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Search for a Standard Model Higgs Boson with a Dilepton and Missing Energy Signature

Description: The subject of this thesis is the search for a standard model Higgs boson decaying to a pair of W bosons that in turn decay leptonically, H {yields} W{sup +}W{sup -} {yields} {bar {ell}}{nu}{ell}{bar {nu}}. This search is performed considering events produced in p{bar p} collisions at {radical}s = 1.96 TeV, where two oppositely charged lepton candidates (e{sup +}e{sup -}, e{sup {+-}}{mu}{sup {-+}}, or {mu}{sup +}{mu}{sup -}), and missing transverse energy, have been reconstructed. The data were collected with the D0 detector at the Fermilab Tevatron collider, and are tested against the standard model predictions computed for a Higgs boson with mass in the range 115-200 GeV. No excess of events over background is observed, and limits on Standard Model Higgs boson production are determined. An interpretation of these limits within the hypothesis of a fourth-generation extension to the standard model is also given. The overall analysis scheme is the same for the three dilepton pairs being considered (e{sup +}e{sup -}, e{sup {+-}}{mu}{sup {-+}}, or {mu}{sup +}{mu}{sup -}); this thesis, however, describes in detail the study of the dimuon final state.
Date: June 1, 2011
Creator: Gerbaudo, Davide & U., /Princeton
Partner: UNT Libraries Government Documents Department

First Evidence of WW/WZ ---> l nu qq at the Tevatron

Description: We present the first evidence from a hadron collider of WW + WZ production with semileptonic decays. The data were recorded by the D0 detector at the Fermilab Tevatron and correspond to 1.07 fb{sup -1} of integrated luminosity obtained in proton-antiproton collisions at {radical}s = 1.96 TeV. The cross section observed for WW + WZ production is 20.2 {+-} 4.5 pb with a significance of 4.4 standard deviations.
Date: July 1, 2009
Creator: Haley, Joseph & U., /Princeton
Partner: UNT Libraries Government Documents Department

First evidence for WW and WZ diboson production with semi-leptonic decays at a Hadron Collider

Description: Presented is a measurement of the simultaneous production of a W{sup {+-}} boson in association with a second weak boson (W{sup {+-}} or Z{sup 0}) in p{bar p} collisions at {radical}s = 1.96 TeV. Events are consider with one electron or one muon, missing transverse energy, and at least two hadronic jets. The data were collected by the D0 detector in Run IIa of the Tevatron accelerator and correspond to 1.07 fb{sup -1} of integrated luminosity for each of the two channels (WW/WZ {yields} e{nu}q{bar q} and WW/WZ {yields} {mu}{nu}q{bar q}). The cross section for WW + WZ production is measured to be 20.2 {+-} 2.5(stat) {+-} 3.6(sys) {+-} 1.2(lum) pb with a Gaussian significance of 4.4 standard deviations above the background-only scenario. This measurement is consistent with the Standard Model prediction and represents the first direct evidence for WW and WZ production with semi-leptonic decays at a hadron collider.
Date: March 1, 2009
Creator: Haley, Joseph Glenn Biddle & U., /Princeton
Partner: UNT Libraries Government Documents Department

Limited Streamer Tubes for the BaBar Instrumented Flux Return Upgrade

Description: Starting from the very beginning of their operation the efficiency of the RPC chambers in the BaBar Instrumented Flux Return (IFR) has suffered serious degradation. After intensive investigation, various remediation efforts had been carried out, but without success. As a result the BaBar collaboration decided to replace the dying barrel RPC chambers about two years ago. To study the feasibility of using the Limited Streamer Tube (LST) as the replacement of RPC we carried out an R&D program that has resulted in BaBar's deciding to replace the barrel RPC's with LST's. In this report we summarize the major detector R&D results, and leave other issues of the IFR system upgrade to the future publications.
Date: October 11, 2005
Creator: Lu, C. & U., /Princeton
Partner: UNT Libraries Government Documents Department

