Seminários GFPAE – 02/2009 1 Diffractive heavy quark production at the LHC Mairon Melo Machado...
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Transcript of Seminários GFPAE – 02/2009 1 Diffractive heavy quark production at the LHC Mairon Melo Machado...
1Seminários GFPAE – 02/2009
Diffractive heavy quark production at the LHC
Mairon Melo [email protected]
2Seminários GFPAE – 02/2009
Outlook
Motivation Diffractive Physics Hadroproduction of heavy quarks at LO Hadroproduction of heavy quarks at NLO Coherent and incoherent heavy quark production Pomeron Structure Function Multiple Pomeron Scattering Results Conclusions
3Seminários GFPAE – 02/2009
Cross section for heavy quark production allows to probe the gluon densities
Pomeron with substructure Ingelman-Schlein
Ingelman-Schlein predictions
Absorptive corrections multiple Pomeron Scattering
Gap survival probability to AA single diffractive collisions
Coherent and incoherent diffraction is a powerful tool for studying the low-x processes (gluon saturation)
HQ are important signals of possible new physics
Motivation
BBH BBgg signal background
4Seminários GFPAE – 02/2009
Introduction Diffractive processes rapidity gap
Exchange of a Pomeron with vacuum quantum numbers
Pomeron not completely known
Parton content in the Pomeron DPDFs
Diffractive distributions of singlet quarks and gluons in the Pomeron
Coherent (small-x dynamics) and incoherent cases (color field fluctuations)
Diffractive structure function
Gap Survival Probability (GSP)
5Seminários GFPAE – 02/2009
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 angular regions Φ of the final state phase space
Diffractive events
Rapidity gaps
Ingelman-Schlein Model
6Seminários GFPAE – 02/2009
o Focus on the following single diffractive processes
Heavy quark hadroproduction
o Diffractive ratios as a function of energy center-mass ECM
X+CC+ppp X+BB+ppp
o Diagrams contributing to the lowest order cross section
Q+Qg+g
7Seminários GFPAE – 02/2009
LO hadroproductionTotal cross section
Partonical cross section
are the parton distributions inner the hadron i=1 and j=2
factorisation (renormalisation) scale RF μμ
8Seminários GFPAE – 02/2009
Partonic cross section
N = 3 (4) to charm (bottom)
m is the heavy quark mass is the coupling constant
V=N 2− 1 Dimension of the SU(N) gauge group
(number of gluons)
p1,2 are the parton momenta
Sα
9Seminários GFPAE – 02/2009
NLO Production
g+Q+Qg+g
Running of the coupling constant
n1f = 3 (4) charm (bottom)
10Seminários GFPAE – 02/2009
NLO functions
a0 0.108068
a1 -0.114997
a2 0.0428630
a3 0.131429
a4 0.0438768
a5 -0.0760996
a6 -0.165878
a7 -0.158246
Using a physical motivation fit to the numerically integrated result
Error of 1%
11Seminários GFPAE – 02/2009
NLO Production
Auxiliary functions
12Seminários GFPAE – 02/2009
Diffractive cross section
Pomeron flux factor
Pomeron Structure Function (H1)
β=xxIP
KKMR model <|S|2> = 0.06 at LHC single diffractive events
FIT A Similar results with FIT B
13Seminários GFPAE – 02/2009
Incoherent diffractive is a process where
A* denotes the excited nucleus that subsequently decays into a system of colorless hadrons
Diffractive incoherent ratio
Coherent diffractive is a process where
Stronger dependence on energy and atomic number
Diffractive Nuclear heavy quark production
*A+[LRG]QQ+A+XA+A
single diffraction
A+[LRG]QQ+A+XA+A
14Seminários GFPAE – 02/2009
qq vs. gg
• Inclusive cross section and diffractive cross section
• Charm-anticharm hadroproduction
• Contribution of qq anihillation at high energies not important
• Diffractive cross section without GSP
• Mc = 1.5 GeV
Inclusive quarks/gluons
Inclusive gluons
Diffractive
15Seminários GFPAE – 02/2009
Diffractive comparison
• Diffractive cross sections to bottom-antibottom hadroproduction
• Relevant contribution of GSP value in the total diffractive
cross section
• <|S|2> = 0.06
• Mb = 4.7 GeV
Inclusive
Diffractive wt/GSP
Diffractive wh/GSP
16Seminários GFPAE – 02/2009
Comparison LO and NLO
• Predictions for inclusive cross sections in pp collisions (LHC)
• NLO cross section is 1.5 higher than LO cross section at high energies
17Seminários GFPAE – 02/2009
Cross sections in NLO to inclusive nuclear cross section
ACa = 40 APb = 208
Results for heavy quark production
Cross sections in NLO for heavy quarks hadroproduction
GSP value decreases the diffractive rate
<|S|2> = 0.06
18Seminários GFPAE – 02/2009
Incoherent results
There are not values of <|S|2> to single diffraction in AA collisions
Estimatives to Higgs central production <|S|2> ~ 1 x 10-4
Values of diffractive cross section in a region possible to be verified
19Seminários GFPAE – 02/2009
Coherent results
Predictions to diffractive cross section in a region possible to be verified
Diffractive cross section without GSP is consistent with the literature
Very small single diffractive ratio
20Seminários GFPAE – 02/2009
Conclusions• Theoretical predictions for inclusive and single diffractive heavy quarks
production at LHC energies in pp and AA collisions
• Estimates for cross sections as a function of energy center mass ECM
• Diffractive ratio is computed using hard diffractive factorization and absorptive corrections (NLO)
• There are not predictions to <|S|2> in AA collisions
• Important contribution of the absolute value of absorptive corrections
• Diffractive cross section for AA collisions in a region that is possible to be verified
• Evaluation of the gap survival probability for single diffraction in AA collisions
21Seminários GFPAE – 02/2009
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