DISASTER++ (Version 1.0)

TL;DR

DISASTER++ presents a C++ class library for calculating (1+1)- and (2+1)-jet observables in deeply inelastic scattering at NLO using the subtraction formalism, with explicit dependence on $N_f$ and on renormalization/factorization scales. It provides a general, observable-agnostic framework, interfaced to FORTRAN, and leverages VEGAS for adaptive Monte Carlo integration to enable multiple observables to be evaluated in a single run. In comparisons with DISENT and MEPJET, DISASTER++ shows good agreement with DISENT but exhibits several discrepancies with MEPJET that depend on internal cuts and PDF choices, underscoring the sensitivity of higher-order QCD calculations to technical details. The work constitutes a flexible, extensible tool for precise jet-related predictions in DIS and lays groundwork for broader one-particle-inclusive extensions and scale-study capabilities, with future directions for cross-checks and interface refinements.

Abstract

DISASTER++ is a C++ class library for the calculation of (1+1) and (2+1)-jet-like quantities in deeply inelastic lepton-nucleon scattering for one-photon exchange in next-to-leading-order QCD perturbation theory. The calculation is based on the subtraction formalism. The user has access to an event record such that an arbitrary set of infrared-safe observables can be calculated in a single run. Compared to other existing universal programs, the full dependence on the number of flavours and on the renormalization and factorization scales is made explicit. An interface class providing a simple interface from C++ to existing FORTRAN programs is available. In a preliminary study DISASTER++ is compared to two other programs for various bins of the lepton variables $x_B$ and $y$, where a particular emphasis is put on different behaviours for $ξ\to 1$ of the parton densities $f(ξ)$. We find good agreement of DISASTER++ and DISENT (Version 0.1). The comparison of DISASTER++ and MEPJET (Version 2.0) leads to several discrepancies.