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Register a new userBounds on Plack-scale deformation of CPT from lifetimes and interference
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Authors
Wojciech Wislicki
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Deformed relativistic kinematics, expected to emerge in a flat-spacetime limit of quantum gravity, predicts violation of discrete symmetries at energy scale in the vicinity of the Planck mass. Momentum-dependent deformations of the C, P and T invariance are derived from the k{appa}-deformed Poincare algebra. Deformation of the CPT symmetry leads to a subtle violation of Lorentz symmetry. This entails some small but measurable phenomenological consequences, as corrections to characteristics of time evolution: particle lifetimes or frequency of flavour oscillations in two-particle states at high energy. We argue here that using current experimental precisions on the muon lifetime one can bound the deformation parameter k{appa} > 10^14 GeV at LHC energy and move this limit even to 10^16 GeV at Future Circular Collider, planned at CERN. Weaker limits on deformation can be also obtained from interference of neutral mesons. In case of B0s from {Upsilon} decay it amounts to k{appa} > 10^8 GeV at confidence level 99%.
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We carry out a systematic study of the bounds that can be set on Planck-scale deformations of relativistic symmetries and CPT from precision measurements of particle and antiparticle lifetimes. Elaborating on our earlier work [1] we discuss a new form of departure from CPT invariance linked to the possibility of a non-trivial geometry of four-momentum and its consequences for the particle and antiparticle mass-shells and decay probabilities. Our main result is a collection of experimental bounds that can be obtained for the deformation parameter of the theoretical model under consideration based on current data and sensitivities of planned experiments at high energies.
We show that deformed relativistic kinematics, expected to emerge in a flat-spacetime limit of quantum gravity, predicts different lifetimes for particles and their antiparticles. This phenomenon is a consequence of Planck-scale modifications of the action of discrete symmetries. In particular we focus on deformations of the action of CPT derived from the kappa-Poincare algebra, the most studied example of Planck-scale deformation of relativistic symmetries. Looking at lifetimes of muons and anti-muons we are able to derive an experimental bound on the deformation parameter of kappa > 4x10^14 GeV from measurements at the LHC. Such bound has the potential to reach the value of kappa > 2x10^16 GeV using measurements at the planned Future Circular Collider (FCC).
In a broad class of gravity theories, the equations of motion for vacuum compactifications give a curvature bound on the Ricci tensor minus a multiple of the Hessian of the warping function. Using results in so-called Bakry--Emery geometry, we put rigorous general bounds on the KK scale in gravity compactifications in terms of the reduced Planck mass or the internal diameter. We reexamine in this light the local behavior in type IIA for the class of supersymmetric solutions most promising for scale separation. We find that the local O6-plane behavior cannot be smoothed out as in other local examples; it generically turns into a formal partially smeared O4.
We report the strictest observational verification of CPT invariance in the photon sector, as a result of gamma-ray polarization measurement of distant gamma-ray bursts (GRBs), which are brightest stellar-size explosions in the universe. We detected the gamma-ray polarization of three GRBs with high significance, and the source distances may be constrained by a well-known luminosity indicator for GRBs. For the Lorentz- and CPT-violating dispersion relation E_{pm}^2=p^2 pm 2xi p^3/M_{Pl}, where pm denotes different circular polarization states of the photon, the parameter xi is constrained as |xi|<O(10^{-15}). Barring precise cancellation between quantum gravity effects and dark energy effects, the stringent limit on the CPT-violating effect leads to the expectation that quantum gravity presumably respects the CPT invariance.
In the framework of a baryon-number-violating effective Lagrangian, we calculate improved lower bounds on partial lifetimes for proton and bound neutron decays, including $p to ell^+ ell^+ ell^-$, $n to bar u ell^+ ell^-$, $p to ell^+ ubar u$, and $n to bar u bar u u$, where $ell$ and $ell$ denote $e$ or $mu$, with both $ell = ell$ and $ell e ell$ cases. Our lower bounds are substantially stronger than the corresponding lower bounds from direct experimental searches. We also present lower bounds on $(tau/B)_{p to ell^+gamma}$, $(tau/B)_{n to bar u gamma}$, $(tau/B)_{p to ell^+ gammagamma}$, and $(tau/B)_{n to bar u gammagamma}$. Our method relies on relating the rates for these decay modes to the rates for decay modes of the form $p to ell^+ M$ and $n to bar u M$, where $M$ is a pseudoscalar or vector meson, and then using the experimental lower bounds on the partial lifetimes for these latter decays.
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