CMS: Cosmic muons in simulation and measured data

A dedicated cosmic muon Monte-Carlo event generator CMSCGEN has been developed for the CMS experiment. The simulation relies on parameterisations of the muon energy and the incidence angle, based on measured and simulated data of the cosmic muon flux. The geometry and material density of the CMS infrastructure underground and surrounding geological layers are also taken into account. The event generator is integrated into the CMS detector simulation chain of the existing software framework. Cosmic muons can be generated on earth's surface as well as for the detector located 90 m underground. Many million cosmic muon events have been generated and compared to measured data, taken with the CMS detector at its nominal magnetic field of 3.8 T.Comment: 3 pages, 1 figure. Proceedings of HCP 0

Photon plus Jet Cross Sections at the Tevatron

Photon plus jet production has been studied by the D0 and CDF experiments in Run II of the Fermilab Tevatron Collider at a center of mass energy of sqrt{s}=1.96 TeV. Measurements of the inclusive photon plus jet, di-photon and photon plus b jet cross section are presented. They are based on integrated luminosities between 0.2 fb^-1 and 1.1 fb^-1. The results are compared to perturbative QCD calculations in various approximations.Comment: 4 pages, 4 figures, XLIII Rencontres de Moriond, QCD and High Energy Interactions, 200

Measurement of the charge ratio of atmospheric muons with the CMS detector

A measurement is presented of the flux ratio of positive and negative muons from cosmic ray interactions in the atmosphere, using data collected by the CMS detector at ground level and in the underground experimental cavern. The excellent performance of the CMS detector allowed detection of muons in the momentum range from 5GeV/c to 1TeV/c. For muon momenta below 100GeV/c the flux ratio is measured to be a constant 1.2766 +/-0.0032(stat.) +/-0.0032(syst.), the most precise measurement to date. At higher momenta an increase in the charge ratio is observed, in agreement with models of muon production in cosmic ray showers and compatible with previous measurements by deep underground experiments.Comment: 2 pages, 1 figure, ICHEP 2010 conference proceeding

Recent results of the CMS experiment

The CMS experiment is a multi-purpose detector successfully operated at the LHC where predominantly pp collisions take place at various centre-of-mass energies up to sqrt(s)=8 TeV so far. Several weeks per year also heavy-ion collisions take place leading to interesting studies in Pb-Pb and p-Pb collisions at sqrt(s_(NN))=2.76 TeV and sqrt(s_(NN))=5.02 TeV centre-of-mass energies per nucleon, respectively. The excellent performance of the accelerator and the experiment allows for dedicated physics measurements over a wide range of subjects, starting from particle identification, encompassing forward physics, Standard Model measurements in multijet, boson, heavy flavour and top quark physics, building the basis for new physics searches interpreted within the framework of various models and theories. These pursued pp physics subjects are complemented by a rich heavy ion physics programme.Comment: 20 pages, 10 figures, 1 table, proceedings of 52. International Winter Meeting on Nuclear Physics, Bormio 201

Drift velocity and pressure monitoring of the CMS muon drift chambers

The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore, the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented. Another important parameter to be monitored is the pressure inside the muon drift tube chambers. The differential pressure must not exceed a certain value and the absolute pressure has to be kept slightly above ambient pressure to prevent air from entering into the muon drift tube chambers in case of a leak. Latest drift velocity monitoring results are discussed.Comment: 3 pages, 2 figures. Proceedings of Lepton Photon 200