1,517 Matching Results

Search Results

Advanced search parameters have been applied.

Substructure of High-pT Jets at the LHC

Description: We study high-p{sub T} jets from QCD and from highly-boosted massive particles such as tops, W,Z and Higgs, and argue that infrared-safe observables can help reduce QCD backgrounds. Jets from QCD are characterized by different patterns of energy flow compared to the products of highly-boosted heavy particle decays, and we employ a variety of jet shapes, observables restricted to energy flow within a jet, to explore this difference. Results from Monte Carlo generators and arguments based on perturbation theory support the discriminating power of the shapes we refer to as planar flow and angularities. We emphasize that for massive jets, these and other observables can be analyzed perturbatively.
Date: July 2, 2008
Creator: Almeida, L.G.; Lee, S.J.; Perez, G.; Sterman, G.; Sung, I. & Virzi, J.
Partner: UNT Libraries Government Documents Department

Search for neutral heavy leptons in the NuTeV experiment at Fermilab

Description: Preliminary results are presented from a search for neutral heavy leptons in the NuTeV experiment at Fermilab. The upgraded NuTeV neutrino detector for the 1996-1997 run included an instrumented decay region for the NHL search which, combined with the NuTeV calorimeter, allows detection in several decay modes ({mu}{mu}{nu}, {mu}e{nu}, {mu}{pi}, e{pi}, and ee{nu}). We see no evidence for neutral heavy leptons in our current search in the mass range from 0.3 GeV to 2.0 GeV decaying into final states containing a muon.
Date: December 1, 1998
Creator: Drucker, R.B.
Partner: UNT Libraries Government Documents Department

Rare b decays from the CDF experiment

Description: The high cross-section for the production of b quarks at the Tevatron hadron collider make it an ideal place to search for rare B meson species and very low branching fraction decay modes of the more common B mesons. This paper reports the recent discovery of the Bc meson by the CDF collaboration. It also discusses the observation of rare B meson final states involving {psi}(2S) mesons and searches for ultra-rare decays such as B {yields} {mu}{sup +}{mu}{sup -}
Date: October 1, 1998
Creator: Trischuk, W.
Partner: UNT Libraries Government Documents Department

The Measurement of xi'/xi at Fermilab KTeV-E832

Description: The status of the analysis effort for the 25% data sample taken during the Fermilab '96-'97 fixed target run for {epsilon}'/{epsilon} measurement from KTeV is presented here. Detector performance, data statistics, background subtractions, data and monte-carlo comparison for acceptance corrections, as well as the preliminary results on K{sub L}{yields}{pi}{sup 0}{gamma}{gamma} are described in more detail. Prospects for KTeV 99, in the up coming 6 months '99 fixed target run, are also discussed here.
Date: February 15, 1999
Creator: Hsiung, Yee Bob
Partner: UNT Libraries Government Documents Department

Recent D-Zero results on the top quark

Description: Recent results on top quark physics with the D0 experiment in {anti p}p collisions at {radical}s = 1.8 TeV for an integrated luminosity of 125 pb{sup -1} are reported. The direct measurement of the top quark mass uses single lepton events, giving the result m{sub top} = 173.3 {+-} 5.6(stat) {+-} 6.2(syst) GeV=c{sup 2}. The measurement of the t{anti t} production cross section includes analyses from 8 top decay channels: dilepton (t{anti t} {yields} e{mu}, ee, and {mu}{mu}), electron and neutrino (t{anti t} {yields} e{nu}), and single leptons (t{anti t} {yields} e + jets and t{anti t} {yields} {mu} + jets) with and without b tagging. We measure the t{anti t} production cross section to be 5.5 {+-} 1.8 pb at m{sub top} = 173.3 GeV/c{sup 2}.
Date: July 1, 1997
Creator: Li, Q.
Partner: UNT Libraries Government Documents Department

