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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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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
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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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
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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
CDF Forward Detectors:
BSC 1 BSC 2,3,4
CLCCherenkov Luminosity Counters
MINIPLUG
BSC very important as rap gap detectors.
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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 20109
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
)/(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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
Thank You
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Mike Albrow Exclusive production in CDF Diffraction Trento Jan 2010
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.
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