Russian institutes will participate in setting up the experiments HIHEX (Heavy Ion Heating and Expansion) and LAPLAS (Laboratory Planetary Sciences) as part of the FAIR program of scientific ...research. The appropriate numerical calculations of targets and preliminary experiments will be performed. Two vacuum chambers for studying the thermodynamic, transport, and optical properties of extreme states generated when matter is heated by intense heavy-ion beams will be developed and built. A system for obtaining a cylindrical beam and the corresponding cryogenic system for the LAPLAS experiments will be developed and built. Special attention will be focused on the development of proton radiography for diagnostics of extreme states of matter.
Search for the process e + e − → η Achasov, M. N.; Barnyakov, A. Yu; Beloborodov, K. I. ...
Physical review. D,
09/2018, Volume:
98, Issue:
5
Journal Article
Peer reviewed
Open access
A search for the rare decay η→e+e− is performed using the inverse process e+e−→η in the decay mode η→π0π0π0. We analyze data with an integrated luminosity of 654 nb−1 accumulated at the VEPP-2000 ...e+e− collider with the SND detector at the center-of-mass energy E=mηc2≈548 MeV, and set the upper limit B(η→e+e−)<7×10−7 at the 90% confidence level.
The 800 MeV proton radiography facility for high dynamic pressure research in condensed matter has been commissioned at the Terrawatt Accelerator of Institute of Theoretical and Experimental Physics ...(TWAC-ITEP) in Moscow. Spatial resolution of the facility measured in static experiments with a variety of test objects was found to be 0.30±0.01 mm in current experimental arrangement. First dynamic experiments on the observation of a shock loading of steel surface and a propagation of the detonation wave in a high explosive charge were conducted. Good quantitative agreement of density profiles reconstructed from obtained radiographic images with theoretical and simulated data showed the capabilities of high energy ion beam radiography as an excellent tool for bulk density measurements in high dynamic pressure studies.
A
bstract
The cross section of the process
e
+
e
−
→
π
+
π
−
has been measured in the Spherical Neutral Detector (SND) experiment at the VEPP-2000
e
+
e
−
collider VEPP-2000 in the energy region 525
...<
$$ \sqrt{s} $$
s
<
883 MeV. The measurement is based on data with an integrated luminosity of about 4.6 pb
−
1
. The systematic uncertainty of the cross section determination is 0.8% at
$$ \sqrt{s} $$
s
>
0
.
600 GeV. The
ρ
meson parameters are obtained as
m
ρ
= 775
.
3 ± 0
.
5 ± 0
.
6 MeV, Γ
ρ
= 145
.
6 ± 0
.
6 ± 0
.
8 MeV,
B
ρ
→
e
+
e−
×
B
ρ
→
π
+
π−
= (4
.
89 ± 0
.
02 ± 0
.
04) × 10
−
5
, and the parameters of the
e
+
e
−
→
ω
→
π
+
π
−
process, suppressed by
G
-parity, as
B
ω
→
e
+
e−
×
B
ω
→
π
+
π−
= (1
.
32 ± 0
.
06 ± 0
.
02) × 10
−
6
and and
ϕ
ρω
= 110
.
7 ± 1
.
5 ± 1
.
0 degrees.
Formation of homo- and copolymers of various structures (random and block) based on
tert
-butyl acrylate and
n
-butyl acrylate via polymerization mediated by trithiocarbonates as reversible ...addition-fragmentation chain-transfer agents has been studied. The process is found to proceed according to a three-stage mechanism. As a result, it is possible to synthesize symmetric triblock copolymers with the use of polymer trithiocarbonates; the polymer reversible addition-fragmentation chain transfer agent predetermines the composition and molecular mass of end blocks, the composition of the monomer mixture determines the structure of the central block, and the concentration of the agent and the conversion of the monomers define its molecular-mass characteristics. The modification of polymerization products gives rise to amphiphilic copolymers.
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.
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.
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.
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 .
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.
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