CP violation in neutral kaon decays

Description: A brief review of the theoretical status of CP violation in decays of neutral kaons is presented. We focus on three important topics: {epsilon}, {epsilon}`/{epsilon} and K{sub L}{yields}{pi}{sup 0}{nu}{anti {nu}}.
Date: May 1, 1997
Creator: Buchalla, G.
Partner: UNT Libraries Government Documents Department

Axions from string decay

Description: We have studied numerically the evolution and decay of axion strings. These global defects decay mainly by axion emission and thus contribute to the cosmological axion energy density. The relative importance of this source relative to misalignment production of axions depends on the spectrum. Radiation spectra for various string loop configurations are presented. They support the contention that the string decay contribution is of the same order of magnitude as the contribution from misalignment.
Date: July 9, 1998
Creator: Hagmann, C., LLNL
Partner: UNT Libraries Government Documents Department

Realizing the potential of quarkonium

Description: I recall the development of quarkonium quantum mechanics after the discovery of {Upsilon}. I emphasize the empirical approach to determining the force between quarks from the properties of c{anti c} and b{anti b} bound states. I review the application of scaling laws, semiclassical methods, theorems and near-theorems, and inverse- scattering techniques. I look forward to the next quarkonium spectroscopy in the B{sub c} system.
Date: July 1, 1997
Creator: Quigg, C.
Partner: UNT Libraries Government Documents Department

Charmonium and charm decays from the Fermilab fixed target program

Description: Recent results on charm decay physics from the Fermilab Fixed Target program will be presented. There have been many physics results within the past year from experiments E687 and E791 and these will be highlighted. Many of these results are related to rare phenomena and searches. These will become even more interesting with the FOCUS experiment dataset of 1 million fully reconstructed charm decays. Preliminary signals from FOCUS as well as from SELEX will be presented together with prospects for the future. Preliminary results from E835 on the {eta}`{sub c} search will also be presented.
Date: May 1, 1998
Creator: Cheung, G.W.K.
Partner: UNT Libraries Government Documents Department

Studies of the top quark at the Tevatron

Description: We report on studies of the top quark, beyond the measurements of its mass and produciton cross section, which have been carried out recently by the CDF and D0 collaborations, based on {approximately}110{+-}6 pb{sup -1} of proton-antiproton collisions at a center-of-mass energy of 1.8 TeV. Each experiment has searched for t{yields}H{sup +}b decays and, from the lack of observable signal, excluded previously unexplored regions of the [M{sub H+},tan{beta}] parameter space. D0 has studied the correlation between the spin states of pair-produced top quarks, and CDF has studied the helicity of the W bosons produced in the decay of top quarks. Within large statistical uncertainties, both measurements agree with predictions of the standard model.
Date: May 28, 1999
Creator: Chakraborty, Dhiman
Partner: UNT Libraries Government Documents Department

Theoretical developments in inclusive B decays

Description: Some recent theoretical work on inclusive B decays relevant for the model independent determination of {vert_bar}V{sub ub}{vert_bar} and {vert_bar}V{sub cb}{vert_bar} is summarized. The theoretical predictions and their reliability for several differential decay distributions in {anti B}{yields}X{sub c,u}e{anti {nu}} and {anti B}{yields}X{sub s}{gamma} are reviewed. These can be used to determine certain important HQET matrix elements. The upsilon expansion and ways of testing it are discussed.
Date: May 17, 1999
Creator: Ligeti, Zoltan
Partner: UNT Libraries Government Documents Department

Present searches for Higgs signatures at the Tevatron

Description: We present results for various searches for signatures of standard and non-standard model Higgs boson decays conducted at the collider detectors CDF and D0 using {approx}100 pb{sup -1} of integrated luminosity each from the Tevatron collider Run 1 (1992-96) at {radical}s=1.8 TeV. No evidence for a Higgs boson decay is found and various limits are set.
Date: August 1, 1997
Creator: Groer, L.
Partner: UNT Libraries Government Documents Department

