211 research outputs found
Radar altimetry systems cost analysis
This report discusses the application and cost of two types of altimeter systems (spaceborne (satellite and shuttle) and airborne) to twelve user requirements. The overall design of the systems defined to meet these requirements is predicated on an unconstrained altimetry technology; that is, any level of altimeter or supporting equipment performance is possible
The scaler magnetic intensity at 1100 kilometers in middle and low latitudes
Satellite borne magnetometer for measuring scalar magnetic intensities in middle and low latitudes at 1100 km altitud
An evaluation of geomagnetic harmonic series for 1100 kilometers altitude
Geomagnetic harmonic series evaluation for 1100 kilometers altitude using satellite observation
Spin Correlation in tt-bar Production from pp-bar Collisions at sqrt(s)=1.8 TeV
The D0 collaboration has performed a study of spin correlation in tt-bar
production for the process tt-bar to bb-bar W^+W^-, where the W bosons decay to
e-nu or mu-nu. A sample of six events was collected during an exposure of the
D0 detector to an integrated luminosity of approximately 125 pb^-1 of
sqrt{s}=1.8 TeV pp-bar collisions. The standard model (SM) predicts that the
short lifetime of the top quark ensures the transmission of any spin
information at production to the tt-bar decay products.
The degree of spin correlation is characterized by a correlation coefficient
k. We find that k>-0.25 at the 68% confidence level, in agreement with the SM
prediction of k=0.88.Comment: Submitted to PRL, Added references, minor changes to tex
Search for Squarks and Gluinos in Events Containing Jets and a Large Imbalance in Transverse Energy
Using data corresponding to an integrated luminosity of 79 pb-1, D0 has
searched for events containing multiple jets and large missing transverse
energy in pbar-p collisions at sqrt(s)=1.8 TeV at the Fermilab Tevatron
collider. Observing no significant excess beyond what is expected from the
standard model, we set limits on the masses of squarks and gluinos and on the
model parameters m_0 and m_1/2, in the framework of the minimal low-energy
supergravity models of supersymmetry. For tan(beta) = 2 and A_0 = 0, with mu <
0, we exclude all models with m_squark < 250 GeV/c^2. For models with equal
squark and gluino masses, we exclude m < 260 GeV/c^2.Comment: 10 pages, 3 figures, Submitted to PRL, Fixed typo on page bottom of
p. 6 (QCD multijet background is 35.4 events
Search for Charged Higgs Bosons in Decays of Top Quark Pairs
We present a search for charged Higgs bosons in decays of pair-produced top
quarks using 109.2 +- 5.8 pb^-1 of data recorded from ppbar collisions at
sqrt{s} = 1.8 TeV by the D0 detector during 1992-96 at the Fermilab Tevatron.
No evidence is found for charged Higgs production, and most parts of the
[m(H+),tan(beta)] parameter space where the decay t -> bH+ has a branching
fraction close to or larger than that for t -> bW+ are excluded at 95%
confidence level. Assuming m(t) = 175 GeV and sigma(ppbar -> ttbar) = 5.5 pb,
for m(H+) = 60 GeV, we exclude tan(beta) 40.9.Comment: 11 pages, 3 figures, submitted to PR
Direct Measurement of the Top Quark Mass at D0
We determine the top quark mass m_t using t-tbar pairs produced in the D0
detector by \sqrt{s} = 1.8 TeV p-pbar collisions in a 125 pb^-1 exposure at the
Fermilab Tevatron. We make a two constraint fit to m_t in t-tbar -> b W^+bbar
W^- final states with one W boson decaying to q-qbar and the other to e-nu or
mu-nu. Likelihood fits to the data yield m_t(l+jets) = 173.3 +- 5.6 (stat) +-
5.5 (syst) GeV/c^2. When this result is combined with an analysis of events in
which both W bosons decay into leptons, we obtain m_t = 172.1 +- 5.2 (stat) +-
4.9 (syst) GeV/c^2. An alternate analysis, using three constraint fits to fixed
top quark masses, gives m_t(l+jets) = 176.0 +- 7.9 (stat) +- 4.8 (syst)
GeV/C^2, consistent with the above result. Studies of kinematic distributions
of the top quark candidates are also presented.Comment: 43 pages, 53 figures, 33 tables. RevTeX. Submitted to Phys. Rev.
A measurement of the W boson mass using large rapidity electrons
We present a measurement of the W boson mass using data collected by the D0
experiment at the Fermilab Tevatron during 1994--1995. We identify W bosons by
their decays to e-nu final states where the electron is detected in a forward
calorimeter. We extract the W boson mass, Mw, by fitting the transverse mass
and transverse electron and neutrino momentum spectra from a sample of 11,089 W
-> e nu decay candidates. We use a sample of 1,687 dielectron events, mostly
due to Z -> ee decays, to constrain our model of the detector response. Using
the forward calorimeter data, we measure Mw = 80.691 +- 0.227 GeV. Combining
the forward calorimeter measurements with our previously published central
calorimeter results, we obtain Mw = 80.482 +- 0.091 GeV
Measurement of the Boson Mass
A measurement of the mass of the boson is presented based on a sample of
5982 decays observed in collisions at
= 1.8~TeV with the D\O\ detector during the 1992--1993 run. From a
fit to the transverse mass spectrum, combined with measurements of the
boson mass, the boson mass is measured to be .Comment: 12 pages, LaTex, style Revtex, including 3 postscript figures
(submitted to PRL
Measurement of the Top Quark Pair Production Cross Section in pbar-p Collisions Using Multijet Final States
We have studied tbar-t production using multijet final states in pbar-p
collisions at a center-of-mass energy of 1.8 TeV, with an integrated luminosity
of 110.3 pb(-1). Each of the top quarks with these final states decays
exclusively to a bottom quark and a W boson, with the W bosons decaying into
quark-antiquark pairs. The analysis has been optimized using neural networks to
achieve the smallest expected fractional uncertainty on the tbar-t production
cross section, and yields a cross section of 7.1 +/- 2.8(stat.) +/- 1.5(syst.)
pb, assuming a top quark mass of 172.1 GeV/c^(2). Combining this result with
previous D0 measurements, where one or both of the W bosons decay leptonically,
gives a tbar t production cross section of 5.9 +/- 1.2(stat) +/- 1.1(syst) pb.Comment: 30 pages, 32 figures; no substative change in revisio
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