Observation of the Decay Bs0 → K0 K ¯ 0 Schwartz, A. J.; Aihara, H.; Ayad, R. ...
Physical review letters,
04/2016, Letnik:
116, Številka:
16
Journal Article
Recenzirano
Odprti dostop
We measure the decay B$^{0}_{s}$ → K0K¯0 using data collected at the Υ(5S) resonance with the Belle detector at the KEKB e+e– collider. The data sample used corresponds to an integrated luminosity of ...121.4 fb–1. We measure a branching fraction B(B$^{0}_{s}$ → K0K¯0) = 19.6$^{+5.8}_{–5.1}$(stat.) ± 1.0(sys.)±2.0(NB$^{0}_{s}$B¯$^{0}_{s}$)×10–6 with a significance of 5.1 standard deviations. Here, this measurement constitutes the first observation of this decay.
The Belle II silicon vertex detector is one of the vertex detectors in the Belle II experiment. The detector reads out the signals from the double-sided silicon strip sensors with the APV25 front-end ...readout ASIC, adopting the chip-on-sensor concept to minimize the strip noise. The detector has been operated in the experiment since the spring of 2019. Analyzing the acquired data during the beam collisions, the excellent performance of the detector is confirmed. Also, the radiation dose and 1-MeV equivalent neutron fluence of the detector are estimated using the measured dose rates of the diamond sensors installed on the beam pipe and are compared with the measured radiation effects in the strip noise, leakage current, and depletion voltage. This paper briefly introduces the main features of the silicon vertex detector, and then reports on the measured performance and radiation effects of the first two years of running experience of the detector.
We report the measurement of branching fractions and CP-violation asymmetries in B → ϕϕK decays based on a 711 fb−1 data sample containing 772 × 106 B¯B events. The data were recorded at the Υ(4S) ...resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. For B+ → ϕϕK+, the branching fraction and CP-violation asymmetry measured below the ηc threshold ... respectively. Similarly, the branching fraction obtained for ... below the ηc threshold is ... . We also measure the CP-violation symmetry for ... within the ηc region ... .(ProQuest: ... denotes formulae omitted.)
Here, we measure the branching fraction and time-dependent CP-violating asymmetry for B0 → J/ψ π0 decays using a data sample of 711 fb–1 collected on the Υ (4S) resonance by the Belle experiment ...running at the KEKB e+e– collider. The branching fraction is measured to be B(B0 → J/ψ π0) = 1.62 ± 0.11 (stat) ± 0.06 (syst) × 10–5, which is the most precise measurement to date. The measured CP asymmetry parameters are S = –0.59 ± 0.19 (stat) ± 0.03 (syst) and A = –0.15 ± 30.14 (stat) +0.04 (syst). The mixing-induced CP asymmetry (S) differs from the case of no CP violation by 3.0 standard deviations, and the direct CP asymmetry (A) is consistent with zero.
We report a search for a heavy neutral lepton (HNL) that mixes predominantly with ν τ . The search utilizes data collected with the Belle detector at the KEKB asymmetric energy e + e − collider. The ...data sample was collected at and just below the center-of-mass energies of the ϒ ( 4 S ) and ϒ ( 5 S ) resonances and has an integrated luminosity of 915 fb − 1 , corresponding to ( 836 ± 12 ) × 10 6 e + e − → τ + τ − events. We search for production of the HNL (denoted N ) in the decay τ − → π − N followed by its decay via N → μ + μ − ν τ . The search focuses on the parameter-space region in which the HNL is long-lived, so that the μ + μ − originate from a common vertex that is significantly displaced from the collision point of the KEKB beams. Consistent with the expected background yield, one event is observed in the data sample after application of all the event-selection criteria. We report limits on the mixing parameter of the HNL with the τ neutrino as a function of the HNL mass. Published by the American Physical Society 2024
We present the results of the first Dalitz plot analysis of the decay D 0 → K-π +η. The analysis is performed on a data set corresponding to an integrated luminosity of 953 fb-1 collected by the ...Belle detector at the asymmetric-energy e+e- KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels K- * (892)0 η, K-a0(980)+, K-a2(1320)+, K¯ * (1410)0 η, K* (1680)-π + and K* 2 (1980)-π +, together with Kπ and Kη S-wave components. The decays K* (1680)- → K-η and K* 2 (1980)- → K-η are observed for the first time. We measure ratio of the branching fractions, B(D0→K-π+η) B(D0→K=π+) = 0.500 ± 0.002(stat) ± 0.020(syst) ± 0.003(BPDG). Using the Dalitz fit result, the ratio B(K*(1680)→Kη) B(K*(1680)→Kπ) is measured to be 0.11±0.02(stat)+0.06 =0.04(syst)± 0.04(BPDG); this is much lower than the theoretical expectations (≈ 1) made under the assumption that K* (1680) is a pure 1 3D1 state. The product branching fraction B(D 0 → K* 2 (1980)- → K-ηπ +) = (2.2 +1.7 -1.9 ) × 10-4 is determined. In addition, the πη' contribution to the a0(980)± resonance shape is confirmed with 10.1σ statistical significance using the three-channel Flatté model. We also measure B(D 0 → K¯ * (892)0 η) = (1.41+0.13 -0.12)%. This is consistent with, and more precise than, the current world average (1.02 ± 0.30)%, deviates with a significance of more than 3σ from the theoretical predictions of (0.51-0.92)%.
We have searched for the Cabibbo-suppressed decay Λc+→ϕpπ0 in e+e− collisions using a data sample corresponding to an integrated luminosity of 915 fb−1. The data were collected by the Belle ...experiment at the KEKB e+e− asymmetric-energy collider running at or near the ϒ(4S) and ϒ(5S) resonances. No significant signal is observed, and we set an upper limit on the branching fraction of B(Λc+→ϕpπ0)<15.3×10−5 at 90% confidence level. The contribution of nonresonant Λc+→K+K−pπ0 decays is found to be consistent with zero, and the corresponding upper limit on its branching fraction is set to be B(Λc+→K+K−pπ0)NR<6.3×10−5 at 90% confidence level. We also search for an intermediate hidden-strangeness pentaquark decay Ps+→ϕp. We see no evidence for this intermediate decay and set an upper limit on the product branching fraction of B(Λc+→Ps+π0)×B(Ps+→ϕp)<8.3×10−5 at 90% confidence level. Finally, we measure the branching fraction for the Cabibbo-favored decay Λc+→K−π+pπ0; the result is B(Λc+→K−π+pπ0)=(4.42±0.05(stat)±0.12(syst)±0.16(norm))%, which is the most precise measurement to date.
PDF
