119544460
Two-Loop Electroweak Logarithms
We present the complete analytical result for the two-loop logarithmically enhanced contributions to the high energy asymptotic behavior of the vector form factor and the four-fermion cross section in a spontaneously broken SU(2) gauge model. On the basis of this result we derive the dominant two-loop electroweak corrections to the neutral current four-fermion processes at high energies.
15966773
Fermionic contributions to the three-loop static potential
Abstract We consider the three-loop corrections to the static potential which are induced by a closed fermion loop. For the reduction of the occurring integrals a combination of the Grobner and Laporta algorithm has been used and the evaluation of the master integrals has been performed with the help of the Mellin–Barnes technique. The fermionic three-loop corrections amount to 2% of the tree-level result for top quarks, 8% for bottom quarks and 27% for the charm quark system.
122087913
Singularities of feynman amplitudes in the momentum space
16218113
Analytical result for dimensionally regularized massless master double box with one leg off shell
Abstract The dimensionally regularized massless double box Feynman diagram with powers of propagators equal to one, one leg off the mass shell, i.e. with nonzero q 2 = p 1 2 , and three legs on shell, p i 2 =0, i=2,3,4 , is analytically calculated for general values of q 2 and the Mandelstam variables s and  t . An explicit result is expressed through (generalized) polylogarithms, up to the fourth order, dependent on rational combinations of q 2 , s and  t , and a one-dimensional integral with a simple integrand consisting of logarithms and dilogarithms.
121715808
Calculation of Feynman diagrams with zero mass threshold from their small momentum expansion
A method of calculating Feynman diagrams from their small momentum expansion [1] is extended to diagrams with zero mass thresholds. We start from the asymptotic expansion in large masses [2] (applied to the case when all $M_i^2$ are large compared to all momenta squared). Using dimensional regularization, a finite result is obtained in terms of powers of logarithms (describing the zero-threshold singularity) times power series in the momentum squared. Surprisingly, these latter ones represent functions, which not only have the expected physical “second threshold” but have a branchcut singularity as well below threshold at a mirror position. These can be understood as pseudothresholds corresponding to solutions of the Landau equations. In the spacelike region the imaginary parts from the various contributions cancel. For the two-loop examples with one mass M, in the timelike region for q2 ≈ M2 we obtain approximations of high precision. This will be of relevance in particular for the calculation of the decay Z → bb̅in the mb = 0 approximation.
12241639
Analytical evaluation of certain on-shell two-loop three-point diagrams
Abstract An analytical approach is applied to calculating some dimensionally regulated two-loop vertex diagrams with essential on-shell singularities. Such diagrams are important in evaluating the QED corrections to the muon decay, the QCD corrections to top quark decays t→W + b, t→H + b, etc.
122046947
ARES — a spectrometer for the investigation of rare particle decays and rare nuclear processes
Abstract A magnetic spectrometer intended for a wide range of investigations of rare particle and nuclear processes is described. The spectrometer consists of cylindrical proportional chambers (∼ 15000 signal wires) with gas supply and gas leakage systems, cylindrical scintillation hodoscopes, a magnet, electronics with power supplies, and a data acquisition system. Basic characteristics of the spectrometer are discussed and results of first physics experiments are presented.
124769212
Method of Bunch Phase Distribution Measurement Based on a Møller Scattering
119270809
Detector with a profile-based cathode and the two-coordinate pad-strip readout system
A detector with a profile-based cathode and a two-coordinate cathode readout system has been experimentally investigated. Cathode pads located in each profile along the anode wire are diagonally interconnected, thus forming strips that cross the detector at some angle with respect to the anode wire. Owing to the availability of the two cathode coordinates and the coordinate associated with the anode wire, it is possible to solve the problem of identifying high-multiplicity events in a single detector.
121235164
Architecture of data-acquisition systems for high-energy physics experiments
In this review we discuss the evolution of the basic principles of the architecture of data-acquisition systems for experimental setups used in high-energy physics and relativistic nuclear physics during the last 25 years. The effect of the latest advances in computational techniques and communications, such as microprocessors and open bus system standards, on improving data recording and acquisition is discussed. The evolution of data-acquisition systems is illustrated by examples of developments occurring at the leading physics centers and at the Laboratory of High Energy Physics, JINR, Dubna. The trends in the future development of data-acquisition systems are described for the research programs at the LHCcollider, CERN, and the Relativistic Heavy Ion Collider at Brookhaven National Laboratory.
125282472
Harmonic spectrum analyzer of magnetic induction