Heavy Quark Production in photon-Pomeron interactions at hadronic colliders *

1. Heavy Quark Production in photon-Pomeron interactions at hadronic colliders* Mairon Melo Machado melo.machado@ufrgs.br HEP – VALPARAÍSO, CHILE, 03 – 10 JANUARY 1 * Work with V. P. B. Gonçalves

2. Motivation Diffractive Physics Coherent Interactions in Hadronic Colliders Diffractive photoproduction of heavy quarks Heavy quarks photoproduction in the resolved Pomeron model Pomeron Structure Function Results Conclusions Outlook

3. Motivation • Pomeron (IP) carrying quantum numbers of the vacuum • associated with diffractive events • Large rapidity gaps in the hadronic final state • Diffraction information about structure of hadrons / interaction mechanisms. • Exclusive events rapidity gaps separate the intact very forward hadron from • the central massive object. • Nothing else is produced, except the leading hadrons and the central object. • Inclusive processes rapidity gaps + soft particles + hard diffractive object • Rapidity gaps smaller than in the exclusive case.

4. Motivation • Good test for diffractive physics heavy quark production • Some models to the Pomeron • Resolved Pomeron model • Diffractive factorization formalism and Pomeron has a partonic structure • Light-cone dipole approach • Dipole-target with breakdown of factorization in diffractive hadronic collisions • Both models describe the experimental data for single diffractive heavy quarks • Correct approach to describe inclusive diffraction process is an open question. • Improved version of the Durham model high cross section • Study of alternative processes which allow to constrain the correct description of the Pomeron.

5. Diffractive processes rapiditygap Exchange of a Pomeronwithvacuum quantum numbers PomeronwithsubstructureDPDFs Diffractivedistributionsof quarks andgluons in thePomeron Diffractive heavy quark production mediated by photons coherent (ultraperipheral) collisions Introduction What is the Pomeron ?

6. Coherent interactions • Photon stemming from the electromagnetic field of one of the two colliding hadrons • Interaction with one photon of the other hadron (two-photon process) or directly with the other hadron (photon-hadron process). • Coherent processes allow us to study the inclusive and diffractive heavy quark photoproduction. • Distinct experimental signature easily to be separated. • Diffractive heavy quark photoproduction two rapidity gaps and hadrons • intact in the final state • Verify if the diffractive heavy quark photoproduction can be useful to discriminate between the resolved and perturbative models for the Pomeron • Compare our predictions with other in the literature. Rapidity gaps 6

7. Coherent interactions • Total cross section can be factorized in terms of the equivalent flux of photons of the hadron projectile and the photon-photon or photon-target production cross section • Cross sections for γh interactions are at least two order of magnitude largerthan for γ γ interactions • Focusing in the photon-hadron process • Cross section for the diffractive photoproduction of heavy quarks in a coherent hadron-hadron collision • ⊗ rapidity gap in the final state • ω photon energy equivalent photon flux Center mass square energy

8. Photon flux (p-p) • Analyticapproximation for theequivalentphoton flux of a hadron • Photoncanbeconsidered as real • Lorentz boostof a singlebeam (7455 at LHC)

9. Photon flux (p-A) • Analytic approximation for the equivalent photon flux of a nuclei • Modified Bessel Functions and • b impact parameter • pA interactions photon direction is known • Collision assymmetry rapidity distribution assymmetry • Resolved Pomeron Model final state associated to the hadronization of • the Pomeron remnants

10. Resolved Pomeron Model • Diffractive cross section parton distributions in the Pomeron and Pomeron • flux factor • Diffractive Gluon Distribution • Center-of-mass energy of γp system • Momentum fraction carried by the gluon • Mass of the heavy quark

11. Photon-gluon fusion CS • Cross section at Leading Order • Electric charge of the heavy quark • Eletromagnetic coupling constant

12. Diffractive Gluon distribution . • Convolution of • flux of Pomerons • gluon distribution in the Pomeron . • Fraction of the hadrons momentum transferred into the diffractive system • Momentum fraction carried by the gluon inner the Pomeron • Flux of Pomerons • H1 Collaboration Kinematic boundaries

13. Results (h-h collisions) • Rapidity distribution • Rapidity distribution increases with energy • As expected from the behaviour of the diffractive gluon distribution in small-x • Total cross section for charm-anticharm production

14. Results (comparing models) • Diffractive charm and bottom photoproduction in pp collisions at LHC • (14 TeV)

15. Results (p-A collisions) • Cross section enhanced by a factor present in the photon flux • Rapidity distribution is assymetric due to the dominance of the ion as the photon emmiter

16. Results (Cross sections) • Diffractive charm and bottom photoproduction in pp and pPb collisions • 14 and 8.8 TeV LHC energies Largevalues to inclusive crosssections nanobarns(microbarns) b(c) DRP 7 x DDP

17. Comparison for pp predictions • Inclusive heavy quark photoproduction J. Raufensein and J. C. Peng, PRD67, 054008 (2003) smaller • Heavy quark production in two-photon interaction THIS WORK V. P. Gonçalves and M. V. T. Machado, EJPC 29, 37 (2003) larger • Inclusive DD heavy quark production M. V. T. Machado, PRD 76, 054006 (2007) smaller • Exclusive DD heavy quark production R. Maciula, R. Pasechnik and A. Szczurek PRD82, 114011 (2010) smaller

18. Conclusions • Cross sections for diffractive photoproduction of heavy quarks in pp and pA collisions • Resolved Pomeron model based on the diffractive factorization formalism • Pomeronwithpartonicsubstructure (describes HERA data verywell) • Sizeablevaluesat LHC energies • PredictionssmallerthanthoseobtainedconsideringDouble Pomeroninteractions • Constraintheunderlyingmodelfor thePomeron • Fundamental to predictobservableswhichwillbemeasured in h-h collisionsat LHC