New data obtained by experiment ATLAS enabled detailed investigation of properties of new particle discovered in last year. Studies of the spin and parity quantum numbers of the Higgs boson are presented, based on proton–proton collision data collected by the ATLAS experiment at the LHC. The Standard Model spin–parity JP = 0+ hypothesis is compared with alternative hypotheses using the Higgs boson decays H→γγ, H→ZZ*→4ℓ (image 1) and H→WW*→ℓνℓν, as well as the combination of these channels.
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Significant results of scientific activity in year 2013
The miniaturization and integration of frequency-agile microwave circuits — relevant to electronically tunable filters, antennas, resonators and phase shifters — with microelectronics offers tantalizing device possibilities, yet requires thin films whose dielectric constant at gigahertz frequencies can be tuned by applying a quasi-static electric field. Appropriate systems such as BaxSr1−xTiO3 have a paraelectric–ferroelectric transition just below ambient temperature, providing high tunability.
Nanocomposites of polymers with carbon nanotubes CNTs are of intense research interest for their unique electrical and mechanical properties. Well electrically conducting CNT, thanks to its specific shape, enables to process composites with extremely low percolation threshold. Our colleagues in UK succeeded to prepare well dispersed composites of PET polymer with CNTs, which have been in Institute of Physics for the first time characterized by broadband conductivity and dielectric spectroscopy.
Spin glass theory is extensively complicated, thus the full mean-field solution of spin glass models with a continuous order-parameter function is not directly available and approximate schemes must be used to assess its properties. The main goal is to find such solutions that wouldn't show non-physical behavior eg. negative enthropy for absolute zero. We introduced evolution operator applicable to the whole range of temperatures while simultaneously suppressing non-physical behavior even in the lowest evolution order.
Possibility of the existence of magnetic ordering in carbon nanotubes (CNTs) was theoretically predicted, but so far nobody has been able to experimentally confirm the existence of localized magnetic moment in carbon. The main obstacle is a presence of residual (magnetic) metal catalyst nanoparticles in CNTs from the production process. Group from Institute of Physics in collaboration with J. Heyrovsky Institute tested several methods for CNTs purification.
We prepared a novel type of hybrid nanocomposite by mixing maghemite nanoparticles and a chiral liquid crystalline compound. The hybrid system exhibits ferroelectric as well superparamagnetic properties. The impact of nanoparticles and the effect of an applied magnetic field on the ferroelectric liquid crystalline properties were established. The ferroelectric properties are conserved up to a concentration of 5.6% of maghemite.
František Slanina from the Institute of Physics has lead long-time research activities in applying physical methods to economy or social processes resulting in an invitation from Oxford University Press. The monography is a course in methods and models rooted in physics and used in modelling economic and social phenomena. It covers the discipline of econophysics, which creates an interface between physics and economics. Besides the main theme, it touches on the theory of complex networks and simulations of social phenomena in general. Prof.
Supersurface electron scattering, i.e., electron energy losses and associated deflections in vacuum above the surface of a medium, is shown to contribute significantly to electron spectra. We have obtained experimental verification (in absolute units) of theoretical predictions that the angular distribution of the supersurface backscattering probability exhibits strong oscillations which are anticorrelated with the generalized Ramsauer-Townsend minima in the backscattering probability.
Friction between two objects can be understood by the making, stretching, and breaking of thousands of atomic-scale asperities. We achieved to measure the friction forces with atomic resolution using atomic force microscope. Our measurements showed that the friction is dependent on the relative orientation of the atomic structure of surfaces in the contact. The performed calculations provided a deeper understanding of the origin of the directional dependence of the friction as a result of different excitation of vibrational modes at the surface.
The structural and magnetic properties of two mixed-valence cobaltites with a formal population of 0.30 Co4+ ions per f.u., (Pr1−yYy)0.7Ca0.3CoO3 (y=0 and 0.15), have been studied down to very low temperatures by means of high-resolution neutron diffraction, SQUID magnetometry and heat-capacity measurements. Combining this complex experimental research with calculations from the first priciples we determined character of spin states in cobalt ions.
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