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Description
The TOTEM experiment at the interaction point 5 of the LHC has measured the total, elastic and inelastic proton-proton cross sections in a centre-of-mass energy range from 2.76 to 13 TeV, in dedicated fills with special beam optics.
Most recently, TOTEM has performed the first measurement of the ρ parameter at $\sqrt{s} = 13$ TeV, where rho is the ratio between the real and the imaginary part of the nuclear elastic scattering amplitude at t = 0.
The unprecedented precision of the measurement, combined with the TOTEM total cross-section measurements, led to the exclusion of all the models classified and published by COMPETE. The ρ and σtot results obtained by TOTEM are compatible with predictions -- from alternative theoretical models both in the Regge-like framework and in the modern QCD framework -- of a colourless 3-gluon bound state exchange in the t-channel of the proton-proton elastic scattering.