Measurement of the top quark pair production cross section in the dilepton channel using lepton+track selection

Description: The production cross section for t{bar t} pairs decaying into two lepton final states was measured using data from the D0 detector at Fermilab. The measurement was made using a lepton+track selection, where one lepton is fully identified and the second lepton is observed as an isolated track. This analysis is designed to complement similar studies using two fully identified leptons [1]. The cross section for the lepton+track selection was found to be {sigma} = 5.2{sub -1.4}{sup +1.6}(stat){sub -0.8}{sup +0.9}(syst) {+-} 0.3(lumi) pb. The combined cross section using both the lepton+track data and the data from the electron+electron, electron+muon, and muon+muon samples is: {sigma} = 6.4{sub -0.9}{sup +0.9}(stat){sub -0.7}{sup +0.8}(syst) {+-} 0.4(lumi) pb.
Date: September 1, 2008
Creator: Wagner, Robert Emil & U., /Princeton
Partner: UNT Libraries Government Documents Department

A search for muon neutrino to electron neutrino oscillations at delta(m^2)>0.1 eV^2

Description: The evidence is compelling that neutrinos undergo flavor change as they propagate. In recent years, experiments have observed this phenomenon of neutrino oscillations using disparate neutrino sources: the sun, fission reactors, accelerators, and secondary cosmic rays. The standard model of particle physics needs only simple extensions - neutrino masses and mixing - to accommodate all neutrino oscillation results to date, save one. The 3.8{sigma}-significant {bar {nu}}{sub e} excess reported by the LSND collaboration is consistent with {bar {nu}}{sub {mu}} {yields}{bar {nu}}{sub e} oscillations with a mass-squared splitting of {Delta}m{sup 2} {approx} 1 eV{sup 2}. This signal, which has not been independently verified, is inconsistent with other oscillation evidence unless more daring standard model extensions (e.g. sterile neutrinos) are considered.
Date: November 1, 2007
Creator: Patterson, Ryan Benton & U., /Princeton
Partner: UNT Libraries Government Documents Department

Measurement of the Semileptonic Anti-B to D(*) Tau Anti-Nu/Tau Decays at BaBar

Description: Semileptonic B meson decays into final states containing the {tau} lepton are of interesting as they provide information on the Standard Model as well as a window on new physics effects. We present results on {bar B} {yields} D{sup (*)} {tau}{bar {nu}}{sub {tau}} decays where the second B in the event is fully reconstructed.
Date: November 11, 2011
Creator: Lopes Pegna, David & U., /Princeton
Partner: UNT Libraries Government Documents Department

Dalitz Analysis of D0 to K0(S) Pi+ Pi- and Measurement of the CKM Angle Gamma in Charged B+- Decays to D(*) K+- Decays

Description: Despite more than thirty years having elapsed since the discovery of CP violation, our understanding about the source and the nature of this phenomenon is still very limited. In the standard model of particle physics, CP violation is due to the presence of an non-irreducible weak phase in the Cabibbo-Kabayashi-Maskawa(CKM) matrix. Up to now, all the experimental results are in good agreement with the standard model. However, it is important for us to over-constrain the CKM quark-mixing matrix and explore the possibility of new physics beyond the standard model. The B meson provides an ideal place to measure CP violation due to its heavy mass and potentially large CP-violating effects. In particular, the angle {gamma} of the Unitary Triangle relating the elements of the CKM matrix is extremely crucial in terms of CP violation and constraints on the new physics models. Various methods using B{sup -} {yields} D{sup 0}K{sup -} decays have been proposed to measure based on the interference between the V{sub cb} and V{sub ub} amplitudes. Despite the simple concept, the measurement turns out to be experimentally challenging due to the small branching fraction and the small value of {tau}{sub B}, the amplitude ratio between the two contributing Feynman diagrams. In this thesis a novel technique to measure {gamma} in B{sup -} {yields} D{sup (*)} K{sup -} decay using a Dalitz plot analysis of D{sup 0} {yields} K{sub s}{pi}{sup +}{pi}{sup -} is presented. Until the turn on of LHC{sub b} [1] later in the decade, this remains the most promising method to measure {gamma}. This thesis is roughly separated into two parts. The first part involves a study of hadron spectroscopy and the Dalitz plot analysis of the D{sup 0} {yields} K{sub S}{sup 0}{pi}{sup +}{pi}{sup -}. The second part of the thesis involves the measurement of {gamma} in ...
Date: July 10, 2007
Creator: Lau, Yan-Pan & U., /Princeton
Partner: UNT Libraries Government Documents Department

