Determination of f+K(0) and extraction of |Vcs| from semileptonic D decays

By globally analyzing all existing measured branching fractions and partial rates in different four momentum transfer-squared q2 bins of D→Ke+νe decays, we obtain the product of the form factor and magnitude of Cabibbo–Kobayashi–Maskawa matrix element Vcs to be f+K(0)|Vcs|=0.717±0.004 . With this product, we determine the D→K semileptonic form factor f+K(0)=0.737±0.004±0.000 in conjunction with the value of |Vcs| determined from the standard model global fit. Alternately, with the product together with the input of the form factor f+K(0) calculated in lattice quantum chromodynamics (LQCD) recently, we extract |Vcs|D→Ke+νe=0.962±0.005±0.014 , where the error is still dominated by the uncertainty of the form factor calculated in LQCD. Combining the |Vcs|Ds+→ℓ+νℓ=1.012±0.015±0.009 extracted from all existing measurements of Ds+→ℓ+νℓ decays and |Vcs|D→Ke+νe=0.962±0.005±0.014 together, we find the most precisely determined |Vcs| to be |Vcs|=0.983±0.011 , which improves the accuracy of the PDG’2014 value |Vcs|PDG′2014=0.986±0.016 by 45%

Observation of Electromagnetic Dalitz decays J/ψ\to P e^+e^-

Based on a sample of (225.3\pm2.8)\times 10^{6} J/\psi events collected with the BESIII detector, the electromagnetic Dalitz decays of J/\psi \to P e^+e^-(P=\eta'/\eta/\pi^0) are studied. By reconstructing the pseudoscalar mesons in various decay modes, the decays J/\psi \to \eta' e^+e^-, J/\psi \to \eta e^+e^- and J/\psi \to \pi^0 e^+e^- are observed for the first time. The branching fractions are determined to be \mathcal{B}(J/\psi\to \eta' e^+e^-) = (5.81\pm0.16\pm0.31)\times10^{-5}, \mathcal{B}(J/\psi\to \eta e^+e^-) = (1.16\pm0.07\pm0.06)\times10^{-5}, and \mathcal{B}(J/\psi\to \pi^0 e^+e^-)=(7.56\pm1.32\pm0.50)\times10^{-7}, where the first errors are statistical and the second ones systematic

Constraining absolute neutrino masses via detection of galactic supernova neutrinos at JUNO

A high-statistics measurement of the neutrinos from a galactic core-collapse supernova is extremely important for understanding the explosion mechanism, and studying the intrinsic properties of neutrinos themselves. In this paper, we explore the possibility to constrain the absolute scale of neutrino masses mν via the detection of galactic supernova neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO) with a 20 kiloton liquid-scintillator detector. In assumption of a nearly-degenerate neutrino mass spectrum and a normal mass ordering, the upper bound on the absolute neutrino mass is found to be mν < (0.83 ± 0.24) eV at the 95% confidence level for a typical galactic supernova at a distance of 10 kpc, where the mean value and standard deviation are shown to account for statistical fluctuations. For comparison, we find that the bound in the Super-Kamiokande experiment is mν < (0.94 ± 0.28) eV at the same confidence level. However, the upper bound will be relaxed when the model parameters characterizing the time structure of supernova neutrino fluxes are not exactly known, and when the neutrino mass ordering is inverted

A Grassmann path from AdS 3 to flat space

We show that interpreting the inverse AdS 3 radius 1 /l as a Grassmann variable results in a formal map from gravity in AdS 3 to gravity in flat space. The underlying reason for this is the fact that ISO(2 , 1) is the Inonu-Wigner contraction of SO(2 , 2). We show how this works for the Chern-Simons actions, demonstrate how the general (Banados) solution in AdS 3 maps to the general flat space solution, and how the Killing vectors, charges and the Virasoro algebra in the Brown-Henneaux case map to the corresponding quantities in the BMS 3 case. Our results straightforwardly generalize to the higher spin case: the recently constructed flat space higher spin theories emerge automatically in this approach from their AdS counterparts. We conclude with a discussion of singularity resolution in the BMS gauge as an application

Desingularization of the Milne Universe

Resolution of cosmological singularities is an important problem in any full theory of quantum gravity. The Milne orbifold is a cosmology with a big-bang/big-crunch singularity, but being a quotient of flat space it holds potential for resolution in string theory. It is known, however, that some perturbative string amplitudes diverge in the Milne geometry. Here we show that flat space higher spin theories can effect a simple resolution of the Milne singularity when one embeds the latter in <math altimg="si1.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mn>2</mn><mo>+</mo><mn>1</mn></math> dimensions. We explain how to reconcile this with the expectation that non-perturbative string effects are required for resolving Milne. Along the way, we introduce a Grassmann realization of the İnönü–Wigner contraction to export much of the AdS technology to our flat space computation

Constraining anisotropy of the universe from different groups of type-Ia supernovae

