Based on a sample of (1310.6±7.0)×10^{6}J/ψ events collected with the BESIII detector, we present measurements of J/ψ and η^{'} absolute branching fractions using the process J/ψ→γη^{'}. By analyzing ...events where the radiative photon converts into an e^{+}e^{-} pair, the branching fraction for J/ψ→γη^{'} is measured to be (5.27±0.03±0.05)×10^{-3}. The absolute branching fractions of the five dominant decay channels of the η^{'} are then measured for the first time and are determined to be B(η^{'}→γπ^{+}π^{-})=(29.90±0.03±0.55)%, B(η^{'}→ηπ^{+}π^{-})=(41.24±0.08±1.24)%, B(η^{'}→ηπ^{0}π^{0})=(21.36±0.10±0.92)%, B(η^{'}→γω)=(2.489±0.018±0.074)%, and B(η^{'}→γγ)=(2.331±0.012±0.035)%, where the first uncertainties are statistical and the second systematic.
We report a measurement of the observed cross sections of e+e−→ J / ψ X based on 3.21 fb−1 of data accumulated at energies from 3.645 to 3.891 GeV with the BESIII detector operated at the BEPCII ...collider. In analysis of the cross sections, we measured the decay branching fractions of B ( ψ ( 3686 ) → J / ψ X ) = ( 64.4 ± 0.6 ± 1.6 ) % and B ( ψ ( 3770 ) → J / ψ X ) = ( 0.5 ± 0.2 ± 0.1 ) % for the first time. The energy-dependent line shape of these cross sections cannot be well described by two Breit-Wigner (BW) amplitudes of the expected decays ψ ( 3686 ) → J / ψ X and ψ ( 3770 ) → J / ψ X . Instead, it can be better described with one more BW amplitude of the decay R ( 3760 ) → J / ψ X . Under this assumption, we extracted the R ( 3760 ) mass MR(3760) = 3766.2 ± 3.8 ± 0.4 MeV / c2 , total width ΓR(3760)tot= 22.2 ± 5.9 ± 1.4 MeV , and product of leptonic width and decay branching fraction ΓR(3760)eeB R(3760) → J / ψ X = ( 79.4 ± 85.5 ± 11.7 ) eV . The significance of the R ( 3760 ) is 5.3 σ . The first uncertainties of these measured quantities are from fits to the cross sections and second systematic.
We report the measurement of the inclusive cross sections for e^{+}e^{-}→nOCH (where nOCH denotes non-open charm hadrons) with improved precision at center-of-mass (c.m.) energies from 3.645 to ...3.871 GeV. We observe three resonances: R(3760), R(3780), and R(3810) with significances of 8.1σ, 13.7σ, and 8.8σ, respectively. The R(3810) state is observed for the first time, while the R(3760) and R(3780) states are observed for the first time in the nOCH cross sections. Two sets of resonance parameters describe the energy-dependent line shape of the cross sections well. In set I set II, the R(3810) state has mass (3805.7±1.1±2.7) (3805.7±1.1±2.7) MeV/c^{2}, total width (11.6±2.9±1.9) (11.5±2.8±1.9) MeV, and an electronic width multiplied by the nOCH decay branching fraction of (10.9±3.8±2.5) (11.0±3.4±2.5) eV. In addition, we measure the branching fractions BR(3760)→nOCH=(25.2±16.1±30.4)%(6.4±4.8±7.7)% and BR(3780)→nOCH=(12.3±6.6±8.3)%(10.4±4.8±7.0)% for the first time. The R(3760) state can be interpreted as an open-charm (OC) molecular state, but containing a simple four-quark state component. The R(3810) state can be interpreted as a hadrocharmonium state.
Using (10087±44)×10^{6} J/ψ events collected with the BESIII detector, numerous Ξ^{-} and Λ decay asymmetry parameters are simultaneously determined from the process J/ψ→Ξ^{-}Ξover ...¯^{+}→Λ(pπ^{-})π^{-}Λover ¯(nover ¯π^{0})π^{+} and its charge-conjugate channel. The precisions of α_{Λ0} for Λ→nπ^{0} and αover ¯_{Λ0} for Λover ¯→nover ¯π^{0} compared to world averages are improved by factors of 4 and 1.7, respectively. The ratio of decay asymmetry parameters of Λ→nπ^{0} to that of Λ→pπ^{-}, ⟨α_{Λ0}⟩/⟨α_{Λ-}⟩, is determined to be 0.873±0.012_{-0.010}^{+0.011}, where the first and the second uncertainties are statistical and systematic, respectively. The ratio is smaller than unity more than 5σ, which signifies the existence of the ΔI=3/2 transition in Λ for the first time. Besides, we test for CP symmetry in Ξ^{-}→Λπ^{-} and in Λ→nπ^{0} with the best precision to date.
