Decay Widths Of Mesons Research Articles

Preliminary lattice QCD calculation of the σ meson decay width

We report an exploratory lattice QCD investigation of the σ meson decay width though the s-wave scattering phase shift for isospin I = 0 pion-pion (ππ) system. Rummukainen-Gottlieb formula is used to estimate the scattering phase for the two-pion system in the moving frame, which demonstrate the presence of a resonance around σ meson. Using the effective range formula we extract the effective σ → ππ coupling constant as g σππ = 2.69(44) GeV, which is consistent with the theoretical predictions. The estimated decay width is about 236 ± 49 MeV. These simulations are carried out on a 163 × 48 MILC gauge configuration with the N f = 2 + 1 flavor of the “Asqtad” improved staggered dynamical sea quarks at m π /m σ ≈ 0.414 and the lattice spacing a ≈ 0.15 fm.

Determination of theη-η′mixing angle

We extract $\eta$-$\eta^\prime$ mixing angle and the ratios of decay constants of light pseudoscalar mesons $\pi^0$, $\eta$ and $\eta^\prime$ using recently available BaBar measurements on $\eta$-photon and $\eta^\prime$-photon transition form factors and more accurate experimental data for the masses and two-photon decay widths of the light pseduoscalar mesons.

Chiral particle decay of heavy-light mesons in a relativistic potential model

Partial decay widths of the heavy-light mesons, $D, D_s, B,$ and $B_s$, emitting one chiral particle ($\pi$ or $K$) are evaluated in the framework of a relativistic potential model. Decay amplitudes are calculated by keeping the Lorentz invariance as far as possible and use has been made of the Lorentz-boosted relativistic wave functions of the heavy-light mesons. One of predictions of our calculation is very narrow widths of a few keV for yet undsicovered $B_s(0^+, 1^+)$ mesons corresponding to ${^{2S+1}L_J}={^3P_0}$ and $"{^3P_1}"$ assuming their masses to be 5617 and 5682 MeV, respectively, as calculated in our former paper. In the course of our calculation, new sum rules are discovered on the decay widths in the limit of $m_Q\to \infty$. Among these rules, $ \Gamma(D_{s0}^*(2317)\to D_s+\pi)=\Gamma (D_{s1}(2460)\to D_s^*+\pi) $ and $ \Gamma(B_{s0}^*(5615)\to B_s+\pi)=\Gamma (B_{s1}(5679)\to B_s^*+\pi) $ are predicted to hold with a good accuracy.

Analysis of Vector Meson Transitions Among Heavy Quarkonium States

In this article, we study the vector meson transitions among the charmonium and bottomonium states with the heavy quark effective theory in a systematic way, and make predictions for the ratios among the vector meson decay widths of a special multiplet to another multiplet. The predictions can be confronted with the experimental data in the future.

The preliminary lattice QCD calculation of κ meson decay width

We present a direct lattice QCD calculation of the $\kappa$ meson decay width with the s-wave scattering phase shift for the isospin $I=1/2$ pion-kaon ($\pi K$) system. We employ a special finite size formula, which is the extension of the Rummukainen-Gottlieb formula for the $\pi K$ system in the moving frame, to calculate the scattering phase, which indicates a resonance around $\kappa$ meson mass. Through the effective range formula, we extract the effective $\kappa \to \pi K$ coupling constant $g_{\kappa \pi K} = 4.54(76)$ GeV and decay width $\Gamma = 293 \pm 101$ MeV. Our simulations are done with the MILC gauge configurations with $N_f=2+1$ flavors of the "Asqtad" improved staggered dynamical sea quarks on a $16^3\times48$ lattice at $(m_\pi + m_K) / m_\kappa \approx 0.8$ and lattice spacing $a \approx 0.15$ fm.

