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![Page 1: Diffraction, saturation, and pp cross-sections at the LHC Diffraction, saturation and pp cross sections at the LHC Konstantin Goulianos The Rockefeller.](https://reader031.fdocuments.us/reader031/viewer/2022032704/56649d485503460f94a23e53/html5/thumbnails/1.jpg)
Diffraction, saturation, and pp cross-sections at the LHC
Diffraction, saturation andpp cross sections at the LHC
Konstantin GoulianosThe Rockefeller University
Moriond QCD and High Energy InteractionsLa Thuile, March 20-27, 2011
(member of CDF and CMS)
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 2 K. Goulianos
CONTENTS
Introduction
Diffractive cross sections
The total, elastic, and inelastic cross sections
Monte Carlo strategy for the LHC
Conclusions
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 3 K. Goulianos
Two reasons: one fundamental / one practical.
fundamental
practical: underlying event (UE), triggers, calibrations
the UE affects all physics studies at the LHC
Why study diffraction?
T
optical theoremIm fel(t=0)
dispersion relationsRe fel(t=0)Diffraction
measure T & -value at LHC:
check for violation of dispersion relations
sign for new physics Bourrely, C., Khuri, N.N., Martin, A.,Soffer, J., Wu, T.T
http://en.scientificcommons.org/16731756
saturation T
NEED ROBUST MC SIMULATION OF SOFT PHYSICS
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 4 K. Goulianos
Pandora's box is an artifact in Greek mythology, taken from the myth of Pandora's creation around line 60 of Hesiod's Works And Days. The "box" was actually a large jar (πιθος pithos) given to Pandora (Πανδώρα) ("all-gifted"), which contained all the evils of the world. When Pandora opened the jar, the entire contents of the jar were released, but for one – hope. Nikipedia
MC simulations:Pandora’s box was unlocked at the LHC!
Presently available MCs based on pre-LHC data were found to be inadequate for LHC MC tunes: the “evils of the world” were released from Pandora’s box at the LHC
… but fortunately, hope remained in the box
a good starting point for this talk
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 5 K. Goulianos
Diffractive gapsdefinition: gaps not exponentially suppressed
ξ
1~
dξ
dσ
M
1~
dM
dσconstant
Δηd
dσ22
0t
p pX p
Particle production Rapidity gap
-ln ln MX2
ln s
X
No ra
diat
ion
Lpξ
sM
ξ2x
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 6 K. Goulianos
Diffractive pbar-p studies @ CDF
Elastic scattering Total cross section
SD DD DPE SDD=SD+DD
T=Im fel (t=0)
OPTICALTHEOREM
GAP
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 7 K. Goulianos
Basic and combineddiffractive processes
a 4-gap diffractive process
gap
SD
DD
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 8 K. Goulianos
Regge theory – values of so & g?
Parameters: s0, s0' and g(t) set s0‘ = s0 (universal IP ) determine s0 and gPPP – how?
KG-1995: PLB 358, 379 (1995)
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 9 K. Goulianos
A complication … Unitarity!
d/dt sd grows faster than t as s increases unitarity violation at high s
(similarly for partial x-sections in impact parameter space)
the unitarity limit is already reached at √s ~ 2 TeV
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 10 K. Goulianos
TSD vs T (pp & pp)
Factor of ~8 (~5)suppression at √s = 1800 (540) GeV
KG, PLB 358, 379 (1995)
1800
GeV
540
GeV
M,t
p
p
p’
√s=22 GeV
RENORMALIZATION MODEL
CDF Run I results
TT
suppressed relative to Regge for √s>22 GeV
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 11 K. Goulianos
Gap probability (re)normalize to unity
Single diffraction renormalized – (1)
yy
yt ,2 independent variables:
t
colorfactor
17.0)0(
)(
ppIP
IPIPIP tg
yoyt
p eetFCyddt
d
222
)(
gap probability sub-energy x-section
KG EDS 2009: http://arxiv.org/PS_cache/arxiv/pdf/1002/1002.3527v1.pdfKG CORFU-2001: hep-ph/0203141
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 12 K. Goulianos
Single diffraction renormalized – (2)
colorfactor
17.0)0(
)(
ppIP
IPIPIP tg
Experimentally: KG&JM, PRD 59 (114017) 1999
18.03
125.0
8
175.0
121f
1
1f
2
Q
NN cq
cgQCD:
104.0,02.017.0
pIP
IPIPIPg
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 13 K. Goulianos
Single diffraction renormalized - (3)
constsb
sssd
ln
ln~
set to unity determine so
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 14 K. Goulianos
Single diffraction renormalized – (4)
yoyt
pgap eetFCNyddt
d
222
)(
s
sCdtydtysN s
gaptygap ln),(P)(
2
,1
tybsy eseCyddt
d )2()ln(2
0ln
Pumplin bound obeyed at all impact parameters
grows slower than s
),(P tygap
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 15 K. Goulianos
M2 distribution: data
KG&JM, PRD 59 (1999) 114017
factorization breaks down to ensure M2 scaling
ε12
2ε
2 )(M
s
dM
dσ
Regge
1
Independent of s over 6 orders of magnitude in M2
M2 scaling
ddM2|t=-0.05 ~ independent of s over 6 orders of magnitude!