Top Quark Production and Decay Measurements from CDF

Description: The CDF collaboration is completing a number of studies on the top quark, based on samples collected during Run I of the Tevatron Collider. The production and decay properties of the top quark are being examined in most of the t {anti t} decay channels, and many of these results have recently been published. The study of the top quark has moved beyond measurements of its mass and production cross section, to detailed studies of W polarization in top decays, single top production, branching fractions, the W - t - b coupling, and search for rare decays.
Date: January 1, 1999
Creator: Tollefson, K.
Partner: UNT Libraries Government Documents Department

Supergravity grand unification, proton decay and cosmological constraints

Description: Properties and experimental predictions of a broad class of supergravity grand unified models possessing an SU(5)-type proton decay and R parity are described. Models of this type can be described in terms of four parameters at the Gut scale in addition to those of the Standard Model i.e. m{sub 0} (universal scalar mass), m{sub 1/2} (universal gaugino mass), A{sub 0} (cubic soft breaking parameter) and tan {beta} = <H{sub 2}>/<H{sub 1}>. Thus the 32 SUSY masses can be expressed in terms of m{sub 0}, M{sub 1/2}, A{sub 0} tan {beta} and the as yet unknown t-quark mass M{sub t}. Gut thresholds are examined and a simple model leads to grand unification consistent with p-decay data when 0.114 < {alpha}{sub 3}(M{sub z}) < 0.135, in agreement with current values of {alpha}{sub 3}(M{sub Z}). Proton decay is examined for the superheavy Higgs triplet mass H{sub H3} < 10M{sub G}(M{sub G} {approx_equal} 1.5 {times} 10{sup 16} GeV) and squarks and gluinos lighter than 1 TeV. Throughout most of the parameter space chargino-neutralino scaling relations are predicted to hold: 2m{sub {anti Z}}{sub 1} {congruent} m{sub {anti W}}{sub 1} {congruent} m{sub {anti Z}}{sub 2}, m{sub {anti W}}{sub 1} {approx_equal} (1/4)m{sub {anti g}} (for {mu} > 0) or m{sub {anti W}}{sub 1} {approx_equal} (1/3)m{sub {anti g}} (for {mu} < 0), while m{sub {anti W}}{sub 2} {congruent} m{sub {anti Z}}{sub 3} {congruent} m{sub {anti Z}}{sub 4} {much_gt} m{sub {anti Z}}{sub 1}. Future proton decay experiments combined with LEP2 lead to further predictions, e.g. for the entire parameter space either proton decay should be seen at these or the {anti W}{sub 1} seen at LEP2. Relic density constraints on the {anti Z}{sub 1} further constrain the parameter space e.g. so that m{sub t} < 165 GeV, M{sub h} < 105 GeV, m{sub {anti W}}{sub 1} < 100 GeV ...
Date: May 1, 1995
Creator: Arnowitt, R. & Nath, P.
Partner: UNT Libraries Government Documents Department

B Decays as a probe of spontaneous cp-violation in SUSY models

Description: We consider phenomenological implications of susy models with spontaneously broken CP-symmetry. In particular, we analyze CP-asymmetries in B decays and find that the predictions of these models are vastly different from those of the SM. These features are common to NMSSM-like models with an arbitrary number of sterile superfields and the MSSM with broken R-parity.
Date: July 8, 1999
Creator: Lebedev, Oleg
Partner: UNT Libraries Government Documents Department

Tau physics at CDF

Description: We discuss tau identification techniques at hadron colliders, and present the measurements and the searches performed so far. We report on the first evidence of t{anti t} production in the channel containing one hadronically decaying {tau} lepton. We also present a search for the charged Higgs boson in the tau decay channel, as well as for the leptoquark family containing tau leptons. In addition, we underline the importance of tau physics both at present and future collider experiments.
Date: August 1, 1997
Creator: Gallinaro, M.
Partner: UNT Libraries Government Documents Department

