Table 3.

Length-scale calibrations at the ATLAS interaction point at $\sqrt{s}=8$ TeV. Values shown are the ratio of the beam displacement measured by ATLAS using the average primary-vertex position, to the nominal displacement entered into the accelerator control system. Ratios are shown for each individual beam in both planes, as well as for the beam-separation scale that determines that of the convolved beam sizes in the vdM scan. The uncertainties are statistical only

Calibration session(s)	April 2012		July 2012 (applicable to November)
${\mathit{\beta }}^{\star }$	0.6 m		11 m
	Horizontal	Vertical	Horizontal	Vertical
Displacement scale
Beam 1	$0.9882\pm 0.0008$	$0.9881\pm 0.0008$	$0.9970\pm 0.0004$	$0.9961\pm 0.0006$
Beam 2	$0.9822\pm 0.0008$	$0.9897\pm 0.0009$	$0.9964\pm 0.0004$	$0.9951\pm 0.0004$
Separation scale	$0.9852\pm 0.0006$	$0.9889\pm 0.0006$	$0.9967\pm 0.0003$	$0.9956\pm 0.0004$