119288185
Radiative and leptonic decays of the pseudoscalar charmonium state eta(c)
The radiative and leptonic decays of {eta}{sub c}{yields}{gamma}{gamma} and {eta}{sub c}{yields}l{sup +}l{sup -} are studied. For a {eta}{sub c}{yields}{gamma}{gamma} decay, the second-order electromagnetic tree-level diagram gives the leading contribution. The decay rate of {eta}{sub c}{yields}{gamma}{gamma} is calculated, the prediction is in good agreement with the experimental data. For {eta}{sub c}{yields}l{sup +}l{sup -}, both the tree and loop diagrams are calculated. The analysis shows that the loop contribution dominates; the contribution of tree diagram with a Z{sup 0} intermediate state can only modify the decay rate by less than 1%. The prediction of the branching ratios of {eta}{sub c}{yields}e{sup +}e{sup -} and {mu}{sup +}{mu}{sup -} are very tiny within the standard model. The smallness of these predictions within the standard model makes the leptonic decays of {eta}{sub c} sensitive to physics beyond the standard model. Measurement of the leptonic decay may give information about new physics.
34157910
New look at the critical behavior near the threshold of black hole formation in the Russo-Susskind-Thorlacius model.
204015985
Semileptonic decay of B and D ---> K*0 (1430) anti-l nu from QCD sum rule
We calculate B-(s) and D-(s) to K-0(*)(1430) transition form factors, and study semileptonic decays of B-(s) and D-(s)-> K-0(*)(1430)(l) over bar nu based on QCD sum rule. Measuring these semileptonic decays with high statistics will give valuable information on the nature of light scalar mesons.
119119152
Analysis of a selected sample of RR Lyrae stars in the LMC from OGLE-III
A systematic study of RR Lyrae stars is performed using a selected sample of 655 objects in the Large Magellanic Cloud (LMC) with long-term observations and numerous measurements from the Optical Gravitational Lensing Experiment III project. The phase dispersion method and linear superposition of the harmonic oscillations are used to derive the pulsation frequency and properties of light variation. It is found that a dichotomy exists in Oosterhoff Type I and Oosterhoff Type II for RR Lyrae stars in the LMC. Due to our strict criteria for identifying a frequency, a lower limit for the incidence rate of Blazhko modulation in the LMC is estimated in various subclasses of RR Lyrae stars. For fundamental-mode RR Lyrae stars, the rate of 7.5% is smaller than the previous result. In the case of the first-overtone RR Lyrae variables, the rate of 9.1% is relatively high. In addition to the Blazhko variables, 15 objects are identified to pulsate in the fundamental/first-overtone double mode. Furthermore, four objects show a period ratio around 0.6, which makes them very likely to be rare pulsators in the fundamental/second-overtone double mode.
119474898
The topological branching fractions of $\tau$ decay at LEP
The paper has heen withdrawn.
27697160
350 μm Observations of Ultraluminous Infrared Galaxies at Intermediate Redshifts
We present 350 μm observations of 36 ultraluminous infrared galaxies (ULIRGs) at intermediate redshifts (0.089 ≤ z ≤ 0.926) using the Submillimeter High Angular Resolution Camera II (SHARC-II) on the Caltech Submillimeter Observatory (CSO). In total, 28 sources are detected at S/N ≥ 3, providing the first flux measurements longward of 100 μm for a statistically significant sample of ULIRGs in the redshift range 0.1 ≲ z ≲ 1.0. Combining our 350 μm flux measurements with the existing IRAS 60 and 100 μm data, we fit a single-temperature model to the spectral energy distribution (SED) and thereby estimate dust temperatures and far-IR luminosities. Assuming an emissivity index of β = 1.5, we find a median dust temperature and far-IR luminosity of T_d = 42.8 ± 7.1 K and log(L_(FIR)/L_☉) = 12.2 ± 0.5, respectively. The far-IR-radio correlation observed in local star-forming galaxies is found to hold for ULIRGs in the redshift range 0.1 ≲ z ≲ 0.5, suggesting that the dust in these sources is predominantly heated by starbursts. We compare the far-IR luminosities and dust temperatures derived for dusty galaxy samples at low and high redshifts with our sample of ULIRGs at intermediate redshift. A general L_(FIR)-T_d relation is observed, albeit with significant scatter due to differing selection effects and variations in dust mass and grain properties. The relatively high dust temperatures observed for our sample compared to that of high-z submillimeter-selected starbursts with similar far-IR luminosities suggest that the dominant star formation in ULIRGs at moderate redshifts takes place on smaller spatial scales than is found at higher redshifts.
11438036
2006 Whole Earth Telescope Observations of GD358: A New Look at the Prototype DBV
We report on the analysis of 436.1 hr of nearly continuous high-speed photometry on the pulsating DB white dwarf GD358 acquired with the Whole Earth Telescope (WET) during the 2006 international observing run, designated XCOV25. The Fourier transform (FT) of the light curve contains power between 1000 and 4000 μHz, with the dominant peak at 1234 μHz. We find 27 independent frequencies distributed in 10 modes, as well as numerous combination frequencies. Our discussion focuses on a new asteroseismological analysis of GD358, incorporating the 2006 data set and drawing on 24 years of archival observations. Our results reveal that, while the general frequency locations of the identified modes are consistent throughout the years, the multiplet structure is complex and cannot be interpreted simply as l = 1 modes in the limit of slow rotation. The high-k multiplets exhibit significant variability in structure, amplitude and frequency. Any identification of the m components for the high-k multiplets is highly suspect. The k = 9 and 8 modes typically do show triplet structure more consistent with theoretical expectations. The frequencies and amplitudes exhibit some variability, but much less than the high-k modes. Analysis of the k = 9 and 8 multiplet splittings from 1990 to 2008 reveal a long-term change in multiplet splittings coinciding with the 1996 sforzando event, where GD358 dramatically altered its pulsation characteristics on a timescale of hours. We explore potential implications, including the possible connections between convection and/or magnetic fields and pulsations. We suggest future investigations, including theoretical investigations of the relationship between magnetic fields, pulsation, growth rates, and convection.
14082825
350 μm Observations of Local Luminous Infrared Galaxies and the Temperature Dependence of the Emissivity Index
We report 350 μm observations of 18 nearby luminous infrared galaxies (LIRGs) using the Submillimeter High Angular Resolution Camera II (SHARC-II) mounted on the Caltech Submillimeter Observatory (CSO) 10.4 m telescope. Combining our 350 μm flux measurements with the existing far-infrared (FIR) and submillimeter data, we fit a single-temperature model to the spectral energy distributions (SEDs) and find the dust temperatures, emissivity indices, and FIR luminosities having sample medians of T_d = 39.4 ± 7.9 K, β = 1.6 ± 0.3, and LFIR = 10^(11.2±0.6) L⊙. An empirical inverse T_d-β correlation, best described by T_d = (9.86 × 10^9)^(1/(4.63 + β)), is established for the local LIRG sample, which we argue can be explained by the intrinsic interdependence between the dust temperature and grain emissivity index as physical parameters, as well as variations in grain properties in the interstellar medium (ISM).