Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 1 Central Exclusive Production...

$: Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 1 Central Exclusive Production in CDF Mike Albrow, Fermilab e+e- Mass 10 – 40 GeV,$
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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010

Central Exclusive Production in CDFMike 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-, 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

cIPIP

ZSYSYSYSJIP

ee

,

(?)),3(),2(),1(),2(',/

,

Search for

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Introduction

pXppp

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 ΔyLooking forward to LHC:Interesting LHC examples ...,

~~,,, llWWHhX

If see h, H : Mass, width, spin J, C = +1, Couplings Γ(Hgg), …in a unique way, even if e.g. bb(150)&bb(140) Hh

Central Exclusive Production

(& VM:J/ψ,ψ’,Υ)

X

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/0

5110

57Pile-up reduction:Quartz + MCP-PMT

4


σ(p+H+p) was uncertain (to asimple experimenter) by a factor > 1000 in 2000

pJJppp

pppp

pppp

pppp

b

c

We absolutely needed someexperimental input to home inon what to expect!

* Now measured in CDF

*

*

*

p+p p + H + p cross sections

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pJJppp

pppp

pppp

pppp

b

c

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

(KMRS) nb100~)0( ydy

d

More perturbative, smaller theory uncertaintyBut σ ~ 1/500th χc. 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.

H JJ, ,χ ,χ γγ,

(980)fσ(600),

bc

0ISR did it … but it is not perturbative (IP+IP→ f/σ → π+π-)

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CDF Forward Detectors:

BSC 1 BSC 2,3,4

CLCCherenkov Luminosity Counters

MINIPLUG

BSC very important as rap gap detectors.

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Photon “beams” radiated from electrons and protonsLEP 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

ee

PRL 98,112001(2007)

2GeV/c)μM(μ

μμ

PRL 102, 242001 (2009)

μμeeμμ

inel12σ103~pb0.24~σ

Tevatron as a collider!

PRL 102, 222002 (2009)

dφ 180-dφ

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All our dilepton measurements agree with QED: So what?

1) It shows we know how to select rare exclusive events in hadron-hadron environment2) 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:

.,..~~

,WWγγ ll

2 |η| and GeV 10)μM(μ

withpb500in events 4400-

1

Luminosity calibration at LHCCannot veto pile-up! Testing nowin CDF M(μ+μ-) > 8 GeV/c2

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c0c

J/ψ

γ

μ+

μ-

& nothing elsein all CDF

-7.4 < |η| < + 7.4Beam 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.

4.7||2.5

CDFcentral

BSC

- 50 m

We set out to measure exclusive c J/ψ + → μ+μ-

Plan to put these (FSC) with CMS

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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).

500100 1000 counts

Example: BSC1 (8 PMTs)5.4 < |η| < 5.9Hottest PMT (no int/int)

0cc

Exclusive production0c

Exclusive requirement:

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arXiv:0902.1271

Fit: 2 Gaussians + QED continuum.Masses 3.09, 3.68 GeV == PDGWidths 15.8,16.7 MeV=resolution.QED = generator x acceptance3 amplitudes floating

402 events

p

p

(95%) J/ψOIPfor nb 2.3 )(J/ 0y|dy

dσ

(CDF) nb 0.623.92)(J/ψ 0y|dy

dσ

average)(theory, nb 0.33.0)(J/ψ 0y|dy

dσ

nb 0.46:Theory

nb 0.140.53 :CDF

:)]2('[|

0.110.04

0

Sdy

dy

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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

4039:not do ψ(2S)

352286 :photons have J/ψ

γJ/ψχ c

cχ

γJ/ψχ c

E(EmEt) resolution, very low energy photons, does not allow separation

of different χc states, but data are consistent with χc (3415).

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)/(pand)(:J/ψonfitsKinematic T JEvents with EM shower

Good fits to kinematics with only , if EM showerμμ c

Confirms assignment

cχ

cχ

No photoproduced ψ’(2S) with EM shower > 80 MeV

New MC: SuperCHIC (Lucien Harland-Lang& Durham) to use.

