Browsing by Author "Padley, B. Paul"

Now showing 1 - 7 of 7
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    A comparison of multivariate data analysis techniques as applied to the identification of electrons and tau leptons
    (2001) Askew, Andrew Warren; Padley, B. Paul
    This thesis compares the performance of Probability Density Estimation and Neural Networks as applied to the identification of tau leptons and electrons at the DO detector for Run II. The theory behind each method of multivariate analysis is briefly described. The efficiencies of each of the methods are compared from analysis of Monte Carlo data samples, and optimal choices for the discrimination between signal and background are made.
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    Identification of the tau lepton through its hadronic decay modes at the DO collider detector
    (2000) Sen, Naresh; Padley, B. Paul
    This thesis focuses on tau identification efficiencies in Monte Carlo simulations of various processes by implementing optimization techniques to determine optimal values for selection cuts on discriminant variables. Two sets of discriminants were studied: the first set consisted of only the Fisher discriminant, and the second set comprised the jet width and profile. Results obtained for the two sets are comparable for the central region (|eta| < 1.1) of the DO detector. For the forward region (|eta| ≥ 1.1), the optimization procedure did not yield optimal values for the set of variables used, suggesting that the signatures of the tau decay products in the forward regions is different from that in the central region, so that it appears that a different approach is required to identify the tau in the forward region. Given that the tau is to be identified through a reconstruction of its decay products, the complex interplay of the multitude of variables that need to be taken into account make the task of tau identification an ideal candidate for a multivariate analysis.
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    K*(892)0 Lambda and K+ Sigma* (1385)- Photoproduction on the Deuteron
    (2011) Mattione, Paul; Padley, B. Paul
    Thirteen N* states have been well-established according to the Particle Data Group, but some relativized quark models predict that many more N* resonances exist. Diquark models predict that the N* spectrum is limited by a correlated quark-pair in the nucleon, but there is strong evidence for the existence of the [Special characters omitted.] (1900)** resonance, which is absent in diquark models. Measuring the spectrum of N* states will provide valuable information on the relevant degrees of freedom within the nucleons. Most of the experimental searches for the N* states have been conducted in the πN channel. Some models of baryon decays predict that most of the unobserved N* states couple somewhat weakly to the πN channel, and that some couple non-negligibly to the KY, K*Y , and KY* channels. Measurements of the cross sections and polarization observables of strangeness photoproduction reactions can provide additional information on the spectrum of N* states. These measurements can be used in coupled-channel partial-wave analyses that can provide simultaneous constraints on the N* resonance parameters from several channels. These analyses can also take into account hadronic rescattering, which is predicted to have a large effect on the measured cross sections. However, to determine the isospin decomposition of the photo-transition amplitudes to these channels, photoproduction measurements are necessary on both the proton and the neutron. Measurements of the differential cross sections of the γn [arrow right] K* (892) 0 Λ and γn [arrow right] K + Σ*(1385) - reactions have been performed using data from the Jefferson Lab Hall B CLAS g13 experiment. No experimental cross section data have yet been published on the γn [arrow right] K* (892) 0 Λ reaction, and the only published cross section data on the γn [arrow right] K + Σ*(1385) - reaction are limited to forward angles, where t -channel K + and K* + exchanges are predicted to dominate. These cross sections are compared against theoretical models to study the channel interactions that give rise to their distributions. These reactions also have the same final state particles ( K + π - pπ - ), so studies of their potential interference were performed as well. A measurement of the γn [arrow right] pπ - cross section was also performed, and the agreement with published results within the uncertainties validated the integrity of the data and procedures used in this analysis.
