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Using (2712.4±14.3)×106 ψ(3686) events collected with the BESIII detector operating at the BEPCII collider, we search for the hadronic transition hc→π+π−J/ψ via ψ(3686)→π0hc. No significant signal is observed. We set the most stringent upper limits to date on the branching fractions B(ψ(3686)→π0hc)×B(hc→π+π−J/ψ) and B(hc→π+π−J/ψ) at the 90% confidence level, which are determined to be 6.7×10−7 and 9.4×10−4, respectively.
The process 𝑒+𝑒−→Σ+¯Σ− is studied from threshold up to 3.04 GeV/𝑐2 via the initial-state radiation technique using data with an integrated luminosity of 12.0 fb−1, collected at center-of-mass energies between 3.773 and 4.258 GeV with the BESIII detector at the BEPCII collider. The pair production cross sections and the effective form factors of Σ are measured in eleven Σ+¯Σ− invariant mass intervals from threshold to 3.04 GeV/𝑐2. The results are consistent with the previous results from Belle and BESIII. Furthermore, the branching fractions of the decays 𝐽/𝜓→Σ+¯Σ− and 𝜓(3686)→Σ+¯Σ− are determined and the obtained results are consistent with the previous results of BESIII.
The process e+e−→Σ+Σ¯− is studied from threshold up to 3.04 GeV/c2 via the initial-state radiation technique using data with an integrated luminosity of 12.0 fb−1, collected at center-of-mass energies between 3.773 and 4.258 GeV with the BESIII detector at the BEPCII collider. The pair production cross sections and the effective form factors of Σ are measured in eleven Σ+Σ¯− invariant mass intervals from threshold to 3.04 GeV/c2. The results are consistent with the previous results from Belle and BESIII. Furthermore, the branching fractions of the decays J/ψ→Σ+Σ¯− and ψ(3686)→Σ+Σ¯− are determined and the obtained results are consistent with the previous results of BESIII.
Using e+e− collision data collected with the BESIII detector operating at the BEPCII collider, the Born cross sections of e+e−→Λ+cΛ¯c(2595)−+c.c. and e+e−→Λ+cΛ¯c(2625)−+c.c. are measured for the first time at center-of-mass energies of s√=4918.0 and 4950.9 MeV. Non-zero cross sections are observed very close to the production threshold. The measured Born cross sections of e+e−→Λ+cΛ¯c(2625)−+c.c. are about 2∼3 times greater than those of e+e−→Λ+cΛ¯c(2595)−+c.c., thereby indicating that the exotic structure potentially exists in the excited charmed baryons. The Born cross sections are 15.6±3.1±0.9 pb and 29.4±3.7±2.7 pb for e+e−→Λ+cΛ¯c(2595)−+c.c., and are 43.4±4.0±4.1 pb and 76.8±6.5±4.2 pb for e+e−→Λ+cΛ¯c(2625)−+c.c. at s√=4918.0 and 4950.9 MeV, respectively. Based on the polar angle distributions of the Λ¯c(2625)− and Λc(2625)+, the form-factor ratios |GE|2+3|GM|2−−−−−−−−−−−−√/|GC| are determined for e+e−→Λ+cΛ¯c(2625)−+c.c. for the first time, which are 5.95±4.07±0.15 and 0.94±0.32±0.02 at s√=4918.0 and 4950.9 MeV, respectively. All of these first uncertainties are statistical and second systematic.
