A bstract Based on e + e − collision data collected at center-of-mass energies from 2.000 to 3.080 GeV by the BESIII detector at the BEPCII collider, a partial wave analysis is performed for the ...process e + e − → $$ {K}_S^0{K}_L^0 $$ K S 0 K L 0 π 0 . The results allow the Born cross sections of the process e + e − → $$ {K}_S^0{K}_L^0 $$ K S 0 K L 0 π 0 , as well as its subprocesses e + e − → K ∗ (892) 0 $$ \overline{K} $$ K ¯ 0 and $$ {K}_2^{\ast } $$ K 2 ∗ (1430) 0 $$ \overline{K} $$ K ¯ 0 to be measured. The Born cross sections for e + e − → $$ {K}_S^0{K}_L^0 $$ K S 0 K L 0 π 0 are consistent with previous measurements by BaBar, but with substantially improved precision. The Born cross section lineshape of the process e + e − K ∗ (892) 0 $$ \overline{K} $$ K ¯ 0 is consistent with a vector meson state around 2.2 GeV with a significance of 3.2 σ . A Breit-Wigner fit determines its mass as M Y = (2164 . 7 ± 9 . 1 ± 3 . 1) MeV /c 2 and its width as Γ Y = (32 . 4 ± 21 . 0 ± 1 . 8) MeV.
The Beijing Electron Spectrometer III (BESIII) is a multipurpose detector operating on the Beijing Electron Positron Collider II (BEPCII). After more than ten years operation, the efficiency of the ...inner layers of the Main Drift Chamber (MDC) decreased significantly. To solve this issue, the BESIII collaboration is planning to replace the inner part of the MDC with three layers of Cylindrical triple Gas Electron Multipliers (CGEM).
The transverse plane spatial resolution of CGEM is required to be 120μm or better. To meet this goal, a careful calibration of the detector is necessary to fully exploit the potential of the CGEM detector. In all the calibrations, the detector alignment plays an important role to improve the detector precision. The track-based alignment for the CGEM detector with the Millepede algorithm is implemented to reduce the uncertainties of the hit position measurement. Using the cosmic-ray data taken in 2020 with the two layers setup, the displacement and rotation of the outer layer with respect to the inner layer is determined by a simultaneous fit applied to more than 160000 tracks. A good alignment precision has been achieved that guarantees the design request could be satisfied in the future. A further alignment is going to be performed using the combined information of tracks from cosmic-ray and collisions after the CGEM is installed into the BESIII detector.
A bstract The $$ {D}_s^{+}\to {K}^{+}{K}^{-}{\mu}^{+}{\nu}_{\mu } $$ D s + → K + K − μ + ν μ decay is studied based on 7.33 fb − 1 of e + e − collision data collected with the BESIII detector at ...center-of-mass energies in the range from 4.128 to 4.226 GeV. The absolute branching fraction is measured as $$ \mathcal{B}\left({D}_s^{+}\to \phi {\mu}^{+}{\nu}_{\mu}\right)=\left(2.25\pm 0.09\pm 0.07\right)\times {10}^{-2} $$ B D s + → ϕ μ + ν μ = 2.25 ± 0.09 ± 0.07 × 10 − 2 , the most precise measurement to date. Combining with the world average of $$ \mathcal{B}\left({D}_s^{+}\to \phi {e}^{+}{\nu}_e\right) $$ B D s + → ϕ e + ν e , the ratio of the branching fractions obtained is $$ \frac{\mathcal{B}\left({D}_s^{+}\to \phi {\mu}^{+}{\nu}_{\mu}\right)}{\mathcal{B}\left({D}_s^{+}\to \phi {e}^{+}{\nu}_e\right)}=0.94\pm 0.08 $$ B D s + → ϕ μ + ν μ B D s + → ϕ e + ν e = 0.94 ± 0.08 , in agreement with lepton universality. By performing a partial wave analysis, the hadronic form factor ratios at q 2 = 0 are extracted, finding $$ {r}_V=\frac{V(0)}{A_1(0)}=1.58\pm 0.17\pm 0.02 $$ r V = V 0 A 1 0 = 1.58 ± 0.17 ± 0.02 and $$ {r}_2=\frac{A_2(0)}{A_1(0)}=0.71\pm 0.14\pm 0.02 $$ r 2 = A 2 0 A 1 0 = 0.71 ± 0.14 ± 0.02 , where the first uncertainties are statistical and the second are systematic. No significant S -wave contribution from f 0 (980) → K + K − is found. The upper limit $$ \mathcal{B}\left({D}_s^{+}\to {f}_0(980){\mu}^{+}{\nu}_{\mu}\right)\cdot \mathcal{B}\left({f}_0(980)\to {K}^{+}{K}^{-}\right)<5.45\times {10}^{-4} $$ B D s + → f 0 980 μ + ν μ ⋅ B f 0 980 → K + K − < 5.45 × 10 − 4 is set at 90% credibility level.
