A bstract We measured the Born cross sections for the process e + e − → ωη ′ at 22 center-of-mass energies from 2.000 to 3.080 GeV with the BESIII detector at the BEPCII collider. We observed a ...resonant structure with a statistical significance of 9.6 σ . A Breit-Wigner fit determines its mass to be M R = (2153 ± 30 ± 31) MeV /c 2 and its width to be Γ R = (167 ± 77 ± 7) MeV, where the first uncertainties are statistical and the second are systematic.
Using a sample of 4.3 x 105 eta' -> eta pi 0 pi 0 events selected from the ten billion J=psi event dataset collected with the BESIII detector, we study the decay eta' -> eta pi 0 pi 0 within ...the framework of nonrelativistic effective field theory. Evidence for a structure at pi+pi- mass threshold is observed in the invariant mass spectrum of pi 0 pi 0 with a statistical significance of around 3.5 sigma, which is consistent with the cusp effect as predicted by the nonrelativistic effective field theory. After introducing the amplitude for describing the cusp effect, the pi pi scattering length combination a0 - a2 is determined to be 0.226 10.060stat 10.013syst, which is in good agreement with theoretical calculation of 0.2644 10.0051.
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”.
Based on e+e- collision data corresponding to an integrated luminosity of 4.5 fb-1 collected at the center-of-mass energies between 4.600 and 4.699 GeV with the BESIII detector at BEPCII, the ...absolute branching fraction of the inclusive decay over bar ? - c & RARR; n over bar + X, where X refers to any possible final state particles, is measured. The absolute branching fraction is determined to be B( over bar ?-c & RARR; n over bar + X) = (32.4 + 0.7 + 1.5)%, where the first uncertainty is statistical and the second systematic. Assuming CP symmetry, the measurement indicates that about one fourth of ?+ c ( over bar ?-c) decay modes with a neutron (an antineutron) in the final state have not been observed.
Study of η′ → π+π−l+l− decays at BESIII Ai, X. C.; Bakina, O.; Balossino, I. ...
The journal of high energy physics,
16/7, Volume:
2024, Issue:
7
Journal Article
Peer reviewed
Open access
A
bstract
With a sample of (10087
±
44)
×
10
6
J/ψ
events accumulated with the BESIII detector, we analyze the decays
η
′
→ π
+
π
−
l
+
l
−
(
l
=
e, μ
) via the process
J/ψ → γη
′. The branching ...fractions are measured to be
B
(
η
′
→ π
+
π
−
e
+
e
−
) = (2
.
45
±
0
.
02(stat
.
)
±
0
.
08(syst
.
))
×
10
−
3
and
B
(
η
′
→ π
+
π
−
μ
+
μ
−
) = (2
.
16
±
0
.
12(stat
.
)
±
0
.
06(syst
.
))
×
10
−
5
, and the ratio is
B
η
′
→
π
+
π
−
e
+
e
−
B
η
′
→
π
+
π
−
μ
+
μ
−
=
113.4
±
0.9
stat
.
±
3.7
syst
.
. In addition, by combining the
η
′ →
π
+
π
−
e
+
e
−
and
η
′ →
π
+
π
−
μ
+
μ
−
decays, the slope parameter of the electromagnetic transition form factor is measured to be
b
η
′
= 1.30 ± 0.19 (GeV
/c
2
)
−
2
, which is consistent with previous measurements from BESIII and theoretical predictions from the VMD model. The asymmetry in the angle between the
π
+
π
−
and
l
+
l
−
decay planes, which has the potential to reveal the
CP
-violation originating from an unconventional electric dipole transition, is also investigated. The asymmetry parameters are determined to be
A
CP
η
′
→
π
+
π
−
e
+
e
−
=
−
0.21
±
0.73
stat
.
±
0.01
syst
.
%
and
A
CP
η
′
→
π
+
π
−
μ
+
μ
−
=
0.62
±
4.71
stat
.
±
0.08
syst
.
%
, implying that no evidence of
CP
-violation is observed at the present statistics. Finally, an axion-like particle is searched for via the decay
η
′ →
π
+
π
−
a, a
→
e
+
e
−
, and upper limits of the branching fractions are presented for the mass assumptions of the axion-like particle in the range of 0
−
500 MeV
/c
2
.
PDF
