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).     

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.     

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.     

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°).     

First observation of the KS→π0γγ decay

Using the NA48 detector at the CERN SPS, 31 K_S→π⁰γγ candidates with an estimated background of 13.7±3.2 events have been observed. This first observation leads to a branching ratio of BR(K_S→π⁰γγ)_z>0.2=(4.9±1.6_stat±0.9_syst)×10⁻⁸ in agreement with Chiral Perturbation Theory predictions.     

First observation of the decays B(0) → D(+)K(-)π(+)π(-) and B(-) → D(0)K(-)π(+)π(-)

First observations of the Cabibbo-suppressed decays B(0) → D(+)K(-)π(+)π(-) and B(-) → D(0)K(-)π(+)π(-) are reported using 35 pb(-1) of data collected with the LHCb detector. Their branching fractions are measured with respect to the corresponding Cabibbo-favored decays, from which we obtain B(B(0) → D(+)K(-)π(+)π(-))/B(B(0) → D(+)π(-)π(+)π(-))=(5.9±1.1±0.5)×10(-2) and B(B(-) → D(0)K(-)π(+)π(-))/B(B(-) → D(0)π(-)π(+)π(-))=(9.4±1.3±0.9)×10(-2), where the uncertainties are statistical and systematic, respectively. The B(-) → D(0)K(-)π(+)π(-) decay is particularly interesting, as it can be used in a similar way to B(-) → D(0)K(-) to measure the Cabibbo-Kobayashi-Maskawa phase γ.     

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 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 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→ao(980)π0 and B-→a0-(980)π0 decays can be large, about (70-80)% for α = 100°.     

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-.     

Isotopic Symmetry Breaking in the η(1405) → f0(980)π0 → π+π–π0. Decay through a $$K\bar K$$ Loop Diagram and the Role of Anomalous Landau Thresholds

Anomalous isotopic symmetry breaking in the η(1405) → f₀(980)π⁰ → π+π–π⁰ decay through a mechanism featuring anomalous Landau thresholds in the form of logarithmic triangle singularities, i.e., through the \(\eta (1405) \to (K*\bar K + \bar K*K) \to ({K^ + }{K^ - } + {K^0}{\bar K^0}){\pi ^0} \to {f_0}(980){\pi ^0} \to {\pi ^ + }{\pi ^ - }{\pi ^0}\) transition, has been analyzed. It has been shown that this effect can be correctly quantified only by taking into account the nonzero K* width. Different scales of isotopic symmetry breaking associated with the K⁺–K⁰ mass difference are compared.     

First observation of B(s)(0) → J/ψη and B(s)(0) → J/ψη'

We report first observations of B(s)(0) → J/ψη and B(s)(0) → J/ψη'. The results are obtained from 121.4 fb(-1) of data collected at the Υ(5S) resonance with the Belle detector at the KEKB e+ e- collider. We obtain the branching fractions B(B(s)(0) → J/ψη)=[5.10±0.50(stat)±0.25(syst)(-0.79)(+1.14)(N(B(s)(*) B(s)(*))]×10(-4), and B(B(s)(0) → J/ψη')=[3.71±0.61(stat)±0.18(syst)(-0.57)(+0.83)(N(B(s)(*) B(s)(*))]×10(-4). The ratio of the two branching fractions is measured to be (B(B(s) → J/ψη'))/(B(B(s) → J/ψη))=0.73±0.14(stat)±0.02(syst).     

A test of CPT symmetry in K0 vs (K-)0→π+π-π0 decays

I show that the CP-violating asymmetry in K0 vs K-0→π+π-π0 decays differs from that in KL→π+π-,KL→π0π0 or the semileptonic KL transitions,if there exists CPT violation in K0-K-0 mixing.A delicate measurement of this difference at a super flavor factory(e.g.,the φ factory)will provide us with a robust test of CPT symmetry in the neutral kaon system.     

Dynamics of η→3π0 decay

The η→3π⁰ decay was studied with the SND detector at the VEPP-2Me ⁺ e ^? collider. The parameter that describes deviation of the Dalitz plot of events from a uniform distribution was found to be α=?0.010±0.021±0.010.     

