VEPP-2000 is the only electron–positron collider with round beams. This factor enables one to increase the beam–beam effect limit. During the 2018–2019 season, the experimental program was focused on ...the energy range of 550–990 MeV per beam. Data accumulation was performed using CMD-3 and SND detectors. The measured luminosity integral proved to have a record value of 68 pb
–1
per detector. After connecting to the BINP injection complex in 2016, the luminosity of VEPP-2000 is limited by the beam–beam effects in the entire energy range.
A
bstract
The cross section of the process
e
+
e
−
→ ηπ
+
π
−
is measured using the data collected with the CMD-3 detector at the VEPP-2000 collider in the center-of-mass energy range from 1
.
1 to 2
....
0 GeV. The decay mode
η → γγ
is used for
η
meson reconstruction in the data sample corresponding to an integrated luminosity of 78
.
3 pb
−
1
. The energy dependence of the
e
+
e
−
→ ηπ
+
π
−
cross section is fitted within the framework of vector meson dominance in order to extract the Γ(
ρ
(1450)
→ e
+
e
−
)
B
(
ρ
(1450)
→ ηπ
+
π
−
) and the Γ(
ρ
(1700)
→ e
+
e
−
)
B
(
ρ
(1700)
→ ηπ
+
π
−
) products. Based on conservation of vector current, the analyzed data are used to test the relationship between the
e
+
e
−
→ ηπ
+
π
−
cross section and the spectral function in
τ
−
→ ηπ
−
π
0
ντ
decay. The
e
+
e
−
→ ηπ
+
π
−
cross section obtained with the CMD-3 detector is in good agreement with the previous measurements.
This paper reports measurements of the hadronic cross sections with the CMD-3 detector at the VEPP-2000 electron-positron collider. The overall size of the data sample analyzed is about 60 pb-1, ...collected by the CMD- 3 running since December 2010 up to June 2013 in the c.m. energy range from 0.32 to 2.0 GeV. The preliminary results of data analysis for various modes of e+e−→hadrons are discussed.
The Spherical Neutral Detector (SND) is an experiment for e+e− annihilation study at low energies 0.2−2 GeV. The light quark anti−quark bound states are the main subject of study at these energies. ...They express themselves as resonances in the e+e− hadronic cross sections. Hadronic cross sections could be recalculated to hadronic vacuum polarization (HVP). The Standard Model predictions today are limited by HVP which is not calculable with modern QCD theory. In this talk we present the review of the hadronic cross sections measurements at SND and new measurements: e+e− → π+π−, π0γ, π+π−π0, ωπ0, K+K−η, η, KsKLπ0, π+π−π0η, ωπ0η e.t.c.
Abstract
The process
$$e^+e^-\rightarrow \eta \pi ^0\gamma $$
e
+
e
-
→
η
π
0
γ
is studied in the center-of-mass energy range 1.05–2.00 GeV using data with an integrated luminosity of 94.5
$$\hbox ...{pb}^{-1}$$
pb
-
1
collected by the SND detector at the VEPP-2000
$$e^{+}e^{-}$$
e
+
e
-
collider. The
$$e^+e^-\rightarrow \eta \pi ^0\gamma $$
e
+
e
-
→
η
π
0
γ
cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the
$$\omega \eta $$
ω
η
intermediate state. The measured cross section of the subprocess
$$e^+e^-\rightarrow \omega \eta \rightarrow \eta \pi ^0\gamma $$
e
+
e
-
→
ω
η
→
η
π
0
γ
is consistent with previous measurements in the
$$e^+e^-\rightarrow \pi ^+\pi ^-\pi ^0\eta $$
e
+
e
-
→
π
+
π
-
π
0
η
mode. It is found, with a significance of
$$5.6\sigma $$
5.6
σ
, that the process
$$e^+e^-\rightarrow \eta \pi ^0\gamma $$
e
+
e
-
→
η
π
0
γ
is not completely described by hadronic vector-pseudoscalar intermediate states. The cross section of this missing contribution, which can originate from radiation processes, e. g.
