1Seminários GFPAE – 02/2009

Diffractive heavy quark production at the LHC

Mairon Melo Machadomelo.machado@ufrgs.br

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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