DOI: 10.17182/hepdata.73997.v1/t5
title: "Table 5" of "Measurement of the total cross section from elastic scattering in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector"

description: The measured differential elastic cross section. In addition to the statistical and total systematic uncertainties, the following 22 systematic shifts 
are given, which are included in the profile fit with their signs:
-- Constraints: Beam optics uncertainty obtained by varying the ALFA constraints in the optics fit
-- QScan: Variation by +/- 0.1 % of the quadrupole strength
-- Q2: Fit of the strength of Q2 using the best value for the strength of Q1 and Q3
-- Q5Q6: Variation of the strength of Q5 and Q6 by -0.2% as indicated by machine constraints
-- MadX: Uncertainty related to the beam transport replacing matrix transport by MadX PTC tracking
-- Qmisal: Uncertainty due to the mis-alignment of the quadrupoles in the beam line
-- Q1Q3: Propagation of the optics fit uncertainty in the strenght of Q1 and Q3 on the differential elastic cross section
-- Aopt: Alignment uncertainty from the optimization procedure
-- Offv: Alignment uncertainty related to the vertical beam center offset 
-- Offh: Alignment uncertainty related to the horizontal beam center offset 
-- Ang: Alignment uncertainty related to the detector rotation in the x-y plane
-- BGn: Uncertainty from the background normalization
-- BGs: Uncertainty from the background shape
-- MCres: Error from modelling of the detector response
-- Slope: Residual dependence on the physics model estimated by varying the nuclear slope in the simulation by +/- 1 GeV^-2
-- Emit: Uncertainty from the emittance used to calculate beam divergence in the simulation
-- Unf: Unfolding uncertainty from the data-driven closure test
-- Trac: Uncertainty from the variation of the track reconstruction selection cuts
-- Xing: Uncertainty from residual crossing angle in the horizontal plane
-- Eff: Uncertainty from the reconstruction efficiency
-- Lumi: Luminosity uncertainty (+/- 1.5%)
-- Ebeam: Uncertainty from the nominal beam energy (+/- 0.65%)
Small differences in the values given here compared to the published version 
are related to insignificant rounding issues.
description: CERN-LHC. A measurement of the total $pp$ cross section at the LHC at $\sqrt{s}=8$ TeV is presented. 
An integrated luminosity of $500$ $\mu$b$^{-1}$ was accumulated 
in a special run with high-$\beta^{\star}$ beam optics 
to measure the differential elastic cross section as a function of 
the Mandelstam momentum transfer variable $t$. The measurement is performed with the ALFA sub-detector of 
ATLAS. Using a fit to the differential elastic cross section in the $-t$ range from $0.014$ GeV$^2$ to $0.1$ GeV$^2$ to 
extrapolate $t\rightarrow 0$, the total cross section, $\sigma_{\mathrm{tot}}(pp\rightarrow X)$, 
is measured via the optical theorem to be:
$\sigma_{\mathrm{tot}}(pp\rightarrow X) = \mbox{96.07} \; \pm 0.18 \; ({\mbox{stat.}}) \pm 0.85 \; 
({\mbox{exp.}}) \pm 0.31 \; (\mbox{extr.}) \; \mbox{mb} \;,$
where the first error is statistical, the second accounts for all experimental systematic uncertainties and the last 
is related to uncertainties in the extrapolation $t\rightarrow 0$. 
In addition, the slope of the exponential function describing the elastic cross section at small $t$ is determined to be $B = 19.74 \pm 0.05 \; ({\mbox{stat.}}) \pm 0.23 \; ({\mbox{syst.}}) \; \mbox{GeV}^{-2}$.