Mu3e

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.

Abstract:

The suppression of the individual Υ(nS) states in PbPb collisions with respect to their yields in pp data has been measured. The PbPb and pp data sets used in the analysis correspond to integrated luminosities of 150μb -1 and 230nb-1, respectively, collected in 2011 by the CMS experiment at the LHC, at a center-of-mass energy per nucleon pair of 2.76TeV. The Υ(nS) yields are measured from the dimuon invariant mass spectra. The suppression of the Υ(nS) yields in PbPb relative to the yields in pp, scaled by the number of nucleon-nucleon collisions, RAA, is measured as a function of the collision centrality. Integrated over centrality, the RAA values are 0.56±0.08(stat)±0.07(syst), 0.12±0.04(stat)±0.02(syst), and lower than 0.10 (at 95% confidence level), for the Υ(1S), Υ(2S), and Υ(3S) states, respectively. The results demonstrate the sequential suppression of the Υ(nS) states in PbPb collisions at LHC energies. © 2012 CERN.