284 research outputs found
Transient domain walls and lepton asymmetry in the Left-Right symmetric model
It is shown that the dynamics of domain walls in Left-Right symmetric models,
separating respective regions of unbroken SU(2)_L and SU(2)_R in the early
universe, can give rise to baryogenesis via leptogenesis. Neutrinos have a
spatially varying complex mass matrix due to CP-violating scalar condensates in
the domain wall. The motion of the wall through the plasma generates a flux of
lepton number across the wall which is converted to a lepton asymmetry by
helicity-flipping scatterings. Subsequent processing of the lepton excess by
sphalerons results in the observed baryon asymmetry, for a range of parameters
in Left-Right symmetric models.Comment: v2 version accepted for publication in Phys. Rev. D. Discussion in
Introduction and Conclusion sharpened. Equation (12) corrected. 16 pages, 3
figure files, RevTeX4 styl
Pulsar kicks from a dark-matter sterile neutrino
We show that a sterile neutrino with mass in the 1-20 keV range and a small
mixing with the electron neutrino can simultaneously explain the origin of the
pulsar motions and the dark matter in the universe. An asymmetric neutrino
emission from a hot nascent neutron star can be the explanation of the observed
pulsar velocities. In addition to the pulsar kick mechanism based on resonant
neutrino transitions, we point out a new possibility: an asymmetric
off-resonant emission of sterile neutrinos. The two cases correspond to
different values of the masses and mixing angles. In both cases we identify the
ranges of parameters consistent with the pulsar kick, as well as cosmological
constraints.Comment: 5 pages, 2 figures; final version; discussion and references adde
The ARGO-YBJ Experiment Progresses and Future Extension
Gamma ray source detection above 30TeV is an encouraging approach for finding
galactic cosmic ray origins. All sky survey for gamma ray sources using wide
field of view detector is essential for population accumulation for various
types of sources above 100GeV. To target the goals, the ARGO-YBJ experiment has
been established. Significant progresses have been made in the experiment. A
large air shower detector array in an area of 1km2 is proposed to boost the
sensitivity. Hybrid detection with multi-techniques will allow a good
discrimination between different types of primary particles, including photons
and protons, thus enable an energy spectrum measurement for individual specie.
Fluorescence light detector array will extend the spectrum measurement above
100PeV where the second knee is located. An energy scale determined by balloon
experiments at 10TeV will be propagated to ultra high energy cosmic ray
experiments
High Altitude test of RPCs for the ARGO-YBJ experiment
A 50 m**2 RPC carpet was operated at the YangBaJing Cosmic Ray Laboratory
(Tibet) located 4300 m a.s.l. The performance of RPCs in detecting Extensive
Air Showers was studied. Efficiency and time resolution measurements at the
pressure and temperature conditions typical of high mountain laboratories, are
reported.Comment: 16 pages, 10 figures, submitted to Nucl. Instr. Met
Partial Wave Analysis of
BES data on are presented. The
contribution peaks strongly near threshold. It is fitted with a
broad resonance with mass MeV, width MeV. A broad resonance peaking at 2020 MeV is also required
with width MeV. There is further evidence for a component
peaking at 2.55 GeV. The non- contribution is close to phase
space; it peaks at 2.6 GeV and is very different from .Comment: 15 pages, 6 figures, 1 table, Submitted to PL
Early carboniferous brachiopod faunas from the Baoshan block, west Yunnan, southwest China
38 brachiopod species in 27 genera and subgenera are described from the Yudong Formation in the Shidian-Baoshan area, west Yunnan, southwest China. New taxa include two new subgenera: Unispirifer (Septimispirifer) and Brachythyrina (Longathyrina), and seven new species: Eomarginifera yunnanensis, Marginatia cylindrica, Unispirifer (Unispirifer) xiangshanensis, Unispirifer (Septimispirifer) wafangjieensis, Brachythyrina (Brachythyrina) transversa, Brachythyrina (Longathyrina) baoshanensis, and Girtyella wafangjieensis. Based on the described material and constraints from associated coral and conodont faunas, the age of the brachiopod fauna from the Yudon Formation is considered late Tournaisian (Early Carboniferous), with a possibility extending into earlyViseacutean.<br /
Dynamic protein methylation in chromatin biology
Post-translational modification of chromatin is emerging as an increasingly important regulator of chromosomal processes. In particular, histone lysine and arginine methylation play important roles in regulating transcription, maintaining genomic integrity, and contributing to epigenetic memory. Recently, the use of new approaches to analyse histone methylation, the generation of genetic model systems, and the ability to interrogate genome wide histone modification profiles has aided in defining how histone methylation contributes to these processes. Here we focus on the recent advances in our understanding of the histone methylation system and examine how dynamic histone methylation contributes to normal cellular function in mammals
- …