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Readout of TPC Tracking Chambers with GEMs and Pixel Chip
Two layers of GEMs and the ATLAS Pixel Chip, FEI3, have been combined and tested as a prototype for Time Projection Chamber (TPC) readout at the International Linear Collider (ILC). The double-layer GEM system amplifies charge with gain sufficient to detect all track ionization. The suitability of three gas mixtures for this application was investigated, and gain measurements are presented. A large sample of cosmic ray tracks was reconstructed in 3D by using the simultaneous timing and 2D spatial information from the pixel chip. The chip provides pixel charge measurement as well as timing. These results demonstrate that a double GEM and pixel combination, with a suitably modified pixel ASIC, could meet the stringent readout requirements of the ILC
Heliolatitude and time variations of solar wind structure from in situ measurements and interplanetary scintillation observations
The 3D structure of solar wind and its evolution in time is needed for
heliospheric modeling and interpretation of energetic neutral atoms
observations. We present a model to retrieve the solar wind structure in
heliolatitude and time using all available and complementary data sources. We
determine the heliolatitude structure of solar wind speed on a yearly time grid
over the past 1.5 solar cycles based on remote-sensing observations of
interplanetary scintillations, in situ out-of-ecliptic measurements from
Ulysses, and in situ in-ecliptic measurements from the OMNI-2 database. Since
the in situ information on the solar wind density structure out of ecliptic is
not available apart from the Ulysses data, we derive correlation formulae
between solar wind speed and density and use the information on the solar wind
speed from interplanetary scintillation observations to retrieve the 3D
structure of solar wind density. With the variations of solar wind density and
speed in time and heliolatitude available we calculate variations in solar wind
flux, dynamic pressure and charge exchange rate in the approximation of
stationary H atoms.Comment: Accepted for publication in Solar Physic
Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events
The - oscillation frequency has been measured with a sample of
23 million \B\bar B pairs collected with the BABAR detector at the PEP-II
asymmetric B Factory at SLAC. In this sample, we select events in which both B
mesons decay semileptonically and use the charge of the leptons to identify the
flavor of each B meson. A simultaneous fit to the decay time difference
distributions for opposite- and same-sign dilepton events gives ps.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
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