Recently, a
γ
γ
collider based on the existing 17.5 GeV linac of the European XFEL has been proposed. High-energy photons will be generated by Compton scattering of laser photons with a wavelength of ...0.5–1
μ
m
on electrons. Such a photon collider covers the range of invariant masses
W
γ
γ
<
12
Ge
V
/
c
2
. The physics program includes spectroscopy of
C
-even resonances (
c
-,
b
-quarkonia, 4-quark states, glueballs) in various
J
P
states. Variable circular and linear polarizations will help in determining the quantum numbers. In this paper, we present a summary of measured and predicted two-photon widths of various resonances in the mass region 3–12
Ge
V
/
c
2
and investigate the experimental possibility of observing these heavy two-photon resonances under the conditions of a large multi-hadron background. Registration of all final particles is assumed. The minimum values of
Γ
γ
γ
(
W
)
are obtained at which resonances can be detected at a
5
σ
confidence level in 1 year of operation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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•Pt loading and oxidative treatment conditions determine Pt state in Pt/CeO2 catalysts.•Calcination at 300 and 500 °C provides Pt incorporation into ceria lattice.•Reduction of ...ceria-incorporated Pt species yields ultrasmall Pt particles.•Ultrasmall (1.72 nm) Pt nanoparticles ensure Pt/CeO2 activity in CO oxidation.
The features of the formation of Pt species on the CeO2 surface from adsorbed PtCl6-yOy complexes in Pt/CeO2 catalysts depending on the Pt content (0.5, 1.0 and 2.0 wt.%) and treatment conditions (direct Pt precursor reduction, oxidative and reductive treatments) are studied by XRD, CO pulse chemisorption, H2-TPR, UV–vis DRS, and Raman spectroscopy. The temperature of oxidative decomposition of the Pt precursor is shown to be the key factor that defines the state and size of the Pt species formed. High pretreatment temperature (500 °C) provides Pt incorporation into ceria lattice and yields smaller Pt particles after reduction providing strong Pt–CeO2 interaction, while the reduction of the samples dried at 120 °C results in the pronounced agglomeration of the formed Pt species to yield Pt particles weakly bonded with the ceria.
Abstract
Recently, a
$$\gamma \gamma $$
γ
γ
collider based on the existing 17.5 GeV linac of the European XFEL has been proposed. High-energy photons will be generated by Compton scattering of laser ...photons with a wavelength of 0.5–1
$${\,\upmu \mathrm m}$$
μ
m
on electrons. Such a photon collider covers the range of invariant masses
$$W_{\gamma \gamma } <12$$
W
γ
γ
<
12
$${\mathrm {\,Ge V\!/}c^2}$$
Ge
V
/
c
2
. The physics program includes spectroscopy of
$$ C $$
C
-even resonances (
c
-,
b
-quarkonia, 4-quark states, glueballs) in various
$$J^P$$
J
P
states. Variable circular and linear polarizations will help in determining the quantum numbers. In this paper, we present a summary of measured and predicted two-photon widths of various resonances in the mass region 3–12
$${\mathrm {\,Ge V\!/}c^2}$$
Ge
V
/
c
2
and investigate the experimental possibility of observing these heavy two-photon resonances under the conditions of a large multi-hadron background. Registration of all final particles is assumed. The minimum values of
$$\varGamma _{\gamma \gamma }(W)$$
Γ
γ
γ
(
W
)
are obtained at which resonances can be detected at a
$$5\sigma $$
5
σ
confidence level in 1 year of operation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Large-scale monitoring of anthropogenic marine litter in the Barents Sea was carried out in 2012–2018. The marine litter composition was estimated by recording by-catch from pelagic and bottom ...trawling. Litter on the sea surface (floating litter) was also taken into account during visual observations. The contents of 949 pelagic and 1477 bottom trawls were analyzed. Marine litter was recorded in 256 pelagic and 571 bottom trawl catches and in 454 cases during visual observations. Litter was sorted into plastic, wood, metal, rubber, textiles, paper, and glass. The occurrence of plastic prevailed in all litter records. It covered 71% of marine litter observed on the surface, 97% in pelagic trawls, and 78% in bottom trawls. Fishery litter prevailed in plastic litter (about 65% of its weight). Wood was recorded in 19% of surface litter observations
,
1% in pelagic trawls and 13% in bottom ones. Metal, rubber, paper, textiles, and glass were occasionally observed; however, their weight (except glass) could be very large. Thus, metal and wood prevailed by weight on the bottom (45 and 36.8%, respectively). Wood prevailed in pelagic layers, being 73% of the total litter weight. The volume of plastic and wood prevailed on the sea surface (50 and 47%, respectively). The average density of all types of litter on the sea bottom was about 7.9 kg/km
2
. Some significant differences in the litter composition were recorded between the southwestern and northeastern areas of the Barents Sea.
