926 research outputs found
Real-Time Data Processing in the Muon System of the D0 Detector
This paper presents a real-time application of the 16-bit fixed point Digital
Signal Processors (DSPs), in the Muon System of the D0 detector located at the
Fermilab Tevatron, presently the world's highest-energy hadron collider. As
part of the Upgrade for a run beginning in the year 2000, the system is
required to process data at an input event rate of 10 KHz without incurring
significant deadtime in readout. The ADSP21csp01 processor has high I/O
bandwidth, single cycle instruction execution and fast task switching support
to provide efficient multisignal processing. The processor's internal memory
consists of 4K words of Program Memory and 4K words of Data Memory. In addition
there is an external memory of 32K words for general event buffering and 16K
words of Dual Port Memory for input data queuing. This DSP fulfills the
requirement of the Muon subdetector systems for data readout. All error
handling, buffering, formatting and transferring of the data to the various
trigger levels of the data acquisition system is done in software. The
algorithms developed for the system complete these tasks in about 20
microseconds per event.Comment: 4 pages, Presented and published at the 11th IEEE NPSS Real Time
Conference, held at Santa Fe, New Mexico, USA, from June 14-18, 199
Journal Staff
We present the first measurements of the differential cross section d sigma/dp(T)(gamma) for the production of an isolated photon in association with at least two b-quark jets. The measurements consider photons with rapidities vertical bar y(gamma)vertical bar < 1.0 and transverse momenta 30 < p(T)(gamma) < 200 GeV. The b-quark jets are required to have p(T)(jet) > 15 GeVand vertical bar y(jet)vertical bar < 1.5. The ratio of differential production cross sections for gamma + 2 b-jets to gamma + b-jet as a function of p(T)(gamma) is also presented. The results are based on the proton-antiproton collision data at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The measured cross sections and their ratios are compared to the next- to- leading order perturbative QCD calculations as well as predictions based on the k(T)- factorization approach and those from the sherpa and pythia Monte Carlo event generators
Precise measurement of the top quark mass in the dilepton channel at D0
We measure the top quark mass (mt) in ppbar collisions at a center of mass
energy of 1.96 TeV using dilepton ttbar->W+bW-bbar->l+nubl-nubarbbar events,
where l denotes an electron, a muon, or a tau that decays leptonically. The
data correspond to an integrated luminosity of 5.4 fb-1 collected with the D0
detector at the Fermilab Tevatron Collider. We obtain mt = 174.0 +- 1.8(stat)
+- 2.4(syst) GeV, which is in agreement with the current world average mt =
173.3 +- 1.1 GeV. This is currently the most precise measurement of mt in the
dilepton channel.Comment: 7 pages, 4 figure
A search for charged massive long-lived particles
We report on a search for charged massive long-lived particles (CMLLPs),
based on 5.2 fb of integrated luminosity collected with the D0 detector
at the Fermilab Tevatron collider. We search for events in which one
or more particles are reconstructed as muons but have speed and ionization
energy loss inconsistent with muons produced in beam collisions.
CMLLPs are predicted in several theories of physics beyond the standard model.
We exclude pair-produced long-lived gaugino-like charginos below 267 GeV and
higgsino-like charginos below 217 GeV at 95% C.L., as well as long-lived scalar
top quarks with mass below 285 GeV.Comment: submitted to Phys. Rev. Letter
Search for Decay
We have searched for the charmless hadronic decay of B0 mesons into two
neutral pions. Using 9.13fb^-1 taken at the Upsilon(4S) with the CLEO detector,
we obtain an improved upper limit for the branching fraction BR(B0-->pi0pi0) <
5.7*10^-6 at the 90% confidence level.Comment: pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Search for first generation leptoquark pair production in the electron + missing energy + jets final state
We present a search for the pair production of first generation scalar
leptoquarks (LQ) in data corresponding to an integrated luminosity of 5.4
fb collected with the D0 detector at the Fermilab Tevatron Collider in
ppbar collisions at TeV. In the channel , where q, q' are u or d quarks, no significant excess
of data over background is observed, and we set a 95% C.L. lower limit of 326
GeV on the leptoquark mass, assuming equal probabilities of leptoquark decays
to eq and .Comment: 7 pages, 6 figures, submitted to PRD-R
Direct measurement of the mass difference between top and antitop quarks
We present a direct measurement of the mass difference between top and
antitop quarks (dm) in lepton+jets top-antitop final states using the "matrix
element" method. The purity of the lepton+jets sample is enhanced for
top-antitop events by identifying at least one of the jet as originating from a
b quark. The analyzed data correspond to 3.6 fb-1 of proton-antiproton
collisions at 1.96 TeV acquired by D0 in Run II of the Fermilab Tevatron
Collider. The combination of the e+jets and mu+jets channels yields dm = 0.8
+/- 1.8 (stat) +/- 0.5 (syst) GeV, which is in agreement with the standard
model expectation of no mass difference.Comment: submitted to Phys. Rev.
Zgamma production and limits on anomalous ZZgamma and Zgammagamma couplings in ppbar collisions at sqrt(s)=1.96 TeV
We present a measurement of ppbar->Zgamma->ll+gamma (l = e, mu) production
with a data sample corresponding to an integrated luminosity of 6.2 fb^{-1}
collected by the D0 detector at the Fermilab Tevatron ppbar Collider. The
results of the electron and muon channels are combined, and we measure the
total production cross section and the differential cross section
dsigma/dp_T^gamma, where p_T^gamma is the momentum of the photon in the plane
transverse to the beamline. The results obtained are consistent with the
standard model predictions from next-to-leading order calculations. We use the
transverse momentum spectrum of the photon to place limits on anomalous ZZgamma
and Zgammagamma couplings
Search for a Narrow ttbar Resonance in ppbar Collisions at sqrt{s}=1.96 TeV
We report a search for a narrow ttbar resonance that decays into a
lepton+jets final state based on an integrated luminosity of 5.3/fb of
proton-antiproton collisions at sqrt{s}=1.96 TeV collected by the D0
Collaboration at the Fermilab Tevatron Collider. We set upper limits on the
production cross section of such a resonance multiplied by its branching
fraction to ttbar which we compare to predictions for a leptophobic topcolor Z'
boson. We exclude such a resonance at the 95% confidence level for masses below
835 GeV.Comment: 7 pages, 3 figures, submitted to Physical Review Letter
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