Charged Higgs bosons and decays of heavy flavored mesons

We explore the possibility that charged Higgs bosons exist. The role of e⁺e^? experiments carried out above heavy quark thresholds is stressed. Striking experimental signatures are predicted.     

Comments on radiative decays of scalar mesons

A previously proposed analysis of radiative decays of 0⁺⁺ mesons is reexamined. New estimates are given for the widths of χ → γγ and ψ → χγ.     

D decays into pseudoscalar and scalar mesons

Zeitschrift für Physik C Particles and Fields - In this paper, we study the pseudoscalar-scalar meson (PS) weak decays ofD-mesons in the non-relativistic quark model using factorization...     

Vector-meson-dominance model for radiative decays involving light scalar mesons

We study a vector-dominance model which predicts quite a large number of currently interesting decay amplitudes of the types S-->gammagamma, V-->Sgamma, and S-->Vgamma, where S and V denote scalar and vector mesons, in terms of three parameters. As an application, the model makes it easy to study in detail a recent proposal to boost the ratio Gamma(phi-->f(0)gamma)/Gamma(phi-->a(0)(0)gamma) by including the isospin violating a(0)(0)-f(0) mixing. However, we find that this effect is actually small in our model.     

Inclusive production of neutral vector mesons in hadronic Z decays

A data sample of about 3.0 million hadronicZ decays collected by the ALEPH experiment at LEP in the years 1991 through 1994 is used to make an inclusive selection of B hadron events. In this event sample 4227±140±252B* mesons in the decayB*→Bγ and 1944±108±161B** _u,d mesons decaying into a B meson and a charged pion are reconstructed. Here and in the followingB** _u,d denotes the eightL=1(bū) and (bd) states and their charge conjugate. For the well establishedB* meson the following quantities are obtained:ΔM=M _B*−M_B=(45.30±0.35±0.87) MeV/c² andN _B*/(N _B+N _B*)=(77.1±2.6±7.0)%. The angular distribution of the photons in theB* rest frame is used to measure the relative contribution of longitudinalB* polarization states to beσ _L/(σ _L+σ _T)=(33±6±5)%.     

Doubly-charged scalar bosons from the doublet

We consider the extended Higgs models, in which one of the isospin doublet scalar fields carries the hypercharge Y=3/2. Such a doublet field Φ3/2 is composed of a doubly charged scalar boson as well as a singly charged one. We first discuss a simple model with Φ3/2 (Model I), and study its collider phenomenology at the LHC. We then consider a new model for radiatively generating neutrino masses with a dark matter candidate (Model II), in which Φ3/2 and an extra Y=1/2 doublet as well as vector-like singlet fermions carry the odd quantum number for an unbroken discrete Z₂ symmetry. We also discuss the neutrino mass model (Model III), in which the exact Z₂ parity in Model II is softly broken. It is found that the doubly charged scalar bosons in these models show different phenomenological aspects from those which appear in models with a Y=2 isospin singlet field or a Y=1 triplet one. They could be clearly distinguished at the LHC.     

Radiative decays with light scalar mesons and singlet–octet mixing in ChPT

We study different types of radiative decays involving f₀(980) and a₀(980) mesons within a unified ChPT-based approach at one-loop level. Light scalar resonances, which are seen in the ππ, πη and KK̄ channels of the φ(1020) radiative decays and in the J/ψ decays are responsible for key questions of low-energy dynamics in the strong interaction sector, and the decays φ(1020)→γa₀(980), φ(1020)→γf₀(980), a₀(980)→γγ and f₀(980)→γγ are of interest for current experimental programs in Jülich, Frascati and Novosibirsk. From the theoretical point of view it is important to verify whether light scalar mesons are members of some flavor octet or nonet. We find a value for the mixing angle dictated by consistency with experiment and the coupling structures of the ChPT Lagrangian. The decay widths f₀(980)/a₀(980)→γρ(770)/ω(782), which have not been experimentally studied yet, are predicted. We also obtain several relations between the widths, which hold independently of the coupling constants and which represent a fingerprint of the model. PACS 11.30.Hv; 12.39.Fe; 13.30.Eg; 14.40.-n     

