2,309 research outputs found
Hyperpolarized Long-T1 Silicon Nanoparticles for Magnetic Resonance Imaging
Silicon nanoparticles are experimentally investigated as a potential
hyperpolarized, targetable MRI imaging agent. Nuclear T_1 times at room
temperature for a variety of Si nanoparticles are found to be remarkably long
(10^2 to 10^4 s) - roughly consistent with predictions of a core-shell
diffusion model - allowing them to be transported, administered and imaged on
practical time scales without significant loss of polarization. We also report
surface functionalization of Si nanoparticles, comparable to approaches used in
other biologically targeted nanoparticle systems.Comment: supporting material here:
http://marcuslab.harvard.edu/Aptekar_hyper1_sup.pd
The Radio Structure of High-Energy Peaked BL Lacertae Objects
We present VLA and first-epoch VLBA observations that are part of a program
to study the parsec-scale radio structure of a sample of fifteen
high-energy-peaked BL Lacs (HBLs). The sample was chosen to span the range of
logarithmic X-ray to radio flux ratios observed in HBLs. As this is only the
first epoch of observations, proper motions of jet components are not yet
available; thus we consider only the structure and alignment of the parsec- and
kiloparsec-scale jets. Like most low-energy-peaked BL Lacs (LBLs), our HBL
sample shows parsec-scale, core-jet morphologies and compact, complex
kiloparsec-scale morphologies. Some objects also show evidence for bending of
the jet 10-20pc from the core, suggesting interaction of the jet with the
surrounding medium. Whereas LBLs show a wide distribution of parsec- to
kpc-scale jet misalignment angles, there is weak evidence that the jets in HBLs
are more well-aligned, suggesting that HBL jets are either intrinsically
straighter or are seen further off-axis than LBL jets.Comment: Accepted, A
Measurements of time-dependent CP asymmetries in decays using a partial reconstruction technique
We report results on time-dependent CP asymmetries in decays based on a data sample containing 657 {\times}
pairs collected with the Belle detector at the KEKB
asymmetric-energy collider at the resonance. We use a
partial reconstruction technique, wherein signal
events are identified using information only from the fast pion from the B
decay and the slow pion from the subsequent decay of the , where the
former (latter) corresponds to final states. We obtain CP
violation parameters and .Comment: 8 pages, 5 figures, 2 tables, submitted to Physical Review D (RC
Improved measurement of time-dependent CP violation in B0 -> J/Psi pi0 decays
We report improved measurements of time-dependent CP violation parameters for
decay. This analysis is based on 535 million
pairs accumulated at the resonance with the Belle
detector at the KEKB asymmetric-energy e^+e^- collider. From the distribution
of proper time intervals between the two B decays, we obtain the following CP
violation parameters and , which are consistent with Standard Model
expectations.Comment: Resubmitted to PRD(RC), including 4 figures, 6pages Revision has been
made according to communication with PRD referee
Measurement of the decay and determination of
We present a measurement of the charmless semileptonic decay
using a data sample containing 657
events collected with the Belle detector at the KEKB
asymmetric-energy collider operating near the
resonance. We determine the total branching fraction of the decay,
. We also report a new precise measurement
of the differential decay rate, and extract the Cabibbo-Kobayashi-Maskawa
matrix element using model-independent and -dependent approaches.
From a simultaneous fit to the measured differential decay rate and lattice QCD
results, we obtain , where the error
includes both statistical and systematic uncertainties.Comment: 8 pages, 3 figures, Submitted to PRD(RC
Search for CP violation in the decays and
We have searched for CP violation in the charmed meson decays and using 673 fb of data
collected with the Belle detector at the KEKB asymmetric-energy
collider. No evidence for CP violation is observed. We report the most
sensitive CP asymmetry measurements to date for these decays: , , , and , where the first uncertainties are statistical and
the second are systematic
Measurement of CP Asymmetries and Branching Fractions in a Time-Dependent Dalitz Analysis of B^0-->(rho pi)^0 and a Constraint on the Quark Mixing Angle phi_2
We present the results of a time-dependent Dalitz plot analysis of B0 --> pi+
pi- pi0 decays based on a 414/fb data sample that contains 449 x 10^6 BB pairs.
