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Register a new userUnparticle Physics Effects on D0-anti-D0 Mixing
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The mixing of $K^0-bar{K^0}$, $D^0-bar{D^0}$ and $B_{(s)}^0-bar{B^0_{(s)}}$ provides a sensitive probe to explore new physics beyond the Standard Model. The scale invariant unparticle physics recently proposed by Georgi can induce flavor-changing neutral current and contribute to the mixing at tree level. We investigate the unparticle effects on $B^0-bar{B^0}$ and $D^0-bar{D^0}$ mixing. Especially, the newly observed $D^0-bar{D^0}$ mixing sets the most stringent constraints on the coupling of the unparticle to quarks.
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In current searches for D0 anti-D0 mixing, the time evolution of ``wrong-sign decays is used to distinguish between a potential mixing signal and the dominant background from doubly-Cabibbo-suppressed decays. A term proportional to $Delta Mt$ in the expression for the time evolution is often neglected in theoretical discussions and experimental analyses of these processes. We emphasize that, in general, this term does not vanish even in the case of CP invariance. Furthermore, CP invariance is likely to be violated if the rate of D0 anti-D0 mixing is close to the experimental bound. The consequence of either of these two facts is that the strongest existing measured bound is not applicable for constraining New Physics.
We present a brief review of CPV and mixing measurements in the charm sector, with emphasys in results published or presented since the previous edition of the Physics in Collision Symposia.
Measurements of charm mixing parameters from the decay-time-dependent ratio of D0->K+pi- to D0->K-pi+ rates and the charge-conjugate ratio are reported. The analysis uses data, corresponding to 3 fb^{-1} of integrated luminosity, from proton-proton collisions at 7 and 8 TeV center-of-mass energies recorded by the LHCb experiment. In the limit of charge-parity (CP) symmetry, the mixing parameters are determined to be x^2=(5.5 +- 4.9)x10^{-5}, y= (4.8 +- 1.0)x10^{-3}, and R_D=(3.568 +- 0.066)x10^{-3}. Allowing for CP violation, the mixing parameters are determined separately for D0 and D0bar mesons yielding A_D = (-0.7 +- 1.9)%, for the direct CP-violating asymmetry, and 0.75 < |q/p|< 1.24 at the 68.3% confidence level, where q and p are parameters that describe the mass eigenstates of the neutral charm mesons in terms of the flavor eigenstates. This is the most precise determination of these parameters from a single experiment and shows no evidence for CP violation.
The D0 meson can decay to the wrong sign K+pi- state either through a doubly Cabibbo suppressed decay or via mixing to the D0bar state followed by the Cabibbo favoured decay D0bar -> K+ pi-. We measure the rate of wrong sign decays relative to the Cabibbo favoured decay to (0.383 +- 0.044 +- 0.022)% and give our sensitivity to a mixing signal.
We present recent DO results based on approximately 1 fb$^{-1}$ of $p bar{p}$ collisions at $sqrt{s} = 1.96$ TeV recorded at the Fermilab Tevatron. Preliminary results on a search for the flavor changing neutral current process $D^+to pi^+mu^+mu^-$, a measurement of the CP violation parameter in $B$ mixing, $epsilon_B$, and a two sided limit on the $B_s$ oscillation frequency $Delta m_s$ are presented. The limits on $epsilon_B$ and ${cal B}(D^+to pi^+mu^+mu^-)$ are the worlds best limits. The two sided bound on $Delta m_s$ is the first direct indication by a single experiment that $Delta m_s$ is bounded from above.
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