706 research outputs found
Thin-Film Metamaterials called Sculptured Thin Films
Morphology and performance are conjointed attributes of metamaterials, of
which sculptured thin films (STFs) are examples. STFs are assemblies of
nanowires that can be fabricated from many different materials, typically via
physical vapor deposition onto rotating substrates. The curvilinear--nanowire
morphology of STFs is determined by the substrate motions during fabrication.
The optical properties, especially, can be tailored by varying the morphology
of STFs. In many cases prototype devices have been fabricated for various
optical, thermal, chemical, and biological applications.Comment: to be published in Proc. ICTP School on Metamaterials (Augsut 2009,
Sibiu, Romania
The Target Silicon Detector for the FOCUS Spectrometer
We describe a silicon microstrip detector interleaved with segments of a
beryllium oxide target which was used in the FOCUS photoproduction experiment
at Fermilab. The detector was designed to improve the vertex resolution and to
enhance the reconstruction efficiency of short-lived charm particles.Comment: 18 pages, 14 figure
Measurement of the relative branching ratio BR(\Xi_c^+ \to p^+ K^-\pi^+)\BR(\Xi_c^+ \to \Xi^- \pi^+ \pi^+)
We report the observation of the Cabibbo suppressed decay \Xi_c^+ \to p
K^-\pi^+ using data collected with the FOCUS spectrometer during the 1996--97
Fermilab fixed target run. We find a \Xi_c^+ signal peak of 202\pm35 events. We
have measured the relative branching ratios BR(\Xi^+_c\to p
K^-\pi^+)/BR(\Xi^+_c\to\Xi^-\pi^+\pi^+)= 0.234 \pm 0.047 \pm 0.022 and
BR(\Xi^+_c\to p \bar{K}^*(892)^0)/BR(\Xi^+_c\to p K^-\pi^+)= 0.54 \pm 0.09 \pm
0.05 .Comment: 9 pages, 4 figure
Autoluminescent Plants
Prospects of obtaining plants glowing in the dark have captivated the imagination of scientists and layman alike. While light emission has been developed into a useful marker of gene expression, bioluminescence in plants remained dependent on externally supplied substrate. Evolutionary conservation of the prokaryotic gene expression machinery enabled expression of the six genes of the lux operon in chloroplasts yielding plants that are capable of autonomous light emission. This work demonstrates that complex metabolic pathways of prokaryotes can be reconstructed and function in plant chloroplasts and that transplastomic plants can emit light that is visible by naked eye
Discovery of a Be/X-ray pulsar binary and associated supernova remnant in the Wing of the SMC
We report on a new Be/X-ray pulsar binary located in the Wing of the Small
Magellanic Cloud (SMC). The strong pulsed X-ray source was discovered with the
Chandra and XMM-Newton X-ray observatories. The X-ray pulse period of 1062 s is
consistently determined from both Chandra and XMM-Newton observations,
revealing one of the slowest rotating X-ray pulsars known in the SMC. The
optical counterpart of the X-ray source is the emission-line star 2dFS 3831.
Its B0-0.5(III)e+ spectral type is determined from VLT-FLAMES and 2dF optical
spectroscopy, establishing the system as a Be/X-ray binary (Be-XRB). The hard
X-ray spectrum is well fitted by a power-law with additional thermal and
blackbody components, the latter reminiscent of persistent Be-XRBs. This system
is the first evidence of a recent supernova in the low density surroundings of
NGC 602. We detect a shell nebula around 2dFS 3831 in H-alpha and [O III]
images and conclude that it is most likely a supernova remnant. If it is linked
to the supernova explosion that created this new X-ray pulsar, its kinematic
age of (2-4)x10^4 yr provides a constraint on the age of the pulsar.Comment: 5 pages, 5 figures, accepted for publication in MNRAS Letter
Search for CP violation in D0 and D+ decays
A high statistics sample of photoproduced charm particles from the FOCUS
(E831) experiment at Fermilab has been used to search for CP violation in the
Cabibbo suppressed decay modes D+ to K-K+pi+, D0 to K-K+ and D0 to pi-pi+. We
have measured the following CP asymmetry parameters: A_CP(K-K+pi+) = +0.006 +/-
0.011 +/- 0.005, A_CP(K-K+) = -0.001 +/- 0.022 +/- 0.015 and A_CP(pi-pi+) =
+0.048 +/- 0.039 +/- 0.025 where the first error is statistical and the second
error is systematic. These asymmetries are consistent with zero with smaller
errors than previous measurements.Comment: 12 pages, 4 figure
A measurement of lifetime differences in the neutral D-meson system
Using a high statistics sample of photoproduced charm particles from the
FOCUS experiment at Fermilab, we compare the lifetimes of neutral D mesons
decaying via D0 to K- pi+ and K- K+ to measure the lifetime differences between
CP even and CP odd final states. These measurements bear on the phenomenology
of D0 - D0bar mixing. If the D0 to K-pi+ is an equal mixture of CP even and CP
odd eigenstates, we measure yCP = 0.0342 \pm 0.0139 \pm 0.0074.Comment: 15 pages, 5 figure
Measurements of the Sigma_c^0 and Sigma_c^{++} Mass Splittings
Using a high statistics sample of photoproduced charmed particles from the
FOCUS experiment at Fermilab (FNAL-E831), we measure the mass splittings of the
charmed baryons Sigma_c^0 and Sigma_c^{++}. We find M(Sigma_c^0 - Lambda_c^+) =
167.38 +/- 0.21 +/- 0.13 MeV/c^2 and M(Sigma_c^++ - Lambda_c^+) = 167.35 +/-
0.19 +/- 0.12 MeV/c^2 with samples of 362 +/- 36 and 461 +/- 39 events,
respectively. We measure the isospin mass splitting M(Sigma_c^++ - Sigma_c^0)
to be -0.03 +/- 0.28 +/- 0.11 Mev/c^2. The first errors are statistical and the
second are systematic.Comment: 10 pages, 2 figure
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
- âŚ