single diffractive higgs production at the lhc *
DESCRIPTION
Maria Beatriz Gay Ducati [email protected]. Single Diffractive Higgs Production at the LHC *. DIFFRACTION 2010 – OTRANTO, ITALY, 10 – 15 SEPTEMBER. * Work with G. G. Silveira, M. M. Machado and M. V. T. Machado. Motivation Diffractive Physics Higgs production at LO - PowerPoint PPT PresentationTRANSCRIPT
1
Single Diffractive Higgs Production at the LHC *
Maria Beatriz Gay [email protected]
DIFFRACTION 2010 – OTRANTO, ITALY, 10 – 15 SEPTEMBER
* Work with G. G. Silveira, M. M. Machado and M. V. T. Machado
2
Outlook Motivation
Diffractive Physics
Higgs production at LO
Higgs production at NLO
Inclusive and diffractive cross section
Pomeron Structure Function
Multiple Pomeron Scattering
Results
Conclusions
3
Compute single diffractive and Double Pomeron Exchange (DPE) production of the Standard Model Higgs Boson
Considering diffractive factorization formalism
Parametrization for the Pomeron Structure Function H1 Collaboration (2006)
Cross section computed at NLO accuracy
Gluon fusion process leading mechanism to the Higgs boson production
Gap survival probability rescattering corrections due to spectator particles
Single diffractive ratio computed for proton-proton collisions at the LHC
Estimations for the single and DPE events in the LHC kinematical regime
Motivation
4
LHC opens a new kinematical region:
CM Energy in pp Collisions: 14 TeV 7x Tevatron Energy
Luminosity: 10 – 100 fb-1 10 x Tevatron luminosity
MotivationThe TEVNPH Working Group, 1007.4587 [hep-ph]
Evidences show new allowed mass range excluded for Higgs Boson production
Tevatron exclusion ranges are a combination of the data from CDF and D0
5
Introduction
Diffractive processes rapidity gap
Exchange of a Pomeron with vacuum quantum numbers
Pomeron with substructure DPDFs
Diffractive distributions of quarks and gluons in the Pomeron
Diffractive structure function
Gap Survival Probability (GSP)
MBGD, M. M. Machado and M. V. T. Machado, PRD
What is the Pomeron ?
Cross sections at NLO
6
Single diffraction in hadronic collisions
One of the colliding hadrons emits Pomeron
Partons in the the Pomeron interact with partons from the another hadron
Absence of hadronic energy in the final state
Single diffractive Higgs production
Rapidity gaps
Regge factorization
Heyssler et al, 9702.286 [hep-ph]
7
Double Pomeron Exchange in hadronic collisions
Both colliding hadrons emit Pomeron
Partons in the the Pomerons interact with each other
Absence of hadronic energy in the final state
Two rapidity gaps
Regge factorization
DPE Higgs production P. D. Collins, An Introduction to Regge Theory and High Energy Physics
8
o Focus on the gluon fusion
o Main production mechanism of Higgs boson in high-energy pp collisions
o Gluon coupling to the Higgs boson in SM
triangular loops of top quarks
Higgs production D. Graudenz et al. PRL 70 (1993) 1372
Lowest order to gg contribution
9
Diagrams
Higgs production in gq and qq collisions
Vertex corrections
Real gluon radiation
o At NLO, these processes could occur
Quark considered top (high mass)
Possible background expected for high pT
BBgg
10
Lowest order
parton cross section expressed by the gluonic width of the Higgs boson
gg invariant energy squared
Partonic cross section M. Spira et al. 9504378 [hep-ph]
dependence
Quark Top
11
LO hadroproduction Lowest order two-gluon decay width of the Higgs boson
Gluon luminosityPDFs MSTW2008
Lowest order proton-proton cross section
Renormalization scale
s invariant pp collider energy squared
12
QCD Corrections
Involve virtual corrections for the subprocess and the radiation of
gluons in the final state
Higgs boson production gluon-quark collisions and quark
annihilation
Subprocesses contribute to the Higgs production at the same order of αs
Virtual corrections modify the lowest-order fusion cross section by a
coefficient linear in αs
M. Spira et al. 9504378 [hep-ph]
Three contributions
13
NLO Cross Section Gluon radiation two parton final states
Invariant energy in the channels
New scaling variable supplementing and
The final result for the pp cross section at NLO
Renormalization scale in αs and the factorization scale of the parton densities to be fixed properly
14
NLO Cross Section Coefficient contributions from the virtual two-loop
corrections
Regularized by the infrared singular part of the cross section for real gluon emission
Infrared part
Finite τQ dependent piece
Logarithmic term depending on the renormalization scale μ
15
Delta functionso Contributions from gluon radiation in gg, gq and qq scattering
o Dependence of the parton densities
o Renormalization scale
QCD coupling in the radiative corrections and LO cross sections
renormalization scale μ
factorization scale M
16
d functions
F+
usual + distribution
Considering only the heavy-quark limit
Region allowed by Tevatron combination
17
Diffractive cross section
Normalization
Gluon distributions in the proton
β=xxIP
Single diffractive
H1 parametrization (2006)
Double Pomeron Exchange
Gluon distributions in the Pomeron
Gluon distributions (i ) in the Pomeron IPPomeron flux
MSTW (2008)
H1 parametrization
• Range of data
0.0043 < z < 0.8
• In this work, FIT B.