The data was collected on the Upsilon(4S) resonance with the Belle detector at
the KEKB asymmetric energy e+e- collider. Combining our analysis with
information on charged B decay modes, we perform a full Dalitz and isospin
analysis and obtain a constraint on the quark mixing angle phi_2, 68deg. <
phi_2 < 95deg. at the 68.3% confidence level for the phi_2 solution consistent
with the standard model (SM). A large SM-disfavored region also remains. The
branching fractions for the decay processes of B0 --> rho+-(770) pi-+ and B0
--> rho0(770) pi0 are measured to be (22.6 +- 1.1[stat.] +- 4.4 [syst.]) x
10^{-6} and (3.0 +- 0.5 [stat.] +- 0.7 [syst.]) x 10^{-6}, respectively. These
are the first branching fraction measurements of the process B0 --> rho(770)pi
with the lowest resonance rho(770) explicitly separated from the radial
excitations.Comment: 26 pages, 12 figures, to be submitted to Phys. Rev. D; Revision to
Phys. Rev. D published versio
Observation of B^0 \to D^{*-} \tau^+ \nu_{\tau} decay at Belle
We report an observation of the decay in a
data sample containing pairs collected with the
Belle detector at the KEKB asymmetric-energy collider. We find a
signal with a significance of 5.2 standard deviations and measure the branching
fraction . This is the first observation of an exclusive
decay with a transition.Comment: 6 pages, 3 figures, submitted to Phys. Rev. Let
Search for CP Violation in D Meson Decays to phi pi+
We search for CP violation in Cabibbo-suppressed charged D meson decays by
measuring the difference between the CP violating asymmetries for the
Cabibbo-suppressed decays D+ -> K+K-pi+ and the Cabibbo-favored decays Ds ->
K+K-pi+ in the K+K- mass region of the phi resonance. Using 955/fb of data
collected with the Belle detector we obtain A_CP(D+ -> phi pi+) = (+0.51 +-
0.28 +- 0.05)%. The measurement improves the sensitivity of previous searches
by more than a factor of five. We find no evidence for direct CP violation.Comment: submitted to PR
Observation of Bs->Ds(*)+Ds(*)- using e+e- collisions and a determination of the Bs-Bsbar width difference \Delta\Gamma_s
We have made the first observation of Bs->Ds(*)+Ds(*)- decays using 23.6 fb-1
of data recorded by the Belle experiment running on the Upsilon(5S) resonance.
The branching fractions are measured to be B(B^0_s\ra D^+_s D^-_s) =
(1.0\,^{+0.4}_{-0.3}\,^{+0.3}_{-0.2})%, B(B^0_s\ra D^{*\pm}_s D^{\mp}_s) =
(2.8\,^{+0.8}_{-0.7}\,\pm 0.7)%, and B(B^0_s\ra D^{*+}_s D^{*-}_s) =
(3.1\,^{+1.2}_{-1.0}\,\pm 0.8)%; the sum is B(B^0_s\ra D^{(*)+}_s D^{(*)-}_s) =
(6.9\,^{+1.5}_{-1.3}\,\pm 1.9)%. Assuming Bs->Ds(*)+Ds(*)- saturates decays to
CP-even final states, the branching fraction determines the ratio
\Delta\Gamma_s/cos(\phi), where \Delta\Gamma_s is the difference in widths
between the two Bs-Bsbar mass eigenstates, and \phi is a CP-violating weak
phase. Taking CP violation to be negligibly small, we obtain
\Delta\Gamma_s/\Gamma_s =
0.147^{+0.036}_{-0.030}(stat.)^{+0.044}_{-0.042}(syst.), where \Gamma_s is the
mean decay width.Comment: 13 pages, 2 figures, 2 tables. v2: text added for clarification,
version published in Phys. Rev. Letter
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