101 research outputs found
Многокомпонентные смесевые биотоплива для дизельных двигателей
The characteristic features of using multi-propellant mixed biofuels with rapeseed oil in diesel engines have been considered. The results of experimental research of a type D-245.12S vehicle diesel engine running on diesel fuel, rapeseed oil, rapeseed oil methyl ester and gasoline multi-propellant mix-tures have been shown. The dependence of fuel efficiency and exhaust emission characteristics on mixed biofuel components has been shown.В статье рассмотрены особенности использования в дизелях многокомпонентных биотоплив, получаемых с использованием рапсового масла. Представлены результаты экспериментальных исследований транспортного дизеля типа Д-245.12С, работающего на смесях дизельного топлива, рапсового масла, метилового эфира рапсового масла и бензина. Показана зависимость показателей топливной экономичности и токсичности отработавших газов от состава смесевого биотоплива
Heavy ion event generator HYDJET++ (HYDrodynamics plus JETs)
HYDJET++ is a Monte-Carlo event generator for simulation of relativistic
heavy ion AA collisions considered as a superposition of the soft, hydro-type
state and the hard state resulting from multi-parton fragmentation. This model
is the development and continuation of HYDJET event generator (Lokhtin &
Snigirev, 2006, EPJC, 45, 211). The main program is written in the
object-oriented C++ language under the ROOT environment. The hard part of
HYDJET++ is identical to the hard part of Fortran-written HYDJET and it is
included in the generator structure as a separate directory. The soft part of
HYDJET++ event is the "thermal" hadronic state generated on the chemical and
thermal freeze-out hypersurfaces obtained from the parameterization of
relativistic hydrodynamics with preset freeze-out conditions. It includes the
longitudinal, radial and elliptic flow effects and the decays of hadronic
resonances. The corresponding fast Monte-Carlo simulation procedure, C++ code
FAST MC (Amelin et al., 2006, PRC, 74, 064901; 2008, PRC, 77, 014903) is
adapted to HYDJET++. It is designed for studying the multi-particle production
in a wide energy range of heavy ion experimental facilities: from FAIR and NICA
to RHIC and LHC.Comment: 44 pages including 6 figures as EPS-files; prepared using LaTeX
package for publication in Computer Physics Communication
Tensor Correlations Measured in 3He(e,e'pp)n
We have measured the 3He(e,e'pp)n reaction at an incident energy of 4.7 GeV
over a wide kinematic range. We identified spectator correlated pp and pn
nucleon pairs using kinematic cuts and measured their relative and total
momentum distributions. This is the first measurement of the ratio of pp to pn
pairs as a function of pair total momentum, . For pair relative
momenta between 0.3 and 0.5 GeV/c, the ratio is very small at low and
rises to approximately 0.5 at large . This shows the dominance of
tensor over central correlations at this relative momentum.Comment: 4 pages, 4 figures, submitted to PR
Measurement of the nuclear multiplicity ratio for hadronization at CLAS
The influence of cold nuclear matter on lepto-production of hadrons in
semi-inclusive deep inelastic scattering is measured using the CLAS detector in
Hall B at Jefferson Lab and a 5.014 GeV electron beam. We report the
multiplicity ratios for targets of C, Fe, and Pb relative to deuterium as a
function of the fractional virtual photon energy transferred to the
and the transverse momentum squared of the . We find that the
multiplicity ratios for are reduced in the nuclear medium at high
and low , with a trend for the transverse momentum to be
broadened in the nucleus for large .Comment: Submitted to Phys. Lett.