Model of scalar mesons

A model containing a nonet of scalar mesonsS, a nonet of pseudoscalar mesonsP, and a nonet of baryons is constructed where the mesons enter in the form of the matrixM=e^i(S+iP), Several Lagrangians are introduced such that the mesons get their physical masses, and the decay widths of the scalar mesons are calculated. The model satisfies generalized PCAC. It is found that the coupling constants of the mesonsε(700) andε′(1060) to pions and nucleons satisfy the relations: $$\frac{{|G_{\varepsilon NN} |}}{{|G_{\varepsilon \pi \pi } |}} = 1 \cdot 4,\frac{{|G_{\varepsilon 'NN} |}}{{|G_{\varepsilon '\pi \pi } |}} = 0 \cdot 89,\frac{{|G_{\varepsilon \pi \pi } G_{\varepsilon NN} |}}{{4\pi }} = 4 \cdot 9,{\text{and}}\frac{{|G_{\varepsilon '\pi \pi } G_{\varepsilon 'NN} |}}{{4\pi }} = 0 \cdot 34.$$      

Electromagnetic decays of light mesons

The new data on the electromagnetic decays of “light” mesons are analyzed. Special attention is paid to rare electromagnetic leptonic decays of the type $\text{A}\text{→}\text{B}\text{l}{}^{\mathrm{+}}\text{l}{}^{\mathrm{?}}$ and to ways of using these processes for extracting information on the transition form factors of neutral mesons. Data on electromagnetic lepton processes of higher order, such as $\text{P}\text{→}\text{l}{}^{\mathrm{+}}\text{l}{}^{\mathrm{?}}$ and $\text{P}\text{′ →}\text{P}\text{l}{}^{\mathrm{+}}\text{l}{}^{\mathrm{?}}$, are also analyzed and we discuss present prospects for such investigations.     

Measurement of light scalar mesons in many-body decays in the PHENIX experiment at the Relativistic Heavy-Ion Collider

The unique design of the PHENIX detector at the Relativistic Heavy-Ion Collider allows one to detect neutral and charged particles produced in high-energy collisions of heavy ions. This circumstance made it possible to measure many-particle decays of light mesons, such as K _S ⁰ →π⁰π⁰, η→π⁰π^?π⁺, and η→γγ in p + p, d + Au and Au + Au collisions at the energy \(\sqrt {S_{NN} }\) = 200 GeV. The latest results of measuring the differential production cross sections, ratios of particle yields (K _S ⁰ /π⁰ and η/π⁰), and the nuclear modification factors (\(R_{dA}^{K_S }\), R _dA ^η , R _AA ^η ) in a wide range of transverse momenta (from 2 to 12 GeV s^?1) are reported.     

Preliminary estimate of branching ratios of weak hadronic decays of bottom baryons emitting charmless scalar mesons

In this paper we study one-dimensional static self-dual non-topological solitons in an Abelian-Higgs Chern–Simons model with a non-canonical kinetic term. We choose a scalar potential with a single minimum and present an analytical soliton solution which corresponds to an electrically charged lump-like soliton without total momentum and located in a region where the scalar field gets maximum. The solitonic boundary conditions impose a discontinuity on the electric field across the soliton line where, then, there is a linear charge density.     

Two-body nonleptonic decays ofD mesons

The amplitudes for two-body Cabibbo allowed nonleptonic decays ofD mesons are evaluated within the factorization approximation from the effective Hamiltonian including short distance QCD corrections to next-to-leading order. Annihilation andW-exchange contributions as well as final state interaction effects have been included and are in fact crucial to obtain agreement with the experimental data.     

Confinement singularities in two-pion decays of mesons

We consider as an example the two-pion decay of the ρ meson, the ³ S ₁ q $ \bar q $ \bar q state of the constituent quarks—the decay being determined by the transition q $ \bar q $ \bar q → ππ contains information about confinement interactions. One can specify in this decay two types of transitions: (i) the bremsstrahlung radiation of a pion q → q + π (or $ \bar q $ \bar q → $ \bar q $ \bar q + π) with a subsequent fusion q $ \bar q $ \bar q → π, and (ii) the direct transition q $ \bar q $ \bar q → ππ. We demonstrate how in the amplitudes of the corresponding transitions the quark singularities have to disappear, i.e., what is the way the quark confinement at relatively short distances can be realized. We calculate and estimate the contributions of processes with bremsstrahlung radiation of the pion and of the direct transition q $ \bar q $ \bar q → ππ. The estimates demonstrate that the processes involving the direct transition q $ \bar q $ \bar q → ππ are necessary, but they cannot be determined unambiguously by the decay ρ(775) → ππ. We conclude that for the determination of the q $ \bar q $ \bar q → ππ transition more complete data on the resonance decays into the ππ channels are needed than those available at the moment.