Optimal Jet Finder

We describe a FORTRAN 77 implementation of the optimal jet definition for identification of jets in hadronic final states of particle collisions. We discuss details of the implementation, explain interface subroutines and provide a usage example. The source code is available from http://www.inr.ac.ru/~ftkachov/projects/jets/.

Program summary

Title of program: Optimal Jet Finder (OJF_014)Catalogue identifier: ADSBProgram Summary URL:http://cpc.cs.qub.ac.uk/summaries/ADSBProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandComputer: Any computer with the FORTRAN 77 compilerTested with: g77/Linux on Intel, Alpha and Sparc; Sun f77/Solaris (thwgs.cern.ch); xlf/AIX (rsplus.cern.ch); MS Fortran PowerStation 4.0/Win98Programming language used: FORTRAN 77Memory required: ∼1 MB (or more, depending on the settings)Number of bytes in distributed program, including examples and test data: 251 463Distribution format: tar gzip fileKeywords: Hadronic jets, jet finding algorithmsNature of physical problem: Analysis of hadronic final states in high energy particle collision experiments often involves identification of hadronic jets. A large number of hadrons detected in the calorimeter is reduced to a few jets by means of a jet finding algorithm. The jets are used in further analysis which would be difficult or impossible when applied directly to the hadrons. Grigoriev et al. [hep-ph/0301185] provide a brief introduction to the subject of jet finding algorithms and a general review of the physics of jets can be found in [Rep. Prog. Phys. 36 (1993) 1067].Method of solution: The software we provide is an implementation of the so-called optimal jet definition (OJD). The theory of OJD was developed by Tkachov [Phys. Rev. Lett. 73 (1994) 2405; 74 (1995) 2618; Int. J. Mod. Phys. A 12 (1997) 5411; 17 (2002) 2783]. The desired jet configuration is obtained as the one that minimizes , a certain function of the input particles and jet configuration.Restrictions on the complexity of the program: The size of the largest data structure the program uses is (maximal number of particles in the input) × (maximal number of jets in the output) × 8 bytes. (For the standard settings <1 MB). Therefore, there is no memory restriction for any conceivable application for which the program was designed.Typical running time: The running time depends strongly on the physical process being analyzed and the parameters used. For the benchmark process we studied, , with the average number of ∼80 particles in the input, the running time was <10−2s on a modest PC (per event with n_tries=1). For a fixed number of jets the complexity of the algorithm grows linearly with the number of particles (cells) in the input, in contrast with other known jet finding algorithms for which this dependence is cubic. The reader is referred to Grigoriev et al. [hep-ph/0301185] for a more detailed discussion of this issue.     

Mechanical properties of chromium-manganese austenite steels in a hydrogen environment

We study the influence of gaseous hydrogen on the mechanical properties of hardened and deformed specimens of 07Kh13G20AN4 and 03Kh13N9G19AM2 steels under a pressure of 35 MPa in the temperature range 293–773 K. We establish that hydrogen causes the strain martensite transformation of nitrogen-containing austenite stable in air. Formation of a polygonal dislocation substructure by means of preliminary mechanical or thermomechanical treatment significantly decreases the tendency of steels toward hydrogen degradation. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 5, pp. 75–78, September–October, 1999.     

Antifriction properties of heat-resistant alloys in hydrogen

We investigate the influence of hydrogen on friction properties of heat-resistant KhN55MBYu alloy and establish the main regularities of variation in the sliding friction coefficient in the process of operation of a shaft-bush couple depending on the temperature and pressure of hydrogen as well as on the rate and type of loading. Some recommendations concerning the efficient use of certain plasma and self-lubricating coatings for the operation of valve hydrogen engines are given. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 36, No. 2, pp. 108–112, March-April, 2000.     

Effect of Hydrogen on the Properties of Structural Steels

We describe the principal achievements of the Physicomechanical Institute of the Ukrainian Academy of Sciences in the field of investigations of the hydrogen degradation of metals. Hydrogen localization is considered to be the main cause of changes in the properties of metals by the decohesion mechanism. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 4, pp. 107–110, July–August, 2005.     

Methodological Aspects of Determination of Hydrogen Resistance of Steels

We consider main conditions of the adequate estimation of degradation of mechanical properties of chromium–nickel alloys in gaseous hydrogen. We establish that evacuation is a necessary procedure for preparing a working chamber for testing. The low-cycle fatigue and relative contraction are the most sensitive to hydrogen embrittlement. We determine the strain rate and hydrogen pressure that maximally impair mechanical properties.     

New method for measurement of complex magnetic permeability in themillimeter-wave range, part II: hexaferrites

Magneto-optical methods were applied for the first time in millimeter wavelength range for characterization of anisotropic ferrites. The principles of the free-space magneto-optical method are presented and the new experimental procedures leading to the determination of millimeter-wave permeability and permittivity in anisotropic ferrite materials are described. The measurements were performed with a computer-controlled W-band (70-120 GHz) quasi-optical-waveguide bridge. A backward-wave oscillator was used as a source of tunable millimeter wave radiation. The oriented Sr-hexaferrite ceramic was selected for the verification of millimeter-wave magneto-optical method. The magneto optical measurements in transverse configuration revealed strong anomalous dispersion in the millimeter-wave refractive index spectrum for Sr hexaferrite, mainly due to the frequency variation of magnetic permeability. Computer simulations revealed a good agreement of measured parameters with known data for Sr hexaferrite. It was shown that the free-carrier absorption (σ~0.05 Ω^-1 cm^-1) and magnetic permeability contribute to the relatively high millimeter-wave losses in hexaferrite ceramics. The frequency dependence of Faraday rotation in the millimeter-wave range was measured, and the experimental results are discussed. The results presented in this paper demonstrate that this new magneto-optical method is capable of providing accurate dielectric and magnetic data in the millimeter-wavelength range     

Synthesis of carbon nanotubes from acetone

The process of synthesizing carbon nanotubes (CNTs) using the method of catalytic gas-phase pyrolysis has been studied using acetone as a source of carbon. CNTs with outer diameters of 8–10 nm were prepared. The highest yield of the CNTs with the best quality is achieved when (Co, Mo)/MgO-Al₂O₃ catalyst is used. When (Fe, Co, Mo)/Al₂O₃ is used, the yield and quality of CNTs are lower. For comparison, CNTs obtained on the same catalysts but with propylene as the source of carbon have been investigated. It has been shown that, in this case, the best yield is achieved if (Fe, Co, Mo)/Al₂O₃ catalyst is used. According to the thermogravimetric data, CNT prepared at optimal conditions from acetone have fewer structural defects than those prepared from polypropylene. The optimal temperature and concentration conditions of the CNT synthesis from acetone have been determined. Based on the kinetic data, it has been assumed that the growth of CNTs takes place due to the ketene formed under the thermal decomposition of acetone. The ecological aspects of the CNT preparation from hydrocarbons and acetone are considered.     

Specific features of the deformation of steels in hydrogen

We have studied the effect of hydrogen on the mechanical properties of foils made of 08Kh18N12T steel under uniaxial tension. The initial stages of deformation in hydrogen require forces smaller by a factor of 3–5. In the case of biaxial tension of membranes made of this steel, their deformation ability also increases. The effect of hydrogen on the axial residual stresses of the first kind in 08Kh18N12T, 40Kh, and ShKh15 steels manifests itself in the activation of tensile deformation (inducing of compressive stresses). We have recorded a 30% increase in the fatigue limit of an austenitic alloy in hydrogen with a pressure of 30 MPa (the reference medium is air). __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 4, pp. 84–88, July–August, 2008.