Recent results in Lorentz and CPT tests
This talk summarizes some recent experimental constraints on Lorentz and CPT violation.
hep-ph↗
arXiv subjects
Alan Kostelecky
Publications and source records attributed to Alan Kostelecky.
Lorentz and CPT tests with spin-polarized solids
Experiments using macroscopic samples of spin-polarized matter offer exceptional sensitivity to Lorentz and CPT violation in the electron sector. Data from existing experiments with a spin-polarized torsion pendulum provide sensitivity in this sector rivaling that of all other existing experiments and could reveal spontaneous violation of Lorentz symmetry at the Planck scale.
hep-ph↗
Lorentz- and CPT-violating extension of the standard model
The formulation and some experimental implications of a general Lorentz-violating extension of the standard model are reviewed. The theory incorporates both CPT-preserving and CPT-breaking terms. It is otherwise a conventional quantum field theory, obtained under the assumption that Lorentz symmetry is spontaneously broken in an underlying model. The theory contains the usual standard-model gauge structure, and it is power-counting renormalizable. Energy and momentum are conserved. Despite the violation of Lorentz symmetry, the theory exhibits covariance under Lorentz transformations of the observer inertial frame. A general Lorentz-violating extension of quantum electrodynamics can be extracted. The standard-model extension implies potentially observable effects in a wide variety of experiments, including among others measurements on neutral-meson oscillations, comparative studies in Penning traps, spectroscopy of hydrogen and antihydrogen, bounds on cosmological birefringence, measurements of muon properties, clock-comparison tests, and observations of the baryon asymmetry.
hep-ph↗
Off-shell structure of the string sigma model
The off-shell structure of the string sigma model is investigated. In the open bosonic string, nonperturbative effects are shown to depend crucially on the regularization scheme. A scheme retaining the notion of string width reproduces the structure of Witten's string field theory and the associated unconventional gauge transformations.
hep-th↗
Bounds on CPT and Lorentz violation from experiments with kaons
Possible signals for indirect CPT violation arising in experiments with neutral kaons are considered in the context of a general CPT- and Lorentz-violating standard-model extension. Certain CPT observables can depend on the meson momentum and exhibit sidereal variations in time. Any leading-order CPT violation would be controlled by four parameters that can be separately constrained in appropriate experiments. Recent experiments bound certain combinations of these parameters at the level of about $10^{-20}$ GeV.
hep-ph↗
CPT and Lorentz tests with muons
Precision experiments with muons are sensitive to Planck-scale CPT and Lorentz violation that is undetectable in other tests. Existing data on the muonium ground-state hyperfine structure and on the muon anomalous magnetic moment could be analyzed to provide dimensionless figures of merit for CPT and Lorentz violation at the levels of $4\times 10^{-21}$ and $10^{-23}$.
hep-ph↗
Signals for CPT and Lorentz Violation in Neutral-Meson Oscillations
Experimental signals for indirect CPT violation in the neutral-meson systems are studied in the context of a general CPT- and Lorentz-violating standard-model extension. In this explicit theory, some CPT observables depend on the meson momentum and exhibit diurnal variations. The consequences for CPT tests vary significantly with the specific experimental scenario. The wide range of possible effects is illustrated for two types of CPT experiment presently underway, one involving boosted uncorrelated kaons and the other involving unboosted correlated kaon pairs.
hep-ph↗
Nonrelativistic Quantum Hamiltonian for Lorentz Violation
A method is presented for deriving the nonrelativistic quantum hamiltonian of a free massive fermion from the relativistic lagrangian of the Lorentz-violating standard-model extension. It permits the extraction of terms at arbitrary order in a Foldy-Wouthuysen expansion in inverse powers of the mass. The quantum particle hamiltonian is obtained and its nonrelativistic limit is given explicitly to third order.
hep-ph↗
Constraints on Lorentz violation from clock-comparison experiments
Constraints from clock-comparison experiments on violations of Lorentz and CPT symmetry are investigated in the context of a general Lorentz-violating extension of the standard model. The experimental signals are shown to depend on the atomic and ionic species used as clocks. Certain experiments usually regarded as establishing comparable bounds are in this context sensitive to different types of Lorentz violation. Some considerations relevant to possible future measurements are presented. All these experiments are potentially sensitive to Lorentz-violating physics at the Planck scale.
