exclusive dilepton (e + e -, + -,j/ , ', ) exclusive dilepton (e + e -, + -,j/ , ',...

Exclusive Dilepton (eExclusive Dilepton (e++ee--,,++--,J/,J/, , ',',))and Diphoton Production at CDF IIand Diphoton Production at CDF II

James L. PinfoldUniversity of Alberta

HIGH ENERGY PHOTON COLLISIONS AT THE LHC

MENU: CDF Motivation eMENU: CDF Motivation e++ee- - ++--,J/,J/,,'',, cc Odderon Odderon

ConclusionsConclusionsJames L. Pinfold Workshop on High Energy Photon Collisions at the LHC 1

CDF :: IntroductionCDF :: IntroductionRoman Pots not used

Muon Chambers

CDF Detector + Performance CDF Detector + Performance

Luminosity delivered 3.7 fb-1 about 3 fb-1 of data to tape

MENU: MENU: CDF CDF Motivation e Motivation e++ee- - ++--,J/,J/,,'',, cc Odderon Odderon


Motivation: for Exclusive Studies Motivation: for Exclusive Studies

Motivations to study exclusive lepton pair production:Motivations to study exclusive lepton pair production:– Potential to improve luminosity measurements at LHC since the cross Potential to improve luminosity measurements at LHC since the cross

section is known to better than ~5 %section is known to better than ~5 %– Can be used as a control sample for exclusive processes whose cross- Can be used as a control sample for exclusive processes whose cross-

sections are not well predicted (sections are not well predicted (, Higgs, ...), Higgs, ...)

– For example, a place to search for For example, a place to search for cc and the odderon and the odderon – Can be used to calibrate forward proton spectrometers (FP420) at LHC Can be used to calibrate forward proton spectrometers (FP420) at LHC

(important in the search for new physics & Higgs in exclusive channel)(important in the search for new physics & Higgs in exclusive channel) Main motivation to study exclusive ppMain motivation to study exclusive pp p + p + + p + p

– This process is a “standard candle” for exclusive Higgs productionThis process is a “standard candle” for exclusive Higgs production

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gX

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l+

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lIPJ/',q-loop

MENU: CDF MENU: CDF MotivationMotivation e e++ee- - ++--,J/,J/,,'',, cc Odderon ConclusionsOdderon ConclusionsJames L. Pinfold Workshop on High Energy Photon Collisions at the LHC 3

Exclusive eExclusive e++ee-- Production (1) Production (1)

Central state produced via Central state produced via QED QED e e++ee--

Protons do not dissociateProtons do not dissociate Only eOnly e++ee-- are produced are produced nothing else nothing else Process has never been observed before in Process has never been observed before in

hadron-hadron collisionshadron-hadron collisions

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e+

e

QED

MENU: CDF Motivation MENU: CDF Motivation ee++ee-- ++--,J/,J/,,'',, cc Odderon Odderon


Exclusive eExclusive e++ee-- Production (2) Production (2) Integrated luminosity → 532 ± 32 pbIntegrated luminosity → 532 ± 32 pb-1-1

DIFF_DIPHOTON Trigger:DIFF_DIPHOTON Trigger:– 2 EM clusters with E2 EM clusters with ETT>4GeV plus a veto on BSC 1 (E+W)>4GeV plus a veto on BSC 1 (E+W)

Exclusive eExclusive e++ee-- events are selected by: events are selected by:– Reconstructing the eReconstructing the e++ee--

– Requiring that there is no other activity in |Requiring that there is no other activity in ||<7.4 |<7.4 – Photons have EPhotons have ETT >5 GeV and |h| < 2 >5 GeV and |h| < 2– 16 e16 e++ee-- candidates selected candidates selected

