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

The TOTEM collaboration has measured the elastic proton-proton differential cross section dσ/dt at √s = 13 TeV LHC energy using dedicated beta∗ = 90 m beam optics. The Roman Pot detectors were inserted to 10σ 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 ± 0.002 stat ± 0.01 syst ) GeV**−2 in the |t |-range 0.04 GeV**2 to 0.2 GeV**2. The dip position is |tdip| = (0.47 ± 0.004 stat ± 0.01 syst) GeV**2. The differential cross section ratio at the bump vs. at the dip R = 1.77 ± 0.01stat 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.