Incoherent diffraction and structure fluctuations at small x

Apr 12, 2016, 11:00 AM
SR4b (DESY Hamburg)


DESY Hamburg

Small-x, Diffraction and Vector Mesons WG5 Small-x and Diffraction


Dr Heikki Mäntysaari (Brookhaven National Laboratory)


Exclusive vector meson production can be used to directly probe the gluon density of a hadron. Measuring the cross section differentially in the momentum transfer t makes it possible to determine the transverse density profile (via coherent diffraction) and density fluctuations (incoherent diffraction) of the target hadron. This knowledge on the geometric fluctuations of the proton is particularly important for understanding collective phenomena observed in proton-nucleus collisions. We calculate coherent and incoherent diffractive vector meson production in photon-proton and photon-nucleus scattering. The dipole model used in the calculation is constrained by the proton structure function data. By implementing sub-nucleon scale fluctuations using the constituent quark model or the IP-glasma framework we demonstrate that incoherent gamma-p scattering is sensitive to small-scale fluctuations. We discuss to what extent the current HERA diffractive deep inelastic scattering data can be used to constrain the proton structure fluctuations and how an Electron Ion Collider (EIC) can improve the picture. Before an EIC, the only processes that can be used to study diffraction with nuclear targets at high energy are ultraperipheral heavy ion collisions. We present an updated CGC calculation where a dipole model constrained by more precise combined HERA structure function data is used, and calculate diffractive cross sections at sqrt(s)=5 TeV. We discuss how access to the ultraperipheral cross section at different energies can help to study the nuclear wave function and its fluctuations.

Primary author

Dr Heikki Mäntysaari (Brookhaven National Laboratory)


Dr Björn Schenke (Brookhaven National Laboratory) Dr Tuomas Lappi (University of Jyväskylä)

Presentation materials