Recently released Planck data and other astronomical observations show that the universe may be anisotropic on large scales. Inspired by this, anisotropic cosmological models have been proposed. We note that the Finsler–Randers spacetime provides an appropriate framework for the anisotropic cosmology. By adding an arbitrary 1-form to the Friedmann–Robertson–Walker line element, a privileged axis in the universe is picked out. The distance–redshift relation is modified to be direction-dependent. We wish that the anisotropic cosmological model may be tested crossly by independent observations. Type-Ia supernovae (SNe Ia) calibrated from four different light curve fitters are used to constrain the possible anisotropy of the universe. The magnitudes of anisotropy are all between 2–5 %, but the systematic uncertainty cannot be excluded. The directions of the privileged axis seem to differ from each other. The statistical significance is not high enough to make a convincing conclusion. Nevertheless, the <math><mrow><mn>1</mn><mi mathvariant="italic">σ</mi></mrow></math> contours in the <math><mrow><mo stretchy="false">(</mo><mi>l</mi><mo>,</mo><mi>b</mi><mo stretchy="false">)</mo></mrow></math> plane obtained from four groups of SNe Ia have an overlap, centering at <math><mrow><mrow><mo stretchy="false">(</mo><mi>l</mi><mo>,</mo><mi>b</mi><mo stretchy="false">)</mo></mrow><mo>≈</mo><mrow><mo stretchy="false">(</mo><msup><mn>170</mn><mo>∘</mo></msup><mo>,</mo><msup><mn>0</mn><mo>∘</mo></msup><mo stretchy="false">)</mo></mrow></mrow></math> . Monte Carlo simulation shows that the anisotropy is unlikely to be caused by the selection effect

Improvements to the Froissart bound from AdS/CFT

In this paper we consider the issue of the Froissart bound on the high energy behaviour of total cross sections. This bound, originally derived using principles of analyticity of scattering amplitudes, is seen to be satisfied by all the available experimental data on total hadronic cross sections. At strong coupling, gauge/gravity duality has been used to provide some insights into this behaviour. In this work, we find the subleading terms to the so-derived Froissart bound from AdS/CFT. We find that a (ln⁡ss0) term is obtained, with a negative coefficient. We see that the fits to the currently available data confirm improvement in the fits due to the inclusion of such a term, with the appropriate sign

Charge and color breaking constraints in MSSM after the Higgs discovery at LHC

We revisit the constraints on the parameter space of the Minimal Supersymmetric Standard Model (MSSM), from charge and color breaking minima in the light of information on the Higgs from the LHC so far. We study the behavior of the scalar potential keeping two light sfermion fields along with the Higgs in the pMSSM framework and analyze the stability of the vacuum. We find that for lightest stops ≲ 1 TeV and small μ ≲ 500 GeV, the absolute stability of the potential can be attained only for $\left| {{X_t}} \right|\lesssim \sqrt{{6{m_{{\widetilde{t}1}}}{m_{{\widetilde{t}2}}}}}$ . The bounds become stronger for larger values of the μ parameter. Note that this is approximately the value of X t which maximizes the Higgs mass. Our bounds on the low scale MSSM parameters are more stringent than those reported earlier in literature. We reanalyze the stau sector as well, keeping both staus. We study the connections between the observed Higgs rates and vacuum (meta)stability. We show how a precision study of the ratio of signal strengths, ( μ γγ /μ ZZ ) can shed further light

A note on D1-D5 entropy and geometric quantization

We quantize the space of 2-charge fuzzballs in IIB supergravity on K 3. The resulting entropy precisely matches the D1-D5 black hole entropy, including a specific numerical coefficient. A partial match (ie., a smaller coefficient) was found by Rychkov a decade ago using the Lunin-Mathur subclass of solutions — we use a simple observation to generalize his approach to the full moduli space of K 3 fuzzballs, filling a small gap in the literature

How to interpret a discovery or null result of the 0ν2β decay

The Majorana nature of massive neutrinos will be crucially probed in the next-generation experiments of the neutrinoless double-beta ( 0ν2β ) decay. The effective mass term of this process, ⟨m⟩ee , may be contaminated by new physics. So how to interpret a discovery or null result of the 0ν2β decay in the foreseeable future is highly nontrivial. In this paper we introduce a novel three-dimensional description of |⟨m⟩ee| , which allows us to see its sensitivity to the lightest neutrino mass and two Majorana phases in a transparent way. We take a look at to what extent the free parameters of |⟨m⟩ee| can be well constrained provided a signal of the 0ν2β decay is observed someday. To fully explore lepton number violation, all the six effective Majorana mass terms ⟨m⟩αβ (for α,β=e,μ,τ ) are calculated and their lower bounds are illustrated with the two-dimensional contour figures. The effect of possible new physics on the 0ν2β decay is also discussed in a model-independent way. We find that the result of |⟨m⟩ee| in the normal (or inverted) neutrino mass ordering case modified by the new physics effect may somewhat mimic that in the inverted (or normal) mass ordering case in the standard three-flavor scheme. Hence a proper interpretation of a discovery or null result of the 0ν2β decay may demand extra information from some other measurements