685 research outputs found
Entanglement of orbital angular momentum states between an ensemble of cold atoms and a photon
Recently, atomic ensemble and single photons were successfully entangled by
using collective enhancement [D. N. Matsukevich, \textit{et al.}, Phys. Rev.
Lett. \textbf{95}, 040405(2005).], where atomic internal states and photonic
polarization states were correlated in nonlocal manner. Here we experimentally
clarified that in an ensemble of atoms and a photon system, there also exists
an entanglement concerned with spatial degrees of freedom. Generation of
higher-dimensional entanglement between remote atomic ensemble and an
application to condensed matter physics are also discussed.Comment: 5 pages, 3 figure
Evidence for a source size of less than 2000 AU in Quasar 2237+0305
Recently, OGLE team have reported clear quasar microlensing signal in
Q2237+0305. We have analyzed the microlens event of ``image C'' by using their
finely and densely sampled lightcurves. From lightcurve fitting, we can
unambiguously set the source size of \lsim 0.98 Einstein Ring radius as a
conservative limit. This limit corresponds to , if we adopt
obtained by a recent statistical study of
mean mass of lens object. This gives a clear evidence for the existence of an
accretion disk in the central region of the quasar.Comment: 11 pages, including 1 table and 3 figures, accepted to ApJ
An X-Ray Microlensing Test of AU-Scale Accretion Disk Structure in Q2237+0305
The innermost regions of quasars can be resolved by a gravitational-lens
{\lq}telescope{\rq} on scales down to a few AU. For the purpose, X-ray
observations are most preferable, because X-rays originating from the innermost
regions, can be selectively amplified by microlensing due to the so-called
`caustic crossing'. If detected, X-ray variations will constrain the size of
the X-ray emitting region down to a few AU. The maximum attainable resolution
depends mainly on the monitoring intervals of lens events, which should be much
shorter than the crossing time. On the basis of this idea, we performe
numerical simulations of microlensing of an optically-thick, standard-type disk
as well as an optically-thin, advection-dominated accretion flow (ADAF).
Calculated spectral variations and light curves show distinct behaviors,
depending on the photon energy. X-ray radiation which is produced in optically
thin region, exhibits intensity variation over a few tens of days. In contrast,
optical-UV fluxes, which are likely to come from optically thick region,
exhibit more gradual light changes, which is consistent with the microlensing
events so far observed in Q2237+0305.
Currently, Q2237+0305 is being monitored in the optical range at Apache Point
Observatory. Simultaneous multi-wavelength observations by X-ray sattelites
(e.g., ASCA, AXAF, XMM) as well as HST at the moment of a microlens event
enable us to reveal an AU scale structure of the central accretion disk around
black hole.Comment: 10 pages LaTeX, 3 figures, accepted to ApJ Letter. e-mail:
[email protected]
NuMI Beam Monitoring Simulation and Data Analysis Status and Progress
With the Main Injector Neutrino Oscillation Search (MINOS) experiment decommissioned, muon and hadron monitors became an important diagnostic tool for the NuMI Off-axis v Appearance (NOvA) experiment at Fermilab to monitor the Neutrinos at the Main Injector (NuMI) beam. The goal of this study is to maintain the quality of the monitor signals and to establish correlations with the neutrino beam profile. And we carry out a systematic study of the response of the muon monitors to the changes in the parameters of the proton beam and lattice parameters. We report here on the progress of the beam data analysis and comparison with the simulation results
The Influence of Gravitational Microlensing on the Broad Emission Lines of Quasars
We discuss the effects of microlensing on the broad emission lines (BELs) of
QSOs in the light of recent determinations of the size of the broad line region
(BLR) and its scaling with QSO luminosity. Microlensing by star-sized objects
can produce significant amplifications in the BEL of some multiple-imaged QSOs,
and could be very relevant for high-ionization lines. We have identified a
group of ten gravitational lens systems (30% of the selected sample) in which
microlensing could be observed. Using standard kinematic models for AGNs, we
have studied the changes induced in the line profile by a microlens located at
different positions with respect to the center of the BLR. We found that
microlensing could produce important effects such as the relative enhancement
of different parts of the line profile or the displacement of the peak of the
line. The study of BEL profiles of different ionization in a microlensed QSO
image could be an alternative method for probing the BLR structure and size.Comment: 41 pages including 20 figures. Accepted for publication in Ap
Pressurized rf cavities in ionizing beams
A muon collider or Higgs factory requires significant reduction of the six dimensional emittance of the beam prior to acceleration. One method to accomplish this involves building a cooling channel using high pressure gas filled radio frequency cavities. The performance of such a cavity when subjected to an intense particle beam must be investigated before this technology can be validated. To this end, a high pressure gas filled radio frequency (rf) test cell was built and placed in a 400 MeV beam line from the Fermilab linac to study the plasma evolution and its effect on the cavity. Hydrogen, deuterium, helium and nitrogen gases were studied. Additionally, sulfur hexafluoride and dry air were used as dopants to aid in the removal of plasma electrons. Measurements were made using a variety of beam intensities, gas pressures, dopant concentrations, and cavity rf electric fields, both with and without a 3 T external solenoidal magnetic field. Energy dissipation per electron-ion pair, electron-ion recombination rates, ion-ion recombination rates, and electron attachment times to SF6 and O-2 were measured.ope
Asymptotic Expansions and Amplification of a Gravitational Lens Near a Fold Caustic
We propose two methods that enable us to obtain approximate solutions of the
lens equation near a fold caustic with an arbitrary degree of accuracy. We
obtain "post-linear" corrections to the well-known formula in the linear
caustic approximation for the total amplification of two critical images of a
point source. In this case, in order to obtain the nontrivial corrections we
had to go beyond the approximation orders earlier used by Keeton et al. and to
take into account the Taylor expansion of the lens equation near caustic up to
the fourth order. Corresponding analytical expressions are derived for the
amplification in cases of the Gaussian and power-law extended source models;
the amplifications depend on three additional fitting parameters. Conditions of
neglecting the correction terms are analysed. The modified formula for the
amplification is applied to the fitting of light curves of the Q2237+0305
gravitational lens system in a vicinity of the high amplification events
(HAEs). We show that the introduction of some "post-linear" corrections reduces
chi^2 by 30% in the case of known HAE on the light curve of image C (1999).
These corrections can be important for a precise comparison of different source
models with regard for observational data. Key words: gravitational lensing:
micro - quasars: individual (Q2237+0305) - gravitational lensing: strong -
methods: analyticalComment: 16 pages, 3 figure
The extinction law in high redshift galaxies
We estimate the dust extinction laws in two intermediate redshift galaxies.
The dust in the lens galaxy of LBQS1009-0252, which has an estimated lens
redshift of zl~0.88, appears to be similar to that of the SMC with no
significant feature at 2175 A. Only if the lens galaxy is at a redshift of
zl~0.3, completely inconsistent with the galaxy colors, luminosity or location
on the fundamental plane, can the data be fit with a normal Galactic extinction
curve. The dust in the zl=0.68 lens galaxy for B0218+357, whose reddened image
lies behind a molecular cloud, requires a very flat ultraviolet extinction
curve with (formally) R(V)=12 +- 2. Both lens systems seem to have unusual
extinction curves by Galactic standards.Comment: 15 pages, 3 figures. ApJ in pres
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