We present the first search for the rare decay of η′ into K±π in J/ψ→φη′, using a sample of 1.3×109 J/ψ events collected with the BESIII detector. No significant signal is observed, and the upper limit at the 90% confidence level for the ratio B(η′→K±π)B(η′→γπ+π-) is determined to be 1.3×10-4. In addition, we report the measurement of the branching fraction of J/ψ→φη′ to be [5.10±0.03(stat)±0.32(syst)]×10-4, which agrees with previous results from BESII.

A neutral structure in the DD[over ¯]^{*} system around the DD[over ¯]^{*} mass threshold is observed with a statistical significance greater than 10σ in the processes e^{+}e^{-}→D^{+}D^{*-}π^{0}+c.c. and e^{+}e^{-}→D^{0}D[over ¯]^{*0}π^{0}+c.c. at sqrt[s]=4.226 and 4.257 GeV in the BESIII experiment. The structure is denoted as Z_{c}(3885)^{0}. Assuming the presence of a resonance, its pole mass and width are determined to be [3885.7_{-5.7}^{+4.3}(stat)±8.4(syst)]  MeV/c^{2} and [35_{-12}^{+11}(stat)±15(syst)]  MeV, respectively. The Born cross sections are measured to be σ[e^{+}e^{-}→Z_{c}(3885)^{0}π^{0},Z_{c}(3885)^{0}→DD[over ¯]^{*}]=[77±13(stat)±17(syst)]  pb at 4.226 GeV and [47±9(stat)±10(syst)]  pb at 4.257 GeV. The ratio of decay rates B[Z_{c}(3885)^{0}→D^{+}D^{*-}+c.c.]/B[Z_{c}(3885)^{0}→D^{0}D[over ¯]^{*0}+c.c.] is determined to be 0.96±0.18(stat)±0.12(syst), consistent with no isospin violation in the process, Z_{c}(3885)^{0}→DD[over ¯]^{*}.

In an analysis of a 2.92 fb-1 data sample taken at 3.773 GeV with the BESIII detector operated at the BEPCII collider, we measure the absolute decay branching fractions B(D0→K-e+νe)=(3.505±0.014±0.033)% and B(D0→π-e+νe)=(0.295±0.004±0.003)%. From a study of the differential decay rates we obtain the products of hadronic form factor and the magnitude of the Cabibbo-Kobayashi- Maskawa (CKM) matrix element f+K(0)|Vcs|=0.7172±0.0025±0.0035 and f+π(0)|Vcd|=0.1435±0.0018±0.0009. Combining these products with the values of |Vcs(d)| from the SM constraint fit, we extract the hadronic form factors f+K(0)=0.7368±0.0026±0.0036 and f+π(0)=0.6372±0.0080±0.0044, and their ratio f+π(0)/f+K(0)=0.8649±0.0112±0.0073. These form factors and their ratio are used to test unquenched lattice QCD calculations of the form factors and a light cone sum rule (LCSR) calculation of their ratio. The measured value of f+K(π)(0)|Vcs(d)| and the lattice QCD value for f+K(π)(0) are used to extract values of the CKM matrix elements of |Vcs|=0.9601±0.0033±0.0047±0.0239 and |Vcd|=0.2155±0.0027±0.0014±0.0094, where the third errors are due to the uncertainties in lattice QCD calculations of the form factors. Using the LCSR value for f+π(0)/f+K(0), we determine the ratio |Vcd|/|Vcs|=0.238±0.004±0.002±0.011, where the third error is from the uncertainty in the LCSR normalization. In addition, we measure form factor parameters for three different theoretical models that describe the weak hadronic charged currents for these two semileptonic decays. All of these measurements are the most precise to date.

We extract the e+e-→π+π- cross section in the energy range between 600 and 900 MeV, exploiting the method of initial state radiation. A data set with an integrated luminosity of 2.93 fb-1 taken at a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider is used. The cross section is measured with a systematic uncertainty of 0.9%. We extract the pion form factor |Fπ|2 as well as the contribution of the measured cross section to the leading-order hadronic vacuum polarization contribution to (g-2)μ. We find this value to be aμππ,LO(600-900MeV)=(368.2±2.5stat±3.3sys)10-10, which is between the corresponding values using the BaBar or KLOE data.

We present a measurement of the azimuthal asymmetries of two charged pions in the inclusive process e^{+}e^{-}→ππX, based on a data set of 62  pb^{-1} at the center-of-mass energy of 3.65 GeV collected with the BESIII detector. These asymmetries can be attributed to the Collins fragmentation function. We observe a nonzero asymmetry, which increases with increasing pion momentum. As our energy scale is close to that of the existing semi-inclusive deep inelastic scattering experimental data, the measured asymmetries are important inputs for the global analysis of extracting the quark transversity distribution inside the nucleon and are valuable to explore the energy evolution of the spin-dependent fragmentation function.

© 2015 American Physical Society. Based on a sample of η′ mesons produced in the radiative decay J/ψ→γη′ in 1.31×109J/ψ events collected with the BESIII detector, the decay η′→ωe+e- is observed for the first time, with a statistical significance of 8σ. The branching fraction is measured to be B(η′→ωe+e-)=(1.97±0.34(stat)±0.17(syst))×10-4, which is in agreement with theoretical predictions. The branching fraction of η′→ωγ is also measured to be (2.55±0.03(stat)±0.16(syst))×10-2, which is the most precise measurement to date, and the relative branching fraction B(η′→ωe+e-)B(η′→ωγ) is determined to be (7.71±1.34(stat)±0.54(syst))×10-3.

We present a study of the process e+e-→π±(DD¯∗)∓ using data samples of 1092 pb-1 at s=4.23 GeV and 826 pb-1 at s=4.26 GeV collected with the BESIII detector at the BEPCII storage ring. With full reconstruction of the D meson pair and the bachelor π± in the final state, we confirm the existence of the charged structure Zc(3885)∓ in the (DD¯∗)∓ system in the two isospin processes e+e-→π+D0D∗- and e+e-→π+D-D∗0. By performing a simultaneous fit, the statistical significance of Zc(3885)∓ signal is determined to be greater than 10σ, and its pole mass and width are measured to be Mpole=(3881.7±1.6(stat)±1.6(syst)) MeV/c2 and Γpole=(26.6±2.0(stat)±2.1(syst)) MeV, respectively. The Born cross section times the (DD¯∗)∓ branching fraction (σ(e+e-→π±Zc(3885)∓)×Br(Zc(3885)∓→(DD¯∗)∓)) is measured to be (141.6±7.9(stat)±12.3(syst)) pb at s=4.23 GeV and (108.4±6.9(stat)±8.8(syst)) pb at s=4.26 GeV. The polar angular distribution of the π±-Zc(3885)∓ system is consistent with the expectation of a quantum number assignment of JP=1+ for Zc(3885)∓.

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an integrated luminosity of 3.2 fb-1 at s=13 TeV collected in 2015 with the ATLAS detector at the Large Hadron Collider. Events are required to have at least one jet with a transverse momentum above 250 GeV and no leptons. Several signal regions are considered with increasing missing-transverse-momentum requirements between ETmiss>250 GeV and ETmiss>700 GeV. Good agreement is observed between the number of events in data and Standard Model predictions. The results are translated into exclusion limits in models with large extra spatial dimensions, pair production of weakly interacting dark-matter candidates, and the production of supersymmetric particles in several compressed scenarios.