18,784 research outputs found
Comparison of available measurements of the absolute air-fluorescence yield and determination of its global average value
Experimental results of the absolute air-fluorescence yield are given very
often in different units (photons/MeV or photons/m) and for different
wavelength intervals. In this work we present a comparison of available results
normalized to its value in photons/MeV for the 337 nm band at 1013 hPa and 293
K. The conversion of photons/m to photons/MeV requires an accurate
determination of the energy deposited by the electrons in the field of view of
the experimental set-up. We have calculated the energy deposition for each
experiment by means of a detailed Monte Carlo simulation and the results have
been compared with those assumed or calculated by the authors. As a result,
corrections to the reported fluorescence yields are proposed. These corrections
improve the compatibility between measurements in such a way that a reliable
average value with uncertainty at the level of 5% is obtained.Comment: 13 pages, 6 figures. To appear in the Proocedings of the
International Symposium on the Recent Progress of Ultra-high Energy Cosmic
Ray Observations (UHECR2010), Nagoya, Japan, 201
On the absolute value of the air-fluorescence yield
The absolute value of the air-fluorescence yield is a key parameter for the
energy reconstruction of extensive air showers registered by fluorescence
telescopes. In previous publications, we reported a detailed Monte Carlo
simulation of the air-fluorescence generation that allowed the theoretical
evaluation of this parameter. This simulation has been upgraded in the present
work. As a result, we determined an updated absolute value of the fluorescence
yield of 7.9+-2.0 ph/MeV for the band at 337 nm in dry air at 800 hPa and 293
K, in agreement with experimental values. We have also performed a critical
analysis of available absolute measurements of the fluorescence yield with the
assistance of our simulation. Corrections have been applied to some
measurements to account for a bias in the evaluation of the energy deposition.
Possible effects of other experimental aspects have also been discussed. From
this analysis, we determined an average fluorescence yield of 7.04+-0.24 ph/MeV
at the above conditions.Comment: Submitted to Astroparticle Physic
Improved model for the analysis of air fluorescence induced by electrons
A model recently proposed for the calculation of air-fluorescence yield
excited by electrons is revisited. Improved energy distributions of secondary
electrons and a more realistic Monte Carlo simulation including some additional
processes have allowed us to obtain more accurate results. The model is used to
study in detail the relationship between fluorescence intensity and deposited
energy in a wide range of primary energy (keVs - GeVs). In addition,
predictions on the absolute value of the fluorescence efficiency in the absence
of collisional quenching will be presented and compared with available
experimental data.Comment: Contribution to the 5th Fluorescence Workshop, El Escorial, Madrid,
Spain, September 2007, to appear in Nuclear Instruments and Methods A.
Revised version.- More details on the comparison with experimental dat
The ALICE electromagnetic calorimeter high level triggers
The ALICE (A Large Ion Collider Experiment) detector yields a huge sample of
data from different sub-detectors. On-line data processing is applied to select
and reduce the volume of the stored data. ALICE applies a multi-level hardware
trigger scheme where fast detectors are used to feed a three-level (L0, L1, and
L2) deep chain. The High-Level Trigger (HLT) is a fourth filtering stage
sitting logically between the L2 trigger and the data acquisition event
building. The EMCal detector comprises a large area electromagnetic calorimeter
that extends the momentum measurement of photons and neutral mesons up to
GeV/c, which improves the ALICE capability to perform jet
reconstruction with measurement of the neutral energy component of jets. An
online reconstruction and trigger chain has been developed within the HLT
framework to sharpen the EMCal hardware triggers, by combining the central
barrel tracking information with the shower reconstruction (clusters) in the
calorimeter. In the present report the status and the functionality of the
software components developed for the EMCal HLT online reconstruction and
trigger chain will be discussed, as well as preliminary results from their
commissioning performed during the 2011 LHC running period.Comment: Proceeding for the CHEP 2012 Conferenc
Does the unemployment benefit institution affect the productivity of workers? Evidence from a field experiment
We investigate whether and how the type of unemployment benefit institution affects
productivity. We designed a field experiment to compare workers' productivity under a
welfare system, where the unemployed receive an unconditional monetary transfer, with
their productivity under a workfare system, where the transfer is received conditional
on the unemployed spending some time on ancillary activities. First, we find that
having an unemployment benefit institution, regardless of whether it makes transfers
conditional or unconditional, increases workers' productivity. Second, we find that
productivity is higher under Welfare than under Workfare. Becoming unemployed
under Welfare comes at the psychological cost of a drop in self-esteem, presumably
due to the shame or stigma associated with receiving an unconditional unemployment
benefit. We document the empirical relevance of precisely this channel. The differences
we observe in productivity suggest that this psychological cost acts as an extra nonmonetary
incentive for workers under Welfare to put a higher effort in their work
Experimental determination of air fluorescence yield from low-energy electrons (LEEAF experiment)
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