Using data samples of 89.5 fb−1, 711.0 fb−1, and 121.4 fb−1 collected with the Belle detector at the KEKB asymmetric-energy e+e− collider at center-of-mass energies 10.52, 10.58, and 10.867 GeV, ...respectively, we study the exclusive reactions e+e−→γχcJ (J=0, 1, 2) and e+e−→γηc. A significant γχc1 signal is observed for the first time at s=10.58 GeV with a significance of 5.1σ including systematic uncertainties. No significant excesses for γχc0, γχc2, and γηc final states are found, and we set 90% credibility level upper limits on the Born cross sections (σB) at 10.52 GeV, 10.58 GeV, and 10.867 GeV. Together with cross sections measured by BESIII at lower center-of-mass energies, the energy dependency of σB(e+e−→γχc1) is obtained.
Study of HF production in BaBar Resistive Plate Chambers Band, H.R.; Bellini, F.; Covarelli, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2008, Letnik:
594, Številka:
1
Journal Article
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The BaBar detector has operated over 200 2nd generation Resistive Plate Chambers (RPCs) in the forward endcap since 2002. Many chambers have increased noise rates and high-voltage currents. These ...aging symptoms are correlated with the integrated RPC current as expected, but also depend on the rate and direction of the gas flow, indicating that pollutants produced in the gas can accelerate aging of downstream RPC surfaces. HF produced by decomposition of the Freon 134a component of the BaBar RPC gas in electric discharges has been proposed as the main pollutant. This paper presents measurements of HF production and absorption rates in BaBar RPCs. Since many of the highest rate chambers in the forward endcap were converted to avalanche mode operation, a comparison of HF production in streamer and avalanche mode RPCs is made. Correlations between the HF production rate and other chamber operating conditions were also explored.
We report the analysis of the three-body e^{+}e^{-}→BBover ¯π^{±}, BBover ¯^{*}π^{±}, and B^{*}Bover ¯^{*}π^{±} processes, including the first observations of the Z_{b}^{±}(10610)→BBover ...¯^{*}+c.c.^{±} and Z_{b}^{±}(10650)→B^{*}Bover ¯^{*}^{±} transitions that are found to dominate the corresponding final states. We measure Born cross sections for the three-body production of σ(e^{+}e^{-}→BBover ¯^{*}+c.c.^{±}π^{∓})=17.4±1.6(stat)±1.9(syst) pb and σ(e^{+}e^{-}→B^{*}Bover ¯^{*}^{±}π^{∓})=8.75±1.15(stat)±1.04(syst) pb and set a 90% C.L. upper limit of σ(e^{+}e^{-}→BBover ¯^{±}π^{∓})<2.9 pb. The results are based on a 121.4 fb^{-1} data sample collected with the Belle detector at a center-of-mass energy near the ϒ(10860) peak.
Charged lepton flavor violation is forbidden in the Standard Model but possible in several new physics scenarios. In many of these models, the radiative decays τ± → ℓ±γ (ℓ = e, μ) are predicted to ...have a sizeable probability, making them particularly interesting channels to search at various experiments. An updated search via τ± → ℓ±γ using full data of the Belle experiment, corresponding to an integrated luminosity of 988 fb–1, is reported for charged lepton flavor violation. No significant excess over background predictions from the Standard Model is observed, and the upper limits on the branching fractions, B(τ± → μ±γ) ≤ 4.2 × 10–8 and B(τ± → e±γ) ≤ 5.6 × 10–8, are set at 90% confidence level.
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