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A novel soft decision-based median subtraction filter is presented for clutter suppression and infrared (IR) point targets enhancement. The decision is made based on a jump Markov model and its state and parameter estimation using a particle filter. The scheme is compared with other conventional clutter background removal techniques and good results are obtained.

The decay D→K-π+ is studied in a sample of quantum-correlated DD¯ pairs, based on a data set corresponding to an integrated luminosity of 2.93 fb-1 collected at the ψ(3770) resonance by the BESIII experiment. The asymmetry between CP-odd and CP-even eigenstate decays into K-π+ is determined to be AKπ=0.132±0.011±0.007, where the first uncertainty is statistical and the second is systematic. This measurement is an update of an earlier study exploiting additional tagging modes, including several decay modes involving a KL0 meson. The branching fractions of the KL0 modes are determined as input to the analysis in a manner that is independent of any strong phase uncertainty. Using the predominantly CP-even tag D→π+π-π0 and the ensemble of CP-odd eigenstate tags, the observable AKππππ0 is measured to be 0.130±0.012±0.008. The two asymmetries are sensitive to rDKπcosδDKπ, where rDKπ and δDKπ are the ratio of amplitudes and phase difference, respectively, between the doubly Cabibbo-suppressed and Cabibbo-favoured decays. In addition, events containing D→K-π+ tagged by D→KS,L0π+π- are studied in bins of phase space of the three-body decays. This analysis has sensitivity to both rDKπcosδDKπ and rDKπsinδDKπ. A fit to AKπ, AKππππ0 and the phase-space distribution of the D→KS,L0π+π- tags yields δDKπ=187.6-9.7+8.9-6.4+5.4∘, where external constraints are applied for rDKπ and other relevant parameters. This is the most precise measurement of δDKπ in quantum-correlated DD¯ decays.

A bstract Using a sample of (10 . 09 ± 0 . 04) × 10 9 J/ψ decays collected with the BESIII detector, partial wave analyses of the decay J / ψ → γ K S 0 K S 0 π 0 are performed within the K S 0 K S 0 π 0 invariant mass region below 1.6 GeV/ c 2 . The covariant tensor amplitude method is used in both mass independent and mass dependent approaches. Both analysis approaches exhibit dominant pseudoscalar and axial vector components, and show good consistency for the other individual components. Furthermore, the mass dependent analysis reveals that the K S 0 K S 0 π 0 invariant mass spectrum for the pseudoscalar component can be well described with two isoscalar resonant states using relativistic Breit-Wigner model, i.e., the η (1405) with a mass of 1391.7 ± 0.7 − 0.3 + 11.3 MeV/ c 2 and a width of 60.8 ± 1.2 − 12.0 + 5.5 MeV, and the η (1475) with a mass of 1507.6 ± 1.6 − 32.2 + 15.5 MeV/ c 2 and a width of 115.8 ± 2.4 − 10.9 + 14.8 MeV. The first and second uncertainties are statistical and systematic, respectively. Alternate models for the pseudoscalar component are also tested, but the description of the K S 0 K S 0 π 0 invariant mass spectrum deteriorates significantly.

A bstract Using 6 . 32 fb − 1 of e + e − collision data collected at the center-of-mass energies between 4.178 and 4.226 GeV with the BESIII detector, we perform an amplitude analysis of the decay D s + → K + π + π − and determine the amplitudes of the various intermediate states. The absolute branching fraction of D s + → K + π + π − is measured to be (6 . 11 ± 0 . 18 stat . ± 0 . 11 syst . ) × 10 − 3 . The branching fractions of the dominant intermediate processes D s + → K + ρ 0 , ρ 0 → π + π − and D s + → K * (892) 0 π + , K * (892) 0 → K + π − are determined to be (1 . 96 ± 0 . 19 stat . ± 0 . 23 syst . ) × 10 − 3 and (1 . 85 ± 0 . 12 stat . ± 0 . 13 syst . ) × 10 − 3 , respectively. The intermediate resonances f 0 (500), f 0 (980), and f 0 (1370) are observed for the first time in this channel.

