We study the processes e^{+}e^{-}→ωχ_{bJ}(1P) (J=0, 1, or 2) using samples at center-of-mass energies sqrts=10.701, 10.745, and 10.805 GeV, corresponding to 1.6, 9.8, and 4.7 fb^{-1} of integrated ...luminosity, respectively. These data were collected with the Belle II detector during special operations of the SuperKEKB collider above the ϒ(4S) resonance. We report the first observation of ωχ_{bJ}(1P) signals at sqrts=10.745 GeV. By combining Belle II data with Belle results at sqrts=10.867 GeV, we find energy dependencies of the Born cross sections for e^{+}e^{-}→ωχ_{b1,b2}(1P) to be consistent with the shape of the ϒ(10753) state. These data indicate that the internal structures of the ϒ(10753) and ϒ(10860) states may differ. Including data at sqrts=10.653 GeV, we also search for the bottomonium equivalent of the X(3872) state decaying into ωϒ(1S). No significant signal is observed for masses between 10.45 and 10.65 GeV/c^{2}.
A
bstract
We report the first measurement of the inclusive
e
+
e
−
→
b
b
¯
→
D
s
±
X
and
e
+
e
−
→
b
b
¯
→ D
0
/
D
¯
0
X
cross sections in the energy range from 10
.
63 to 11
.
02 GeV. Based on these ...results, we determine
σ
(
e
+
e
−
→
B
s
0
B
¯
s
0
X
) and
σ
(
e
+
e
−
→
B
B
¯
X
) in the same energy range. We measure the fraction of
B
s
0
events at Υ(10860) to be
f
s
= (
22.0
−
2.1
+
2.0
)%. We determine also the ratio of the
B
s
0
inclusive branching fractions
B
(
B
s
0
→ D
0
/
D
¯
0
X
)
/
B
(
B
s
0
→
D
s
±
X
) = 0
.
416 ± 0
.
018 ± 0
.
092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energy
e
+
e
−
collider.
The singly Cabibbo-suppressed decay Λ_{c}^{+}→nπ^{+} is observed for the first time with a statistical significance of 7.3σ by using 3.9 fb^{-1} of e^{+}e^{-} collision data collected at ...center-of-mass energies between 4.612 and 4.699 GeV with the BESIII detector at BEPCII. The branching fraction of Λ_{c}^{+}→nπ^{+} is measured to be (6.6±1.2_{stat}±0.4_{syst})×10^{-4}. By taking the upper limit of branching fractions of Λ_{c}^{+}→pπ^{0} from the Belle experiment, the ratio of branching fractions between Λ_{c}^{+}→nπ^{+} and Λ_{c}^{+}→pπ^{0} is calculated to be larger than 7.2 at the 90% confidence level, which disagrees with most predictions of the available phenomenological models. In addition, the branching fractions of the Cabibbo-favored decays Λ_{c}^{+}→Λπ^{+} and Λ_{c}^{+}→Σ^{0}π^{+} are measured to be (1.31±0.08_{stat}±0.05_{syst})×10^{-2} and (1.22±0.08_{stat}±0.07_{syst})×10^{-2}, respectively, which are consistent with previous results.
A
bstract
Using a data sample of 980 fb
−
1
collected with the Belle detector at the KEKB asymmetric-energy
e
+
e
−
collider, we study for the first time the singly Cabibbo-suppressed decays
Ω
c
0
→
...Ξ
−
π
+
and Ω
−
K
+
and the doubly Cabibbo-suppressed decay
Ω
c
0
→
Ξ
−
K
+
. Evidence for an
Ω
c
0
signal in the
Ω
c
0
→
Ξ
−
π
+
mode is reported with a significance of 4
.
5
σ
including systematic uncertainties. The ratio of branching fractions to the normalization mode
Ω
c
0
→
Ω
−
π
+
is measured to be
B
Ω
c
0
→
Ξ
−
π
+
/
B
Ω
c
0
→
Ω
−
π
+
=
0.253
±
0.052
stat
.
±
0.030
syst
.
.
No significant signals of
Ω
c
0
→
Ξ
−
K
+
and Ω
−
K
+
modes are found. The upper limits at 90% confidence level on ratios of branching fractions are determined to be
B
Ω
c
0
→
Ξ
−
K
+
/
B
Ω
c
0
→
Ω
−
π
+
<
0.070
and
B
Ω
c
0
→
Ω
−
K
+
/
B
Ω
c
0
→
Ω
−
π
+
<
0.29
.
Using a data sample corresponding to an integrated luminosity of 2.93 fb^{-1} collected at a center-of-mass energy sqrts=3.773 GeV by the BESIII detector, the decay D^{0}→ωϕ is observed for the ...first time. The branching fraction is measured to be (6.48±0.96±0.40)×10^{-4} with a significance of 6.3σ, where the first and second uncertainties are statistical and systematic, respectively. An angular analysis reveals that the ϕ and ω mesons from the D^{0}→ωϕ decay are transversely polarized. The 95% confidence level upper limit on longitudinal polarization fraction is set to be less than 0.24, which is inconsistent with current theoretical expectations and challenges our understanding of the underlying dynamics in charm meson decays.
Measurement of the Λ_{c}^{+} Lifetime Ahmed, H; Ahn, J K; Aloisio, A ...
Physical review letters,
2023-Feb-17, 20230217, Letnik:
130, Številka:
7
Journal Article
Recenzirano
An absolute measurement of the Λ_{c}^{+} lifetime is reported using Λ_{c}^{+}→pK^{-}π^{+} decays in events reconstructed from data collected by the Belle II experiment at the SuperKEKB ...asymmetric-energy electron-positron collider. The total integrated luminosity of the data sample, which was collected at center-of-mass energies at or near the ϒ(4S) resonance, is 207.2 fb^{-1}. The result, τ(Λ_{c}^{+})=203.20±0.89±0.77 fs, where the first uncertainty is statistical and the second systematic, is the most precise measurement to date and is consistent with previous determinations.
The purpose of this study was to identify best practices perceived and used by principals in low-SES high schools to achieve high annual attendance rates. The study was an applied qualitative design, ...which used interviews for data collection and an emergent approach to data analysis. It involved a combination of criterion and extreme sampling to identify and interview eight principals from low-SES high schools (grades 9–12) in West Virginia with an annual attendance rate over 90%. Coding and data analysis processes involved in vitro and structural protocols. The following best practices emerged from the research in order of most to least used: offering incentives and student recognition; establishing a positive school culture with high expectations for students to come to school; holding meetings with parents, students and an administrator; having personalized communication between students and an adult within the school; telephoning families of absent students; consistently following established district and state policies for attendance; and picking up absent students at their homes. All the approaches revealed could be characterized as aspects of one overall best practice: developing a positive culture within the school. The ensuing specific best practices were actions and policies consistently applied and enforced. Improved attendance results in improved performance and college- and career-readiness. Approaches similar to those revealed in this study of high-attendance, low-SES West Virginia high schools may help to improve attendance and achievement in other high schools, not just in West Virginia, but throughout the United States.
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