177 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
Extended Grimus-Stockinger theorem and inverse square law violation in quantum field theory
We study higher-order corrections to the Grimus-Stockinger theorem dealing
with the large-distance asymptotic behavior of the wave-packet modified
neutrino propagator within the framework of field-theoretical description of
the neutrino oscillation phenomenon. We discuss the possibility that these
corrections are responsible for breakdown of the classical inverse-square law
(ISL) at the macroscopic distances. In particular the ISL violation can be an
explanation of the well-known reactor antineutrino anomaly.Comment: 11 pages, no figures. Some additions are done and references are
adde
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
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
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