A bstract A partial wave analysis on the process e + e − → ωπ + π − is performed using 647 pb − 1 of data sample collected by using the BESIII detector operating at the BEPCII storage ring at center-of-mass (c.m.) energies from 2.000 GeV to 3.080 GeV. The Born cross section of the e + e − → ωπ + π − process is measured, with precision improved by a factor of 3 compared to that of previous studies. A structure near 2.25 GeV is observed in the energy-dependent cross sections of e + e − → ωπ + π − and ωπ 0 π 0 with a statistical significance of 7.6 σ , and its determined mass and width are 2232 ± 19 ± 27 MeV /c 2 and 93 ± 53 ± 20 MeV, respectively, where the first and second uncertainties are statistical and systematic, respectively. By analyzing the cross sections of subprocesses e + e − → ωf 0 (500), ωf 0 (980), ωf 0 (1370), ωf 2 (1270), and b 1 (1235) π , a structure, with mass M = 2200 ± 11 ± 17 MeV/ c 2 and width Γ = 74 ± 20 ± 24 MeV, is observed with a combined statistical significance of 7.9 σ . The measured resonance parameters will help to reveal the nature of vector states around 2.25 GeV.

A bstract Based on e + e − collision samples corresponding to an integrated luminosity of 4.4 fb − 1 collected with the BESIII detector at center-of-mass energies between 4 . 6 GeV and 4 . 7 GeV, a partial wave analysis of the charmed baryon hadronic decay Λ c + → Λ π + π 0 is performed, and the decays Λ c + → Λ ρ (770) + and Λ c + → Σ(1385) π are studied for the first time. Making use of the world-average branching fraction B Λ c + → Λ π + π 0 , their branching fractions are determined to be B Λ c + → Λ ρ 770 + = 4.06 ± 0.30 ± 0.35 ± 0.23 × 10 − 2 , B Λ c + → Σ 1385 + π 0 = 5.86 ± 0.49 ± 0.52 ± 0.35 × 10 − 3 , B Λ c + → Σ 1385 0 π + = 6.47 ± 0.59 ± 0.66 ± 0.38 × 10 − 3 , where the first uncertainties are statistical, the second are systematic, and the third are from the uncertainties of the branching fractions B Λ c + → Λ π + π 0 and B Σ 1385 → Λ π . In addition, the decay asymmetry parameters are measured to be α Λ ρ (770)+  =  − 0.763 ± 0.053 ± 0.045, α Σ 1385 + π 0 = − 0.917 ± 0.069 ± 0.056 , and α Σ 1385 0 π + = − 0.789 ± 0.098 ± 0.056 .

A bstract The Born cross sections of the e + e − → D *+ D * − and e + e − → D *+ D − processes are measured using e + e − collision data collected with the BESIII experiment at center-of-mass energies from 4.085 to 4.600 GeV, corresponding to an integrated luminosity of 15 . 7 fb − 1 . The results are consistent with and more precise than the previous measurements by the Belle, Babar and CLEO collaborations. The measurements are essential for understanding the nature of vector charmonium and charmonium-like states.

A bstract Based on e + e − collision data collected by the BESIII detector at the BEPCII collider at center-of-mass energies from 2.000 to 3.080 GeV, a partial-wave analysis is performed for the process e + e − → K + K − π 0 . The Born cross section of the process e + e − → K + K − π 0 and its subprocesses e + e − → ϕπ 0 , K *+ (892) K − and K 2 ∗ + (1430) K − are measured. The results for e + e − → K + K − π 0 and ϕπ 0 are consistent with the BaBar measurements and with improved precision. By analyzing the cross sections of the subprocesses e + e − → K *+ (892) K − and K 2 ∗ + (1430) K − , a structure with mass M R = (2190 ± 19 ± 37) MeV/ c 2 and width Γ R = (191 ± 28 ± 60) MeV is observed with a combined statistical significance of 7.1 σ . The measured resonance parameters suggest it can be identified as the ϕ (2170), thus the results provide valuable input to understand the internal nature of this state.