113 research outputs found
Measurement of Lambda and Lambda-bar polarization in muon neutrino charged current interactions in NOMAD
The Lambda and Lambda-bar polarizations in muon neutrino charged current
interactions have been measured in the NOMAD experiment. The event sample (8087
reconstructed Lambda's and 649 Lambda-bar's) is more than an order of magnitude
larger than that of previous bubble chamber experiments, while the quality of
event reconstruction is comparable. For the Lambda hyperons we observe negative
polarization along the W-boson direction which is enhanced in the target
fragmentation region: Px(xF < 0) = -0.21 +- 0.04 (stat) +- 0.02 (sys). In the
current fragmentation region we find Px(xF > 0) = -0.09 +- 0.06 (stat) +-
0.03(sys). A significant transverse polarization (in the direction orthogonal
to the Lambda production plane) has been observed for the first time in a
neutrino experiment: Py = -0.22 +- 0.03 (stat) +- 0.01 (sys). The dependence of
the absolute value of Py on the Lambda transverse momentum with respect to the
hadronic jet direction is in qualitative agreement with the results from
unpolarized hadron-hadron experiments. The polarization vector of Lambda-bar
hyperons measured for the first time in neutrino interactions is found to be
consistent with zero.Comment: 5 pages, a contrubution to DIS2002 Conference, Cracow (April, 29 -
May, 4
Sterile Neutrino. A short introduction
This is a pedagogical introduction to the main concepts of the sterile
neutrino - a hypothetical particle, coined to resolve some anomalies in
neutrino data and retain consistency with observed widths of the and
bosons. We briefly review existing anomalies and the oscillation parameters
that best describe these data. We discuss in more detail how sterile neutrino
can be observed, as well as the consequences of its possible existence. In
particular, we pay attention to a possible loss of coherence in a model of
neutrino oscillations with sterile neutrinos, where this effect might be of a
major importance with respect to the 3 model. The current status of
searches for a sterile neutrino state is also briefly reviewed.Comment: contribution to VLVnT2018 Conferenc
Measurement of Lambda polarization in muon neutrino charged current interactions in NOMAD
The Lambda polarization in muon neutrino charged current interactions has
been measured in the NOMAD experiment. We observe negative polarization along
the W - boson direction which is enhanced in the target fragmentation region:
Px (xF < 0) = -0.21 +/- 0.04(stat) +/- 0.02(sys). In the current
fragmentation region we find: Px (xF > 0) = -0.09 +/- 0.06(stat) +/- 0.03(sys).
These results provide a test of different models describing the nucleon spin
composition and the spin transfer mechanisms. A significant transverse
polarization (in the direction orthogonal to the Lambda production plane) has
been observed for the first time in a neutrino experiment: Py = -0.22 +/-
0.03(stat) +/- 0.01(sys). The dependence of the absolute value of Py on the
Lambda transverse momentum with respect to the hadronic jet direction is in
qualitative agreement with the results from unpolarized hadron-hadron
experiments.Comment: a talk given at SPIN2000 (Osaka) symposium, October 16-21 (5 pages
Recent results from Daya Bay experiment
This manuscript is a short summary of my talk given at ICNFP2014 Conference.
Here we report on new results of and measurements, search for the sterile neutrino within domain and precise measurement
of the reactor absolute antineutrino flux.Comment: 10 pages, 5 figure
Recent results in neutrino physics
This manuscript is a shorthand version of my talk given at Odessa Gamov
School on Astronomy, Cosmology and Beyond (22-28 August 2011, Odessa, Ukraine).
Within this note we very briefly review the main achievements, new results and
open problems in neutrino physics of today.Comment: An invited plenar talk at "The XIth G. Gamow's Odessa Astronomical
Summer Conference-School, 22-28 August, 2011, Odessa, Ukraine", 6 pages
http://www.astro-soc.odessa.ua
Intrinsic Polarized Strangeness and Lambda Polarization in Deep-Inelastic Production
We propose a model for the longitudinal polarization of Lambda baryons
produced in deep-inelastic lepton scattering at any xF, based on static SU(6)
quark-diquark wave functions and polarized intrinsic strangeness in the nucleon
associated with individual valence quarks. Free parameters of the model are
fixed by fitting NOMAD data on the longitudinal polarization of Lambda hyperons
in neutrino collisions. Our model correctly reproduces the observed dependences
of Lambda polarization on the kinematic variables. Within the context of our
model, the NOMAD data imply that the intrinsic strangeness associated with a
valence quark has anticorrelated polarization. We also compare our model
predictions with results from the HERMES and E665 experiments using charged
leptons. Predictions of our model for the COMPASS experiment are also
presented
Biomass of Scyphozoan Jellyfish, and Its Spatial Association with 0-Group Fish in the Barents Sea
An 0-group fish survey is conducted annually in the Barents Sea in order to estimate fish population abundance. Data on jellyfish by-catch have been recorded since 1980, although this dataset has never been analysed. In recent years, however, the ecological importance of jellyfish medusae has become widely recognized. In this paper the biomass of jellyfish (medusae) in 0–60 m depths is calculated for the period 1980–2010. During this period the climate changed from cold to warm, and changes in zooplankton and fish distribution and abundance were observed. This paper discusses the less well known ecosystem component; jellyfish medusae within the Phylum Cnidaria, and their spatial and temporal variation. The long term average was ca. 9×108 kg, with some years showing biomasses in excess of 5×109 kg. The biomasses were low during 1980s, increased during 1990s, and were highest in early 2000s with a subsequent decline. The bulk of the jellyfish were observed in the central parts of the Barents Sea, which is a core area for most 0-group fishes. Jellyfish were associated with haddock in the western area, with haddock and herring in the central and coastal area, and with capelin in the northern area of the Barents Sea. The jellyfish were present in the temperature interval 1°C<T<10°C, with peak densities at ca. 5.5°C, and the greatest proportion of the jellyfish occurring between 4.0–7.0°C. It seems that the ongoing warming trend may be favourable for Barents Sea jellyfish medusae; however their biomass has showed a recent moderate decline during years with record high temperatures in the Barents Sea. Jellyfish are undoubtedly an important component of the Barents Sea ecosystem, and the data presented here represent the best summary of jellyfish biomass and distribution yet published for the region
Molecular evolution of cyclin proteins in animals and fungi
<p>Abstract</p> <p>Background</p> <p>The passage through the cell cycle is controlled by complexes of cyclins, the regulatory units, with cyclin-dependent kinases, the catalytic units. It is also known that cyclins form several families, which differ considerably in primary structure from one eukaryotic organism to another. Despite these lines of evidence, the relationship between the evolution of cyclins and their function is an open issue. Here we present the results of our study on the molecular evolution of A-, B-, D-, E-type cyclin proteins in animals and fungi.</p> <p>Results</p> <p>We constructed phylogenetic trees for these proteins, their ancestral sequences and analyzed patterns of amino acid replacements. The analysis of infrequently fixed atypical amino acid replacements in cyclins evidenced that accelerated evolution proceeded predominantly during paralog duplication or after it in animals and fungi and that it was related to aromorphic changes in animals. It was shown also that evolutionary flexibility of cyclin function may be provided by consequential reorganization of regions on protein surface remote from CDK binding sites in animal and fungal cyclins and by functional differentiation of paralogous cyclins formed in animal evolution.</p> <p>Conclusions</p> <p>The results suggested that changes in the number and/or nature of cyclin-binding proteins may underlie the evolutionary role of the alterations in the molecular structure of cyclins and their involvement in diverse molecular-genetic events.</p
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