CMS-PAS-FSQ-15-005

CMS-PAS-FSQ-15-005
Measurement of the inelastic proton-proton cross section at $\sqrt{s}=$ 13 TeV
CMS Collaboration
April 2016

Abstract: A measurement of the inelastic cross section for proton-proton collisions at a centre-of-mass energy of $\sqrt{s} =$ 13 TeV is presented. The analysis is performed with the CMS detector based on information from forward calorimetry, at pseudorapidity 3.0 $< \eta <$ 5.2 and --6.6 $< \eta <$ --3.0, and thus covers particle production over more than 11 units of pseudorapidity and down to small transverse momenta. A visible cross section of 66.9 $\pm$ 0.4 (exp) $\pm$ 2.0 (lumi) mb is obtained for $M_\mathrm{X} >$ 4.1 GeV and $M_\mathrm{Y} >$ 13 GeV, where $M_\mathrm{X}$ and $M_\mathrm{Y}$ are the masses of the diffractive dissociation systems moving towards negative and positive pseudorapidity, respectively. The visible cross section is extrapolated to the full inelastic phase space domain, yielding 71.3 $\pm$ 0.5 (exp) $\pm$ 2.1 (lumi) $\pm$ 2.7 (ext) mb. The results are compared with those of other experiments, and with models used to describe high-energy hadronic interactions.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, JHEP 07 (2018) 161. The superseded preliminary plots can be found here.

Figures & Tables	Summary	CMS Publications

Figures
png pdf	Figure 1-a: Fully corrected cross section in various phase space regions, compared to different models (a) and the same cross sections scaled to the cross section obtained for $\xi > 10^{-6}$ (b). The data point for $\sigma _{\rm inel}$ is obtained from a model-dependent extrapolation of the cross section for $\xi _{\rm X} > 10^{-7}$ or $\xi _{\rm Y} > 10^{-6}$ .
png pdf	Figure 1-b: Fully corrected cross section in various phase space regions, compared to different models (a) and the same cross sections scaled to the cross section obtained for $\xi > 10^{-6}$ (b). The data point for $\sigma _{\rm inel}$ is obtained from a model-dependent extrapolation of the cross section for $\xi _{\rm X} > 10^{-7}$ or $\xi _{\rm Y} > 10^{-6}$ .

Tables
png	Table 1: Overview of purity ( $N_{\rm cor}/(N_{\rm ZB} \times F_{\rm ZB})$ ), average pileup ( $\lambda$ ), and fully corrected particle level cross section (with statistical uncertainty) for all runs used in this analysis.
png	Table 2: Overview of systematic uncertainties from various sources.
png	Table 3: Model extrapolation factors from $\xi _{\rm X} > 10^{-7}$ or $\xi _{\rm Y} > 10^{-6}$ to the total inelastic phase space.

Summary

A measurement of the inelastic cross section for proton-proton collisons at

$\sqrt{s} =$ 13 TeV obtained with the CMS detector at the LHC has been presented. A visible cross section of 66.9

$\pm$ 0.4 (exp)

$\pm$ 2.0 (lum) mb is obtained for

$M_{\rm X} >$ 4.1 GeV and

$M_{\rm Y} >$ 13 GeV, where

$M_{\rm X}$ and

$M_{\rm Y}$ are the masses of the diffractive dissociation systems moving towards negative and positive pseudorapidity, respectively. The visible cross section is extrapolated to the full inelastic phase space domain, yielding 71.3

$\pm$ 0.5 (exp)

$\pm$ 2.1 (lum.)

$\pm$ 2.7 (ext) mb. The measured cross section is significanlty lower than predicted by models for hadronic scattering.