Rubin-LSST

Abstract:

In the context of recent observational results that show massive ellipticals were in place at high redshifts, we reassess the status of monolithic collapse in a ACDM universe. Using a sample of over 2000 galaxies from the Sloan Digital Sky Survey, by comparing the dynamical mass and stellar mass (estimated from colors) we find that ellipticals have "cores" that are baryon-dominated within their half-light radius. These galaxies correspond to 3 σ peaks in the spherical collapse model if the total mass in the halo is assumed to be 20 times the dynamical mass within the half-light radius. This value yields stellar mass-to-total mass ratios of 8%, compared to a cosmological baryon fraction of 18% derived from the first 3 years of WMAP observations alone. We further develop a method for reconstructing the concentration halo parameter c of the progenitors of these galaxies by utilizing adiabatic contraction. Although the analysis is done within the framework of monolithic collapse, the resulting distribution of c is lognormal with a peak value of c ∼ 3-10 and a distribution width similar to the results of N-body simulations. We also derive scaling relations between stellar and dynamical mass and the velocity dispersion, and find that these are sufficient to recover the tilt of the fundamental plane. © 2006. The American Astronomical Society. All rights reserved.

Abstract:

We present a measurement of RB, the ratio of the branching fraction for the rare decay D0→K+π- to that for the Cabibbo-favored decay D0→K-π+. Charge-conjugate decays are implicitly included. A signal of 2005±104 events for the decay D0→K+π- is obtained using the CDF II detector at the Fermilab Tevatron collider. The data set corresponds to an integrated luminosity of 0.35fb-1 produced in p̄p collisions at s=1.96TeV. Assuming no mixing, we find RB=[4.05±0.21(stat)±0.11(syst)] ×10-3. This measurement is consistent with the world average, and comparable in accuracy with the best measurements from other experiments. © 2006 The American Physical Society.

Abstract:

We describe a measurement of the top quark mass using events with two charged leptons collected by the CDF II detector from pp̄ collisions with s=1.96TeV at the Fermilab Tevatron. The likelihood in top quark mass is calculated for each event by convoluting the leading order matrix element describing qq̄→tt̄→blνlb̄l′νl′ with detector resolution functions. The presence of background events in the data sample is modeled using similar calculations involving the matrix elements for major background processes. In a data sample with integrated luminosity of 340pb-1, we observe 33 candidate events and measure Mtop=165.2±6.1(stat.) ±3.4(syst.)GeV/c2. This measurement represents the first application of this method to events with two charged leptons and is the most precise single measurement of the top quark mass in this channel. © 2006 The American Physical Society.