Mike Albrow FermilabISMD 2008, Sept 2008Central Exclusive Production at the Tevatron 1 Central...

1Mike Albrow Fermilab ISMD 2008, Sept 2008Central Exclusive Production at the Tevatron

Central Exclusive Production at the Tevatron (CDF)Mike Albrow (Fermilab) for the CDF Collaboration

Introduction

ISR : π+ π- etc.

Tevatron: e+e-, γγ, μ+μ-, J/ψ, ψ(2S), χ_c, Υ …. Z?

LHC: Z, H, W+W-, …

pp p X p where X is a simple system completely measured

JJ

VeryFewParticle


ISR – Tevatron -- LHC

1) Central Exclusive Production:

2) LHC: Study of Higgs through p + H + p, WW and ZZ + + + FP420: R&D project; proposing extensions to ATLAS & CMS.

pp

pp

p

p

p

p

W

-WG? H?

Our measurements are the first 2-photon in hadron-hadron, and test both the production mechanisms and calibration techniques. ~ same diagramH,χ c

bcJee ,,,',/,, ,...~~

,, llWWH ppKK ,,


In collisions (through LEP energies I L C) : hadrons, and at high energy:WW WW, WW Z,H ; WZ W

In ep collisions (HERA) :gamma-IP vector mesons ( too but buried?)

In (ISR Tevatron and LHC) :IP IP hadrons (can be single hadron), Higgs, -IP vector mesons (.. ,Y, Z(allowed but tiny)) l+l- ( too but buried?)

In AA (RHIC, LHC) mainly (E-fields) -IP and IP+IP

Central Exclusive Production in Different Machines

New in CDF

eeqqll ,

,/,, J

γγγ

qq

ll

ll

γγ

qq

)p(ppp

γ


Central Exclusive Production is very clean, ~ no backgrounds

Rapidity y

~ 7.4~ -7.4

pp ,,)'(, ,bc

|y| < 1

With rapidity gaps > 6 on both sides, t-channelexchanges are very limited:Charge Q = 0, No color, and spin J >= 1.0

Allowed exchanges: only photons, IP = pomeron {~gg}Odderon {~ggg} not yet observed,Z (but p would always break up!)

y p

p

t

only from , continuum. only from IPIP. bc,

)'( only from IP, OIP(?)

yy


Central Exclusive Production of Higgs

Higgs has vacuum quantum numbers, vacuum has Higgs field.So pp p+H+p is possible.Allowed states:

Process is gg H through t-loop as usualwith another g-exchange to cancel colorand even leave p’s in ground state.If measure p’s:

H

2CEN 1 2 3 4M ( )p p p p

+ - ±Even for H W W l νJJ !

Aim: be limited by incoming beam momentum spreadp -4σ

10 0.7 GeVp

MGA+Rostovtsev: hep-ph/0009336

PC ++I J =0 even

J >= 2 strongly suppressed at small p angle (t)

t

4-vectors

( ) 2 GeV per eventHM

0c

0b

u-loop : γγ c-loop : χ

b-loop : χ t-loop: H


G(1710)??

0 (980)f

No ρ

Structures not well understood beyond f(980)Not studied at higher

Central Exclusive Production at ISR = 63 GeV (AFS)

3500 events/25 MeV )( M

DPE would be greatfor G-spectroscopy. Waitingto be done at Tevatron! Student?

ppandKKAlso

s

Axial Field Spectrometer (R807)Added very forward drift chambers

D.P.E. & Search for “Glueballs”

{ } as distinct from { }gg qq

data

pp

ALSO )600(0f

s


CDF Detector at Fermilab Tevatron

MiniPlugs

980 GeV p980 GeV pbar

Muon ChambersCalorimeters


Installed very forward Beam Shower Counters (BSC) for rapidity gapsand scintillating fiber trackers in Roman pots for pbar detection

Not at all to scale!

Roman pot detectors 20mm x 20mm55 m downstream.Beam Shower Counters BSC tight around pipe.Full coverage –7.4 < < +7.4

vetoedetc,; pnpby beam shower counters

In this talk I do not useRoman pots; do not haveacceptance for low mass


16 events

0 0: 180 2

( )10 38 GeV

small ( resolution)T

e e

M e e

p

QED process : collisions in ppγγ

Monte Carlos : LPAIR, GRAPE, STARLIGHT

Exclusive Electron-Positron Production in Hadron Collisions (CDF)

Phys.Rev.Lett 98,112001(2007)

0.5. 0.3

-9

Estimated background = 1.9 0.3

(mostly p-dissociation)

1.6 (stat) 0.3 (syst) pb

p-value = 1.3 10 ( 5 )

MEAS

QED (1.711 0.008) pb

TE ( ) 5 GeV; | ( ) | 2.0e e


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

QCD diagram identical to pHp

36 fb

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

& much smallerqq

Exclusive H Theory Calibration: Exclusive 2-PhotonMGA et al. (2001) hep-ex/0511057

21 2

M( ) ~ 10 20 GeV

, similar, lower

top u,c (mainly)

x x Q

Tevatron

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


12Note : 2 10 !MEAS INEL

3 candidates observed:

It means exclusive H must happen(if H exists) and probably ~ 5 fbwithin factor ~ 3. is higher in MSSM

Phys.Rev.Lett. 99,242002 (2007)

Exclusive Production in Hadron-Hadron Collisions

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

0 0

Actually 2 events are good candidate

and 1is a good candidate.

