Charm quark and D^* cross sections in deeply inelastic scattering at DESY HERA

TL;DR

The paper delivers a next-to-leading order Monte Carlo–style calculation of charm-quark production in deep inelastic scattering at HERA, including predictions for D^*(2010) via Peterson fragmentation. It employs a subtraction-based approach to handle soft and collinear divergences and expresses results through heavy-quark structure functions (F2^c, F_L^c) with explicit mass, scale, and PDF dependence. The authors validate their code by reproducing known LO results with AROMA and matching total NLO cross sections, and they analyze how PDFs, charm mass, and renormalization scales shape differential distributions. The work provides a practical framework for comparing to HERA data and for constraining the small-x gluon content, while highlighting uncertainties from charm mass and hadronization parameters.

Abstract

A next-to-leading order Monte Carlo program for the calculation of heavy quark cross sections in deeply inelastic scattering is described. Concentrating on charm quark and D^*(2010) production at HERA, several distributions are presented and their variation with respect to charm quark mass, parton distribution set, and renormalization-factorization scale is studied.

Figures (8)

• Figure 1: $F_2^c(x,Q^2,m_c=1.5\,{\rm GeV})$ as a function of $x$ for GRV94 (solid lines) and CTEQ4F3 (dash lines) parton distribution sets for $Q^2=3\, {\rm GeV}^2\,$(bottom), $25\, {\rm GeV}^2\,$(middle), and $50\, {\rm GeV}^2\,$(top).
• Figure 2: $F_2^c(x,Q^2,m_c=1.5\,{\rm GeV})$ as a function of the scale $\mu$ with $m_c \leq \mu \leq 2 \sqrt{Q^2+4m_c^2}$ for various $x$ and $Q^2$ values for the GRV94 (solid lines) and CTEQ4F3 (dash lines) parton distribution sets.
• Figure 3: Comparison of leading order results (open circles) with AROMAaroma (solid lines) for charm production in the kinematic region $10<Q^2<100\, {\rm GeV}^2$ and $0<y<0.7$ at HERA.
• Figure 4: Leading (dash) and full next-to-leading (solid) order differential cross sections for charm quark production at $\sqrt{S}=301\, {\rm GeV}$ at HERA using the GRV94 (LO and HO, respectively) parton distribution set at $\mu=\sqrt{Q^2+4m_c^2}$ with $m_c=1.5\, {\rm GeV}$.
• Figure 5: Next-to-leading order differential cross sections for charm quark production at $\sqrt{S}=301\, {\rm GeV}$ at HERA using the GRV94 (dash) and CTEQ4F3 (solid) parton distribution sets at $\mu=\sqrt{Q^2+4m_c^2}$ with $m_c=1.5\, {\rm GeV}$. Also shown for comparison in part $(c)$ is $d\sigma/d\log(\xi)$ vs. $\log(\xi)$ (right pair of curves).