass 10 – 40 GeV , and γγ … not new, a brief reminder μ + μ - Mass 3 - 4 GeV, J/ ψ , ψ (2S) →μ + μ -, χ c → J/ ψ + γ (PRL’09) e+e- and μ + μ - Mass 40 – 100 GeV, and Exclusive Z search (PRL’09)

purity
Download Presentation

Central Exclusive Production in CDF Mike Albrow, Fermilab

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Central Exclusive Production in CDF Mike Albrow, Fermilab Search for e+e- Mass 10 – 40 GeV , and γγ … not new, a brief reminder μ+μ- Mass 3 - 4 GeV, J/ψ, ψ(2S) →μ+μ-, χc→J/ψ + γ(PRL’09) e+e- and μ+μ- Mass 40 – 100 GeV, and Exclusive Z search (PRL’09) μ+μ- Mass 8 – 40+ GeV, Upsilons Y photoproduction, χb ?(search) γγ Mass 5 – ? GeV, search in progress

  2. Introduction Central Exclusive Production where X is a simple state fully measured, and no other particles produced. (In CDF cannot detect p/pbar, down beam pipe, but BSC → η = 7.4 empty) (& VM: J/ψ,ψ’,Υ) X Motivation: In CDF, sophisticated tests of QCD with large rapidity gaps Δy Looking forward to LHC: Interesting LHC examples  If see h, H : Mass, width, spin J, C = +1, Couplings Γ(Hgg), … in a unique way, even if e.g.

  3. A bit of history. LOI to FNAL PAC: Pile-up reduction: Quartz + MCP-PMT hep-ex/0511057 It was great! So why was it not pursued? Most people thought it was hopeless … and they were right! (for Tevatron … but not for LHC!)

  4. p+p  p + H + p cross sections σ(p+H+p) was uncertain (to a simple experimenter) by a factor > 1000 in 2000 We absolutely needed some experimental input to home in on what to expect! * * * * Now measured in CDF

  5. Cleanest (no S.I.) but smallest σ KMR: 38 pb in our box). Found 2+1 candidates Clean, big σ: but M(c) small (non-pert) & hadron More perturbative, smaller theory uncertainty But σ ~ 1/500thχc. Also BR’s not known! Big cross section, but least well defined (jets!) and largest background. ~ 100 pb for M(JJ) > 30 GeV ISR did it … but it is not perturbative (IP+IP→ f/σ→π+π-) Our 3 measurements are all in good agreement (factor “few”) with the Durham group predictions.

  6. CDF Forward Detectors: MINIPLUG BSC 1 BSC 2,3,4 CLC Cherenkov Luminosity Counters BSC very important as rap gap detectors.

  7. Photon “beams” radiated from electrons and protons LEP etc: e+e- (~ background free) HERA: e p (more background, little γγdone) pp/ ppbar: Very high b/g … Seen in CDF e,p γ Tevatron as a  collider! PRL 102, 222002 (2009) PRL 102, 242001 (2009) PRL 98,112001(2007) dφ 180-dφ

  8. All our dilepton measurements agree with QED: So what? • It shows we know how to select rare exclusive • events in hadron-hadron environment • No other h-h cross section is so well known • theoretically except Coulomb elastic. • Possibly excellent Luminosity calibration at LHC e.g. • Outgoing p-momenta extremely well-known • (limited by beam spread). Calibrate forward proton spectrometers. • Practice for other γγ collisions at LHC: Luminosity calibration at LHC Cannot veto pile-up! Testing now in CDF M(μ+μ-) > 8 GeV/c2

  9. We set out to measure exclusive c  J/ψ + →μ+μ-  μ+ J/ψ μ- c γ & nothing else in all CDF -7.4 < |η| < + 7.4 Beam Shower Counters BSC: If these are all empty, p and p did not dissociate (or BSC inefficient, estimated from data) but went down beam pipe with small (<~ 1 GeV/c) transverse momentum. Plan to put these (FSC) with CMS - 50 m CDF central BSC 9

  10. Exclusive production c has small pT, and so do muons: Trigger = 2 muons + BSC1 veto. pT(μ) >~ 1.4 GeV to penetrate calorimetry. M(μμ) <~ 4 GeV imposed by trigger rate (no prescale) Offline required μ+μ- or μ+μ- and nothing else. Found that most μ+μ- had no photon (EM shower). Example: BSC1 (8 PMTs) 5.4 < |η| < 5.9 Hottest PMT (no int/int) Exclusive requirement: c 500 100 1000 counts

  11. arXiv:0902.1271 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 p p

  12. Now allow photons: EmEt spectrum with J/ψ mass cut: Empirical functional form • 65 events above 80 MeV cut. • 3 events below (estimated from fit) • 4% background under J/psi • # = 65 +/- 8 MC also estimates only few % of under the cut E(EmEt) resolution, very low energy photons, does not allow separation of different χc states, but data are consistent with χc (3415).

  13. Events with EM shower Good fits to kinematics with only , if EM shower No photoproduced ψ’(2S) with EM shower > 80 MeV Confirms assignment New MC: SuperCHIC (Lucien Harland-Lang & Durham) to use.

