124513063
What can we learn from the tension between PLANCK and BICEP2 data?
Recently BICEP2 collaboration has announced the detection of the primordial gravitational waves at high confidence level. In light of the results of B-modes power spectrum from BICEP2 and using the based ΛCDM, a constraint on the tensor-to-scalar ratio r = 0.20−0.05+0.07 (68% C.L.) can be obtained, however, this result is in apparent tension with the limit on standard inflation models from the recent PLANCK measurement, r < 0.11 (95% C.L.). Herein we review the recent progress on the cosmological studies after BICEP2 and discuss on different ways of reconciling the tension between PLANCK and BICEP2 data. We will discuss possible modifications on the standard cosmological model, such as including the running of scalar spectral index or other cosmological parameters correlated with inflationary cosmological parameters, or tilting the primordial power spectrum at large scales by introducing a cut off which can be predicted by bouncing cosmology. We will also comment on another possibility of generating extra B-modes of CMB polarization, namely by a non-zero polarization rotation angle during its transferring from the last scattering surface.
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.
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.
117037888
Global fitting analysis on cosmological models after BICEP2
Recently, BICEP2 collaboration has released their results on the measurements of the CMB polarizations. In the framework of the $\Lambda$CDM with a power law form of the scalar primordial power spectrum, this new measurement on the B-mode puts a tight constraint on tensor/scalar ratio $r=0.2^{+0.07}_{-0.05}~(1\sigma)$, which however is in tension with the Planck limit, $r<0.11$ (95% C.L.). In this paper, we consider various extensions of the $\Lambda$CDM model by introducing extra cosmological parameters such as the equation state of dark energy $w$, the curvature of the universe $\Omega_k$, the running of the scalar power spectrum index $\alpha_s$, the sum of the neutrino mass $\Sigma m_{\nu}$, the effective number of neutrinos $N_{eff}$, the tensor power spectrum index $n_{t}$, then perform the global fit to the BICEP2, Planck and also the SN and BAO data. Our results show the cosmological parameters $\alpha_s$ and $n_t$ are highly and directly correlated with the tensor/scalar ratio $r$. However indirectly the parameters $\Omega_k$ and $N_{eff}$ are also correlated with $r$. We will in this paper give the numerical values on the parameters introduced and show explicitly how the tension between the BICEP2 and Planck is effectively alleviated by the inclusion of the parameters $\Omega_k$, $\alpha_s$, $N_{eff}$ and $n_{t}$ separately.
14959007
Gravity in a model of multi-branes alternated between Minkowski and AdS spacetime in the fifth dimension
We construct in this Letter a multi-brane model with Minkowski and AdS spacetime alternated in the fifth dimension and study the gravity on the brane of our universe. We will show that in this model there are both the graviton-like resonant state which generates the "quasi-localized gravity" and the resonant states of the massive KK mode. This model gives rise to gravity which deviates from the Newton gravitational potential at small and large scale which, however can be shown to be consistent with the observations in the absence of fine-tuning of the model parameters. (C) 2002 Elsevier Science B.V. All rights reserved.
14998446
The FCNC top-squark decay as a probe of squark mixing
In supersymmetry (SUSY) the flavor mixing between top-squark (stop) and charm-squark (scharm) induces the flavor-changing neutral-current (FCNC) stop decay t̃1 → cχ̃1. Searching for this decay serves as a probe of soft SUSY breaking parameters. Focusing on the stop pair production followed by the FCNC decay of one stop and the charge-current decay of the other stop, we investigate the potential of detecting this FCNC stop decay at the Fermilab Tevatron, the CERN Large Hadron Collider (LHC) and the next-generation ee linear collider (LC). We find that this decay may not be accessible at the Tevatron, but could be observable at the LHC and the LC with high sensitivity for some part of parameter space. 14.80.Ly, 11.30.Hv Typeset using REVTEX
14865448
Performance of the RPCs for the ARGO detector operated at the YangBaJing laboratory (4300 m a.s.l.)
Bakelite RPCs, assembled according to the ARGO design, have been operated in the high altitude Laboratory of YBJ using dedicated electronics to pick-up the streamer signal. Here we report on the results concerning absorbed current, single counting rate, efficiency and time resolution. Environmental data concerning the operating temperature inside the ARGO experimental hall are also reported.
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.
108549890
A fast Time‐of‐Flight detector also used as a tracker
We present a possible scheme for a fast Time‐of‐Flight detector which could also serve as part of the charged particle tracking system. The detector consists of scintillating fibers read out by newly developed microchannel plate photomultipliers. The performance of the detector in the experimental environment of the τ/charm factory was investigated by a detailed Monte Carlo simulation. The time and space resolutions of the detector are expected to be about 92 ps and 140 μm, respectively.
16277502
High altitude test of RPCs for the Argo YBJ experiment
Abstract A 50 m 2 RPC carpet was operated at the YanBaJin 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.
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.