728 research outputs found
Probabilistic Clustering of Time-Evolving Distance Data
We present a novel probabilistic clustering model for objects that are
represented via pairwise distances and observed at different time points. The
proposed method utilizes the information given by adjacent time points to find
the underlying cluster structure and obtain a smooth cluster evolution. This
approach allows the number of objects and clusters to differ at every time
point, and no identification on the identities of the objects is needed.
Further, the model does not require the number of clusters being specified in
advance -- they are instead determined automatically using a Dirichlet process
prior. We validate our model on synthetic data showing that the proposed method
is more accurate than state-of-the-art clustering methods. Finally, we use our
dynamic clustering model to analyze and illustrate the evolution of brain
cancer patients over time
Reconstruction of cell population dynamics using CFSE
Background: Quantifying cell division and death is central to many studies in the biological
sciences. The fluorescent dye CFSE allows the tracking of cell division in vitro and in vivo and
provides a rich source of information with which to test models of cell kinetics. Cell division and
death have a stochastic component at the single-cell level, and the probabilities of these occurring
in any given time interval may also undergo systematic variation at a population level. This gives rise
to heterogeneity in proliferating cell populations. Branching processes provide a natural means of
describing this behaviour.
Results: We present a likelihood-based method for estimating the parameters of branching
process models of cell kinetics using CFSE-labeling experiments, and demonstrate its validity using
synthetic and experimental datasets. Performing inference and model comparison with real CFSE
data presents some statistical problems and we suggest methods of dealing with them.
Conclusion: The approach we describe here can be used to recover the (potentially variable)
division and death rates of any cell population for which division tracking information is available
Measurement of the top quark mass using the matrix element technique in dilepton final states
We present a measurement of the top quark mass in pp¯ collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. The data were collected by the D0 experiment corresponding to an integrated luminosity of 9.7 fb−1. The matrix element technique is applied to tt¯ events in the final state containing leptons (electrons or muons) with high transverse momenta and at least two jets. The calibration of the jet energy scale determined in the lepton+jets final state of tt¯ decays is applied to jet energies. This correction provides a substantial reduction in systematic uncertainties. We obtain a top quark mass of mt=173.93±1.84 GeV
Measurement of the B0_s semileptonic branching ratio to an orbitally excited D_s** state, Br(B0_s -> Ds1(2536) mu nu)
In a data sample of approximately 1.3 fb-1 collected with the D0 detector
between 2002 and 2006, the orbitally excited charm state D_s1(2536) has been
observed with a measured mass of 2535.7 +/- 0.6 (stat) +/- 0.5 (syst) MeV via
the decay mode B0_s -> D_s1(2536) mu nu X. A first measurement is made of the
branching ratio product Br(b(bar) -> D_s1(2536) mu nu X).Br(D_s1(2536)->D*
K0_S). Assuming that D_s1(2536) production in semileptonic decay is entirely
from B0_s, an extraction of the semileptonic branching ratio Br(B0_s ->
D_s1(2536) mu nu X) is made.Comment: 7 pages, 2 figures, LaTeX, version with minor changes as accepted by
Phys. Rev. Let
Simultaneous measurement of the ratio B(t->Wb)/B(t->Wq) and the top quark pair production cross section with the D0 detector at sqrt(s)=1.96 TeV
We present the first simultaneous measurement of the ratio of branching
fractions, R=B(t->Wb)/B(t->Wq), with q being a d, s, or b quark, and the top
quark pair production cross section sigma_ttbar in the lepton plus jets channel
using 0.9 fb-1 of ppbar collision data at sqrt(s)=1.96 TeV collected with the
D0 detector. We extract R and sigma_ttbar by analyzing samples of events with
