592 research outputs found
Dy8SnS13.61O0.39 from single-crystal data
Crystals of the title dysprosium tin sulfide oxide, Dy8SnS13S1âxOx [x = 0.39â
(4)], were obtained unintentionally from the DyâSnâS system. A statistical mixture of sulfur and oxygen was assumed for one position in the structure. S and O atoms surround each of the eight symmetrically non-equivalent dysprosium atoms. The Sn atoms are located in tetraÂhedral surroundings of sulfur atoms. Trigonal prisms and tetraÂhedra are connected to each other by their edges. All atoms are situated in mirror planes
Effective Lagrangians for physical degrees of freedom in the Randall-Sundrum model
We derive the second variation Lagrangian of the Randall-Sundrum model with
two branes, study its gauge invariance and diagonalize it in the unitary gauge.
We also show that the effective four-dimensional theory looks different on
different branes and calculate the observable mass spectra and the couplings of
the physical degrees of freedom of 5-dimensional gravity to matter.Comment: 22 pages, LaTeX, typos correcte
Study of Leading Hadrons in Gluon and Quark Fragmentation
The study of quark jets in e+e- reactions at LEP has demonstrated that the
hadronisation process is reproduced well by the Lund string model. However, our
understanding of gluon fragmentation is less complete. In this study enriched
quark and gluon jet samples of different purities are selected in three-jet
events from hadronic decays of the Z collected by the DELPHI experiment in the
LEP runs during 1994 and 1995. The leading systems of the two kinds of jets are
defined by requiring a rapidity gap and their sum of charges is studied. An
excess of leading systems with total charge zero is found for gluon jets in all
cases, when compared to Monte Carlo Simulations with JETSET (with and without
Bose-Einstein correlations included) and ARIADNE. The corresponding leading
systems of quark jets do not exhibit such an excess. The influence of the gap
size and of the gluon purity on the effect is studied and a concentration of
the excess of neutral leading systems at low invariant masses (<~ 2 GeV/c^2) is
observed, indicating that gluon jets might have an additional hitherto
undetected fragmentation mode via a two-gluon system. This could be an
indication of a possible production of gluonic states as predicted by QCD.Comment: 19 pages, 6 figures, Accepted by Phys. Lett.
Measurement of the semileptonic charge asymmetry in B0 meson mixing with the D0 detector
We present a measurement of the semileptonic mixing asymmetry for B0 mesons,
a^d_{sl}, using two independent decay channels: B0 -> mu+D-X, with D- ->
K+pi-pi-; and B0 -> mu+D*-X, with D*- -> antiD0 pi-, antiD0 -> K+pi- (and
charge conjugate processes). We use a data sample corresponding to 10.4 fb^{-1}
of ppbar collisions at sqrt(s) = 1.96 TeV, collected with the D0 experiment at
the Fermilab Tevatron collider. We extract the charge asymmetries in these two
channels as a function of the visible proper decay length (VPDL) of the B0
meson, correct for detector-related asymmetries using data-driven methods, and
account for dilution from charge-symmetric processes using Monte Carlo
simulation. The final measurement combines four signal VPDL regions for each
channel, yielding a^d_{sl} = [0.68 \pm 0.45 \text{(stat.)} \pm 0.14
\text{(syst.)}]%. This is the single most precise measurement of this
parameter, with uncertainties smaller than the current world average of B
factory measurements.Comment: Version includes minor textual changes following peer review by
journal, most notably the updating of Ref. [21] to reflect the most recent
publicatio
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
Study of ZÎł events and limits on anomalous ZZÎł and Zγγ couplings in ppÌ collisions at s=1.96TeV
We present a measurement of the ZÎł production cross section and limits on anomalous ZZÎł and Zγγ couplings for form-factor scales of Î=750 and 1000 GeV. The measurement is based on 138 (152) candidates in the eeÎł (ÎŒÎŒÎł) final state using 320(290)pb-1 of ppÌ collisions at s=1.96TeV. The 95% C.L. limits on real and imaginary parts of individual anomalous couplings are |h10,30Z|<0.23, |h20,40Z|<0.020, |h10,30Îł|<0.23, and |h20,40Îł|<0.019 for Î=1000GeV. © 2005 The American Physical Society
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.
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 single top quark production cross sections and |Vtb| in ppbar collisions at sqrt{s}=1.96 TeV
We present measurements of production cross sections of single top quarks in
\ppbar collisions at in a data sample corresponding
to an integrated luminosity of collected by the D0 detector
at the Fermilab Tevatron Collider. We select events with an isolated electron
or muon, an imbalance in transverse energy, and two, three, or four jets, with
one or two of them containing a bottom hadron. We obtain an inclusive cross
section of \sigma({\ppbar}{\rargap}tb+X, tqb+X) = 3.43\pm^{0.73}_{0.74}\;\rm
pb and use it to extract the CKM matrix element at
the 95% C.L. We also measure \sigma({\ppbar}{\rargap}tb+X) =
0.68\pm^{0.38}_{0.35}\;\rm pb and \sigma({\ppbar}{\rargap}tqb+X) =
2.86\pm^{0.69}_{0.63}\;\rm pb when assuming, respectively, and
production rates as predicted by the standard model.Comment: 11 pages, 8 figures, submitted to Phys. Rev.
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