Measurements of CP-Violating Asymmetries and Branching Fractions in the Decays of B Mesons to Charged Pions and Kaons at the Babar Detector

Description: This dissertation describes the measurement of branching fractions and CP asymmetries in neutral B meson decays to charmless two-body final states of charged pions and kaons. CP violation is a poorly-constrained phenomenon in the Standard model (SM) of particle physics and had been studied only in the kaon system before the Babar and Belle experiments. The decay of the neutral B meson to charged pions and kaons is particularly useful for the study of CP violation because they can be related to the Unitarity Triangle angle {alpha}.
Date: April 10, 2006
Creator: Danielson, Morris Nicholas & U., /Princeton
Partner: UNT Libraries Government Documents Department

Measurements of Exclusive B to X(C) L Anti-Nu(L) Decays And |V(Cb)| at BaBar

Description: The authors present recent results on exclusive {bar B} {yields} X{sub c}{ell}{sup -}{bar {nu}}{sub {ell}} decays and measurements of the CKM matrix element |V{sub cb}| based on data collected at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II e{sup +}e{sup -} storage rings.
Date: October 12, 2011
Creator: Pegna, David Lopes & U., /Princeton
Partner: UNT Libraries Government Documents Department

Measurement of Branching Fractions and CP-Violating Asymmetries in B0 to K0K0bar and B+ to K0barK+ Decays at the BaBar Experiment

Description: Over the last few years, the B factories have established the Cabbibo-Kobayashi-Maskawa mechanism of CP violation in the Standard Model through the study of the decays of B mesons. The focus of Belle and BaBar has now expanded to the search for signatures of new physics beyond the Standard Model, particularly through examination of flavor-changing neutral-current transitions, which proceed through diagrams involving virtual loops. These decays are suppressed in the Standard Model, increasing sensitivity to new-physics effects but decreasing branching fractions. Exploiting large and growing datasets, BaBar and Belle have made many measurements in loop decays where a b quark transitions to an s quark, observing hints of possible deviations from Standard Model expectations in CP-violating measurements.
Date: July 10, 2007
Creator: Biesiada, Jedrzej & U., /Princeton
Partner: UNT Libraries Government Documents Department

Search for the Higgs Boson in $H\to WW^{*}\to\ell\nu\ell\nu$ Decays

Description: We present a search for the standard model (SM) Higgs boson decaying to a pair of W bosons that in turn decay leptonically, H {yields} WW* {yields} {ell}{nu}{ell}{nu}. We consider events produced in p{bar p} collisions at {radical}s = 1.96 TeV, with two oppositely charged lepton candidates (e{sup +}e{sup -}, e{sup {+-}}{mu}{sup {+-}}, or {mu}{sup +}{mu}{sup -}), and missing transverse energy. The data were collected with the D0 detector at the Fermilab Tevatron collider, and correspond to an integrated luminosity of 5.4 fb{sup -1}. No excess of events over background is observed, and limits on SM Higgs boson production are determined.
Date: May 30, 2010
Creator: Gerbaudo, Davide & U., /Princeton
Partner: UNT Libraries Government Documents Department

