Forward Physics at the LHC; Elastic Scattering

Understand

The following effects in the nearly forward ("soft") region of the LHC are proposed to be investigated: 1) At small |t| the fine structure of the cone (Pomeron) shouldbe scrutinized: a) a break of the cone near $t\approx - 0.1 ~ GeV$^2, due to the two-pion threshold, and required by t-channel unitarity, is expected, and b) possible small-period oscillations between $t=0$ and the dip region.

• 2) In measuring the elastic $pp$ scattering and total $pp$ cross section at the LHC, the experimentalists are urged to treat the total cross section $\sigma_t,$ the ratio $\rho$, the forward slope $B$ and the luminosity ${\cal L}$ as free arameters, and to publish model-independent results on ${dN/{dt}}.$ 3) Of extreme interest are the details of the expected diffraction minimum in the differential cross section.
• Its position, expected in the interval $0.4<-t<1$ GeV$^2$ at the level of about $10^{-2} {\rm mb} \cdot$ GeV$^{-2}\div 10^{-1} {\rm mb}\cdot$ GeV$^{-2}$, cannot be predicted unambiguously, and its depth, i.e.
• the ratio of $d\sigma/dt$ at the minimum to that at the subsequent maximum (about $-t=5 $GeV$^2$, which is about 5 is of great importance.