Higgs and SUSY searches at LHC

I start with a brief introduction to Higgs mechanism and supersymmetry. Then I discuss the theoretical expectations, current limits and search strategies for Higgs boson(s) at LHC — first in the SM and then in the MSSM. Finally I discuss the signatures and search strategies for the superparticles.     

Effect of preparation method on the properties of deposited copper-palladium deep-oxidation catalysts

Activity of alumocopper-palladium catalysts (0.5 at.% Pd, 0.1–3.0 at.% Cu) which differ in preparation method in CO, C₂H₄ and CH₄ oxidation is studied. It is shown that preliminary modification of a carrier by copper leads to an enhancement of catalyst activity as compared with an alumopalladium one. With the methods of EDRS, TPR-TRS, and TPR of adsorbed CO and O₂, the Pd/Cu/Al₂O₃, Cu/Pd/Al₂O₃ and (Pd−Cu)/Al₂O₃, systems are studied. It is established that premodification of the carrier leads to a weakening of its interaction with the second metal while the combined deposition from one impregnating solution in subsequent thermal treatment is accompanied by a strong metal aggregation. Institute of Physicoorganic Chemistry, National Academy of Sciences of Belarus, 13, Surganov St., Minsk, 220072. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 114–120, January–February, 1998.     

Temporal coherent control induced by wave packet interferences in one and two photon atomic transitions

The interaction of a sequence of two identical ultrashort laser pulses with an atomic system results in quantum interferences as in Ramsey fringes experiments. These interferences allow achievement of temporal coherent control of the excitation probability. We present the results of a temporal coherent control experiment on two different atomic systems: one-photon absorption in K (4s-4p) and two-photon absorption in Cs (6s-7d). In K, the quantum interferences between the two excitation paths associated with the laser pulses are revealed through rapid oscillations of the excitation probability as a function of the time delay between the two pulses. These oscillations take place at the transition frequency (period T = 2.56 fs). The interferences are modulated by beats (at about 580 fs) resulting from the doublet structure of the excited state (4p (² P _1/2 , ² P _3/2 )). Three complementary interpretations of this experiment are presented: in terms of beats of quantum interferences, of variation in the spectrum intensity, and of wave packet interferences. Whenever the two laser pulses are temporally overlapped, optical interferences are superimposed on to the quantum interferences. The distinction between these two types of interference is clearly revealed in the two-photon excitation scheme performed on Cs (6s-7d (² D _3/2 , ² D _5/2 )) because quantum interferences occur at twice the frequency of the optical interferences. Received: 30 December 1997 / Revised: 28 February 1998 / Accepted: 4 March 1998     

Effect of the initial phase of the field in ionization by ultrashort laser pulses

We report on observable new features related to ionization of atoms by laser pulses of only few cycles and some intensity. We show that for particular photo-electron energies, the angular distribution becomes asymmetric and that this asymmetry is related to the initial phase of the field. Received: 4 November 1997/Revised: 21 January 1998/Accepted: 23 February 1998     

Maximum spin aligned states in 98 47Ag51

New excited states have been observed in the neutron deficient isotope ⁹⁸Ag following the ⁵⁸Ni+⁵⁰Cr →¹⁰⁸Te^* heavy–ion reaction. One of these states may be interpreted as a maximum spin aligned state of the πg_9/2 ⁻³νg_7/2 configuration. Other possible interpretations within the nuclear shell model are discussed as well. Received: 24 October 1997     

Anharmonic dynamical behaviour in bcc zirconium

We present inelastic neutron scattering measurements of the low energy and strongly damped phonons in the high temperature bcc phase of zirconium. These phonons were investigated at different scattering vectors but equivalent phonon wave vectors in different Brillouin zones or along different but equivalent paths in the same Brillouin zone. Neither the observed differences in intensity nor in line shapes can be explained by the coherent one-phonon scattering law . This leads to an apparent violation of the fundamental symmetry of lattice dynamics. Taking into account the strong anharmonicity of these phonons, interferences between one- and multi-phonon scattering are held responsible for these effects. Measurements in different scattering planes reveal that due to the symmetry of the bcc lattice, these effects can only be observed in certain directions. Received: 24 December 1997 / Received in final form: 9 March 1998 / Accepted: 19 March 1998     

Two-dimensional polymer networks at a mixed boundary: Surface and wedge exponents

We provide general formulae for the configurational exponents of an arbitrary polymer network connected to the surface of an arbitrary wedge of the two-dimensional plane, where the surface is allowed to assume a general mixture of boundary conditions on either side of the wedge. We report on a comprehensive study of a linear chain by exact enumeration, with various attachments of the walk's ends to the surface, in wedges of angles and , with general mixed boundary conditions. Received: 20 October 1997 / Accepted: 13 May 1998     

Charge density wave transport in submicron antidot arrays in NbSe3

We demonstrate for the first time that a periodic array of submicrometer holes (antidots) can be patterned into thin single NbSe₃ crystals. We report on the study of Charge Density Wave (CDW) transport of the network of mesoscopic units between antidots. Size of the elementary unit can be as small as 0.5 μm along the chain axis and in cross-section. We observe size effects for Ohmic residual resistance and in CDW transport current-voltage characteristics in submicronic networks. Received: 25 November 1997 / Received in final form: 30 March 1998 / Accepted: 6 April 1998     

Cavitation in superfluid helium-4 at low temperature

We have studied the nucleation of bubbles in pure superfluid helium-4 at temperatures down to 65 mK. We have found that the nucleation is a stochastic process, and that at temperatures below 600 mK the nucleation rate is independent of temperature. These results are consistent with the assumption that the nucleation takes place via quantum tunneling. Received: 15 November 1997 / Received in final form: 19 December 1997 / Accepted: 22 January 1998     

Novel massive ground states of spin chains in a magnetic field

Novel massive quantum states appearing in spin chains under a strong magnetic field are discussed. These states lead to plateaus in magnetization curves. When the systems are axially symmetric and the field is applied parallel to the symmetry-axis, the phenomena are analogous to metal-insulator transitions. Striking features of the plateau phenomena - exactness and rationality - are explained as consequences the commensurability condition to the underlying lattice. The effects of the planar anisotropy are also discussed in detail. Received: 16 February 1998 / Revised: 20 April 1998 / Accepted: 30 April 1998