Narrow Results

Using the calculated values of the strong coupling constants of the heavy sextet spin-3/2 baryons to sextet and antitriplet heavy spin-1/2 baryons with light vector mesons within the light cone QCD sum rules method, and vector meson dominance assumption, the radiative decay widths are calculated. These widths are compared with the "direct" radiative decay widths predicted in the framework of the light cone QCD sum rules.

In this paper, we perform an systematic study of the radiative transitions among the bottomonium states using the heavy quarkonium effective Lagrangians, and make predictions for the ratios among the radiative decay widths of a special multiplet to another multiplet. The predictions can be confronted with the experimental data in the future.

The 2S$B_c$ states observed by ATLAS, CMS and LHCb Collaborations are discussed. The observation perspectives of $B_c^{\ast }$, 2P wave, 3P wave and D wave states of $B_c$ at LHC experiments are estimated.

The mass spectrum of $b\bar{b}$ states has been obtained using the phenomenological relativistic quark model (RQM). The Hamiltonian used in the investigation has confinement potential and confined one gluon exchange potential (COGEP). In the framework of RQM a study of $M1$ and $E1$ radiative decays of $b\bar{b}$ states has been made. An overall agreement is obtained with the experimental masses and decay widths. The possibility that some of the excited $s$ wave $b\bar{b}$ states being exotic states is explored.

Recent BaBar results on rare B decays involving flavor changing neutral currents are presented. New measurements of the CP asymmetries in b→sγ and B→K*γ decays are reported as well as B→K(*)l⁺l^- and b→sl⁺l^- branching ratio measurements. The data sample comprises decays collected with the BaBar detector at the PEP-II e⁺e^- storage ring.

We present the magnetic dipole(M1) transitions V → Pγ of various heavy-flavored mesons such as and using the light-front quark model constrained by the variational principle for the QCD-motivated effective Hamiltonian. Our numerical results for the radiative decay widths are in good agreement with the available experimental data as well as other theoretical model calculations.

In the little Higgs model with T-parity (LHTM), the only tree-level kinematically allowed two-body decay of the Z_H boson can be the Z_H→A_HH decay and thus one-loop induced two-body decays may have a significant rate. We study the Z_H→γA_H decay, which is induced at the one-loop level by a fermion triangle and is interesting as it depends on the mechanism of anomaly cancelation of the model. All the relevant two- and three-body decays of the Z_H gauge boson arising at the tree-level are also calculated. We considered a small region of the parameter space where f is still allowed to be as low as 500 GeV by electroweak precision data. We analyzed the scenario of a Higgs with a mass of 120 GeV. We found that the Z_H→γA_H branching ratio can be of the order of a tree-level three-body decay and may be at the reach of detection at the LHC for f close to 500 GeV, but it may be difficult to detect for f = 1 TeV. There is also an scenario where the Higgs boson has an intermediate mass such that the Z_H→A_HH decay is closed, the Z_H→γA_H gets considerably enhanced and the chances of detection get a large boost.

We determine the value of the ω-ρ-π mesons coupling (g_ωρπ), in the context of the vector meson dominance model, from radiative decays, the ω→3π decay width and the e⁺e^-→3π cross-section. For the last two observables we consider the effect of either a heavier resonance (ρ′(1450)) or a contact term. A weighted average of the results from the set of observables yields g_ωρπ = 14.7±0.1 GeV^-1 in absence of those contributions, and g_ωρπ = 11.9 ± 0.2 GeV^-1 or g_ωρπ = 11.7 ± 0.1 GeV^-1 when including the ρ′ or contact term, respectively. The inclusion of these additional terms makes the estimates from the different observables to lay in a more reduced range. Improved measurements of these observables and the ρ′(1450) meson parameters are needed to give a definite answer on the pertinence of the inclusion of this last one in the considered processes.

The first radial excitations of axial-vector mesons are considered in the framework of the extended U(3) × U(3) Nambu–Jona-Lasinio model. We calculate the mass spectrum of a₁, f₁ and also strange axial-vector mesons. For description of radially excited states, we used the form factors of polynomial type of the second order in transverse quark momentum. For the ground- and excited-state mesons consisting of light quarks we have calculated the widths of a number of strong and radiative decays. We got satisfactory agreement with experimental data for the ground states. A set of predictions for the excited states of mesons is given.

