55 research outputs found
Accelerated re-endothelialization and reduced neointimal thickening following catheter transfer of phVEGF165
X-ray harmonic comb from relativistic electron spikes
X-ray devices are far superior to optical ones for providing nanometre
spatial and attosecond temporal resolutions. Such resolution is indispensable
in biology, medicine, physics, material sciences, and their applications. A
bright ultrafast coherent X-ray source is highly desirable, for example, for
the diffractive imaging of individual large molecules, viruses, or cells. Here
we demonstrate experimentally a new compact X-ray source involving high-order
harmonics produced by a relativistic-irradiance femtosecond laser in a gas
target. In our first implementation using a 9 Terawatt laser, coherent soft
X-rays are emitted with a comb-like spectrum reaching the 'water window' range.
The generation mechanism is robust being based on phenomena inherent in
relativistic laser plasmas: self-focusing, nonlinear wave generation
accompanied by electron density singularities, and collective radiation by a
compact electric charge. The formation of singularities (electron density
spikes) is described by the elegant mathematical catastrophe theory, which
explains sudden changes in various complex systems, from physics to social
sciences. The new X-ray source has advantageous scalings, as the maximum
harmonic order is proportional to the cube of the laser amplitude enhanced by
relativistic self-focusing in plasma. This allows straightforward extension of
the coherent X-ray generation to the keV and tens of keV spectral regions. The
implemented X-ray source is remarkably easily accessible: the requirements for
the laser can be met in a university-scale laboratory, the gas jet is a
replenishable debris-free target, and the harmonics emanate directly from the
gas jet without additional devices. Our results open the way to a compact
coherent ultrashort brilliant X-ray source with single shot and high-repetition
rate capabilities, suitable for numerous applications and diagnostics in many
research fields
Measurement of the Atmospheric Muon Charge Ratio at TeV Energies with MINOS
The 5.4 kton MINOS far detector has been taking charge-separated cosmic ray
muon data since the beginning of August, 2003 at a depth of 2070
meters-water-equivalent in the Soudan Underground Laboratory, Minnesota, USA.
The data with both forward and reversed magnetic field running configurations
were combined to minimize systematic errors in the determination of the
underground muon charge ratio. When averaged, two independent analyses find the
charge ratio underground to be 1.374 +/- 0.004 (stat.) +0.012 -0.010(sys.).
Using the map of the Soudan rock overburden, the muon momenta as measured
underground were projected to the corresponding values at the surface in the
energy range 1-7 TeV. Within this range of energies at the surface, the MINOS
data are consistent with the charge ratio being energy independent at the two
standard deviation level. When the MINOS results are compared with measurements
at lower energies, a clear rise in the charge ratio in the energy range 0.3 --
1.0 TeV is apparent. A qualitative model shows that the rise is consistent with
an increasing contribution of kaon decays to the muon charge ratio.Comment: 16 pages, 17 figure
Measurement of neutrino velocity with the MINOS detectors and NuMI neutrino beam
The velocity of a ~3 GeV neutrino beam is measured by comparing detection times at the near and far detectors of the MINOS experiment, separated by 734 km. A total of 473 far detector neutrino events was used to measure (v-c)/c=5.12.910-5 (at 68% C.L.). By correlating the measured energies of 258 charged-current neutrino events to their arrival times at the far detector, a limit is imposed on the neutrino mass of mnu<50 MeV/c2 (99% C.L.)
A Study of Muon Neutrino Disappearance Using the Fermilab Main Injector Neutrino Beam
We report the results of a search for muon-neutrino disappearance by the Main
Injector Neutrino Oscillation Search. The experiment uses two detectors
separated by 734 km to observe a beam of neutrinos created by the Neutrinos at
the Main Injector facility at Fermi National Accelerator Laboratory. The data
were collected in the first 282 days of beam operations and correspond to an
exposure of 1.27e20 protons on target. Based on measurements in the Near
Detector, in the absence of neutrino oscillations we expected 336 +/- 14
muon-neutrino charged-current interactions at the Far Detector but observed
215. This deficit of events corresponds to a significance of 5.2 standard
deviations. The deficit is energy dependent and is consistent with two-flavor
neutrino oscillations according to delta m-squared = 2.74e-3 +0.44/-0.26e-3
eV^2 and sin^2(2 theta) > 0.87 at 68% confidence level.Comment: In submission to Phys. Rev.
First observations of separated atmospheric nu_mu and bar{nu-mu} events in the MINOS detector
The complete 5.4 kton MINOS far detector has been taking data since the beginning of August 2003 at a depth of 2070 meters water-equivalent in the Soudan mine, Minnesota. This paper presents the first MINOS observations of nuµ and [overline nu ]µ charged-current atmospheric neutrino interactions based on an exposure of 418 days. The ratio of upward- to downward-going events in the data is compared to the Monte Carlo expectation in the absence of neutrino oscillations, giving Rup/downdata/Rup/downMC=0.62-0.14+0.19(stat.)±0.02(sys.). An extended maximum likelihood analysis of the observed L/E distributions excludes the null hypothesis of no neutrino oscillations at the 98% confidence level. Using the curvature of the observed muons in the 1.3 T MINOS magnetic field nuµ and [overline nu ]µ interactions are separated. The ratio of [overline nu ]µ to nuµ events in the data is compared to the Monte Carlo expectation assuming neutrinos and antineutrinos oscillate in the same manner, giving R[overline nu ][sub mu]/nu[sub mu]data/R[overline nu ][sub mu]/nu[sub mu]MC=0.96-0.27+0.38(stat.)±0.15(sys.), where the errors are the statistical and systematic uncertainties. Although the statistics are limited, this is the first direct observation of atmospheric neutrino interactions separately for nuµ and [overline nu ]µ
Measurement of Neutrino Oscillations with the MINOS Detectors in the NuMI Beam
This letter reports new results from the MINOS experiment based on a two-year
exposure to muon neutrinos from the Fermilab NuMI beam. Our data are consistent
with quantum mechanical oscillations of neutrino flavor with mass splitting
eV (68% confidence level) and
mixing angle (90% confidence level). Our data disfavor
two alternative explanations for the disappearance of neutrinos in flight,
namely neutrino decays into lighter particles and quantum decoherence of
neutrinos, at the 3.7 and 5.7 standard deviation levels, respectively.Comment: 5 pages, 4 figures, submitted to Phys. Rev. Let
Sudden stratospheric warmings seen in MINOS deep underground muon data
The rate of high energy cosmic ray muons as measured underground is shown to be strongly correlated with upper-air temperatures during short-term atmospheric (10-day) events. The effects are seen by correlating data from the MINOS underground detector and temperatures from the European Centre for Medium Range Weather Forecasts during the winter periods from 2003–2007. This effect provides an independent technique for the measurement of meteorological conditions and presents a unique opportunity to measure both short and long-term changes in this important part of the atmosphere
Observation of Muon Neutrino Disappearance with the MINOS Detectors in the NuMI Neutrino Beam
This Letter reports results from the MINOS experiment based on its initial exposure to neutrinos from the Fermilab NuMI beam. The rates and energy spectra of charged current νμ interactions are compared in two detectors located along the beam axis at distances of 1 and 735 km. With 1.27×1020 120 GeV protons incident on the NuMI target, 215 events with energies below 30 GeV are observed at the Far Detector, compared to an expectation of 336±14 events. The data are consistent with νμ disappearance via oscillations with |Δm322|=2.74-0.26+0.44×10-3 eV2 and sin2(2θ23)>0.87 (68% C.L.)
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