Search

We study the production of the light J P C = 1 − + hybrid isoscalars η 1 ′ (1855) and the yet undiscovered η 1 (1660) as intermediate states in the radiative decays of the charmonium (J / ψ) to two conventional mesons using a flavor symmetric Lagrangian. For this purpose, we use the J / ψ → γ η 1 ′ (1855) → γ η η ′ process as the reference. We find that some of the decay channels have branching ratios similar to or larger than that of the γ η η ′ channel and are sensitive to the mixing between the hybrid isoscalars. We propose that relatively stable γ η f 1 (1285) channel be explored for the presence of the light hybrid isoscalar η 1 h y b (1660). We also exploit the strong decay channels containing at least one vector meson to study the radiative decays of the whole hybrid nonet { π 1 (1600) , K 1 h y b (1750) , η 1 h y b (1660) , η 1 ′ (1855) }. We find that the hybrids cannot radiatively decay into the I = 0 pseudoscalars. Furthermore, the vector decay channels ((ρ / ω / ϕ) γ) of the hybrid isoscalars are sensitive to the strangeness content of the hybrids. We also provide estimates for the branching fractions for the radiative production and partial widths for the radiative decays of the hybrids. [ABSTRACT FROM AUTHOR]

The transition form factors responsible for the radiative Σ Q → Λ Q γ and Ξ Q ′ → Ξ Q γ decays of the negative parity baryons are examined within light cone QCD sum rules. The decay widths of the radiative transitions are calculated using the obtained results of the form factors. A comparison of our predictions on decay widths with the corresponding widths of positive parity baryons is given. [ABSTRACT FROM AUTHOR]

Using the inclusive photon spectrum based on a data sample collected at the J / ψ peak with the KEDR detector at the VEPP-4M e + e − collider, we measured the rate of the radiative decay J / ψ → γ η c as well as η c mass and width. Taking into account an asymmetric photon lineshape we obtained Γ γ η c 0 = 2.98 ± 0.18 − 0.33 + 0.15 keV , M η c = 2983.5 ± 1.4 − 3.6 + 1.6 MeV / c 2 , Γ η c = 27.2 ± 3.1 − 2.6 + 5.4 MeV . [ABSTRACT FROM AUTHOR]

Through-space charge-transfer (TSCT) emitters with high radiative decay rates are very important for their use in electroluminescent devices but have rarely been reported. Here, three TSCT emitters 1 – 3 with high radiative decay rates of over 107 s−1 are developed by using 4-methyl-9 H -xanthene (MeXT) as the rigid linker, 10-phenyldihydroacridine (PhDMAC) as the donor, and 2,4,6-triphenyltriazine (1), 2,4,6-triphenylpyrimidine (2) and 2,4-di- tert -butyl-6-phenyl-1,3,5-triazine (3) as the acceptors. Single-crystal structures and theoretical calculations reveal that the donor fixed by the spiro-structure in MeXT and the acceptor located nearby the donor are arranged into a very close, cofacial packing with strong through-space electronic interactions, which promotes TSCT and the radiative decay of charge-transfer state. In degassed toluene solution, 1 – 3 show blue emission centered at 479, 458 and 455 nm, respectively, and afford high radiative decay rates (k r,s) of up to 1.6 × 107 s−1, which are the highest for TSCT emitters reported so far. In the doped films, 1 – 3 show high k r,s values of up to 1.3 × 107 s−1 and high photoluminescent efficiencies (Φ PL) of up to 0.95. Organic light-emitting diodes using 1 – 3 as the emitters afford blue emission with high external quantum efficiencies of up to 22.6%. The work reveals that TSCT emitters with similar emission characteristics (high Φ PL and high k r,s) to through-bond charge-transfer emitters are achievable by arranging the donor and acceptor units into a very close, cofacial packing. • Through-space charge-transfer emitters were developed with a xanthene linker. • Very close, cofacial donor/acceptor packing was formed within the emitter. • High radiative decay rates up to 1.6 × 107 s−1 were achieved. • Organic light-emitting diodes using the emitters showed high EQE s of up to 22.6%. [ABSTRACT FROM AUTHOR]

Abstract: Recent results and future prospects of particle physics experiments with neutral and charged -meson (kaon) decays are reviewed. Topics include CP violation, rare decays, leptons in kaon decays, tests of CPT and quantum mechanics, radiative decays, hadrons in kaon decays, basic observables, and CKM unitarity, and exotic searches. Experimental techniques developed for the kaon decay experiments are discussed. [Copyright &y& Elsevier]

Abstract: Using an improved “analytic K-matrix model”, we reconsider the extraction of the and γγ widths from scatterings data of Crystal Ball and Belle. Our main results are summarized in Tables 3 and 4. The averaged σ “direct width” to γγ is 0.16(3) keV which confirms a previous result of Mennessier et al. (2007, 2008) and which does neither favour a large four-quark/molecule nor a pure components. The “direct width” of the of 0.28(2) keV is much larger than the four-quark expectation but can be compatible with a or a gluonium component. We also found that the rescattering part of each amplitude is relatively large indicating an important contribution of the meson loops in the determinations of the σ and γγ total widths. This is mainly due to the large couplings of the σ and to ππ and/or , which can also be due to a light scalar gluonium with large OZI violating couplings but not necessary to a four-quark or molecule state. Our average results for the total (direct + rescattering) γγ widths: , are comparable with the ones from dispersion relations and PDG values. Using the parameters from QCD spectral sum rules, we complete our analysis by showing that the production rates of unmixed scalar gluonia and agree with the data from , ϕ radiative and semi-leptonic decays. [ABSTRACT FROM AUTHOR]

