The Belle experiment has accomplished various CP violation measurements, in order to constrain the CKM Unitarity Triangle and to search for New Physics signatures, using a data sample of 772 million ...B-meson pairs. The Belle II experiment will extend research capabilities in this field, thanks to the 50 times larger integrated luminosity expected to be delivered by the SuperKEKB e+e− collider. The results from Belle and future prospects at Belle II are presented.
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
$$ ...{\Omega}_c^0\to {\Xi}^{-}{\pi}^{+} $$
Ω
c
0
→
Ξ
−
π
+
and Ω
−
K
+
and the doubly Cabibbo-suppressed decay
$$ {\Omega}_c^0\to {\Xi}^{-}{K}^{+} $$
Ω
c
0
→
Ξ
−
K
+
. Evidence for an
$$ {\Omega}_c^0 $$
Ω
c
0
signal in the
$$ {\Omega}_c^0 $$
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
$$ {\Omega}_c^0 $$
Ω
c
0
→
Ω
−
π
+
is measured to be
$$ \mathcal{B}\left({\Omega}_c^0\to {\Xi}^{-}{\pi}^{+}\right)/\mathcal{B}\left({\Omega}_c^0\to {\Omega}^{-}{\pi}^{+}\right)=0.253\pm 0.052\left(\textrm{stat}.\right)\pm 0.030\left(\textrm{syst}.\right). $$
B
Ω
c
0
→
Ξ
−
π
+
/
B
Ω
c
0
→
Ω
−
π
+
=
0.253
±
0.052
stat
.
±
0.030
syst
.
.
No significant signals of
$$ {\Omega}_c^0\to {\Xi}^{-}{K}^{+} $$
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
$$ \mathcal{B}\left({\Omega}_c^0\to {\Xi}^{-}{K}^{+}\right)/\mathcal{B}\left({\Omega}_c^0\to {\Omega}^{-}{\pi}^{+}\right)<0.070 $$
B
Ω
c
0
→
Ξ
−
K
+
/
B
Ω
c
0
→
Ω
−
π
+
<
0.070
and
$$ \mathcal{B}\left({\Omega}_c^0\to {\Omega}^{-}{K}^{+}\right)/\mathcal{B}\left({\Omega}_c^0\to {\Omega}^{-}{\pi}^{+}\right)<0.29. $$
B
Ω
c
0
→
Ω
−
K
+
/
B
Ω
c
0
→
Ω
−
π
+
<
0.29
.
We present the first measurements of absolute branching fractions of Ξ_{c}^{0} decays into Ξ^{-}π^{+}, ΛK^{-}π^{+}, and pK^{-}K^{-}π^{+} final states. The measurements are made using a dataset ...comprising (772±11)×10^{6} BBover ¯ pairs collected at the ϒ(4S) resonance with the Belle detector at the KEKB e^{+}e^{-} collider. We first measure the absolute branching fraction for B^{-}→Λover ¯_{c}^{-}Ξ_{c}^{0} using a missing-mass technique; the result is B(B^{-}→Λover ¯_{c}^{-}Ξ_{c}^{0})=(9.51±2.10±0.88)×10^{-4}. We subsequently measure the product branching fractions B(B^{-}→Λover ¯_{c}^{-}Ξ_{c}^{0})B(Ξ_{c}^{0}→Ξ^{-}π^{+}), B(B^{-}→Λover ¯_{c}^{-}Ξ_{c}^{0})B(Ξ_{c}^{0}→ΛK^{-}π^{+}), and B(B^{-}→Λover ¯_{c}^{-}Ξ_{c}^{0})B(Ξ_{c}^{0}→pK^{-}K^{-}π^{+}) with improved precision. Dividing these product branching fractions by the result for B^{-}→Λover ¯_{c}^{-}Ξ_{c}^{0} yields the following branching fractions: B(Ξ_{c}^{0}→Ξ^{-}π^{+})=(1.80±0.50±0.14)%, B(Ξ_{c}^{0}→ΛK^{-}π^{+})=(1.17±0.37±0.09)%, and B(Ξ_{c}^{0}→pK^{-}K^{-}π^{+})=(0.58±0.23±0.05)%. For the above branching fractions, the first uncertainties are statistical and the second are systematic. Our result for B(Ξ_{c}^{0}→Ξ^{-}π^{+}) can be combined with Ξ_{c}^{0} branching fractions measured relative to Ξ_{c}^{0}→Ξ^{-}π^{+} to yield other absolute Ξ_{c}^{0} branching fractions.
