253 research outputs found
Neutralization, effector function and immune imprinting of Omicron variants
Currently circulating SARS-CoV-2 variants have acquired convergent mutations at hot spots in the receptor-binding domain (RBD) of the spike protein. The effects of these mutations on viral infection and transmission and the efficacy of vaccines and therapies remains poorly understood. Here we demonstrate that recently emerged BQ.1.1 and XBB.1.5 variants bind host ACE2 with high affinity and promote membrane fusion more efficiently than earlier Omicron variants. Structures of the BQ.1.1, XBB.1 and BN.1 RBDs bound to the fragment antigen-binding region of the S309 antibody (the parent antibody for sotrovimab) and human ACE2 explain the preservation of antibody binding through conformational selection, altered ACE2 recognition and immune evasion. We show that sotrovimab binds avidly to all Omicron variants, promotes Fc-dependent effector functions and protects mice challenged with BQ.1.1 and hamsters challenged with XBB.1.5. Vaccine-elicited human plasma antibodies cross-react with and trigger effector functions against current Omicron variants, despite a reduced neutralizing activity, suggesting a mechanism of protection against disease, exemplified by S309. Cross-reactive RBD-directed human memory B cells remained dominant even after two exposures to Omicron spikes, underscoring the role of persistent immune imprinting
Search for the decay at Belle
We report a search for the rare charmless decay
using a data sample of
pairs collected at the resonance with
the Belle detector at the KEKB asymmetric-energy collider. No
statistically significant signal is found and a 90% confidence-level upper
limit is set on the decay branching fraction as .Comment: 8 pages, 3 figures, submitted to PRD(RC
Search for and a measurement of the branching fraction for
We search for the decay and measure the
branching fraction for using
121.4~ of data collected at the
resonance with the Belle detector at the KEKB asymmetric-energy
collider. The branching fraction is measured
to be , where is the fraction of
in events. Our result is in good
agreement with the theoretical predictions as well as with a recent measurement
from LHCb. We observe no statistically significant signal for the decay
and set a confidence-level upper
limit on its branching fraction at . This constitutes a
significant improvement over the previous result.Comment: 6 pages, 3 figure
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
Measurements of the masses and widths of the and baryons
We present measurements of the masses and decay widths of the baryonic states
and using a data sample
corresponding to an integrated luminosity of 711 fb collected with the
Belle detector at the KEKB asymmetric-energy collider operating at
the resonance. We report the mass differences with respect to
the baryon MeV/, MeV/,
MeV/, MeV/, and the decay widths
MeV/,
MeV/,
MeV/,
MeV/,
where the first uncertainties are statistical and the second are systematic.
The isospin mass splittings are measured to be
MeV/ and
MeV/. These results are the most precise to date.Comment: 13 pages, 4 figures, Submitted to PRD(RC
Evidence of and search for double-charmonium production in and decays
Using data samples of and
events collected with the Belle detector, a first experimental
search has been made for double-charmonium production in the exclusive decays
, where , , , , and . No significant signal is
observed in the spectra of the mass recoiling against the reconstructed
or except for the evidence of production with a
significance of for . The
measured branching fraction \BR(\Upsilon(1S)\rightarrow J/\psi+\chi_{c1}) is
. The
confidence level upper limits on the branching fractions of the other modes
having a significance of less than are determined. These results are
consistent with theoretical calculations using the nonrelativistic QCD
factorization approach.Comment: 12 pages, 4 figures, 1 table. The fit range was extended to include
X(4160) signal according to referee's suggestions. Other results unchanged.
Paper was accepted for publication as a regular article in Physical Review
Measurements of the and resonances via
We report new measurements of the total cross sections for ( = 1, 2, 3) and from a
high-luminosity fine scan of the region - GeV with the
Belle detector. We observe that the spectra have
little or no non-resonant component and extract from them the masses and widths
of and and their relative phase. We find
MeV/ and
\Gamma_{10860}=(53.7^{+7.1}_{-5.6}\,^{+1.3}_{-5.4}) MeV and report first
measurements M_{11020}=(10987.5^{+6.4}_{-2.5}\,^{+9.0}_{-2.1}) MeV/,
\Gamma_{11020}=(61^{+9}_{-19}\,^{+2}_{-20}) MeV, and \phi_{\rm
11020}-\phi_{\rm 10860} = (-1.0\pm0.4\,^{+1.4}_{-0.1}) rad.Comment: University of Cincinnati preprint UCHEP-15-01, submitted to Physical
Review D - Rapid Communication
Invariant-mass and fractional-energy dependence of inclusive production of di-hadrons in annihilation at 10.58 GeV
The inclusive cross sections for di-hadrons of charged pions and kaons
() in electron-positron annihilation are reported. They
are obtained as a function of the total fractional energy and invariant mass
for any di-hadron combination in the same hemisphere as defined by the thrust
event-shape variable and its axis. Since same-hemisphere di-hadrons can be
assumed to originate predominantly from the same initial parton, di-hadron
fragmentation functions are probed. These di-hadron fragmentation functions are
needed as an unpolarized baseline in order to quantitatively understand related
spin-dependent measurements in other processes and to apply them to the
extraction of quark transversity distribution functions in the nucleon. The
di-hadron cross sections are obtained from a data sample
collected at or near the resonance with the Belle detector at
the KEKB asymmetric-energy collider.Comment: 21 pages, 18 figures plus 25 figures in supplemental material,
submitted to PR
Observation of a new charged charmoniumlike state in B -> J/psi K pi decays
We present the results of an amplitude analysis of anti-B0 -> J/psi K- pi+
decays. A new charged charmoniumlike state Zc(4200)+ decaying to J/psi pi+ is
observed with a significance of 6.2 sigma. The mass and width of the Zc(4200)+
are 4196 +31-29 +17-13 MeV/c^2 and 370 +70-70 +70-132 MeV, respectively; the
preferred assignment of the quantum numbers is J^P = 1^+. In addition, we find
evidence for Zc(4430)+ -> J/psi pi+. The analysis is based on a 711 fb^-1 data
sample collected by the Belle detector at the asymmetric-energy e+ e- collider
KEKB.Comment: 14 pages, 13 figure
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