6,430 research outputs found
Agame-theoretical approach to network capacity planning under competition
The paper discusses the dimensioning strategies of two network providers (operators) that supply channels to the same population of users in a competitive environment. Usersare assumed to compete for best service (lowest blocking probability of new request), while operators wishto maximize their profits. This setting gives rise to two interconnected, noncooperative games: a) a users game, in which the partition of primary traffic between operators is determined by the operators' channel capacities and by the users' blocking-avoidance strategy; and b) a network dimensioning game between operators in which the players alternate dimensioning decisions thatmaximize their profit rate under the current channel capacity of his/her opponent. At least for two plausible users' blocking avoidance strategies discussed in the paper, the users game will always reach some algorithmic equilibrium. In the operators' game, the player strategies are given by their numbers of deployed chanels, limited by their available infrastructure resources. If the infrastrucutre is under-dimensioned with respect to the traffic rate, the operators game willreach a Nash equilibrium when both players reach full use of their available infrastructures. Otherweise, a Nash equilibrium may also arise if both operators incur the same deployment costs. If costs are asymmetric, though, the alternating game may enter a loop. If the asymmetry is modest, both players may then try to achieve a competitive monopoly in which the opponent is forced to leave the game or operate with a loss (negative profit). However, if the asymmetry is high enough, only the player with the lower costs can force his opponent to leave the game while still holding a profitable operation. --network dimensioning,game theory,duopoly,Nash equilibrium,circuit switching,blocking probability
Radiation Damage Studies of Silicon Photomultipliers
We report on the measurement of the radiation hardness of silicon
photomultipliers (SiPMs) manufactured by
Fondazione Bruno Kessler in Italy (1 mm and 6.2 mm), Center of
Perspective Technology and Apparatus in Russia (1 mm and 4.4 mm), and
Hamamatsu Corporation in Japan (1 mm). The SiPMs were irradiated using a
beam of 212 MeV protons at Massachusetts General Hospital, receiving fluences
of up to protons per cm with the SiPMs at operating
voltage. Leakage currents were read continuously during the irradiation. The
delivery of the protons was paused periodically to record scope traces in
response to calibrated light pulses to monitor the gains, photon detection
efficiencies, and dark counts of the SiPMs. The leakage current and dark noise
are found to increase with fluence. Te leakage current is found to be
proportional to the mean square deviation of the noise distribution, indicating
the dark counts are due to increased random individual pixel activation, while
SiPMs remain fully functional as photon detectors. The SiPMs are found to
anneal at room temperature with a reduction in the leakage current by a factor
of 2 in about 100 days.Comment: 35 pages, 25 figure
Extraction of electric field in heavily irradiated silicon pixel sensors
A new method for the extraction of the electric field in the bulk of heavily
irradiated silicon pixel sensors is presented. It is based on the measurement
of the Lorentz deflection and mobility of electrons as a function of depth. The
measurements were made at the CERN H2 beam line, with the beam at a shallow
angle with respect to the pixel sensor surface. The extracted electric field is
used to simulate the charge collection and the Lorentz deflection in the pixel
sensor. The simulated charge collection and the Lorentz deflection is in good
agreement with the measurements both for non-irradiated and irradiated up to
1E15 neq/cm2 sensors.Comment: 6 pages, 11 figures, presented at the 13th International Workshop on
Vertex Detectors for High Energy Physics, September 13-18, 2004,
Menaggio-Como, Italy. Submitted to Nucl. Instr. Meth.
Simulation of Heavily Irradiated Silicon Pixel Detectors
We show that doubly peaked electric fields are necessary to describe
grazing-angle charge collection measurements of irradiated silicon pixel
sensors. A model of irradiated silicon based upon two defect levels with
opposite charge states and the trapping of charge carriers can be tuned to
produce a good description of the measured charge collection profiles in the
fluence range from 0.5x10^{14} Neq/cm^2 to 5.9x10^{14} Neq/cm^2. The model
correctly predicts the variation in the profiles as the temperature is changed
from -10C to -25C. The measured charge collection profiles are inconsistent
with the linearly-varying electric fields predicted by the usual description
based upon a uniform effective doping density. This observation calls into
question the practice of using effective doping densities to characterize
irradiated silicon. The model is now being used to calibrate pixel hit
reconstruction algorithms for CMS.Comment: Invited talk at International Symposium on the Development of
Detectors for Particle, AstroParticle and Synchrtron Radiation Experiments,
Stanford Ca (SNIC06) 8 pages, LaTeX, 11 eps figure
Light Neutralinos in B-Decays
We consider the decays of a -meson into a pair of lightest
supersymmetric particles (LSP) in the minimal supersymmetric standard model. It
is found that the parameter space for light LSP's in the range of 1 GeV can be
appreciably constrained by looking for such decays.Comment: 9 pages, LaTex, 2 figures (hard copies of the figures available from
the Authors on request
Position Dependence of Charge Collection in Prototype Sensors for the CMS Pixel Detector
This paper reports on the sensor R&D activity for the CMS pixel detector.
Devices featuring several design and technology options have been irradiated up
to a proton fluencec of 1E15 n_eq/cm**2 at the CERN PS. Afterward they were
bump bonded to unirradiated readout chips and tested using high energy pions in
the H2 beam line of the CERN SPS. The readout chip allows a non zero suppressed
full analogue readout and therefore a good characterization of the sensors in
terms of noise and charge collection properties. The position dependence of
signal is presented and the differences between the two sensor options are
discussed.Comment: Contribution to the IEEE-NSS Oct. 2003, Portland, OR, USA, submitted
to IEEE-TNS 7 pages, 8 figures, 1 table. Revised, title change
Tests of silicon sensors for the CMS pixel detector
The tracking system of the CMS experiment, currently under construction at
the Large Hadron Collider (LHC) at CERN (Geneva, Switzerland), will include a
silicon pixel detector providing three spacial measurements in its final
configuration for tracks produced in high energy pp collisions. In this paper
we present the results of test beam measurements performed at CERN on
irradiated silicon pixel sensors. Lorentz angle and charge collection
efficiency were measured for two sensor designs and at various bias voltages.Comment: Talk presented at 6th International Conference on Large Scale
Applications and Radiation Hardness of Semiconductor Detectors, September
29-October 1, 2003, Firenze, Italy. Proceedings will be published in Nuclear
Instr. & Methods in Phys. Research, Section
- …