No abstract

No abstract

Abstract-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 DEPFET R & D project is reviewed in the light of the requirements of the vertex detector at a future linear e + e − collider.

No abstract

We recently discovered an error in the way the Belle installation of EVTGEN [1] treated semileptonic B 0 s decays. It was found that the generated distribution of the lepton decay angle in the rest frame of the virtual W boson was uniform. This also led to incorrectly modeled lepton momentum spectra in the simulation. There were two consequences of this modeling error: the normalization of the signal component obtained in the fit to the lepton momentum distributions was incorrect, and the acceptance within the selected fiducial region was incorrectly estimated. We have addressed this problem by correcting the affected Monte Carlo (MC) distributions. Below, we report on the resulting changes in the measurement. All values that change with respect to the original publication are also summarized in Table I. The corrected signal acceptances for the pðℓ þ Þ > 0.6 GeV selection criterion are 93% and 94% for electrons and muons, respectively. The signal lepton identification efficiencies multiplied by the geometrical acceptance are estimated to be 77% (electrons) and 71% (muons). We repeat the fit to the measured lepton momentum spectra with the correct MC distribution of prompt leptons (see Fig 1). The χ 2 =d:o:f: value of the fits are 3.6=7 and 5.7=7 for the electron and muon modes, respectively. The efficiency-corrected yields of prompt leptons are ½3.91 AE 0.18ðstatÞ × 10 3 electrons and ½4.37 AE 0.21ðstatÞ × 10 3 muons. These yields translate into the following ratiosThe combination of the e þ and μ þ modes, R e;μ , takes into account the correlations between the two modes. The correction of the signal MC distributions also modifies the systematic uncertainties in the "signal modeling" category in Table II of the original publication. The uncertainty on R due to the modeling of the shape of the prompt lepton spectra is reevaluated to be 1.0% for both electrons and muons. The uncertainty due to the composition of the semileptonic width becomes 1.6% and 2.1% for electrons and muons, respectively. The total systematic uncertainties on R are recalculated to be 3.3% (3.1%) for the electron mode and 4.0% (3.6%) for the muon mode, where the values in parentheses are the fully correlated errors between both modes. Based on the ratios, R ℓ , we obtain the following values for the semileptonic branching fraction BðB 0 s → X − ℓ þ ν ℓ Þ: