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Evidence for an anomalous like-sign dimuon charge asymmetry

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Article number 081801 16/08/2010 Physical review letters 8 105 7 Published English

Abstract

We measure the charge asymmetry $A\equiv(N^{++} - N^{--})/(N^{++} + N^{--})$ of like-sign dimuon events in 6.1~fb$^{-1}$ of $p\bar{p}$ collisions recorded with the D0 detector at a center-of-mass energy $\sqrt{s}=1.96$~TeV at the Fermilab Tevatron collider. From $A$ we extract the like-sign dimuon charge asymmetry in semileptonic $b$-hadron decays: $\aslb=-0.00957\pm0.00251\thinspace({\rm stat})\pm0.00146\thinspace({\rm sys})$. It differs by 3.2~standard deviations from the standard model prediction $\aslb({\rm SM})=(-2.3^{+0.5}_{-0.6})\times10^{-4}$, and provides first evidence of anomalous $CP$ violation in the mixing of neutral $B$ mesons.

Bibliographic note

© 2010 The American Physical Society 7 pages, 3 figures, submitted to Phys. Rev. Lett., please refer this paper together with arXiv:1005.2757 [hep-ex] (2010) (submitted to Phys. Rev. D)