First measurement of elastic, inelastic and total cross-section, determination of the $ρ$ parameter at $\sqrt{s} =$ 13 TeV by TOTEM and an evidence for odderon

The TOTEM experiment has performed the first 13 TeV measurements of the total crosssection and the ρ parameter, i.e. the real-to-imaginary ratio of the nuclear elastic scattering amplitude at $t =$ 0. The obtained $ρ$ value is significantly lower than expected and together with the total cross-section the new TOTEM measurements rule out most of the pre-LHC models and indicate a strong role of a crossing-odd scattering amplitude even at high energies. A similar conclusion is made from comparison of proton-proton and proton-antiproton elastic differential cross-section in the dip region. Theory offers several candidates for the crossingodd scattering amplitude. In particular, in perturbative QCD it could be realised as $t$-channel exchange of a colourless bound state of 3 gluons.