Searches for violation of Lorentz invariance in $\mathrm{t\bar{t}}$ production using dilepton events in proton-proton collisions at $\sqrt{s}$ = 13 TeV

The CMS collaboration
CMS-TOP-22-007, 2024.

A search for violation of Lorentz invariance in the production of top quark pairs ($\mathrm{t\bar{t}}$) is presented. The measured normalized differential $\mathrm{t\bar{t}}$ production cross section, as function of the sidereal time, is examined for potential modulations induced by Lorentz-invariance breaking operators in an effective field theory extension of the standard model (SM). The cross section is measured from collision events collected by the CMS detector at a center-of-mass-energy of 13 TeV, corresponding to an integrated luminosity of 77.8 fb$^{-1}$, and containing one electron and one muon. The results are found to be compatible with zero, in agreement with the SM, and are used to bound the Lorentz-violating couplings to be in ranges of 1 - 8 $\times$ 10$^{-3}$ at 68% confidence level. This is the first precision test of the isotropy in special relativity with top quarks at the LHC, restricting further the bounds on such couplings by up two orders of magnitude with respect to previous searches conducted at the Tevatron.

  • Figure 3


    The normalized differential cross section for $t\bar{t}$ as a function of sidereal time, using combined 2016--2017 data. The error bars...

  • Figure 4


    Comparison of systematic and statistical uncertainties, where the former are grouped according to the treatment of time dependence: uniform (flat...

  • Table 3


    Expected and observed 68\% confidence level interval measured for the SME fits of single coefficients while the others are fixed...

  • Figure 6


    Fitted SME coefficients and their uncertainties at 1$\sigma$ and 2$sigma$, measured in fits of single coefficients while the coefficients corresponding...

  • Figure 7


    Uncertainty breakdown for SME fits of single coefficients while the coefficients corresponding to the three other directions are left floating,...

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