8,286 research outputs found

    Rare decay Bβ†’Xsl+lβˆ’B\to X_sl^+l^- in a CP spontaneously broken two Higgs doublet model

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    The Higgs boson mass spectrum and couplings of neutral Higgs bosons to fermions are worked out i n a CP spontaneously broken two Higgs doublet model in the large tanΞ²\beta case. The differential branching ratio, forward-backward asymmetry, CP asymmetry and lepton polarization for Bβ†’Xsl+lβˆ’B\to X_s l^+ l^- are computed. It is shown that effects of neutral Higgs bosons are quite significant when tan⁑β\tan\beta is large. Especially, the CP violating normal polarization PNP_N can be as large as several percents.Comment: 27 pages, text updated, new numerical results include

    Empirical metallicity-dependent calibrations of effective temperature against colours for dwarfs and giants based on interferometric data

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    We present empirical metallicity-dependent calibrations of effective temperature against colours for dwarfs of luminosity classes IV and V and for giants of luminosity classes II and III, based on a collection from the literature of about two hundred nearby stars with direct effective temperature measurements of better than 2.5 per cent. The calibrations are valid for an effective temperature range 3,100 - 10,000 K for dwarfs of spectral types M5 to A0 and 3,100 - 5,700 K for giants of spectral types K5 to G5. A total of twenty-one colours for dwarfs and eighteen colours for giants of bands of four photometric systems, i.e. the Johnson (UBVRJIJJHKUBVR_{\rm J}I_{\rm J}JHK), the Cousins (RCICR_{\rm C}I_{\rm C}), the Sloan Digital Sky Survey (SDSS, grgr) and the Two Micron All Sky Survey (2MASS, JHKsJHK_{\rm s}), have been calibrated. Restricted by the metallicity range of the current sample, the calibrations are mainly applicable for disk stars ([Fe/H]β€‰β‰³β€‰βˆ’1.0\,\gtrsim\,-1.0). The normalized percentage residuals of the calibrations are typically 2.0 and 1.5 per cent for dwarfs and giants, respectively. Some systematic discrepancies at various levels are found between the current scales and those available in the literature (e.g. those based on the infrared flux method IRFM or spectroscopy). Based on the current calibrations, we have re-determined the colours of the Sun. We have also investigated the systematic errors in effective temperatures yielded by the current on-going large scale low- to intermediate-resolution stellar spectroscopic surveys. We show that the calibration of colour (gβˆ’Ksg-K_{\rm s}) presented in the current work provides an invaluable tool for the estimation of stellar effective temperature for those on-going or upcoming surveys.Comment: 28 pages, 19 figures, 8 tables, accepted for publication in MNRA
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