(Remember at ISR)

Prediction V.A.Khoze et al. Eur. Phys. J C38, 475 (2005) (our cuts) = (36 +72 – 24) fb = 0.8 +1.6 –0.5 events.Cannot yet claim “discovery” as b/g study a posteriori, 2 events correspondsto ~ 90 fb, agreeing with Khoze et al.

s

ExHuME Monte CarloJames Monk &Andy Pilkington (MCR)

gg


New Results, hot off the press:

pppp 2

μμ2 GeV/c 4MGeV/c3

Region rich in physics. First observations in (elastic) hadron-hadron:

cχIPIP

ψ(2S) & J/ψIPγ

μμγγ

1 & 2 ) Forward proton momenta precisely known: calibrate momentum scale of forward spectrometersfor p + p p + H + p at LHC.3) Calibrate theory (x-sn) of p + H + p

1)

2)

3)


There are 4, maybe 5, physics processes in this data!

1) 2-photon (QED) production of the continuum (no resonances) We published this in 2007 for e+e- [ee] with M > 10 GeV (16 events as in QED)

2) Photon + IP … photoproduction, as in ep at HERA3) Photon + IP … photoproduction, as in ep at HERA4) IP + IP

/J)2(' S /Jc

IP = pomeron

1)

4)

2,3) )2(' Sor


Data: Feb 2002 – March 2007Luminosity (Good Runs) = 1.48/fb (+/- 6%)Trigger = muon + track +BSC1 gaps 2 muonsNumber of events on tape: ~ 1.6 million

2-T GeV/c4.0)μM(μ3.0GeV/c,1.4(μμp,0.6|η(μ)| )

Reject cosmic ray events (ToF, colinearity) … 100% efficientExclusivity: Require all detectors < noise cuts except in mumu direction


Exclusivity cuts

Want to be sure no other particles were produced.Take 0-bias = bunch crossing data.Put in two classes: non-interaction (dominated), no tracks, no CLC hits, no muon stubs interaction (dominated), all othersFor each sub-detector: 5 calorimeter regions, 3 BSC counter hodoscopesFind largest signal and plot it as [Log_10 max ADC counts]

We did this for each of (11)periods of data, finding cutefficient at selecting “nothing”i.e. noise thresholds.

Red mini-peak is not ineffiency,mainly mini-gaps with no pile-up.

500 ADC counts


Eff(excl) = 0.093 , 1.48/fb (139 +/- 8) /pb (6%)

36 bunch x bunch crossingsHave different luminositiesDistribution over a “period”Exclusive efficiencyExclusive efficiency x L(bunch)Integral = L_1(effective) – no PU


Very well fit by empirical function:F = 0.1 at M = 3.05F = 0.6 asymptotically

Single muon acceptance > 90% for pT > 1.5 GeV.Lower pT range out in calorimeters region. mass through rises )μA(μ


pppp

402 events

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

Paper in preparation


/J )2( S

x QED spectrum~ M0.852

QED A.eF Only normalization A floating

STARLIGHT & LPAIR MCsGood description: v.low pT

μμγ γ:continuum QED

pb 2.18:QED LPAIR & STARLIGHT

pb 0.52.6

)GeV/c4MGeV/c30.6,|η|σ(

:)μμσ(γγA22


J/ψ photoproduction(or possible odderon exchange)

Kinematics well described bySTARLIGHT MC

Much broader pT,dphi than



photoproduction(or possible odderon exchange)

Kinematics well described bySTARLIGHT MC

Much broader pT,dphi than

(2S)



Dissociation background:Take (90 +/- 10%) for eff (BSC)

...,,* etcnppp (10 +/- 3)%

Non-exclusive correction:QED: 0.91 +/- 0.05J/psi, psi’ 0.97 +/- 0.03

Indication of small non-exclusive b/g as not described by MC


)/(pand)(:J/ψonfitsKinematic T J Exclusive (<80 MeV)

20.034.0)combined( f

peak? J/ψ under the are γJ/ψχmany How c

Best fit is with ~ 1/3 but with very large uncertainty

Interpretations: (1) Large component (not supported by Method 2)(2) Decay simulations not precise (3) 1.5 sigma fluctuation(4) An odderon component (also larger )

c

)(J/pT


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

Good fits to mumu kinematics with only chi_c’s, if EM shower

cut MeV 80 above J/ψ cedphotoprodu No


EmEt spectrum with J/psi mass cut:

Empirical functional form:

TC.EBTT e.E.A)f(E

Fit shown (ET in MeV): A = 0.00025B = 2.5C = 0.0125 (per MeV)

Fraction under 80 MeV small:2.8 below 80 MeV (1% of J/psi)From varying A,B,C (1 +/- 1)%

& # chi_c = 68 +/- 8

Combine (1) and (2) : f = (1.9 +2.8 -1.9) %Total number of chi_c = 68.2 (65.2 are above 80 MeV cut)


Run,Evt: 220182.13272933M=3.101, pT=1.54, dphi=2.18

Note: CLC and BSC all empty although we did not require that.

