cern 26-27 march 2004hera and the lhc: diffractive gap probability k. goulianos1 hera and the lhc k....
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CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 1
HERA and the LHC
K. Goulianos, The Rockefeller UniversityCERN 26-27 March 2004
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 2
Diffractive signatures
Leading hadron(s) Rapidity gap(s)
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 3
Leading hadrons
X
Diffractiondissociation
025.0dMdt
σ2
2
dt
1
~
dt
dσ
KG, Phys. Rep. 101 (1983) 171
LL/PΔPξ
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 4
Rapidity gapsMinimum bias Diffraction
dissociation
Gaps exponentially suppressed
From Poisson statistics:
dy
dnρey)P( Δyρ
2lnlnln Msy
constantdy
dσ
M
1~
dM
dσ22
MX
gap
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 5
QCD aspects of diffraction Quark/gluon exchange across a rapidity gap:
POMERON
No particles radiated in the gap:
the exchange is COLOR-SINGLET with vacuum quantum numbers
Rapidity gap formation: NON-PERTURBATIVE
Diffraction probes the large distance aspects of QCD:
POMERON CONFINEMENT
PARTONIC STRUCTURE FACTORIZATION PROPERTIES
?
MX
gap
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 6
History of Diffraction
1960 Good and Walker 1960’s BNL: first observation
1970’s Fermilab fixed target, ISR, SPS 1983 KG, Phys. Rep. 101, 169 (1983)
1992 UA8: diffractive dijets hard diff 1993-2003 Golden decade: HERA, Tevatron,
RHIC
40 years of diffraction
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 7
SOFT DIFFRACTION
Soft and Hard Diffraction HARD DIFFRACTION
=PL/PL =fractional momentum loss of scattered (anti)proton
Variables: (, t) or (,
t)
Additional variables: (x, Q2)
seExjet
T
jetBj /
22 )(, jetTEQx
dN/d
MX
=-lnt
dN/d
ln MX2
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 8
Breakdown of QCD factorization
dN/dgap
e*
HERA TEVATRON
dN/dgap
p
ppIPt
),( 22 xQF
),,,( 22 tQF D ),,,( tEF Jet
TDJJ
),( xEF JetTJJ
CDF
H1
p
ppIP
pIP
XXX
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 9
Diffractive vs inclusive structure fn’s
F2D(x,Q2) /F2(x,Q2)
FDJJ(x,Q2) /F(x,Q2)
x),2F(Q
ξ)x,,2(QDFR
~ no Q2 dependence~ flat at HERA~ 1/x0.5 at Tevatron
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 10
CDF Run I results
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 11
Unitarity problem: With factorization and std pomeron flux SD exceeds T at
Renormalization: normalize the pomeron flux to unity
Soft Diffraction)(Mσξ)(t,f
dtdξ
σd 2XpIPIP/p
SD2
MX
KG, PLB 358 (1995) 379
TeV.2s
1dtdξξ)(t,f0.1
ξ
IP/p
0
tmin
~10
2~ sSD
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 12
A Scaling Law in Diffraction
KG&JM, PRD 59 (1999) 114017
Factorization breaksdown in favor of
M2-scaling
12
2
2 )(M
s
dM
d
renormalization
1
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 13
Double Diffraction Dissociation
One central gap
Double Pomeron Exchange
Two forward gaps
SDD: Single+Double Diffraction Forward + central gaps
Central and Double Gaps
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 14
Elastic & total
yooT ess )(
2),( ytel ets
y
y
sy ln
sy ln
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 15
yy
yt ,2 independent variables:
yoyt
p eetFCyddt
d
2
12
2
)(
Gap probability
ye 2~ 22ln
minsyssy
y
Renormalization removes the s-dependence SCALING
Generalized renormalization (KG, hep-ph/0205141)
colorfactor
17.0)0(
)(
ppIP
IPIPIP tg
t
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 16
The factors and
18.03
125.0
8
175.0
1w
1
1w 0
2
2
Q
cq
cg NN
Experimentally:
02.017.0pIP
IPIPIPg
Color factor:
KG&JM, PRD 59 (114017) 1999
12.0ww qqgg
λx
1f(x)x
g=0.20
q=0.04
R=-0.5
Intercept:
wg=gluon fractionwq=quark fraction
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 17
colorfactor
1y 2y1y 2y
1y 2y
2t1t 21 yyy 5 independent variables
2122
2-1i1
2
51
5
)( yyo
ytp
ii
eetFCdV
dii
Gap probability Sub-energy cross section(for regions with particles)ye 2~
Two-Gap Diffraction (KG, hep-ph/0205141)
22ln
minsyssy
y
Same suppressionas for single gap!
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 18
Differential shapes agree with Regge predictions
One-gap cross sections are suppressed
DD SDD DPE
Two-gap/one-gap ratios are 17.0
Central & Double-Gap Results
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 19
Soft Double Pomeron Exchange
ieEs
iTp
particlesall
1
Roman Pot triggered events
0.035 < -pbar < 0.095
|t-pbar| < 1 GeV 2
-proton measured using
Data compared to MC based
on Pomeron exchange with
Pomeron intercept =0.1
Good agreement over 4 orders of magnitude!
2pbar
pbar
GeV1||
095.0035.0
GeV1800
t
s
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 20
Soft gap survival probability
0.23GeV)(1800S gapgap/01gapgap/12
0.29GeV)(630S gapgap/01gapgap/12
S =
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 21
Hard Diffraction & QCD
• The diffractive structure function measured using SD dijets at the Tevatron is suppressed by about an order of magnitude relative to predictions based on diffractive DIS at HERA
• The discrepancy is generally attributed to additional color exchanges which spoil the diffractive rapidity gap.
~10
Factorization Breakdown
XJetJetppp Diffractive structure function
HERA
Tevatron
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 22
Double-Gap Hard Diffraction @TEV vs HERA
R(SD/ND)
R(DPE/SD)
DSF from double-gapsDSF from single-gaps
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 23
Diffractive structure functionfrom inclusive pdf’s (KG)
Power-law region
max = 0.1xmax = 0.1 < 0.05
xxfx
1)(
g=0.20
q=0. 04
R=-0.5
g =0.5
q =0.3
CAC
xFxF NORM
Q
QQQ
D 1)(1
21
22
2
)(
)(1),(
1),,(
)(2 constant,:) (noHERA 2fixedRENORM QDDIS
DDISDISR
)(JJ
R:(RENORM)TEVATRON
xND
SD
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 24
Pomeron Intercept from H1
RENORM
1+
ttIP 1)(
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 25
Pomeron intercept from ZEUS
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 26
Gap between jets
jet???gap ΔyΔy Question
gapΔyjetΔy
5%1%/0.2/SR)s(R JGJTEV
JGJLHC
JetGapJetpp
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 27
Exclusive Dijets in DPEInterest in diffractive Higgs production Calibrate on exclusive dijets
Dijet mass fraction
X
conejj
jj M
MR
pb10534GeV25
pb27265970GeV10
0.8)(RσE jjjjexcl
DPEjetT
Upper limit for excl DPE-jjconsistent with theory
no peak!
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 28
Exclusive c Production in DPE pγ)J/ψ(χppp c
Cross section upper limit comparable to KMR prediction
CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos 29
Summary
M2 – scaling
Non-suppressed double-gap to single-gap ratios
Flavor-independence SD/ND ratio
Get diffractive from non-diffractive pdf’s
SOFT DIFFRACTION
Universality of gap prob. across soft and hard diffraction
HARD DIFFRACTION