Combining Parton Showers with Next-to-Leading Order QCD Matrix Elements in Deep-Inelastic eP Scattering

TL;DR

The paper tackles merging fixed-order NLO QCD calculations with parton-shower generators for deep-inelastic eP scattering, focusing on single-jet inclusive cross sections and jet shapes. It introduces a positive-weight NLO-PS matching method that uses a phase-space separation with $R_{tech}$ and a $s_{ m min}^{\mathrm{nlo}}$ cutoff to maintain NLO accuracy while avoiding negative weights. Implemented in DISENT and interfaced with PYTHIA, the approach yields inclusive jet spectra and jet shapes that agree well with ZEUS measurements at HERA, and it improves jet-shape predictions over standard NLO. The work lays the groundwork for a full event generator by planning inclusion of initial-state radiation, hadronization, and extension to dijet final states.

Abstract

We have implemented a systematic procedure for combining parton shower algorithms with next-to-leading order QCD calculations for the case of jet production in deep-inelastic electron-proton scattering. Using this method we have computed inclusive jet cross sections and jet shapes for the case of single-jet production and compared them to data from the ZEUS collaboration at HERA. We found good agreement between the data and our calculations, both for the jet shapes and the inclusive spectra.

Figures (4)

• Figure 1: Differential cross sections $d\sigma/dE_T$ for inclusive jet production in NC DIS events integrated over $-1<\eta<2$ for $Q^2>125,500,1000$ and $2000$ GeV$^2$. The ZEUS data are compared to our calculation labeled ' DISSET' (full line) and to a NLO calculation, labeled 'standard DISENT' (dashed line).
• Figure 2: Differential cross sections $d\sigma/d\eta$ for inclusive jet production in NC DIS events integrated over $E_T>14$ GeV and $Q^2>125$ GeV$^2$. The ZEUS data are compared to our calculation (full line) and to a NLO calculation (dashed line).
• Figure 3: Integrated jet shape $\Psi(r)$ in NC DIS events integrated over $Q^2 > 100$ GeV$^2$ for jets with $E_T>14$ GeV and $-1<\eta<2$. The ZEUS data are compared to our calculation (full line) and to a NLO calculation (dashed line).
• Figure 4: Integrated jet shape $\rho(r)$ in NC DIS events integrated over $Q^2 > 100$ GeV$^2$ for jets with $-1<\eta<2$ in four different ranges of $E_T$. The ZEUS data are compared to our calculation (full line) and to a NLO calculation (dashed line).