We present the first comprehensive tests of light-lepton universality in the angular distributions of semileptonic $B^0$-meson decays to charged spin-1 charmed mesons. We measure five ...angular-asymmetry observables as functions of the decay recoil that are sensitive to lepton-universality-violating contributions. We use events where one neutral $B$ is fully reconstructed in $\Upsilon\left(4S\right)\to{}B \overline{B}$ decays in data corresponding to $189~\mathrm{fb}^{-1}$ integrated luminosity from electron-positron collisions collected with the Belle II detector. We find no significant deviation from the standard model expectations.
The measurement of two-particle angular correlation functions in high-multiplicity e^{+}e^{-} collisions at sqrts=10.52 GeV is reported. In this study, the 89.5 fb^{-1} of hadronic e^{+}e^{-} ...annihilation data collected by the Belle detector at KEKB are used. Two-particle angular correlation functions are measured in the full relative azimuthal angle (Δϕ) and three units of pseudorapidity (Δη), defined by either the electron beam axis or the event-shape thrust axis, and are studied as a function of charged-particle multiplicity. The measurement in the thrust axis analysis, with mostly outgoing quark pairs determining the reference axis, is sensitive to the region of additional soft gluon emissions. No significant anisotropic collective behavior is observed with either coordinate analyses. Near-side jet correlations appear to be absent in the thrust axis analysis. The measurements are compared to predictions from various event generators and are expected to provide new constraints to the phenomenological models in the low-energy regime.
Using 980 fb−1 of data collected with the Belle detector operating at the KEKB asymmetric-energy e+ e− collider, we report the measurements of the masses, and the first measurements of the instrinsic ...widths, of the Σc ( 2455 )+ and Σc (2520)+ charmed baryons. We find M (Σc (2455)+) − M (Λc+) = 166.17 ± 0.0 5−0.07+0.16 MeV / c2, Γ (Σc (2455)+) = 2.3 ± 0.3 ± 0.3 MeV /c2, M ( Σc (2520)+) − M(Λc+) = 230.9 ± 0. 5− 0.1+ 0.5 MeV / c2, and Γ(Σc (2520)+) = 17.2− 2.1− 0.7+2.3+3.1 MeV / c2, where the uncertainties are statistical and systematic, respectively. These measurements can be used to test models of the underlying quark structure of the Σc states.
First measurement of the Λc+→ pη′ decay Li, S. X.; Shen, C. P.; Adachi, I. ...
The journal of high energy physics,
03/2022, Letnik:
2022, Številka:
3
Journal Article
Recenzirano
Odprti dostop
A
bstract
We present the first measurement of the branching fraction of the singly Cabibbo-suppressed (SCS) decay
Λ
c
+
→ pη
′ with
η
′
→ ηπ
+
π
−
, using a data sample corresponding to an integrated ...luminosity of 981 fb
−
1
, collected by the Belle detector at the KEKB
e
+
e
−
asymmetric-energy collider. A significant
Λ
c
+
→ pη
′ signal is observed for the first time with a signal significance of 5.4
σ
. The relative branching fraction with respect to the normalization mode
Λ
c
+
→ pK
−
π
+
is measured to be
B
Λ
c
+
→
pη
′
B
Λ
c
+
→
pK
−
π
+
=
7.54
±
1.32
±
0.73
×
10
−
3
,
where the uncertainties are statistical and systematic, respectively. Using the world-average value of
B
Λ
c
+
→
pK
−
π
+
= (6
.
28
±
0
.
32)
×
10
−
2
, we obtain
B
Λ
c
+
→
pη
′
=
4.73
±
0.82
±
0.46
±
0.24
×
10
−
4
,
where the uncertainties are statistical, systematic, and from
B
Λ
c
+
→
pK
−
π
+
, respectively.
We report a measurement of decay-time-dependent charge-parity ( C P ) asymmetries in B 0 → K S 0 K S 0 K S 0 decays. We use 387 × 10 6 B B ¯ pairs collected at the ϒ ( 4 S ) resonance with the Belle ...II detector at the SuperKEKB asymmetric-energy electron-positron collider. We reconstruct 220 signal events and extract the C P -violating parameters S and C from a fit to the distribution of the decay-time difference between the two B mesons. The resulting confidence region is consistent with previous measurements in B 0 → K S 0 K S 0 K S 0 and B 0 → ( c c ¯ ) K 0 decays and with predictions based on the standard model. Published by the American Physical Society 2024
Evidence for B + → K + ν ν ¯ decays Adachi, I.; Aggarwal, L.; Aloisio, A. ...
Physical review. D,
6/2024, Letnik:
109, Številka:
11
Journal Article
Recenzirano
We search for the rare decay B + → K + ν ν ¯ in a 362 fb − 1 sample of electron-positron collisions at the ϒ ( 4 S ) resonance collected with the Belle II detector at the SuperKEKB collider. We use ...the inclusive properties of the accompanying B meson in ϒ ( 4 S ) → B B ¯ events to suppress background from other decays of the signal B candidate and light-quark pair production. We validate the measurement with an auxiliary analysis based on a conventional hadronic reconstruction of the accompanying B meson. For background suppression, we exploit distinct signal features using machine learning methods tuned with simulated data. The signal-reconstruction efficiency and background suppression are validated through various control channels. The branching fraction is extracted in a maximum likelihood fit. Our inclusive and hadronic analyses yield consistent results for the B + → K + ν ν ¯ branching fraction of 2.7 ± 0.5 ( stat ) ± 0.5 ( syst ) × 10 − 5 and 1.1 − 0.8 + 0.9 ( stat ) − 0.5 + 0.8 ( syst ) × 10 − 5 , respectively. Combining the results, we determine the branching fraction of the decay B + → K + ν ν ¯ to be 2.3 ± 0.5 ( stat ) − 0.4 + 0.5 ( syst ) × 10 − 5 , providing the first evidence for this decay at 3.5 standard deviations. The combined result is 2.7 standard deviations above the standard model expectation. Published by the American Physical Society 2024
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