exclusive central production in cdf (from talk to cdf cm, apologies for obvious to you)

1Mike Albrow FP420 Meeting, 6/20/09 Exclusive Central Production in CDF

Exclusive Central Production in CDF (From talk to CDF CM, apologies for obvious to you)

pXppp

where X is a simple state fully measured, and no other particles produced. (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 examples ...,

~~,,, llWWHhX

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

In CDF, 5 PRLs:(M, GeV range) 80)/Z(40ll,χψ(2S),J/ψ/4),(3μμX

30)JJ(10),γγ(40),(10ee

c0


A bit of history:To show that σ(p+H+p) wasuncertain by a factor > 1000in 2000

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

pJJppp

pppp

pppp

pppp

b

c

* Now measured in CDF*

*

*


pJJppp

pppp

pppp

pppp

b

c

Cleanest (no S.I.) but smallest σ

KMR: 38 pb in our box). 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!See next slide.

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

0


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

36 fb

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

& much smallerqq

Exclusive 2-Photon Production

Tevatron

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

H

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

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

3 candidates, 2 golden12Note : 2 10 !MEAS INEL

New data, Lower threshold, probable “observation”(Erik Brucken)


5

c0c

J/ψ

γ

μ+

μ-

& nothing elsein all CDF

-7.4 < |η| < + 7.4Beam Shower Counters BSC:Scintillator paddles tightly wrapped around beam pipes.Detect showers produced in beam pipes if p or p dissociate.e.g. 8 + 10 counters

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.

pp

4.7||2.5

CDFcentral

BSC (size greatly exaggerated!)

- 50 m

CDF measurement of exclusive c J/ψ + → μ+μ-


c has small pT, and so do muons: Trigger = 2 muons + BSC veto.pT(μ) >~ 1.4 GeV to escape calorimetry.M(μμ) <~ 4 GeV imposed by trigger rate (no prescale)

Offline required μ+μ- or μ+μ- and nothing else.Found most μ+μ- had no photon.

500

100 1000 counts

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

0cc

pppp

2μμ

2 GeV/c 4MGeV/c3

pppp

Exclusive production (CDF)0c


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

pppp


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

Some predictions for J/psi photoproduction: Machado,Goncalves 3.0 nbMotyka and Watt: 3.4 +- 0.4 nbSchafer & Szczurek ~ 2.8 nbNystrand 2.7+0.6-0.2 nb

Our result: 3.92 +- 0.62 nbTak

e 3.

0 +

- 0.

3Y is much lower.Allow Pile-Up (x 10)More data (x 3)More Δy (x >4)

(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

Our limits on O-exchange are close to,and constrain, theoretical predictions

nb 0.46:Theory

nb 0.140.53 :CDF

:)]2('[|

0.110.04

0

Sdy

dy


Now allow photons: EmEt spectrum with J/ψ mass cut:

Empirical functional form

MC also estimates only few % of under the cut

(But CDF SIMulation is not reliable for such low ET)

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


)/(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


Summary of Results pppp M = 3-4 GeV/c2

No strong evidence for odderon

90 nb(χ width)Durham

(IP)p(γγp TT


PDG 2008 (latest):

Could exclusive central production be a valuable lab for decays?


Dimuons: Upsilon Region

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

CDF Run II Preliminary

CDF Run II Preliminary

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

Inclusive

Search for/measurement ofphotoproduction of Y, Y’(not before seen in hadron-hadron)

Status:analysis in progress.QED continuum checkY : cf HERA (we resolve states)Can we see ?

