26,662 research outputs found
Particle identification with the AMS-02 RICH detector: search for dark matter with antideuterons
The Alpha Magnetic Spectrometer (AMS), whose final version AMS-02 is to be
installed on the International Space Station (ISS) for at least 3 years, is a
detector designed to measure charged cosmic ray spectra with energies up to the
TeV region and with high energy photon detection capability up to a few hundred
GeV, using state-of-the art particle identification techniques. It is equipped
with several subsystems, one of which is a proximity focusing Ring Imaging
Cherenkov (RICH) detector equipped with a dual radiator (aerogel+NaF), a
lateral conical mirror and a detection plane made of 680 photomultipliers and
light guides, enabling precise measurements of particle electric charge and
velocity (Delta beta / beta ~ 10^-3 and 10^-4 for Z=1 and Z=10-20,
respectively) at kinetic energies of a few GeV/nucleon. Combining velocity
measurements with data on particle rigidity from the AMS-02 Tracker (Delta R /
R ~ 2% for R=1-10 GV) it is possible to obtain a reliable measurement for
particle mass. One of the main topics of the AMS-02 physics program is the
search for indirect signatures of dark matter. Experimental data indicate that
dark, non-baryonic matter of unknown composition is much more abundant than
baryonic matter, accounting for a large fraction of the energy content of the
Universe. Apart from antideuterons produced in cosmic-ray propagation, the
annihilation of dark matter will produce additional antideuteron fluxes.
Detailed Monte Carlo simulations of AMS-02 have been used to evaluate the
detector's performance for mass separation, a key issue for anti-D/anti-p
separation. Results of these studies are presented.Comment: 5 pages. Contribution to the 20th European Cosmic Ray Symposium
(Lisbon 2006). Presenter: Rui Pereir
Active vision for dexterous grasping of novel objects
How should a robot direct active vision so as to ensure reliable grasping? We
answer this question for the case of dexterous grasping of unfamiliar objects.
By dexterous grasping we simply mean grasping by any hand with more than two
fingers, such that the robot has some choice about where to place each finger.
Such grasps typically fail in one of two ways, either unmodeled objects in the
scene cause collisions or object reconstruction is insufficient to ensure that
the grasp points provide a stable force closure. These problems can be solved
more easily if active sensing is guided by the anticipated actions. Our
approach has three stages. First, we take a single view and generate candidate
grasps from the resulting partial object reconstruction. Second, we drive the
active vision approach to maximise surface reconstruction quality around the
planned contact points. During this phase, the anticipated grasp is continually
refined. Third, we direct gaze to improve the safety of the planned reach to
grasp trajectory. We show, on a dexterous manipulator with a camera on the
wrist, that our approach (80.4% success rate) outperforms a randomised
algorithm (64.3% success rate).Comment: IROS 2016. Supplementary video: https://youtu.be/uBSOO6tMzw
Particle identification with the AMS-02 RICH detector: D/p and anti-D/anti-p separation
The Alpha Magnetic Spectrometer (AMS), whose final version AMS-02 is to be
installed on the International Space Station (ISS) for at least 3 years, is a
detector designed to measure charged cosmic ray spectra with energies up to the
TeV region and with high energy photon detection capability up to a few hundred
GeV, using state-of-the art particle identification techniques. Among several
detector subsystems, AMS includes a proximity focusing RICH enabling precise
measurements of particle electric charge and velocity. The combination of both
these measurements together with the particle rigidity measured on the silicon
tracker endows a reliable measurement of the particle mass. The main topics of
the AMS-02 physics program include detailed measurements of the nuclear
component of the cosmic-ray spectrum and the search for indirect signatures of
dark matter. Mass separation of singly charged particles, and in particular the
separation of deuterons and antideuterons from massive backgrounds of protons
and antiprotons respectively, is essential in this context. Detailed Monte
Carlo simulations of AMS-02 have been used to evaluate the detector's
performance for mass separation at different energies. The obtained results and
physics prospects are presented.Comment: 5 pages. Contribution to the Sixth International Workshop on New
Worlds in Astroparticle Physics (Faro 2007). Presenter: Rui Pereir
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