We report the first evidence for X(3872) production in two-photon interactions by tagging either the electron or the positron in the final state, exploring the highly virtual photon region. The ...search is performed in e^{+}e^{-}→e^{+}e^{-}J/ψπ^{+}π^{-}, using 825 fb^{-1} of data collected by the Belle detector operated at the KEKB e^{+}e^{-} collider. We observe three X(3872) candidates, where the expected background is 0.11±0.10 events, with a significance of 3.2σ. We obtain an estimated value for Γover ˜_{γγ}B(X(3872)→J/ψπ^{+}π^{-}) assuming the Q^{2} dependence predicted by a ccover ¯ meson model, where -Q^{2} is the invariant mass squared of the virtual photon. No X(3915)→J/ψπ^{+}π^{-} candidates are found.
The branching fractions of the Υ(1S) inclusive decays into final states with a J/ψ or a ψ(2S) are measured with improved precision to be B(Υ(1S)→J/ψ+anything)=(5.25±0.13(stat)±0.25(syst))×10-4 and ...B(Υ(1S)→ψ(2S)+anything)=(1.23±0.17(stat)±0.11(syst))×10-4. The first search for Υ(1S) decays into XYZ states that decay into a J/ψ or a ψ(2S) plus one or two charged tracks yields no significant signals for XYZ states in any of the examined decay modes, and upper limits on their production rates in Υ(1S) inclusive decays are determined.
We have searched for the lepton-flavor-violating decay B0→K*0μ±e∓ using a data sample of 711 fb−1 that contains 772×106 BB¯ pairs. The data were collected near the ϒ(4S) resonance with the Belle ...detector at the KEKB asymmetric-energy e+e− collider. No signals were observed, and we set 90% confidence level upper limits on the branching fractions of B(B0→K*0μ+e−)<1.2×10−7, B(B0→K*0μ−e+)<1.6×10−7, and, for both decays combined, B(B0→K*0μ±e∓)<1.8×10−7. These are the most stringent limits on these decays to date.
Here, we present a measurement of angular observables and a test of lepton flavor universality in the B → K*ℓ+ℓ- decay, where ℓ is either e or μ . The analysis is performed on a data sample ...corresponding to an integrated luminosity of 711fb-1 containing 772×106 B B ¯ pairs, collected at the Υ ( 4S ) resonance with the Belle detector at the asymmetric-energy e+e- collider KEKB. The finding is consistent with standard model (SM) expectations, where the largest discrepancy from a SM prediction is observed in the muon modes with a local significance of 2.6σ .
Observation of ϒ(4S)→η^{'}ϒ(1S) Al Said, S; Asner, D M; Ayad, R ...
Physical review letters,
2018-Aug-10, Letnik:
121, Številka:
6
Journal Article
Recenzirano
Odprti dostop
We report the first observation of the hadronic transition ϒ(4S)→η^{'}ϒ(1S), using 496 fb^{-1} data collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} ...collider. We reconstruct the η^{'} meson through its decays to ρ^{0}γ and to π^{+}π^{-}η, with η→γγ. We measure B(ϒ(4S)→η^{'}ϒ(1S))=3.43±0.88(stat)±0.21(syst)×10^{-5}, with a significance of 5.7σ.
Performance, reliability and scalability in data access are key issues in the context of Grid computing and High Energy Physics (HEP) data analysis. We present the technical details and the results ...of a large scale validation and performance measurement achieved at the CNAF Tier1, the central computing facility of the Italian National Institute for Nuclear Research (INFN). The aim of this work is the evaluation of data access activity during analysis tasks within BaBar and ALICE computing models against two of the most used data handling systems in HEP scenario: GPFS and Scalla/Xrootd.
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