Diffractive heavy q uark production in A A collisions at the LHC at NLO *

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

2. 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 Outlook DIFFRACTION 2010

3. Motivation • 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 signal background 3 DIFFRACTION 2010

4. 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 ? 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) Introduction 1, 2 Studies Diffractive structure function Gap Survival Probability (GSP) DIFFRACTION 2010

5. Absence of hadronic energy in angular regions Φof the final state Hard diffractive factorization 4 4 M. Heyssler, Z. Phys. C 73. (1997) 297. 5 B. Z. Kopeliovich et al, Phys. Rev. Lett. 85, 507 (2000) Diffractive events Rapidity gaps Single diffraction DPE exchange • Introduction of the appropriate absorptive effects which cause the suppresion of any LRG process 5 and nuclear effects as well DIFFRACTION 2010

6. Diffractive ratios as a function of energy center-mass ECM 6 M. L. Mangano et al, Nucl. Phys. B 373, 295 (1992) Heavy quark hadroproduction • Focus on the following single diffractive processes • Diagrams contributing to the lowest order cross section6 DIFFRACTION 2010

7. 6 M. L. Mangano, P. Nason, G. Ridolfi Nucl. Phys. B373 (1992) 295 Total cross section LO 6 x1,2 are the momentum fraction are the parton distributions inner the hadron i=1 and j=2 Partonical cross section factorization (renormalization) scale DIFFRACTION 2010

8. 6 M. L. Mangano, P. Nason, G. Ridolfi Nucl. Phys. B373 (1992) 295 NLO Production 6 Running of the coupling constant n1f = 3 (4) charm (bottom) DIFFRACTION 2010

9. NLO functions 8 P. Nason, S. Dawson, R. K. Ellis Nucl. Phys. B303 (1988) 607 8 Auxiliary functions 9 DIFFRACTION 2010

10. 9 H1 Coll. A. Aktas et al, Eur. J. Phys. J. C48 (2006) 715 10 V. A. Khoze, A. D. Martin, M. G. Ryskin, Eur. Phys. J. C18, 167 (2000) Diffractive cross section Pomeron flux factor Pomeron Structure Function (H1) 9 KKMR model <|S|2> = 0.06 at LHC single diffractive events 10 Parametrization of the pomeron flux factor and structure function H1 Collaboration DIFFRACTION 2010

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

12. 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) Inclusive nuclear cross section at NLO APbPb = 208 (5.5 TeV); 40 (6.3) TeV difrativo 12 DIFFRACTION 2010

13. Diffractive cross sections @ LHC 13 M. Gay Ducati, M. M. M, M. V. T. Machado, PRD. 81, 054034 (2010) 14 B. Kopeliovich et al, 0702106 [arXiv:hep-ph] (2007) Inclusive cross section Diffractive cross sections Proton-Nucleus collision Similar results that 14 Nucleus-Nucleus collision • Predictions to cross sections possible to be verified at the LHC 13 Very small diffractive ratio 13 DIFFRACTION 2010

14. Diffractive cross sections @ LHC 13 M. Gay Ducati, M. M. M, M. V. T. Machado, PRD. 81, 054034 (2010) 13 • 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 sectionspossible to be verified experimentally 14 DIFFRACTION 2010

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

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

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

18. DPE results 10 V. A. Khoze, A. D. Martin, M. G. Ryskin, Eur. Phys. J. C18, 167 (2000) pp collisions at the LHC (14 TeV) Ingelman-Schlein Bialas-Landshoff 10 Ingelman-Schlein > Bialas-Landshoff 18 DIFFRACTION 2010

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 <|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 important DIFFRACTION 2010

20. pA cross sections @ LHC • Suppression factor σpA ~ 0.8 mb 20 DIFFRACTION 2010