109 research outputs found
Substrate-independent method for growing and modulating the density of polymer brushes from surfaces by ATRP
Published: April 19, 2012We describe a method for grafting PEG-based polymer chains of variable surface density using a substrate independent approach, allowing grafting from virtually any material substrate. The approach relies upon initial coupling of a macroinitiator to plasma polymer treated surfaces. The macroinitiator is a novel random terpolymer containing ATRP initiator residues, strongly negatively charged groups, and carboxylic acid moieties that facilitate covalent surface anchoring. Surface-initiated ATRP (SI-ATRP) using polyethylene glycol methyl ether methacrylate (PEGMA) at different concentrations led to grafted surfaces of controlled thickness in either the “brush” or “mushroom” morphology, which was controlled by the abundance of initiator residues in the macroinitiator. Grafted polymer layer structure was investigated via direct interaction force measurements using colloid probe atomic force microscopy (AFM). Equilibrium, hydrated graft layer thicknesses inferred from the highly repulsive AFM force data suggest that the polymer brush graft layer contained polymer chains which were fully stretched. Since the degree of stretching resulted in layer thicknesses approaching the polymer contour length, the polymer brushes studied must be very close to maximum graft density. Grafted layers where the polymer molecules were in the mushroom regime resulted in much thinner layers but the chains had greater chain entropic freedom as indicated by strongly attractive bridging interactions between tethered chains and the silica colloid probe. Use of this experimental methodology would be suitable for preparing grafted polymer layers of a preferred density free from substrate-specific linking chemistries.Bryan R. Coad, Yi Lu, Veronica Glattauer, and Laurence Meaghe
Measurement of via initial state radiation at Belle
The process (=1, 2) is studied via initial
state radiation using 980 fb of data at and around the
(=1, 2, 3, 4, 5) resonances collected with the Belle detector at the KEKB
asymmetric-energy collider. No significant signal is observed except
from decays. Upper limits on the cross sections between
and are determined at the 90% credibility
level, which range from few pb to a few tens of pb. We also set upper limits on
the decay rate of the vector charmonium [), , and
] and charmoniumlike [, , and ] states
to .Comment: Accepted by PR
Studies of charmed strange baryons in the final state at Belle
We report the discovery of , observed by its decay into
the final state , and present the first observation and evidence
of the decays of and into .
We also perform a combined analysis of the with the
and decay modes to measure
the ratios of branching fractions, masses and widths with improved accuracy. We
measure the ratios of branching fractions , , and , where the uncertainties are
statistical and systematic. The analysis is performed using a 980 fb
data sample collected with the Belle detector at the KEKB asymmetric-energy
collider.Comment: Submitted to PR
Study of pair production in single-tag two-photon collisions
We report a measurement of the differential cross section of pair
production in single-tag two-photon collisions, , in scattering. The cross section is measured for up to
30 GeV, where is the negative of the invariant mass squared of the
tagged photon, in the kinematic range 0.5 GeV < W < 2.1 GeV and < 1.0 for the total energy and pion scattering angle, respectively,
in the center-of-mass system. The results are based on a data
sample of 759 fb collected with the Belle detector at the KEKB
asymmetric-energy collider. The transition form factor of the
and that of the with the helicity-0, -1, and -2
components separately are measured for the first time and are compared with
theoretical calculations.Comment: 36 pages, 37 figures, 11 tables, Belle Preprint 2015-15, KEK Preprint
2015-2
Semi-inclusive studies of semileptonic decays at Belle
We present an analysis of the semi-inclusive decays and , where denotes a final state that
may consist of additional hadrons or photons and is an electron or muon.
The studied decays are contained in the
data sample collected by the Belle detector at the KEKB
asymmetric-energy collider. The branching fractions of the decays are
measured to be and
, where the first two uncertainties
are statistical and systematic and the last is due to external parameters. The
measurement also provides an estimate of the
production cross-section, ,
at the center-of-mass energy .Comment: 13 pages, 2 figures, submitted to Phys. Rev.
Observation of
We report the first observation of the decays . The data sample of fb used in this analysis corresponds
to million pairs, collected at the resonance by
the Belle detector at the KEKB asymmetric-energy collider. We
observe and excesses of events for the two decay
modes and measure the branching fractions of and to be
and ,
respectively, where the first uncertainties are statistical and the second are
systematic. These results are not compatible with the predictions based on the
generalized factorization approach. In addition, a threshold enhancement in the
di-baryon () system is observed, consistent with that observed
in similar decays.Comment: 16 pages, 3 figures and 3 tables, submitted to PR
Search for B+ -> l+ nu gamma decays with hadronic tagging using the full Belle data sample
We search for the decay B+ -> l+ nu gamma with l+ = e+ or mu+ using the full
Belle data set of 772 x 10^6 BBbar pairs, collected at the Y(4S) resonance with
the Belle detector at the KEKB asymmetric-energy e+e- collider. We reconstruct
one B meson in a hadronic decay mode and search for the B+ -> l+ nu gamma decay
in the remainder of the event. We observe no significant signal within the
phase space of E_gamma^sig > 1 GeV and obtain upper limits of BR(B+ -> e+ nu
gamma) mu+ nu gamma) l+ nu
gamma) < 3.5 x 10^-6 at 90 % credibility level.Comment: Submitted to Phys. Rev.
Evidence for the decay B0->eta pi^0
We report a search for the charmless hadronic decay with a
data sample corresponding to an integrated luminosity of 694
containing pairs. The data were collected by the
Belle experiment running on the resonance at the KEKB
collider. We measure a branching fraction
, where
the first uncertainty is statistical and the second is systematic. Our
measurement gives an upper limit of at 90\% confidence level. The signal has a significance of
standard deviations and constitutes the first evidence for this decay mode.Comment: 11 pages, 3 figures, 2 tables, submitted to Physical Review D(R
- …