1. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 1 Central Exclusive Production in CDF Mike Albrow, Fermilab 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) μ+μ- Mass 8 – 40+ GeV, Upsilons Y photoproduction, χ b ?(search) γγ Mass 5 – ? GeV, search in progress Search for

2. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 2 Introduction 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) 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. Central Exclusive Production (& VM: J/ψ,ψ’,Υ) X

3. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 3 A bit of history. LOI to FNAL PAC: 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!) hep-ex/0511057 Pile-up reduction: Quartz + MCP-PMT

4. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 4 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 * * * p+p  p + H + p cross sections

5. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 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 ~ 1/500 th χ c. Also BR’s not known! Big cross section, but least well defined (jets!) and largest background. ~ 100 pb for M(JJ) > 30 GeV Our 3 measurements are all in good agreement (factor “few”) with the Durham group predictions. ISR did it … but it is not perturbative (IP+IP→ f/σ → π+π-)

6. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 6 CDF Forward Detectors: BSC 1 BSC 2,3,4 CLC Cherenkov Luminosity Counters MINIPLUG BSC very important as rap gap detectors.

7. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 7 Photon “beams” radiated from electrons and protons LEP etc: e+e- (~ background free) HERA: e p (more background, little γγ done) pp/ ppbar: Very high b/g … Seen in CDF γ e,p PRL 98,112001(2007)PRL 102, 242001 (2009) Tevatron as a  collider! PRL 102, 222002 (2009) dφdφ 180-dφ

8. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 8 All our dilepton measurements agree with QED: So what? 1)It shows we know how to select rare exclusive events in hadron-hadron environment 2)No other h-h cross section is so well known theoretically except Coulomb elastic. Possibly excellent Luminosity calibration at LHC e.g. 3)Outgoing p-momenta extremely well-known (limited by beam spread). Calibrate forward proton spectrometers. 4)Practice for other γγ collisions at LHC: Luminosity calibration at LHC Cannot veto pile-up! Testing now in CDF M(μ+μ-) > 8 GeV/c 2

9. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 9 9 c J/ψ γ μ+μ+ μ-μ- & 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. CDF central BSC - 50 m We set out to measure exclusive  c  J/ψ +  → μ+μ-  Plan to put these (FSC) with CMS

10. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 10  c has small p T, and so do muons: Trigger = 2 muons + BSC1 veto. p T (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). 500 1001000 counts Example: BSC1 (8 PMTs) 5.4 < |η| < 5.9 Hottest PMT (no int/int) c Exclusive production Exclusive requirement:

11. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 11 arXiv:0902.1271 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 402 events p p

12. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 12 Now allow photons: EmEt spectrum with J/ψ mass cut: Empirical functional form MC also estimates only few % of under the cut 65 events above 80 MeV cut. 3 events below (estimated from fit)  4% background under J/psi  # = 65 +/- 8 E(EmEt) resolution, very low energy photons, does not allow separation of different χ c states, but data are consistent with χ c (3415).

13. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 13 Events with EM shower Good fits to kinematics with only, if EM shower Confirms assignment No photoproduced ψ’(2S) with EM shower > 80 MeV New MC: SuperCHIC (Lucien Harland-Lang & Durham) to use.

14. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 14 Summary of ResultsM = 3-4 GeV/c2 No strong evidence for odderon 90 nb (χ width) Durham Oops: PRL table (not text) says 27 +- 0.5 also

15. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 15 Khoze, Martin and Ryskin, Eur.Phys.J. C23: 311 (2002) ; KMR+Stirling hep-ph/0409037 36 fb Claim factor ~ 3 uncertainty ; Correlated to p+H+p H 3 candidates, 2 golden, 1 ? ? New data, Lower threshold, possible “observation” to come(?) & SuperCHIC ! 36 fb  0.8 events

16. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 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. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 17 E not ET! M(ee) = 49.3 GeV/c2 |Δφ-π| = 6 mrad = 0.34 deg, pT(ee) = 210 MeV M reach at Tevatron to 75 GeV/c 2 >~ HERA, LEP ! At LHC will be 100’s of GeV. 82 < M < 98 GeV

18. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 18 Agrees with LPAIR/QED in shape as well as normalization. All pairs back-to-back in Ø within 0.8 degrees! Before requiring BSC empty (no dissociation): 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. 8 pairs

19. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 19 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! COOL! (960 fb) Have 3 x more data. If allow pile-up get another factor x 5, but more background. (Not being actively looked at.) Exclusive Z limit: Combining e+e- and μ+μ- 0 candidates 0.66±0.11 background α.BR(ll).L eff = 3.22±0.38 pb -1 σ(Zexcl) < 0.96 pb @ 95% CL At LHC SM predictions ~ fb and may be just in reach!

20. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 20 Dimuons: Upsilon Region Invariant Mass 0 associated tracks pT(μμ) < 1.5 GeV/c CDF Run II Preliminary Trigger: μ+μ- |η| 4 GeV/c Inclusive Search for/measurement of photoproduction of Y(1S),Y(2S),Y(3S) (not before seen in hadron-hadron) 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(1S) Y(3S) Y(2S) CDF Run II Preliminary

21. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 21 Exclusive Upsilon Y(1S) candidate Run/Event: 204413/8549136 R-z, Muon hits Plugs, Miniplugs, CLC, BSC empty M ~ 9.4 GeV

22. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 22 e.g. A. Szczurek: arXiv:0811.2488 ~ 30 pb

23. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 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. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 24 Exclusive Di-Jets Phys Rev D77:052004 (2008) “Almost” exclusive di-jet, Two jets and nothing else JET Observed in CDF, QCD tests & related to p+H+p 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. J J GAP

25. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 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! 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). @ ISR

26. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 26 Summary Programme in CDF to measure central exclusive processes a)As interesting QCD physics in its own right but especially in a Tev-4-LHC spirit and to understand FP420/240 issues b)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: our star reaction! { } = no observation yet

27. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 27 Thank You

28. Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 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 q 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. calculable but with large uncertainties Measuring one constrains the others.