High-mass dijet cross sections in photoproduction at HERA

TL;DR

This paper measures dijet cross sections in photoproduction at HERA, compares results with QCD predictions, and sets limits on Z0 and new heavy resonance production in the dijet mass range.

Contribution

It provides detailed measurements of dijet cross sections and angular distributions, and establishes upper limits on Z0 and other heavy resonance production in photoproduction.

Findings

Measured dijet cross sections for 47 < Mjj < 160 GeV.

Compared measurements with next-to-leading-order QCD calculations.

Set 95% C.L. upper limit on Z0 photoproduction cross section.

Abstract

Dijet differential cross sections for the reaction e+p -> e+ + jet + jet + X in the photoproduction regime have been measured with the ZEUS detector at HERA using an integrated luminosity of 42.7 pb**{-1}. The cross sections are given for photon-proton centre-of-mass energies in the range 134< W <277 GeV. The differential cross sections as a function of the dijet mass, Mjj, and of the dijet angular variables have been measured for 47 < Mjj < 160 GeV and compared to next-to-leading-order QCD calculations. The dijet events in the region 75< Mjj < 100 GeV have been used to derive a 95% C.L. upper limit on the cross section for Z0 photoproduction of sigma(e+ p -> e+ Z0 X} < 5.9 pb. Upper limits on the photoproduction of new heavy resonances decaying into two jets are also presented for masses in the range between 60 GeV and 155 GeV.