Using e+e− collision data collected with the BESIII detector operating at the BEPCII collider, the Born cross sections of e+e−→Λ+cΛ¯c(2595)−+c.c. and e+e−→Λ+cΛ¯c(2625)−+c.c. are measured for the first time at center-of-mass energies of s√=4918.0 and 4950.9 MeV. Non-zero cross sections are observed very close to the production threshold. The measured Born cross sections of e+e−→Λ+cΛ¯c(2625)−+c.c. are about 2∼3 times greater than those of e+e−→Λ+cΛ¯c(2595)−+c.c., thereby indicating that the exotic structure potentially exists in the excited charmed baryons. The Born cross sections are 15.6±3.1±0.9 pb and 29.4±3.7±2.7 pb for e+e−→Λ+cΛ¯c(2595)−+c.c., and are 43.4±4.0±4.1 pb and 76.8±6.5±4.2 pb for e+e−→Λ+cΛ¯c(2625)−+c.c. at s√=4918.0 and 4950.9 MeV, respectively. Based on the polar angle distributions of the Λ¯c(2625)− and Λc(2625)+, the form-factor ratios |GE|2+3|GM|2−−−−−−−−−−−−√/|GC| are determined for e+e−→Λ+cΛ¯c(2625)−+c.c. for the first time, which are 5.95±4.07±0.15 and 0.94±0.32±0.02 at s√=4918.0 and 4950.9 MeV, respectively. All of these first uncertainties are statistical and second systematic.
Using e+e− collision data collected with the BESIII detector operating at the BEPCII collider, the Born cross sections of e+e−→Λ+cΛ¯c(2595)−+c.c. and e+e−→Λ+cΛ¯c(2625)−+c.c. are measured for the first time at center-of-mass energies of s√=4918.0 and 4950.9 MeV. Non-zero cross sections are observed very close to the production threshold. The measured Born cross sections of e+e−→Λ+cΛ¯c(2625)−+c.c. are about 2∼3 times greater than those of e+e−→Λ+cΛ¯c(2595)−+c.c., thereby indicating that the exotic structure potentially exists in the excited charmed baryons. The Born cross sections are 15.6±3.1±0.9 pb and 29.4±3.7±2.7 pb for e+e−→Λ+cΛ¯c(2595)−+c.c., and are 43.4±4.0±4.1 pb and 76.8±6.5±4.2 pb for e+e−→Λ+cΛ¯c(2625)−+c.c. at s√=4918.0 and 4950.9 MeV, respectively. Based on the polar angle distributions of the Λ¯c(2625)− and Λc(2625)+, the form-factor ratios |GE|2+3|GM|2−−−−−−−−−−−−√/|GC| are determined for e+e−→Λ+cΛ¯c(2625)−+c.c. for the first time, which are 5.95±4.07±0.15 and 0.94±0.32±0.02 at s√=4918.0 and 4950.9 MeV, respectively. All of these first uncertainties are statistical and second systematic.
Using 𝑒+𝑒− collision data with an integrated luminosity of 7.33 fb−1 collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector operating at the BEPCII collider, the branching fraction of the leptonic decay 𝐷+ 𝑠→𝜇+𝜈𝜇 is measured to be (0.5294±0.0108stat±0.0085syst)%. Based on this, the product of the 𝐷+ 𝑠 decay constant 𝑓𝐷+ 𝑠 and the magnitude of the 𝑐→𝑠 quark mixing matrix element |𝑉𝑐𝑠| is determined to be 𝑓𝐷+ 𝑠|𝑉𝑐𝑠| = 241.8±2.5stat±2.2syst MeV. Using the value of |𝑉𝑐𝑠| given by the global standard model fit, 𝑓𝐷+ 𝑠 is found to be 248.4±2.5stat±2.2syst MeV. Alternatively, using the value of 𝑓𝐷+ 𝑠 from a recent lattice quantum chromodynamics calculation, |𝑉𝑐𝑠| is determined to be 0.968±0.010stat±0.009syst.
