NLO QCD analysis of single- diffractive dijet production at the Tevatron Michael Klasen (LPSC Grenoble) in collaboration with G. Kramer (U Hamburg) April 20, 2010 Phys. Rev. D 80 (2009) 074006
Jan 15, 2016
NLO QCD analysis of single-diffractive dijet production at the
Tevatron
Michael Klasen (LPSC Grenoble)in collaboration with G. Kramer (U Hamburg)
April 20, 2010
Phys. Rev. D 80 (2009) 074006
April 20, 2010 Michael Klasen, LPSC Grenoble 2
Publications
With G. Kramer
PLB 508 (2001) 259: p 2 jets+n
EPJC 38 (2004) 39: p 2 jets+p
PRL 93 (2004) 232002: p 2 jets+p
JPG 31 (2005) 1391: New fact. scheme
EPJC 49 (2007) 957:p 2 jets+n
MPLA 23 (2008) 1885: Review (HERA data)
PRD 80 (2009) 074006: p p 2 jets+p
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Motivation
Diffractive Higgs production:Clean central events, similar to vector-boson fusion
Easier identification of h than in incl. Higgs productionRelies on understanding of pomeron flux / parton densities
Factorization breaking in single-diffractive dijets:For photoproduction established only at NLODirect vs. resolved, x-dependence of S still under discussionFor hadroproduction established already at LOThorough NLO analysis was missing since Y2K !!
April 20, 2010 Michael Klasen, LPSC Grenoble 3
Definition of the SD / ND cross sections
Hadronic cross section:
Non-diffractive PDFs:CTEQ6L1 / CTEQ6.6M
Diffractive PDFs:H1 2006 fit A, BH1 2007 fit jets (no f.b.!)MY < 1.6 GeV
1.15 larger than ZEUS LPS
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Experimental cuts by CDF
PRL 84 (2000) 5043:
s = 1800 GeVRun IC (95-96), RPS
|t| < 1 GeV2
0.035 < < 0.095
R = 0.7, Rsep = 1.3R
ET 1,2 > 7 (6.5) GeV
|| < 4.2
April 20, 2010 Michael Klasen, LPSC Grenoble 5
MK and G. Kramer, PLB 366 (1996) 385
Experimental cuts by CDF
PRL 84 (2000) 5043:
s = 1800 GeVRun IC (95-96), RPS
|t| < 1 GeV2
0.035 < < 0.095
R = 0.7, Rsep = 1.3R
ET 1,2 > 7 (6.5) GeV
|| < 4.2
PRL 88 (2002)
151802:
s = 630 and 1800 GeVRun IC (95-96) UA8
|t| < 0.2 GeV2
0.035 < < 0.095
R = 0.7, Rsep = 1.3R
ET > 10 GeV
|| < 4.2
April 20, 2010 Michael Klasen, LPSC Grenoble 6
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MK and G. Kramer, PLB 366 (1996) 385
Observables derived from JJ(th)/NJJ(exp)
Parton momentum fraction in antiproton, pomeron: directly from jets, but in convolution
Ratio of SD to ND cross sections:
Integrated over ET 1,2 and 1,2 with xp fixed
Integrate also over t and ranges, assume similar Q2 ≈ ET2
Naive estimate of non-diffractive structure function: (t-channel gluon exchange)
GRV 98 LO, <Q2> = 75 GeV2 (<ET> ≈ 8.7 GeV)
Diffractive structure function:
Weak dependence on Use <> = 0.063
April 20, 2010 Michael Klasen, LPSC Grenoble 7
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Average transverse-energy distribution
Non-diffractive (ND): Single-diffractive (SD):
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<ET> ≈ 8.7 GeV_
Average rapidity distribution
Non-diffractive (ND): Single-diffractive (SD):
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small xp_large xp
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Parton momentum fraction in anti-proton
Ratio SD/ND: Suppression factor:
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NLO≈LO,x-dependent
Parton momentum fraction in pomeron
Diffr. structure function:
Suppression factor:
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<> = 0.063GRV98LO
<Q2>=75 GeV2
weaker -dependence
Average transverse-energy distribution
Non-diffractive (ND): Single-diffractive (SD):
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Average rapidity distribution
Non-diffractive (ND): Single-diffractive (SD):
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Perfe
ct!
Energy dependence of ratio SD/ND
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Energy dependence of suppression factor
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Energy dependence of diffr. structure fct.
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<> = 0.063GRV98LO
<Q2>=75 GeV2
<> = 0.063GRV98LO
<Q2>=75 GeV2
Energy dependence of suppression factor
April 20, 2010 Michael Klasen, LPSC Grenoble 17
Pomeron momentum fraction in
antiproton
Published in PRL 88Agrees with PRL 84
data:
taken at =0.1
Weak -dependence <>=0.063 not badAlso observed in (N)LO H1 pomeron flux fact.
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June 7, 2006 Michael Klasen, LPSC Grenoble 19
Two-Channel Eikonal ModelDouble Pomeron exchange:
Survival probability:
Opacity / optical density: Ki = 1
Kaidalov et al., EPJC 21 (2001) 521
Fit tot, del./dt to ISR, SppS, Tevatron data
Total cross section: Determines (gIP
pp)2 = 25 mbStarting scale s0 = 1 GeV2
Large distance physics: = 0.1
Elastic amplitude: Pomeron trajectory: (t) = 1 + ’ t + Small distance physics: ’ = 0.15 GeV-2
Pomeron vertex in b-space:B = B0/2 + ’ ln (s/s0)Elastic slope: B0 = 8 GeV-2
p N* transition probability: = 0.4
Survival probability: S ≈ 0.1Small abs./size: Val., large xp, small Large abs./size: Sea, small xp, small
ConclusionLO analysis by CDF was very crude:
Cone algorithm, equal ET cuts [in PRL 84 (2000) 5043]
Proton PDFs, Q2 dependence and systematic errors cancelIntegrations over and t don´t matterStructure function ≈ t-channel gluon exchange
Still, NLO analysis confirms main conclusions:SD/ND K-factors of 1.6 (630 GeV) and 1.35 (1800 GeV)Partially compensated by exact ratios of NLO cross sectionsSuppression factor is x-dependent, in particular at small xPredicted by LO two-channel eikonal model valence/seaLess dependence on , at NLO, 630 GeV, with H1 2007 jets
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