Model independent FCNC top physics at the LHC

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Model independent FCNC top physics at the LHC

• Pedro Ferreira
• ISEL e CFTC, Universidade de Lisboa

Jornadas do LIP 2008, 12/1/08
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THE WORK

• P. M. Ferreira, O. Oliveira and R. Santos,
  PHYSICAL REVIEW D 73, 034011 (2006)
• P. M. Ferreira and R. Santos, PHYSICAL REVIEW D
  73, 054025 (2006)
• P. M. Ferreira and R. Santos, PHYSICAL REVIEW D
  74, 014006 (2006)
• P. M. Ferreira, R. B. Guedes and R. Santos,
  PHYSICAL REVIEW D 75, 055015 (2007)
• Contribution to the Yellow Report for the CERN
  Workshop Flavour in the Era of the LHC (2007)
  (in the arXiv on Monday!)
• Two more being produced as we speak

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ProjectsPOCI/FP/81950/2007
PTDC/FIS/70156/2006POCI/FP/63926/2005POCI/FP/63
420/2005POCTI/FIS/59741/2004PDCTI/FP/FNU/50155/2
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THE TEAM
People Juan Aguilar-Saavedra, Augusto Barroso,
João Bastos, João Carvalho, Matilde Castanheira,
Nuno Castro, Pedro Ferreira, Miguel Fiolhais,
Agostinho Gomes, Renato Guedes, Amélia Maio,
Paulo Martins, Rita Monteiro, Miguel Oliveira,
Orlando Oliveira, Sancho Oliveira, António
Onofre, Rui Santos, Sergey Slabospitsky, Filipe
Veloso, Helmut Wolters, Miguel Won.
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top FCNCcombination
THE CONNECTIONS
Granada
Southampton
tbW measurements(BSM physics)
NExT
tbW measurements
CFTC
LIP
RAL
Generators, tbW physics
RHUL LONDON
Valencia
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EFFECTIVE OPERATOR FORMALISM

• New physics generated in extensions of the
  standard model would manifest itself at lower
  energy scales in the form of effective operators
  of dimension superior to 4.
• Complete list of dimension 5 and 6 effective
  operators Buchmüller e Wyler, Nucl. Phys. B268
  (1986) 621.
• Dimension 5 operators violate baryon/lepton
  number.

Dimension 6 operators a great many of them.
We are interested in processes of single top
production via flavour changing neutral currents
(FCNCs) at the LHC.
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EFFECTIVE OPERATOR FORMALISM
All terms are invariant under the SM gauge group
? is the energy scale of new physics. This
formalism allows us to make predictions in a
model-independent manner.

• To select among the many dimension 6 terms, we
  employed some physical selection criteria
• The operators must contribute to FCNCs
  involving the top quark and the strong
  interaction, with impact on single top
  production.
• They must not have sizeable contributions to
  physics below the TeV scale, so as to not ruin
  the successful predictions of the SM.

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Strong FCNC contributions decays t ? q g, with
q u, c.

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Weak FCNC contributions decays t ? q Z and t ?
q ?

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RESULTS
We found a direct proportionality between the
cross sections of several FCNC processes and the
FCNC Branching ratios. For instance, for single
top production of a top quark at the LHC (in
picobarn)
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RESULTS
In the SM, BR(t?cg) 10-12 In other models, it
can reach BR(t?cg) 10-4
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The branching ratios of t ? q Z and t ? q ? are
related
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RESULTS FOR t ? PRODUCTION
Analysing the combined effects of FCNC in the
strong and weak sector yields information on the
sum of the branching ratios.
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DIFFERENTIAL CROSS SECTIONS ALLOW TO DISTINGUISH
STRONG AND WEAK FCNC CONTRIBUTIONS
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THE FUTURE

• Continue (and survive) the fruitful
  collaboration between theoreticians and
  experimentalists.
• Top gluon FCNC interactions have been introduced
  in an event generator (latest version of TopReX).
  We wish to implement ALL FCNC interactions in
  generators and study their effects in LHC
  physics.
• Publish loads of very nice papers

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