A bstract Using e + e − collision datasets corresponding to a total integrated luminosity of 21.7 fb − 1 collected with the BESIII detector at the BEPCII collider at center-of-mass energies ranging ...from 4.009 GeV to 4.951 GeV, the energy-dependent cross sections of $$ {e}^{+}{e}^{-}\to p{K}^{-}\overline{\Lambda}+c.c. $$ e + e − → p K − Λ ¯ + c . c . are measured for the first time. By fitting these energy-dependent cross sections, we search for the excited ψ states ψ (4160) and ψ (4415), and the vector charmonium-like states ψ (4230), ψ (4360), and ψ (4660). No evidence for these is observed and the upper limits on the branching fractions of these states decaying into $$ p{K}^{-}\overline{\Lambda}+c.c. $$ p K − Λ ¯ + c . c . are set at the 90% confidence level.
A bstract Based on 4.5 fb − 1 e + e − collision data collected with BESIII detector at seven energy points between 4.600 and 4.699 GeV, the branching fractions for $$ {\Lambda}_c^{+}\to p\eta $$ Λ c ...+ → pη and $$ {\Lambda}_c^{+}\to p\omega $$ Λ c + → pω were measured by means of single-tag method. The branching fractions of $$ {\Lambda}_c^{+}\to p\eta $$ Λ c + → pη and $$ {\Lambda}_c^{+}\to p\omega $$ Λ c + → pω are determined to be (1.57 ± 0.11 stat ± 0.04 syst ) × 10 − 3 and (1.11 ± 0.20 stat ± 0.07 syst ) × 10 − 3 , with a statistical significance of greater than 10 σ and 5.7 σ , respectively. These results are consistent with the previous measurements by BESIII, LHCb and Belle, and the result of $$ {\Lambda}_c^{+}\to p\eta $$ Λ c + → pη is the most precise to date.
A
bstract
With data samples collected with the BESIII detector at seven energy points at
$$ \sqrt{s} $$
s
= 3
.
68
−
3
.
71 GeV, corresponding to an integrated luminosity of 333 pb
−
1
, we present a ...study of the Λ transverse polarization in the
e
+
e
−
→
$$ \Lambda \overline{\Lambda} $$
Λ
Λ
¯
reaction. The significance of polarization by combining the seven energy points is found to be 2.6
σ
including the systematic uncertainty, which implies a non-zero phase between the transition amplitudes of the
$$ \Lambda \overline{\Lambda} $$
Λ
Λ
¯
helicity states. The modulus ratio and the relative phase of EM-
psionic
form factors combined with all energy points are measured to be
R
Ψ
=
$$ {0.71}_{-0.10}^{+0.10} $$
0.71
−
0.10
+
0.10
±
0.03 and ∆Φ
Ψ
=
$$ {23}_{-8.0}^{+8.8} $$
23
−
8.0
+
8.8
±
1.6
°
, where the first uncertainties are statistical and the second systematic.
A
bstract
Utilizing 7
.
33 fb
−
1
of
e
+
e
−
collision data taken at the center-of-mass energies of 4.128, 4.157, 4.178, 4.189, 4.199, 4.209, 4.219, and 4.226 GeV with the BESIII detector, the ...branching fraction of the leptonic decay
$$ {D}_s^{+} $$
D
s
+
→ τ
+
ν
τ
via
τ
+
→ μ
+
ν
μ
$$ \overline{\nu} $$
ν
¯
τ
is measured to be
$$ {\mathcal{B}}_{D_s^{+}\to {\tau}^{+}{\nu}_{\tau }} $$
B
D
s
+
→
τ
+
ν
τ
= (5
.
