Elastic and Total Cross-Section Measurements by TOTEM

The proton-proton elastic differential cross section ${\rm d}\sigma/{\rm d}t$ has been measured by the TOTEM experiment at $\sqrt{s}=2.76$~TeV energy with $\beta^{*}=11$~m beam optics. TheRoman Pots were inserted to 13 times the transverse beam size from the beam, which allowed to measure the differential cross-section of elastic scattering in a range of the squared four-momentum transfer ($|t|$) from $0.36$~GeV$^{2}$ to $0.74$~GeV$^{2}$. The differential cross-section can be described with an exponentialin the $|t|$-range between $0.36$~GeV$^{2}$ and $0.54$~GeV$^{2}$, followed by a diffractive minimum (dip) at $|t_{\rm dip}|=(0.61\pm0.03)$~GeV$^{2}$ and a subsequent maximum (bump). The ratio of the ${\rm d}\sigma/{\rm d}t$ at the bumpand at the dip is $1.7\pm0.2$. When compared to the proton-antiproton measurement of the D0 experiment at $\sqrt s = 1.96$~TeV, a significant difference can be observed. Under the conditionthat the effects due to the energy difference between TOTEM and D0 can be neglected, the result provides evidence for the exchange of a colourless C-odd three-gluon compound state in the $t$-channel of the proton-proton elastic scattering.