# Elastic differential cross-section measurement at $\sqrt{s}=13$ TeV by TOTEM

## TL;DR

The TOTEM experiment measured the elastic proton-proton differential cross section at 13 TeV, revealing detailed features like the dip and bump, with high precision, enhancing understanding of proton interactions at TeV energies.

## Contribution

This work provides the first high-precision measurement of the differential cross section at 13 TeV, including the dip and bump features, using dedicated beam optics and extensive data collection.

## Key findings

- Measured the differential cross section over a wide |t| range.
- Identified the position of the diffractive dip at 0.47 GeV^2.
- Determined the ratio of cross sections at bump and dip as 1.77.

## Abstract

The TOTEM collaboration has measured the elastic proton-proton differential cross section ${\rm d}\sigma/{\rm d}t$ at $\sqrt{s}=13$ TeV LHC energy using dedicated $\beta^{*}=90$ m beam optics. The Roman Pot detectors were inserted to 10$\sigma$ distance from the LHC beam, which allowed the measurement of the range $[0.04$ GeV$^{2}$$; 4 $GeV$^{2}$$]$ in four-momentum transfer squared $|t|$. The efficient data acquisition allowed to collect about 10$^{9}$ elastic events to precisely measure the differential cross-section including the diffractive minimum (dip), the subsequent maximum (bump) and the large-$|t|$ tail. The average nuclear slope has been found to be $B=(20.40 \pm 0.002^{\rm stat} \pm 0.01^{\rm syst})~$GeV$^{-2}$ in the $|t|$-range $0.04~$GeV$^{2}$ to $0.2~$GeV$^{2}$. The dip position is $|t_{\rm dip}|=(0.47 \pm 0.004^{\rm stat} \pm 0.01^{\rm syst})~$GeV$^{2}$. The differential cross section ratio at the bump vs. at the dip $R=1.77\pm0.01^{\rm stat}$ has been measured with high precision. The series of TOTEM elastic pp measurements show that the dip is a permanent feature of the pp differential cross-section at the TeV scale.