Diffraction at the Tevatron CDF Results K Goulianos

Diffraction at the Tevatron: CDF Results K. Goulianos The Rockefeller University presented on behalf of the CDF Collaboration Diffraction 2006 Milos island, Greece, 5 -10 September 2006 1

Contents Ø Run-I diffraction @ CDF Ø Run II results ü Diffractive structure function x. Bj, Q 2, and t dependence ü Exclusive production dijet & diphoton Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 2

Run-I Diffraction @ CDF T=Im fel (t=0) Elastic scattering f h SD f OPTICAL THEOREM GAP DD Diffraction 2006, Milos, Greece, Sep 05 -10 Total cross section h DPE Diffraction at the Tevatron: CDF results SDD=SD+DD K. Goulianos 3

Run I-0 (1988 -89) Elastic, single diffractive, and total cross sections @ 546 and 1800 Ge. V Roman Pot Spectrometers Roman Pot Detectors Ø Scintillation trigger counters Ø Wire chamber Ø Double-sided silicon strip detector Results Ø Total cross section Ø Elastic cross section Ø Single diffraction Diffraction 2006, Milos, Greece, Sep 05 -10 Additional Detectors Trackers up to |h| = 7 tot ~ se d /dt ~ exp[2 a’ lns] shrinking forward peak Breakdown of Regge factorization Diffraction at the Tevatron: CDF results K. Goulianos 4

Breakdown of Regge factorization Factorization Pomeron flux KG, PLB 358 (1995) 379 Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 5

Run-IC Run-IA, B, C Run-IA, B beam Forward Detectors BBC 3. 2<h<5. 9 FCAL 2. 4<h<4. 2 Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 6

Central and Double Gaps @ CDF q Double Diffraction Dissociation Ø One central gap q Double Pomeron Exchange Ø Two forward gaps q SDD: Single+Double Diffraction Ø One forward + one central gap Results: DD, like SD, is suppressed The formation of the second gap in two-gap events is not suppressed! Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 7

Hard Diffractive Fractions @ CDF d. N/dh h Fraction: SD/ND ratio at 1800 Ge. V % Fraction (+/-) W 1. 15 (0. 55) JJ 0. 75 (0. 10) b 0. 62 (0. 25) J/y 1. 45 (0. 25) Diffraction 2006, Milos, Greece, Sep 05 -10 All ratios ~ 1% ~ uniform suppression ~ FACTORIZATION ! Diffraction at the Tevatron: CDF results K. Goulianos 8

Diffractive Structure Function: Breakdown of QCD Factorization b = momentum fraction of parton in Pomeron The diffractive structure function at the Tevatron is suppressed by a factor of ~10 relative to expectation from pdf’s measured by H 1 at HERA H 1 CDF Using preliminary pdf’s from Diffraction 2006, Milos, Greece, Sep 05 -10 Similar suppression factor as in soft diffraction relative to Regge expectations! Diffraction at the Tevatron: CDF results K. Goulianos 9

Restoring factorization: multigap diffraction R(SD/ND) R(DPE/SD) DSF from two/one gap: factorization restored! w/preliminary pdf’s from The diffractive structure function measured on the proton side in events with a leading antiproton is NOT suppressed relative to predictions based on DDIS Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 10

Run II Results § Diffractive structure function NEW: Ø Q 2 - dependence Ø t - dependence § Exclusive production Ø dijet Ø diphoton Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 11

CDF in Run-II ROMAN POT DETECTORS BEAM SHOWER COUNTERS: Used to reject ND events MINIPLUG CALORIMETER Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 12

The Mini. Plugs @ CDF Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 13

DIFFRACTIVE STRUCTURE FUNCTION Systematic uncertainties due to energy scale and resolution cancel out in the ratio Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 14

Diffractive Dijet Signal - Bulk of data taken with RPS trigger but no RPS tracking - Extract x from calorimetric information - Calibrate calorimetric x using limited sample of RPS tracking data - Subtract overlap background using a rescaled dijet event sample - Verify diffractive x range by comparing x. RPS with x. CAL Overlap events: mainly ND dijets plus SD low x RPS trigger Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 15

Alignment of RPS using Data maximize the |t|-slope determine X and Y offsets Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 16

CAL x Calibration signal region overlap events xcal distribution for slice of x. RPS / mean ~ 30% Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 17

Dijet Properties jet p SD boosted opposite to pbar Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 18

ET distributions 120 Ge. V Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 19

Diffractive Structure Function: Q 2 dependence ETjet ~ 100 Ge. V ! Small Q 2 dependence in region 100 < Q 2 < 10, 000 Ge. V 2 Pomeron evolves as the proton! Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 20