$$e^+e^-\rightarrow a_{0}(1450)\gamma $$
e
+
e
-
→
a
0
(
1450
)
γ
, is measured. It is found to be 15–20 pb in the wide energy range from 1.3 to 1.9 GeV.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The process e+e-→ηπ0γ is studied in the center-of-mass energy range 1.05–2.00 GeV using data with an integrated luminosity of 94.5 pb-1 collected by the SND detector at the VEPP-2000 e+e- collider. ...The e+e-→ηπ0γ cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the ωη intermediate state. The measured cross section of the subprocess e+e-→ωη→ηπ0γ is consistent with previous measurements in the e+e-→π+π-π0η mode. It is found, with a significance of 5.6σ, that the process e+e-→ηπ0γ is not completely described by hadronic vector-pseudoscalar intermediate states. The cross section of this missing contribution, which can originate from radiation processes, e. g. e+e-→a0(1450)γ, is measured. It is found to be 15–20 pb in the wide energy range from 1.3 to 1.9 GeV.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract The process $$e^+e^-\rightarrow \eta \pi ^0\gamma $$ e + e - → η π 0 γ is studied in the center-of-mass energy range 1.05–2.00 GeV using data with an integrated luminosity of 94.5 $$\hbox ...{pb}^{-1}$$ pb - 1 collected by the SND detector at the VEPP-2000 $$e^{+}e^{-}$$ e + e - collider. The $$e^+e^-\rightarrow \eta \pi ^0\gamma $$ e + e - → η π 0 γ cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the $$\omega \eta $$ ω η intermediate state. The measured cross section of the subprocess $$e^+e^-\rightarrow \omega \eta \rightarrow \eta \pi ^0\gamma $$ e + e - → ω η → η π 0 γ is consistent with previous measurements in the $$e^+e^-\rightarrow \pi ^+\pi ^-\pi ^0\eta $$ e + e - → π + π - π 0 η mode. It is found, with a significance of $$5.6\sigma $$ 5.6 σ , that the process $$e^+e^-\rightarrow \eta \pi ^0\gamma $$ e + e - → η π 0 γ is not completely described by hadronic vector-pseudoscalar intermediate states. The cross section of this missing contribution, which can originate from radiation processes, e. g. $$e^+e^-\rightarrow a_{0}(1450)\gamma $$ e + e - → a 0 ( 1450 ) γ , is measured. It is found to be 15–20 pb in the wide energy range from 1.3 to 1.9 GeV.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
The dynamics of the process
$$ e^+e^- \rightarrow \pi ^+\pi ^-\pi ^0 $$
e
+
e
-
→
π
+
π
-
π
0
is studied in the energy region from 1.15 to 2.00 GeV using data accumulated with the SND ...detector at the VEPP-2000
$$e^+e^-$$
e
+
e
-
collider. The Dalitz plot distribution and
$$\pi ^+\pi ^-$$
π
+
π
-
mass spectrum are analyzed in a model including the intermediate states
$$\rho (770)\pi $$
ρ
(
770
)
π
,
$$\rho (1450)\pi $$
ρ
(
1450
)
π
, and
$$\omega \pi ^0$$
ω
π
0
. As a result, the energy dependences of the
$$\rho (770)\pi $$
ρ
(
770
)
π
and
$$\rho (1450)\pi $$
ρ
(
1450
)
π
cross sections and the relative phases between the
$$\rho (770)\pi $$
ρ
(
770
)
π
amplitude and the
$$\rho (1450)\pi $$
ρ
(
1450
)
π
and
$$\omega \pi ^0$$
ω
π
0
amplitudes are obtained. The
$$\rho (1450)\pi $$
ρ
(
1450
)
π
cross section has a peak in the energy region of the
$$\omega (1650)$$
ω
(
1650
)
resonance (1.55–1.75 GeV). In this energy range the contributions of the
$$\rho (770)\pi $$
