Unitarisation dependence of diffractive scattering in light of high-energy collider data

We study the consequences of high-energy collider data on the best fits to total, elastic, inelastic, and single-diffractive cross sections for pp and $$ p\overline{p} $$ p p ¯ scattering using different unitarisation schemes. We find that the data are well fitted both by eikonal and U-matrix schemes, but that diffractive data prefer the U-matrix. Both schemes may be generalised by means of an additional parameter; however, this yields only marginal improvements to the fits. We provide estimates for ρ, the ratio of the real part to the imaginary part of the elastic amplitude, for the different fits. We comment on the effect of the different schemes on present and future cosmic ray data.

Exclusive heavy vector meson electroproduction to NLO in collinear factorisation

We compute the exclusive electroproduction, γ*p → Vp, of heavy quarkonia V to NLO in the collinear factorisation scheme, which has been formally proven for this process. The inclusion of an off-shell virtuality Q2 carried by the photon extends the photoproduction phase space of the exclusive heavy quarkonia observable to electroproduction kinematics. This process is relevant for diffractive scattering at HERA and the upcoming EIC, as well as at the proposed LHeC and FCC.

Roy Glauber and asymptotic diffraction theory

This is a review of Glauber’s asymptotic diffraction theory, in which diffractive scattering is described in terms of interference between semiclassical amplitudes, resulting from a stationary-phase approximation. Typically two such amplitudes are sufficient to accurately describe elastic scattering, but the stationary points are located at complex values of the impact parameter. Their separation controls the interference pattern, and their offsets from the real axis determine the overall fall-off with momentum transfer. Asymptotically, at large momentum transfers, the stationary points move towards singularities of the profile function. I also include some reminiscences from our collaboration.

High-Beta Optics and Running Prospects

Dedicated high-beta optics are used to make forward proton scattering measurements possible at the LHC. Following a short general introduction and history of special high-beta optics and running conditions, we describe the two types of special high-beta runs planned for 2018. A run at top energy at β y * = 90 m for elastic and diffractive scattering, and a low energy run to measure the rho-parameter in the Coulomb interference region.