Backgrounds 1.9 Backgrounds 1.9 ± 0.3± 0.3 events: events:– dijet fake ( 0.0 +0.1 -0.0)dijet fake ( 0.0 +0.1 -0.0)– cosmic ( negligible)cosmic ( negligible)– inclusive distribution (0.3+/-0.1)inclusive distribution (0.3+/-0.1)– dissociation (1.6 dissociation (1.6 ±± 0.3) (these are also gg 0.3) (these are also gg ee++ee-- where one (or where one (or

both) proton(s) dissociate)both) proton(s) dissociate) MENU: CDF Motivation MENU: CDF Motivation ee++ee-- ++--,J/,J/,,'',, cc Odderon Odderon


Exclusive eExclusive e++ee-- Production (3) Production (3) Kinematics of 16 event candidate sample match the predictions of the LPAIR Kinematics of 16 event candidate sample match the predictions of the LPAIR

signal MCsignal MC (J.Vermaseren. Nucl. Phys., B229 347-371, 1983 )- e (J.Vermaseren. Nucl. Phys., B229 347-371, 1983 )- e++ee-- are collinear in are collinear in and have matching Eand have matching ETT

Cross-section for Cross-section for e e++ee- - LPAIR theory:LPAIR theory: LPAIR LPAIR = 1.71 ± 0.01 pb= 1.71 ± 0.01 pb

MENU: CDF Motivation MENU: CDF Motivation ee++ee-- ++--,J/,J/,,'',, cc Odderon Odderon


Exclusive eExclusive e++ee-- Production (4) Production (4)

Agrees with LPAIR theory:Agrees with LPAIR theory: LPAIR LPAIR = 1.71 ± 0.01 pb= 1.71 ± 0.01 pb

Probability of 1.9 Probability of 1.9 ≥≥16 = 1.3×1016 = 1.3×10-9-9 - corresponds to 5.5 - corresponds to 5.5 “observation”“observation”

This is the first observation of exclusive two-photon produced This is the first observation of exclusive two-photon produced ee++ee-- interactions in hadron-hadron collisions interactions in hadron-hadron collisions

The LHC can rely on measuring such processes for luminosity The LHC can rely on measuring such processes for luminosity measurement, etc.measurement, etc.

We have many more candidates in new data with dedicated 2-EM shower triggerWe have many more candidates in new data with dedicated 2-EM shower trigger MENU: CDF Motivation MENU: CDF Motivation ee++ee-- ++--,J/,J/,,'',, cc Odderon Odderon


Exclusive Exclusive Study (1) Study (1)

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Exclusive Exclusive events: events:– selected in the same way as eselected in the same way as e++ee-- (except tracking) (except tracking)

Selected in the same way as Selected in the same way as ee++ee-- (except tracks) (except tracks) agreement of agreement of ee++ee-- cross section gives confidence in cross section gives confidence in analysis methodologyanalysis methodology



where X has JPC = 0++

XX

Exclusive Exclusive Study (2) Study (2) 3 candidate events are found in 532 pb-1 of Run II data.3 candidate events are found in 532 pb-1 of Run II data. Background 0.09 ± 0.04 events (dominated by misid. of excl.) Background 0.09 ± 0.04 events (dominated by misid. of excl.) Good agreement on kinematics with ExHume MC Good agreement on kinematics with ExHume MC (Monk & Pilkington. hep-ph/0502077)(Monk & Pilkington. hep-ph/0502077) 0.8 0.8 +1.6+1.6

-0.5 -0.5 events predicted from ExHuME MC events predicted from ExHuME MC -2 candidates are almost certainly -2 candidates are almost certainly but the but the hypotheses cannot be excludedhypotheses cannot be excluded



Exclusive Exclusive Candidates (1) Candidates (1)

We have found >10 more candidates in new data with new di-EM shower trig.

