Antimatter search results of the Alpha Magnetic Spectrometer (AMS) detector are presented. About 10
8 triggers were collected in the 1998 precursor flight onboard space shuttle
Discovery. This ten ...day mission exposed the detector on a 51.7° orbit at an altitude around 350km. Identification of charged cosmic rays is achieved by multiple energy loss and time-of-flight measurements. Bending inside the 0.15T magnetic volume yields a measurement of the absolute value of the particle's rigidity. The supplemental knowledge of the sense of traversal identifies the sign of the charge. In the rigidity range 1 <
R < 140 GV no antinucleus at any rigidity was detected, while 2.86 × 10
6 helium and 1.65 × 10
5 heavy nuclei were precisely measured. Hence, upper limits on the flux ratio
Z/Z
are given. Different prior assumptions on the antimatter spectrum are considered and corresponding limits are given.
Antimatter searches with AMS Cristinziani, Markus
Nuclear physics. Section B, Proceedings supplement,
12/2002, Letnik:
113, Številka:
1
Journal Article
A search for antimatter with the Alpha Magnetic Spectrometer (AMS) is presented. The detector was flown for a ten day mission in 1998 on a 51.7° orbit at an altitude around 350km onboard space ...shuttle
Discovery. Identification of nuclei is ensured through multiple energy loss and time-of-flight measurements. The rigidity is obtained by the measurement of the bending inside the 0.15T magnetic volume. 2.86 × 10
6 helium and 1.65 × 10
5 heavy nuclei have been precisely measured in a rigidity range 1 <
R < 140 GV, while no antinucleus at any rigidity were detected. Upper limits on the flux ratio
Z
/
Z are given which are independent on the incident spectrum.
To improve the understanding of accelerator-induced backgrounds at the SLAC B-Factory, we simulate lost particle backgrounds in the BABAR detector originating from beam-gas interactions and radiative ...Bhabha scatters. We have extended the GEANT4-based BABAR detector simulation to include beam-line components and magnetic fields up to 8.5 m away from the interaction point. We describe the simulation model and then compare preliminary predicted background levels with measurements from dedicated single-and colliding-beam experiments.
We report measurements of
Ξ
− and
Ξ
+
hyperon absolute yields as a function of rapidity in 158 GeV/c Pb+Pb collisions. At midrapidity,
dN/
dy=2.29±0.12 for
Ξ
−, and 0.52±0.05 for
Ξ
+
, leading to the ...ratio of
Ξ
+/Ξ
−=0.23±0.03
. Inverse slope parameters fitted to the measured transverse mass spectra are of the order of
T≈300 MeV near mid-rapidity. The estimated total yield of
Ξ
− particles in Pb+Pb central interactions amounts to 7.4±1.0 per collision. Comparison to
Ξ
− production in properly scaled p+p reactions at the same energy reveals a dramatic enhancement (about one order of magnitude) of
Ξ
− production in Pb+Pb central collisions over elementary hadron interactions.
Diamond has been developed as a material for the detection of charged particles by ionization. Its radiation hardness makes it an attractive material for detectors operated in a harsh radiation ...environment e.g. close to a particle beam as is the case for beam monitoring and for pixel vertex detectors. Poly-crystalline chemical vapor deposition (CVD) diamond has been studied as strip and pixel detectors so far. We report on a first-time characterization of a single-crystal diamond pixel detector in a 100 GeV particle beam at CERN. The detectors are made from irregularly shaped single crystal sensors, 395mm thick, mated by bump bonding to a front-end readout IC as used in the ATLAS pixel detector with pixel sizes of 50 x 400 mm2. The diamond sensors show excellent charge collection properties: full collection over the entire detector volume, clean and narrow signal charge distributions with a S/N value of >100 and a hit detection efficiency of (99.9 +- 0.1)%. The measured spatial resolution for particles under normal incidence in the shorter pixel direction is (8.9 +- 0.1) um.
The ATLAS pixel detector Cristinziani, M; for the ATLAS Pixel Collaboration
arXiv.org,
03/2007
Paper
Odprti dostop
After a ten years planning and construction phase, the ATLAS pixel detector is nearing its completion and is scheduled to be integrated into the ATLAS detector to take data with the first LHC ...collisions in 2007. An overview of the construction is presented with particular emphasis on some of the major and most recent problems encountered and solved.
3D silicon detectors are characterized by cylindrical electrodes perpendicular to the surface and penetrating into the bulk material in contrast to standard Si detectors with planar electrodes on its ...top and bottom. This geometry renders them particularly interesting to be used in environments where standard silicon detectors have limitations, such as for example the radiation environment expected in an LHC upgrade. For the first time, several 3D sensors were assembled as hybrid pixel detectors using the ATLAS-pixel front-end chip and readout electronics. Devices with different electrode configurations have been characterized in a 100 GeV pion beam at the CERN SPS. Here we report results on unirradiated devices with three 3D electrodes per 50 x 400 um2 pixel area. Full charge collection is obtained already with comparatively low bias voltages around 10 V. Spatial resolution with binary readout is obtained as expected from the cell dimensions. Efficiencies of 95.9% +- 0.1 % for tracks parallel to the electrodes and of 99.9% +- 0.1 % at 15 degrees are measured. The homogeneity of the efficiency over the pixel area and charge sharing are characterized.
PDF
![Ξ and [formula omitted] pro...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0370-2693/small "Ξ and [formula omitted] production in 158 GeV/nucleon Pb+Pb collisions")
