Diffraction for all: from Tevatron to LHC and Beyond HEP 2006, December 11-15, Valparaiso, Chile Konstantin Goulianos The Rockefeller University Recent references Diffraction at the Tevatron: CDF results http://pos.sissa.it//archive/conferences/035/016/DIFF2006_016.pdf Renormalized diffractive parton densities http://pos.sissa.it//archive/conferences/035/044/DIFF2006_044.pdf
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Diffraction for all:from Tevatron to LHC and Beyond
HEP 2006, December 11-15, Valparaiso, Chile
Konstantin Goulianos
The Rockefeller University
Recent referencesDiffraction at the Tevatron: CDF resultshttp://pos.sissa.it//archive/conferences/035/016/DIFF2006_016.pdf
Renormalized diffractive parton densitieshttp://pos.sissa.it//archive/conferences/035/044/DIFF2006_044.pdf
HEP 2006, Chile, Dec 11-16 Diffraction for all K. Goulianos 2
ContentsIntroductionElastic and Total Cross SectionsDiffractionExclusive Production
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p-p InteractionsDiffractive:Colorless exchange with vacuum quantum numbers
Non-diffractive:Color-exchange
Incident hadrons retain their quantum numbersremaining colorless
pseudo-DECONFINEMENT
Incident hadrons acquire colorand break apart
CONFINEMENT
POMERON
Goal: understand the QCD nature of the diffractive exchange
rapidity gap
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Elastic Scattering
DIFFRACTION PATTERN
PROTON BEAM
TARGETPROTON
PROTON-PROTON ELASTIC SCATTERING
p p' dtdσ
2
π
)(p4
R
cGeV13b
m1R
e~bte~dtdσ 2
2
−
−
⎟⎠⎞
⎜⎝⎛≈⇒=
θ
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Diffraction DissociationRT
RL
M
P0
P0
Δ PT Δ PL,
m p
sM
PΔPξ
2
L
L ==
025.02
2
−=tdMdt
d σ
Momentum loss fraction
COHERENCE CONDITION 1.0
mm
p
≈< πξξ< 0.1
d
?M1~
dMdσwhyBut 22
Tevatron M 0.6 TeVLHC 4.4 TeV
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Rapidity Gaps
ξ1~
dξdσ
M
1~dM
dσconstantΔηddσ
220t
⇒⇒≈⎟⎟⎠
⎞⎜⎜⎝
⎛
=
p pX p
ξp
Particle production Rapidity gap
η
φ
-ln ξln MX2
ln s
X
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Diffractive pp Processes
η
φ
Elastic scattering Total cross section
SD DD DPE SDD=SD+DD
σT=Im fel (t=0)
OPTICALTHEOREM
η
φGAP
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Rapidity Gaps in Fireworks
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The PhysicsElastic and Total Cross Sections:……….pp pp and pp X
Fundamental Quantum MechanicsFroissart Unitarity Bound……….σT < C ln2s Optical theorem………………………..σT ~Im f(t=0)Dispersion relations………………....Re f(t=0)~Im f(t=0)Is space-time discrete? Measure σT and ρ-value at LHC!
One-gap cross sections are suppressedTwo-gap/one-gap ratios are 17.0=≈ κ
Central & Double-Gap CDF ResultsDifferential shapes agree with Regge predictions
10
10 2
10 3
10 4
10 5
10-6
10-5
10-4
10-3
10-2
10-1
1ξp
X
MX2
Num
ber
of E
vent
s pe
r Δl
ogξ
= 0
.1
Data
DPE MC
SD MC
DPE+SD MC
√s⎯
= 1800 GeV
0.035 ≤ ξ- p ≤ 0.095
| t- p | ≤ 1.0 GeV2
( GeV 2 )1 10 10
210
310
410
510
6CDF Preliminary
10
10 2
10 3
10 4
10 5
0 1 2 3 4 5 6 7
√s=1800 GeV
DATADD + non-DD MCnon-DD MC
Δη0=ηmax-ηmin
even
ts
10 2
10 3
10 4
10 5
0 1 2 3 4 5 6 7Δη0
exp=ηmax-ηmin
even
ts
√s=1800 GeVDATASDD + SD MCSD MC
DD SDD DPE
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Dark Energy
P(Δy) is exponentially suppressed
dydN
ρ,ey)P( particlesΔyρ ==Δ −
Rapidity gaps are formed bymultiplicity fluctuations:
Non-diffractive interactions
Δy2εe~0ty)P( =Δ
2lnlnln Msy −=−≈Δ ξ
Rapidity gaps at t=0 grow with Δy:
Diffractive interactions
2ε: negative particle density!
Gravitational repulsion?