A preliminary result of the KEDR/VEPP-4M experiment devoted to measuring the cross section for electron-positron annihilation to hadrons (
e
+
e
−
→ hadrons) in the energy region of
J
/
ψ
-resonance ...production is presented. The value found for the product of the
J
/
ψ
-meson width with respect to decay to electrons and the branching ratio for
J
/
ψ
-meson decay to hadrons is Γ
ee
B
h
= 4.67±0.04(stat.)± 0.22(syst.) keV.
Trends in the development of electrochemical methods for solving environmental problems were considered. Modern tendencies in research on the electrochemical destruction of toxic organic substances ...resistant to oxidation were analyzed. The use of three-dimensional (3D) electrodes and combined methods (electro-Fenton process combined with ultrasound, UV irradiation, etc.) increases the efficiency of destruction. Special attention was paid to studies at increased pressures. Increased pressure initially created with an inert gas did not substantially affect the kinetics of the anodic process. Increased pressure initially created with an electrochemically active gas (oxygen) accelerated the anodic oxidation of organic compounds (phenol and azo dyes (direct black 2S and stable disperse yellow 4K). The organic substances under study inhibit the cathodic reduction of oxygen, and the positive role of increased pressure is proven.
Abstract
Using the 1.32
$$\hbox {pb}^{-1}$$
pb
-
1
statistics collected at the
$$J/\psi $$
J
/
ψ
peak with the KEDR detector at the VEPP-4M
$$e^{+}e^{-\, }$$
e
+
e
-
collider, we measured the ...branching fractions of
$$J/\psi $$
J
/
ψ
meson decays to the final states 2(
$$\pi ^{+}\pi ^{-})\pi ^{0}$$
π
+
π
-
)
π
0
,
$$K^{+}K^{-}\pi ^{+}\pi ^{-}\pi ^{0}$$
K
+
K
-
π
+
π
-
π
0
, 2(
$$\pi ^{+}\pi ^{-})$$
π
+
π
-
)
and
$$K^{+}K^{-}\pi ^{+}\pi ^{-}$$
K
+
K
-
π
+
π
-
. The results obtained for the decays
$$J/\psi \rightarrow $$
J
/
ψ
→
2(
$$\pi ^{+}\pi ^{-})\pi ^{0}$$
π
+
π
-
)
π
0
,
$$J/\psi \rightarrow K^{+}K^{-}\pi ^{+}\pi ^{-}\pi ^{0}$$
J
/
ψ
→
K
+
K
-
π
+
π
-
π
0
contradict the measurements performed by other groups in the last century, but agree well with recent results of BABAR and BESIII collaborations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The electronic width of the
J
/
ψ
meson and its product by the branching fractions of
J
/
ψ
meson decay to hadrons and electrons measured with the KEDR detector at the VEPP-4M
e
+
e
−
collider have ...been reported in ref. 1.
—
The review presents the experiments performed with the KEDR detector at the
collider VEPP-4M in the energy range of
= 1.84–3.88 GeV. The cross section of
annihilation to hadrons was measured at 22 ...points of this range and the search for narrow resonances was conducted below 3.1 GeV. The masses of
and
mesons were measured with a record accuracy better than
; their partial and total widths were determined. Measurements of the tau lepton mass and masses of charged and neutral
mesons were performed with high precision. The measurements of the
parameters are discussed, and attention is drawn to some inconsistency of the procedure employed by the Particle Data Group for determining its parameters.
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