low x 2008, kolymbari-crete, greecediffractive and exclusive jj and w/z at cdf k. goulianos1...
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Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 1
Diffractive and Exclusive Productionof Dijets and W/Z at CDF
K. GoulianosThe Rockefeller University
and the CDF collaboration
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 2
A bit of history…Diffraction in the70s the Pomeron unveiled!
Opening night at Chez Leon - Fermilab (1989)
(right)Greg Snow on violin (Ph.D thesis: first observation of diffractive dissociation)
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 3
At the Gorge of Samaria (1980)
w/R. Feynman – a day of jokes!
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 4
Contents Introduction Dijets W/Z
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 5
Introduction
SD DD DPE SDD=SD+DD
pp
JJ, ee,
Soft and hard diffraction @ CDF
JJ, b, J/W
exclusive
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 6
SD kinematics
MX
,t
dN/d
p
MX
pp’
p’rap-gap
=-ln
0
Lpξ
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 7
Breakdown of factorization – Run I
~8
ZEUS and H1 vs. CDF
ξ
xβ H1
ZEUS
CDFKG, PLB 358 (1995) 379
1dtdξξ)(t,f0.1
ξ
IP/p
0
tmin
Tsd
~ 8
soft*e
pp p
pp
hard
Magnitude: same suppression factor in soft and hard diffraction!Shape of distribution: ZEUS, H1, and Tevatron – why different shapes?
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 8
All fractions ~ 1% (differences due to
kinematics) ~ uniform suppression ~ FACTORIZATION !
Hard diffractive fractions – Run I
dN/d
gap)( Xpp
1.45 +/- 0.25J/
0.62 +/- 0.25b
0.115 +/- 0.55W
0.75 +/- 0.10JJ
Fraction %Fraction:SD/ND ratio@ 1800 GeV
FACTORIZATION !
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 9
Multi-gap diffraction – Run I restoring factorization
R(SD/ND)
R(DPE/SD)DSF from two/one gap:factorization restored!
The diffractive structure function measured on the proton side in events with a leading antiproton is NOT suppressed relative to predictions
based on DDIS
w/preliminary pdf’s from
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 10
ξ
1
β
1~ξβ,FD
jj Pomeron dominated
constantdξ
dσincl
0.10.90.11.0
Djj ξ
1
β
1ξβ,F
& dependence of FDjj – Run I
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 11
Diffractive structure function – Run IIQ2 - dependence
ETjet ~ 100 GeV !
Small Q2 dependence in region 100<Q2<10 000 GeV2 where each dND/dET dND/dET vary by a factor of ~104
The Pomeron evolves as the proton !
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 12
Diffractive structure function – Run IIt - dependence
No diffraction dips No Q2 dependence in slope from inclusive to Q2~104 GeV2
Fit d/dt to a double exponential:
Same slope over entire region of 0 < Q2 < ~ 10 000 GeV2
across soft and hard diffraction!
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 13
Looks like…
… the underlying diffractive PDF on a hard scale is similar to the proton PDF except for small differences - presumably due to the requirement of combining with the soft PDF to form a spin 1 color singlet with vacuum quantum numbers.
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 14
Diffractive W/Z production
W, Z
p
p
p
IP
W, Z
p
p
pIP
Diffractive W production probes the quark content of the Pomeron– To leading order,
the W is produced by a quark in the Pomeron
Production by gluons is suppressed by a factor of S, and can be distinguished from quark production by an associated jet
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 1515
Diffractive W/Z - motivation
• In Run I, by combining diffractive dijet production with diffractive W production we determined the quark/gluon content of the Pomeron ===
• In Run II we aim at determining the diffractive structure function for a more direct comparison with HERA.
