The SLD Vertex Detector Upgrade (VXD3) and a study of b$\bar{b}$g events

Abstract

This thesis presents a variety of work concerning the design, construction and use of the SLD's vertex detector. SLD's pioneering 120 Mpixel vertex detector, VXD2, was replaced by VXD3, a 307Mpixel CCD vertex detector in January 1996. The motivation for the upgrade detector and its subsquent construction and testing are described in some detail. This work represents the collaborative work of a large number of people. My work was mainly carried out at EEV on the testing of the CCDs and subsequent ladders. VXD3 was commissioned during the 1996 SLD run and performed very close to design specifications. Monitoring the position of VXD3 is crucial for reconstructing the data in the detector for physics analysis. This was carried out using a capacitive wire position monitoring system. The system indicated that VXD3 was very stable during the whole of the 1996 run, except for known controlled movements. VXD3 was aligned globally for each period in-between these known movements using the tracks from e+e-* Z°-p hadrons. The structure of three-jet bbg events has been studied using hadronic Z° decays from the 1993-1995 SLD data. Three-jet final states were selected and the CCDbased vertex detector was used to identify two of the jets as ab or b. The distributions of the gluon energy and polar angle with respect to the electron beam direction were examined and were compared with perturbative QCD predictions. If was found that the QCD Parton Shower prediction was needed to describe the data well. These distributions are potentially sensitive to an anomalous b chromomagnetic moment K. K was measured to be-0.031±ö. ö39(, tat.)±ö. öö3(Syst.), which is consistent with the Standard Model, with 95% confidence level limit,-0.106 <'<0.044. 1 Acknowledgements Many people have contributed to the work covered in this thesis. I would like to thank them all. In particular I would like to thank the following: My supervisor, Steve Watts, and Chris Damerell and Phil Burrows without whom you would not be reading this thesis. Everybody at EEV, in particular Colin Hotston, John Bloomer, Wolfgang Suske and all the clean room staff. All my colleagues at SLAC and Brunel. There are too many to mention by name, but they know who they are. Special thanks go to

Affinity and kinetic modulation of polyamide–DNA interactions byN‐modification of the heterocycles

“…S ynthetic pyrrole (Py) and imidazole (Im) containing analogs (Figure 1) of the naturally occurring polyamide (PA) compounds distamycin and netropsin have been shown to selectively bind as ''stacked'' dimers to the minor groove of DNA with high affinity and selectivity. [1][2][3][4][5][6][7][8] The addition of a formamido (f) group to the N-terminus of PAs increases the binding affinity and causes Affinity and Kinetic Modulation of Polyamide-DNA Interactions by N-Modification of the Heterocycles the stacking to be in a ''staggered'' position as opposed to ''overlapped'' stacking. 1,9,10 Because of their high affinity and sequence selectivity, PAs have demonstrated potential as therapeutics.…”

“…Based on their ability to target, alter, and control gene expression, especially those genes associated with such diseases as cancer, PAs are of interest for the design and development of new types of therapeutics. [1][2][3][4][11][12][13][14][15][16] The PA, f-ImPyIm (Figure 1), binds to the cognate DNA sequence 5 0 -ACGCGT-3 0 as a stacked, staggered homodimer with a high binding affinity, K eq [ 10 8 M 21 , for a small molecule. 9,10,17,18 Closely related trimer PAs bind to their cognate sites from 10 to 100 fold more weakly.…”

Polyamide‐ and RNA‐Based Activators in Living Cells: A Major Step Towards Controlling Gene Expression

“…One of these peptoid-activation domains was then tethered to a DNA-binding polyamide, a class of small molecules able to bind to the minor groove of DNA with high intrinsic selectivity and affinity (vide infra), [12] to give compound 1. [13] This strategy has been pursued for peptidic and small-molecule activation domains with considerable success in vitro before.…”

“…A specific pair of heterocycles recognizes one particular base pair in the minor groove of DNA by means of shape and H-bond contacts (Scheme 1). [12] These guidelines allowed, for example, quite specific control of the expression of hypoxia-inducible genes with "naked" polyamides at 1 mm concentrations. [16] Imprinting such selectivity into conjugates like 1 might be a logical next step.…”

“…General guidelines for DNA recognition of polyamides. [12] High-affinity polyamides form faceto-face dimers with countercurrent strands kept in register by a suitable element, often a turn inducer. The C terminus of the polyamide chain featuring N-methylated heterocycles points towards the 3'-end of the DNA strand.…”