1. 1 Diffractive heavy quark production in AA collisions at the LHC at NLO* Mairon Melo Machado GFPAE – IF – UFRGS melo.machado@ufrgs.br www.if.ufrgs.br/gfpae * Work with M. V. T. Machado and M. B. Gay Ducati DIFFRACTION 2010 – OTRANTO, ITALY, 10 – 15 SEPTEMBER

2. 2 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 DIFFRACTION 2010

3. 3 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 signal background DIFFRACTION 2010

4. 4 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 functionGap Survival Probability (GSP) DIFFRACTION 2010 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

5. 5  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) DIFFRACTION 2010 Single diffraction DPE exchange  Introduction of the appropriate absorptive effects which cause the suppresion of any LRG process 5 and nuclear effects as well

6. 6 o Focus on the following single diffractive processes Heavy quark hadroproduction o Diffractive ratios as a function of energy center-mass E CM o Diagrams contributing to the lowest order cross section 6 6 M. L. Mangano et al, Nucl. Phys. B 373, 295 (1992) DIFFRACTION 2010

7. 7 Total cross section LO Partonical cross section are the parton distributions inner the hadron i=1 and j=2 6 6 M. L. Mangano, P. Nason, G. Ridolfi Nucl. Phys. B373 (1992) 295 factorization (renormalization) scale x 1,2 are the momentum fraction DIFFRACTION 2010

8. 8 NLO Production 6 6 M. L. Mangano, P. Nason, G. Ridolfi Nucl. Phys. B373 (1992) 295 Running of the coupling constant n 1f = 3 (4) charm (bottom) DIFFRACTION 2010

9. 9 NLO functions 8 P. Nason, S. Dawson, R. K. Ellis Nucl. Phys. B303 (1988) 607 a0a0 0.108068 a1a1 -0.114997 a2a2 0.0428630 a3a3 0.131429 a4a4 0.0438768 a5a5 -0.0760996 a6a6 -0.165878 a7a7 -0.158246 DIFFRACTION 2010 Auxiliary functions 8

10. 10 Diffractive cross section Pomeron flux factor Pomeron Structure Function (H1) 9 9 H1 Coll. A. Aktas et al, Eur. J. Phys. J. C48 (2006) 715 KKMR model = 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 DIFFRACTION 2010

11. 11 Nuclear single diffractive 11 N. M. Agababyan et al Phys. Atom. Nucl. 62, 1572 (1999) 12 K. Tuchin, arXiv:0812.1519v2 [hep-ph] (2009) 11 Inclusive case A Pb = 208 (5.5 TeV) Incoherent process Pomeron emmited by a nucleon inner the nucleus Coherent process Pomeron emmited by the nucleus Diffractive case DIFFRACTION 2010 11 12

12. Inclusive nuclear cross section at NLO A PbPb = 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 ( = 0.06) difrativo DIFFRACTION 2010

13. 13 Diffractive cross sections @ LHC  Predictions to cross sections possible to be verified at the LHC 13 Inclusive cross section DIFFRACTION 2010 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)

14. 14 Diffractive cross sections @ LHC  No values to for single diffractive events in AA collisions  Estimations to central Higgs production ~ 8 x 10 -7  Values of diffractive cross sections possible to be verified experimentally DIFFRACTION 2010 13 13 M. Gay Ducati, M. M. M, M. V. T. Machado, PRD. 81, 054034 (2010)

15. 15 Bialas-Landshoff approach nucleon form-factor Double Pomeron Exchange DIFFRACTION 2010 Differential phase-space factor mass of produced quarks 15 15 A. Bialas and W. Szeremeta, Phys. Lett. B 296, 191 (1992)

16. 16 Bialas-Landshoff approach two-dimensional four-vectors describing the transverse component of the momenta Sudakov parametrization for momenta DIFFRACTION 2010 momentum for one of exchanged gluons momenta for the incoming (outgoing) protons momentum for the produced quark (antiquark)

17. 17 Bialas-Landshoff approach Square of the invariant matrix element averaged over initial spins and summed over final spins 14 DIFFRACTION 2010 effect of the momentum transfer dependence of the non-perturbative gluon propagator 14 A. Bialas and W. Szeremeta, Phys. Lett. B 296, 191 (1992)

18. 18 DPE results Ingelman-Schlein DIFFRACTION 2010 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) 10 Ingelman-Schlein > Bialas-Landshoff

19. 19 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 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 important DIFFRACTION 2010

20. 20 pA cross sections @ LHC  Suppression factor DIFFRACTION 2010 σ pA ~ 0.8 mb