We report a search for X(3872) and X(3915) in B+→χc1π0K+ decays. We set an upper limit of B(B+→X(3872)K+)×B(X(3872)→χc1π0)<8.1×10−6 and B(B+→X(3915)K+)×B(X(3915)→χc1π0)<3.8×10−5 at 90% confidence ...level. We also measure B(X(3872)→χc1π0)/B(X(3872)→J/ψπ+π−)<0.97 at 90% confidence level. The results reported here are obtained from 772×106 BB events collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider.
The DEPFET collaboration develops highly granular, ultra-transparent active pixel detectors for high-performance vertex reconstruction at future collider experiments. The characterization of detector ...prototypes has proven that the key principle, the integration of a first amplification stage in a detector-grade sensor material, can provide a comfortable signal to noise ratio of over 40 for a sensor thickness of 50-75 μm. ASICs have been designed and produced to operate a DEPFET pixel detector with the required read-out speed. A complete detector concept is being developed, including solutions for mechanical support, cooling, and services. In this paper, the status of the DEPFET R & D project is reviewed in the light of the requirements of the vertex detector at a future linear e + e - collider.
We report inclusive and exclusive measurements for χc1 and χc2 production in B decays. We measure B(B → χc1X)= (3.03 ± 0.05(stat) ± 0.24(syst)) × 10$-$3 and B(B → χc2X)= (0.70 ± 0.06(stat) ± ...0.10(syst)) × 10$-$3 . For the first time, χc2 production in exclusive B decays in the modes B0 → χc2π $-$K+ and B+ → χc2π+π$-$K+ has been observed, along with first evidence for the B+ → χc2π+K$0\atop{S}$ decay mode. For χc1 production, we report the first observation in the B+ → χc1π+π$-$K+, B0 → χc1π+π$-$K$0\atop{S}$ and B0 → χc1π0π$-$K+ decay modes. Using these decay modes, we observe a difference in the production mechanism of χc2 in comparison to χc1 in B decays. In addition, we report searches for X(3872) and χc1(2P) in the B+ → (χc1π+π$-$)K+ decay 3 mode. The reported results use 772 × 106 B$\overline{B}$ events collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e$-$ collider.
We present the first measurements of branching fractions of rare tau-lepton decays, τ− →π−ντℓ+ℓ− (ℓ = e or μ), using a data sample corresponding to 562 fb−1 collected at a center-of-mass energy of ...10.58 GeV with the Belle detector at the KEKB asymmetric-energy e+e− collider. The τ−→π−ντe+e− decay is observed for the first time with 7.0σ significance. The partial branching fraction determined by the structure-dependent mechanisms mediated by either a vector or an axial-vector current for the mass region Mπee > 1.05 GeV/c2 is measured to be B(τ− →π−ντe+e−)Mπ−e+e− > 1.05 GeV/c2 = (5.90 ± 0.53 ± 0.85 ± 0.11) × 10−6, where the first uncertainty is statistical, the second is systematic, and the third is due to model dependence. In the full phase space, due to the different detection efficiencies for the structure-dependent mechanisms mediated by axial-vector and vector currents, the branching fraction varies from BA(τ−→π−ντe+e−) = (1.46 ± 0.13 ± 0.21) × 10−5 to BV(τ−→π−ντe+e−) = (3.01 ± 0.27 ± 0.43) × 10−5, respectively. An upper limit is set on the branching fraction of the τ−→π−ντμ+μ− decay, B(τ− →π−ντμ+μ−) < 1.14 × 10−5, at the 90% confidence level.
We present a search for a non-Standard-Model invisible particle X0 in the mass range 0.1-1.8GeV/c2 in B+→e+X0 and B+→μ+X0 decays. The results are obtained from a 711 fb-1 data sample that corresponds ...to 772×106BB pairs, collected at the Υ(4S) resonance with the Belle detector at the KEKB e+e- collider. One B meson is fully reconstructed in a hadronic mode to determine the momentum of the lepton of the signal decay in the rest frame of the recoiling partner B meson. We find no evidence of a signal and set upper limits on the order of 10-6.
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