Search for leptoquarks at CDF

Description: We present the result of direct leptoquark searches based on 110 pb{sup -1} of integrated luminosity collected by the Collider Detector at Fermilab during the 1992-93 and 1994-95 Tevatron runs at {radical}s = 1.8 TeV. We present upper limits on the production cross sections as a function of the leptoquark mass. Using the NLO calculation of the leptoquark-pair production cross sections we extract lower-mass limits for 1{sup st}, 2{sup nd}, and 3{sup d} generation leptoquarks. We also present the result of an indirect search for Pati-Salam leptoquarks via exclusive e{mu} decay modes of B{sup 0}{sub s} and B{sup 0}{sub d}
Date: July 1, 1997
Creator: Kambara, H. S.
Partner: UNT Libraries Government Documents Department

Decay rates of various bottomonium systems

Description: Using the Bodwin-Braaten-Lepage factorization theorem in heavy quarkonium decay and production processes, the authors calculated matrix elements associated with S- and P-wave bottomonium decays via lattice QCD simulation methods. In this work, they report preliminary results on the operator matching between the lattice expression and the continuum expression at one loop level. Phenomenological implications are discussed using these preliminary {ovr MS} matrix elements.
Date: December 31, 1995
Creator: Kim, S.
Partner: UNT Libraries Government Documents Department

Absolute Decay Rate from K<sub>2</sub><sup>0</sup>→π<sup>+</sup> + π<sup>-</sup> + π<sup>0</sup> and the barDELTA I over→bar = 1/2 Rule

Description: In this letter the author describes a measurement of the absolute decay rate {Gamma}{sub 2}({+-}0) {approx_equal} {Gamma}(K{sub 2}{sup 0} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup 0}). The result is based on 16 events of the type {pi}{sup -} p {yields} {Lambda}K{sup 0} followed by {Lambda} {yields} p{pi}{sup -} and K{sub 2}{sup 0} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup 0}, and 2608 double-vec events {pi}{sup -} p {yields} {Lambda}K{sup 0} with {Lambda} {yields} p{pi}{sup -} and K{sub 1}{sup 0} {yields} {pi}{sup +}{pi}{sup -}.
Date: February 4, 1964
Creator: Stern, Donald; Binford, Thomas O.; Lind, V. Gordon; Anderson, Jared A.; Crawford, Jr, Frank S. & Golden, Robert L.
Partner: UNT Libraries Government Documents Department

DECAYS OF THE Tz = -2 NUCLEI 20Mg, 24Si AND 36Ca

Description: Beta-delayed protons have been observed from the decays of the mass separated T{sub z} = -2 nuclides {sup 20}Mg, {sup 24}Si, and {sup 36}Ca. From these proton spectra the mass excesses of the lowest T = 2 states in the T{sub z} = -1 nuclei {sup 20}Na, {sup 24}Al, and {sup 36}K are determined to be 13420 {+-} 50 keV ({sup 20}Na), 5903 {+-} 9 keV ({sup 24}Al), and - 13168 {+-} 22 keV ({sup 36}K). The complete A = 20, 24, and 36 isospin quintets have all their members bound against isospin allowed particle-decay modes, providing a stringent test of the isobaric multiplet mass equation. Good agreement is observed for all these quintets using only the quadratic form of this equation. Radioactivity {sup 20}Mg, {sup 24}Si, {sup 36}Ca (mass separated); measured {beta}-delayed protons; deduced T{sub 1/2} and proton branching; derived mass excesses of the lowest 0{sup +}, T = 2 states in {sup 20}Na, {sup 24}Al, and {sup 36}K; deduced coefficients of the isobaric multiplet mass equation.
Date: June 1, 1980
Creator: Aysto, J.; Cable, M.D.; Parry, R.F.; Wouters, J.M.; Moltz, D.M. & Cerny, J.
Partner: UNT Libraries Government Documents Department