Y(1S)

Y(3S)

Y(2S)

γΥχ b


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

R-z, Muon hits

Plugs, Miniplugs, CLC, BSC empty

M ~ 9.4 GeV

But will allow P-U,(except for b Y + search)


b at Tevatron and LHC nb, “O.M.”

hep-ph/0403218

MeV 777p)%;0.11.7()1S(:2J)10269(

MeV 242p)%;4.22.16()S2(:2J)10269(

MeV 743p)%;6.09.0()S1(:0J)10232(

MeV 207p)%;1.26.4()S2(:0J)10232(

MeV 442p)%;422()S1(:2J)9912(

391MeVp?);%5.3(~%6)S1(:0J)9859(

:states20and00JIχ

γb2

γb2

γb0

γb0

γb2

γb0

PCGb

Complex spectrum of radiativedecays to Y(1),Y(2):

Here just give DPE allowed states(J=0 >> J=2)

ds/dy(KMRS,TeV) = 200 pbIf BR = 4% (?) that’s 8 pb ->gY1Cf ~ 10 pb for ds/dy(Y1)ds/dy(KMRS, LHC) = 600 pbIf BR = 4% (?) that’s 24 pb ->gY1cf ~ 30 pb for ds/dy(Y1)

Will not get good Y cross sections without knowing , and p-calibration screwed up. “Soft” photons important.

b


Y: Predictions from Motyka and WattarXiv:0805.2113

Phys.Rev.D78:014023,2008.

W)&(M pb)145())1((| 0 Ydy

dy

(CDF)nb)62.092.3()/(| 0 J

dy

dy

Other predictions:12 +- 1 pb (Cox,Forshaw,Sandapan)~12 pb (Klein & Nystrand)0.8 – 5 – 9 pb (Bzdak,Motyka,Szymanowski & Cudell)

HERA data not much help:Resolution confuses Y1,2,3, low statistics

Factor ~ 400

CDF Run II


A. Szczurek: arXiv:0811.2488

/J

)2(' S

)1( S

)2( S

~ 30 pb


… and more so as M increases. CDF QED data:

M(mumu) = 3 – 4 GeV/c20.34 (rad) efficient.

M(ee) = 10 – 30 GeV/c20.08 (rad) efficient.

M(ll) = 40 – 76 GeV/c20.02 (rad) efficient.

)GeV/c(

rad)(1.12

M

is a good empirical fit to these QED data cuts.

0.13 for 8 – 9.2 GeV/c20.10 for 10.5 – 12 GeV/c2

How does resolution in compare CDF-ATLAS/CMS ?

QED γγ→l+ l-


M(ll) > 40 GeV/c2pT < 1.1 GeV/c efficient

M(mumu) = 3 – 4 GeV/c2pT < 0.3 GeV/c efficient.(- 3 outliers)

M(e+e-) = 10-30 GeV/c2pT < 1.6 GeV/c efficient.

pT(l+l-) cut dominated by detector resolution (so CDF not ~ CMS)True pT (Coulomb pair) < ~ 0.1 GeV/c.Looking at CDF data (small statistics in tail):

pT <~ 1.0 GeV/c2 should be efficient for 8 – 12 GeV/c2 region(a priori).

QED:


Photoproduction of vector mesons: larger

pT <~ 1 GeV/c efficient( - outliers)

< ~ 0.65 efficient

andpT

J/psi

psi(2S)

<~ 0.22 for Y(1)


Next steps:Full data set (~ x 2-3).Separate data in mass bands: QEDlow, Y1,Y2,Y3, QEDhigh, QED veryhigh.

Check all distributions & confirm cuts.Simulate generation and CDF detector Acceptance x efficiencyCross sections {& no dependence on L(instantaneous)?}

CDF Lumi calibration has ~ 6%. Can these QED events help improve it?? (Marginal, but test bed for LHC)

The Y1 Y2 and Y3 photoproduction cross sections could be better than HERA (resolution & statistics). Odderon contribution? Information on dipole-proton scattering, g(x1,x2), S^2 etc. But:

From “final” sample, select no pile-up clean events (~ 15%)Allow EM showers, look for: b

b


What about LHC and FP420 ?

The best tests of

)(

and)(

are)(

pppp

pppp

pHppp

b

These can probably only be done with no pile-up, orjust possibly with just 1 or 2 min-bias events (? … could try)Early days with low luminosity/bunch crossing:<n_inel> < ~ 3 Exclusive 2+3 EM showers can give us these.

pllppp

pllppp

)(

and

These will practice calibration of FP420 spectrometers(momentum scale and resolution).Y’s higher rate than QED. Want forward pairs for acceptance.


