P. I. Hopman

Optimization of silicon microstrip detector design for CLEO III

Abstract We present measurements from prototype silicon microstrip detectors for the CLEO III silicon vertex detector. Noise and capacitance optimization is discussed. We also present a design to achieve 10 pF total capacitance on a double sided, double metal silicon detector.

Search for CP violation in B+/- --> J/psiK+/- and B+/- --> psi(2S)K+/- decays.

We present a search for direct CP violation in B+/--->J/psiK+/- and B+/--->psi(2S)K+/- decays. In a sample of 9.7x10(6) B&Bmacr; meson pairs collected with the CLEO detector, we have fully reconstructed 534 B+/--->J/psiK+/- and 120 B+/--->psi(2S)K+/- decays with very low background. We have measured the CP-violating charge asymmetry to be [+1.8+/-4.3(stat)+/-0.4(syst)]% for B+/--->J/psiK+/- and [+2.0+/-9. 1(stat)+/-1.0(syst)]% for B+/--->psi(2S)K+/-.

Design, performance and status of the CLEO III silicon detector

Abstract The CLEO III silicon detector is part of a general upgrade of the CLEO detector to allow for operation at a luminosity of 2×10 33 cm −2 s −1 , which will be provided by the Cornell Electron–Positron Storage Ring (CESR) beginning in 1999. The silicon detector is a four-layer barrel design covering radii from 2.5 to 10.2 cm with 93% solid angle coverage. The silicon sensors are DC-coupled and double-sided with double-metal readout on the p-side. The n-type strips measure φ , with 50 μ m pitch while the p-type strips measure z , the coordinate along the beam axis, with 100 μ m pitch. The readout electronics are mounted on BeO hybrids attached to the conical support structure and connected to the silicon sensors via a thin kapton flex cable. The electronics consist of an R / C chip with bias resistors and decoupling capacitors, a low-noise preamp/shaper chip and a digitizer/sparsifier chip. Readout is done using VME-based sequencer boards. Production of all detector components is nearing completion and installation of the detector will take place in early 1999.

Radiation-induced surface leakage currents in silicon microstrip detectors

After exposure to X-rays and UV light, we have observed induced leakage currents in silicon microstrip detectors designed for CLEO III. UV measurements have shown that the damage is confined to the Si-SiO/sub 2/ interfacial area. The damage is manifested only as a leakage current without additional 1/f noise or significant changes to detector parameters. The scaled damage rate is measured to be 5/spl plusmn/1 nA/cm/sup 2//kRad for 20 keV X-rays.

THE CLEO III SILICON TRACKER

Abstract The Cornell Electron Storage Ring is being upgraded to B-factory luminosities. The CLEO detector is also being upgraded with a new charged particle tracking system and with the addition of a ring imaging Cerenkov particle identification system. A major part of the tracking system upgrade is the construction of a new four-layer double-sided silicon tracker with 93% solid angle coverage and new readout electronics. The status of the silicon tracker including production tests and the expected performance of the final system are discussed.

Design and initial performance of the CLEO III silicon tracker

Abstract CLEO III is the new experimental phase of the CLEO experiment at the CESR accelerator. Both the accelerator and the detector have recently been upgraded. A new charged particle tracking system with the addition of a ring imaging Cherenkov particle identification system has been installed. A major part of the tracking system upgrade was the construction of a new four-layer double-sided silicon tracker with 93% solid angle coverage and new readout electronics. The CLEO III upgrade was completed in February 2000 with the installation of the silicon detector. CLEO III has finished the commissioning phase and is now taking data. The design of the detector and first performance results are presented here.

Study of the B0 semileptonic decay spectrum at the Y(4S) resonance

We have made a first measurement of the lepton momentum spectrum in a sample of events enriched in neutral Bs through a partial reconstruction of B{sup 0} {yields} D*{sup -}{ell}{sup +}{nu}. This spectrum, measured with 2.38 fb{sup -1} of data collected at the {Upsilon}(4S) resonance by the CLEO II detector, is compared directly to the inclusive lepton spectrum from all {Upsilon}(4S) events in the same data set. These two spectra are consistent with having the same shape above 1.5 GeV/c. From the two spectra and two other CLEO measurements, we obtain the B{sup 0} and B{sup +} semileptonic branching fractions, b{sub 0} and b{sub +}, their ratio, and the production ratio f{sub +-}/f{sub 00} of B{sup +} and B{sup 0} pairs at the {Upsilon}(4S). We report b{sub +}/b{sub 0} = 0.950{sub -0.080}{sup +0.117} {+-} 0.091, b{sub 0} = (10.78 {+-} 0.60 {+-} 0.69)%, and b{sub +} = (10.25 {+-} 0.57 {+-} 0.65)%. b{sub +}/b{sub 0} is equivalent to the ratio of charged to neutral B lifetimes, {tau}{sub +}/{tau}{sub 0}.

Observation of the Decay D s + → ωπ +

Using e{sup +}e{sup {minus}} annihilation data collected by the CLEOII detector at CESR, we have observed the decay D{sup +}{sub s}{r_arrow}{omega}{pi}{sup +} . This final state may be produced through the annihilation decay of the D{sup +}{sub s} , or through final state interactions. We find a branching ratio of {Gamma}(D{sup +}{sub s}{r_arrow}{omega}{pi}{sup +})/{Gamma}(D{sup +}{sub s}{r_arrow} {eta}{pi}{sup +})=0.16{plus_minus}0.04{plus_minus}0 .03 , where the first error is statistical and the second is systematic. {copyright} {ital 1997} {ital The American Physical Society}Using e+e- annihilation data collected by the CLEO~II detector at CESR, we have observed the decay Ds+ to omega pi+. This final state may be produced through the annihilation decay of the Ds+, or through final state interactions. We find a branching ratio of [Gamma(Ds+ to omega pi+)/Gamma(Ds+ to eta pi+)]=0.16+-0.04+-0.03, where the first error is statistical and the second is systematic.

Optimization of silicon microstrip detector design for the CLEOIII vertex detector

We present measurements from prototype silicon microstrip detectors for the CLEOIII silicon vertex detector. Noise and capacitance optimization is discussed. We also present a design to achieve 10pF total capacitance on a double sided, double metal silicon detector.

Status of the CLEO III silicon tracker

Abstract The CLEO-III silicon vertex detector is a 4-layer device with double-sided silicon sensors arranged in a barrel design, covering 93% of the solid angle. After initially meeting its design goals of signal-to-noise performance and spatial resolution, the signal efficiency deteriorated on the rφ sensor side in the two innermost layers due to radiation induced sensor effects. Operation of the two outermost layers and the z -coordinate readout in all layers is stable.