215 research outputs found
Observation and study of the decay
We report the observation and study of the decay
using events
collected with the BESIII detector. Its branching fraction, including all
possible intermediate states, is measured to be
. We also report evidence for a structure,
denoted as , in the mass spectrum in the GeV/
region. Using two decay modes of the meson ( and
), a simultaneous fit to the mass spectra is
performed. Assuming the quantum numbers of the to be , its
significance is found to be 4.4, with a mass and width of MeV/ and MeV, respectively, and a
product branching fraction
. Alternatively, assuming , the
significance is 3.8, with a mass and width of MeV/ and MeV, respectively, and a product
branching fraction
. The angular distribution of
is studied and the two assumptions of the
cannot be clearly distinguished due to the limited statistics. In all
measurements the first uncertainties are statistical and the second systematic.Comment: 10 pages, 6 figures and 4 table
Observation of and confirmation of its large branching fraction
The baryonic decay is observed, and the
corresponding branching fraction is measured to be
, where the first uncertainty is statistical
and second systematic. The data sample used in this analysis was collected with
the BESIII detector operating at the BEPCII double-ring collider with
a center-of-mass energy of 4.178~GeV and an integrated luminosity of
3.19~fb. The result confirms the previous measurement by the CLEO
Collaboration and is of greatly improved precision, which may deepen our
understanding of the dynamical enhancement of the W-annihilation topology in
the charmed meson decays
Evidence of a resonant structure in the cross section between 4.05 and 4.60 GeV
The cross section of the process for
center-of-mass energies from 4.05 to 4.60~GeV is measured precisely using data
samples collected with the BESIII detector operating at the BEPCII storage
ring.
Two enhancements are clearly visible in the cross section around 4.23 and
4.40~GeV.
Using several models to describe the dressed cross section yields stable
parameters for the first enhancement, which has a mass of 4228.6 \pm 4.1 \pm
6.3 \un{MeV}/c^2 and a width of 77.0 \pm 6.8 \pm 6.3 \un{MeV}, where the
first uncertainties are statistical and the second ones are systematic.
Our resonant mass is consistent with previous observations of the
state and the theoretical prediction of a molecule.
This result is the first observation of associated with an
open-charm final state.
Fits with three resonance functions with additional , ,
, , or a new resonance, do not show significant
contributions from either of these resonances. The second enhancement is not
from a single known resonance. It could contain contributions from
and other resonances, and a detailed amplitude analysis is required to better
understand this enhancement
Observation of and Improved Measurements of
Using a data sample corresponding to an integrated luminosity of
2.93~fb recorded by the BESIII detector at a center-of-mass energy of
GeV, we present an analysis of the decays and . By performing a partial wave
analysis, the -wave contribution to
is observed to be % with a statistical significance greater
than 10, besides the dominant -wave contribution. This is the first
observation of the -wave contribution. We measure the branching fractions
, , and . An upper limit
of is set at the 90% confidence level. We also obtain the hadronic
form factor ratios of at assuming the
single-pole dominance parameterization:
,
Evidence for the decays of and
We study the hadronic decays of to the final states
and , using an annihilation
data sample of 567 pb taken at a center-of-mass energy of 4.6 GeV with
the BESIII detector at the BEPCII collider. We find evidence for the decays
and with
statistical significance of and , respectively.
Normalizing to the reference decays and
, we obtain the ratios of the branching fractions
and to be and , respectively. The upper limits at the 90\% confidence level are
set to be and . Using BESIII measurements of the
branching fractions of the reference decays, we determine
() and
(). Here, the first uncertainties are statistical and the second
systematic. The obtained branching fraction of is
consistent with the previous measurement, and the branching fraction of
is measured for the first
time.Comment: Accepted by Chin. Phys. C : Chin. Phys. C 43, 083002, (2019
Determination of the pseudoscalar decay constant via
Using a data sample collected at an
center-of-mass energy of GeV with the BESIII detector, we
measure the branching fraction of the leptonic decay to
be . Combining our branching fraction with the masses of the
and and the lifetime of the , we determine
.
