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
The production of
B
±
mesons is studied in pp collisions at centre-of-mass energies of 7 and 13 TeV, using
B
±
→
J
/
ψ K
±
decays and data samples corresponding to 1.0 fb
−1
and 0.3 fb
−1
, ...respectively. The production cross-sections summed over both charges and integrated over the transverse momentum range 0 <
p
T
< 40 GeV/
c
and the rapidity range 2.0 <
y
< 4.5 are measured to be
σ
pp
→
B
±
X
,
s
=
7
T
e
V
=
43.0
±
0.2
±
2.5
±
1.7
μ
b
,
σ
pp
→
B
±
X
,
s
=
13
T
e
V
=
86.6
±
0.5
±
5.4
±
3.4
μ
b
,
where the first uncertainties are statistical, the second are systematic, and the third are due to the limited knowledge of the
B
±
→
J
/
ψ K
±
branching fraction. The ratio of the cross-section at 13 TeV to that at 7 TeV is determined to be 2.02 ± 0.02 (stat) ± 0.12 (syst). Differential cross-sections are also reported as functions of
p
T
and
y
. All results are in agreement with theoretical calculations based on the state-of-art fixed next-to-leading order quantum chromodynamics.
The process e^{+}e^{-}→D_{s}^{*+}D_{s}^{*-} is studied with a semi-inclusive method using data samples at center-of-mass energies from threshold to 4.95 GeV collected with the BESIII detector ...operating at the Beijing Electron Positron Collider. The Born cross sections of the process are measured for the first time with high precision in this energy region. Two resonance structures are observed in the energy-dependent cross sections around 4.2 and 4.4 GeV. By fitting the cross sections with a coherent sum of three Breit-Wigner amplitudes and one phase-space amplitude, the two significant structures are assigned masses of (4186.8±8.7±30) and (4414.6±3.4±6.1) MeV/c^{2}, widths of (55±15±53) and (122.5±7.5±8.1) MeV, where the first errors are statistical and the second ones are systematic. The inclusion of a third Breit-Wigner amplitude is necessary to describe a structure around 4.79 GeV.
We study the process e^{+}e^{-}→Λ_{c}^{+}Λover ¯_{c}^{-} at twelve center-of-mass energies from 4.6119 to 4.9509 GeV using data samples collected by the BESIII detector at the BEPCII collider. The ...Born cross sections and effective form factors (|G_{eff}|) are determined with unprecedented precision after combining the single and double-tag methods based on the decay process Λ_{c}^{+}→pK^{-}π^{+}. Flat cross sections around 4.63 GeV are obtained and no indication of the resonant structure Y(4630), as reported by Belle, is found. In addition, no oscillatory behavior is discerned in the |G_{eff}| energy dependence of Λ_{c}^{+}, in contrast to what is seen for the proton and neutron cases. Analyzing the cross section together with the polar-angle distribution of the Λ_{c}^{+} baryon at each energy point, the moduli of electric and magnetic form factors (|G_{E}| and |G_{M}|) are extracted and separated. For the first time, the energy dependence of the form factor ratio |G_{E}/G_{M}| is observed, which can be well described by an oscillatory function.
Search for the doubly charmed baryon Ξcc Alexander, M.; Alves, A. A.; Baryshnikov, F. ...
Science China. Physics, mechanics & astronomy,
02/2020, Letnik:
63, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A search for the doubly charmed baryon
Ξ
c
c
+
is performed through its decay to the
Λ
c
+
K
−
π
+
final state, using proton-proton collision data collected with the LHCb detector at centre-of-mass ...energies of 7, 8 and 13 TeV. The data correspond to a total integrated luminosity of 9 fb
−1
. No significant signal is observed in the mass range from 3.4 to 3.8 GeV/
c
2
. Upper limits are set at 95% credibility level on the ratio of the
Ξ
c
c
+
production cross-section times the branching fraction to that of
Λ
c
+
and
Ξ
c
c
+
+
baryons. The limits are determined as functions of the
Ξ
c
c
+
mass for different lifetime hypotheses, in the rapidity range from 2.0 to 4.5 and the transverse momentum range from 4 to 15 GeV/
c
.
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
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
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
a
1
(1260)
+
(
→ ρ
+
π
0
) and
D
+
→
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.
A search for the rare decay Σ^{+}→pμ^{+}μ^{-} is performed using pp collision data recorded by the LHCb experiment at center-of-mass energies sqrts=7 and 8 TeV, corresponding to an integrated ...luminosity of 3 fb^{-1}. An excess of events is observed with respect to the background expectation, with a signal significance of 4.1 standard deviations. No significant structure is observed in the dimuon invariant mass distribution, in contrast with a previous result from the HyperCP experiment. The measured Σ^{+}→pμ^{+}μ^{-} branching fraction is (2.2_{-1.3}^{+1.8})×10^{-8}, where statistical and systematic uncertainties are included, which is consistent with the standard model prediction.
The BESIII experiment at the electron-positron collider BEPCII in Beijing (China) is successfully operating since 2008 and has collected large data samples in the tau-mass region, including the ...world's largest data samples at the \(J/\psi\) and \(\psi'\) resonances. The recent observations of hyperon polarizations at BESIII opens a new window for testing CP violation, as it allows for simultaneous production and detection of hyperon and anti-hyperon pair two-body weak decays. The CP-symmetry tests can be performed in processes like e.g. \(J/\psi\to\Lambda\bar{\Lambda}\), \(J/\psi,\psi'\to\Sigma^+\bar{\Sigma}^-\) and \(J/\psi\to\Xi^-\bar{\Xi}^+\). For the \(\Xi^-\to\Lambda\pi^-\) decay it is possible to perform three independent CP tests and determine the strong phase and weak phase difference.
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