• To accomplish this we use: New forward detectors New methodology More data
Phys Rev Lett 78, 2698 (1997)Fraction of W events due to SD Rw=[1.15±0.51(stat)±0.20(syst) ]% for <0.1 integrated over t
DIS @ JJ
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 16
The DF II detectors
RPS acceptance ~80% for 0.03 < x < 0.1 and |t| < 0.1
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 17
The MiniPlugs @ CDF
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 1818
Using RPS information:
No background from gaps due to multiplicity fluctuations No gap survival probability systematics The RPS provides accurate event-by-event measurement Determine the full kinematics of diffractive W production by obtaining using the equation:
where
This allows the determination of: W mass
xBj
Diffractive structure function
νηTcalRPS es
Eξξ
Diffractive W/Z analysis
η
towers
Tcal es
Eξ
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 19
W/Z selection requirements
cm60|Z|
GeV120M40
GeV25M
GeV25(pE
vtx
WT
T
μT
eT
cm60|Z|
GeV116M66
GeV25(pE
GeV25(pE
vtx
Z
μ2T
e2T
μ1T
e1T
Standard W/Z selection
Diffractive W/Z selection RPS trigger counters - MIP RPS track - 0.03< <0.10, |t|<1 W 50 < MW(RPS,cal) < 120 Z cal < 0.1
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 2020
Reconstructed diffractive W mass
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 2121
Rejection of multiple interaction events
ND dijetw/soft SDoverlap
ND dijetw/soft SDoverlap
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 2222
Diffractive W/Z results
RW (0.03 < < 0.10, |t|<1)= [0.97 ± 0.05(stat) ± 0.11(syst)]%
Run I: RW =1.15±0.55 % for <0.1 estimate 0.97±0.47 % in 0.03 < < 0.10 & |t|<1)
RZ (0.03 < x < 0.10, |t|<1)= [0.85 ± 0.20(stat) ± 0.11(syst)]%
DØ Phys Lett B 574, 169 (2003) Rw=[5.1±0.51(stat)±0.20(syst)]%gap acceptance Agap=(0.21±4)%
uncorrected for Agap
RW=[0.89+0.19-0.17 ]%
RZ=[1.44+0.61-0.52 ]%
Stay connected tor results on FDW/Z
CDF PRL 78, 2698 (1997)Rw=[1.15±0.51(stat)±0.20(syst)]%gap acceptance Agap=0.81
uncorrected for Agap
Rw=(0.93±0.44)%
(Agap calculated from MC)
CDF/DØ Comparison – Run I (< 0.1)
EXCLUSIVE JJ& HIGGS BOSONS
22H )'pp'p(pM M~(1-2) GeV Determine spin of H
gap gap
b
b -jet
-jet
p p
H
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 24
Exclusive dijet and Higg production
H
DPEMC
ExHuME
URL: http://link.aps.org/abstract/PRD/v77/e052004 DOI: 10.1103/PhysRevD.77.052004
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 25
The DPE data sample
η
towers
TCALpbar e
s
Eξ
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 26
Kinematic distributions
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 27
Exclusive dijet signal
dijet mass fraction – all jets
Exclusive b-jets are suppressedas expected (JZ= 0 selection rule)
Excess observed over POMWIG MC prediction at large Rjj
b-jet dijet mass fraction
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 28
Underlying event
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 29
Jet1 vs. Jet2: signal and background regions
DATA
POMWIG
A: signal regionB: background region
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 30
Background region
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 31
Inclusive DPE W/LRG-p data vs. MC
Shape of excess of events at high Rjj
is well described by both ExHuME & DPEMC
ExHuME (KMR): gggg process (based on LO pQCD)
DPEMC: exclusive DPE MC based on Regge theory
Rjj
ExHuME DPEMCexclusive MC models
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 32
HF suppression vs. inclusive signal
HF suppression
Invert HF vertically and compare with 1-MC/DATA good agreement observed
HF vs. incl
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 33
ExHuME vs. DPEMC and vs. data
Measured x-sections favor ExHuME
KMR x 1/3 agrees with data Within theoretical uncertainty of +/- factor of 3
jjexcl/incl approx. independent of ET
min
WHY?
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 34
Exclusive dijet x-section vs. Mjj
curve: ExHuME hadron-level exclusive dijet cross sections vs. dijet mass
points: derived from CDF excl. dijet x-sections using ExHuMEStat. and syst. errors are propagated from measured cross section
uncertainties using Mjj distribution shapes of ExHuME generated data.
SUMMARYHIGGS ?
Introduction diffractive PDF looks like proton PDF
Diffractive W/Z – RPS data W diffractive fraction in agreement with Run I W/Z diffractive fractions equal within error New techniques developed to enable extracting the diffractive structure function in W production
Exclusive dijet/(Higgs?) production Results favor ExHuME over DPEMC Phys. Rev. D 77, 052004 (2008)
DIJET
W/Z
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 36
BACKUPMeasurements with the MiniPlugsDynamic alignment of RPS detectorsET
jet calibration
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 37
Measurements w/the MiniPlugs
ADC counts in MiniPlug towersin a pbar-p event at 1960 GeV.• “jet” indicates an energy cluster and may be just a hadron.• 1000 counts ~ 1 GeVMultiplicity of SD and ND events
ENERGY
MP TOWER
STRUCTURE
MULTIPLICITY
@ POSITION
NIM A 430 (1999)
NIM A 496 (2003)
NIM A 518 (2004)
s
eEΣξ
iηiTiCAL
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 38
Dynamic Alignment of RPS Detectors
Method: iteratively adjust the RPS X and Y offsets from the nominal beam axis until a maximum in the b-slope is obtained @ t=0.
Limiting factors
1-statistics2-beam size3-beam jitter
@ CDF W/lowlum data μm30
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 39
ETjet Calibration
Calibrate Etjet or , as you
wish!
use RPS information to check jet energy corrections
Low x 2008, Kolymbari-Crete, Greece Diffractive and Exclusive JJ and W/Z at CDF K. Goulianos 40
thank you