# Presentation: 884276

## Update on CDF Results on Diffraction

- The Rockefeller University
- (Representing the CDF Collaboration)
- DIS 2005
- 27 April – 1 May
- Madison, Wisconsin

**Update on CDF Results ****on Diffraction**

## -p Interactions 

- _Diffractive:_
- vacuum exchange

- Protons retain their
- quantum numbers

- _Non-diffractive:_
- color exchange

- Protons acquire color
- and break apart

- Goal: understand the nature of the colorless exchange

## 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

- _Results_
-   Total cross section          tot ~ s
-   Elastic cross section        d/dt ~ exp[2’ lns]   shrinking forward peak
-   Single diffraction	     Breakdown of Regge factorization

- _Additional Detectors_
- Trackers up to |****| = 7

## Run 1-0 results in perspective 

## CDF Run 1 (1992-1995)

## Diffraction @ CDF in Run I

**93(2004)141601**

## Diffractive Fractions @ CDF

- ~ uniform suppression
-   ~ FACTORIZATION

- _Diffractive Fractions @ CDF_

_**Fraction:**_
**SD/ND ratio**
**at 1800 GeV**

## R(SD/ND) vs xBj

- 0.035 <  < 0.095

- Flat  dependence

## Tevatron vs HERA:Breakdown of QCD Factorization

- CDF

- H1

## Restoring Factorization 

- The diffractive structure function measured on the proton side
- in events with a leading antiproton
- is NOT suppressed relative to predictions  based on DDIS

## Run 2 Diffractive Program

- _ __Single Diffraction_
-    and Q2 dependence of FjjD
-    Process dependence of FD (W, J/
- _ __Double Diffraction_
-   Jet-Gap-Jet: gap for fixed large jet
- _ __Double Pomeron Exchange_
-   FjjD on p-side vs -pbar
- _Also:_
- _Exclusive central production_
-   Dijets, c
- _Other __  _
-   Tev4LHC issues

## SD and ND collisions

- _SD and ND collisions_

- ND

- ND

- SD

- Particle density

- Energy flow

## CDF-II

- _CDF-II_

## Artist’s View of MiniPlug

## MiniPlug Run II Data

**ADC counts in MiniPlug towers**
**in a pbar-p event at 1960 GeV.**
**  ****“****jet” indicates an energy cluster   **
**   ****and may be just a hadron****. **

**Multiplicity distribution in SD and ND events**

**MiniPlug tower structure**

##  Diffractive Structure Function

## Diffractive Dijet Sample

- overlap events

## RP vs cal

- overlap events

- signal region

-  cal distribution for slice of RP

-  cal = (0.94 ± 0.03) RP

- /mean ~ 30%

## Rjj

## FjjD @ low 

- FjjD @ low 

- Measure -dependence of Fjj(,t) down to ~0.001
- using gap trigger

- STATUS:
- Data at hand
- Analysis in progress

## Diffractive W production

- Probes the quark content of the Pomeron
-  More direct comparison with HERA

- hard-gluon dominated Pomeron
- (rate lower by s)

- hard-quark dominated Pomeron

-  Run I: 8,246 W(ev) events - PRL 78 (1997), 2698
-  RW (SD/ND) = 1.15 ± 0.51(stat) ± 0.20(syst) %

- Status: data at hand, analysis in progress

## Gap Between Jets

- Is the diffractive exchange BFKL-like
- or simply a color rearrangement?

- Work in progress: low luminosity run needed

##  Exclusive Dijet Production

- _Use dijet rate to calibrate Higgs production calculations_

- _Khoze, Martin, Ryskin_:  Eur. Phys. J. C23, 311 (2002); C25,391 (2002);C26, 229 (2002)
- _Boonekamp, Peschanski, Royon: _PRL 87, 251806(2001)

## Exclusive Dijets in Run 1

- not detected

- Exclusive dijet limit:
- jj (excl.) < 3.7 nb (95% CL)

- Dijet
- Mass fraction

**Expected shape of signal events**

- Theoretical expectation (KMR) ~1 nb

**PRL 85 (2000) 4215**

- Mx

## Run 2 dijet mass fraction

- _Run 2 dijet mass fraction_

| Minimum ET(Jet1) | Cross section (Rjj>0.8) |
| --- | --- |
| 10 GeV |    1.1 ± 0.1(stat) ± 0.5(syst) nb |
| 25 GeV | 25 ± 3(stat) ± 10(syst) pb |

- exclusive?

## Exclusive Dijet Events ?

- Rjj=0.36

- Rjj=0.81

- ETjet1(2) = 33(31) GeV

- ETjet1(2) = 36(33) GeV

## Limits on Exclusive production

-                               Martin, Kaidalov, Khoze, Ryskin, Stirling
-                 hep-ph/0409258): ~ 40 pb (ET>25 GeV) (factor ~2 uncertainty)

## Heavy flavor exclusive dijets

- _Heavy flavor exclusive dijets_

- Experimental method:
- normalize Rjj(qq) to Rjj(all jets)
-  look for suppression at large Rjj
- _Pros:_	many systematics cancel out
- 	good HF quark id
- 	small g mistag O(1%)
- _Cons:_	heavy quark mass:
- 	suppression is not complete

- illustration

## Heavy flavor tagged dijet fraction

**R****btag****(R****jj****>0.7)/R****btag****(R****jj**** <0.4)=****0.59**** ± 0.33 (stat) ± 0.23 (syst)**

- exclusive production?
- _need_:
-  to compare with MC
-  more data !

## Exclusive C

## CONCLUSION

- _Run 2_
- CDF has a comprehensive Run 2 diffractive program
-   Data at hand are being analyzed
-   More data are being collected
-   Proposal for low luminosity (~1030) run under study
- _Beyond Run 2_
-   Tev4LHC studies