The underlying event in proton-proton collisions at 900 GeV from CMS
Faculty of Sciences. Physics
Nuclear physics: B: proceedings supplements. - Amsterdam
15th High Energy Physics International Conference on Quantum, Chromodynamics, JUN 28-JUL 02, 2010, Montpellier, FRANCE
, p. 37-40
It is presented a measurement of the underlying activity in scattering processes with p(T) scale in the GeV region performed in proton-proton collisions at root s = 0.9 TeV, using data collected by the CMS experiment at the LHC. Charged particles production is studied with reference to the direction of a leading object, either a charged particle or a set of charged particles forming a jet. Predictions of several QCD-inspired models as implemented in PYTHIA are compared, after full detector simulation, to the data. The models generally predict too little production of charged particles with pseudorapidity vertical bar eta vertical bar < 2, transverse momentum p(T) > 0.5 GeV/c and azimuthal direction transverse to that of the leading object.