CLC E empty CLC W empty

BSC empty

CENTRAL DRIFT CHAMBERCALORIMETERS: LEGO PLOT

/J


Summary of Results


Summary of Results

0.202)J/(B2,J),3516(

0.013)J/(B0,J),3415(

c

cAssumedSuppressed byJ_z=0 rule

nb 0.8)(3.0


Odderon O, C = -1 partner to IP … at least 3 gluons

In QCD but not yet observed.

Possibly O + IP & /J )2(' S

Search for Odderon exchange

Signature: Excess of exclusive & and Upsilons Yover rate expected from photoproduction (tuned to HERA data).t(p)-distribution would be flatter and henceVM should have larger <pT> andKinematic behavior different, but not well known. not known

)(

/J )2(' S


e.g. Schafer and Szczurek: arXiv:0705.2887 [hep-ph]

Some predictions for J/psi photoproduction:

Machado,Goncalves 3.0 nb

Khoze, Martin, Ryskin

Motyka and Watt: 3.4 nb

Schafer & Szczurek ~ 2.8 nb

Nystrand 2.2 nb

Our result: 3.96 +- 0.64 nb

Machado is considered too high by KMR

Tak

e 3.

0 +

- 0.

8

We are consistent, & sowe can put a limit on odderon exchange.If theory gets more precise, our limit can change


c.l.)%95(38.0

19.019.1)combined,(

21.015.1)'(

41.032.1)/(

VIP

VIPO

Vtheory

dataR

theory

dataR

Jtheory

dataR

015.0060.0)3415(

/)(

0

cIPIP

JIPO

Odderon Limits and ratios


Invariant Mass Distribution - Upsilon Region

Invariant Mass (nassoc_tracks = 0)pT(μμ) < 6GeV/c

CDF Run II Preliminary

CDF Run II PreliminaryTrigger: μ+μ- |η|<0.6 , pT(μ) > 4 GeV/c

Inclusive

Photo-production of Y, Y’(first observation in hadron-hadron)

Y(1S)

Y(2S)


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

R-z, Muon hitsLego, threshold ET > 10 MeV

Plugs, Miniplugs, CLC, BSC empty

M ~ 9.4 GeV


We have observed a candidate exclusive eventwith M ~ 64 GeV, which appears to be exclusive.

Run 166529 Event 10107956

Forward counters both sidesCLC and BSC were empty.Roman pot had pbar track

This is exactly the type of event for calibrating p(FP420)

GeV13.0)excluding(

GeV/c64~)( 2

TE

M

Search for Exclusive Z, and observe high mass lepton pairs.

Spectrum extends to M(ll) > 100 GeV!


FP420 : Forward Protons 420m downstream of CMS & ATLAS

CMS

CMS: Inner Vacuum Tank insertion

420 & 220m 220 & 420m||| ||| ||| |||ATLAS


Summary

bcJee ,,,',/,,

We have observed the following exclusive states X in p + X + pat the Tevatron with CDF:

These are all “first observations” for hadron-hadron “elastic”.(unless you call {A,Z} a hadron)

processes agree with QED predictions

Photoproduction of V agree with expectations & HERA.Hence limit on odderon exchange, near theory.

IP+IP c within theoretical uncertainties, and demonstratesthat exclusive H should happen, if H.

Furthermore, exclusive di-leptons provide a calibration of forward p – spectrometers, momentum scale and resolution


BACK UPS


μ)(eachη21 Cosmic rays would be at 0


H[ ](M ), s = 14 TeVpp p H p

What is exclusive H cross section?

H

Calculation involves:gg H (perturbative, standard, NLO)Unintegrated gluon densitiesProb.(no other parton interaction) (“Gap survival”)Proton form factorProb.(no gluon radiation no hadrons) Sudakov Suppression

( ). ( ')i ig x g x

Durham Gp: Khoze, Martin, Ryskin, Stirlinghep-ph/0505240 ++

~ 3 fb (M(H)=125 GeV)

“factor ~ 3 uncertainty”

30 fb^-1 ~ 100 Ae events(Ae = acceptance, efficiency)

But other estimates differby “large” amounts!Need to “calibrate” theory!

Exclusive

Mike Albrow FermilabISMD 2008, Sept 2008Central Exclusive Production at the Tevatron 1 Central...

Documents

Transcript of Mike Albrow FermilabISMD 2008, Sept 2008Central Exclusive Production at the Tevatron 1 Central...