Germán Rodrigo Heavy flavour jet physics LHCb prospects, CERN, Oct 2013 1

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Heavy flavour jet physics and LHCbImplications of LHCb measurements and future prospect, CERN, 14-16 Oct 2013

Germán Rodrigo

I F I CI N S TI TU T D E F I S I C A C O R P U S C U L A R

Germán Rodrigo Heavy flavour jet physics LHCb prospects, CERN, Oct 2013 2

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Collinear factorization in pQCD

pQCD for hard-scattering processes based on universality:

the sole uncancelled IR divergences are due to partonic states whose momenta are collinear to the collider partons

removed by redefinition of bare parton densities (PDFs)

assumes that colliding partons do not have any intrinsic transverse momentum

Germán Rodrigo Heavy flavour jet physics LHCb prospects, CERN, Oct 2013 3

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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.

𝑝1=𝑥1√ 𝑠/2𝑝2=𝑥2√𝑠 /2

Germán Rodrigo Heavy flavour jet physics LHCb prospects, CERN, Oct 2013 4

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factorizationHigh-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

Germán Rodrigo Heavy flavour jet physics LHCb prospects, CERN, Oct 2013 5

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Forward heavy quark jet productionNew particles in discovery processes

Reduce background in Higgs searches 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 in cosmic 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]

Germán Rodrigo Heavy flavour jet physics LHCb prospects, CERN, Oct 2013 6

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Heavy quark impact factor at NLx

𝒌

At leading order (Lx)

At next-to-leading log (NLx)

[Ciafaloni,GR]

where

with the gluon Regge trajectory

Free from double logs: and Collinear as predicted by DGLAP

Germán Rodrigo Heavy flavour jet physics LHCb prospects, CERN, Oct 2013 7

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

Germán Rodrigo Heavy flavour jet physics LHCb prospects, CERN, Oct 2013 8

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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

Germán Rodrigo Heavy flavour jet physics LHCb prospects, CERN, Oct 2013 9

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Single bottom quark forward production

Germán Rodrigo Heavy flavour jet physics LHCb prospects, CERN, Oct 2013 10

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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

Conclusions