Study of scalar meson a_0(980) from B→a_0(980)π decays

In this paper,we calculate the branching ratios and the direct CP-violating asymmetries for decays B0 →a00(980)π0,a0+(980)π-,a0-(980)π+ and B- →a00(980)π-,a0-(980)π0 by employing the perturbative QCD(pQCD) factorization approach at the leading order.We found that(a) the pQCD predictions for the branching ratios are around(0.4-2.8)×10-6,consistent with currently available experimental upper limits;(b) the CP asymmetries of B0 →a00(980)π0 and B- →a0-(980)π0 decays can be large,about(70-80)% for α=100-.     

Study of scalar meson a0（980） from B → a0（980）π decays

In this paper, we calculate the branching ratios and the direct CP-violating asymmetries for decays B^0 → a0^0（980）π^0, a0^＋ （980）π^-, a0^-（980）π^＋ and B^- → a0^0 （980）π^-, a0^- （980）π^0 by employing the perturbative QCD （pQCD） factorization approach at the leading order. We found that （a） the pQCD predictions for the branching ratios are around （0.4-2.8） × 10^-6, consistent with currently available experimental upper limits; （b） the CP asymmetries of B^0→ a0^0（980）π^0 and B^- → a0^- （980）π^0 decays can be large, about （70-80）% for α= 100°.     

Study of scalar meson f 0(980) from B→f 0(980)K * decays

We show how parton distributions unintegrated over the parton transverse momentum, k _t , may be generated, at NLO accuracy, from the known integrated (DGLAP-evolved) parton densities determined from global data analyses. A few numerical examples are given, which demonstrate that sufficient accuracy is obtained by keeping only the LO splitting functions together with the NLO integrated parton densities. However, it is important to keep the precise kinematics of the process, by taking the scale to be the virtuality rather than the transverse momentum, in order to be consistent with the calculation of the NLO splitting functions.     

Study of f 0(980) and f 0(1500) from B s →f 0(980)π,f 0(1500)π decays

In this paper, we analyze the scalar mesons f ₀(980) and f ₀(1500) from the decays $\bar{B}^{0}_{s}\to f_{0}(980)\pi^{0},\allowbreak f_{0}(1500)\pi^{0}$ within Perturbative QCD approach. From the leading-order calculations, we find that (a) in the allowed mixing angle ranges, the branching ratio of $\bar{B}^{0}_{s}\to f_{0}(980)\pi^{0}$ is about (1.0～1.6)×10^?7, which is smaller than that of $\bar{B}^{0}_{s}\to f_{0}(980)K^{0}$ (the difference is a few times even one order); (b) the decay $\bar{B}^{0}_{s}\to f_{0}(1500)\pi^{0}$ is better to distinguish between the lowest lying state or the first excited state for f ₀(1500), because the branching ratios for two scenarios have about one-order difference in most of the mixing angle ranges; and (c) the direct CP asymmetries of $\bar{B}^{0}_{s}\to f_{0}(1500)\pi^{0}$ for two scenarios also exists great difference. In scenario II, the variation range of the value ${\mathcal{A}}^{\mathrm{dir}}_{CP}(\bar{B}^{0}_{s}\to f_{0}(1500)\pi^{0})$ according to the mixing angle in scenario II is very small, except for the values for mixing angles near 90° or 270°, while the variation range of ${\mathcal{A}}^{\mathrm{dir}}_{CP}(\bar{B}^{0}_{s}\to f_{0}(1500)\pi^{0})$ in scenario I is very large. Compared with the future data for the decay $\bar{B}^{0}_{s}\to f_{0}(1500)\pi^{0}$ , it is easy to determine the nature of the scalar meson f ₀(1500).     

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

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.     

Study of B s 0 → µ+µ− and B d 0 → µ+µ− decays in flavor-changing Z′ models

Recently, the first evidence for the decay B _s ⁰ → μ ⁺ μ ^? has been announced by the LHCb Collaboration and the measured branching ratio B( _s ⁰ → μ ⁺) = (3.2 _?1.2 ^+1.5 ) × 10^?9 is in good agreement with the standard model (SM) expectation. It has also reported an upper limit for B(B _d ⁰ → μ ⁺ μ ^?) < 9.4 × 10^?10 at 95% confidence level. In this paper, we study the B _s ⁰ → μ ⁺ μ ^? and B _d ⁰ → μ ⁺ μ ^? rare decays in flavor-changing Z′ model. Our estimated branching ratios are enhanced from their SM values and provide signals for new physics.     

