Inclusive jet production in two-photon collisions at LEP

Abstract

Inclusive jet production, e + e − → e + e − jet X, is studied using 560 pb −1 of data collected at LEP with the L3 detector at centre-of-mass energies between 189 and 209 GeV. The inclusive differential cross section is measured using a k t jet algorithm as a function of the jet transverse momentum, p t , in the range 3 < p t < 50 GeV for a pseudorapidity, η, in the range −1 < η < 1. This cross section is well represented by a power law. For high p t , the measured cross section is significantly higher than the NLO QCD predictions, as already observed for inclusive π ± and π 0 production.

Inclusive jet production in photon–photon collisions at see from 189 to 209 GeV

“…While the L3 data points are compatible with the present measurement, they lie below the OPAL data points at low p jet T and above the OPAL data points at high p jet T , and there is a discrepancy in shape between the L3 data and the NLO calculation. This difference in shape has been reported in the L3 publication and leads to a significant disagreement between the L3 data and the NLO calculation at the highest p jet T of up to 50 GeV studied in [5]. The present analysis finds the region of p jet T > 40 GeV to be dominated by background and hence no measurement is presented for this region.…”

“…Inclusive jet cross-sections in two-photon interactions have previously been measured at √ s ee from 130 to 136 GeV by OPAL [4], and at √ s ee from 189 to 209 GeV by L3 [5]. In [5] an excess at high transverse momenta was observed in the data over the QCD calculations, for kinematical conditions very similar to those used in the present Letter. At LEP the photons are radiated by the beam electrons, 28 and carry mostly small negative four-momenta squared, Q 2 .…”

Inclusive production of charged hadrons in photon–photon collisions

“…Furthermore a drastic discrepancy between data and NLO QCD has recently been observed in this process [1] which would indicate the breakdown of this otherwise so successful theory and hence requires further study. Our measurements complement similar studies of jet production [2,3]. The same partonic processes are at work in QCD in both cases, but hadronisation is usually treated differently.…”

High Momentum Hadron and Jet Production in Photon-Photon Collisions at LEP2

“…To facilitate a comparison with a recent measurement by the L3 collaboration [11], the inclusive jet cross section measurement was performed with kinematic conditions such as the ones used in the L3 analysis. Figure 2 shows the resulting inclusive jet differential cross section.…”

“…been reported in the L3 publication and leads to a significant disagreement between the L3 measurement and the NLO calculation at the highest p jet T of up to 50 GeV studied in [11]. The OPAL analysis [2] finds the region of p jet T > 40 GeV to be dominated by background and hence no measurement is presented for this region.…”