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Exploiting the single-lepton event structure in the search for the top quark

Description: We discuss whether the event structure can be useful in searching for the top quark in the single-lepton channel at the Tevatron, where the main obstacle is a considerable background from QCD W+ multijet production. We restrict our discussion to the case of a Standard Model top quark of heavy mass, M{sub top}>100 GeV.
Date: June 1, 1993
Creator: Cobal, M.; Leone, S. & Grassman, H.
Partner: UNT Libraries Government Documents Department

[High Energy Physics Program at the University of Alabama. Final report]

Description: The High Energy Physics group at University of Alabama is a member of the L3 collaboration studying e+e{minus} collisions near the Z{degree} pole at the LEP accelerator at CERN. About 2 million Z{degree} events have been accumulated and the experiment has been prolific in publishing results on the Z resonance parameters, the Z couplings to all leptons and quarks with mass less than half the Z mass, searches for new particles and interactions, and studies of strong interactions and/or weak charged current decays of the quarks and leptons abundantly produced in Z decays. The group is contributing to data analysis as well as to detector hardware. In particular, the authors are involved in a major hardware upgrade for the experiment, namely the design, construction and commissioning of a Silicon Microvertex Detector (SMD) which has successfully been installed for operation during the present grant period. The authors present here a report on their recent L3 activities and their plans for the next grant period of twelve months (April 1, 1994--March 31, 1995). Their main interests in data analysis are in the study of single photon final states and the physics made more accessible by the SMD, such as heavy flavor physics. Their hardware efforts continue to be concentrated on the high precision capacitive and optical alignment monitoring systems for the SMD and also includes gas monitoring for the muon system. They are also planning to participate in the coming upgrade of the L3 detector.
Date: October 1, 1993
Creator: Baksay, L. & Busenitz, J.K.
Partner: UNT Libraries Government Documents Department

Overview of the GEM muon system cosmic ray test program at the SSCL

Description: Muon track resolution exceeding 75-{mu}m per plane is one of the main strengths of the GEM detector design, and will be crucial in searches for Higgs Bosons, heavy Z-Bosons, technicolor, and supersymmetry. Achieving this resolution coal requires improved precision in muon chambers and their alignment. A cosmic ray test stand known as the Texas Test Rio, (TTR) has been created at the SSCL for studying candidate GEM muon chamber technologies. Test results led to selecting Cathode Strip Chambers (CSC) as the GEM muon system baseline chamber technology.
Date: April 1, 1993
Creator: Milner, E.C.
Partner: UNT Libraries Government Documents Department

Duke University High Energy Physics; Progress report, December 1, 1990--March 15, 1993

Description: The research program of the Duke High Energy Physics Group is described in this Progress Report and a separate Proposal containing their plans for 1994. These two documents are supplemented by compilations of selected publications, thesis abstracts, and the curriculum vitae of the eleven Ph.D. physicists who are carrying out this research program. This Progress Report contains a review of the research which has been done over the first half (1992 and 1993 to date) of the current three-year DOE grant, plus some earlier research to establish a broader perspective of the research interests. High energy physics research at Duke has three components. The first, Task A, is based upon experiments carried out at Fermilab`s Tevatron Collider. The group is finishing the analysis of data from their first collider experiment (E735), a study of inclusive particle production from {bar p} p collisions at {radical}{bar s} = 1.8 TeV. The second component of the research, Task B, deals primarily with heavy flavor physics. The third part of the research program, Task D, deals with preparation for research at the SSC. The authors have been active in the development of tracking detectors for the SSC since 1989, and are now concentrating on the design and construction of straw tube drift chambers for the solenoid detector.
Date: March 1, 1993
Creator: Fortney, L.R.; Goshaw, A.T. & Walker, W.D.
Partner: UNT Libraries Government Documents Department

Search for the top quark and other new particles at D0

Description: Preliminary results from the search for the top quark and other new particles in p[bar p] collisions at [radical]s = 1.8 TeV are reported. In a data sample corresponding to an integrated luminosity of about 7.5 pb[sup [minus]1], one candidate event for top quark is found in the di-lepton channel. A lower limit for the mass of the top quark of 103 GeV/c[sup 2] (99 Gev/c[sup 2]) is obtained at 95% confidence level with (without) background subtraction. Status of searches for other new particles that may arise from new phenomena beyond the standard model is summarized.
Date: September 1, 1993
Creator: Bhat, P.C.
Partner: UNT Libraries Government Documents Department