Using 2.93 fb−1 of e+e− collision data collected with the BESIII detector at the center-of-mass energy of 3.773 GeV, we investigate the semileptonic decays D+→π+π−ℓ+νℓ (ℓ=e and μ). The D+→f0(500)μ+νμ decay is observed for the first time. By analyzing simultaneously the differential decay rates of D+→f0(500)μ+νμ and D+→f0(500)e+νe in different ℓ+νℓ four-momentum transfer intervals, the product of the relevant hadronic form factor ff0+(0) and the magnitude of the c→d Cabibbo-Kobayashi-Maskawa matrix element |Vcd| is determined to be ff0+(0)|Vcd|=0.0787±0.0060stat±0.0033syst for the first time. With the input of |Vcd| from the global fit in the standard model, we determine ff0+(0)=0.350±0.027stat±0.015syst. The absolute branching fractions of D+→f0(500)(π+π−)μ+νμ and D+→ρ0(π+π−)μ+νμ are determined as (0.72±0.13stat±0.10syst)×10−3 and (1.64±0.13stat±0.11syst)×10−3. Combining these results with those of previous BESIII measurements on their semielectronic counterparts from the same data sample, we test lepton flavor universality by measuring the branching fraction ratios BD+→ρ0μ+νμ/BD+→ρ0e+νe = 0.88±0.10 and BD+→f0(500)μ+νμ/BD+→f0(500)e+νe = 1.14±0.28, which are compatible with the standard model expectation.
Using 2.93 fb−1 of e+e− collision data collected with the BESIII detector at the center-of-mass energy of 3.773 GeV, we investigate the semileptonic decays D+→π+π−ℓ+νℓ (ℓ=e and μ). The D+→f0(500)μ+νμ decay is observed for the first time. By analyzing simultaneously the differential decay rates of D+→f0(500)μ+νμ and D+→f0(500)e+νe in different ℓ+νℓ four-momentum transfer intervals, the product of the relevant hadronic form factor ff0+(0) and the magnitude of the c→d Cabibbo-Kobayashi-Maskawa matrix element |Vcd| is determined to be ff0+(0)|Vcd|=0.0787±0.0060stat±0.0033syst for the first time. With the input of |Vcd| from the global fit in the standard model, we determine ff0+(0)=0.350±0.027stat±0.015syst. The absolute branching fractions of D+→f0(500)(π+π−)μ+νμ and D+→ρ0(π+π−)μ+νμ are determined as (0.72±0.13stat±0.10syst)×10−3 and (1.64±0.13stat±0.11syst)×10−3. Combining these results with those of previous BESIII measurements on their semielectronic counterparts from the same data sample, we test lepton flavor universality by measuring the branching fraction ratios BD+→ρ0μ+νμ/BD+→ρ0e+νe=0.88±0.10 and BD+→f0(500)μ+νμ/BD+→f0(500)e+νe = 1.14±0.28, which are compatible with the standard model expectation.
Precision measurements of the semileptonic decays 𝐷+𝑠→𝜂𝑒+𝜈𝑒 and 𝐷+𝑠→𝜂′𝑒+𝜈𝑒 are performed with 7.33 fb−1 of 𝑒+𝑒− collision data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector. The branching fractions obtained are ℬ(𝐷+𝑠→𝜂𝑒+𝜈𝑒) = (2.255±0.039stat±0.051syst)% and ℬ(𝐷+𝑠→𝜂′𝑒+𝜈𝑒)=(0.810±0.038stat±0.024syst)%. Combining these results with the ℬ(𝐷+→𝜂𝑒+𝜈𝑒) and ℬ(𝐷+→𝜂′𝑒+𝜈𝑒) obtained from previous BESIII measurements, the 𝜂−𝜂′ mixing angle in the quark flavor basis is determined to be 𝜙P=(40.0±2.0stat±0.6syst)°. Moreover, from the fits to the partial decay rates of 𝐷+𝑠→𝜂𝑒+𝜈𝑒 and 𝐷+𝑠→𝜂′𝑒+𝜈𝑒, the products of the hadronic transition form factors 𝑓𝜂(′)+(0) and the modulus of the 𝑐→𝑠 Cabibbo-Kobayashi-Maskawa matrix element |𝑉𝑐𝑠| are determined by using different hadronic transition form factor parametrizations. Based on the two-parameter series expansion, the products 𝑓𝜂+(0)|𝑉𝑐𝑠| = 0.4519±0.0071stat±0.0065syst and 𝑓𝜂′+(0)|𝑉𝑐𝑠| = 0.525±0.024stat±0.009syst are extracted. All results determined in this work supersede those measured in the previous BESIII analyses based on the 3.19 fb−1 subsample of data at 4.178 GeV.
