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Search Results: 1 - 10 of 139520 matches for " K. Hara "
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Rare B decays with leptons at Belle
K. Hara,for the Belle Collaboration
Statistics , 2008,
Abstract: We present a new measurement of the purely leptonic decay B- -> tau- nu_tau-bar with a semileptonic B tagging method, using a data sample containing 657*10^6 BB-bar pairs collected with the Belle detector at the KEKB asymmetric e+e- collider. A sample of BB-bar pairs are tagged by reconstructing one B meson decaying semileptonically. We detect the B- -> tau- nu_tau-bar candidate in the recoil. We obtain a signal with a significance of 3.8 standard deviations including systematics, and measure the branching fraction to be B(B- -> tau- nu_tau-bar) = 1.65+0.38-0.37(stat)+0.35-0.37(syst))*10^-4. This result confirms the evidence for B- -> tau- nu_tau-bar obtained in the previous Belle measurement with a hadronic B tagging method. The B meson decay constant f_B and constraint on charged Higgs are obtained using the measured branching fraction.
Measurement of CP-Violating Parameters in $B\to η^\prime K$ Decays
K. F. Chen,K. Hara
Statistics , 2002, DOI: 10.1016/S0370-2693(02)02389-4
Abstract: We present measurements of CP-violating parameters in $B^0(\bar{B}{}^0) \to \eta^\prime K_S^0$ and $B^{\pm} \to \eta' K^{\pm}$ decays based on a 41.8 fb$^{-1}$ data sample collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+} e^{-}$ collider. We fully reconstruct one neutral $B$ meson as a $B^0(\bar{B}{}^0) \to \eta^\prime K_S^0$ CP eigenstate and identify the flavor of the accompanying $B$ from its decay products. From the distribution of time intervals between pairs of $B$ meson decay points, we obtain the CP-violating asymmetry parameters ${\mathcal S}_{\eta^\prime K_S^0} = 0.28\pm0.55(stat)^{+0.07}_{-0.08}(syst)$, and ${\mathcal A}_{\eta^\prime K_S^0} = 0.13\pm0.32(stat)^{+0.09}_{-0.06}(syst)$. We also reconstruct charged $B^{\pm} \to \eta^\prime K^{\pm}$ decays and determine a direct-CP violating asymmetry value of ${\mathcal A}_{\eta^\prime K^\pm}=(-1.5\pm7.0(stat)\pm0.9(syst))%$.
Seasonal variations and vertical features of aerosol particles in the Antarctic troposphere
K. Hara, K. Osada, C. Nishita-Hara,T. Yamanouchi
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2011,
Abstract: Tethered balloon-borne aerosol measurements were conducted at Syowa Station, Antarctica during the 46th Japanese Antarctic expedition (2005–2006). The CN concentration reached a maximum in the summer, although the number concentrations of fine particles (Dp>0.3 μm) and coarse particles (Dp>2.0 μm) increased during the winter–spring. The CN concentration was 30–2200 cm 3 near the surface (surface – 500 m) and 7–7250 cm 3 in the lower free troposphere (>1500 m). During the austral summer, higher CN concentration was often observed in the lower free troposphere, where the number concentrations in fine and coarse modes were remarkably lower. The frequent appearance of higher CN concentrations in the free troposphere relative to continuous aerosol measurements at the ground strongly suggests that new particle formation is more likely to occur in the lower free troposphere in Antarctic regions. Seasonal variations of size distribution of fine-coarse particles show that the contribution of the coarse mode was greater in the winter–spring than in summer because of the dominance of sea-salt particles in the winter–spring. The number concentrations of fine and coarse particles were high in air masses from the ocean and mid-latitudes. Particularly, aerosol enhancement was observed not only in the boundary layer, but also in the lower free troposphere during and immediately after Antarctic haze events occurring in May, July and September.
Analysis of Delta I =2 staggering in nuclear rotational spectra
K. Hara,G. A. Lalazissis
Physics , 1996, DOI: 10.1103/PhysRevC.55.1789
Abstract: A method is proposed and tested for the analysis of Delta I=2 staggering observed in nuclear rotational bands. We examine six super- and hyper-deformed bands, among which that of 149Gd and possibly of 147Gd seem to exhibit real staggering. However, we emphasize that the presence of staggering may not necessarily imply the occurrence of bifurcation. It is also shown that a similar staggering seen in normally deformed bands is a manifestation of band crossings. A more extensive analysis is planned.
Analysis of the superdefomed rotational bands
G. A. Lalazissis,K. Hara
Physics , 1997, DOI: 10.1103/PhysRevC.58.243
Abstract: All available experimental data for the $\Delta I=2$ transition energies in superdeformed bands are analyzed by using a new one-point formula. The existence of deviations from the smooth behavior is confirmed in many bands. However, we stress that one cannot necessarily speak about staggering patterns as they are mostly irregular. Simulations of the experimental data suggest that the irregularities may stem from the presence of irregular kinks in the rotational spectra. This could be a clue but, at the moment, where such kinks come from is an open question.
