Dijet Production at HERA in Next-to-Leading Order

Abstract

Two-jet cross sections in deep inelastic scattering at HERA are calculated in next-to-leading order. The QCD corrections are implemented in a new $ep\rightarrow n$ jets event generator, MEPJET, which allows to analyze arbitrary jet definition schemes and general cuts in terms of parton 4-momenta. First results are presented for the JADE, the cone and the $k_T$ schemes. For the $W$-scheme, disagreement with previous results and large radiative corrections and recombination scheme dependencies are traced to a common origin.

Figures (5)

• Figure 1: Dependence of the inclusive two-jet cross section in the $k_T$, cone, JADE, and the $W$-scheme on $s_{min}$, the two-parton resolution parameter. Partons are recombined in the $E$-scheme. Error bars represent statistical errors of the Monte Carlo program. For the fairly soft jet definition criteria described in the text, $s_{min}$ independence is achieved for $s_{min}\mathrel{\hbox{$<$} \hbox{$\sim$}} 0.1$ GeV$^2$.
• Figure 2: Dependence of a) the two-jet inclusive and b) the two-jet exclusive cross section in the cone scheme on the renormalization and factorization scale factor $\xi$. The solid curves are for $\mu_R^2=\mu_F^2=\xi\;(\sum_i\;p_T^B(i))^2$, while for the dashed curves only $\xi_R=\xi$ is varied but $\xi_F=1/4$ is fixed. Choosing the photon virtuality as the basic scale yields the dotted curves, which correspond to $\mu_R^2=\mu_F^2=\xi\;Q^2$. Results are shown for the LO (lower curves) and NLO calculations.
• Figure 3: Transverse momentum distribution in the lab frame for the jet with (a) minimal and (b) maximal transverse momentum. Results are shown for the two-jet inclusive cross section in the cone scheme in leading (dashed curves) and next-to-leading order (histograms).
• Figure 4: Rapidity distribution of the most forward jet (a) and transverse momentum distribution of the scattered electron (b) in the lab frame. Results are shown for the $k_T$ scheme in leading (dashed curves) and next-to-leading order (histograms) for the two-jet inclusive cross section.
• Figure 5: Single jet mass effects at next-to-leading order. (a) Fraction of events in the cone scheme (solid curve), $k_T$ scheme (dashed curve), and $W$-scheme (histogram) with all jet mass to energy ratios below $m/E$, where $E$ is the corresponding jet's energy in the parton center of mass frame. Negative values at small $m/E$ are due to virtual contributions at $m/E=0$. (b) Next-to-leading order transverse momentum ($x_T=p_T$, solid histogram) and transverse-energy distribution ($x_T=E_T$, dotted curve) for the jet with largest $p_T$ and $E_T$ in the Breit frame, for the $W$-scheme. The dashed curve shows the leading order result where both distributions are identical.