Mu3e

Abstract:

The results of a search for the pair production of a fourth-generation up-type quark (t') in proton-proton collisions at √s=7 TeV are presented, using data corresponding to an integrated luminosity of about 5.0 fb-1 collected by the Compact Muon Solenoid experiment at the LHC. The t' quark is assumed to decay exclusively to a W boson and a b quark. Events with a single isolated electron or muon, missing transverse momentum, and at least four hadronic jets, of which at least one must be identified as a b jet, are selected. No significant excess of events over standard model expectations is observed. Upper limits for the t't' production cross section at 95% confidence level are set as a function of t' mass, and t'-quark production for masses below 570 GeV is excluded. The search is equally sensitive to nonchiral heavy quarks decaying to Wb. In this case, the results can be interpreted as upper limits on the production cross section times the branching fraction to Wb. © 2012 CERN.

Abstract:

Results are reported from a search for the production of three-jet resonances in pp collisions at a center-of-mass energy √s=7TeV. The study uses the data sample collected by the CMS experiment at the LHC in 2011, corresponding to an integrated luminosity of 5.0fb-1. Events with high jet multiplicity and a large scalar sum of jet transverse momenta are analyzed for the presence of resonances in the three-jet invariant mass spectrum. No evidence for a narrow resonance is found in the data, and limits are set on the cross section for gluino pair production in an R-parity-violating supersymmetry model, for gluino masses greater than 280 GeV. Assuming a branching fraction for gluino decay into three jets of 100%, gluino masses below 460 GeV are excluded at 95% confidence level. These results significantly extend the range of previous limits. © 2012 CERN.

Abstract:

We analyze a sample of 3×106 quantum-correlated D0D̄0 pairs from 818pb-1 of e+e- collision data collected with the CLEO-c detector at Ecm=3.77GeV, to give an updated measurement of cos δ and a first determination of sin δ, where δ is the relative strong phase between doubly Cabibbo-suppressed D0→K+π- and Cabibbo-favored D ̄0→K+π- decay amplitudes. With no inputs from other experiments, we find cos δ=0.81-0.18-0.05+0.22+0.07, sin δ=-0.01±0.41±0.04, and |δ|=(10-53-0+28+13)°. By including external measurements of mixing parameters, we find alternative values of cos δ=1.15-0.17-0.08+0.19+0.00, sin δ=0.56-0.31-0.20+0.32+0.21, and δ=(18-17+11)°. Our results can be used to improve the world average uncertainty on the mixing parameter y by approximately 10%. © 2012 American Physical Society.

Abstract:

A search for a doubly-charged Higgs boson in pp collisions at √s=7 TeV is presented. The data correspond to an integrated luminosity of 4. 9 fb-1, collected by the CMS experiment at the LHC. The search is performed using events with three or more isolated charged leptons of any flavor, giving sensitivity to the decays of pair-produced triplet components Φ++Φ--, and Φ++Φ- from associated production. No excess is observed compared to the background prediction, and upper limits at the 95 % confidence level are set on the Φ++ production cross section, under specific assumptions on its branching fractions. Lower bounds on the Φ++ mass are reported, providing significantly more stringent constraints than previously published limits. © 2012 CERN for the benefit of the CMS collaboration.

Abstract:

The Large Synoptic Survey Telescope (LSST) uses an Active Optics System (AOS) to maintain system alignment and surface figure on its three large mirrors. Corrective actions fed to the LSST AOS are determined from 4 curvature based wavefront sensors located on the corners of the inscribed square within the 3.5 degree field of view. Each wavefront sensor is a split detector such that the halves are 1mm on either side of focus. In this paper we describe the development of the Active Optics Pipeline prototype that simulates processing the raw image data from the wavefront sensors through to wavefront estimation on to the active optics corrective actions. We also describe various wavefront estimation algorithms under development for the LSST active optics system. The algorithms proposed are comprised of the Zernike compensation routine which improve the accuracy of the wavefront estimate. Algorithm development has been aided by a bench top optical simulator which we also describe. The current software prototype combines MATLAB modules for image processing, tomographic reconstruction, atmospheric turbulence and Zemax for optical ray-tracing to simulate the closed loop behavior of the LSST AOS. We describe the overall simulation model and results for image processing using simulated images and initial results of the wavefront estimation algorithms. © 2012 SPIE.