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Heavy flavour jet physics and LHCb

Heavy flavour jet physics and LHCb Implications of LHCb measurements and future prospect, CERN, 14-16 Oct 2013. Germán Rodrigo. IFIC INSTITUT DE FISICA CORPUSCULAR. Collinear factorization in pQCD. pQCD for hard-scattering processes based on universality :

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Heavy flavour jet physics and LHCb

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  1. Heavy flavour jet physics and LHCb Implications of LHCb measurements and future prospect, CERN, 14-16 Oct 2013 Germán Rodrigo IFIC INSTITUT DE FISICA CORPUSCULAR

  2. Collinearfactorization in pQCD • pQCD for hard-scattering processes based on universality: • the sole uncancelledIR divergences are due to partonic states whose momenta are collinear to the collider partons • removed by redefinition of bare partondensities (PDFs) • assumes that colliding partons do not have any intrinsic transverse momentum

  3. Forward jet production • At least one of the colliding partons at small-x longitudinal momenta • PDFs poorly known at small-x. • Transverse momentum non-negligible  collinear factorization for fixed order pQCD (LO or NLO) does not work well. • Large logarithms must be resummed BFKL or factorization • Dominated by multi-gluon emission off the t-channel.

  4. factorization • High-energy scattering of two partons () • Differential cross-section as a function of transverse momenta (Mellin space) • Gluon Green´s function : Regge-gluon exchanges • Impact factors : process dependent, free of high-energy gluon exchanges, but collinear singularities due to the initial massless partons which need to be factored out • Scheme dependent scale [Ciafaloni,GR] From colour coherence: rapidity of extra gluon radiation cannot exceed that of the final quark

  5. Forward heavy quark jet production • New particles in discovery processes • Reduce background in Higgssearches in vector boson fusion channels, e.g. • Decays of highly boosted heavy states • QCD at an extreme energy regime • Valuable information on the gluon density at small-x, which is poorly constrained from DIS • Promt neutrino flux incosmic ray cascades from the decay of charm and bottom dominant at large energies (GeV) over the conventional neutrino flux from the decay of pions, kaons, …[Enberg, Reno, Sarcevic]

  6. Heavy quark impact factor at NLx [Ciafaloni,GR] • At leading order (Lx) • At next-to-leading log (NLx) • where • with the gluon Regge trajectory • Free from double logs: and • Collinear as predicted by DGLAP

  7. Heavy quark impact factor at NLx revisited [Deak, Chachamis,GR]

  8. Single heavy quark forward production [Deak, Chachamis,Salas, Sabio-Vera, GR] • Single bottom (charm) quark forward production, with soft gluon radiation between the heavy quark and the other parent proton at NLx • The unintegrated gluon density • whose evolution is determined by BFKL

  9. Single bottom quark forward production

  10. Conclusions • Forward production of heavy quarks offers interesting prospects for discovery processes. • and also access to QCD in a new energy regime: probe small-x where PDFs are poorly known. • First steeps towards single bottom/charm quark forward production at NLx

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