Acoplamentos não-mínimos de dimensão cinco com violação da simetria de Lorentz nos setores eletrofraco e hadrônico

Abstract

One of the main tools currently used to address the Lorentz / CPT symmetries violation in physical systems is the minimum Standard Model Extension (SMEm), developed by Colladay & Kostelecky in 1997, which corresponds to an extension of the Standard Model with a group structure, SU (3) × SU (2) × U (1), encompassing terms that violate the Lorentz symmetry and sometimes the CPT symmetry in all sectors of the latter. The SMEm has been subject of investigation in several sectors, mainly in the CPT-odd and CPT-even electromagnetic sectors as well as in the fermion sector. Nonminimal SMEm extensions, involving higher derivatives, have been developed in both photon sector and fermion one. However, until the beginning of the activities of this thesis, no examples of LV nonminimal interactions in the electroweak and hadron sectors were known in the literature. Therefore, in order to fill this gap, we have introduced the first proposals of nonminimal couplings in these sectors. We have proposed two possibilities of dimension five, CPT-odd, nonminimal interactions between leptons and vector bosons in the context of the covariant derivative of the GSW (Glashow-Salam-Weinberg) model. The first possibility of NM coupling, in the sector U (1)Y

of the GSW model, has been introduced

through the covariant derivative: Dμ = ∂μ − igT · Wμ − i g ′ 2 Y Bμ + ig′ 2Y BμνC ν , with C ν being a fixed 4−vector that establishes a previleged direction in space-time, violating the Lorentz symmetry. A second gauge invariant nonminimal interaction in the SU (2)L

sector of the GSW

model can be proposed as Dμ = ∂μ − igT · Wμ − i g ′ 2 Y Bμ + ig′ 3 (T · Wμν) V ν , where V ν is a 4−vector that violates the Lorentz symmetry. We have first determined the LV contributions to the electroweak currents. Then, we have evaluated the LV corrections to the decay rates of the following mediators: Z0 → ̄l + l and W− → l + ν ̄l

. Using these results and the experimental uncertainty in the measurements, we have constrained the magnitude of the LV parameters, achieving upper bounds as tight as 10−5 (GeV ) −1 and 10−4 (GeV ) −1 . We have also proposed rank-1, rank-2, rank-3 and rank-4 LV NM couplings in the lagrangean density of the GSW model. We have found that, among these couplings, rank-1 and rank-3 ones do not present an EDM signature as occurs with rank-2 and rank-4 couplings. Using the electron EDM measurements, we obtain upper bounds on the order of up to 10−16 (GeV ) −1 for our VL parameters. Lastly, we have presented two dimension five, CPT-odd, nonminimal interactions in the Kroll, Lee and Zumino (KLZ) model, endowed with vector meson dominance (VMD), by means of the covariant derivative: Dμ = (∂μ + igρππρμ + ieAμ + igρ ̄ μνξ

ν + igF ̃ μνξ ν ), where ξ

ν plays the role

of 4−vector that violates the Lorentz symmetry. The NMC, igF ̃ μνξ ν , between the photon and the pion current has been introduced to preserve the concept of VMD in this LV model. We have determined the LV contributions to the decay rate of the decay ρ 0 → π − + π +

, as well as to the pion timelike form factor which yieldes LV corrections to the anomalous magnetic moment of the muon through the channel e −e + → π −π +

. Using these results and the uncertainties in the experimental measurements of this decay rate and the anomalous magnetic moment of the muon, we have obtained the following upper bounds to the magnitude of our VL parameter: gξ ̄ 0 < 5, 0 × 10−1 (GeV) −1 , gξ ̄ 0 < 2, 0 × 10−1 GeV−1.