Table 1.

Observed numbers of opposite-sign $e\mathit{\mu }$ events with one and two $b$-tagged jets ($N_1$ and $N_2$) for each data sample, together with the estimates of backgrounds and associated total uncertainties described in Sect. 6

Event counts	$\sqrt{s}=7\mathrm{TeV}$		$\sqrt{s}=8\mathrm{TeV}$
	$N_1$	$N_2$	$N_1$	$N_2$
Data	3527	2073	21666	11739
$Wt$ single top	$326\pm 36$	$53\pm 14$	$2050\pm 210$	$360\pm 120$
Dibosons	$19\pm 5$	$0.5\pm 0.1$	$120\pm 30$	$3\pm 1$
$Z(\to \mathit{\tau }\mathit{\tau }\to e\mathit{\mu })$+jets	$28\pm 2$	$1.8\pm 0.5$	$210\pm 5$	$7\pm 1$
Misidentified leptons	$27\pm 13$	$15\pm 8$	$210\pm 66$	$95\pm 29$
Total background	$400\pm 40$	$70\pm 16$	$2590\pm 230$	$460\pm 130$