Depleted argon from underground sources

Description: Argon is a powerful scintillator and an excellent medium for detection of ionization. Its high discrimination power against minimum ionization tracks, in favor of selection of nuclear recoils, makes it an attractive medium for direct detection of WIMP dark matter. However, cosmogenic {sup 39}Ar contamination in atmospheric argon limits the size of liquid argon dark matter detectors due to pile-up. The cosmic ray shielding by the earth means that Argon from deep underground is depleted in {sup 39}Ar. In Cortez Colorado a CO{sub 2} well has been discovered to contain approximately 500ppm of argon as a contamination in the CO{sub 2}. In order to produce argon for dark matter detectors we first concentrate the argon locally to 3-5% in an Ar, N{sub 2}, and He mixture, from the CO{sub 2} through chromatographic gas separation. The N{sub 2} and He will be removed by continuous cryogenic distillation in the Cryogenic Distillation Column recently built at Fermilab. In this talk we will discuss the entire extraction and purification process; with emphasis on the recent commissioning and initial performance of the cryogenic distillation column purification.
Date: September 1, 2011
Creator: Back, H.O.; U., /Princeton; Alton, A.; Coll., /Augustana U.; Calaprice, F.; Galbiati, C. et al.
Partner: UNT Libraries Government Documents Department

The BaBar Gas Bubbler Upgrade and Evaluation

Description: The Instrumented Flux Return region (muon and K{sub L} detection barrel) of the BaBar detector at SLAC requires careful monitoring of the gas flow through the detector array. This is currently done by a system of digital gas bubblers which monitor the flow rate by using photogate technology to detect the presence of bubbles formed by gas flowing through an internal oil chamber. Recently, however, a design flaw was discovered in these bubblers. Because the bubblers are connected directly to the detector array with no filter, during rises in atmospheric pressure or a drop in the gas flow rate (e.g. when the gas system is shut off for maintenance), the oil in this chamber could be forced backwards into the detector tubes. To compensate for this problem, we upgraded the existing gas bubbler systems by installing metal traps into the old gas lines to capture the oil. This installation was followed by an evaluation of the retro-fitted bubblers during which we determined a relationship between the bubble counting rate and the actual gas flow rate, but encountered recurring problems with baseline fluctuations and unstable bubble counting rates. Future work will involve the study of how these instabilities develop, and whether or not they can be mitigated.
Date: December 15, 2005
Creator: Gan, Yu; U., /Princeton; Young, C. & /SLAC
Partner: UNT Libraries Government Documents Department

Experience with the CMS Event Data Model

Description: The re-engineered CMS EDM was presented at CHEP in 2006. Since that time we have gained a lot of operational experience with the chosen model. We will present some of our findings, and attempt to evaluate how well it is meeting its goals. We will discuss some of the new features that have been added since 2006 as well as some of the problems that have been addressed. Also discussed is the level of adoption throughout CMS, which spans the trigger farm up to the final physics analysis. Future plans, in particular dealing with schema evolution and scaling, will be discussed briefly.
Date: June 1, 2009
Creator: Elmer, P.; U., /Princeton; Hegner, B.; /CERN; Sexton-Kennedy, L. & /Fermilab
Partner: UNT Libraries Government Documents Department

High momentum transfer inelastic muon scattering and test of scale invariance at NAL

Description: We propose a relatively simple first stage experiment with muons in the 50-150 GeV range. The experiment is designed to optimize conditions for testing scale invariance while providing some information about the final state, as a test of various theories of high energy interactions. The proposed use of an iron spectrometer and of a high Z (>1) target with a low intensity ({approx}10{sup 6}/sec) muon beam should greatly reduce the cost and complexity of the experiment and especially ease the construction of the beam. It may even be possible to make an adequate muon beam for this purpose from the planned 3.5 mrad high intensity pion beam. A higher intensity muon beam can be used to extend the range in q{sup 2}. Information gained in this first experiment could greatly assist the planning of a more sophisticated experiment proposed for the high intensity {mu} beam.
Date: June 1, 1970
Creator: Chen, K.Wendell, (Spokesperson); U., /Princeton; Hand, L.N. & /Cornell U., LNS
Partner: UNT Libraries Government Documents Department