ρ
(
770
)
π
and
$$\rho (1450)\pi $$
ρ
(
1450
)
π
states are of the same order of magnitude. No resonance structure near 1.65 GeV is observed in the
$$\rho (770)\pi $$
ρ
(
770
)
π
cross section. We conclude that the intermediate state
$$\rho (1450)\pi $$
ρ
(
1450
)
π
gives a significant contribution to the decay of
$$\omega (1650)\rightarrow \pi ^+\pi ^-\pi ^0$$
ω
(
1650
)
→
π
+
π
-
π
0
, whereas the
$$\rho (770)\pi $$
ρ
(
770
)
π
mechanism dominates in the decay
$$\omega (1420)\rightarrow \pi ^+\pi ^-\pi ^0$$
ω
(
1420
)
→
π
+
π
-
π
0
.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract The dynamics of the process $$ e^+e^- \rightarrow \pi ^+\pi ^-\pi ^0 $$ e + e - → π + π - π 0 is studied in the energy region from 1.15 to 2.00 GeV using data accumulated with the SND ...detector at the VEPP-2000 $$e^+e^-$$ e + e - collider. The Dalitz plot distribution and $$\pi ^+\pi ^-$$ π + π - mass spectrum are analyzed in a model including the intermediate states $$\rho (770)\pi $$ ρ ( 770 ) π , $$\rho (1450)\pi $$ ρ ( 1450 ) π , and $$\omega \pi ^0$$ ω π 0 . As a result, the energy dependences of the $$\rho (770)\pi $$ ρ ( 770 ) π and $$\rho (1450)\pi $$ ρ ( 1450 ) π cross sections and the relative phases between the $$\rho (770)\pi $$ ρ ( 770 ) π amplitude and the $$\rho (1450)\pi $$ ρ ( 1450 ) π and $$\omega \pi ^0$$ ω π 0 amplitudes are obtained. The $$\rho (1450)\pi $$ ρ ( 1450 ) π cross section has a peak in the energy region of the $$\omega (1650)$$ ω ( 1650 ) resonance (1.55–1.75 GeV). In this energy range the contributions of the $$\rho (770)\pi $$ ρ ( 770 ) π and $$\rho (1450)\pi $$ ρ ( 1450 ) π states are of the same order of magnitude. No resonance structure near 1.65 GeV is observed in the $$\rho (770)\pi $$ ρ ( 770 ) π cross section. We conclude that the intermediate state $$\rho (1450)\pi $$ ρ ( 1450 ) π gives a significant contribution to the decay of $$\omega (1650)\rightarrow \pi ^+\pi ^-\pi ^0$$ ω ( 1650 ) → π + π - π 0 , whereas the $$\rho (770)\pi $$ ρ ( 770 ) π mechanism dominates in the decay $$\omega (1420)\rightarrow \pi ^+\pi ^-\pi ^0$$ ω ( 1420 ) → π + π - π 0 .
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The dynamics of the process e+e-→π+π-π0 is studied in the energy region from 1.15 to 2.00 GeV using data accumulated with the SND detector at the VEPP-2000 e+e- collider. The Dalitz plot distribution ...and π+π- mass spectrum are analyzed in a model including the intermediate states ρ(770)π, ρ(1450)π, and ωπ0. As a result, the energy dependences of the ρ(770)π and ρ(1450)π cross sections and the relative phases between the ρ(770)π amplitude and the ρ(1450)π and ωπ0 amplitudes are obtained. The ρ(1450)π cross section has a peak in the energy region of the ω(1650) resonance (1.55–1.75 GeV). In this energy range the contributions of the ρ(770)π and ρ(1450)π states are of the same order of magnitude. No resonance structure near 1.65 GeV is observed in the ρ(770)π cross section. We conclude that the intermediate state ρ(1450)π gives a significant contribution to the decay of ω(1650)→π+π-π0, whereas the ρ(770)π mechanism dominates in the decay ω(1420)→π+π-π0.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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