119,263 research outputs found
Evidence for CP violation in B+→K∗(892)+π0 from a Dalitz plot analysis of B+→K0Sπ+π0 decays
No full textWe report a Dalitz plot analysis of charmless hadronic decays of charged B mesons to the final state K0Sπ+π0 using the full BABAR data set of 470.9±2.8 million B ̄B events collected at the Υ(4S) resonance. We measure the overall branching fraction and CP asymmetry to be B(B+→K0π+π0)=(31.8±1.8±2.1+6.0−0.0)×10−6 and ACP(B+→K0π+π0)=0.07±0.05±0.03+0.02−0.03, where the uncertainties are statistical, systematic, and due to the signal model, respectively. This is the first measurement of the branching fraction for B+→K0π+π0. We find first evidence of a CP asymmetry in B+→K∗(892)+π0 decays: ACP(B+→K∗(892)+π0)=−0.52±0.14±0.04+0.04−0.02. The significance of this asymmetry, including systematic and model uncertainties, is 3.4 standard deviations. We also measure the branching fractions and CP asymmetries for three other intermediate decay modes
The Belle II SVD data readout system
No full textThe Belle II Experiment at the High Energy Accelerator Research Organization (KEK) in Tsukuba, Japan, will explore the asymmetry between matter and antimatter and search for new physics beyond the standard model.
172 double-sided silicon strip detectors are arranged cylindrically in four layers around the collision point to be part of a system which measures the tracks of the collision products of electrons and positrons. A total of 1748 radiation-hard APV25 chips read out 128 silicon strips each and send the analog signals by time-division multiplexing out of the radiation zone to 48 Flash Analog Digital Converter Modules (FADC).
Each of them applies processing to the data; for example, it uses a digital finite impulse response filter to compensate line signal distortions, and it extracts the peak timing and amplitude from a set of several data points for each hit, using a neural network.
We present an overview of the SVD data readout system, along with front-end electronics, cabling, power supplies and data processing
The Belle II silicon vertex detector assembly and mechanics
No full textThe Belle II experiment at the asymmetric SuperKEKB collider in Japan will operate at an instantaneous luminosity approximately 50 times greater than its predecessor (Belle). The central feature of the experiment is a vertex detector comprising two layers of pixelated silicon detectors (PXD) and four layers of double-sided silicon microstrip detectors (SVD). One of the key measurements for Belle II is CP violation asymmetry in the decays of beauty and charm hadrons, which hinges on a precise charged-track vertex determination and low-momentum track measurement. Towards this goal, a proper assembly of the SVD components with precise alignment ought to be performed and the geometrical tolerances should be checked to fall within the design limits. We present an overview of the assembly procedure that is being followed, which includes the precision gluing of the SVD module components, wire-bonding of the various electrical components, and precision 3D coordinate measurements of the final SVD modules.
Finally, some results from the latest test-beam are reported
The s-CVD radiation monitoring and beam abort system of the Belle-II Vertex Detector
No full textThe Belle-II VerteX Detector (VXD) is a 6 layers silicon tracker device that will cope with an unprecedented luminosity of 8 × 1035 cm-2 s-1 achievable by the new SuperKEKB e+e- collider, now under commissioning at the KEK laboratory (Tsukuba, Japan). A radiation monitoring and beam abort system has been developed based on single-crystal s-CVD diamond sensors. The sensors will be placed in 20 key positions in the vicinity of the interaction region. The severe space limitations require a remote readout of the sensors. In this contribution we present the system design, along with the sensor characterisation procedure. We present also the preliminary results with the prototype system during the first SuperKEKB commissioning phase in February-June 2016
Study of B -> pi l nu and B -> rho l nu decays and determination of |Vub|
No full textWe present an analysis of exclusive charmless semileptonic B-meson decays based on 377×106 BB̅ pairs recorded with the BABAR detector at the Υ(4S) resonance. We select four event samples corresponding to the decay modes B0→π-l+ν, B+→π0l+ν, B0→ρ-l+ν, and B+→ρ0l+ν and find the measured branching fractions to be consistent with isospin symmetry. Assuming isospin symmetry, we combine the two B→πlν samples, and similarly the two B→ρlν samples, and measure the branching fractions B(B0→π-l+ν)=(1.41±0.05±0.07)×10-4 and B(B0→ρ-l+ν)=(1.75±0.15±0.27)×10-4, where the errors are statistical and systematic. We compare the measured distribution in q2, the momentum transfer squared, with predictions for the form factors from QCD calculations and determine the Cabibbo-Kobayashi-Maskawa matrix element |Vub|. Based on the measured partial branching fraction for B→πlν in the range q2<12 GeV2 and the most recent QCD light-cone sum-rule calculations, we obtain |Vub|=(3.78±0.13-0.40+0.55)×10-3, where the errors refer to the experimental and theoretical uncertainties. From a simultaneous fit to the data over the full q2 range and the FNAL/MILC lattice QCD results, we obtain |Vub|=(2.95±0.31)×10-3 from B→πlν, where the error is the combined experimental and theoretical uncertainty
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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