Tau physics at p[bar p] colliders

Description: Tau detection techniques in hadron colliders are discussed together with the measurements and searches performed so far. We also underline the importance tau physics has in present and future collider experiments.
Date: January 1, 1993
Creator: Konigsberg, J. (Harvard Univ., Cambridge, MA (United States). High Energy Physics Lab.)
Partner: UNT Libraries Government Documents Department

e[sup [plus]]e[sup [minus]] linear colliders and new particle searches

Description: We discuss future e[sup +]e[sup [minus]] linear colliders and new particle searches that can be done with them. In the discussion of new particle searches we examine the following topics: searches for gauge boson structure, searches for a strongly interacting Higgs sector, top quark studies, Higgs searches, supersymmetric particle searches and measurements of soft supersymmetry breaking parameters.
Date: January 1, 1993
Creator: Barklow, T.L.
Partner: UNT Libraries Government Documents Department

Strange meson spectroscopy in K[omega] and K[phi] at 11 GeV/c and Cherenkov ring imaging at SLD

Description: This thesis consists of two independent parts; development of Cherenkov Ring Imaging Detector (CRID) system and analysis of high-statistics data of strange meson reactions from the LASS spectrometer. Part 1: The CRID system is devoted to charged particle identification in the SLAC Large Detector (SLD) to study e[sup +]e[sup [minus]] collisions at [radical]s = m[sub Z[sup 0]]. By measuring the angles of emission of the Cherenkov photons inside liquid and gaseous radiators, [pi]/K/p separation will be achieved up to [approximately]30 GeV/c. The signals from CRID are read in three coordinates, one of which is measured by charge-division technique. To obtain a [approximately]1% spatial resolution in the charge-division, low-noise CRID preamplifier prototypes were developed and tested resulting in <1000 electrons noise for an average photoelectron signal with 2 [times] 10[sup 5] gain. To help ensure the long-term stability of CRID operation at high efficiency, a comprehensive monitoring and control system was developed. Part 2: Results from the partial wave analysis of strange meson final states in the reactions K[sup [minus]]p [yields] K[sup [minus]][omega]p and K[sup [minus]]p [yields] [bar K][sup 0][phi]n are presented. The analyses are based on data from a 4.1 event/nb exposure of the LASS spectrometer in K[sup [minus]]p interactions at 11 GeV/c. The data sample of K[sup [minus]][omega]p final state contains [approximately]10[sup 5] events. From the partial wave analysis, resonance structures of J[sup P] = 2[sup [minus]], 3[sup [minus]] and 2[sup +] amplitudes are observed in the K[omega] system. The analysis of 2[sup [minus]] amplitudes provides an evidence for two strange meson states in the mass region around 1.75 GeV/c[sup 2]. The appropriate branching fractions are calculated and compared with the SU(3) predictions. The partial wave analysis of [bar K][sup 0][phi] system favors J[sup P] = 1[sup [minus]] and 2[sup +] states in the 1.9--2.0 GeV/c[sup 2] region.
Date: January 1, 1993
Creator: Kwon, Youngjoon.
Partner: UNT Libraries Government Documents Department

A search for the top quark decaying to charged Higgs in p{bar p} collisions at {radical}s = 1.8 TeV

Description: We present results of a search for the top quark decaying to a charged. Higgs boson (H) in p{bar p} collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron. Using 4.1 pb{sup {minus}1} of data collected during the 1988--1989 CDF run, we have searched for evidence of t{bar t} production assuming that t{r_arrow} Hb and H{r_arrow} {tau}{nu}{sub {tau}}. We find no evidence for this decay and are able to exclude regions in the (m{sub t}, m{sub H}) plane for different Br(H{r_arrow} {tau}{nu}{sub {tau}}). We also interpret these results for the two Higgs doublet(THD) model.
Date: August 1, 1993
Creator: Collaboration, CDF
Partner: UNT Libraries Government Documents Department

Research on elementary particle physics, Task P: Studies in theory and phenomenology of elementary physics. Annual progress report, November 1, 1992--October 31, 1992: Part 1

Description: Continued progress has been made in isolating the variables needed to completely specify a quark or gluon jet, independent of the process in which it is created. We have evidence of a slow, but statistically significant, dependence on the sub-energy of the hard process in which the jet arises. Once this is taken into account, jets from e{sup +}e{sup {minus}} are consistent with those created in p{bar p}. Neural network jet identification studies win be based on this expanded set of variables. Work on the new type of Dirac equation for a relativistic oscillator was presented at the International Conference on High Energy Physics in Dallas, and will be published in the Proceedings of the Conference. Theoretical studies involving jet signals for theoretically predicted (but as yet undiscovered) particles are underway.
Date: May 1, 1993
Creator: Holloway, L. E. & O`Halloran, T. A.
Partner: UNT Libraries Government Documents Department