Using the quark mixing matrix element determined from a
global standard model fit, we evaluate the decay constant
\,MeV. Alternatively,
using the value of calculated by lattice quantum chromodynamics, we
find . These values
of , , and
are each the most precise results to date
Search for heavy Majorana neutrino in lepton number violating decays of D→Kπe+e+
Using a data sample with an integrated luminosity of 2.93 fb-1 taken at the center-of-mass energy of 3.773 GeV, we search for the Majorana neutrino (νm) in the lepton number violating decays D→Kπe+e+. No significant signal is observed, and the upper limits on the branching fraction at the 90% confidence level are set to be B(D0→K-π-e+e+)<2.8×10-6, B(D+→KS0π-e+e+)<3.3×10-6 and B(D+→K-π0e+e+)<8.5×10-6. The Majorana neutrino is searched for with different mass assumptions ranging from 0.25 to 1.0 GeV/c2 in the decays D0→K-e+νm,νm→π-e+ and D+→KS0e+νm,νm→π-e+, and the upper limits on the branching fraction at the 90% confidence level are at the level of 10-7∼10-6, depending on the mass of the Majorana neutrino. The constraints on the mixing matrix element |Veνm|2 are also evaluated
Measurements of the branching fractions of the singly Cabibbo-suppressed decays D0→ωη, η(')π0 and η(')η
By analyzing a data sample of 2.93 fb−1 collected at ffiffi
s p ¼ 3.773 GeV with the BESIII detector operated
at the BEPCII storage rings, we measure the branching fractions BðD0 → ωηÞ¼ð2.15 0.17stat
0.15sysÞ × 10−3, BðD0 → ηπ0Þ¼ð0.58 0.05stat 0.05sysÞ × 10−3, BðD0 → η0
π0Þ¼ð0.93 0.11stat
0.09sysÞ × 10−3, BðD0 → ηηÞ¼ð2.20 0.07stat 0.06sysÞ × 10−3 and BðD0 → η0
ηÞ¼ð0.94 0.25stat
0.11sysÞ × 10−3. We note that BðD0 → ωηÞ is measured for the first time and that BðD0 → ηηÞ is measured
with much improved precision
Allele Polymorphism and Haplotype Diversity of HLA-A, -B and -DRB1 Loci in Sequence-Based Typing for Chinese Uyghur Ethnic Group
Previous studies indicate that the frequency distributions of HLA alleles and haplotypes vary from one ethnic group to another or between the members of the same ethnic group living in different geographic areas. It is necessary and meaningful to study the high-resolution allelic and haplotypic distributions of HLA loci in different groups.High-resolution HLA typing for the Uyghur ethnic minority group using polymerase chain reaction-sequence-based-typing method was first reported. HLA-A, -B and -DRB1 allelic distributions were determined in 104 unrelated healthy Uyghur individuals and haplotypic frequencies and linkage disequilibrium parameters for HLA loci were estimated using the maximum-likelihood method. A total of 35 HLA-A, 51 HLA-B and 33 HLA-DRB1 alleles were identified at the four-digit level in the population. High frequency alleles were HLA-A*1101 (13.46%), A*0201 (12.50%), A*0301 (10.10%); HLA-B*5101(8.17%), B*3501(6.73%), B*5001 (6.25%); HLA-DRB1*0701 (16.35%), DRB1*1501 (8.65%) and DRB1*0301 (7.69%). The two-locus haplotypes at the highest frequency were HLA-A*3001-B*1302 (2.88%), A*2402-B*5101 (2.86%); HLA-B*5001-DRB1*0701 (4.14%) and B*0702-DRB1*1501 (3.37%). The three-locus haplotype at the highest frequency was HLA-A*3001-B*1302-DRB1*0701(2.40%). Significantly high linkage disequilibrium was observed in six two-locus haplotypes, with their corresponding relative linkage disequilibrium parameters equal to 1. Neighbor-joining phylogenetic tree between the Uyghur group and other previously reported populations was constructed on the basis of standard genetic distances among the populations calculated using the four-digit sequence-level allelic frequencies at HLA-A, HLA-B and HLA-DRB1 loci. The phylogenetic analyses reveal that the Uyghur group belongs to the northwestern Chinese populations and is most closely related to the Xibe group, and then to Kirgiz, Hui, Mongolian and Northern Han.The present findings could be useful to elucidate the genetic background of the population and to provide valuable data for HLA matching in clinical bone marrow transplantation, HLA-linked disease-association studies, population genetics, human identification and paternity tests in forensic sciences
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