Recent results from BABAR

The BABAR Collaboration at SLAC continues to produce a wide variety of publications on interesting and unique topics despite having ceased data-collection operations more than 10 years ago. Presented here are the results of three recent studies. The first is on the direct measurement of the B± → K± X(3872) branching fraction, allowing the first determination of the branching fractions of the exotic X(3872) charmonium state. The second is a publication on the first observation of the D0 → K−π+e+e− branching fraction. The third is on searches for lepton flavor and lepton number violating decays in D0 meson decays, resulting in improvements over existing limits by factors that vary from 20 to almost 800 depending on the D0 decay channel.

Calculation of the $$B\rightarrow K_{0,2}^*(1430)f_0(980)/\sigma $$ decays in the perturbative QCD approach

Motivated by the observations of the decays $$B^0 \rightarrow K_0^{*}(1430)^0 f_0(980)$$B0→K0∗(1430)0f0(980) and $$ B^0 \rightarrow K_2^{*}(1430)^0 f_0(980)$$B0→K2∗(1430)0f0(980) from BaBar collaboration, we study the $$B^{0(+)} \rightarrow K_{0,2}^{*}(1430)^{0(+)} f_0(980)/\sigma $$B0(+)→K0,2∗(1430)0(+)f0(980)/σ decays in the perturbative QCD approach for the first time. In the absence of reliable nonperturbative wave functions we only assume the scalar meson $$f_0(980)$$f0(980) and $$\sigma $$σ are two-quark ground states. In our calculations, these decays are all dominated by the hard-scattering emission and annihilation diagrams, while the factorizable emission diagrams are forbidden or suppressed heavily by the vector decay constants. Furthermore, the branching fractions are sensitive to the mixing between $$f_0(980)$$f0(980) and $$\sigma $$σ. Comparing our results with the experimental data, a large mixing angle $$\theta $$θ is favored. Taking $$\theta =145^\circ $$θ=145∘, the orders of branching fractions of $$B \rightarrow K_0^{*}(1430)^0 \sigma $$B→K0∗(1430)0σ, $$B \rightarrow K_{2}^{*}(1430)^0 \sigma $$B→K2∗(1430)0σ and $$B \rightarrow K_{0,2}^{*}(1430)^0 f_0(980)$$B→K0,2∗(1430)0f0(980) are predicted to be $$10^{-4}$$10-4, $$10^{-5}$$10-5 and $$10^{-6}$$10-6, respectively, which can be measured in the current experiments such as LHCb and Belle-2. In addition, although these decays are penguin dominant, the mixing also leads to large direct CP asymmetries in these decays. With the precise data in future, our results could shed light on the inner structure of the scalar mesons and can be used to determine the mixing angle of the $$\sigma -f_0(980)$$σ-f0(980) system.

A no-go theorem for non-standard explanations of the $\tau\to K_S\pi\nu_\tau$ CP asymmetry

A new tensor interaction is the only possibility to explain the \boldsymbol{2.8\sigma}2.8𝛔 tension observed by the BaBar collaboration in the CP asymmetry in \boldsymbol{\tau\to K_S\pi\nu_\tau}𝛕→𝐊𝐒𝛑𝛎𝛕 with physics beyond the Standard Model (BSM) realized above the electroweak scale. However, the strong phase generated by the interference between vector and tensor phases is suppressed by at least two orders of magnitude due to Watson’s final-state-interaction theorem, and the strength of the CP-violating tensor interaction is strongly constrained by bounds from the neutron electric dipole moment and \boldsymbol{D}𝐃–\boldsymbol{\bar{D}}𝐃‾ mixing. As a result, a confirmation of the tension at Belle II would point to light BSM physics.

Semi-leptonic production of DsJ(3040) and DJ(3000) in Bs and B decays

In this paper, we study the productions of the newly detected states [Formula: see text] and [Formula: see text] observed by BaBar Collaboration and LHCb Collaboration. We assume these states to be the [Formula: see text] and [Formula: see text] states with the quantum number [Formula: see text] in our work. The results of improved Bethe–Salpeter (BS) method indicate that the semi-leptonic decays via [Formula: see text] and [Formula: see text] into [Formula: see text] and [Formula: see text] have considerable branching ratios, for example, [Formula: see text], [Formula: see text], which shows that these semi-leptonic decays can be accessible in experiments.

Determination of the magnetic dipole moment of the rho meson using four-pion electroproduction data

We determine the magnetic dipole moment of the rho meson using preliminary data from the BaBar Collaboration for the [Formula: see text] process, in the center of mass energy range from 0.9 to 2.2 GeV. We describe the [Formula: see text] vertex using a vector meson dominance model, including the intermediate resonance contributions relevant at these energies. We find that [Formula: see text] in [Formula: see text] units.

RECENT τ LEPTON RESULTS FROM BABAR

We report recent measurements on τ leptons obtained by the BABAR collaboration using the entire recorded sample of electron-positron collisions at and around the Υ(4S) (about 470fb-1). The events were recorded at the PEP-II asymmetric collider at the SLAC National Accelerator Laboratory. The measurements include high multiplicity τ decay branching fractions with 3 or 5 charged particles in the final state, a search for the second class current the τ decay τ → πη′ν, τ branching fractions into final states containing two KS mesons, [Formula: see text], with h = π, K, and preliminary measurements of hadronic spectra of τ decays with three hadrons (τ- → h-h+h-ντ decays, where h = π, K). The results improve the experimental knowledge of the τ lepton properties and can be used to improve the precision tests of the Standard Model.

THE CHARMED PENTAQUARK Θc(3250) FROM QCD SUM RULES

We study, using the QCD sum rule framework, the possible existence of a charmed pentaquark that we call Θc(3250). In the QCD side we work at leading order in αs and consider condensates up to dimension 10. The mass obtained: mΘc = (3.21±0.13) GeV, is compatible with the mass of the structure seen by BaBar Collaboration in the decay channel [Formula: see text].

Constituent quark model study of exotic meson states

Using high precision numerical method based on Gaussian expansion method for few-body systems, we studied the spectra of possible exotic meson states composed of [Formula: see text] (Q = c, b, and q = u, d, s) in non-relativistic constituent quark model. Some newly released experimental data by the BES, Belle, BaBar Collaboration can be interpreted in our calculation. Several possible exotic states are also predicted.

DETERMINATION OF THE MAGNETIC DIPOLE MOMENT OF THE RHO MESON

We determine the magnetic dipole moment of the rho meson using preliminary data from the BaBar Collaboration for the e+e- → π+π-2π0 process, in the center of mass energy range from 0.9 to 2.2 GeV. We describe the γ* → 4π vertex using a vector meson dominance model, including all intermediate resonance contributions. We find that μρ = 2.1 ± 0.5 [e/2mρ].