B→f0(980)(π,η') decays in the PQCD approach

Based on the assumption of a two-quark structure of the scalar meson f0(980), we calculate the branching ratios and CP-violating asymmetries for the four B→f0(980)π and B→f0(980)η(') decays by employing the perturbative QCD (Pqcd) factorization approach. The leading order Pqcd predictions for branching ratios are, Br(B-→f0(980)π-)～2.5×10-6, Br(B0→f0(980)πo)～2.6×10-7, Br(B0→f0(980)η)～ 2.5×10-7 and Br(B0→f0(980)η')～6.7×10-7, which are consistent with both the QCD factorization predictions and the experimental upper limits.     

Phenomenology of b→cτ■ decays in a scalar leptoquark model

During the past few years,signs of lepton flavor universality(LFU)violation have been observed in b→cτ■ and b→sl+l-transitions.Recently,the D* and τ polarization fractions P_L~D* and P_L~τ in B→D*τ■decay were likewise measured by the Belle collaboration.Motivated by these intriguing results,we revisit the RD(*)and RK(*) anomalies in a scalar leptoquark(LQ)model,where two scalar LQs,one of which is a S U(2)L singlet and the other a S U(2)L triplet,are introduced simultaneously.We consider five b→ cτ■ mediated decays,B→D(*)τ■,B_c→ηcτ■,Bc→J/ψt■,and ∧_b→∧_cτ■,and focus on the LQ effects on the q~2 distributions of the branching fractions,LFU ratios,and various angular observables in these decays.Under the combined constraints of the available data on RD(*),RJ/ψ,P_L~τ(D*),and pLD*,we perform scans for the LQ couplings and make predictions for a number of observables.Numerically it is found that both the differential branching fractions and LFU ratios are largely enhanced by the LQ effects,with the latter expected to provide testable signatures at the SuperKEKB and High-Luminosity LHC experiments.     

Do B meson decays exclude a light Higgs?

In the standard model with three generations a light Higgs boson will be produced in a quarter of all B meson decays. A novel calculation of the b → sH matrix element is given. Existing data on B meson decays excludes a light Higgs with mass less than 300 MeV or between 2 and 3.7 GeV. Because of theoretical uncertainties in the branching fractions for Higgs production and decay, a window between 300 MeV and 2 GeV is still allowed. Such a Higgs could be discovered at the ϒ (4S) in inclusive π⁺π⁻ or K⁺ K⁻ invariant mass plots, and in events with six kaons.     

First observation of η(1405) decays into f(0)(980)π0

The decays J/ψ → γ π+ π- π0 and J/ψ → γ π0 π0 π0 are analyzed using a sample of 225×10(6) J/ψ events collected with the BESIII detector. The decay of η(1405) → f(0)(980)π0 with a large isospin violation is observed for the first time. The width of the f(0)(980) observed in the dipion mass spectra is anomalously narrower than the world average. Decay rates for three-pion decays of the η' are also measured precisely.     

Annihilation contribution and B → a 0π, f 0 K decays

We analyze the and B^–,0 → f₀K^–,0 decays and show that a consistent phenomenological picture can be obtained within the factorization approximation. In this approach the O₆ operator provides the dominant contributions to the suppressed channel . An estimate of the annihilation form factor using perturbative QCD indicates that this contribution is not negligible, moreover interference with other penguin contributions includes a free parameter since the phase of the annihilation amplitude is not determined. Assumptions based on SU(2) isospin symmetry provide relations between different B decays involving one scalar and one pseudoscalar meson.     

Extraction of the CKM phase γ from the charmless two-body B meson decays

Using all experimentally measured charmless B → PP, PV decay modes, where P(V) denotes a light pseudoscalar(vector) meson, we extract the CKM angle γ by a global fit. All hadronic parameters are determined from the experimental data, such that the approach is least model dependent. The contributions of the various decay modes are classified by the topological weak Feynman diagram amplitudes, which are determined by the global fit.To improve the precision of the approach, we consider the flavor SU(3) breaking effects of the topological diagram amplitudes of the decay modes by including the form factors and decay constants. The fit result for the CKM angle γ is( 69.8 ± 2.1 ± 0.9)°. It is consistent with the current world average values but has a smaller uncertainty.     

