Direct CP violation of $B\to l\nu$ in unparticle physics

Abstract

We have investigated the effects of unparticles in decays $B\to l\nu$. 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 $\mathrm{Br}(B\to \tau \nu )$ and $\nu e$ elastic scattering. If both unparticle-lepton coupling universality and unparticle-quark coupling universality are assumed the constraint from $Br(\pi \to \mu \nu )$ leads that the direct CP violation in $B\to l\nu$ can only reach at most 8% and 1% for scalar and vector unparticle contributions respectively if $d_{\mathcal{U}}<2$. If the direct CP violation is observed in the future it would give strong evidence for the existence of unparticle stuff.

Comments: 9 pages, 2 figures, to appear in PRD