We investigate $B_s^0\to {\ell }^{+}{\ell }^{-}\gamma$ decays in a nonuniversal $Z^{\prime }$ model derived from the extension of the Standard Model (SM). Considering the $Z^{\prime }$-mediated flavor-changing neutral current (FCNC) effects, we calculate the branching ratio and forward–backward asymmetry $(A_{\mathrm{\text{FB}}})$ for $B_s^0\to {\ell }^{+}{\ell }^{-}\gamma$ decay processes. We compare the obtained results with predictions of the SM and discuss the sensitivity of the observables to $Z^{\prime }$ boson coupling parameters. We find that the branching ratios are enhanced by one order from SM predictions in $Z^{\prime }$ model scenario. We also observe that the variation of forward–backward asymmetry with the $Z^{\prime }$ boson coupling parameters portrays discrimination between NP effects and SM results.

In this work, we tried to predict the parameters of $B_c^{\ast }$ meson. Simple assumptions gave us the following parameters $m_{B_c^{\ast }}=6329\pm 10$MeV and $f_{B_c^{\ast }}=535.5\pm 57.8$MeV (for ${\mathrm{\Lambda }}_{B_c^{\ast }}=2.26\pm 0.14$GeV in covariant confined quark model). We calculated widths of radiative decays of $B_q^{\ast }$ mesons, where $q=u∕d,s,c$ and compared them with other theoretical works. It was shown that the width of the $B_c^{\ast }$ meson is very sensitive to the mass $m_{B_c^{\ast }}$ as expected and less to the size parameter ${\mathrm{\Lambda }}_{B_c^{\ast }}$.

This paper describes the search for di-photon decays of an Axion-like particle (ALP) in radiative decays of $J/\psi$ using 2.7 billion $\psi (2S)$ events collected by the BESIII detector. A $J/\psi$ data sample is selected by tagging the pion-pair from $\psi (2S)\to {\pi }^{+}{\pi }^{-}J/\psi$ transition. No evidence of ALP production is found, and $95\%$ confidence upper limits on ALP photon coupling are set to be in the mass range of [0.165, 2.84] GeV/${\mathrm{\text{c}}}^2$. The new BESIII limits are more stringent than the existing experimental constraints.

In this work, the spectra and decay properties of $B_c$ mesons $(c\overline{b}$) have been investigated using a nonrelativistic potential model incorporating corrections from LQCD. The nonrelativistic Schrödinger wave equation is solved numerically using the Matrix Numerov Method. Using the obtained masses and wave functions, decay widths, lifetime, branching ratios and radiative decay widths are computed for the $c\overline{b}$ system. Influence of the bound state effect on decay width of $B_c$ mesons is also analyzed. We compare the obtained results with the experimental data and with other theoretical models.

We have employed the framework of Bethe–Salpeter equation under covariant instantaneous ansatz to calculate leptonic decay constants of unequal mass pseudoscalar mesons like π^±, K, D, D_S and B, and radiative decay constants of neutral pseudoscalar mesons like π⁰ and η_c into two photons. In the Dirac structure of hadronic Bethe–Salpeter wave function, the covariants are incorporated from their complete set in accordance with a recently proposed power counting rule. The contribution of both leading order and next-to-leading order Dirac covariants to decay constants are studied. The results are found to improve and hence validating the power counting rule which provides a practical means of incorporating Dirac covariants in the Bethe–Salpeter wave function for a hadron.

In this work, we have employed Bethe–Salpeter equation (BSE) under Covariant Instantaneous Ansatz (CIA) to study radiative decays of light vector mesons through the process: h→h'γ, taking h and h' as equal mass light vector and pseudoscalar mesons, respectively. The decay widths calculated for these processes are in reasonable agreement with data. The motivation for this work was our intention to resolve the problems involved in calculations of triangle quark-loop diagrams which appear in processes such as radiative meson decays, meson form factors, strong decays of mesons, etc., in BSE under CIA, which give rise to complexities in amplitudes (as pointed out earlier in Ref. 1) due to the presence of the time-like momentum components in Gaussian factors associated with the vertex functions of the participating hadrons. In this work we try to highlight this problem and then demonstrate a mathematical procedure which might lead to calculations of such processes in BSE under CIA.

