A
bstract
We report a new measurement of the
e
+
e
−
→
ϒ(
nS
)
π
+
π
−
(
n
= 1
,
2
,
3) cross sections at energies from 10
.
52 to 11
.
02 GeV using data collected with the Belle detector at the KEKB ...asymmetric-energy
e
+
e
−
collider. We observe a new structure in the energy dependence of the cross sections; if described by a Breit-Wigner function its mass and width are found to be
M
=
10752.7
±
5.9
−
1.1
+
0.7
MeV
/
c
2
and
Γ
=
35.5
−
11.3
−
3.3
+
17.6
+
3.9
MeV, where the first error is statistical and the second is systematic. The global significance of the new structure including systematic uncertainty is 5.2 standard deviations. We also find evidence for the
e
+
e
−
→
ϒ (1
S
)
π
+
π
−
process at the energy 10
.
52 GeV, which is below the
B
B
¯
threshold.
Using a data sample of 980 fb−1 of e+e− annihilation data taken with the Belle detector operating at the KEKB asymmetric-energy e+e− collider, we report the results of a study of excited Ξc states ...that decay, via the emission of photons and/or charged pions, into Ξc0 or Ξc+ ground state charmed-strange baryons. We present new measurements of the masses of all members of the Ξc′, Ξc(2645), Ξc(2790), Ξc(2815), and Ξc(2980) isodoublets, measurements of the intrinsic widths of those that decay strongly, and evidence of previously unknown transitions.
An investigation was successfully made in the present work to obtain the solid-state coating of AISI316 stainless steel over EN24 medium carbon steel by friction surfacing process. Spindle speed, ...axial force, and table traverse speed were perceived to be the supreme aspects for bonding integrity. It was observed that the depth of the coating (C
t
) lessened as the coating width (C
w
) increased. The impact of process parameters on physical geometry of the coating was explored by experimentation based on desirability approach. The coefficients of correlation for coating width (0.94) and thickness (0.99) are extremely high. The coatings exhibited martensitic microstructure with fine grain size and without carbide particles which substantiates the effectiveness of good bonding. The optimal process parameters were identified by response surface methodology as 2.26 mm/s of Ts, 7.20 kN of AL, and 1447.17 rpm of RoS and also the output values are observed as C
t
= 2.10 mm and C
W
= 17.21 mm.
Abstract The silicon vertex detector (SVD) is installed at the heart of the Belle II experiment, taking data at the high-luminosity B-Factory SuperKEKB since 2019. The SVD is a four-layer ...double-sided strip detector with tracking and particle-identification capabilities. In this paper, we report on the performance of the reconstruction of SVD hits. The detector has shown a stable and above-99% hit efficiency, with a large signal-to-noise in all sensors since the beginning of data taking. Cluster position and time resolution have been measured with 2020 and 2022 data and show excellent performance and stability. In particular, the cluster-position resolution is between 7 and 12 μm for the small-pitch sensors, in reasonable agreement with the expectations, while the cluster time resolution is measured to be below 3 ns. The effect of radiation damage is visible, but not affecting the performance. As the luminosity increases, higher machine backgrounds are expected and the excellent hit-time information in SVD can be exploited for background rejection. In particular, we have recently developed a novel procedure to select hits by grouping them event-by-event based on their time. This new procedure allows a significant reduction of the fake rate, while preserving the tracking efficiency, and it has therefore replaced the previous cut-based procedure. We have developed a method that uses the SVD hits to estimate the track time (previously unavailable) and the collision time. It has a similar precision to the estimate based on the drift chamber readout but its execution time is three orders of magnitude smaller, allowing a faster online reconstruction that is crucial in a high luminosity regime. The track time is a powerful information that allows, together with the aforementioned grouping selection, to raise the occupancy limit above that expected at nominal luminosity, leaving room for a safety factor. Finally, in June 2022 the data taking of the Belle II experiment was stopped to install a new two-layer DEPFET detector (PXD) and upgrade components of the accelerator. The whole silicon tracker (PXD+SVD) has been extracted from Belle II, the new PXD installed, the detector closed and commissioned. We briefly describe the SVD results of this upgrade.
We report the result from the first search for D0 decays to invisible final states. The analysis is performed on a data sample of 924 fb−1 collected at and near the ϒ(4S) and ϒ(5S) resonances with ...the Belle detector at the KEKB asymmetric-energy e+e− collider. The absolute branching fraction is determined using an inclusive D0 sample, obtained by fully reconstructing the rest of the particle system including the other charmed particle. No significant signal yield is observed and an upper limit of 9.4×10−5 is set on the branching fraction of D0 to invisible final states at 90% confidence level.
We report measurements of isospin asymmetry Δ0− and difference of direct CP asymmetries ΔACP between charged and neutral B→Xsγ decays. This analysis is based on the data sample containing 772×106BB¯ ...pairs that was collected with the Belle detector at the KEKB energy-asymmetric e+e− collider. Using a sum-of-exclusive technique with invariant Xs mass up to 2.8 GeV/c2, we obtain Δ0−=−0.48±1.49(stat)±0.97(syst)±1.15(f+−/f00)% and ΔACP=+3.69±2.65(stat)±0.76(syst)%, where the last uncertainty for Δ0− is due to the uncertainty on the production ratio of B+B− to B0B¯0 in (4S) decays. The measured value of Δ0− is consistent with zero, allowing us to constrain the resolved photon contribution in the B→Xsγ, and improve the branching fraction prediction. The result for ΔACP is consistent with the prediction of the SM. We also measure the direct CP asymmetries for charged and neutral B→Xsγ decays. All the measurements are the most precise to date.
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