Radiative decays and quark content of f 0(980) and φ(1020)

The quark structure of φ(1020) and f ₀(980) is studied on the basis of data on the radiative decays φ(1020) → γπ ⁰, γη, γη′, γ a ₀(980), γ f ₀(980) and f ₀(980) → γγ. The partial widths are calculated under the assumption that all the mesons under consideration are $\bar qq$ states: φ(1020) is a dominantly $s\bar s$ state ( $\eta ' = n\bar nsin\theta + s\bar scos\theta $ component contributes not more than 1%); η, η′, and π ⁰ are standard $q\bar q$ states, $\eta = n\bar ncos\theta - s\bar ssin\theta $ and $\eta ' = n\bar nsin\theta + s\bar scos\theta $ with θ?37°; and f ₀(980) is a e5 meson with the flavor wave function $n\bar ncos\varphi + s\bar ssin\varphi $ . The transition φ → γπ ⁰ specifies the admixture of the $n\bar n$ component in the φ meson: it is on the order of 0.5%. We argue that this order of $n\bar n$ value does not contradict data on the decay φ(1020) → γ a ₀(980). The partial widths calculated for the decays φ → γη, γη? are in reasonable agreement with experimental data. The measured branching-ratio value Br(φ→γf ₀(980))=(3.4±0.4 _?0.5 ^+1.5 ×10^?4) requires 25°≤|?|≤90°. For the decay f ₀(980) → γγ, the agreement with data, Γ(f ₀(980) → γγ)=0.28 _?0.13 ^+0.09 keV, is attained at either ?=85°±8° or ?=?46°±8°. A simultaneous analysis of the decays φ(1020) → γ f ₀(980) and f ₀(980) → γγ favors the solution with the negative mixing angle of ?=?48°±6°, setting f ₀(980) very close to the flavor octet (? _octet=±54.7°).     

Study ao（980）-f0（980） mixing in charmonium decays

In this proceeding, we propose to directly measure the a0^0（980）-f0 （980） mixing in J/ψ→φf0（980）→φa0^0（980） and Xc1→π^0a0^0（980） →π^0f0（980） with the upgraded Beijing Electron Positron Collider（BEPCII） with BESIII detector. We show that a narrow peak of about 8 MeV will be produced by the a0^0（980）-f0（980） mixing, and the predominant feature makes it standing out from the background contributions. The predicted branching ratios for these two reactions are both expected to be about O（10^-6）, which is unambiguously accessible with 10^9 J/ψ and 3 × 10^8 Xc1 at BESⅢ.     

On the possibility of observing a 0 0 (980)-ƒ 0(980) mixing in the reaction π − p → ηπ 0 n on a polarized target

It is shown that the spin asymmetry in the reaction π ^? p → a ₀ ⁰ (980)n → (ηπ ⁰)S _n is highly sensitive to the mixing of the a ₀ ⁰ (980) and ? ₀(980) resonances. At low momentum transfers (namely, in any of the intervals 0 ≤ ?t ≤ 0.025, …, 0.1 GeV²), the asymmetry normalized in such a way that it takes values between ?1 and 1must undergo a jump close inmagnitude to unity in the region of the ηπ ⁰ invariant masses between 0.965 and 1.01 GeV. A large jump of the asymmetry is due exclusively to a ₀ ⁰ (980)?? ₀(980) mixing. A very high resolution in the ηπ ⁰ invariant mass is not required for observing the jump of the asymmetry. The energy dependence of the polarization effect is expected to be rather weak; therefore, the polarization effect in question can be studied at any high energy—for example, in the range between 8 and 100 GeV.     

Analysis of the B 0(+) → J/ΨD 0(+) decays

We analyze B ⁰⁽⁺⁾ → J/ΨD ⁰⁽⁺⁾ decays by considering the contributions of annihilation diagrams. For each diagram, we calculate the branching ratios for various parameters X _A , which have played a significant role in our results. These parameters have been concluded from the divergence integrals in hard-scattering kernels. Here, we have considered three effective variables, including: Λ(225, 500 MeV), ρ _A (0, 1, 1/2), and φ _A . It is found that the most of the obtained data are placed in the experimental range at Λ = 225 MeV and Λ = 500 MeV for B ⁺ → J/ΨD ⁺ and B ⁰ → J/ΨD ⁰, respectively.     

Measurement of polarization and search for CP violation in B(s)0→φφ decays

We present the first measurement of polarization and CP-violating asymmetries in a B(s)(0) decay into two light vector mesons, B(s)(0)→φφ, and an improved determination of its branching ratio using 295 decays reconstructed in a data sample corresponding to 2.9 fb(-1) of integrated luminosity collected by the CDF experiment at the Fermilab Tevatron collider. The fraction of longitudinal polarization is determined to be f(L)=0.348±0.041(stat)±0.021(syst), and the branching ratio B(B(s)(0)→φφ)=[2.32±0.18(stat)±0.82(syst)]×10(-5). Asymmetries of decay angle distributions sensitive to CP violation are measured to be A(u)=-0.007±0.064(stat)±0.018(syst) and A(v)=-0.120±0.064(stat)±0.016(syst).