Diffractive Structure Function: t- dependence Fit ds/dt to a double exponential: Ø No diffraction dips Ø No Q 2 dependence in slope from inclusive to Q 2~104 Ge. V 2 Diffraction 2006, Milos, Greece, Sep 05 -10 Ø Same slope over entire region of 0 < Q 2 < 4, 500 Ge. V 2 across soft and hard diffraction! Diffraction at the Tevatron: CDF results K. Goulianos 21

Diffractive dijets: Df=fpbar-fdijet Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 22

EXCLUSIVE PRODUCTION Measure exclusive jj & gg Bialas, Landshoff, Phys. Lett. B 256, 540 (1991) Khoze, Martin, Ryskin, Eur. Phys. J. C 23, 311 (2002); C 25, 391 (2002); C 26, 229 (2002) C. Royon, hep-ph/0308283 B. Cox, A. Pilkington, PRD 72, 094024 (2005) OTHER…………… Clean discovery channel Search for exclusive dijets: Measure dijet mass fraction Look for signal as Mjj 1 Diffraction 2006, Milos, Greece, Sep 05 -10 Calibrate predictions for H production rates @ LHC H KMR: H(LHC) ~ 3 fb S/B ~ 1 if DM ~ 1 Ge. V Search for exclusive gg Search for events with two high ET gammas and no other activity in the calorimeters or BSCs Diffraction at the Tevatron: CDF results K. Goulianos 23

Exclusive Dijet Signal D I J E T S Dijet fraction – all jets Excess over MC predictions at large dijet mass fraction Diffraction 2006, Milos, Greece, Sep 05 -10 b-tagged dijet fraction Exclusive b-jets are suppressed by JZ= 0 selection rule Diffraction at the Tevatron: CDF results K. Goulianos 24

RJJ(excl): Data vs MC Ex. Hu. ME (KMR): gg gg process uses LO p. QCD Exclusive DPE (DPEMC) non-p. QCD based on Regge theory Shape of excess of events at high Rjj is well described by both models Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 25

jjexcl: Exclusive Dijet Signal COMPARISON Inclusive data vs MC @ b/c-jet data vs inclusive Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 26

JJexcl : x-section vs ET(min) Comparison with hadron level predictions Ex. Hu. ME (red) Exclusive DPE in DPEMC (blue) Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 27

JJexcl : cross section predictions Ex. Hu. ME Hadron-Level Differential Exclusive Dijet Cross Section vs Dijet Mass (dotted/red): Default Ex. Hu. ME prediction (points): Derived from CDF Run II Preliminary excl. dijet cross sections Statistical and systematic errors are propagated from measured cross section uncertainties using Ex. Hu. ME Mjj distribution shapes. Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 28

JJexcl: R(excl/incl) vs ETmin Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 29

Exclusive gg/ee Search QED process: cross-check to exclusive gg ü (anti)proton not detected ü require 2 EM showers (ET>5 Ge. V, |h|<2) ü veto on all BSCs and cal towers except for those of the 2 EM showers ü L~530 pb-1 delivered Leffective=46 pb-1 ü 19 events with 2 EM showers + ”nothing” [above threshold] Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 30

Exclusive ee Search control sample for gg search 16 candidate events found background: ET 1=6. 1 Ge. V ET 2=6. 0 Ge. V good agreement with LPAIR: Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 31

Exclusive gg Search ET 1=6. 8 Ge. V/c ET 2=5. 9 Ge. V/c Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 32

Summary Run I Ø Suppression of single gap diffraction Ø M 2 – scaling: d /d. M 2 independent of s Ø Non-suppressed double-gap to single-gap ratios Run II Ø Diffractive structure function vs x. Bj, Q 2, and t Composite Pomeron made up from proton pdf’s ? Ø Exclusive production; dijet and diphoton Diffractive Higgs @ LHC under control Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 33

BACKUP Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 34

p-p Interactions Non-diffractive: Color-exchange Diffractive: Colorless exchange w/vacuum quantum numbers rapidity gap Incident hadrons acquire color and break apart P O M E R O N Incident hadrons retain their quantum numbers remaining colorless Goal: understand the QCD nature of the diffractive exchange Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 35

M 2 - scaling KG&JM, PRD 59 (1999) 114017 renormalization 1 Independent of S over a range of six orders of magnitude in M 2 ! Factorization breaks down so as to ensure M 2 -scaling! Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 36

x-dependence: Inclusive vs Dijet Pomeron dominated Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 37

The Mini. Plug Calorimeters About 1500 wavelength shifting fibers of 1 mm dia. are ‘strung’ through holes drilled in 36 x¼” lead plates sandwiched between reflective Al sheets and guided into bunches to be viewed individually by multi-channel photomultipliers. Diffraction 2006, Milos, Greece, Sep 05 -10 Diffraction at the Tevatron: CDF results K. Goulianos 38