Based on data samples collected with the BESIII detector at the BEPCII collider, the process e^{+}e^{-}→Σ^{+}Σover ¯^{-} is studied at center-of-mass energies sqrts=2.3960, 2.6454, and 2.9000 GeV. ...Using a fully differential angular description of the final state particles, both the relative magnitude and phase information of the Σ^{+} electromagnetic form factors in the timelike region are extracted. The relative phase between the electric and magnetic form factors is determined to be sinΔΦ=-0.67±0.29(stat)±0.18(syst) at sqrts=2.3960 GeV, ΔΦ=55°±19°(stat)±14°(syst) at sqrts=2.6454 GeV, and 78°±22°(stat)±9°(syst) at sqrts=2.9000 GeV. For the first time, the phase of the hyperon electromagnetic form factors is explored in a wide range of four-momentum transfer. The evolution of the phase along with four-momentum transfer is an important input for understanding its asymptotic behavior and the dynamics of baryons.
A
bstract
Using 1310
.
6 × 10
6
J/ψ
and 448
.
1 × 10
6
ψ
(3686) events collected with the BESIII detector, the branching fractions of
J/ψ
decays to Σ
+
Σ
¯
−
is measured to be (10
.
61 ± 0
.
04 ± 0
.
...36) × 10
−
4
, which is significantly more precise than the current world average. The branching fractions of
ψ
(3686) decays to Σ
+
Σ
¯
−
is measured to be (2
.
52 ± 0
.
04 ± 0
.
09) × 10
−
4
, which is consistent with the previous measurements. In addition, the ratio of
B
(
ψ
(3686) → Σ
+
Σ
¯
−
)
/
B
(
J/ψ
→ Σ
+
Σ
¯
−
) is determined to be (23
.
8 ± 1
.
1)% which violates the “12% rule”.
A
bstract
By using 6.32 fb
−
1
of data collected with the BESIII detector at center-of-mass energies between 4.178 and 4.226 GeV, we perform an amplitude analysis of the decay
D
s
+
→
K
S
0
π
+
π
0
...and determine the relative fractions and phase differences of different intermediate processes, which include
K
S
0
ρ
(770)
+
,
K
S
0
ρ
(1450)
+
,
K
*
(892)
0
π
+
,
K
*
(892)
+
π
0
, and
K
*
(1410)
0
π
+
. With the detection efficiency based on the amplitude analysis results, the absolute branching fraction is measured to be
ℬ
D
s
+
→
K
S
0
π
+
π
0
=
5.43
±
0.30
stat
±
0.15
syst
×
10
−
3
.
The singly Cabibbo-suppressed decay Lambda(+)(c) -> n pi(+) e is observed for the first time with a statistical significance of 7.3 sigma by using 3.9 fb(-1) of e(+)e(-) collision data collected ...at center-of-mass energies between 4.612 and 4.699 GeV with the BESIII detector at BEPCII. The branching fraction of Lambda(+)(c) -> n pi(+) is measured to be (6.6 +/- 1.2(stat) 0.4(syst)) x 10(-4). By taking the upper limit of branching fractions of Lambda(+)(c) -> n pi(+) from the Belle experiment, the ratio of branching fractions between Lambda(+)(c) -> n pi(+) and Lambda(+)(c) -> p pi(0) is calculated to be larger than 7.2 at the 90% confidence level, which disagrees with most predictions of the available phenomenological models. In addition, the branching fractions of the Cabibbo-favored decays Lambda(+)(c) -> Lambda pi(+) and Lambda(+)(c)-> Sigma(0)(pi+) are measured to be (1.31 +/- 0.08(stat) +/- 0.05(syst)) x 10(-2) and (1.22 +/- 0.08(stat) +/- 0.07(syst)) x 10(-2), respectively, which are consistent with previous results.
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