data
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 16 K. Goulianos
Scale so and triple-pom coupling
Two free parameters: so and gPPP
Obtain product gPPP•so from SD
Renormalized Pomeron flux determines so
Get unique solution for gPPP
Pomeron-proton x-section
)(sσξ)(t,fdtdξ
σdp/p
SD2
IPIP
os
)(s /2o tgPPP
Pomeron flux: interpret as gap probabilityset to unity: determines gPPP and s0 KG, PLB 358 (1995) 379
So=3.7±1.5 GeV2gPPP=0.69 mb-1/2=1.1 GeV -1
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 17 K. Goulianos
Saturation “glueball” at ISR?
See M.G.Albrow, T.D. Goughlin, J.R. Forshaw, hep-ph>arXiv:1006.1289
Giant glueball with f0(980) and f0(1500) superimposed, interfering destructively and manifesting as dips (???)
√so
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 18 K. Goulianos
Multigap cross sections, e.g. SDD
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
KG, hep-ph/0203141
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 19 K. Goulianos
SDD in CDF: data vs NBR MChttp://physics.rockefeller.edu/publications.html
Excellent agreement between data and NBR (MinBiasRockefeller) MC
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 20 K. Goulianos
Multigaps: a 4-gap x-section
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 21 K. Goulianos
The total x-section
√sF=22 GeV
SUPERBALL MODEL
98 ± 8 mb at 7 TeV109 ±12 mb at 14 TeV
http://arxiv.org/abs/1002.3527
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 22 K. Goulianos
Total inelastic cross section
ATLAS measurementof the total inelastic x-section
Renormalization model
The el is obtainedfrom t and the ratio of el/tot
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 23 K. Goulianos
SD and ratio of '
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 24 K. Goulianos
Diffraction in PYTHIA -1
some comments: 1/M2 dependence instead of (1/M2)1+
F-factors put “by hand” – next slide Bdd contains a term added by hand - next slide
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 25 K. Goulianos
Diffraction in PYTHIA -2
note: 1/M2 dependence e4 factor
Fudge factors: suppression at kinematic limit kill overlapping diffractive systems in dd enhance low mass region
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 26 K. Goulianos
CMS: observation of Diffraction at 7 TeVAn example of a beautiful data analysis and of MC inadequacies
• No single MC describes the data in their entirety
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 27 K. Goulianos
Monte Carlo Strategy for the LHC
T from SUPERBALL model optical theorem Im fel(t=0) dispersion relations Re fel(t=0) el
inel
differential SD from RENORM use nesting of final states (FSs) forpp collisions at the IP p sub-energy √s'
Strategy similar to that employed in the MBR (Minimum Bias Rockefeller) MC used in CDF based on multiplicities from: K. Goulianos, Phys. Lett. B 193 (1987) 151 pp“A new statistical description of hardonic and e+e− multiplicity distributions “
T
optical theoremIm fel(t=0)
dispersion relationsRe fel(t=0)
MONTE CARLO STRATEGY
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 28 K. Goulianos
Monte Carlo algorithm - nesting
'ct
Profile of a pp inelastic collision
y‘ < y'min
EXIT
y‘ > y'min
generate central gap
repeat until y' < y'min
ln s' evolve every cluster similarly
gap gapno gap
final statefrom MC w/no-gaps
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 29 K. Goulianos
SUMMARY
Introduction
Diffractive cross sections
basic: SDp, SDp, DD, DPE
combined: multigap x-sections
ND no-gaps: final state from MC with no gaps
this is the only final state to be tuned
The total, elastic, and inelastic cross sections
Monte Carlo strategy for the LHC – use “nesting”
derived from NDand QCD color factors
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 30 K. Goulianos
BACKUP
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 31 K. Goulianos
RISING X-SECTIONS IN PARTON MODEL
(see E. Levin, An Introduction to Pomerons,Preprint DESY 98-120)
ses oy
oT )(y
sy ln
Emission spacing controlled by -strong
: power law rise with energy
s
’ reflects the size of the emitted cluster,
which is controlled by 1 /s and thereby is related
to
ytel etsf ),(Im
y sy ln
Forward elastic scattering amplitude
assume linear t-dependence
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 32 K. Goulianos
Gap survival probability
0.23GeV)(1800S gapgap/01gapgap/12
0.29GeV)(630S gapgap/01gapgap/12
S =
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 33 K. Goulianos
Diffraction in MBR: dd in CDFhttp://physics.rockefeller.edu/publications.html
renormalized
gap probability x-section
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 34 K. Goulianos
Diffraction in MBR: DPE in CDFhttp://physics.rockefeller.edu/publications.html
Excellent agreement between data and MBR low and high masses are correctly implemented
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 35 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)
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 36 K. Goulianos
Saturation at low Q2 and small-x
figure from a talk by Edmond Iancu
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Moriond QCD 2011 Diffraction, saturation, and pp cross sections at the LHC 37 K. Goulianos
The end