Upgraded breaking of the HLS model: a full solution to the τ−e + e − and ϕ decay issues and its consequences on g−2 VMD estimates

The muon anomalous magnetic moment a μ and the hadronic vacuum polarization are examined using data analyzed within the framework of a suitably broken HLS model. The analysis relies on all available scan data samples and leaves provisionally aside the existing ISR data. Our HLS model based global fit approach allows for a better check of consistency between data sets and we investigate how results depend on different strategies which may be followed. Relying on global fit qualities, we find several acceptable solutions leading to ambiguities in the reconstructed value for (a μ )th. Among these, the most conservative solution is \(a_{\mu}^{\mathrm{had,LO}}[\mathrm{HLS\ improved}]=687.72(4.63) \times10^{-10}\) and (a μ )th=11 659 175.37(5.31)×10−10 corresponding to a 4.1σ significance for the difference Δa μ =(a μ )exp−(a μ )th. It is also shown that the various contributions accessible through the model yield uniformly a factor 2 improvement of their uncertainty. The breaking procedure implemented in the HLS model is an extension of the former procedure based on a mechanism defined by Bando, Kugo and Yamawaki (BKY). This yields a quite satisfactory simultaneous description of most e + e − annihilation channels up to and including the ϕ meson (π + π −, π 0 γ, ηγ, π + π − π 0, K + K −, \(K^{0} \overline{K}^{0}\)) and of a set of 10 (mostly radiative) decay widths of light mesons. It also allows to achieve the proof of consistency between the e + e −→π + π − annihilation and the τ ±→π ± π 0 ν decay and gives a solution to the reported problem concerning the measured partial width ratio \(\varGamma(\phi\to K^{+}K^{-})/\varGamma(\phi\to K^{0} \overline{K}^{0})\). Prospects for improving the VMD based estimates of a μ are emphasized.

Decay widths of large-spin mesons from the noncritical string/gauge duality

In this paper, we use the non-critical string/gauge duality to calculate the decay widths of large-spin mesons. Since it is believed that the string theory of QCD is not a ten dimensional theory, we expect that the non-critical versions of ten dimensional black hole backgrounds lead to better results than the critical ones. For this purpose we concentrate on the confining theories and consider two different six dimensional black hole backgrounds. We choose the near extremal AdS6 model and the near extremal KM model to compute the decay widths of large-spin mesons. Then, we present our results from these two non-critical backgrounds and compare them together with those from the critical models and experimental data.

Resonance parameters of theρmeson from lattice QCD

We perform a nonperturbative lattice calculation of the $P$-wave pion-pion scattering phase in the $\ensuremath{\rho}$-meson decay channel using two flavors of maximally twisted mass fermions at pion masses ranging from 480 to 290 MeV. Making use of finite-size methods, we evaluate the pion-pion scattering phase in the center-of-mass frame and two moving frames. Applying an effective range formula, we find a good description of our results for the scattering phase as a function of the energy covering the resonance region. This allows us to extract the $\ensuremath{\rho}$-meson mass and decay width and to study their quark mass dependence.

VARIATIONAL CALCULATION OF K-pp WITH CHIRAL SU(3)-BASED $\bar KN$ INTERACTION

The prototype of a [Formula: see text] nuclear cluster, K-pp, has been investigated using effective [Formula: see text] potentials based on chiral SU (3) dynamics. Variational calculation shows a bound state solution with shallow binding energy B(K-pp) = 20 ± 3 MeV and broad mesonic decay width [Formula: see text]. The [Formula: see text] pair in the K-pp system exhibits a similar structure as the Λ(1405). We have also estimated the dispersive correction, p-wave [Formula: see text] interaction, and two-nucleon absorption width.

A precision measurement of the neutral Pion lifetime via the Primakoff effect

The main parameters and technical features of the PrimEx experiment conducting in Jefferson Lab (USA) are presented. One of the main parts of the PrimEx setup-electromagnetic calorimeter is described in details. Value of π0 meson decay width into two γ-quanta, obtained from PrimEx 2004 year data is Γ(πo → 2γ) = 7.82 eV 2.2% (stat.) 2.1% (syst.)