Searches for strangelets and other exotics at the AGS

Description: This article describes some experiments either completed, in progress or planned at the Brookhaven National Laboratory AGS. In particular, the experiments described are searches for exotic forms of matter. The existence of such matter could provide a clear signature for the deconfinement or rearrangement of quarks outside the bounds of normal baryons.
Date: January 1, 1993
Creator: Pile, P.H.
Partner: UNT Libraries Government Documents Department

e{sup {plus}}e{sup {minus}} linear colliders and new particle searches

Description: We discuss future e{sup +}e{sup {minus}} linear colliders and new particle searches that can be done with them. In the discussion of new particle searches we examine the following topics: searches for gauge boson structure, searches for a strongly interacting Higgs sector, top quark studies, Higgs searches, supersymmetric particle searches and measurements of soft supersymmetry breaking parameters.
Date: January 1, 1993
Creator: Barklow, T. L.
Partner: UNT Libraries Government Documents Department

SDC tracking capabilities for B physics

Description: The b{bar b} production cross section is estimated to be 1 mb at {radical}s = 40 TeV, implying 10{sup 12} produced b{bar b} pairs at an SSC luminosity of 10{sup 32}cm{sup {minus}2}sec{sup {minus}1} (.1 {times} design). SDC has the potential to exploit this high rate to explore a-number of B physics topics, in particular, CP violation in the neutral B meson. This note describes the SDC particle tracking design and its predicted performance parameters relevant to B physics.
Date: June 1, 1993
Creator: Coupal, D. P.
Partner: UNT Libraries Government Documents Department

A measurement of the ({tau}) polarization at the Z resonance with the DELPHI detector at LEP

Description: The polarization of {tau} leptons produced in the reaction e{sup +}e{sup {minus}} {yields} {tau}{sup +}{tau}{sup {minus}} near the peak of the Z{degree} resonance has been measured using a sample of 24904 {tau}{sup +}{tau}{sup {minus}} events, with an estimated background of 1.5%. We have selected 4562 {tau} {yields} e{nu}{bar {nu}} 2218 {tau} {yields} {pi}{nu} and 5133 {tau} {yields} {rho}{nu} candidates. The mean value obtained is P{sub {tau}} = {minus}0.176 {plus_minus} 0.029. This corresponds to a ratio of the neutral current vector to the axial-vector coupling constants of the {tau} lepton of g{sub V}{sup {tau}}/g{sub A}{sup {tau}} = 0.088 {plus_minus} 0.014. This leads to a value of the electroweak mixing angle of sin{sup 2}{theta}{sub W} = 0.2280 {plus_minus} 0.0036. This result is in good agreement with previous measurements of the weak mixing angle from the study of the Z{degree} lineshape and the forward-backward asymmetries in the processes Z{degree} {yields} l{sup +}l{sup {minus}} and Z{degree} {yields} q{bar q}.
Date: July 1, 1993
Creator: Wong Chan, A.
Partner: UNT Libraries Government Documents Department

Measurement of tau lepton branching fractions

Description: We present {tau}{sup {minus}} lepton branching fraction measurements based on data from the TPC/Two-Gamma detector at PEP. Using a sample of{tau}{sup {minus}} {yields} {nu}{sub {tau}}K{sup {minus}}{pi}{sup +}{pi}{sup {minus}} events, we examine the resonance structure of the K{sup {minus}}{pi}{sup +}{pi}{sup {minus}} system and obtain the first measurements of branching fractions for {tau}{sup {minus}} {yields} {nu}{sub {tau}}K{sub 1}{sup {minus}}(1270) and {tau}{sup {minus}} {yields} {nu}{sub {tau}}K{sub 1}{sup {minus}}(1400). We also describe a complete set of branching fraction measurements in which all the decays of the {tau}{sup {minus}} lepton are separated into classes defined by the identities of the charged particles and an estimate of the number of neutrals. This is the first such global measurement with decay classes defined by the four possible charged particle species, e, {mu}, {pi}, and K.
Date: September 30, 1993
Creator: Nicol, N. A.
Partner: UNT Libraries Government Documents Department

A measurement of R{sub b} = {Gamma}(Z{sup 0} {yields} b{anti b})/{Gamma}(Z{sup 0} {yields} hadrons) at SLD

Description: A measurement of the ratio R{sub b} = {Gamma}(Z{sup 0} {yields} b{anti b})/{Gamma}(Z{sup 0} {yields} hadrons) is reported. This measurement is made using the CCD-based vertex detector of the SLD detector at the SLAC Linear Collider. Efficient tagging of the b{anti b} events is performed with an impact parameter technique that takes advantage of the small and stable interaction point of the SLC and all charged tracks in Z{sup 0} decays. In a sample of 27K Z{sup 0} events collected in 1992 & 1993, a value R{sub b} = 0.235 {+-} 0.006 {+-} 0.018 is obtained.
Date: December 1, 1993
Creator: Neal, H. A. Jr. & Collaboration, SLD
Partner: UNT Libraries Government Documents Department

