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Diffractive heavy quark production in AA collisions at the

LHC at NLO*

Mairon Melo MachadoGFPAE – IF – UFRGS

melo.machado@ufrgs.brwww.if.ufrgs.br/gfpae

* Work with M. V. T. Machado and M. B. Gay Ducati

DIFFRACTION 2010 – OTRANTO, ITALY, 10 – 15 SEPTEMBER

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Outlook Motivation

Diffractive Physics

Hadroproduction of heavy quarks at LO

Hadroproduction of heavy quarks at NLO

Coherent heavy quark production

Pomeron Structure Function

Multiple Pomeron Scattering

Results

Conclusions

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Heavy quarks will be produced in large quantities at LHC

Very important for physics study and for understanding background processes

Heavy flavoured hadrons may produce high momentum leptons

Potential background to new physics

Estimate the inclusive, single and Double Pomeron Exchange (DPE) in heavy ion collisions

Coherent and incoherent (single diffraction) production of heavy quarks in AA collisions

Coherent DPE production of heavy quarks in AA collisions

Motivation

BBH BBgg

signal

background

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A+[LRG]+A+XA+A *A+[LRG]+A+XA+A

A+[LRG]XQQLRGAA+A ][][

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Introduction Diffractive processes caractherized by a rapidity gap Pomeron

Pomeron and its reaction mechanisms is not completely known

Regge Theory Pomerons with substructure DPDFs

It does not describe hadron collider data

Application of multiple Pomeron scattering suppress the diffractive cross section

Gap Survival Probability (GSP) to AA collisions ?

Diffractive structure function Gap Survival Probability (GSP)

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Studies

1 M. B. Gay Ducati, M. M. M, M. V. T. Machado, PRD 75, 114013 (2007)

2 M. B. Gay Ducati, M. M. M, M. V. T. Machado, PRD 81, 054034 (2010)

1, 2

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Absence of hadronic energy in angular regions Φ of the final state

Hard diffractive factorization 4

Diffractive events

Rapidity gaps

4 M. Heyssler, Z. Phys. C 73. (1997) 297.5 B. Z. Kopeliovich et al, Phys. Rev. Lett. 85, 507 (2000)

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Single diffraction DPE exchange

Introduction of the appropriate absorptive effects which cause the suppresion of any LRG process 5 and nuclear effects as well

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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 6

6 M. L. Mangano et al, Nucl. Phys. B 373, 295 (1992)

Q+Qg+g

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Total cross section LO

Partonical cross section

are the parton distributions inner the hadron i=1 and j=2

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6 M. L. Mangano, P. Nason, G. Ridolfi Nucl. Phys. B373 (1992) 295

factorization (renormalization) scale RF μμ

x1,2 are the momentum fraction sxxs 21

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NLO Production6

6 M. L. Mangano, P. Nason, G. Ridolfi Nucl. Phys. B373 (1992) 295

g+Q+Qg+g

Running of the coupling constant

n1f = 3 (4) charm (bottom)

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NLO functions

8 P. Nason, S. Dawson, R. K. Ellis Nucl. Phys. B303 (1988) 607

a0 0.108068

a1 -0.114997

a2 0.0428630

a3 0.131429

a4 0.0438768

a5 -0.0760996

a6 -0.165878

a7 -0.158246

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Auxiliary functions

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Diffractive cross section

Pomeron flux factor

Pomeron Structure Function (H1) 9

β=xxIP

9 H1 Coll. A. Aktas et al, Eur. J. Phys. J. C48 (2006) 715

KKMR model <|S|2> = 0.06 at LHC single diffractive events 10

10 V. A. Khoze, A. D. Martin, M. G. Ryskin, Eur. Phys. J. C18, 167 (2000)

Parametrization of the pomeron flux factor and structure function H1 Collaboration

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Nuclear single diffractive

11 N. M. Agababyan et al Phys. Atom. Nucl. 62, 1572 (1999)

12 K. Tuchin, arXiv:0812.1519v2 [hep-ph] (2009)

A+[LRG]+A+XA+A

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Inclusive case

APb = 208 (5.5 TeV)

Incoherent process Pomeron emmited by a nucleon inner the nucleus

Coherent process Pomeron emmited by the nucleus

*A+[LRG]+A+XA+A

Diffractive case

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Inclusive nuclear cross section at NLO

APbPb = 208 (5.5 TeV); 40 (6.3) TeV

Heavy quarks production at the LHC

Heavy quarks cross sections in NLO to pp collisions

GSP value decreases the diffractive ratio (<|S|2> = 0.06)

difrativo

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Diffractive cross sections @ LHC

Predictions to cross sections possible to be verified at the LHC 13

Inclusive cross section

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Diffractive cross sections

Very small diffractive ratio

Proton-Nucleus collision

Nucleus-Nucleus collision

13 M. Gay Ducati, M. M. M, M. V. T. Machado, PRD. 81, 054034 (2010)

Similar results that 14

14 B. Kopeliovich et al, 0702106 [arXiv:hep-ph] (2007)

0287.02 GAPS

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Diffractive cross sections @ LHC

No values to <|S|2> for single diffractive events in AA collisions

Estimations to central Higgs production <|S|2> ~ 8 x 10-7

Values of diffractive cross sections possible to be verified experimentally

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13 M. Gay Ducati, M. M. M, M. V. T. Machado, PRD. 81, 054034 (2010)

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Bialas-Landshoff approach

nucleon form-factor

Double Pomeron Exchange

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pQQppp

Differential phase-space factor

mass of produced quarks

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15 A. Bialas and W. Szeremeta, Phys. Lett. B 296, 191 (1992)

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Bialas-Landshoff approach

two-dimensional four-vectors describing the transverse component of the momenta

Sudakov parametrization for momenta

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momentum for one of exchanged gluons

momenta for the incoming (outgoing) protons

momentum for the produced quark (antiquark)

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Bialas-Landshoff approach

Square of the invariant matrix element averaged over initial spins and summed over final spins 14

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effect of the momentum transfer dependence of the non-perturbative gluon propagator

14 A. Bialas and W. Szeremeta, Phys. Lett. B 296, 191 (1992)

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DPE results

Ingelman-Schlein

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Bialas-Landshoff

pp collisions at the LHC (14 TeV)

10 V. A. Khoze, A. D. Martin, M. G. Ryskin, Eur. Phys. J. C18, 167 (2000)

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Ingelman-Schlein > Bialas-Landshoff

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Conclusions• Theoretical predictions for single and DPE heavy quarks production at

LHC energies in pp, pA and AA collisions

• Diffractive ratio is computed using hard diffractive factorization and absorptive corrections (NLO)

• There are no predictions to <|S|2> in pA and AA collisions

• Diffractive cross sections for AA collisions possible to be verified

• Diffractive channel dominates over exclusive photoproduction channel in proton-proton case

• Calculation of GSP values to AA collisions is highly importantDIFFRACTION 2010

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pA cross sections @ LHC

Suppression factor

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σpA ~ 0.8 mb