Vacuum properties of mesons in a linear sigma model with vector mesons and global chiral invariance

We present a two-flavor linear sigma model with global chiral symmetry and vector and axial-vector mesons. We calculate $\ensuremath{\pi}\ensuremath{\pi}$ scattering lengths and the decay widths of scalar, vector, and axial-vector mesons. It is demonstrated that vector and axial-vector meson degrees of freedom play an important role in these low-energy processes and that a reasonable theoretical description requires globally chirally invariant terms other than the vector-meson mass term. An important question for meson vacuum phenomenology is the quark content of the physical scalar ${f}_{0}(600)$ and ${a}_{0}(980)$ mesons. We investigate this question by assigning the quark-antiquark $\ensuremath{\sigma}$ and ${a}_{0}$ states of our model with these physical mesons. We show via a detailed comparison with experimental data that this scenario can describe all vacuum properties studied here except for the decay width of the $\ensuremath{\sigma}$, which turns out to be too small. We also study the alternative assignment ${f}_{0}(1370)$ and ${a}_{0}(1450)$ for the scalar mesons. In this case the decay width agrees with the experimental value, but the $\ensuremath{\pi}\ensuremath{\pi}$ scattering length ${a}_{0}^{0}$ is too small. This indicates the necessity to extend our model by additional scalar degrees of freedom.

An independent-quark model calculation for radiative decay widths of mesons in static and beyond static approximation

We perform a static calculation of decay widths for radiative transitions of mesons within the conventional picture of photon emission by a confined quark and (or) antiquark. As the calculation based on the moderate momentum transfer allows some amount of uncertainty to creep into the model predictions, we further apply the model for a more realistic calculation beyond the static approximation, taking into account some momentum-dependent effects due to the recoil of the daughter meson. The results obtained for the decay widths of radiative transitions of light mesons are improved and are in good agreement with the experimental values. The predictions on the decay rates of heavy mesons are also affected and are comparable with those of other model predictions.

Radiative decays of scalar mesons σ(600), f 0(980) and a 0(980) in the local Nambu-Jona-Lasinio model

Abstract The two-photon decay widths of scalar mesons σ(600), f 0(980) and a 0(980) as well a 0 → ju(ω)γ and f 0 → ju(ω)γ are calculated in the framework of the local Nambu-Jona-Lasinio model. The contributions of the quark loops (Hartree-Fock approximation) and the meson loops (next 1/N c-approximation where N c is the number of colors) are taken into account. The values of these contributions, as we show, are of the same order of magnitude. For the f 0 decay the K-loop contribution plays the dominant role. The results for two-gamma decays are in satisfactory agreement with modern experimental data. The predictions for a 0 → ju(ω)γ and f 0 → ju(ω)γ widths are given.

M1 TRANSITIONS OF MESONS IN A POTENTIAL MODEL OF INDEPENDENT QUARKS

The decay widths for M1 transitions of mesons are calculated in a relativistic potential model of independent quarks with its parameters determined from a fit to the mass splittings of the ground state mesons in the strange, charm and bottom flavor sector. A more realistic calculation of the decay widths is performed beyond static approximation incorporating some momentum dependence due to recoil of the daughter meson. The model accounts well for the observed decay widths of light mesons and predicts decay rates of heavy mesons which are comparable with those of other model calculations.

2γ decays of scalar mesons (σ(600), f 0(980), and a 0(980)) in the Nambu-Jona-Lasinio model

The two-photon decay widths of scalar mesons \sigma(600), f_0(980) and a_0(980) are calculated in framework of the local Nambu-Jona-Lasinio model. The contributions of the quark loops (Hartree-Fock approximation) and the meson loops (next 1/N_c-approximation where N_c is the number of colors) are taken into account. These contributions, as we show, are the values of the same order of magnitude. For the f_0 decay the K-loop contribution turns out to play the dominant role. The results are in satisfactory agreement with modern experimental data.

