[seminar] [seminar RBI-T-WINNING] L. Vale, 25.04., (ponedjeljak) 14 sati (c.t.) predavaona krila Ivana Supeka

[Kornelija Passek-Kumericki]

                        SEMINAR  TEORIJSKE  FIZIKE


                          RBI-T-WINNING seminari

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Revisiting short-distance QCD corrections for kaon mixing in Left-Right Models


Luiz Vale
Laboratoire de Physique Théorique, Orsay


    Datum:  ponedjeljak, 25. travnja 2016.
    Vrijeme: 14 sati c.t.
    Mjesto: IRB, predavaona krila Ivana Supeka



Sazetak:

Left-Right (LR) models are extensions of the Standard Model where left-right symmetry
is restored at high energies, and which are strongly constrained by kaon mixing
described in the framework of the |Delta S| = 2 effective Hamiltonian. I consider the
short-distance QCD corrections to this Hamiltonian both in the Standard Model (SM) and
in LR models. The leading logarithms occurring in these short-distance corrections can
be resummed within a rigourous Effective Field Theory (EFT) approach integrating out
heavy degrees of freedom progressively, or using an approximate simpler "method of
regions" identifying the ranges of loop momentum generating large logarithms in the
relevant two-loop diagrams. I compare the two approaches in the SM at next-to-leading
order, finding a very good agreement when one scale dominates the problem, but only a
fair agreement in the presence of a large logarithm at leading order. Then I compute
the short-distance QCD corrections for LR models at next-to-leading order using the
"method of regions," and I compare the results with the EFT approach with two charm
quarks for the WW' box (together with additional diagrams forming a gauge-invariant
combination), where a large logarithm occurs already at leading order. I conclude by
providing next-to-leading-order estimates for cc, ct, tt contributions in LR models.



Voditeljica seminara: Kornelija Passek-Kumericki (passek at irb dot hr)
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