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Register a new userCharm-System Tests of CPT with FOCUS
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R.W. Gardner
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We discuss a search for CPT violation in neutral charm meson oscillations. The data come from the Fermilab fixed-target experiment FOCUS. While flavor mixing in the charm sector is predicted to be small by the standard model, it is still possible to investigate CPT violation through study of the proper time dependence of the asymmetry in right-sign decay rates for D0 and D0-bar. Using present limits for D0-D0-bar mixing we infer bounds on charm CPT violation using data from FOCUS.
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The ongoing experimental efforts in the high energy and high precision communities keep providing evidence for CPT, a fundamental symmetry holding in any local Lorentz invariant theory. We suggest possible interconnections between different CPT violating parameters. Specifically, the very precise test of CPT in the $K^0-bar K^0$ system suggests--though definitely does not imply--that CPT violations in other observable parameters (mass, width, charge, magnetic moments, etc.) are much smaller than the directly measured bounds.
The status of Lorentz- and CPT-violation searches using measurements of the anomalous magnetic moment of the muon is reviewed. Results from muon g-2 experiments have set the majority of the most stringent limits on Standard- Model Extension Lorentz and CPT violation in the muon sector. These limits are consistent with calculations of the level of Standard-Model Extension effects required to account for the current 3.7{sigma} experiment-theory discrepancy in the muons g-2. The prospects for the new Muon g-2 Experiment at Fermilab to improve upon these searches is presented.
The FOCUS photoproduction experiment took data in the ninenties and produced a wealth of results in charm physics. Some of the studies were seminal for contemporary experiments, and even paved the way for the technology of many charm and beauty analysis tools.
We present a summary of recent results on CP violation and mixing in the charm quark sector based on a high statistics sample collected by photoproduction experiment FOCUS (E831 at Fermilab). We have measured the difference in lifetimes for the $D^0$ decays: $D^0 to K^-pi^+$ and $D^0 to K^-K^+$. This translates into a measurement of the $y_{CP}$ mixing parameter in the $d0d0$ system, under the assumptions that $K^-K^+$ is an equal mixture of CP odd and CP even eigenstates, and CP violation is negligible in the neutral charm meson system. We verified the latter assumption by searching for a CP violating asymmetry in the Cabibbo suppressed decay modes $D^+ to K^-K^+pi^+$, $D^0 to K^-K^+$ and $D^0 to pi^-pi^+$. We show preliminary results on a measurement of the branching ratio $Gamma(D^{*+}to pi^+ (K^+pi^-))/Gamma(D^{*+}to pi^+ (K^-pi^+))$.
Clock-comparison experiments are among the sharpest existing tests of Lorentz symmetry in matter. We characterize signals in these experiments arising from modifications to electron or nucleon propagators and involving Lorentz- and CPT-violating operators of arbitrary mass dimension. The spectral frequencies of the atoms or ions used as clocks exhibit perturbative shifts that can depend on the constituent-particle properties and can display sidereal and annual variations in time. Adopting an independent-particle model for the electronic structure and the Schmidt model for the nucleus, we determine observables for a variety of clock-comparison experiments involving fountain clocks, comagnetometers, ion traps, lattice clocks, entangled states, and antimatter. The treatment demonstrates the complementarity of sensitivities to Lorentz and CPT violation among these different experimental techniques. It also permits the interpretation of some prior results in terms of bounds on nonminimal coefficients for Lorentz violation, including first constraints on nonminimal coefficients in the neutron sector. Estimates of attainable sensitivities in future analyses are provided. Two technical appendices collect relationships between spherical and cartesian coefficients for Lorentz violation and provide explicit transformations converting cartesian coefficients in a laboratory frame to the canonical Sun-centered frame.
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