We study e+e-→π+π-hc at center-of-mass energies from 3.90 to 4.42 GeV by using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections are measured at 13 energies and are found to be of the same order of magnitude as those of e+e-→π+π-J/ψ but with a different line shape. In the π±hc mass spectrum, a distinct structure, referred to as Zc(4020), is observed at 4.02  GeV/c2. The Zc(4020) carries an electric charge and couples to charmonium. A fit to the π±hc invariant mass spectrum, neglecting possible interferences, results in a mass of (4022.9±0.8±2.7)  MeV/c2 and a width of (7.9±2.7±2.6)  MeV for the Zc(4020), where the first errors are statistical and the second systematic. The difference between the parameters of this structure and the Zc(4025) observed in the D*D[over ¯]* final state is within 1.5σ, but whether they are the same state needs further investigation. No significant Zc(3900) signal is observed, and upper limits on the Zc(3900) production cross sections in π±hc at center-of-mass energies of 4.23 and 4.26 GeV are set.

It has been shown recently that the anomalies observed inB → D ( * ) τν τ andB →K + − decays could be resolved with just one scalar leptoquark. Fitting to the current data on R(D ( * ) ) along with acceptable q 2 distributions inB → D ( * ) τν τ decays, four best-fit solutions for the operator coefficients have been found. In this paper, we explore the possibilities of how to discriminate these four solutions. Firstly, we find that two of them * With the discovery of heavy quark spin-flavor symmetry and the formulation of heavy quark effective theory (HQET) [1][2][3][4][5], it has become clear that the physical observables in semi-leptonic B → D ( * ) ν could be rather reliably predicted within the Standard Model (SM), especially at the zero recoil point, allowing therefore a reliable determination of the Cabibbo-Kobayashi-Maskawa (CKM) element V cb . It is also believed that the effect of New Physics (NP) beyond the SM should be tiny since these decays are induced by the tree-level charged current.However, the BaBar [6, 7], Belle [8,9] and LHCb [10] collaborations have recently observed anomalies in the ratios R(D ( * ) ) = B(B → D ( * ) τν τ ) B(B → D ( * ) ν ) , = e/µ . (1.1) The Heavy Flavor Average Group (HFAG) gives the average values [11] R(D) avg =0.397 ± 0.040 ± 0.028 , R(D * ) avg =0.316 ± 0.016 ± 0.010 , (1.2) which exceed the SM predictions [12, 13] R(D) SM =0.300 ± 0.008 , R(D * ) SM =0.252 ± 0.003 , (1.3) by 1.9σ and 3.3σ, respectively. Especially when the R(D)-R(D * ) correlation of −0.21 is taken into account, the tension with the SM predictions would be at 4.0σ level [11]. Theoretically, R(D) and R(D * ) can be rather reliably calculated, because they are independent of the CKM element |V cb | and, to a large extent, of the B → D ( * ) transition form factors.The above anomalies have been investigated extensively both within model-independent frameworks [14-35], as well as in some specific NP models where the b → cτν τ transition is mediated by leptoquarks [14, 15, 36-44], charged Higgses [14, 45-55], charged vector bosons [14, 56-58], and sparticles [ [59][60][61]. It is also interesting to point out that, besides the branching ratios, the measured differential distributions dΓ(B → D ( * ) τν)/dq 2 by BaBar [7] and Belle [8,9]

Given that the two-Higgs-doublet model of type III (2HDM-III) has the potential to address the R D (*) anomalies while the resolution to the R K (*) deficits requires new degrees of freedom within this framework, we consider in this paper a unified scenario where the low-scale type-I seesaw mechanism is embedded into the 2HDM-III, so as to accommodate the R D (*) and R K (*) anomalies as well as the neutrino mass. We first revisit the R D (*) anomalies and find that the current world-averaged results can be addressed at 2σ level without violating the bound from the branching ratio B(B − c → τ −ν) 30%. The scenario predicts two sub-eV neutrino masses based on a decoupled heavy Majorana neutrino and two nearly degenerate Majorana neutrinos with mass around the electroweak scale. For the R K (*) anomalies, the same scenario can generate the required Wilson coefficients in the direction C NP 9µ = −C NP 10µ < 0, with O(1) Yukawa couplings for the muon and the top quark.

Using e + e − collision data corresponding to a total integrated luminosity of 12.9 fb −1 collected with the BESIII detector at the BEPCII collider, the exclusive Born cross sections and the effective form factors of the reaction e + e − → Ξ − Ξ+ are measured via the single baryon-tag method at 23 center-of-mass energies between 3.510 and 4.843 GeV. Evidence for the decay ψ(3770) → Ξ − Ξ+ is observed with a significance of 4.5σ by analyzing the measured cross sections together with earlier BESIII results. For the other charmonium(-like) states ψ(4040), ψ(4160), Y (4230), Y (4360), ψ(4415), and Y (4660), no significant signal of their decay to Ξ − Ξ+ is found. For these states, upper limits of the products of the branching fraction and the electronic partial width at the 90% confidence level are provided.