Abstract: Within the framework of a nonlinear chiral Lagrangian we explore the nontrivial nature of and in terms of quarkonium, tetraquark and gluonium components. The mass constraints are obtained and the strong and radiative partial widths are calculated to demonstrate and discriminate these components. The static properties of and glueball are also studied. Our results are confronted with the experimental and theoretical data available as well as the upcoming measurements. [ABSTRACT FROM AUTHOR]

Abstract: We evaluate the radiative decay into a vector, a pseudoscalar and a photon of several resonances dynamically generated from the vector–vector interaction. The process proceeds via the decay of one of the vector components into a pseudoscalar and a photon, which have an invariant mass distribution very different from phase space as a consequence of the two vector structure of the resonances. Experimental work along these lines should provide useful information on the nature of these resonances. [Copyright &y& Elsevier]

Abstract: The decays of a light scalar meson into a vector meson and a photon are evaluated in the tetraquark and quarkonium assignments of the scalar states. A link with the radiative decays is established: experimental results for will make it possible to decide if the direct, quark-loop contribution to or the kaon-loop contribution is dominant. Also strong decays – where P denotes a pseudoscalar meson – are investigated: within our scheme, the tetraquark assignment works better than the quarkonium one. [Copyright &y& Elsevier]

The quark-level linear σ model (LσM) is employed to compute a variety of electromagnetic and weak observables of light mesons, including pion and kaon form factors and charge radii, charged-pion polarizabilities, semileptonic weak Kℓ3 decays, semileptonic weak radiative pion and kaon form factors, radiative decays of vector mesons, and nonleptonic weak K2π decay. The agreement of all these predicted observables with experiment is striking. In passing, the tight link between the LσM and vector-meson dominance is shown. [Copyright &y& Elsevier]

Radiative magnetic dipole decays of heavy–light vector mesons into pseudoscalar mesons V→Pγ are considered within the relativistic quark model. The light quark is treated completely relativistically, while for the heavy quark the 1/mQ expansion is used. It is found that relativistic effects result in a significant reduction of decay rates. Comparison with previous predictions and recent experimental data is presented. [Copyright &y& Elsevier]

Abstract: The hierarchy among the radiative decay channels for the looks quite different from the one. The fate of charm, namely an ultimate survival of on-shell intermediate states, might give us the clue for this new puzzle in exclusive charmonium decays. A similar self-preservation has already been invoked in the past to solve the so-called ρπ puzzle. [Copyright &y& Elsevier]

We examine the dielectron invariant mass spectrum and the variation of the polarization asymmetry as a function of that mass in the event generator of the five-dimensional Bethe–Heitler differential cross section of the conversion of linearly polarized photons that we have implemented recently as a Geant4 Physics Model. We compare the results obtained with simulated samples to analytical expressions. Studies of b → s γ decays at LHC and Belle II experiments could provide hints of physics beyond the standard model in flavor-changing neutral current processes; issues have been reported in the simulation of the properties of the background induced by genuine γ -ray conversions in their detectors. Our results demonstrate that using the five-dimensional model would help solve these issues. [ABSTRACT FROM AUTHOR]

An enhanced phenomenological model that includes isospin-symmetry breaking is presented in this letter. The model is then used in a number of statistical fits to the most recent experimental data for the radiative transitions VPγ (V = ρ , K ⁎ , ω , ϕ and P = π , K , η , η ′) and estimations for the mixing angles amongst the three pseudoscalar states with vanishing third-component of isospin are obtained. The quality of the performed fits is good, e.g. χ min 2 / d.o.f = 1.9. The current experimental uncertainties allow for isospin-symmetry violations with a confidence level of approximately 2.5 σ. [ABSTRACT FROM AUTHOR]

A pion mean-field approach allows one to investigate light and singly heavy baryons on an equal footing. In the large N c limit, the light and singly heavy baryons are viewed respectively as N c and N c − 1 valence quarks bound by the pion mean fields created self-consistently, since a heavy quark can be regarded as a static color source in the limit of the infinitely heavy quark mass. The transition magnetic moments of the baryon sextet are determined entirely by using the parameters fixed in the light-baryon sector without any additional parameters introduced. Assuming that the transition E 2 moments are small, we are able to compute the radiative decay rates of the baryon sextet. The numerical results are discussed, being compared with those from other approaches. [ABSTRACT FROM AUTHOR]

Abstract: - mixing is expected to be small in the Standard Model. Several recent studies have shown evidence for this phenomenon. However, there has been no evidence for CP-violation, either in - mixing or direct D decays. We present evidence for - mixing and improved limits on CP asymmetries from the BaBaR experiment. We also present new branching fraction measurements of radiative decays and compare these measurements with theoretical predictions. [Copyright &y& Elsevier]