Search for CPT Violation with the FOCUS Experiment and Measurement of $\Lambda_b$ lifetime in the decay $\Lambda_b\to J/\psi \Lambda$ with the D\O Experiment

TL;DR

This paper searches for CPT violation in charm meson oscillations and measures the \\Lambda_b and B0 lifetimes using data from FOCUS and DØ experiments, providing new limits on CPT violation and the first fully reconstructed \\Lambda_b lifetime measurement.

Contribution

It presents the first fully reconstructed decay channel measurement of the \\Lambda_b lifetime and sets new limits on CPT violation parameters in charm meson oscillations.

Findings

95% CL limits on CPT violation parameters: -0.0068 to 0.0234

Measured \\Lambda_b lifetime: 1.36 \\pm 0.3 ps

Measured B0 lifetime: 1.43 \\pm 0.12 ps

Abstract

We have performed a search for CPT violation in neutral charm meson oscillations using data from the FOCUS Experiment. 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 a study of the proper time dependence of a CPT asymmetry in right-sign decay rates for $D^0\to K^-\pi^+$ and $\d0b\to K^+\pi^-$. This asymmetry is related to the CPT violating complex parameter $\xi$ and the mixing parameters $x$ and $y$: $A_{CPT}\propto{\rm Re} \xi y-{\rm Im} \xi x$. Our 95% confidence level limit is $-0.0068<{\rm Re} \xi y-{\rm Im} \xi x<0.0234$. Within the framework of the Standard Model Extension incorporating general CPT violation, we also find 95% confidence level limits for the expressions involving coefficients of Lorentz violation. We present measurements of the \lb lifetime in the exclusive decay channel \lbdec with $J/\psi \to \mu^+ \mu^-$ and $\Lambda \to p \pi^-$, the $B^0$ lifetime in the decay \bddecks with $J/\psi \to mu^+ \mu^-$ and $K^0_{S} \to \pi^+ \pi^-$, and the ratio of these lifetimes. The analysis is based on approximately 225 pb$^{-1}$ of data recorded with the D{\O}detector in $p bar{p}$ collisions at $\sqrt{s} =1.96$ TeV. The \lb lifetime is determined to be $\tau(\Lambda^0_b) = 1.36 \pm 0.3 ps$, the $B^0$ lifetime $\tau(\Lambda^0_b) = 1.43 \pm 0.12 ps$, and the ratio $\fr ac{\tau(\Lambda_b)}{\tau(B_d)}=0.95\pm0.22$. In contrast with previous measurements using semileptonic decays, this is the first determination of the \lb lifetime based on a fully reconstructed decay channel.