GRANIITTI: A Monte Carlo Event Generator for High Energy Diffraction

Abstract

We describe the physics and computational power of Graniitti Monte Carlo event generator, a new fully multithreaded engine designed for high energy diffraction, written in modern C++. The emphasis is especially on the lowmass domain of central exclusive processes of the S-matrix, where exotic QCD phenomena such as glueballs are expected and holographic dualities with gravity may be tested. The generator includes photon-photon, photon-pomeron, pomeron-pomeron, Durham QCD model and Tensor pomeron model type scattering amplitudes and advanced spin analysis tools. The generator combines a full parametric resonance spectrum with continuum interference and forward + central spin correlations together with event-by-event eikonal screening loop and forward proton excitation kinematics. We demonstrate the state-of-the-art capabilities and show how the enigmatic 'glueball filter' observable is driven by spin polarization.

Multiparticle Production and Initial Quasitemperature from Proton-Induced Carbon Collisions at pLab=31 GeV/c

“…In particular, for leading protons with momenta being (0.5-0.98)p Lab , a large fraction (77%) comes from non-diffractive deep-inelastic scatterings. In proton-proton and proton-nucleus collisions at the considered energy of this paper, the fraction of diffractive process is about 20% [52] in inelastic events, which is only a half of the fraction of leading protons. Even in nucleus-nucleus collisions, the effect of leading protons in forward rapidity region is also obvious [42,53,54,55], which also reflects in high momentum region and is not only from diffractive process.…”

Study of the central exclusive production of $\pi^+\pi^-$, $K^+K^-$ and $p \bar{p}$ pairs in proton-proton collisions at $\sqrt{s} = 510$ GeV with the STAR detector at RHIC

“…Shown error bars represent the statistical uncertainties. The results are compared with a new tune of GRANIITTI, a Monte Carlo event generator for high energy diffraction [4]. GRANIITTI calculates invariant mass spectra assuming continuum and resonance contributions.…”