The Hierarchical Build-Up of Massive Galaxies And the Intracluster Light Since z=1

Description: We use a set of simulation-based models for the dissipationless evolution of galaxies since z = 1 to constrain the fate of accreted satellites embedded in dark matter subhalos. These models assign stellar mass to dark matter halos at z = 1 by relating the observed galaxy stellar mass function (GSMF) to the halo+subhalo mass function monotonically. The evolution of the stellar mass content is then followed using halo merger trees extracted from N-body simulations. Our models are differentiated only in the fate assigned to satellite galaxies once subhalos, within which satellites are embedded, disrupt. These models are confronted with the observed evolution in the massive end of the GSMF, the z {approx} 0 brightest cluster galaxy (BCG)-cluster mass relation, and the combined BCG and intracluster light (ICL) luminosity distribution--all observables expected to evolve approximately dissipationlessly since z = 1. The combined observational constraints favor a model in which the vast majority ({approx}> 80%) of satellite stars from disrupted subhalos go into the ICL (operationally defined here as light below a surface brightness cut of {mu}{sub i} {approx} 23mag arcsec{sup -2}). Conversely, models that leave behind a significant population of satellite galaxies once the subhalo has disrupted are strongly disfavored, as are models that put a significant fraction of satellite stars into the BCG. Our results show that observations of the ICL provide useful and unique constraints on models of galaxy merging and the dissipationless evolution of galaxies in groups and clusters.
Date: March 19, 2007
Creator: Conroy, Charlie; U., /Princeton; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC; Kravtsov, Andrey V. & /Chicago U., Astron. Astrophys. Ctr. /Chicago U., EFI
Partner: UNT Libraries Government Documents Department

A search for direct muon production in the forward direction

Description: We propose to search for direct muon production in the forward direction from 300 GeV protons incident on a heavy nuclear target. By using the first stage of the Ml beam as a source of a diffracted proton beam and the second and third stages of Ml as a spectrometer, one can make a measurement of the direct muon to pion ratio at values of x between 0.3 and 0.75. If this ratio is on the order of 10{sup -4}, the event rates are on the order of 800 direct muons/hr. at an x of .5. The modifications to the Ml beam are minor.
Date: January 1, 1974
Creator: Buchholz, D.; /Caltech; Johnson, Rolland P.; /Fermilab; Sumner, R.L.; U., /Princeton et al.
Partner: UNT Libraries Government Documents Department

Proposal to study the reactions p + p --> p + (p + pi+ + pi-) / (n + pi+) at 200-GeV and 500-GeV

Description: We would like to study isobar formation at 200-500 GeV in the moderate t-range (-0.1>t>-0.4), concentrating on the modes (p{pi}{sup +}{pi}{sup -}) and (n{pi}{sup +}). These isobar decay modes have such strong signatures that every event will be fully reconstructed with at least a 1C fit even without momentum analysis. Existing evidence is that these modes are either dominant or very strong in the cases of several known isobars. Logistically, our experiment is designed to be suitable for the initial phase of operation of the NAL accelerator. We require only a diffraction-scattered proton beam. The apparatus required is small, simple, and compact enough to be located in the machine tunnel. We do not require a magnet or any rigging, and at least the first results can be obtained with a polyethylene target. the data rate should be very high, and the information gained should be very informative on possible microstructure in the baryon mass spectrum, on the interaction properties of the Pomeron, and on the possible utility of the double-Ragge model and the Veneziano four-point function. A 28.5 GeV run of this experiment has been approved as experiment number 533 at the AGS, and will take place during October '70-May '71. That run will test all of the same apparatus needed for the NAL experiment.
Date: June 1, 1970
Creator: Ash, W.W.; Cheng, D.C.; Coyne, D.; O'Neill, G.K.; U., /Princeton; Goggi, G. et al.
Partner: UNT Libraries Government Documents Department