Goals

We propose an experimental investigation of the interactions of protons at a center of mass energy of = 14 TeV at the Compact Muon Solenoid (CMS) experiment planned for the Large Hadron Collider (LHC) at CERN. In order to study the TeV mass scale, the LHC is designed to operate at a luminosity of cm s. The physics program includes the study of electroweak symmetry breaking, investigating the properties of the top quark, searching for new heavy gauge bosons, probing quark and lepton substructure, looking for supersymmetry and exploring for other new phenomena. Models of electroweak symmetry breaking generally include a scalar field whose interactions give mass to the and bosons, as well as the charged fermions. The dynamical component of this scalar field, the Higgs boson, is expected to decay into and pairs if its mass exceeds 180 GeV. Other theories predict new particle states that decay to , , or pairs. Thus, the study of boson pairs is an important venue for understanding of electroweak symmetry breaking. This requires efficient detection of their decay electrons and muons over a large a solid angle.

Detection of the -quark and measurement of its mass will provide important information about the fermion mass spectrum and the Standard Model. Millions of -quark events are expected per LHC year. This presents an opportunity to make precision measurements of the -quark properties. The decay of top quark pairs to pairs may also represent a significant background to the Higgs boson, and therefore needs careful study. Events with -quarks will be identified by searching for one or two isolated leptons from semileptonic -quark decays. Backgrounds from -multijet production are reduced by identifying the -quark jets (jets with a secondary vertex) in the -quark events.

It is possible that new forces may manifest themselves at LHC energies in the form of massive bosons similar to the and . Heavy charged bosons can be found by looking for events with high-, isolated leptons and large total missing . Another intriguing possibility is that quarks consist of other particles bound by some new force. This would cause scattering of quarks at high energy to differ from the predictions of QCD. An indication of such quark compositeness would be an excess of hadronic jet events at high transverse momenta. Evidence for lepton substructure would be a deviation from the expected Drell-Yan contribution to the lepton pair spectrum.

Supersymmetry proposes a relationship between fermions and bosons that forecasts a host of new particles. An example is the gluino, the supersymmetric partner of the gluon. This particle could decay to at least one stable neutral particle, which is not observed. Therefore, gluino events would be characterized by a large imbalance in the observed total transverse momentum. Other supersymmetric particles which are potentially detectable at the LHC are -inos and -inos, which decay into multilepton final states.