Study of jet production in H1 detector at HERA. Application to αs(Q2) determination

Measuring the fractions of events with a given number of hadronic jets should enable the HERA physicists to observe the evolution of αs as a function of Q2, hence to measure ΛQCD. For that purpose, after a study of the calorimeter performances, we have developed a jet-finding algorithm, optimized so that it excludes the remnants of the proton from the jet making process. With this algorithm, the ratio of the number of events with two reconstructed jets over the number of events with one reconstructed jet has been studied. A clear dependence with ΛQCD and Q2 is observed. We have then defined a kinematic zone in which the acceptance corrections are below a few percent and the reconstruction of the kinematic variables well under control: 0.01 ≤ x ≤ 0.1; 200 GeV2 ≤ Q2 ≤ 9840 GeV2. Using an integrated luminosity of 100 pb-1, we find that, in this zone, it will be possible to measure ΛQCD with a statistical error of the order of 3%. Moreover, with the same luminosity and points in the (x,Q2) plane defined with a precision of 10%, one should observe the evolution of αs with a statistical precision δαs of the order of 0.03