2,805 research outputs found
Simple singularities of multigerms of curves
We classify stably simple reducible curve singularities in complex spaces of
any dimension. This extends the same classification of of irreducible curve
singularities obtained by V.I.Arnold. The proof is essentially based on the
method of complete transversals by J.W.Bruce et al.Comment: 18 page
QED Bremsstrahlung in decays of electroweak bosons
Isolated lepton momenta, in particular their directions are the most
precisely measured quantities in pp collisions at LHC. This offers
opportunities for multitude of precision measurements. It is of practical
importance to verify if precision measurements with lep- tons in the final
state require all theoretical effects evaluated simultaneously or if QED
bremsstrahlung in the final state can be separated without unwanted precision
loss. Results for final state bremsstrahlung in the decays of narrow resonances
are obtained from the Feynman rules of QED in an unambiguous way and can be
controlled with a very high precision. Also for resonances of non-negligible
width, if calculations are appropriately performed, such separation from the
remaining electroweak effects can be expected. Our paper is devoted to
validation that final state QED bremsstrahlung can indeed be separated from the
rest of QCD and electroweak effects, in the production and decay of Z and W
bosons, and to estimation of the resulting systematic error. The quantitative
discussion is based on Monte Carlo programs PHOTOS and SANC, as well as on KKMC
which is used for benchmark results. We show, that for a large classes of W and
Z boson observables as used at LHC, theoretical error on photonic
bremsstrahlung is 0.1 or 0.2%, depending on the program options used. An
overall theoretical error on QED final state radiation, i.e. taking into
account missing corrections due to pair emission and interference with initial
state radiation is estimated respectively at 0.2% or 0.3% again depending on
the program option used.Comment: 1+28 pages, 20 figure
Extra lepton pair emission corrections to Drell-Yan processes in PHOTOS and SANC
In the paper we present results for final state emissions of lepton pairs in
decays of heavy intermediate states such as Z boson. Short presentations of
PHOTOS and SANC algorithms and physics assumptions are given. Numerical
distributions of relevance for LHC observables are shown. They are used in
discussions of systematic errors in the predictions of pair emissions as
implemented in the two programs. Suggestions for the future works are given.
Present results confirm, that for the precision of 0.3% level, in simulation of
final state the pair emissions can be avoided. For the precision of 0.1-0.2%,
the results obtained with the presented programs should be enough. To cross
precision tag of 0.1%, the further work is however required.Comment: 21 pages, 12 figure
Electrotransport and magnetic properies of Cr-GaSb spintronic materials synthesized under high pressure
Electrotarnsport and magnetic properties of new phases in the system Cr-GaSb
were studied. The samples were prepared by high-pressure (P=6-8 GPa)
high-temperature treatment and identified by x-ray diffraction and scanning
electron microscopy (SEM). One of the CrGaSb phases with an
orthorhombic structure has a combination of ferromagnetic and
semiconductor properties and is potentially promising for spintronic
applications. Another high-temperature phase is paramagnetic and identified as
tetragonal
The "Horizon-T" Experiment: Extensive Air Showers Detection
Horizon-T is an innovative detector system constructed to study Extensive Air
Showers (EAS) in the energy range above 10^16 eV coming from a wide range of
zenith angles (0 - 85 degrees). The system is located at Tien Shan
high-altitude Science Station of Lebedev Physical Institute of the Russian
Academy of Sciences at approximately 3340 meters above the sea level. It
consists of eight charged particle detection points separated by the distance
up to one kilometer as well as optical detector subsystem to view the
Vavilov-Cerenkov light from the EAS. The time resolution of charged particles
and Vavilov-Cerenkov light photons passage of the detector system is a few ns.
This level of resolution allows conducting research of atmospheric development
of individual EAS.Comment: Initial technical note for Horizon-T experiment, updated with recent
detector upgrades, 11/2016. Updated 12/2017 with minor edits. Large upgrade
will be in another articl
Electroweak Effects in Neutral Current Drell-Yan Processes within SANC System
The complete one-loop electroweak radiative corrections to the neutral
current Drell-Yan process are presented for the case of
longitudinal polarization of initial particles. The calculations are based on
the SANC computer system. The paper contains a brief description of the SANC
approach and a discussion of the sources of theoretical uncertainties in
electroweak effects
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