Deep exclusive electroproduction off the proton at CLAS
The exclusive electroproduction of above the resonance region was
studied using the Large Acceptance Spectrometer () at
Jefferson Laboratory by scattering a 6 GeV continuous electron beam off a
hydrogen target. The large acceptance and good resolution of ,
together with the high luminosity, allowed us to measure the cross section for
the process in 140 (, , ) bins:
, 1.6 GeV GeV and 0.1 GeV
GeV. For most bins, the statistical accuracy is on the order of a few
percent. Differential cross sections are compared to two theoretical models,
based either on hadronic (Regge phenomenology) or on partonic (handbag diagram)
degrees of freedom. Both can describe the gross features of the data reasonably
well, but differ strongly in their ingredients. If the handbag approach can be
validated in this kinematical region, our data contain the interesting
potential to experimentally access transversity Generalized Parton
Distributions.Comment: 18pages, 21figures,2table
Precise Measurements of Beam Spin Asymmetries in Semi-Inclusive production
We present studies of single-spin asymmetries for neutral pion
electroproduction in semi-inclusive deep-inelastic scattering of 5.776 GeV
polarized electrons from an unpolarized hydrogen target, using the CEBAF Large
Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator
Facility. A substantial amplitude has been measured in the
distribution of the cross section asymmetry as a function of the azimuthal
angle of the produced neutral pion. The dependence of this amplitude
on Bjorken and on the pion transverse momentum is extracted with
significantly higher precision than previous data and is compared to model
calculations.Comment: to be submitted PL
A Bayesian analysis of pentaquark signals from CLAS data
We examine the results of two measurements by the CLAS collaboration, one of
which claimed evidence for a pentaquark, whilst the other found no
such evidence. The unique feature of these two experiments was that they were
performed with the same experimental setup. Using a Bayesian analysis we find
that the results of the two experiments are in fact compatible with each other,
but that the first measurement did not contain sufficient information to
determine unambiguously the existence of a . Further, we suggest a
means by which the existence of a new candidate particle can be tested in a
rigorous manner.Comment: 5 pages, 3 figure
First measurement of direct photoproduction on the proton
We report on the results of the first measurement of exclusive
meson photoproduction on protons for GeV and GeV. Data were collected with the CLAS detector at the Thomas
Jefferson National Accelerator Facility. The resonance was detected via its
decay in the channel by performing a partial wave analysis of the
reaction . Clear evidence of the meson
was found in the interference between and waves at GeV. The -wave differential cross section integrated in the mass range of
the was found to be a factor of 50 smaller than the cross section
for the meson. This is the first time the meson has been
measured in a photoproduction experiment
Modified structure of protons and neutrons in correlated pairs
The atomic nucleus is made of protons and neutrons (nucleons), which are themselves composed of quarks and gluons. Understanding how the quark–gluon structure of a nucleon bound in an atomic nucleus is modified by the surrounding nucleons is an outstanding challenge. Although evidence for such modification—known as the EMC effect—was first observed over 35 years ago, there is still no generally accepted explanation for its cause1,2,3. Recent observations suggest that the EMC effect is related to close-proximity short-range correlated (SRC) nucleon pairs in nuclei4,5. Here we report simultaneous, high-precision measurements of the EMC effect and SRC abundances. We show that EMC data can be explained by a universal modification of the structure of nucleons in neutron–proton SRC pairs and present a data-driven extraction of the corresponding universal modification function. This implies that in heavier nuclei with many more neutrons than protons, each proton is more likely than each neutron to belong to an SRC pair and hence to have distorted quark structure. This universal modification function will be useful for determining the structure of the free neutron and thereby testing quantum chromodynamics symmetry-breaking mechanisms and may help to discriminate between nuclear physics effects and beyond-the-standard-model effects in neutrino experiments
Evidence for the Onset of Color Transparency in Electroproduction off Nuclei
We have measured the nuclear transparency of the incoherent diffractive
process in C and Fe targets relative to H
using a 5 GeV electron beam. The nuclear transparency, the ratio of the
produced 's on a nucleus relative to deuterium, which is sensitive to
interaction, was studied as function of the coherence length (),
a lifetime of the hadronic fluctuation of the virtual photon, and the
four-momentum transfer squared (). While the transparency for both
C and Fe showed no dependence, a significant
dependence was measured, which is consistent with calculations that included
the color transparency effects.Comment: 6 pages and 4 figure
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