Abstract
The collimation of average multiplicity inside quark and gluon jets is investigated in perturbative QCD in the modified leading logarithmic approximation (MLLA). The role of higher order corrections accounting for energy conservation and the running of the coupling constant leads to smaller multiplicity collimation as compared to leading logarithmic approximation (LLA) results. The collimation of jets produced in heavy-ion collisions has also been explored by using medium-modified splitting functions enhanced in the infrared sector. As compared to elementary collisions, the angular distribution of the jet multiplicity is found to broaden in QCD media at all energy scales.
Highlights
The “jet quenching” phenomenon observed at RHIC precedes by many years the first measurements of jets in heavy-ion collisions
We investigate in this paper the collimation of the average multiplicity inside a quark and a gluon jet as a function of the jet energy scale
In the leading logarithmic approximation (LLA) [15], the solid angle Θ1/2 containing half of the average multiplicity of the jet Θ0 decreases with the jet hardness Q ≃ EΘ0 approximately like Θ1/2(Q) ∼ N −1/4(Q), such that at high energy scales the bulk of the total multiplicity is concentrated at smaller solid angles around the culation to direction of propagation of the the modified leading logarithmic approximation (MLLA) by incorporating all jet
Summary
The “jet quenching” phenomenon observed at RHIC precedes by many years the first measurements of jets in heavy-ion collisions. The modified leading logarithmic approximation (MLLA) in perturbative QCD has been successfully tested from e+e− to hadronic collisions 1 [14] To this sake, we investigate in this paper the collimation of the average multiplicity inside a quark and a gluon jet as a function of the jet energy scale. In the leading logarithmic approximation (LLA) [15], the solid angle Θ1/2 containing half of the average multiplicity of the jet Θ0 decreases with the jet hardness Q ≃ EΘ0 approximately like Θ1/2(Q) ∼ N −1/4(Q), such that at high energy scales the bulk of the total multiplicity is concentrated at smaller solid angles around the culation to direction of propagation of the the MLLA by incorporating all jet In this corrections poafpoerr,dewreOext√enαds this cal, which partially guarantee energy conservation and account for the running of the coupling constant αs in intra-jet cascades.
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