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.
11775945
Electroweak Sphaleron in Large Higgs Boson Mass Limit
Since the TRIVIALITY argument of the Higgs sector requires the existence of new physics beyond the standard model, there should exist a cutoff $\Lambda$ beyond which the standard model will breakdown. The cutoff can be determined from the position of the Landau pole. We study the effects of this cutoff on the energy of the electroweak sphaleron, $E^{spha}$, in the large Higgs boson mass limit. We found that $E^{spha}$ becomes arbitrarily large as the Higgs boson mass increases. This is in contrast to the well-known result, which is held in the standard model and a wide class of its extensions, that $E^{spha}$ is stable against the variation of the {\it bare} Higgs boson mass. The physical meaning of this result is discussed.
119524126
Anomalous global strings and primordial magnetic fields
We propose a new mechanism for the generation of primordial magnetic fields, making use of the magnetic fields which are induced by anomalous global strings, such as pion and axion strings, which couple to electromagnetism via Wess-Zumino type interactions. We calculate the magnitude and coherence length of these fields. They are seen to depend on the string dynamics. With optimistic assumptions, both the magnitude and coherence scale of the induced magnetic fields can be large enough to explain the seed magnetic fields of greater than 10{sup {minus}23} G necessary to produce the observed galactic magnetic fields via the galactic dynamo mechanism. {copyright} {ital 1999} {ital The American Physical Society}
119067588
k-essential leptogenesis
k-Essence is a possible candidate for dark energy of the Universe. In this Letter we consider couplings of k-essence to the matter fields of the standard electroweak theory and study the effects of the cosmological CPT violation induced by the CPT violating ether during the evolution of the k-essence scalar field on the laboratory experiments and baryogenesis. Our results show that the matter and antimatter asymmetry can be naturally explained via leptogenesis without conflicting with the experimental limits on CPT violation test. The mechanism for baryogenesis proposed in this Letter provides a unified picture for dark energy and baryon matter of our Universe and allows an almost degenerate neutrino mass pattern with a predicted rate on the neutrinoless double beta decays accessible to the experimental sensitivity in the near future. (C) 2003 Elsevier B.V. All rights reserved.
58887814
Showering cosmogenic muons in a large liquid scintillator
A bstractWe present the results of FLUKA simulations of the propagation of cosmogenic muons in a 20 kton spherical liquid scintillator detector underneath 700 to 900 meters of rock. A showering muon is one which deposits at least 3 GeV in the detector in addition to ionization energy. We find that 20 percent of muons are showering and a further 11 percent of muon events are muon bundles, of which more than one muon enters the detector. In this range the showering and bundle fractions are robust against changes in the depth and topography, thus the total shower and bundle rate for a given experiment can be obtained by combining our results with an estimate for the total muon flux. One consequence is that a straightforward adaptation of the full detector showering muon cuts used by KamLAND to JUNO or RENO 50 would yield a nearly vanishing detector efficiency.
17209312
THE EFFECT OF 4D EFFECTIVE COSMOLOGICAL CONSTANT ON THE STABILITY OF RANDALL–SUNDRUM SCENARIO
We study the Randall-Sundrum model with a small 4D effective cosmological constant on the brane, and drive a corrected radion potential following the Goldberger-Wise mechanism. We then discuss the effect of the 4D effective cosmological constant on the stability of the brane-system, and find that to quintessence determined by updated observation, the proper distance between the two branes required to solve the hierarchy problem can exist. However, during inflation, whether we can get a reasonable hierarchy scale is still uncertain.
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.
118189735
Studies of neutron-rich nuclei with the CLARA-PRISMA setup and description of the heavy-ion detector DANTE
A polymeric antioxidant which comprises a monomeric unit having a formula (I): (I) wherein R1 is methyl or ethyl; and a monomeric unit having a formula (II): (II) which imparts an excellent resistance against heat- or light-aging to a synthetic fiber and a resin.
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.
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.
121510906
Results from the ARGO-YBJ test experiment
Abstract A resistive plate counters (RPCs) carpet of ∼50 m 2 has been put in operation in the Yangbajing Laboratory (Tibet, P.R. China) at 4300 m a.s.l., in order to study the RPCs performance at high altitude and the detector capability of imaging the EAS disc. This test has been performed in view of an enlarged use of RPCs for the ARGO-YBJ experiment. This experiment will be devoted to a wide range of fundamental issues in cosmic rays and astroparticle physics, including in particular γ-ray astronomy and γ-ray bursts physics at energies ⩾100 GeV. In this paper we present and discuss the procedures adopted to calibrate the detector and reconstruct the shower direction. Results concerning many shower features as the angular distribution, the density spectrum, the time profile of the shower front, are found well consistent with the expectation.