Particle identification

The identity of a particle is fixed by its mass, lifetime and quantum numbers such as charge, spin, parity and flavour. A particle’s identity can be inferred by observing its interactions in matter, as for example the shower development of an electron or a photon, the specific energy loss of charged particles, the emission of radiation by a particle or the penetration capability of a muon. The mass of a particle can be determined by measurements of specific energy loss, time-of-flight or Cherenkov radiation when combined with a momentum measurement. High energy electrons can be separated from heavier particles through transition radiation. For particles which decay in the detector the mass can often be kinematically reconstructed from the decay products and the lifetime can be determined by the reconstruction of secondary vertices.

SECONDARY ELECTRON EMISSION INDUCED BY α-PARTICLES FROM Mg-MgO LAYERS

The paper presents the results of experimental study of forward and backward electron emission induced by α-particles from the deposited film of magnesium. It was shown that during the deposition of magnesium in residual gas atmosphere the deposited film contained a large amount of MgO component, which makes it possible to consider the resulting structure as Mg-MgO. The presence of magnesium oxide on the surface of the target and the collector leads to the fact that the previously obtained dependence of the ratio of forward and backward electron yields on specific energy loss of the ion for various metals is not applicable in the case of deposited magnesium. The differences are explained by the specificity of the emission from magnesium in the presence of a significant amount of MgO. The results obtained can be used to detect MgO on the surface of a magnesium substrate. It was shown the differences in the experimental data for the bulk magnesium collector and the collector with deposited magnesium layer

Study of the dE/dx resolution of a GEM Readout Chamber prototype for the upgrade of the ALICE TPC

The ALICE Collaboration is planning a major upgrade of its central barrel detectors to be able to cope with the increased LHC luminosity beyond 2020. For the TPC, this implies a replacement of the currently used gated MWPCs (Multi-Wire Proportional Chamber) by GEM (Gas Electron Multiplier) based readout chambers. In order to prove, that the present particle identification capabilities via measurement of the specific energy loss are retained after the upgrade, a prototype of the ALICE IROC (Inner Readout Chamber) has been evaluated in a test beam campaign at the CERN PS. The dE/dx resolution of the prototype has been proven to be fully compatible with the current MWPCs.

PARTICLE IDENTIFICATION BY IONIZATION ENERGY LOSS IN THE CMS SILICON STRIP TRACKER

The large sensitive volume of the Silicon Strip Tracker of CMS detector allows, for a typical track, up to 20 samplings of the specific energy loss by ionization, providing a powerful tool for particle identification at low βγ values. We report on the application to hadron identification in the first pp collisions recorded by the CMS detector at [Formula: see text] and 7 TeV and on applications to other CMS analyses, including the search for highly-ionizing exotic particles.

Magneto-viscoelastic plane waves in rotating media in the generalized thermoelasticity II

A study is made of the propagation of time-harmonic magneto-thermoviscoelastic plane waves in a homogeneous electrically conducting viscoelastic medium of Kelvin-Voigt type permeated by a primary uniform external magnetic field when the entire medium rotates with a uniform angular velocity. The generalized thermoelasticity theory of type II (Green and Naghdi model) is used to study the propagation of waves. A more general dispersion equation for coupled waves is derived to ascertain the effects of rotation, finite thermal wave speed of GN theory, viscoelastic parameters and the external magnetic field on the phase velocity, the attenuation coefficient, and the specific energy loss of the waves. Limiting cases for low and high frequencies are also studied. In absence of rotation, external magnetic field, and viscoelasticity, the general dispersion equation reduces to the dispersion equation for coupled thermal dilatational waves in generalized thermoelasticity II (GN model), not considered before. It reveals that the coupled thermal dilatational waves in generalized thermoelasticity II are unattenuated and nondispersive in contrast to the thermoelastic waves in classical coupled thermoelasticity (Chadwick (1960)) which suffer both attenuation and dispersion.

Magnetoelastic plane waves in rotating media in thermoelasticity of type II (G-N model)

A study is made of the propagation of time-harmonic plane waves in an infinite, conducting, thermoelastic solid permeated by a uniform primary external magnetic field when the entire medium is rotating with a uniform angular velocity. The thermoelasticity theory of type II (G-N model) (1993) is used to study the propagation of waves. A more general dispersion equation is derived to determine the effects of rotation, thermal parameters, characteristic of the medium, and the external magnetic field. If the primary magnetic field has a transverse component, it is observed that the longitudinal and transverse motions are linked together. For low frequency (χ≪1,χbeing the ratio of the wave frequency to some standard frequencyω∗), the rotation and the thermal field have no effect on the phase velocity to the first order ofχand then this corresponds to only one slow wave influenced by the electromagnetic field only. But to the second order ofχ, the phase velocity, attenuation coefficient, and the specific energy loss are affected by rotation and depend on the thermal parameterscT,cTbeing the nondimensional thermal wave speed of G-N theory, and the thermoelastic couplingεT, the electromagnetic parametersεH, and the transverse magnetic fieldRH. Also for large frequency, rotation and thermal field have no effect on the phase velocity, which is independent of primary magnetic field to the first order of (1/χ) (χ≫1), and the specific energy loss is a constant, independent of any field parameter. However, to the second order of (1/χ), rotation does exert influence on both the phase velocity and the attenuation factor, and the specific energy loss is affected by rotation and depends on the thermal parameterscTandεT, electromagnetic parameterεH, and the transverse magnetic fieldRH, whereas the specific energy loss is independent of any field parameters to the first order of (1/χ).

SCFV-6HIS Bioengineered for High Fidelity Labeling.

In life sciences, the essential part of the functional molecular analysis is the unambiguous identification of biochemical composition of the observed structures. This analysis is expected to create a bridge between functional data pouring from biochemistry and molecular biology laboratories with the molecular architecture data available from ultrastructural images. This goal can be attained by application of various ultrastructural tags (See: Albrecht et al. 1992).A new promising approach for high fidelity labeling is offered by molecular cloning and expression of molecules containing metal binding sites making them suitable for electron spectroscopic imaging (ESI) (Malecki 1995). A truly enormous potential of ESI relies in its ability for mapping of various elements within the same sample. Interactions of electrons with an atom result in the electrons specific energy loss. Based upon these energy losses distribution of the elements within the sample can be mapped.