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 5d2^{2}~3^{3}F2_{2} 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 $\rm{5d^{2}~^{3}F_{2}}$ 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 $30\,\%$ of the trapped atoms to this state. The radiative decay of the $\rm{5d^{2}~^{3}F_{2}}$ state cascades to the cooling cycle of the MOT with a probability of $96.0(7)\,\%$ corresponding to a trap loss of $4.0(7)\,\%$ and its lifetime is determined to $\rm{160(10)~\mu s}$. This is in good agreement with the theoretically calculated lifetime of $\rm{190~\mu s}$ [J. Phys. B, {\bf 40}, 227 (2007)]. The determined loss of $4.0(7)\,\%$ 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 $\alpha$, timescale $\tau$ of star formation, gas component $\sigma_{g}$ of surface mass density and a real exponent $n$. A given exponent $n$ determines $\tau$ which however yields the corresponding star formation rate. Current nominal Schmidt exponent $n_{s}$ for our model is $2<n_{s}<3$. Based on a gravitational instability parameter $Q_{A}$ and another dimensionless parameter $f_{P}\equiv (P/G\sigma_{c}^{2})^{1/2}$, where $P$ = pressure, $\sigma_{c}$ = 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 $Q_{A}$ 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

Isotope shifts of 6s5d 3^3D-states in neutral Barium

Laser spectroscopy of the low lying $^1$P and $^3$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 $^3$D$_{1,2}$-$^1$P$_1$ transitions. A deviation of the King plot from its expected behavior has been observed. Further we have optically resolved the hyperfine structure of the $^3$D$_{1,2}$ states.Comment: 7 pages, 7 figure