Analysis of Molecular Rotational Spectra
K. Hara,G. A. Lalazissis
Physics , 1997,
Abstract: Rotational spectra of diatomic molecules measured in the high-precision experiments are analyzed. Such a spectrum is usually fitted by an 8th order polynomial in spin. In fact, from the theoretical point of view, the rotational spectrum is expected to be a smooth function of spin. Thus, fitting the rotational spectrum in terms of a low order polynomial in spin seems to be justified. However, this is not what we found in the present work. We show that the measured spectrum is not necessarily a smooth function of the spin, which is quite surprising. Whether or not it indicates the presence of some hidden physics is an open question.
Triaxial projected shell model approach
J. A. Sheikh,K. Hara
Physics , 1998, DOI: 10.1103/PhysRevLett.82.3968
Abstract: The projected shell model analysis is carried out using the triaxial Nilsson+BCS basis. It is demonstrated that, for an accurate description of the moments of inertia in the transitional region, it is necessary to take the triaxiality into account and perform the three-dimensional angular-momentum projection from the triaxial Nilsson+BCS intrinsic wavefunction.
Tethered balloon-borne aerosol measurements: seasonal and vertical variations of aerosol constituents over Syowa Station, Antarctica
K. Hara,K. Osada,T. Yamanouchi
Atmospheric Chemistry and Physics Discussions , 2013, DOI: 10.5194/acpd-13-8153-2013
Abstract: Tethered balloon-borne aerosol measurements were conducted at Syowa Station, Antarctica during the 46th Japanese Antarctic expedition (2005–2006). Direct aerosol sampling was operated from near the surface to the lower free troposphere (approximately 2500 m) using a balloon-borne aerosol impactor. Individual aerosol particles were analyzed using a scanning electron microscope equipped with an energy dispersive X-ray spectrometer. Seasonal and vertical features of aerosol constituents and their mixing states were investigated. Results show that sulfate particles were dominant in the boundary layer and lower free troposphere in the summer, whereas sea-salt particles were dominant during winter–spring. Minerals, MgSO4, and sulfate containing K were identified as minor aerosol constituents in both boundary layer and free troposphere over Syowa Station. Although sea-salt particles were dominant during winter–spring, the relative abundance of sulfate particles increased in the boundary layer when air masses fell from the free troposphere over the Antarctic coast and continent. Sea-salt particles were modified considerably through heterogeneous reactions with SO42 , CH3SO3 , and their precursors during the summer, and were modified slightly through heterogeneous reactions with NO3 and its precursors. During winter–spring, sea-salt modification was insignificant, particularly in the cases of high relative abundance of sea-salt particles and higher number concentrations. In August, NO3 and its precursors contributed greatly to sea-salt modification over Syowa Station. Because of the occurrence of sea-salt fractionation on sea-ice, Mg-rich sea-salt particles were identified during April–November. In contrast, Mg-free sea-salt particles and slightly Mg-rich sea-salt particles co-existed in the lower troposphere during summer. Thereby, Mg separation can proceed by sea-salt fractionation during summer in Antarctic regions.
Quest for Potentials in the Quintessence Scenario  [PDF]
Tetsuya Hara
Journal of Applied Mathematics and Physics (JAMP) , 2016, DOI: 10.4236/jamp.2016.42027

The time evolution of the equation of state w for quintessence scenario with a scalar field as dark energy is studied up to the third derivative (d3w/da3) with respect to the scale factor a, in order to predict the future observations and specify the scalar potential parameters with the observables. The third derivative of w for general potential V is derived and applied to several types of potentials. They are the inverse power-law (V = M4 + α/Qα), the exponential ?\"\", the mixed \"\" , the cosine \"\" ?and the Gaussian types \"\" , which are prototypical potentials for the freezing and thawing models. If the parameter number for a potential form is n, it is necessary to find at least for n + 2 independent observations to identify the potential for0m and the evolution of the scalar field (Q and \"\"

The influence of the rate of selenium crystallization from aqueous solutions on its morphology
Hara?czyk I.,Szafirska B.,Fitzner K.
Journal of Mining and Metallurgy, Section B : Metallurgy , 2002, DOI: 10.2298/jmmb0202033h
Abstract: Selenium crystallization process from aqueous solutions was investigated at constant temperature of 357 K. Two different reducers were used, namely dissolved NaHSO3 and gaseous SO2. Experiments were conducted for solutions with different initial selenium concentration and different pH. The degree of conversion was determined as a function of time from the weight of the sediment, and can be described by Avrami-type equation of the following form: - ln ( 1 - á) = (6.95 . 10 -3 . t )1.52 valid at constant temperature of 357 K for NaHSO3 reducer, rate constant k = 6.95.10-3 min-1, and t in minutes. When the reduction was carried out in SO2 stream, the rate constant k was found to be strongly dependent on the flow rate. Possible mechanism of the reduction process and the influence of the rate of the reduction on the morphology of the product were suggested.
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