Strange meson spectroscopy in K{omega} and K{phi} at 11 GeV/c and Cherenkov ring imaging at SLD

Description: This thesis consists of two independent parts; development of Cherenkov Ring Imaging Detector (CRID) system and analysis of high-statistics data of strange meson reactions from the LASS spectrometer. Part 1: The CRID system is devoted to charged particle identification in the SLAC Large Detector (SLD) to study e{sup +}e{sup {minus}} collisions at {radical}s = m{sub Z{sup 0}}. By measuring the angles of emission of the Cherenkov photons inside liquid and gaseous radiators, {pi}/K/p separation will be achieved up to {approximately}30 GeV/c. The signals from CRID are read in three coordinates, one of which is measured by charge-division technique. To obtain a {approximately}1% spatial resolution in the charge-division, low-noise CRID preamplifier prototypes were developed and tested resulting in <1000 electrons noise for an average photoelectron signal with 2 {times} 10{sup 5} gain. To help ensure the long-term stability of CRID operation at high efficiency, a comprehensive monitoring and control system was developed. Part 2: Results from the partial wave analysis of strange meson final states in the reactions K{sup {minus}}p {yields} K{sup {minus}}{omega}p and K{sup {minus}}p {yields} {bar K}{sup 0}{phi}n are presented. The analyses are based on data from a 4.1 event/nb exposure of the LASS spectrometer in K{sup {minus}}p interactions at 11 GeV/c. The data sample of K{sup {minus}}{omega}p final state contains {approximately}10{sup 5} events. From the partial wave analysis, resonance structures of J{sup P} = 2{sup {minus}}, 3{sup {minus}} and 2{sup +} amplitudes are observed in the K{omega} system. The analysis of 2{sup {minus}} amplitudes provides an evidence for two strange meson states in the mass region around 1.75 GeV/c{sup 2}. The appropriate branching fractions are calculated and compared with the SU(3) predictions. The partial wave analysis of {bar K}{sup 0}{phi} system favors J{sup P} = 1{sup {minus}} and 2{sup +} states in the 1.9--2.0 GeV/c{sup 2} region.
Date: January 1, 1993
Creator: Kwon, Youngjoon
Partner: UNT Libraries Government Documents Department

Search for the top quark in the single lepton + jets channel at D0

Description: We have searched for standard model top quark pair production at {radical}s = 1.8 TeV. We present preliminary results of searches in the single lepton decay modes (i.e. where one top quark decays semileptonically to an electron or a muon and the other top quark decayed hadronically). We do not find evidence for top quark production in these decay channels. By combining this negative result with our negative result from the dilepton decay channels, we obtain a 95% confidence level upper limit on the top quark production cross section for top masses between 80 and 140 GeV/c{sup 2}. By comparing this cross section upper limit curve with a theoretical production cross section we obtain a lower limit on the top quark mass of 124 GeV/c{sup 2}
Date: November 1, 1993
Creator: Greenlee, H. B. & collaboration, D0
Partner: UNT Libraries Government Documents Department

Search for the top quark in the electron-electron and electron-muon channels at D0

Description: We discuss preliminary results of a search for top quarks using their decays in two di-lepton, with the D0 detector at Fermilab. The present analysis has been optimized to search for a top with mass near 100{sub c{sup 2}}/{sup GeV}, consistent with published limits. In the event sample corresponding to an integrated luminosity of 15pb{sup {minus}1} we observe two events passing all selection cuts. The number of events observed is consistent with the expected number of background events. Consequently, we do not claim the observation of a top decay in the present event sample. We note however, that the kinematic properties of one of the events appear to be far removed from known backgrounds. We discuss the event and show results of the mass likelihood analysis when applied to this event.
Date: December 3, 1993
Creator: Fatyga, M. & Collaboration, The D0
Partner: UNT Libraries Government Documents Department

Search for the H dibaryon by {Xi}{sup {minus}} capture on the deuteron

Description: The present status of the H-dibaryon search experiment at Brookhaven (E813) using the formation reaction through {Xi}{sup {minus}} atomic operation on the deuteron, ({Xi}{sup {minus}}, d){sub atom} {yields} H n, is reported with emphasis placed on the analysis of the data collected with the 1992 slow extracted proton beam run.
Date: December 31, 1993
Creator: Iijima, Toru & Collaboration, E813
Partner: UNT Libraries Government Documents Department