37
±
0
.
17
stat
±
0
.
15
syst
)%. Combining this branching fraction with the world averages of the measurements of the masses of
τ
+
and
$$ {D}_s^{+} $$
D
s
+
as well as the lifetime of
$$ {D}_s^{+} $$
D
s
+
, we extract the product of the decay constant of
$$ {D}_s^{+} $$
D
s
+
and the
c → s
Cabibbo-Kobayashi-Maskawa matrix element to be
$$ {f}_{D_s^{+}} $$
f
D
s
+
|V
cs
|
= (246
.
7
±
3
.
9
stat
±
3
.
6
syst
) MeV. Taking
|V
cs
|
from a global fit in the standard model we obtain
$$ {f}_{D_s^{+}} $$
f
D
s
+
= (253
.
4
±
4
.
0
stat
±
3
.
7
syst
) MeV. Conversely, taking
$$ {f}_{D_s^{+}} $$
f
D
s
+
from lattice quantum chromodynamics calculations, we obtain
|V
cs
|
= 0
.
987
±
0
.
016
stat
±
0
.
014
syst
.
A
bstract
Based on 4.5 fb
−
1
data taken at seven center-of-mass energies ranging from 4.600 to 4.699 GeV with the BESIII detector at the BEPCII collider, we measure the branching fractions of
$$ ...{\Lambda}_c^{+} $$
Λ
c
+
→
Σ
+
+
hadrons
relative to
$$ {\Lambda}_c^{+} $$
Λ
c
+
→
Σ
+
π
+
π
−
. Combining with the world average branching fraction of
$$ {\Lambda}_c^{+} $$
Λ
c
+
→
Σ
+
π
+
π
−
, their branching fractions are measured to be (0
.
377
±
0
.
042
±
0
.
020
±
0
.
021)% for
$$ {\Lambda}_c^{+} $$
Λ
c
+
→
Σ
+
K
+
K
−
, (0
.
200
±
0
.
023
±
0
.
011
±
0
.
011)% for
$$ {\Lambda}_c^{+} $$
Λ
c
+
→
Σ
+
K
+
π
−
, (0
.
414
±
0
.
080
±
0
.
030
±
0
.
023)% for
$$ {\Lambda}_c^{+} $$
Λ
c
+
→
Σ
+
ϕ
and (0
.
197
±
0
.
036
±
0
.
009
±
0
.
011)% for
$$ {\Lambda}_c^{+} $$
Λ
c
+
→ Σ
+
K
+
K
−
(non-
ϕ
). In all the above results, the first uncertainties are statistical, the second are systematic and the third are from external input of the branching fraction of
$$ {\Lambda}_c^{+} $$
Λ
c
+
→
Σ
+
π
+
π
−
. Since no signal for
$$ {\Lambda}_c^{+} $$
Λ
c
+
→
Σ
+
K
+
π
−
π
0
is observed, the upper limit of its branching fraction is determined to be 0.13% at the 90% confidence level.
A
bstract
Using 2.93 fb
−
1
of
e
+
e
−
collision data collected with the BESIII detector at the center-of-mass energy 3.773 GeV, we perform the first amplitude analysis of the decay
D
+
→
$$ {K}_S^0 ...$$
K
S
0
π
+
π
0
π
0
and determine the relative magnitudes and phases of different intermediate processes. The absolute branching fraction of
D
+
→
$$ {K}_S^0 $$
K
S
0
π
+
π
0
π
0
is measured to be (2.888
±
0.058
stat
.
±
0.069
syst
.
)%. The dominant intermediate processes are
D
+
→
$$ {K}_S^0 $$
K
S
0
a
1
(1260)
+
(
→ ρ
+
π
0
) and
D
+
→
$$ \overline{K} $$
K
¯
*0
ρ
+
, with branching fractions of (8.66
±
1.04
stat
.
±
1.39
syst
.
)
×
10
−
3
and (9.70
±
0.81
stat
.
±
0.53
syst
.
)
×
10
−
3
, respectively.