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HARD DIFFRACTIONDiffractive fractionsDiffractive structure function
factorization breakdownRestoring factorizationQ2 dependencet dependenceHard diffraction in QCD
η
dN/dη
JJ, W, b, J/ψ
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All ratios ~ 1% ~ uniform suppression~ FACTORIZATION !
Diffractive Fractions @ CDF
gap)( ++→ Xpp
1.45 (0.25)J/ψ
0.62 (0.25)b
0.75 (0.10)JJ
1.15 (0.55)W
Fraction(%)Fraction:SD/ND ratioat 1800 GeV
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The diffractive structure function at the Tevatron is suppressed by a factor of ~10 relative to expectation from pdf’s measured by H1 at HERA
Similar suppression factor as in soft diffraction
relative to Regge expectations!
Diffractive Structure Function:Breakdown of QCD Factorization
CDF
H1
β = momentum fractionof parton in Pomeron
Using preliminary pdf’s from
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Restoring QCD Factorization
0.1 1
0.1
1
10
100
β
FD jj(β
)
from DPE/SD , 0.01 ≤ ξ ≤ 0.03
from SD/ND , 0.035 ≤ ξ ≤ 0.095
p
p
ND jetjet
0p
p
p
IP
SD jetjet
p
0
p
p
IP
IP
DPE jetjet
p p
η0ηp_ ηp
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
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Diffractive Structure Function:Q2 dependence
ETjet ~ 100 GeV !
Small Q2 dependence in region 100 < Q2 < 10,000 GeV2
Pomeron evolves as the proton!
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Diffractive Structure Function:t- dependence
No diffraction dipsNo Q2 dependence in slopefrom inclusive to Q2~104 GeV2
Fit dσ/dt to a double exponential:
Same slope over entire region of0 < Q2 < 4,500 GeV2
across soft and hard diffraction!
HEP 2006, Chile, Dec 11-16 Diffraction for all K. Goulianos 36
valence quarks
antiproton
x=ξ
Hard Diffraction in QCD
proton
deep sea
Derive diffractivefrom inclusive PDFsand color factors
antiproton
valence quarks
p
p
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EXCLUSIVE PRODUCTION
H
Measure exclusive jj & γγ Calibrate predictions for H production rates @ LHC
Bialas, Landshoff,Phys.Lett. B 256,540 (1991)Khoze, Martin, Ryskin,Eur. Phys. J. C23, 311 (2002); C25,391 (2002);C26,229 (2002)C. Royon, hep-ph/0308283B. Cox, A. Pilkington,PRD 72, 094024 (2005)OTHER…………………………
Search for exclusive dijets:Measure dijet mass fraction
Look for signal as Mjj 1
( )rscalorimeteallMM
RX
jjjj =
Search for exclusive γγ
3 candidate events found1 (+2/-1) predictedfrom ExHuME MC* background under study
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Exclusive Dijet Signal
b-tagged dijet fractionDijet fraction – all jets
Exclusive b-jets are suppressedby JZ= 0 selection rule
Excess over MC predictions at large dijet mass fraction
DIJETS
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RJJ(excl): Data vs MC
Shape of excess of events at high Rjjis well described by both models
ExHuME (KMR): gg gg processuses LO pQCD
Exclusive DPE (DPEMC)non-pQCD based on Regge theory
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jjexcl: Exclusive Dijet Signal
COMPARISONInclusive data vs MC @ b/c-jet data vs inclusive
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JJexcl : x-section vs ET(min)Comparison with hadron level predictions
ExHuME (red)Exclusive DPE in DPEMC (blue)
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JJexcl : cross section predictionsExHuME Hadron-Level Differential Exclusive Dijet Cross Section vs Dijet Mass (dotted/red): Default ExHuME prediction(points): Derived from CDF Run II Preliminary excl. dijet cross sections
Statistical and systematic errors are propagated from measured cross section uncertainties using ExHuME Mjj distribution shapes.
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Looking forward @ LHC
TOTEM/CMS ATLAS
FP420 project: http://www.fp420.com/Measure protons at 420 m from the IP during normal high luminosity running to be used in conjunction with CMS and ATLASFeasibility study and R&D for Roman Pot detector development
Physics aim :pp → p+ X + p (Higgs, New physics, QCD studies)Status: Project funded by the UK
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SummaryTEVATRON – what we have learntM2 – scalingNon-suppressed double-gap to single-gap ratiosPomeron: composite object made up from underlying pdf’s subject to color constraints
LHC - what to doElastic and total cross sections & ρ-valueHigh mass ( 4 TeV) and multi-gap diffraction Exclusive production (FP420 project)
Reduced bgnd for std Higgs to study propertiesDiscovery channel for certain Higgs scenarios