3,952 research outputs found
Measurement of air and nitrogen fluorescence light yields induced by electron beam for UHECR experiments
Most of the Ultra High Energy Cosmic Ray (UHECR) experiments and projects
(HiRes, AUGER, TA, EUSO, TUS,...) use air fluorescence to detect and measure
extensive air showers (EAS). The precise knowledge of the Fluorescence Light
Yield (FLY) is of paramount importance for the reconstruction of UHECR. The
MACFLY - Measurement of Air Cherenkov and Fluorescence Light Yield - experiment
has been designed to perform such FLY measurements. In this paper we will
present the results of FLY in the 290-440 nm wavelength range for dry air and
pure nitrogen, both excited by electrons with energy of 1.5 MeV, 20 GeV and 50
GeV. The experiment uses a 90Sr radioactive source for low energy measurement
and a CERN SPS electron beam for high energy. We find that the FLY is
proportional to the deposited energy (E_d) in the gas and we show that the air
fluorescence properties remain constant independently of the electron energy.
At the reference point: atmospheric dry air at 1013 hPa and 23C, the ratio
FLY/E_d=17.6 photon/MeV with a systematic error of 13.2%.Comment: 19 pages, 8 figures. Accepted for publication in Astroparticle
Physic
Measurement of intracellular concentration of fluorescently-labeled targets in living cells
Estimations of intracellular concentrations of fluorescently-labeled molecules within living cells are very important for guidance of biological experiments and interpretation of their results. Here we propose a simple and universal approach for such estimations. The approach is based upon common knowledge that the dye fluorescence is directly proportional to its quantum yield and the number of its molecules and that a coefficient of proportionality is determined by spectral properties of the dye and optical equipment used to record fluorescent signals. If two fluorescent dyes are present in the same volume, then a ratio of their concentrations is equal to a ratio of their fluorescence multiplied by some dye- and equipment-dependent coefficient. Thus, if the coefficient and concentration of one dye is known then the concentration of another dye can be determined. Here we have demonstrated how to calculate this coefficient (called a ratio factor) and how to use it for concentration measurements of fluorescently tagged molecules. As an example of how this approach can be used, we estimated a concentration of exogenously expressed neuronal Ca2+ sensor protein, hippocalcin, tagged by a fluorescent protein in a dendritic tree of rat hippocampal neurons loaded via a patch pipette with Alexa Fluor dye of known concentration. The new approach should allow performing a fast, inexpensive and reliable quantitative analysis of fluorescently-labeled targets in different parts of living cells
Tunka Advanced Instrument for cosmic rays and Gamma Astronomy
The paper is a script of a lecture given at the ISAPP-Baikal summer school in
2018. The lecture gives an overview of the Tunka Advanced Instrument for cosmic
rays and Gamma Astronomy (TAIGA) facility including historical introduction,
description of existing and future setups, and outreach and open data
activities.Comment: Lectures given at the ISAPP-Baikal Summer School 2018: Exploring the
Universe through multiple messengers, 12-21 July 2018, Bol'shie Koty, Russi
Transverse polarization in inclusive quasi-real photoproduction at the current fragmentation
It is shown that the recent HERMES data on the transverse
polarization in the inclusive quasi-real photoproduction at can be
accommodated by the strange quark scattering model. Relations with the quark
recombination approach are discussed.Comment: 5 pages, 3 figures, accepted by Eur. Phys. J.
An extensive-air-shower-like event registered with the TUS orbital detector
TUS (Tracking Ultraviolet Set-up) is the world's first orbital detector of
ultra-high-energy cosmic rays (UHECRs). It was launched into orbit on 28th
April 2016 as a part of the scientific payload of the Lomonosov satellite. The
main aim of the mission was to test the technique of measuring the ultraviolet
fluorescence and Cherenkov radiation of extensive air showers generated by
primary cosmic rays with energies above ~100 EeV in the Earth atmosphere from
space. During its operation for 1.5 years, TUS registered almost 80,000 events
with a few of them satisfying conditions anticipated for extensive air showers
(EASs) initiated by UHECRs. Here we discuss an event registered on 3rd October
2016. The event was measured in perfect observation conditions as an
ultraviolet track in the nocturnal atmosphere of the Earth, with the kinematics
and the light curve similar to those expected from an EAS. A reconstruction of
parameters of a primary particle gave the zenith angle around 44 but an
extreme energy not compatible with the cosmic ray energy spectrum obtained with
ground-based experiments. We discuss in details all conditions of registering
the event, explain the reconstruction procedure and its limitations and comment
on possible sources of the signal, both of anthropogenic and astrophysical
origin. We believe this detection represents a significant milestone in the
space-based observation of UHECRs because it proves the capability of an
orbital telescope to detect light signals with the apparent motion and light
shape similar to what are expected from EASs. This is important for the
on-going development of the future missions KLYPVE-EUSO and POEMMA, aimed for
studying UHECRs from space.Comment: 24 pages; v2: important changes to address comments by the anonymous
referee; main conclusions unchange
Nuclear Polarization of Molecular Hydrogen Recombined on a Non-metallic Surface
The nuclear polarization of molecules formed by recombination
of nuclear polarized H atoms on the surface of a storage cell initially coated
with a silicon-based polymer has been measured by using the longitudinal
double-spin asymmetry in deep-inelastic positron-proton scattering. The
molecules are found to have a substantial nuclear polarization, which is
evidence that initially polarized atoms retain their nuclear polarization when
absorbed on this type of surfac
Measurements of and Production in + Collisions at = 200 GeV
We report measurements of charmed-hadron (, ) production cross
sections at mid-rapidity in + collisions at a center-of-mass energy of
200 GeV by the STAR experiment. Charmed hadrons were reconstructed via the
hadronic decays , and their charge conjugates,
covering the range of 0.62.0 GeV/ and 2.06.0 GeV/ for
and , respectively. From this analysis, the charm-pair production cross
section at mid-rapidity is = 170 45
(stat.) (sys.) b. The extracted charm-pair cross section is
compared to perturbative QCD calculations. The transverse momentum differential
cross section is found to be consistent with the upper bound of a Fixed-Order
Next-to-Leading Logarithm calculation.Comment: 15 pages, 16 figures. Revised version submitted to Phys. Rev.
Studies of di-jet survival and surface emission bias in Au+Au collisions via angular correlations with respect to back-to-back leading hadrons
We report first results from an analysis based on a new multi-hadron
correlation technique, exploring jet-medium interactions and di-jet surface
emission bias at RHIC. Pairs of back-to-back high transverse momentum hadrons
are used for triggers to study associated hadron distributions. In contrast
with two- and three-particle correlations with a single trigger with similar
kinematic selections, the associated hadron distribution of both trigger sides
reveals no modification in either relative pseudo-rapidity or relative
azimuthal angle from d+Au to central Au+Au collisions. We determine associated
hadron yields and spectra as well as production rates for such correlated
back-to-back triggers to gain additional insights on medium properties.Comment: By the STAR Collaboration. 6 pages, 2 figure
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