Possible event



The upper limit of the cross-section pp --> p p is set at 410 fb with 95% confidence level ( taking into account the background + its uncertainty, signal selection efficiency, & Lint)

If 2 of the 3 candidates are events we obtain a cross section:


12030(2 events) (90 16) fb

Durham Group Khoze, Martin, Ryskin & Stirling hep-ph/0507040 Eur.Phys.J C38 (2005) 475 : 38 fb with factor ~ 3 uncertainty



Exclusive Exclusive Production (1) Production (1)

Trigger (DIFF_CHIC_CMU1.5_PT1.5_TRK):Trigger (DIFF_CHIC_CMU1.5_PT1.5_TRK):– BSC Gap, east & westBSC Gap, east & west

– muon + track (pmuon + track (ptt > 1.3; | > 1.3; || < 1.2)| < 1.2)

– 2.7 < M(muon + track) < 4.0 GeVc2.7 < M(muon + track) < 4.0 GeVc22

No other activity in the events (to an |No other activity in the events (to an || of 7.4)| of 7.4) The existing sample corresponds to a luminosity 1.48 fbThe existing sample corresponds to a luminosity 1.48 fb -1-1

Also higher mass muons have just been stripped, (trigs with pAlso higher mass muons have just been stripped, (trigs with p tt(() > 4 ) > 4 GeV, 2 muons, no Df requirement).GeV, 2 muons, no Df requirement).

Should be very efficient for dimuons, with M >~ 9 GeV, covering the Should be very efficient for dimuons, with M >~ 9 GeV, covering the Upsilon region and above.Upsilon region and above.



Exclusive Exclusive Production (2) Production (2)

Example exclusive Example exclusive ++- - event: event: Run 199559, Event 13120174 Run 199559, Event 13120174



Exclusive Exclusive Production (3) Production (3) Integrated luminosity – 1.48 fbIntegrated luminosity – 1.48 fb-1-1

Offline cutsOffline cuts– Loose quality cutsLoose quality cuts

– PPTT(() > 1.4 GeV/c & |) > 1.4 GeV/c & |(()| < 0.6 )| < 0.6

– Cosmic ray cuts (abs (delta_TOF) < 3 ns)Cosmic ray cuts (abs (delta_TOF) < 3 ns)

– Exclusivity cuts (same as for the eExclusivity cuts (same as for the e++ee-- paper) paper)

Analysis of cuts is underwayAnalysis of cuts is underway– AcceptanceAcceptance

– EfficiencyEfficiency

– Effective luminosityEffective luminosity

STARLIGHT Monte Carlo simulation employed (S. STARLIGHT Monte Carlo simulation employed (S. Klein & J. Nystrand)Klein & J. Nystrand)



Many candidate events (334) have been found (CDF-II Preliminary)Many candidate events (334) have been found (CDF-II Preliminary)

We expect to increase the number of candidates after review of the cutsWe expect to increase the number of candidates after review of the cuts




Continuum


Good agreement on kinematics with Good agreement on kinematics with STARLIGHT MC (Klein & Nystrand )STARLIGHT MC (Klein & Nystrand )

The continuum



Exclusive Exclusive cc Production Background Production Background

Similar selection as search with additional single isolated EM shower req.

10 candidates in 93 pb-1 of data

Many more candidates with new trigger

New ChicMC (James Stirling)

ExAnalysis in the doldrums after Angela Wyatt left for industry

It is just now being actively worked on…watch this space

Problem is - understanding low energy photon background

Many more events with new trigger



o + -c

-1

In reality: BR(χ J/ψ γ μ μ γ)

no other interaction acceptance(trig)

few pb (1000's in 1 fb )

Exclusive Exclusive Candidates (High Mass) (1)Candidates (High Mass) (1)

Find Exclusive events using Find Exclusive events using – Number of associated tracks = 0Number of associated tracks = 0

– Kinematics: Kinematics: 180 180oo, , ppTT 0, (or 0, (or PPTT 0) 0)

Trigger: 2 central muons with pT > 4 GeV/c

L = 890/pb-1 ~ 2.3 M events.

Remove cosmic rays (timing + colinearity)

Require on beam-line. Count additional (associated) tracks (n_ass) within 5 cm of vertex.

Cleanliness, backgrounds & acceptances being studied.

