164,857 research outputs found
Top quark charge asymmetry measurements with ATLAS detector
The top quark charge asymmetry measurements performed with ATLAS detector at
a centre-of-mass energy of 7 TeV are presented.Comment: 5 pages text + 1 title page , 4 figures Proceedings of the 8th
International Workshop on the CKM Unitarity Triangle (CKM 2014), Vienna,
Austria, September 8-12, 201
Intercropping cereals and grain legumes: a farmer’s perspective
Intercropping cereals and grain legumes show potential for organic agriculture in many ways. However, the use of land equivalent ratio (LER) as a measure for calculating the cropping advantage of intercrops over sole crops is too simple: neglecting weed suppression, yield reliability, grain quality, and minimum profitable yield, which are all relevant fac-tors from a farmer’s perspective. Only when the crop selection for the mixtures is carefully done, and crops are grown on the right soil in the right rotation, can intercropping be made to profit
Lifetime determination of the 5d~F state in barium using trapped atoms
Magneto-optically trapped atoms enable the determination of lifetimes of
metastable states and higher lying excited states like the
state in barium. The state is efficiently populated by
driving strong transitions from metastable states within the cooling cycle of
the barium MOT. The lifetime is inferred from the increase of MOT fluorescence
after the transfer of up to of the trapped atoms to this state. The
radiative decay of the state cascades to the cooling
cycle of the MOT with a probability of corresponding to a trap
loss of and its lifetime is determined to .
This is in good agreement with the theoretically calculated lifetime of
[J. Phys. B, {\bf 40}, 227 (2007)]. The determined loss of
from the cooling cycle is compared with the theoretically
calculated branching ratios. This measurement extends the efficacy of trapped
atoms to measure lifetimes of higher, long-lived states and validate the atomic
structure calculations of heavy multi-electron systems.Comment: 5 pages, accepted for publication in Physical Review
Interacting Tachyon: generic cosmological evolution for a tachyon and a scalar field
We study the cosmological evolution of a tachyon scalar field T with a
Dirac-Born-Infeld type lagrangian and potential V(T) coupled to a canonically
normalized scalar field \phi with an arbitrary interaction term B(T,\phi) in
the presence of a barotropic fluid \rb, which can be matter or radiation. The
force between the barotropic fluid and the scalar fields is only gravitational.
We show that the dynamics is completely determine by only three parameters L1 =
- V_T/ V^{3/2}, L2= - B_T /B^{3/2} and L3 =-B_{\phi}/B. We determine
analytically theconditions for \lm_i under which the energy density of T,
\phi and \rb have the same redshift. We study the behavior of T and \phi in
the asymptotic limits for L_i and we show the numerical solution for different
interesting cases.
The effective equation of state for the tachyon field changes due to the
interaction with the scalar field and we show that it is possible for a tachyon
field to redshift as matter in the absence of an interaction term B and as
radiation when B is turned on. This result solves then the tachyonic matter
problem.Comment: 13 pages, 5 figure
Gravitational instability and star formation in disk galaxies
We present a general star formation law where star formation rate depends
upon efficiency , timescale of star formation, gas component
of surface mass density and a real exponent . A given exponent
determines which however yields the corresponding star formation
rate. Current nominal Schmidt exponent for our model is .
Based on a gravitational instability parameter and another
dimensionless parameter , where =
pressure, = column density of molecular clouds, we suggest a
general equation for star formation rate which depends upon relative competence
of the two parameters for various physical circumstances. We find that
emerges to be a better parameter for star formation scenario than Toomre
Q-parameter. Star formation rate in the solar neighbourhood is found to be in
good agreement with values inferred from previous studies. Under closed box
approximation model, we obtain a relation between metallicity of gas and the
efficiency of star formation. Our model calculations of metallicity in the
solar neighbourhood agree with earlier estimates. We conclude that metallicity
dispersion for stars of same age may result due to a change in efficiency
through which different sample stars were processed. For no significant change
of metallicity with age, we suggest that all sample stars were born with almost
similar efficiency.Comment: 10 pages, 3 figures, submitted to MNRA
Telling the spin of the "Higgs boson" at the LHC
We assume that the Higgs boson or a possible resonance---playing its role in
strongly interacting models of electroweak symmetry breaking---has been
discovered at the LHC and propose a search strategy to determine its spin based
on two simple asymmetries in the ZZ, W+W- and t t-bar decays channels. We
consider some benchmark values for its mass (in the interval from 182 GeV/c^2
to 1 TeV/c^2) and discuss the relative advantages of the different decay
processes. A full analysis, including the background, is given. For a
center-of-mass energy of 14 TeV, we find that the lowest integrated luminosity
required to discriminate between the different spins is, depending on the
process and the resonance mass, between 40 fb^{-1} and 250 fb^{-1}.Comment: 17 pages, 3 figure
Isotope shifts of 6s5d D-states in neutral Barium
Laser spectroscopy of the low lying P and D states in atomic barium
has been performed. This work contributes substantially to the development of
an effective laser cooling and trapping for heavy alkaline earth elements and
aims in particular for a better understanding of the atomic wave function of
these systems. Isotope shifts and hyperfine structures are ideal probes for the
wave functions at the position of the nucleus. This is essential input for a
theoretical evaluation of the sensitivity to fundamental symmetry breaking
properties like permanent electric dipole moments. We report the first isotope
shift measurements of the D-P transitions. A deviation of
the King plot from its expected behavior has been observed. Further we have
optically resolved the hyperfine structure of the D states.Comment: 7 pages, 7 figure
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