Puzzle of anomalously large isospin violations in η(1405/1475)→3π

The BES-III Collaboration recently reported the observation of anomalously large isospin violations in J/ψ→γη(1405/1475)→γπ(0)f(0)(980)→γ+3π, where the f(0)(980) in the ππ invariant mass spectrum appears to be much narrower (~10 MeV) than the peak width (~50 MeV) measured in other processes. We show that a mechanism, named as triangle singularity (TS), can produce a narrow enhancement between the charged and neutral KKˉ thresholds, i.e., 2m(K(±))~2m(K(0)). It can also lead to different invariant mass spectra for η(1405/1475)→a(0)(980)π and KK ˉ*+c.c., which can possibly explain the long-standing puzzle about the need for two close states η(1405) and η(1475) in ηππ and KKˉπ, respectively. The TS could be a key to our understanding of the nature of η(1405/1475) and advance our knowledge about the mixing between a(0)(980) and f(0)(980).     

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.     

Measurement of the f1(1285) → π+π−π0 decay

The isospin symmetry-breaking (ISB) decay f ₁(1285) → π⁺π^?π⁰ has been studied at the VES facility. The branching ratio is measured: $\frac{{BR\left( {f_1 \to \pi ^ + \pi ^ - \pi ^0 } \right)}} {{BR\left( {f_1 \to \eta \pi ^ + \pi ^ - } \right)}} = 0.86 \pm 0.16_{ - 0.20}^{ + 0.70} \%Low-energy resonances in ³¹P(p, α ²⁸Si and ³⁵Cl(p, α)³²S were studied directly in order to gain a better understanding of reaction cycling in the Si-Ar region in novae. New resonance strengths at E _c.m. = 600 and 622 keV in ³¹P(p, α)²⁸Si were measured (ωγ _{p, α} = (2.2#x00B1;0.7) × 10^?2 eV and ωγ _{p, α} = (0.99±0.08) eV, respectively) as well as the E _c.m. = 610 keV resonance in ³⁵Cl(p, α)³²S [ωγ _{p, α} = (1.2±0.2) × 10^?2 eV], the lowest energy that any resonance in this reaction has been observed, directly or indirectly. The strengths of these resonances were found to be lower than previously determined, resulting in even weaker cycling in the Si-Ar region.     

A test of CPT symmetry in K^0 vs K^0→π^＋π^-π^0 decays

I show that the CP-violating asymmetry in K^0 vs K^0→π^＋π^-π^0 decays differs from that in KL→π^＋π^-, KL →π^0π^0 or the semileptonic KL transitions, if there exists CPT violation in K^0-K^0 mixing. A delicate measurement of this difference at a super flavor factory （e.g., the φ factory） will provide us with a robust test of CPT symmetry in the neutral kaon system.     

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（Bˉ^0 → f0（980） π^0） ～ 2.6×10^-7,Br（Bˉ^0 → f0（980） η） ～ 2.5×10^-7 and Br（Bˉ^0 → f0（980） η ） ～ 6.7×10^-7,which are consistent with both the QCD factorization predictions and the experimental upper limits.     

Search for CP violation in the decays D(0)→K(S)(0)P(0)

We have searched for CP violation in the decays D(0)→K(S)(0)P(0) where P(0) denotes a neutral pseudoscalar meson that is either a π(0), η, or η' using KEKB asymmetric-energy e(+)e(-) collision data corresponding to an integrated luminosity of 791 fb(-1) collected with the Belle detector. No evidence of significant CP violation is observed. We report the most precise CP asymmetry measurement in the decay D(0)→K(S)(0)π(0) to date: A(CP)(D(0)→K(S)(0)π(0))=(-0.28±0.19±0.10)%. We also report the first measurements of CP asymmetries in the decays D(0)→K(S)(0)η and D(0)→K(S)(0)η': A(CP)(D(0)→K(S)(0)η)=(+0.54±0.51±0.16)% and A(CP)(D(0)→K(S)(0)η')=(+0.98±0.67±0.14)%, respectively.     

Search for the rare decays K(L)→π0π0μ+μ- and K(L)→π0π0X0→π0π0μ+μ-

The KTeV E799 experiment has conducted a search for the rare decays, K(L)→π(0)π(0)μ(+)μ(-) and K(L)→π(0)π(0)X(0)→π(0)π(0)μ(+)μ(-), where the X(0) is a possible new neutral boson that was reported by the HyperCP experiment with a mass of (214.3 ± 0.5) MeV/c(2). We find no evidence for either decay. We obtain upper limits of Br(K(L)→π(0)π(0)X(0)→π(0)π(0)μ(+)μ(-)) < 1.0 × 10(-10) and Br(K(L)→π(0)π(0)μ(+)μ(-)) < 9.2 × 10(-11) at the 90% confidence level. This result rules out the pseudoscalar X(0) as an explanation of the HyperCP result under the scenario that the dsX(0) coupling is completely real.