39,029 research outputs found
A Generic Algorithm for IACT Optical Efficiency Calibration using Muons
Muons produced in Extensive Air Showers (EAS) generate ring-like images in
Imaging Atmospheric Cherenkov Telescopes when travelling near parallel to the
optical axis. From geometrical parameters of these images, the absolute amount
of light emitted may be calculated analytically. Comparing the amount of light
recorded in these images to expectation is a well established technique for
telescope optical efficiency calibration. However, this calculation is usually
performed under the assumption of an approximately circular telescope mirror.
The H.E.S.S. experiment entered its second phase in 2012, with the addition of
a fifth telescope with a non-circular 600m mirror. Due to the differing
mirror shape of this telescope to the original four H.E.S.S. telescopes,
adaptations to the standard muon calibration were required. We present a
generalised muon calibration procedure, adaptable to telescopes of differing
shapes and sizes, and demonstrate its performance on the H.E.S.S. II array.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherland
Rubidium resonant squeezed light from a diode-pumped optical-parametric oscillator
We demonstrate a diode-laser-pumped system for generation of quadrature
squeezing and polarization squeezing. Due to their excess phase noise, diode
lasers are challenging to use in phase-sensitive quantum optics experiments
such as quadrature squeezing. The system we present overcomes the phase noise
of the diode laser through a combination of active stabilization and
appropriate delays in the local oscillator beam. The generated light is
resonant to the rubidium D1 transition at 795nm and thus can be readily used
for quantum memory experiments.Comment: 6 pages 4 figure
Nonlinear metrology with a quantum interface
We describe nonlinear quantum atom-light interfaces and nonlinear quantum
metrology in the collective continuous variable formalism. We develop a
nonlinear effective Hamiltonian in terms of spin and polarization collective
variables and show that model Hamiltonians of interest for nonlinear quantum
metrology can be produced in Rb ensembles. With these Hamiltonians,
metrologically relevant atomic properties, e.g. the collective spin, can be
measured better than the "Heisenberg limit" . In contrast to other
proposed nonlinear metrology systems, the atom-light interface allows both
linear and non-linear estimation of the same atomic quantities.Comment: 8 pages, 1 figure
Potential for measuring the longitudinal and lateral profile of muons in TeV air showers with IACTs
Muons are copiously produced within hadronic extensive air showers (EAS)
occurring in the Earth's atmosphere, and are used by particle air shower
detectors as a means of identifying the primary cosmic ray which initiated the
EAS. Imaging Atmospheric Cherenkov Telescopes (IACTs), designed for the
detection of gamma-ray initiated EAS for the purposes of Very High Energy (VHE)
gamma-ray astronomy, are subject to a considerable background signal due to
hadronic EAS. Although hadronic EAS are typically rejected for gamma-ray
analysis purposes, single muons produced within such showers generate clearly
identifiable signals in IACTs and muon images are routinely retained and used
for calibration purposes. For IACT arrays operating with a stereoscopic
trigger, when a muon triggers one telescope, other telescopes in IACT arrays
usually detect the associated hadronic EAS. We demonstrate for the first time
the potential of IACT arrays for competitive measurements of the muon content
of air showers, their lateral distribution and longitudinal profile of
production slant heights in the TeV energy range. Such information can provide
useful input to hadronic interaction models.Comment: 15 pages, 11 figures, 2 tables, accepted for publication in
Astroparticle Physic
LHAASO J2108+5157 as a Molecular Cloud Illuminated by a Supernova Remnant
The search for Galactic PeVatrons - astrophysical accelerators of cosmic rays
to PeV energies - has entered a new phase in recent years with the discovery of
the first Ultra-High-Energy (UHE, TeV) gamma-ray sources by the HAWC
and LHAASO experiments. Establishing whether the emission is leptonic or
hadronic in nature, however, requires multiwavelength data and modelling
studies. Among the currently known UHE sources, LHAASO J2108+5157 is an
enigmatic source without clear association to a plausible accelerator, yet
spatially coincident with molecular clouds. We investigate the scenario of a
molecular cloud illuminated by cosmic rays accelerated in a nearby supernova
remnant (SNR) as an explanation for LHAASO J2108+5157. We aim to constrain the
required properties of the SNR as well as which of the clouds identified in the
vicinity is the most likely association. We use a model for cosmic ray
acceleration in SNRs, their transport through the interstellar medium and
subsequent interaction with molecular material, to predict the corresponding
gamma-ray emission. The parameter space of SNR properties is explored to find
the most plausible parameter combination that can account for the gamma-ray
spectrum of LHAASO J2108+5157. In the case that a SNR is illuminating the
cloud, we find that it must be young ( kyr) and located within pc
of the cloud. A SN scenario with a low Sedov time is preferred, with a maximum
proton energy of 3 PeV assumed. No SNRs matching these properties are currently
known, although an as yet undetected SNR remains feasible. The galactic CR sea
is insufficient to solely account for the observed flux, such that a PeVatron
accelerator must be present in the vicinity.Comment: 7 pages, 4 figures, 3 tables. Accepted for publication in A&
Rotation of Coulomb crystals in a magnetized inductively coupled complex plasma
Under suitable conditions, micron-sized dust particles introduced into inductively coupled argon plasma form a stable microscopic crystal lattice, known as a Coulomb (or plasma) crystal. In the experiment described, an external axial magnetic field was applied to various configurations of Coulomb crystal, including small crystal lattices consisting of one to several particles, and large crystal lattices with many hundreds of particles. The crystals were observed to rotate collectively under the influence of the magnetic field. This paper describes the experimental procedures and the preliminary results of this investigation
Diagnosis, prescription and prognosis of a Bell-state filter by quantum process tomography
Using a Hong-Ou-Mandel interferometer, we apply the techniques of quantum
process tomography to characterize errors and decoherence in a prototypical
two-photon operation, a singlet-state filter. The quantum process tomography
results indicate a large asymmetry in the process and also the required
operation to correct for this asymmetry. Finally, we quantify errors and
decoherence of the filtering operation after this modification.Comment: 4 pages, 4 figure
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