DISCOVERY AND MEASUREMENT OF EXCITED B HADRONS AT THE COLLIDER DETECTOR AT FERMILAB

This thesis presents evidence for the B∗∗0 and S(∗)± b hadrons in proton-antiproton collisions at a center of mass energy of 1.96 TeV, using data collected by the Collider Detector at Fermilab. In the search for B∗∗0→B±p∓, two B± decay modes are reconstructed: B±→J/yK±, where J/y→μ+μ−, and B± → ¯D0p±, where ¯D0 →K±p∓. Both modes are reconstructed using 370±20 pb−1 of data. Combining the B± meson with a charged pion to reconstruct B∗∗0 led to the observation and measurement of the masses of the two narrow B∗∗0 states, B01 and B∗0 2 , of m(B01 ) = 5734±3 (stat.) ±2 (syst.) MeV/c2 m(B∗0 2 ) = 5738±5 (stat.) ±1 (syst.) MeV/c2 In the search for S(∗)± b →L0b p±, the L0b is reconstructed in the decay mode L0b →L+ c p−, where L+ c → pK−p+, using 1070±60 pb−1 of data. Upon combining the L0b candidate with a charged pion, all four of the S(∗)± b states are observed and their masses measured to be: m(S+ b ) = 5807.8+2.0 −2.2 (stat.)±1.7 (syst.) MeV/c2 m(S−b ) = 5815.2±1.0 (stat.)±1.7 (syst.) MeV/c2 m(S∗+ b ) = 5829.0+1.6 −1.8 (stat.)+1.7 −1.8 (syst.) MeV/c2 m(S∗− b ) = 5836.4±2.0 (stat.)+1.8 −1.7 (syst.) MeV/c2 This is the first observation of the S(∗)± b baryons

Electronic Correlations and Unconventional Spectral Weight Transfer in the High-Temperature Pnictide BaFe2-xCoxAs2 Superconductor Using Infrared Spectroscopy

We report an infrared optical study of the pnictide high-temperature superconductor BaFe1.84Co0.16As2 and its parent compound BaFe2As2. We demonstrate that electronic correlations are moderately strong and do not change across the spin-density wave transition or with doping. By examining the energy scale and direction of spectral weight transfer, we argue that Hund\u27s coupling J is the primary mechanism that gives rise to correlations

High energy pseudogap and its evolution with doping in Fe-based superconductors as revealed by optical spectroscopy

We report optical spectroscopic measurements on electron- and hole-doped BaFe2As2. We show that the compounds in the normal state are not simple metals. The optical conductivity spectra contain, in addition to the free carrier response at low frequency, a temperature-dependent gap-like suppression at rather high energy scale near 0.6 eV. This suppression evolves with the As-Fe-As bond angle induced by electron- or hole-doping. Furthermore, the feature becomes much weaker in the Fe-chalcogenide compounds. We elaborate that the feature is caused by the strong Hund's rule coupling effect between the itinerant electrons and localized electron moment arising from the multiple Fe 3d orbitals. Our experiments demonstrate the coexistence of itinerant and localized electrons in iron-based compounds, which would then lead to a more comprehensive picture about the metallic magnetism in the materials.Comment: 6 pages, 7 figure

Guest Editorial Recent Advances in Capacity Approaching Codes

[No abstract available

Operational experience, improvements, and performance of the CDF Run II silicon vertex detector

The Collider Detector at Fermilab (CDF) pursues a broad physics program at Fermilab's Tevatron collider. Between Run II commissioning in early 2001 and the end of operations in September 2011, the Tevatron delivered 12 fb-1 of integrated luminosity of p-pbar collisions at sqrt(s)=1.96 TeV. Many physics analyses undertaken by CDF require heavy flavor tagging with large charged particle tracking acceptance. To realize these goals, in 2001 CDF installed eight layers of silicon microstrip detectors around its interaction region. These detectors were designed for 2--5 years of operation, radiation doses up to 2 Mrad (0.02 Gy), and were expected to be replaced in 2004. The sensors were not replaced, and the Tevatron run was extended for several years beyond its design, exposing the sensors and electronics to much higher radiation doses than anticipated. In this paper we describe the operational challenges encountered over the past 10 years of running the CDF silicon detectors, the preventive measures undertaken, and the improvements made along the way to ensure their optimal performance for collecting high quality physics data. In addition, we describe the quantities and methods used to monitor radiation damage in the sensors for optimal performance and summarize the detector performance quantities important to CDF's physics program, including vertex resolution, heavy flavor tagging, and silicon vertex trigger performance.Comment: Preprint accepted for publication in Nuclear Instruments and Methods A (07/31/2013

An infrared probe of the insulator-to-metal transition in GaMnAs and GaBeAs

We report infrared studies of the insulator-to-metal transition (IMT) in GaAs doped with either magnetic (Mn) or non-magnetic acceptors (Be). We observe a resonance with a natural assignment to impurity states in the insulating regime of Ga$_{1-x}$Mn$_x$As, which persists across the IMT to the highest doping (16%). Beyond the IMT boundary, behavior combining insulating and metallic trends also persists to the highest Mn doping. Be doped samples however, display conventional metallicity just above the critical IMT concentration, with features indicative of transport within the host valence band