New developments in measurements of CP violation

We present several alternative techniques used by the BaBar Collaboration in order to measure the Unitarity Triangle angle gamma. We also present the results of two searches designed to improve the measurements of sin(2beta) using penguin B decay modes by reducing the hadronic corrections uncertainties.Comment: 6 pages, 4 figures, Contribution to Moriond ElectroWeak 2006 Proceeding

LAT Onboard Science: Gamma-Ray Burst Identification

The main goal of the Large Area Telescope (LAT) onboard science program is to provide quick identification and localization of Gamma Ray Bursts (GRB) onboard the LAT for follow-up observations by other observatories. The GRB identification and localization algorithm will provide celestial coordinates with an error region that will be distributed via the Gamma ray burst Coordinate Network (GCN). We present results that show our sensitivity to bursts as characterized using Monte Carlo simulations of the GLAST observatory. We describe and characterize the method of onboard track determination and the GRB identification and localization algorithm. Onboard track determination is considerably different than in the onground case, resulting in a substantially altered point spread function. The algorithm contains tunable parameters which may be adjusted after launch when real bursts characteristics at very high energies have been identified

Study of K_S Production with the BaBar Experiment

We study the inclusive production of short-lived neutral kaons (K{sub S}) with the BABAR experiment at the Stanford Linear Accelerator Center. The study is based on a sample of 383 million B{bar B} pairs produced in e{sup +}e{sup -}collisions at the {Upsilon}(4S) resonance, in which one B meson has been fully reconstructed. We select a clean sample of K{sub S} mesons and compare kinematic spectra for data and simulation. We find that the simulation overestimates the total production rate of K{sub S} and we see differences in the shape of the K{sub S} momentum spectra. We derive correction factors for different momentum intervals to bring the simulation into better agreement with the observed data

On the influence of the cosmological constant on gravitational lensing in small systems

The cosmological constant Lambda affects gravitational lensing phenomena. The contribution of Lambda to the observable angular positions of multiple images and to their amplification and time delay is here computed through a study in the weak deflection limit of the equations of motion in the Schwarzschild-de Sitter metric. Due to Lambda the unresolved images are slightly demagnified, the radius of the Einstein ring decreases and the time delay increases. The effect is however negligible for near lenses. In the case of null cosmological constant, we provide some updated results on lensing by a Schwarzschild black hole.Comment: 8 pages, 1 figure; v2: extended discussion on the lens equation, references added, results unchanged, in press on PR

Cooling the dark energy camera instrument

DECam, camera for the Dark Energy Survey (DES), is undergoing general design and component testing. For an overview see DePoy, et al in these proceedings. For a description of the imager, see Cease, et al in these proceedings. The CCD instrument will be mounted at the prime focus of the CTIO Blanco 4m telescope. The instrument temperature will be 173K with a heat load of 113W. In similar applications, cooling CCD instruments at the prime focus has been accomplished by three general methods. Liquid nitrogen reservoirs have been constructed to operate in any orientation, pulse tube cryocoolers have been used when tilt angles are limited and Joule-Thompson or Stirling cryocoolers have been used with smaller heat loads. Gifford-MacMahon cooling has been used at the Cassegrain but not at the prime focus. For DES, the combined requirements of high heat load, temperature stability, low vibration, operation in any orientation, liquid nitrogen cost and limited space available led to the design of a pumped, closed loop, circulating nitrogen system. At zenith the instrument will be twelve meters above the pump/cryocooler station. This cooling system expected to have a 10,000 hour maintenance interval. This paper will describe the engineering basis including the thermal model, unbalanced forces, cooldown time, the single and two-phase flow model

A Study of Neutron Proton Charge Exchange Scattering in the Momentum Range 50 - 200 GeV

It is proposed to measure the neutron-proton charge-exchange cross-section in an on-line counter experiment for four-momentum transfers between .002 and 1.0 (GeV/c){sup 2}. The experiment will be performed in an intense neutron beam with a continuous momentum spectrum; data will be taken simultaneously for all momenta between 50 and 200 GeV/c. At a beam intensity of 10{sup 7} neutrons/pulse, the true data-collection rate will be about .5 per pulse. Approximately 90,000 events will be obtained. The vector momenta of both outgoing particles are measured, resulting in a 3-constraint fit. The two-body topology allows a large rejection of background by the counter logic

Analysis Methods for Milky Way Dark Matter Halo Detection

We present methods for the analysis of dark matter annihilation in the smooth halo of the Milky Way galaxy. We model the diffuse gamma-ray background using GALPROP, and model the halo using an NFW profile and the gamma-ray spectrum for WIMP pair annihilation. We plan to combine these models with the point source catalog and a simple model for the extragalactic gamma ray background. Using the downhill simplex method to converge on the maximum likelihood value, we can vary key parameters in these models and fit them to the gamma-ray data. Through the use of the Markov Chain Monte Carlo (MCMC) method we can then map out the likelihood as a function of the model parameters to estimate the correlated errors on these parameters

Optically-Selected Cluster Catalogs As a Precision Cosmology Tool

We introduce a framework for describing the halo selection function of optical cluster finders. We treat the problem as being separable into a term that describes the intrinsic galaxy content of a halo (the Halo Occupation Distribution, or HOD) and a term that captures the effects of projection and selection by the particular cluster finding algorithm. Using mock galaxy catalogs tuned to reproduce the luminosity dependent correlation function and the empirical color-density relation measured in the SDSS, we characterize the maxBCG algorithm applied by Koester et al. to the SDSS galaxy catalog. We define and calibrate measures of completeness and purity for this algorithm, and demonstrate successful recovery of the underlying cosmology and HOD when applied to the mock catalogs. We identify principal components--combinations of cosmology and HOD parameters--that are recovered by survey counts as a function of richness, and demonstrate that percent-level accuracies are possible in the first two components, if the selection function can be understood to {approx} 15% accuracy

Radiation monitoring with CVD Diamonds and PIN Diodes at BaBar

The BaBar experiment at the Stanford Linear Accelerator Center has been using two polycrystalline chemical vapor deposition (pCVD) diamonds and 12 silicon PIN diodes for radiation monitoring and protection of the Silicon Vertex Tracker (SVT). We have used the pCVD diamonds for more than 3 years, and the PIN diodes for 7 years. We will describe the SVT and SVT radiation monitoring system as well as the operational difficulties and radiation damage effects on the PIN diodes and pCVD diamonds in a high-energy physics environment