Large‐acceptance diamond planar refractive lenses manufactured by laser cutting

For the first time, single‐crystal diamond planar refractive lenses have been fabricated by laser micromachining in 300 µm‐thick diamond plates which were grown by chemical vapour deposition. Linear lenses with apertures up to 1 mm and parabola apex radii up to 500 µm were manufactured and tested at the ESRF ID06 beamline. The large acceptance of these lenses allows them to be used as beam‐conditioning elements. Owing to the unsurpassed thermal properties of single‐crystal diamond, these lenses should be suitable to withstand the extreme flux densities expected at the planned fourth‐generation X‐ray sources.     

Jet activity versus alignment

The hypothesis of the relation between the observed alignment of spots in x-ray films in cosmic ray emulsion experiments and the features of events in which jets prevail at super-high energies is tested. Due to the strong dynamical correlation between jet axis directions and that between the momenta of jet particles (almost collinearity), the evaluated degree of alignment is considerably larger than that for randomly selected chaotically located spots in the x-ray film. It appears to be comparable with the experimental data provided that the height of the primary interaction, the collision energy and the total energy of the selected clusters meet certain conditions. The Monte Carlo generator PYTHIA, which basically well describes jet events in hadron-hadron interactions, was used for the analysis.Received: 25 February 2005, Revised: 18 April 2005, Published online: 2 August 2005     

Medium-modified fragmentation of <Emphasis Type="Italic">b</Emphasis>-jets tagged by a leading muon in ultrarelativistic heavy ion collisions

The possibility to observe the medium-modified fragmentation of hard b quarks tagged by a leading muon in ultrarelativistic heavy ion collisions is analyzed. We have found that reasonable statistics, events per 1 month of LHC run with lead beams, can be expected for the realistic geometrical acceptance and kinematic cuts. The numerical estimates on the effect of the medium-induced softening b-jet fragmentation function are given.Received: 9 July 2004, Published online: 1 October 2004     

A new possible mechanism of lepton-pair radiation from quark-gluon plasmas

The lepton-pair production mechanism resulting from escaping quarks interacting with a collective confining colour field is discussed. The pair production rate is estimated and the spectrum of pair invariant mass is calculated. It is suggested that measuring the angle asymmetry of radiated lepton-pairs could indicate quark-gluon plasma formation.     

The phenomenon of alignment in cosmic rays and analyzing azimuthal anisotropy on the large hadron collider

The phenomenon of alignment discovered in experiments with emulsion chambers is a consequence of the coplanar scatter of secondary particles in nuclear interaction at very high energies (>10¹⁶ eV). The possibility of a correlation between the alignment effect and the generation of QCD jets is considered. Criteria and methods for analyzing the correlation between the alignment phenomenon and events with unusual topology on the LHC are proposed     

Elliptic flow studies using the CMS detector

The azimuthal anisotropy of charged particles in heavy ion collisions is an important probe of quark-gluon plasma evolution at early stages. The nuclear reaction plane can be determined independently by different detector subsystems and using different analysis methods. This paper reports the capability of the CMS detector at the LHC to reconstruct the reaction plane of the collision and to me asure elliptic flow with calorimetry and a tracking system. The analysis is based on a full CMS detector simulation of Pb + Pb events with the HYDJET event generator.     

Jet quenching pattern at LHC in PYQUEN model

The first LHC data on high transverse momentum hadron and dijet spectra in PbPb collisions at center-of-mass energy 2.76 TeV per nucleon pair are analyzed in the frameworks of PYQUEN jet quenching model. The presented studies for the nuclear modification factor of high-p _T hadrons and the imbalance in dijet transverse energy support the supposition that the intensive wide-angular (“out-of-cone”) medium-induced partonic energy loss is seen in central PbPb collisions at the LHC.