# Background check for anomalous like-sign dimuon charge asymmetry - High Energy Physics - Phenomenology

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Abstract: The D0 Collaboration has reported an excess of roughly one percent of $\mu^-\mu^-$ pairs over $\mu^+ \mu^+$ pairs in $\bar p p$ collisions at acenter-of-mass energy $\sqrt{s} = 1.96$ GeV at the Fermilab Tevatron, whenknown backgrounds are subtracted. This excess, if ascribed to CP violation inmeson-antimeson mixing of non-strange or strange neutral $B$ mesons, is about40 times that expected in the Standard Model SM. We propose a null test,based on a tight restriction on the muon impact parameter $b$, to confirm thatthis excess is indeed due to $B$ mesons. If the asymmetry is due to anomalousCP violation in $B s$-$\bar B s$ mixing then a tight restriction on $b$ wouldincrease by a factor two the net asymmetry from neutral $B$ mixing, while thesample of dimuons from neutral $B$ decays will be reduced significantlyrelative to background events.

Autor: Michael Gronau, Jonathan L. Rosner

Fuente: https://arxiv.org/