• z is the momentum fraction of the Pomeron
A. Aktas et al, Eur. J. Phys. J. C48 (2006) 715
19
Gap
• Absorptive corrections by Multiple Pomeron Scattering
• <|S|2> gap survival probability (GSP)
• A(s,b) diffractive process amplitude
• PS(s,b) probability that no inelastic interactions occurs between
remains particles
Gap Survival Probability (GSP)
22
22
2
|b)A(s,|bd
s)(b,P|b)A(s,|bd|>S|
s
Comparison between GLM and KKMR models
20
Single diffraction
• ρ variable gives the renormalization/factorization
scale dependence
• Predictions to inclusive and diffractive cross sections at LO in agreement with other
theoretical predictions
Heyssler et al, arXiv:hep-ph/9702286
M. Spira et al. 9504378 [hep-ph]
NLO cross sections ~ 1.7 greater than LO cross sections
21
Double Pomeron Exchange
• DPE cross sections as Higgs mass function
• Significant reduction of the diffractive cross section when applied the GSP
• Difference about a factor 2 between GLM and KKMR
models
• Cross section and PDFs evaluated at NLO
KKMR = 2.6 %
GLM = 6 %
22
Higgs production as ρ function (LO)ρ σInc
(pb)
σDiff
(pb)
σKKMR
(pb)
σGLM
(pb)
Rdiff
(%)
RKKMR
(%)
RGLM
(%)
0.5 13.18 0.52 0.031 0.042 3.95 0.24 0.32
1.0 10.04 0.26 0.016 0.021 2.59 0.16 0.21
1.5 8.65 0.21 0.013 0.017 2.43 0.15 0.19
4.0 6.21 0.16 0.010 0.014 2.48 0.15 0.19
Single Diffraction
KKMR = 6 %
GLM = 8 %
Heyssler et al, arXiv:hep-ph/9702286
ρ σInc
(pb)
σDiff
(pb)
σKKMR
(pb)
σGLM
(pb)
Rdiff
(%)
RKKMR
(%)
RGLM
(%)
0.5 13.18 0.07 0.0021 0.0047
0.60 0.016 0.036
1.0 10.04 0.042 0.0011 0.0025
0.42 0.011 0.025
1.5 8.65 0.033 0.0086 0.0020
0.38 0.010 0.023
4.0 6.21 0.025 0.0065 0.0015
0.40 0.010 0.023ρ = μ / MH
DPE
KKMR = 2.6 %
GLM = 6 %
Boonekamp et al, arXiv:hep-ph/0406061
23
Higgs production as ρ function (NLO)
ρ σInc
(pb)
σDiff
(pb)
σKKMR
(pb)
σGLM
(pb)
Rdiff
(%)
RKKMR
(%)
RGLM
(%)
0.5 22.01 0.87 0.052 0.069 3.95 0.24 0.32
1.0 16.77 0.43 0.026 0.034 2.59 0.16 0.21
1.5 14.45 0.35 0.022 0.028 2.43 0.15 0.19
4.0 10.37 0.27 0.017 0.022 2.48 0.15 0.19
ρ σInc
(pb)
σDiff
(pb)
σKKMR
(pb)
σGLM
(pb)
Rdiff
(%)
RKKMR
(%)
RGLM
(%)
0.5 22.01 0.12 0.0033 0.0064
0.57 0.015 0.030
1.0 16.77 0.06 0.0017 0.0040
0.40 0.010 0.024
1.5 14.45 0.05 0.0013 0.0031
0.36 0.009 0.022
4.0 10.37 0.04 0.0011 0.0024
0.38 0.009 0.022
Single Diffraction
KKMR = 6 %
GLM = 8 %
DPE
KKMR = 2.6 %
GLM = 6 %
ρ = μ / MH
24
Conclusions
• Estimate for cross sections as a function of Higgs Mass and ρ = μ/MH
• Diffractive ratio computed using hard diffractive factorization and absorptive corrections
• Values of diffractive LO cross section in good agreement with other theoretical predictions
• Different predictions to NLO cross sections using two GSP models (KKMR and GLM)
• Feasible value of cross sections for both GSP models
SD ~ 2.5 %
DPE ~ 0.5 %
SD ~ 50 - 70 fb DPE ~ 3 – 6 fb γ γ 0.1 fb
γp 0.08 fb MBGD, G. G. Silveira PRD 78 113005 (2009)
• Theoretical predictions
Inclusive
Single Diffractive
Double Pomeron Exchange
Higgs production at LHC energies at
LO and NLO
Very small diffractive ratios to Higgs Mass ~ 150 GeV
at NLO without GSP