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    Measurement of the gamma W boson decaying to muon-neutrino-photon cross section, limits on anomalous trilinear vector boson couplings, and the radiation amplitude zero in proton-antiproton collisions at center of mass energy = 1.96 TeV
    (2005) Askew, Andrew W.; Padley, B. Paul
    This thesis details the measurement of the pp¯ → W gamma + X → munugamma + X cross section at s = 1.96 TeV using the DO detector at Fermilab, in 134.5 pb -1 of integrated luminosity. From the photon E T spectrum limits on anomalous couplings of the photon to the W are obtained. At 95% confidence level, limits of -1.05 < Deltakappa < 1.04 for lambda = 0 and -0.28 <lambda < 0.27 for Deltakappa = 0 are obtained on the anomalous coupling parameters. The charge signed rapidity difference from the data is displayed, and its significance discussed.
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    Natural supersymmetry, muon g−2, and the last crevices for the top squark
    (American Physical Society, 2015) Padley, B. Paul; Sinha, Kuver; Wang, Kechen
    We study the interplay of natural supersymmetry and a supersymmetric solution to the discrepancy observed in measurements of the muon magnetic moment. The strongest constraints on the parameter space currently come from chargino searches in the trilepton channel and slepton searches in the dilepton channel at the LHC, and vast regions are currently allowed, especially at large tanβ. With light top squarks in the spectrum, as required from naturalness arguments, the situation changes dramatically; stop-assisted chargino and neutralino production via t˜→bχ˜±1 and t˜→tχ˜01 are already probing the entire parameter space compatible with the muon magnetic moment at tanβ∼O(10), while upcoming stop searches will probe most of the parameter space at larger tanβ∼40. Direct Higgsino searches as well as compressed slepton and stop searches are crucial to close out corners of parameter space. We consider one such example: in the presence of light sleptons and charginos as required to obtain appreciable contributions to the muon magnetic moment, compressed stops can dominantly undergo the following decay t˜→bℓ˜ν(ν˜ℓ)→bℓνχ˜01, facilitated by off-shell charginos. We find that the enhanced branching to leptons leads to a 5σ mass reach (with 3000  fb−1 of data at LHC14) of mt˜∼350  GeV, with the mass difference between stops and the lightest neutralino being ∼80  GeV. This will further close out a significant part of the parameter space compatible with naturalness and the muon magnetic moment.
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    Testing of the muon port card and related electronics for the CMS endcap muon trigger system
    (2004) Pawloski, Gregory J.; Padley, B. Paul
    This thesis is related to the design of the level one endcap muon trigger system for the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). This system is designed to use muon measurements to help reduce a computationally overwhelming 40 MHz signal of collision data (∼40 TBytes/sec) to a manageable 33kHz (∼33GBytes/sec) [1]. The main focus of this thesis will be on the validation of one of the electronics boards in the trigger device chain. This board is used to pick the 3 most interesting muons out of 18 measured in a single crossing. Referred to as the Muon Port Card, this card will be located on the periphery of the detector and can be tested through a VME back plane.
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    The study of W γ production at DØ: Anomalous coupling limits and the radiation amplitude zero
    (2007) Pawloski, Gregory J.; Padley, B. Paul
    W γ production is analyzed in the electron and muon decay channels with approximately 1 fb –1 of data from pp collisions that were produced at a center-of-mass energy of [special characters omitted] = 1.96 TeV and that were collected by the D∅ detector at the Fermilab Tevatron collider. The inclusive p p → ℓνγ cross section is measured in both channels and is found to be consistent with the Standard Model expectation of 2.08 ± 0.05 PDF pb for events with a photon E T > 11 GeV , Δ R ℓγ > 0.7, and ℓνγ transverse mass greater than 90 GeV . The observed cross section is measured to be 2.05 ± 0.18 stat ± 0.10 sys ± 0.13 lumi pb and 1.72 ± 0.19 stat ± 0.15 sys ± 0.10 lumi pb for the electron and muon channels respectively. The photon E T spectrum is examined for indications of anomalous WW γ couplings. No evidence is found, and the following one-dimensional limits are set at a 95% confidence level: –0.18 The observed charge-signed photon-lepton rapidity difference is consistent with the Standard Model prediction and is indicative of the theoretically expected radiation amplitude zero. The distribution exhibits a bimodal structure which is expected from the destructive interference, with the unimodal hypothesis being ruled out at the 94% confidence level.