  14. Summary of Results M = 3-4 GeV/c2 90 nb (χ width) Durham No strong evidence for odderon Oops: PRL table (not text) says 27 +- 0.5 <pT> also

  15. Khoze, Martin and Ryskin, Eur.Phys.J. C23: 311 (2002) ; KMR+Stirling hep-ph/0409037 Claim factor ~ 3 uncertainty ; Correlated to p+H+p 36 fb H 3 candidates, 2 golden, 1 ? ? 36 fb  0.8 events New data, Lower threshold, possible “observation” to come(?) & SuperCHIC !

  16. Exclusive Z production is possible but SM cross section much to small to see at Tevatron. Detection would imply BSM physics. E.g. Alan White’s critical pomeron predicts “much enhanced” cross section … so we look.

  17. M(ee) = 49.3 GeV/c2 |Δφ-π| = 6 mrad = 0.34 deg, pT(ee) = 210 MeV E not ET! 82 < M < 98 GeV M reach at Tevatron to 75 GeV/c2 >~ HERA, LEP ! At LHC will be 100’s of GeV.

  18. Before requiring BSC empty (no dissociation): 8 pairs Probably a Z, but not exclusive. (SC) Dissociation? not like QED γγ One event has a Roman pot pbar track, others had pbar out of acceptance or Roman pots off. Agrees with LPAIR/QED in shape as well as normalization. All pairs back-to-back in Ø within 0.8 degrees!

  19. Exclusive Z limit: Combining e+e- and μ+μ- 0 candidates 0.66±0.11 background α.BR(ll).Leff = 3.22±0.38 pb-1 σ(Zexcl) < 0.96 pb @ 95% CL COOL! (960 fb) Predictions: Standard Model: Motyka and Watt, PRD 78, 014023 (2008) : σ(Z,excl) = 0.3 fb Goncalves and Machado, Eur.Phys.J. C 56, 33 (2008) : σ(Z,excl) = 0.21 fb Beyond Standard Model (Color sextet quarks): A.R.White, PRD 72, 036007 (2005): “much bigger” at LHC! Have 3 x more data. If allow pile-up get another factor x 5, but more background. (Not being actively looked at.) At LHC SM predictions ~ fb and may be just in reach!

  20. Dimuons: Upsilon Region CDF Run II Preliminary Trigger: μ+μ- |η|<0.6 , pT(μ) > 4 GeV/c Inclusive Search for/measurement of photoproduction of Y(1S),Y(2S),Y(3S) (not before seen in hadron-hadron) Invariant Mass 0 associated tracks pT(μμ) < 1.5 GeV/c CDF Run II Preliminary Y(1S) Status: analysis in progress. QED continuum check, but kinematics better constrained. Y : cf HERA (we resolve states) Can we see ? At most a few events, but BR’s not known. Only “existence proof” (& not yet). Y(2S) Y(3S)

  21. Exclusive Upsilon Y(1S) candidateRun/Event: 204413/8549136 M ~ 9.4 GeV R-z, Muon hits Plugs, Miniplugs, CLC, BSC empty

  22. e.g. A. Szczurek: arXiv:0811.2488 ~ 30 pb

  23. Rate for Y @ LHC: at Tevatron and LHC predictions down by 1.45 (pdg width change) • Will not get good Y cross sections without knowing , and p-calibration is screwed up. “Soft” photons important. Use only QED μ+μ- for calibrations

  24. Exclusive Di-Jets Phys Rev D77:052004 (2008) J GAP J JET Observed in CDF, QCD tests & related to p+H+p JET “Almost” exclusive di-jet, Two jets and nothing else Interesting QCD: gap survival, Sudakov factor Nearly all jets should be gg …. qq suppressed by M(q)/M(JJ) (Jz=0 rule) Gluon jet physics.

  25. Central Exclusive Production (DPE) of hadrons Not studied at (ISR) Higher energy is better, larger Δy ( > 5 at Tevatron) CDF + the Tevatron is the best place in the World for this physics (including LHC) Establishing the spectroscopy of scalar and tensor states is one program. But there’s much more! @ ISR Produced in pure CP-even state. In e+e- (and φ-decay) pure CP-odd Can be done (technically) in CDF without detecting forward protons (use rapidity gaps). Cross sections large (10’s μb) : L1 trigger being tested. If promising, 14 hours, end store, low L, dedicated run ( 10 million events, mostly high mass).

  26. Summary • Programme in CDF to measure central exclusive processes • As interesting QCD physics in its own right • but especially in a Tev-4-LHC spirit and to understand FP420/240 issues • Measurements have demonstrated that p + H + p must happen (if H exists) • and that cross section probably ~ 1 - 10 fb (KMR) • c) Measurements have demonstrated that γγ→ ee, μμ could be used in a • hadron-hadron collider to calibrate forward spectrometers I covered: { } = no observation yet our star reaction!

  27. Thank You

  28. Large ( >~4) rapidity gaps only possible by (t) exchange of 4-momentum with: No color or charge, and effective spin at t ~ 0 >= 1. J = 1, α(0) >=1. But (a) we have such large gaps in strong interactions (b) QCD is THE theory of strong interactions. Unlike QED γ, there is no elementary (q,g) object with these properties. (c) In QCD, with Regge theory to describe exchanges of states in the t-channel, only >= 2 g exchange can work. Pomeron, IP Many ingredients to QCD calculation: 1) gg → X through q-loop 2) A color-cancelling g exchange {g(x1,x2)} 3) No gluon radiation → hadron production 4) No other parton-parton interaction. q calculable but with large uncertainties Measuring one constrains the others.

More Related