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Register a new userConstraining unparticle physics from $CP$ violation in Cabibbo-favored decays of D mesons
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According to the standard model, the Cabibbo-favored (CF) decays are $CP$ conserve at tree level. Observation of any finite $CP$ asymmetry can be received as a signal of new physics. In CF charm meson decays, $ D^0 rightarrow K^- pi^+ $ and $ D^+ rightarrow K_s^0 pi^+ $, the following experimental values for their $CP$ asymmetry are reported, respectively: ($0.3 pm 0.7$) % and ($-0.41 pm 0.09$) %. The value of the later can be attributed to the mixing of $ K^0 $ and $ overline{K^0} $, however, its contribution is about ($-0.332 pm 0.006 $) %. In this paper, we use these experimental results to constrain the unparticle stuff as a new physics which may contribute to these $CP$ asymmetries.
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A U-spin relation among four ratios of amplitudes for $D^0 to pi^+K^-$, $K^+pi^-$, $K^+K^-, pi^+pi^-$, including first, second and third order U-spin breaking, has been derived recently with a precision of $10^{-3}$. We study effects of new $|Delta C|=1$ operators on this relation. We find that it is not affected by U-spin scalar operators, including QCD penguin and chromomagnetic dipole operators occurring in supersymmetric and extra-dimensional models. The relation is modified by new $U=1$ operators with a sensitivity of a few percent characteristic of second order U-spin breaking. Combining this relation with CP asymmetries in $D^0to K^+K^-, pi^+pi^-$ leads to a more solid constraint on $U=1$ operators than from asymmetries alone.
We have investigated the effects of unparticles in decays $B to l u$. It is found that the direct CP violation in the decays, which is zero in SM, can show up due to the CP conserving phase intrinsic in unparticle physics. For $l=tau$, the direct CP asymmetry can reach 30% for the scalar unparticle contribution, and 100% for the longitudinal vector unparticle contribution under the constraints of ${rm Br}(Btotau u)$ and $ u e$ elastic scattering. If both unparticle-lepton coupling universality and unparticle-quark coupling universality are assumed the constraint from $Br(pito mu u)$ leads that the direct CP violation in $Bto l u$ can only reach at most 8% and 1% for scalar and vector unparticle contributions respectively if $d_{cal U} < 2$. If the direct CP violation is observed in the future it would give strong evidence for the existence of unparticle stuff.
We report on a search for direct CP asymmetry in the singly Cabibbo-suppressed decay D+- --> K+ K- pi+- using a data sample of 476 fb-1 accumulated with the BaBar detector running at and just below the Y(4S) resonance. The CP-violating decay rate asymmetry A_CP is determined to be (0.35 +- 0.30 +- 0.15)%. Model-dependent and model-independent Dalitz plot analysis techniques are used to search for CP-violating asymmetries in the various intermediate states.
The phenomenon of mixing in neutral meson systems has now been observed in all flavours, but only in the past year in the D0 system. The standard model anticipated that, for the charm sector, the mixing rate would be small, and also that CP violation, either in mixing or in direct decay, would be below the present levels of observability. It is hoped that further study of these phenomena might reveal signs of new physics. A review of recently available, experimental results is given.
The LHCb Collaboration has recently measured the difference of time-integrated $CP$ asymmetry in $D^{0}rightarrow K^{+}K^{-}$ and $D^{0}rightarrow pi^{+}pi^{-}$ decays, more precisely. The reported value is $ Delta A_{CP}=-0.10 pm 0.08 (text{stat}) pm 0.03 (text{syst})% $ which indicates no evidence for $CP$ violation. We consider the possible unparticle physics contribution in this quantity and by using the LCHb data try to constrain the parameter space of unparticle stuff.
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