0, 1 and >= 2 identified b jets. We measure R = 0.97 +0.09-0.08 (stat+syst) and
sigma_ttbar = 8.18 +0.90-0.84 (stat+syst)} +/-0.50 (lumi) pb, in agreement with
the standard model prediction.Comment: submitted to Phys.Rev.Letter
Search for R-parity violating supersymmetry via the LLE couplings lambda_{121}, lambda_{122} or lambda_{133} in ppbar collisions at sqrt(s)=1.96 TeV
A search for gaugino pair production with a trilepton signature in the
framework of R-parity violating supersymmetry via the couplings lambda_121,
lambda_122, or lambda_133 is presented. The data, corresponding to an
integrated luminosity of L~360/pb, were collected from April 2002 to August
2004 with the D0 detector at the Fermilab Tevatron Collider, at a
center-of-mass energy of sqrt(s)=1.96 TeV. This analysis considers final states
with three charged leptons with the flavor combinations eel, mumul, and eetau
(l=e or mu). No evidence for supersymmetry is found and limits at the 95%
confidence level are set on the gaugino pair production cross section and lower
bounds on the masses of the lightest neutralino and chargino are derived in two
supersymmetric models.Comment: 9 pages, 4 figures (fig2 includes 3 subfigures
Search for W' bosons decaying to an electron and a neutrino with the D0 detector
This Letter describes the search for a new heavy charged gauge boson W'
decaying into an electron and a neutrino. The data were collected with the D0
detector at the Fermilab Tevatron proton-antiproton Collider at a
center-of-mass energy of 1.96 TeV, and correspond to an integrated luminosity
of about 1 inverse femtobarn. Lacking any significant excess in the data in
comparison with known processes, an upper limit is set on the production cross
section times branching fraction, and a W' boson with mass below 1.00 TeV can
be excluded at the 95% C.L., assuming standard-model-like couplings to
fermions. This result significantly improves upon previous limits, and is the
most stringent to date.Comment: submitted to Phys. Rev. Let
Measurement of the ratios of the Z/G* + >= n jet production cross sections to the total inclusive Z/G* cross section in ppbar collisions at sqrt(s) = 1.96 TeV
We present a study of events with Z bosons and jets produced at the Fermilab
Tevatron Collider in ppbar collisions at a center of mass energy of 1.96 TeV.
The data sample consists of nearly 14,000 Z/G* -> e+e- candidates corresponding
to the integrated luminosity of 0.4 fb-1 collected using the D0 detector.
Ratios of the Z/G* + >= n jet cross sections to the total inclusive Z/G* cross
section have been measured for n = 1 to 4 jet events. Our measurements are
found to be in good agreement with a next-to-leading order QCD calculation and
with a tree-level QCD prediction with parton shower simulation and
hadronization.Comment: 7 pages, 2 figures, slightly modified, submitted to Phys. Lett.
Measurement of the Lifetime Using Semileptonic Decays
We report a measurement of the lifetime in the semileptonic decay
channel (and its charge conjugate), using
approximately 0.4 fb of data collected with the D0 detector during 2002
-- 2004. We have reconstructed 5176 signal events, where the
is identified via the decay , followed by . Using these events, we have measured the lifetime to be
. This is the most precise measurement of the lifetime to date.Comment: To appear in Phys. Rev. Lett., 7 pages, 2 figure
Search for Neutral Higgs Bosons Decaying to Tau Pairs in p-pbar Collisions at sqrt(s) = 1.96 TeV
A search for the production of neutral Higgs bosons Phi decaying into
tau^+tau^- final states in p-pbar collisions at a center-of-mass energy of 1.96
TeV is presented. The data, corresponding to an integrated luminosity of up to
348 pb^-1, were collected by the D0 experiment at the Fermilab Tevatron
Collider. Since no excess compared to the expectation from standard model
processes is found, limits on the production cross section times branching
ratio are set. The results are combined with those obtained from the D0 search
for Phi b(b) to b-bbar-b(bbar) and are interpreted in the minimal
supersymmetric standard model.Comment: Version accpeted by Phys. Rev. Lett. (minor changes
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