Level 1:2 EM clusters > 4 GeV (E or ET?) + Forward gapsLittle (<~ 4 GeV, or noise + x) E (ET?) in all hadron calorimeters.(In CDF this trigger worked with no prescale and no L2,L3.)

Higher level: Cleaner forward gaps, 1 vertexShould get low rate (<~ 0.1/s?) with no prescale.

Two muons with pT > 4 GeV/c and Forward gaps as well, want both

3~||

Key is good trigger in early:

Cross section at LHC Y, chi+b, QED,

FORWARD SHOWER COUNTERS: FSC


Y and FP420 at LHCPredictions from Motyka and WattarXiv:0805.2113

Phys.Rev.D78:014023,2008.

Large uncertainty in extrapolation.No gap survival probability!

leptons

T ep )()2(1

FP420 acceptance?

(most likely kinematics)

2121 ;GeV/c75.4TT pp

.)(max vsp

5.2 5

420

220

)(min p is always much too small to see.Fortunately each xi(p) is known


Photon “beams” radiated from electrons and protonsLEP etc: e+e- (~ background free)HERA: e p (more background, little done)pp/ ppbar: Very high b/g … Seen in CDF γ

e,p

ee

Phys.Rev.Lett 98,112001(2007)

2GeV/c)μM(μ

μμ

μμeeμμ

inel12σ103~pb0.24~σ

Tevatron as a collider!

PRL 102, 242001 (2009)


E not ET!

CLC BSC

M(ee) = 49.3 GeV/c2 |Δφ-π| = 6 mrad = 0.34 deg, pT(ee) = 210 MeV

M reach Tevatron >~ HERA, LEP !pb 0.256QED cf

pb 24.0

4||,GeV/c40

μμor )(

(LPAIR)

13.010.0

2

M

peeppp


Emily)(by LPAIRTeV,1.96sat

(max)||differentfor )(minM.vs

)( QED

pppp

Curves hand-drawn by me!No apologies for the quality!Can “read off” cross sectionFor any M_min orM-range, and eta(max).

Handy graph

√s = 1.96 TeV


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 (inaccessible).

Possibly best possible 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 LHC


LPAIR cross sections at LHC (Emily Nurse):

Have at Tevatron and LHC(14)(M in GeV):

4.2min

2.2max

minmaxmin )25.1480(~),(M

MM

Useful look up.


Exclusive Z production : CDF SearchAllowed in SM (like V)but ~ 0.3 fb (Motyka+Watt)

Could be enhanced by BSM loops

2.2/fb : 318K μμ&ee M > 40 GeV; 183K in Z window 82-98 GeVRequire no other interaction, no additional tracks, all calorimeters in noise (E)

8 with BSC empty

Interesting?!-IP-Z eff.coupling.ZOOM IN to see how!

LHC) @ (13fb

0.3fbTheory )σ(Z

C.L.) (95% pb 0.96)σ(Z

excl

excl

~ record E()

Search in “no-PU” events. Have 10 x data if PU allowed.


31

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


SummaryIn p + p →p + X + p, t-channel exchanges only γ, {gg} (IP), or {ggg}(O) in L.O.

O has not been observed; we give best limitQED process (a) seen in e+e- and μ+μ-, M = 3 – 75 GeV/c2

In hadron+hadron, only CDF.Photoproduction (b) seen J/ψ, ψ’, Y(prelim), Z limit (only CDF)

Exclusive gg →χc measured, Excl.H must happen, σ constrained

Exclusive γγ candidates, and exclusive JJ support some theoretical calculations, refute others.

(a) (b) (c)

Best estimates now σ(p+p →p + SMH + p) ~ 1 – 10 fb @ LHCFeasible with v. high precision (space and time) p-detectors

exclusive central production in cdf (from talk to cdf cm, apologies for obvious to you)

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