The mass spectra and decay properties of $B$ and $B_s$ mesons are obtained using the nonrelativistic potential model by applying the variational approach. The quark–anti-quark potential used in our model consists of a Hulthen potential and a confining linear potential. The hyper-fine interaction is introduced to obtain the splittings of the spin-singlet and triplet states, while the spin–orbit and tensor interactions provide the fine structure splittings. The model parameters and the wave functions that reproduce the mass spectra are used to investigate the decay properties of $B$ and $B_s$ mesons. The mass spectra of $B$ and $B_s$ mesons have been enhanced using coupled channel effects.

We study the production cross-sections and radiative decay widths of heavy quarkonia (charmonia and bottomonia) in magnetized nuclear matter. The production cross-sections of the $\psi (3770)$ and $\mathrm{\Upsilon }(4S)$, from the $D\bar{D}$ and $B\bar{B}$ scatterings, respectively, are studied from the medium modifications of the masses and partial decay widths to open charm (bottom) mesons, of these heavy flavor mesons. Within a chiral effective model, the masses of the vector and pseudoscalar charmonium (bottomonium) states are calculated from the medium modification of a dilaton field, $\chi$, which mimics the gluon condensates of quantum chromodynamics (QCD). The effects of the Dirac sea (DS) and the anomalous magnetic moments (AMMs) of the nucleons are taken into consideration in this study. In the presence of a magnetic field, there is mixing of the pseudoscalar (P) meson and the longitudinal component of the vector (V) meson (PV mixing), which leads to appreciable modifications of their masses. The radiative decay widths of the vector (V) heavy quarkonia to the pseudoscalar (P) mesons ($J/\psi \to {\eta }_c(1S)\gamma$, $\psi (2S)\to {\eta }_c(2S)\gamma$ and $\psi (1D)\to {\eta }_c(2S)\gamma$ for the charm sector and $\mathrm{\Upsilon }(NS)\to {\eta }_b(NS)\gamma$, $N=1,2,3,4$, for the bottom sector) in the magnetized asymmetric nuclear matter are also investigated in this work. The difference in the mass of the transverse component from the longitudinal component of the vector meson, arising due to PV mixing, is observed as a double peak structure in the invariant mass spectrum of the production cross-section of $\psi (3770)$. This is observed to be appreciably more pronounced as the value of the magnetic field is increased. For the bottomonium ($\mathrm{\Upsilon }(4S)$) production cross-section, the effect of the PV mixing effect is observed to be marginal, and there is observed to be a downward shift in the peak position due to the DS contributions. The modifications of the production cross-sections as well as the radiative decay widths of the heavy quarkonia in the magnetized matter should have observable consequences on the production of these heavy flavor mesons resulting from ultra-relativistic peripheral heavy ion collision experiments, where the created magnetic field can be extremely large.

We present a study of the inclusive photon spectrum from 6.3 million J/ψ decays collected with the KEDR detector at the VEPP-4M e⁺e^- collider. We measure the branching fraction of the radiative decay J/ψ → η_cγ, η_c width and mass. Taking into account an asymmetric photon line shape we obtain: M_ηc = (2978.1 ± 1.4 ± 2.0) MeV/c², Γ_ηc = (43.5 ± 5.4 ± 15.8) MeV, .

A study of the light-meson couplings to the single photon in the framework of the covariant oscillator quark model (COQM) is reported. The transition rates of {ρ(770), b₁(1235), a₁(1260), a₂(1320), π₂(1670), ρ₃(1690), ρ(1700)}^± into π^±γ, being expected to be measured by the COMPASS collaboration in their Primakoff-reaction experiments, are calculated. It could be useful not only for understanding the internal structures of observed light-quark mesons and their quark-model classification but also for the ongoing experimental studies by COMPASS.

We review recent experimental results on rare charged kaon decays from ISTRA+ experiment. The obtained branching fractions are compared with theoretical predictions. For Kl3γ decays the estimations of T-odd asymmetry are given. The value of |V_us| is extracted from BR(Ke3).