Study of the penguin-dominated decay B0 s - K 0K 0 at LHCb

  1. Álvarez Cartelle, Paula
Supervised by:
  1. Abraham Gallas Torreira Director
  2. Bernardo Adeva Andany Director

Defence university: Universidade de Santiago de Compostela

Fecha de defensa: 21 November 2014

Committee:
  1. Guy Wilkinson Chair
  2. José Angel Hernando Morata Secretary
  3. Joaquim Matias Espona Committee member
  4. Diego Martinez Santos Committee member
  5. Tim Gershon Committee member
Department:
  1. Department of Particle Physics

Type: Thesis

Abstract

This thesis is devoted to the search for and subsequent analysis of the decay channel B0s -> K*0 anti-K*0,using the first data acquired by LHCb during 2010 and 2011 from the LHC proton-proton collisions at a centre-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 35/pb and 1/pb respectively. As a result of the work presented here, the first observation of the B0s -> K*0 anti-K*0 decay was performed. With the extended data sample collected in 2011, a combined angular and mass analysis was carried out, in order to asses the longitudinal polarisation fractions of the K*0, obtaining f_L = 0.201 +/- 0.057(stat.) +/- 0.040(syst.). The branching fraction for this decay was also measured to be BR(B0s -> K*0 anti-K*0) = (10.6 +/- 1.8(stat.) +/- 1.0(syst.) +/- 0.6 (f_d/f_s)) x 10^{â^6},in agreement with the Standard Model prediction. All of the triple product and CP direct asymmetries measurable in the time-integrated and flavour-untagged analysis of B0s -> K+ pi- K- pi+ were also determined. No signs of CP violation was found, in agreement with the Standard Model expectation.