Number of events “reasonable” for QED process & Lumi. MENU: CDF Motivation eMENU: CDF Motivation e++ee- - ++--,J/,J/,,'',, cc Odderon Odderon


Invariant Mass - Upsilon Region

Clearly visible peaks Y(1s) and Y(2s),perhaps Y(3S) too.+ continuum

(nassoc_tracks = 0) Exclusive candidates

GeV/c7)(p,120 T0




(1s)

(2s)

(3S)? ContinuumContinuum

Run/Event: 204413/8549136

Lego, threshold ET > 10 MeV

Now apply “super clean” exclusivity cuts as in low mass l-pair mass i.e. no pile-up, and only -pairs detected

145 events in 8 – 12 GeV region 6 events + 4 M( ) > 12 GeV.(Most of reduction is killing pile-up)

Superclean Upsilon




Exclusive Di-leptons – a Good Exclusive Di-leptons – a Good Place to Search for the OdderonPlace to Search for the Odderon

In perturbative QCD the lowest order prototype of the pomeron is the In perturbative QCD the lowest order prototype of the pomeron is the color neutral system of two gluons. color neutral system of two gluons.

The odderon is the C-odd partner of the pomeron - the hard odderon The odderon is the C-odd partner of the pomeron - the hard odderon skeleton consists of three gluons in a color neutral state. skeleton consists of three gluons in a color neutral state.

Global fits of the available hh and hh-bar data seem to establish that HE Global fits of the available hh and hh-bar data seem to establish that HE scattering dominated by exchange of the C = P = +1 Pomeron.scattering dominated by exchange of the C = P = +1 Pomeron.

If the Odderon exists it would contribute to the exclusive J/If the Odderon exists it would contribute to the exclusive J/ and and ' ' signal and be part of our signal signal and be part of our signal

The Odderon would contribute to J/The Odderon would contribute to J/, , '', , peaks upeaks unlike the nlike the cc backgroundbackground



ConclusionConclusion The paper on the observation of exclusive p-pThe paper on the observation of exclusive p-p p + ep + e++ee-- + p production + p production

has been published in PRL (March 2007) has been published in PRL (March 2007) – Studies continue with new low EStudies continue with new low ETT di-photon trigger di-photon trigger

The study of exclusive p-pThe study of exclusive p-p p p ++ ++ p production was published in p production was published in PRL (December 2007)PRL (December 2007)

– Studies are continuing with a new low EStudies are continuing with a new low ETT di-photon trigger di-photon trigger ( (EETT>3GeV)>3GeV)

The study of p-pThe study of p-p p + p + ++ p, J/ p, J/, J/, J/ '', , , is underway , is underway Implications for the LHC Implications for the LHC

– Use ofUse of / /ee++ee-- as a luminosity monitor as a luminosity monitor

– Study ofStudy of g-p g-p as a calibration for FP420 is underway as a calibration for FP420 is underway

– Exclusive study of p-pExclusive study of p-p J/J/, , ’,…’,… is a good place to search for the is a good place to search for the odderonodderon

– The process p-pThe process p-p//cc is a standard candle for the exclusive Higgsis a standard candle for the exclusive Higgs

– We are understanding how to use the LHC as aWe are understanding how to use the LHC as a , , -p (-p ( IP) & IP- IP collider collider



Extra SlidesExtra Slides

Tevatron PerformanceTevatron Performance

Collider Run II – anticipated 67 fb-1 by end FY09with 2010 running 7 9 fb-1

Motivation: for Exclusive Studies (1)Motivation: for Exclusive Studies (1)

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• We are looking at We are looking at exclusiveexclusive channels to study: channels to study:• LHC as a LHC as a collider - exclusive production models for new and SM collider - exclusive production models for new and SM

physicsphysics• Measurement of luminosity at the LHC &Measurement of luminosity at the LHC &• Calibration of forward detectors (FP420) using Calibration of forward detectors (FP420) using ll++ll--

• LHC as a LHC as a p collider higher energy reach & luminosity yield than for p collider higher energy reach & luminosity yield than for case case

• Experimental techniques to select exclusive events at the LHCExperimental techniques to select exclusive events at the LHC• Advantages: Advantages: reconstruct mass of central state reconstruct mass of central state (if protons (if protons

tagged)tagged)Related measurements: In Heavy Ion Collisions:

A. Belkacem et al., Phys. Rev. A 56, 2806 (1997); C. Vane et al., Phys. Rev. A 50, 2313 (1997); R. Baur et al., Phys. Lett. B 332, 471 (1994); J. Adams et al., Phys. Rev. C 70, 031902 (2004).

