119354521
Inflation in string inspired cosmology and suppression of CMB low multipoles
We construct a string-inspired nonsingular cosmological scenario in which an inflaton field is driven up the potential before the graceful exit by employing a low-energy string effective action with an orbifold compactification. This sets up an initial condition for the inflaton to lead to a sufficient number of e-foldings and to generate a nearly scale-invariant primordial density perturbation during slow-roll inflation. Our scenario provides an interesting possibility to explain a suppressed power spectrum at low multipoles due to the presence of the modulus-driven phase prior to slow-roll inflation and thus can leave a strong imprint of extra dimensions in observed CMB anisotropies.
119071739
Gravitational leptogenesis and neutrino mass limit
Recently Davoudiasl et al. (hep-ph/0403019) have introduced a new type of interaction between the Ricci scalar R and the baryon current ${J}^{\ensuremath{\mu}},$ ${\ensuremath{\partial}}_{\ensuremath{\mu}}{\mathrm{RJ}}^{\ensuremath{\mu}}$ and proposed a mechanism for baryogenesis, the gravitational baryogenesis. Generally, however, ${\ensuremath{\partial}}_{\ensuremath{\mu}}R$ vanishes in the radiation-dominated era. In this paper we consider a generalized form of their interaction ${\ensuremath{\partial}}_{\ensuremath{\mu}}{f(R)J}^{\ensuremath{\mu}}$ and study again the possibility of gravitational baryo(lepto)genesis. Taking $f(R)\ensuremath{\sim}\mathrm{ln}R,$ we will show that ${\ensuremath{\partial}}_{\ensuremath{\mu}}f(R)\ensuremath{\sim}{\ensuremath{\partial}}_{\ensuremath{\mu}}R/R$ does not vanish and the required baryon number asymmetry can be naturally generated in the early universe.
119108700
Cosmological CPT-violation, baryo/leptogenesis and CMB polarization
In this Letter we study the cosmological CPT-violation and its implications in baryo/leptogenesis and CMB polarization. We propose specifically a variant of the models of gravitational leptogenesis. By performing a global analysis with the Markov Chain Monte Carlo (MCMC) method, we find the current CMB polarization observations from the three-year WMAP (WMAP3) and the 2003 flight of BOOMERANG (B03) data provide a weak evidence for our model. However to verify and especially exclude this type of mechanism for baryo/leptogenesis with cosmological CPT-violation, the future measurements on CMB polarization from PLANCK and CMBpol are necessary.
119327390
Cosmological evolution of interacting dark energy models with mass varying neutrinos
In this paper we consider the cosmological implications of dark energy models with a coupled system of a dynamical scalar field (the quintessence) and the neutrinos. By detailed numerical calculations we study the various possibilities on the evolution and the fates of the Universe in this class of models. Our results show that due to the interaction with quintessence, neutrinos could be dominant over the quintessence in the future universe, however would eventually decay away.
119362091
Adiabatic gravitational perturbation during reheating
We study the possibilities of parametric amplification of the gravitational perturbation during reheating in single-held inflation models. Our result shows that there is no additional growth of the super-horizon modes beyond the usual predictions.
118693182
The high energy neutrino nuisance at a medium baseline reactor experiment
10 years from now medium baseline reactor experiments will attempt to determine the neutrino mass hierarchy from quantities associated to the Fourier transformed neutrino spectra. Recently Qian et al. have claimed that this goal may be impeded by the strong dependence of these quantities on the reactor neutrino flux and on slight variations of vertical bar Delta M-32(2)vertical bar. We demonstrate that this effect results from a spurious dependence of the quantities on the very high energy (8+ MeV) tail of the reactor neutrino spectrum. This dependence is spurious because the high energy tail depends upon decays of exotic isotopes and is insensitive to the mass hierarchy. An energy-dependent weight in the Fourier transform eliminates this spurious dependence without decreasing the chance of correctly determining the hierarchy. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
16809708
Results from the analysis of data collected with a 50m2 RPC carpet at YangBaJing
An RPC carpet covering similar to 10(4) m(2) (ARGO-YBJ experiment) will be installed in the YangBaJing Laboratory (Tibet, People's Republic of China) at an altitude of 4300 m a.s.l. A test-module of similar to 50 m(2) has been put in operation in this laboratory and about 10(6) air shower events have been collected. The RPC performance at high altitude and the carpet capability of reconstructing the shower features are presented. (C) 2000 Elsevier Science B.V. All rights reserved.
122356247
Automatic analysis of the emulsion chamber using the image scanner applied to the Tibet hybrid experiment
A new method of emulsion chamber analysis by using an image scanner is developed in order to process a large number of X-ray films used in the Tibet hybrid experiment which is carried out to observe primary proton spectrum in the PeV region. The experimental procedure in this method consists of multiple steps of processing the image of the X-ray films, i.e. the detection of cascade showers induced by high-energy γ-rays, the noise reduction, the spatial reconstruction of γ-families and their energy determination. The quality of the results obtained by the new method is compared with that obtained by the current manual method or Monte Carlo simulations. It is shown that sufficiently high quality of the emulsion chamber analysis is realized by the automatic method both in energy and geometrical resolution.
118548008
A New Multi-wavelength Solar Telescope: Optical and Near-infrared Solar Eruption Tracer (ONSET)
A new multi-wavelength solar telescope, the Optical and Near-infrared Solar Eruption Tracer (ONSET) of Nanjing University, has been constructed. It was fabricated at the Nanjing Institute of Astronomical Optics & Technology, and the operation is jointly administered with Yunnan Astronomical Observatory. ONSET is able to observe the Sun in three wavelength windows: He I 10830 angstrom, H alpha and white-light at 3600 angstrom and 4250 , which are selected in order to simultaneously record the dynamics of the corona, chromosphere and photosphere respectively. Full-disk or partial-disk solar images with a field of 10' at three wavelengths can be obtained nearly simultaneously. It is designed to trace solar eruptions with high spatial and temporal resolutions. This telescope was installed at a new solar observing site near Fuxian Lake in Yunnan Province, southwest China. The site is located at E102N24, with an altitude of 1722 m. The seeing is stable and has high quality. We give a brief description of the scientific objectives and the basic structure of ONSET. Some preliminary results are also presented.
117747714
Study on multifractal structure of the distribution fluctuation of secondary particles in the core region of EAS
The differences of space distributions and time profiles between the gamma-ray and proton induced shower particles are studied using Monte Carlo simulation data. The multifractal analysis is performed with the G-moment method for the distribution fluctuation of secondary particles near the core of showers induced by gamma-rays and protons. From the spectrum functions of gamma and proton events, it is seen that this method can be adopted as a basis for the gamma/proton separation. It is shown that the separation of gamma and proton can be achieved with a good efficiency in the energy region of 1-10TeV.
15875750
The use of RPC in the ARGO-YBJ project
We present the ARGO-YBJ experiment, a full coverage detector placed at high altitude (∼4300 m a.s.l.) that exploits the RPC technique. Results of a test experiment performed at Yanbajing site, with a full coverage RPC carpet of 50 m2 are also presented.