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Summary of Results

pppp

pppp

M = 3-4 GeV/c2

No strong evidence for odderon

90 nb(χ width)Durham

Oops: PRL table(not text)says 27 +- 0.5

Δφ)(γIP)(πΔφ)(γγ)(π

<pT> also

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Khoze, Martin and Ryskin, Eur.Phys.J. C23: 311 (2002) ; KMR+Stirling hep-ph/0409037

36 fb

& much smallerqq

Claim factor ~ 3 uncertainty ; Correlated to p+H+p

H

TE ( ) > 5 GeV; | ( ) | 1.0

3 candidates, 2 golden, 1 ? ?12Note : 2 10 !MEAS INEL

New data, Lower threshold, possible “observation” to come(?)& SuperCHIC !

00ππ36 fb 0.8 events

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

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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/c2 >~ HERA, LEP !At LHC will be 100’s of GeV.

82 < M < 98 GeV

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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, butnot exclusive. (SC)Dissociation? not like QED γγ

One event has a Roman pot pbar track, others hadpbar out of acceptance or Roman pots off.

pb 0.256QED cf

pb 24.0

4||,GeV/c40

μμor )(

(LPAIR)

13.010.0

2

M

peeppp

,Tp

8 pairs

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Predictions: Standard Model:Motyka and Watt, PRD 78, 014023 (2008) : σ(Z,excl) = 0.3 fbGoncalves and Machado, Eur.Phys.J. C 56, 33 (2008) : σ(Z,excl) = 0.21 fbBeyond 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 candidates0.66±0.11 backgroundα.BR(ll).Leff = 3.22±0.38 pb-1

σ(Zexcl) < 0.96 pb @ 95% CL

At LHC SM predictions ~ fb and may be just in reach!

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Dimuons: Upsilon Region

Invariant Mass 0 associated trackspT(μμ) < 1.5 GeV/c

CDF Run II Preliminary

Trigger: μ+μ- |η|<0.6 , pT(μ) > 4 GeV/c

Inclusive

Search for/measurement ofphotoproduction of Y(1S),Y(2S),Y(3S)(not before seen in hadron-hadron)

Status:analysis in progress.QED continuum check, butkinematics better constrained.Y : cf HERA (we resolve states)Can we see ?At most a few events, but BR’snot known. Only “existence proof”(& not yet).

Y(1S)

Y(3S)

Y(2S)

γΥχ b

CDF Run II Preliminary

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Exclusive Upsilon Y(1S) candidate Run/Event: 204413/8549136

R-z, Muon hits

Plugs, Miniplugs, CLC, BSC empty

M ~ 9.4 GeV

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e.g. A. Szczurek: arXiv:0811.2488

/J

)2(' S

)1( S~ 30 pb

)2( S

/)0(

500

1~)1()0( Jy

dy

dSy

dy

d

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1233

236

scm10Lat5/hour~

cm101.25~0.250250 2. pb100~

Eff. Acc. ).μμ(BR Δy. .dy

dσ~Rate

Rate for Y @ LHC:

at Tevatron and LHCb

c 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

b

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Exclusive Di-Jets Phys Rev D77:052004 (2008)

“Almost” exclusive di-jet,Two jets and nothing else

0.8JJ

CEN

M

M

(~ polar angle)

(azimuth) Transverse

Energy TE

JETJETelse nothing~ pJJppp

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.

p JJ

GAP

JJJJ

X

MR = 1.0

M

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Central Exclusive Production (DPE) of hadronsNot 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!

GeV 63s

,...!ΩΩ ,ΣΣ ,Λ,...ΛDD ,DD ,KK SS000

S0S

Produced in pure CP-even state.In e+e- (and φ-decay) pure CP-odd

Can be done (technically) in CDF withoutdetecting 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

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Summary

}{,,

}),3(),2(),1({),2(',/

,

bcIPIP

ZSYSYSYSJIP

ee

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

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Thank You

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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

H JJ, ,χ ,χ γγ, bc

Many ingredients to QCD calculation:

1) gg → X through q-loop2) A color-cancelling g exchange {g(x1,x2)}3) No gluon radiation → hadron production4) No other parton-parton interaction.H JJ, ,χ ,χ γγ,

(980)fσ(600),

bc

0

calculable but with large uncertaintiesMeasuring one constrains the others.

Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010 1 Central Exclusive Production...

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