Efficient calculation of exclusive diffractive cross sections at the EIC and LHeC with the Sartre event generator

Tobias Toll; Dipan Ghosh; Abhinav Srivastav

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arXiv · 2606.14633

Efficient calculation of exclusive diffractive cross sections at the EIC and LHeC with the Sartre event generator

Tobias Toll·Dipan Ghosh·Abhinav Srivastav

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Abstract

We present a new version of the Sartre event generator for exclusive diffraction at small xP in the colour dipole model, for $ep$ and $e$A scattering at the EIC and the LHeC as well as ultra-peripheral $pp$, $p$A, and AA collisions at RHIC and the LHC. Sartre stores the first and second moment of the interaction amplitudes in lookup tables which are then used for efficient event generation. There are many possible combinations of processes in Sartre, with different initial state nuclear targets and different final state vector mesons or real photons. We also want to implement different versions of the dipole model: with and without non-linear saturation effects, with and without nucleon hotspot substructure. A long-standing bottleneck for simulating all possible exclusive processes has been the production of lookup tables, which take a few CPU-year for each combination, necessitating the use of computing farms. The calculation also involves integrations of rapidly fluctuating integrands, which may cause numerical glitches which takes much effort to smoothen out. In this paper we present a solution to these issues, by presenting a new numerical calculation which improves the efficiency in the table production by 3-4 orders of magnitudes. This enables us to produce lookup tables for any process that we may be interested in, in a few hours. The new calculation does also not exhibit numerical glitches. We provide novel predictions for the EIC and the LHeC using the new version of Sartre.

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Tobias Toll, Dipan Ghosh, Abhinav Srivastav. 2026-06-12. Efficient calculation of exclusive diffractive cross sections at the EIC and LHeC with the Sartre event generator. https://arxiv.org/abs/2606.14633

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