Speaker
Description
Elastic scattering is usually described by the $t$-channel exchange of a $C$-even state (the “Pomeron”) that contributes equally to the $pp$ and $p\bar{p}$ cross sections. QCD also predicts the exchange of a sub-dominant $C$-odd state (the “Odderon”) that has opposite sign in the $pp$ and $p\bar{p}$ amplitudes and that QCD describes as a three-gluon state at leading order. At TeV energies where other exchanges than gluonic are expected to be negligible, a difference between the $pp$ and $p\bar{p}$ elastic differential cross sections ($d\sigma_{el}/dt$) would give evidence for $C$-odd three-gluon exchange.
The $pp$ elastic cross sections at 2.76, 7, 8 and 13 TeV measured by TOTEM at the LHC have characteristic diffractive minima (“dips”) and second maxima (“bumps”), whereas the $p\bar{p}$ cross section at 1.96 TeV measured by D0 at the Tevatron has no dip. We have performed an extrapolation of the $pp$ $d\sigma_{el}/dt$ from TOTEM to 1.96 TeV and compared it with the D0 data to search for the presence of $C$-odd three-gluon exchange.