hep-ph↗
Theory and Tests of CPT and Lorentz Violation
A general Lorentz-violating extension of the standard model of particle physics, allowing for both CPT-even and CPT-odd effects, is described. Some of its theoretical aspects and experimental implications are summarized.
hep-ph↗
Radiatively Induced Lorentz and CPT Violation in Electrodynamics
In a nonperturbative formulation, radiative corrections arising from Lorentz and CPT violation in the fermion sector induce a definite and nonzero Chern-Simons addition to the electromagnetic action. If instead a perturbative formulation is used, an infinite class of theories characterized by the value of the Chern-Simons coefficient emerges at the quantum level.
hep-ph↗
The Status of CPT
A short review is given of some theoretical approaches to CPT violation. A potentially realistic possibility is that small apparent breaking of CPT and Lorentz symmetry could arise at the level of the standard model from spontaneous symmetry breaking in an underlying theory. Some experimental constraints are described.
hep-ph↗
Testing CPT and Lorentz Symmetry with Neutral-Meson Oscillations and QED Experiments
This talk summarizes some theoretical features and experimental implications of a general Lorentz-violating extension of the minimal SU(3) x SU(2) x U(1) standard model that allows for both CPT-even and CPT-odd effects. The theory would arise as the low-energy limit of a fundamental theory that is Lorentz and CPT covariant but in which spontaneous Lorentz breaking occurs. The use of neutral-meson oscillations and various QED systems to bound the apparent CPT and Lorentz violations is described.
hep-ph↗
Hydrogen and Antihydrogen Spectroscopy for Studies of CPT and Lorentz Symmetry
A theoretical study of possible signals for CPT and Lorentz violation arising in hydrogen and antihydrogen spectroscopy is described. The analysis uses a CPT- and Lorentz-violating extension of quantum electrodynamics, obtained from a general Lorentz-violating extension of the minimal standard model with both CPT-even and CPT-odd terms. Certain 1S-2S transitions and hyperfine Zeeman lines exhibit effects at leading order in small CPT-violating couplings.
hep-ph↗
Testing CPT and Lorentz Symmetry with Protons and Antiprotons in Penning Traps
A theoretical analysis is performed of Penning-trap experiments comparing protons and antiprotons to test CPT and Lorentz symmetry through measurements of anomalous magnetic moments and charge-to-mass ratios. Possible CPT and Lorentz violations arising at a fundamental level are treated in the context of a general extension of the standard model of particle physics and its restriction to quantum electrodynamics. In a suggested experiment measuring anomaly frequencies a bound on CPT violation of 10^{-23} for a relevant figure of merit is attainable. Experiments comparing cyclotron frequencies are sensitive within this theoretical framework to different kinds of Lorentz violation that preserve CPT. Constraints could be obtained on one figure of merit at 10^{-24} and on another in a related experiment with H- ions and antiprotons at the level of 10^{-25}.
hep-ph↗
Testing CPT and Lorentz Symmetry with Electrons and Positrons in Penning Traps
We present a theoretical analysis of signals for CPT and Lorentz violation in g-2 and charge-to-mass-ratio experiments on electrons and positrons in Penning traps. Experiments measuring anomaly frequencies are found to be the most sensitive to CPT violation. We find that the conventional figure of merit for CPT breaking, involving the difference of the electron and positron g factors, is inappropriate in this context, and an alternative is introduced. Bounds of approximately one part in 10^{20} are attainable.
hep-ph↗
CPT and Lorentz Tests in the Standard Model
A general Lorentz-violating extension of the minimal SU(3) x SU(2) x U(1) standard model is described, including both CPT-even and CPT-odd terms. Some theoretical properties and experimental implications are given. The extension can be regarded as a low-energy limit of a physically relevant Lorentz-covariant fundamental theory in which spontaneous Lorentz violation occurs.
hep-ph↗
CPT and Lorentz Tests in Hydrogen and Antihydrogen
Signals for CPT and Lorentz violation at the Planck scale may arise in hydrogen and antihydrogen spectroscopy. We show that certain 1S-2S and hyperfine transitions can exhibit theoretically detectable effects unsuppressed by any power of the fine-structure constant.
hep-ph↗