In pp Collisions:D. Antreasyan et al., CERN-EP/80-82 (1980).

In ep Collisions:…

Standard Model:W+W- ttH

Beyond SM:H+H- S+S-

~1% of pp luminosity

Motivation: for Exclusive Studies (2)Motivation: for Exclusive Studies (2)

Number of Higgs events for single tags and assuming integrated luminosity of 30, 0.3 and 0.03 fb1 for pp, pAr and ArAr collisions, respectively.

hep-ex/0009065

Reconstruct central state using FP420

Motivation: for Exclusive Studies (3)Motivation: for Exclusive Studies (3) Exclusive Diffraction:Exclusive Diffraction:

where X has JPC = 0++

• Two significant advantages over inclusive case:• mass of X can be determined from outgoing protons• ‘measures’ the quantum numbers of X

• Exclusive channels we are looking at involve photons: - very ‘clean’ signature, but low cross section

• This channel is a Standard Candle for exclusive DPE Higgs prod.(Calculations of V.Khoze et al., show that pomeron-pomeron cross-sections for Higgs production are a few times larger than for the case)

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Khoze, Martin and Ryskin, hep-ph/0111078, Eur.Phys.J. C23: 311 (2002)KMR+Stirling hep-ph/0409037

QCD diagram identical to pHp

38 fb

-1T~ 40 events per fb with p (γ) > 5 GeV/c & |η| < 1.0

& much smallerqq

Central Exclusive 2-Photon ProductionMGA et al. (2001) hep-ex/0511057

21 2

M( ) ~ 10 20 GeV

, similar, lower

top u,c (mainly)

x x Q

Tevatron

Claim factor ~ 4 uncertainty

Cleanest test of p+H+p theory

Exclusive eExclusive e++ee-- Study Results Study Results 4 backgrounds are considered:4 backgrounds are considered:

•Jet Fakes: 0.0+0.1-0.0 events

•Cosmics: negligible•Inclusive (QCD) events: 0.3 ± 0.1 events•Dissociation events: 1.6 ± 0.3 events

• Efficiency•Electron ID: (26 ± 3) %•Cosmic Rejection: (93 ± 3) %•Final State Radiation: (79 ± 5) %•Exclusive Cuts: 8.6 %

measured = 1.6(stat)±0.3(sys)pbAgrees with LPAIR theory: LPAIR = 1.71 ± 0.01 pb

corresponds to 5.5observation”

The OdderonThe Odderon

The color neutral gluon systems, exchanged at high energy The color neutral gluon systems, exchanged at high energy scattering processes, can be classified wrt their C parity. The most scattering processes, can be classified wrt their C parity. The most important one is C-even system with quantum numbers of vacuum important one is C-even system with quantum numbers of vacuum i.e. the pomeron. i.e. the pomeron.

In perturbative QCD the lowest order prototype of the pomeron is the In perturbative QCD the lowest order prototype of the pomeron is the color neutral system of two gluons. color neutral system of two gluons.

The odderon is the C-odd partner of the pomeron - the hard odderon The odderon is the C-odd partner of the pomeron - the hard odderon skeleton consists of three gluons in a color neutral state. skeleton consists of three gluons in a color neutral state.

One would naively expect a suppression by a power of the coupling One would naively expect a suppression by a power of the coupling constant s for the additional gluon). It is not clear, however, why the constant s for the additional gluon). It is not clear, however, why the contribution of the odderon is so small that it has not been definitely contribution of the odderon is so small that it has not been definitely observed by any experiment.observed by any experiment.

exclusive dilepton (e + e -, + -,j/ , ', ) exclusive dilepton (e + e -, + -,j/ , ',...

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