Christopher Seez

This work summarizes the studies for the Higgs boson searches in CMS at the LHC collider. The main discovery channels are presented and the potential is given for the discovery of the SM Higgs boson and the Higgs bosons of the MSSM. The phenomenology, detector, trigger and reconstruction issues are briefly discussed.

This note describes the reconstruction of electrons using the electromagnetic calorimeter (ECAL) alone. This represents the first step in the High Level Trigger reconstruction and selection chain. By making super-clusters (i.e. clusters of clusters) much of the energy radiated by bremsstrahlung in the tracker material can be recovered. Representative performance figures for energy and position resolution in the barrel are given.

The ratio R, defined as the fractional decrease in the beam signal divided by the fractional decrease in the light monitoring signal, was measured at the GIF-X5 facility for a set of 20 ECAL barrel crystals. The dependence of R on the wavelength of the injected monitoring light and its path length in the crystals was studied. Measurements of the inter-crystal variation in R are presented for 10 pre-production crystals. Results on the dependence of signal loss on the irradiation profile are given. The use of lead filters, placed between a 137Cs source and a crystal, to reproduce different longitudinal irradiation profiles has been tested.

The momentum and angular distributions of punchthrough muons have been measured after a 10 λ calorimeter using an iron toroid magnet with 1.5 T as spectrometer. The calorimeter was inside a variable magnetic field of 0 to 3 T. The incident momentum of the π− beam ranged from 20 to 300 GeV/c. Measurements were also done at some beam momenta for π+, K+ and p. The results are compared with Monte Carlo predictions. A parameterization for the momentum spectrum of punchthrough muons was derived from the data.

A sample of events with large missing transverse energy, taken in the UA 1 detector and representing an integrated luminosity of 715 nb−1, is used to set limits on the masses of squarks and gluinos. We find mq̃ > 45 GeV/c2 at 90% CL, independent of the gluino mass, and mg̃> 53 GeV/c2 independent of squark mass, provided that the gluino is not long-lived. If mq̃ = mg̃ = m we find m > 75 GeV/c2.