Post on 19-Dec-2015
transcript
Diffractive x-sectionsand event final states at the LHC
Konstantin GoulianosThe Rockefeller University
http://physics.rockefeller.edu/
Diffraction Day7 May 2010 CERN
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 2 K. Goulianos
Describe a phenomenology based on pre-LHC results and use it to: make predictions for LHC suggest measurements to confirm / modify parameters suggest scheme to be implemented in MC simulations propose method to measure luminosity
Current MC generators: unreliable for extrapolations to LHC MC tuning based on multi-parameter tuning of ill-defined
event topologies Solution: use nested x-sections
Contents define diffractive x-section event topologies
nested diffractive gaps describe in terms of proton pdf’’s and QCD color factors normalize to guarantee unitarity renormalization model
OUTLINE
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 3 K. Goulianos
REMARKS
MC generators inadequate:
e.g. PYTHIA and PHOJET predictions of diffractive processes disagree with each other and with data. Diffractive factorization at HERA? Breakdown observed in, e.g.
Vector mesons: vs. W, b-slopes of t-distributionsDijets: ET
jet dependence, resolved vs. direct components, . ..
RENORM model: describes both p(pbar)-p and p
Luminosity measurement: requires a known x-section
suggest SD – well defined and slowly varying
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 4 K. Goulianos
Diffractive pp(pp) processes @ CDF
Single Diffractiondissociation (SD)
Double Diffractiondissociation (DD)
Double PomeronExchange (DPE)
Central Diffraction
Single + DoubleDiffraction (SDD)
SD SD SD SDD
Elastic scattering Total cross sectionT=Im fel (t=0)
OPTICALTHEOREM
gap
nested gap
Use nesting until no diffractive gap fits in √s'
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 5 K. Goulianos
Definitions
s
Mξ-1
2
L x
22 M
1
dM
dσ
ξ
1
dξ
dσconstant
Δηd
dσ
0t
dN/d
M
pp’
p’rap-gap
=-ln0
p
M,t
p
p
p’ Lpξ
ln M2
ln s
particles
M2 scaling: no price paid for increasingdiffractive gap size
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 6 K. Goulianos
M2 scaling
KG&JM, PRD 59 (1999) 114017
factorization breaks down to ensure M2 scaling - why?
12
2
2 )(M
s
dM
d
Regge
1
Independent of s over 6 orders of magnitude in M2 !
ddM2|t=-0.05 independent of s over 6 orders of magnitude!
data
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 7 K. Goulianos
TSD (pp & pp)
Factor of ~8 (~5)suppression at √s = 1800 (540) GeV
suppressed relative to Regge
KG, PLB 358, 379 (1995)
1800
GeV
540
GeV
M,t
p
p
p’
TSD mb
√s=22 GeV
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 8 K. Goulianos
Gap probability MUST be normalized to unity!
Single Diffraction
yy
yt ,2 independent variables:
t
colorfactor
17.0)0(
)(
ppIP
IPIPIP tg
yoyt
p eetFCyddt
d
222
)(
gap probability sub-energy x-section
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 9 K. Goulianos
Single diffraction (re)normalized
yoyt
pgap eetFCNyddt
d
222
)(
s
sCdtydtyPsN s
gaptygap ln),()(
2
,1
tybsy eseCyddt
d )2()ln(2
0ln
Pumplin bound obeyed at all impact parameters
Grows slower than s
),( tyPgap
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 10 K. Goulianos
Unitarity and Renormalization
Two free parameters: s0 and gPPP
Obtain product gPPP•s0 from SD
Renormalized Pomeron flux determines s0
Get unique solution for gPPP
Pomeron-proton x-section
)(sσξ)(t,fdtdξ
σdpIPIP/p
SD2
0s
)(s /20 tgPPP
Pomeron flux gap probabilitySet to unity – determines gPPP and s0
KG, PLB 358 (1995) 379
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 11 K. Goulianos
Dijets in p at HERA from RENORM
Factor of ~3 suppressionexpected at W~200 GeV(just as in pp collisions)
for both direct and resolved components
K. Goulianos, POS (DIFF2006) 055 (p. 8)
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 12 K. Goulianos
Multi-gap Diffraction
1y 2y1y 2y
1y 2y
(KG, hep-ph/0205141)
y
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 13 K. Goulianos
Multi-gap Cross Sections
ssty ln/2~,
Same suppressionas for single gap!
2122
2-1i1
2
51
5
)( yyo
ytp
ii
eetFCdV
dii
Gap probability Sub-energy cross section(for regions with particles)
1y 2y1y 2y
1y 2y
1t 21 yyy 5 independent variables2t color
factor
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 14 K. Goulianos
Rapidity Gaps in Fireworks
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 15 K. Goulianos
Gap survival probability
0.23GeV)(1800S gapgap/01gapgap/12
0.29GeV)(630S gapgap/01gapgap/12
S =
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 16 K. Goulianos
Diffractive Structure Function
CDF
H1
momentum fraction of parton in “Pomeron” – note quotes
Using preliminary pdf’s from
same suppressionas in soft diffraction – why?
Xdijetppp
Breakdown of QCD factorization
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 17 K. Goulianos
Diffractive dijets @ Tevatron
),/(1
),,( 22
21 QQ xFxF D
pjet
reorganizep
jet
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 18 K. Goulianos
FDJJ(,Q2) @ Tevatron
2
sβ
ξ
dξN
ε
ε
2sβ
1
β
xξ1
ξ 211
renorm
minmin
min
)2(
)(1
12
2R
2RENORM
xQs
xSDND
4.02.0 xg
)()(renorm
22
2
2
2 )(12
)/(
)(1N),,( 21221 Q
Q
Q
C
sx
CF D
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 19 K. Goulianos
SD/ND dijet ratio vs. xBj@ CDF
(x)F
(x)FR(x) ND
jj
SDjj
0.035 < < 0.095
Flat dependencefor < 0.5
CDF Run I
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 20 K. Goulianos
Diffractive DIS @ HERA
),(1
),,( 221
2)3(2 QQ xFxF D
eQ2*
p
jet
reorganize
J. Collins: factorization holds (but under what conditions?)
e*
tp
IP
Pomeron exchange Color reorganization
Results favor color reorganization
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 21 K. Goulianos
Dijets in p at HERA - 2008
DIS 2008 talk by W. Slomiński,
ZEUS
20-50 % apparent rise when ETjet 510 GeV
due to suppression at low ETjet !!!
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 22 K. Goulianos
Vector meson production(Pierre Marage, HERA-LHC 2008)
left - why different vs. W slopes? more room for particles right - why smaller b-slope in *p? same reason
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 23 K. Goulianos
Unexpected, notunderstood
QCD factorisationnot OK
Dijets in p at HERA – 2007
Hadron-like
eQ2*
p
jet
reorganize
Direct vs. resolved
the reorganization diagram predicts:
suppression at low Z|Pjets, since larger is available for particles
same suppression for direct and resolved processes
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 24 K. Goulianos
SD and ratio of '
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 25 K. Goulianos
The total x-section
√sF=22 GeV
SUPERBALL MODEL
D-day 7 May 2010 CERN Diffractive x-sections and event final states at the LHC 26 K. Goulianos
Strategy and Conclusion
T from SUPERBALL model optical theorem Im fel(t=0) dispersion relations Re fel(t=0) differential SD from RENORM use nested pp multiplicities forpomeron-proton collisions at √s‘ For a phenomenological approach see: K. Goulianos, Phys. Lett. B 193 (1987) 151 pp
T
optical theoremIm fel(t=0)
dispersion relationsRe fel(t=0)
STRATEGY
CONCUSIONmore to come…