Two-photon mechanism of scalar meson production by colliding beams

Cross sections of scalar mesons f 0(980), a 0(980), and σ(600) production by colliding electron-positron beams are calculated. Two-photon decay widths of scalar mesons obtained in the Nambu-Jona-Lasinio model are used with quark and meson loops taken into account.

Chiral SU(3) dynamics and the quasibound K – pp cluster

The prototype of a Kbar nuclear cluster, K^-pp, has been investigated using effective KbarN potentials based on chiral SU(3) dynamics. Variational calculation shows a bound state solution with shallow binding energy B(K^-pp)=20 \pm 3 MeV and broad mesonic decay width \Gamma(KbarNN -> \pi Y N)=40 - 70 MeV. The KbarN(I=0) pair in the K^-pp system exhibits a similar structure as the \Lambda(1405). We have also estimated the dispersive correction, p-wave KbarN interaction, and two-nucleon absorption width.

Variational calculation of [formula omitted] with Chiral SU(3)-based [formula omitted] interaction

The prototype of a K ¯ nuclear cluster, K − p p , has been investigated using effective K ¯ N potentials based on chiral SU(3) dynamics. Variational calculation shows a bound state solution with shallow binding energy B ( K − p p ) = 20 ± 3 MeV and broad mesonic decay width Γ ( K ¯ N N → π Y N ) = 40 − 70 MeV . The K ¯ N ( I = 0 ) pair in the K − p p system exhibits a similar structure as the Λ ( 1405 ) . We have also estimated the dispersive correction, p-wave K ¯ N interaction, and two-nucleon absorption width.

Probing two-photon decay widths of mesons at energies available at the CERN Large Hadron Collider (LHC)

Meson production cross sections in ultraperipheral relativistic heavy ion collisions at the CERN Large Hadron Collider are revisited. The relevance of meson models and of exotic QCD states is discussed. This study includes states that have not been considered before in the literature.

Variational calculation of theppK−system based on chiral SU(3) dynamics

The ${\mathit{ppK}}^{\ensuremath{-}}$ system, as a prototype for possible quasibound $\overline{K}$ nuclei, is investigated using a variational approach. Several versions of energy-dependent effective $\overline{K}N$ interactions derived from chiral SU(3) dynamics are employed as input, together with a realistic $\mathit{NN}$ potential (Av18). Taking into account theoretical uncertainties in the extrapolations below the $\overline{K}N$ threshold, we find that the antikaonic dibaryon ${\mathit{ppK}}^{\ensuremath{-}}$ is not deeply bound. With the driving $s$-wave $\overline{K}N$ interaction the resulting total binding energy is $B({\mathit{ppK}}^{\ensuremath{-}})=20\ifmmode\pm\else\textpm\fi{}3$ MeV and the mesonic decay width involving $\overline{K}N\ensuremath{\rightarrow}\ensuremath{\pi}Y$ is expected to be in the range 40--70 MeV. Properties of this quasibound ${\mathit{ppK}}^{\ensuremath{-}}$ system (such as density distributions of nucleons and antikaon) are discussed. The $\ensuremath{\Lambda}(1405)$, as an $I=0$ quasibound state of $\overline{K}$ and a nucleon, appears to survive in the ${\mathit{ppK}}^{\ensuremath{-}}$ cluster. Estimates are given for the influence of $p$-wave $\overline{K}N$ interactions and for the width from two-nucleon absorption $(\overline{K}\mathit{NN}\ensuremath{\rightarrow}\mathit{YN})$ processes. With inclusion of these effects and dispersive corrections from absorption, the ${\mathit{ppK}}^{\ensuremath{-}}$ binding energy is expected to be in the range 20--40 MeV, whereas the total decay width can reach 100 MeV but with large theoretical uncertainties.