1,272 research outputs found
Sensitivity reduction using optimally derived controllers
Feedback structures to reduce parameter sensitivity of linear system derived from solution of classical linear regulator problem for design of automatic control system
Optical follow-up of gravitational wave triggers with DECam
Gravitational wave (GW) events have several possible progenitors, including black hole mergers, cosmic string cusps, supernovae, neutron star mergers, and black hole–neutron star mergers. A subset of GW events are expected to produce electromagnetic (EM) emission that, once detected, will provide complementary information about their astrophysical context. To that end, the LIGO-Virgo Collaboration has partnered with other teams to send GW candidate alerts so that searches for their EM counterparts can be pursued. One such partner is the Dark Energy Survey (DES) and Dark Energy Camera (DECam) Gravitational Waves Program (DES-GW). Situated on the 4m Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile, DECam is an ideal instrument for optical followup observations of GW triggers in the southern sky. The DES-GW program performs subtraction of new search images with respect to preexisting overlapping images to select candidate sources. Due to the short decay timescale of the expected EM counterparts and the need to quickly eliminate survey areas with no counterpart candidates, it is critical to complete the initial analysis of each night's images within 24 hours. The computational challenges in achieving this goal include maintaining robust I/O pipelines during the processing, being able to quickly acquire template images of new sky regions outside of the typical DES observing regions, and being able to rapidly provision additional batch computing resources with little advance notice. We will discuss the search area determination, imaging pipeline, general data transfer strategy, and methods to quickly increase the available amount of batch computing. We will present results from the first season of observations from September 2015 to January 2016 and conclude by presenting improvements planned for the second observing season
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
Measurements of differential cross sections of Z/gamma*+jets+X events in proton anti-proton collisions at sqrt{s}=1.96 TeV
We present cross section measurements for Z/gamma*+jets+X production,
differential in the transverse momenta of the three leading jets. The data
sample was collected with the D0 detector at the Fermilab Tevatron proton
anti-proton collider at a center-of-mass energy of 1.96 TeV and corresponds to
an integrated luminosity of 1 fb-1. Leading and next-to-leading order
perturbative QCD predictions are compared with the measurements, and agreement
is found within the theoretical and experimental uncertainties. We also make
comparisons with the predictions of four event generators. Two
parton-shower-based generators show significant shape and normalization
differences with respect to the data. In contrast, two generators combining
tree-level matrix elements with a parton shower give a reasonable description
of the the shapes observed in data, but the predicted normalizations show
significant differences with respect to the data, reflecting large scale
uncertainties. For specific choices of scales, the normalizations for either
generator can be made to agree with the measurements.Comment: Published in PLB. 11 pages, 3 figure
Search for charged Higgs bosons decaying to top and bottom quarks in ppbar collisions
We describe a search for production of a charged Higgs boson, q \bar{q'} ->
H^+, reconstructed in the t\bar{b} final state in the mass range 180 <= M_{H^+}
<= 300 GeV. The search was undertaken at the Fermilab Tevatron collider with a
center-of-mass energy sqrt{s} = 1.96 TeV and uses 0.9 fb^{-1} of data collected
with the D0 detector. We find no evidence for charged Higgs boson production
and set upper limits on the production cross section in the Types I, II and III
two-Higgs-doublet models (2HDMs). An excluded region in the (M_{H^+},tan\beta)
plane for Type I 2HDM is presented.Comment: Submitted to Phys. Rev. Letter
Measurement of the forward-backward charge asymmetry and extraction of sin^2Theta^{eff}_W in ppbar -> Z/\gamma^{*}+X -> e+e+X events produced at \sqrt{s}=1.96 TeV
We present a measurement of the forward-backward charge asymmetry ()
in events at a center-of-mass energy
of 1.96 TeV using 1.1 fb of data collected with the D0 detector at the
Fermilab Tevatron collider. is measured as a function of the invariant
mass of the electron-positron pair, and found to be consistent with the
standard model prediction. We use the measurement to extract the
effective weak mixing angle .Comment: 7 Pages, 1 Figure, 3 Tables, Accepted by Phys. Rev. Let
Measurement of the lifetime of the B_c meson in the semileptonic decay channel
Using approximately 1.3 fb-1 of data collected by the D0 detector between
2002 and 2006, we measure the lifetime of the B_c meson in the B_c -> J/psi mu
nu X final state. A simultaneous unbinned likelihood fit to the J/\psi+mu
invariant mass and lifetime distributions yields a signal of 881 +/- 80 (stat)
candidates and a lifetime measurement of \tau(B_c) = 0.448 +0.038 -0.036 (stat)
+/- 0.032 (syst) ps.Comment: 7 pages, 2 figures, submitted to Phys. Rev. Let
Observation of ZZ production in ppbar collisions at sqrt(s) = 1.96 TeV
We present an observation for ZZ -> l+l-l'+l'- (l, l' = e or mu) production
in ppbar collisions at a center-of-mass energy of sqrt(s) = 1.96 TeV. Using 1.7
fb-1 of data collected by the D0 experiment at the Fermilab Tevatron Collider,
we observe three candidate events with an expected background of 0.14 +0.03
-0.02 events. The significance of this observation is 5.3 standard deviations.
The combination of D0 results in this channel, as well as in ZZ -> l+l-nunubar,
yields a significance of 5.7 standard deviations and a combined cross section
of sigma(ZZ) = 1.60 +/- 0.63 (stat.) +0.16 -0.17 (syst.) pb.Comment: 7 pages, 1 figure, 2 tables Modified slightly following review
proces
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