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The target asymmetry T , recoil asymmetry P , and beam-target double polarization observable H were determined in exclusive π 0 and η photoproduction off quasi-free protons and, for the first time, off quasi-free neutrons. The experiment was performed at the electron stretcher accelerator ELSA in Bonn, Germany, with the Crystal Barrel/TAPS detector setup, using a linearly polarized photon beam and a transversely polarized deuterated butanol target. Effects from the Fermi motion of the nucleons within deuterium were removed by a full kinematic reconstruction of the final state invariant mass. A comparison of the data obtained on the proton and on the neutron provides new insight into the isospin structure of the electromagnetic excitation of the nucleon. Earlier measurements of polarization observables in the γ p → π 0 p and γ p → η p reactions are confirmed. The data obtained on the neutron are of particular relevance for clarifying the origin of the narrow structure in the η n system at W = 1.68 GeV . A comparison with recent partial wave analyses favors the interpretation of this structure as arising from interference of the S 11 ( 1535 ) and S 11 ( 1650 ) resonances within the S 11 -partial wave.

A bstract The product of the electronic width of the J/ψ meson and the branching fractions of its decay to hadrons and electrons has been measured using the KEDR detector at the VEPP-4M e + e − collider. The obtained values are Γ e e J / ψ = 5.550 ± 0.056 ± 0.089 keV , Γ e e J / ψ · ℬ hadrons J / ψ = 4.884 ± 0.048 ± 0.078 keV , Γ e e J / ψ · ℬ e e J / ψ = 0.3331 ± 0.0066 ± 0.0040 keV . The uncertainties shown are statistical and systematic, respectively. Using the result presented and the world-average value of the electronic branching fraction, one obtains the total width of the J/ψ meson: Γ = 92.94 ± 1.83 keV . These results are consistent with the previous experiments.

The pulse shaper based on a capacitive storage device with an active switch operating on a resistive load is considered. The electrical circuit includes a capacitor with a reference voltage for the stabilization of peak of the pulse. The capacitor connected in parallel with a load via the unilateral conductive switch. A general analysis of the shaping circuit was carried out. Analytical expressions for determination of the stabilization accuracy and the stabilization duration have been obtained. The results of computer simulation of dependence of these characteristics as function of pulse parameters and shaper features are presented. The influence of short-term and abrupt change of the resistance load on the stabilization process of peak of the pulse is considered. The possibility of obtaining of pulses with a controlled stability of pulse peaks <1% for pulses with duration to 100 µs at voltages up to 20 kV and energy stored in a capacitor to 3.4 kJ is shown in prototype of the shaper.

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].

A new experiment SPASCHARM for systematic study of polarization phenomena in inclusive and exclusive hadronic reactions is currently under commissioning at IHEP. The universal experimental setup will detect dozens of various resonances and stable particles produced in collisions of unpolarized beams with the polarized target, and at the next stage, using polarized beams. At the first stage with polarized target, the final states composed of light quarks (u, d, s) will be reconstructed. Hyperon polarization and spin density matrix elements of the vector mesons will be measured along with the single-spin asymmetries. The 2π-acceptance in azimuth, which is extremely useful for reduction of systematic errors in measurements of spin observables, will be implemented in the experiment. The solid angle acceptance of the setup, Δθ≈250 mrad vertically and 350 mrad horizontally in the beam fragmentation region, covers a wide range of kinematic variables pT and xF. This provides the opportunity for separating dependences on these two variables which is usually not possible in the setups with a small solid angle acceptance. Unlike some previous polarization experiments, the SPASCHARM will be able to simultaneously accumulate and record data on the both, charged and neutral particle production.

We report the first measurement of the inclusive e + e − →$$ b\\overline{b} $$b b ¯ →$$ {D}_s^{\\pm } $$D s ± X and e + e − →$$ b\\overline{b} $$b b ¯ → D 0 /$$ {\\overline{D}}^0 $$D ¯ 0 X cross sections in the energy range from 10 . 63 to 11 . 02 GeV. Based on these results, we determine σ ( e + e − →$$ {B}_s^0{\\overline{B}}_s^0 $$B s 0 B ¯ s 0 X ) and σ ( e + e − →$$ B\\overline{B} $$B B ¯ X ) in the same energy range. We measure the fraction of$$ {B}_s^0 $$B s 0 events at Υ(10860) to be f s = ($$ {22.0}_{-2.1}^{+2.0} $$22.0 − 2.1 + 2.0 )%. We determine also the ratio of the$$ {B}_s^0 $$B s 0 inclusive branching fractions$$ \\mathcal{B} $$B ($$ {B}_s^0 $$B s 0 → D 0 /$$ {\\overline{D}}^0 $$D ¯ 0 X ) /$$ \\mathcal{B} $$B ($$ {B}_s^0 $$B s 0 →$$ {D}_s^{\\pm } $$D s ± X ) = 0 . 416 ± 0 . 018 ± 0 . 092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energy e + e − collider.

We report the first measurement of the inclusive e+e- → bb̄ → D^(±)_(s) X and e+e- → bb̄ → D0 / D̅⁰ X cross sections in the energy range from 10.63 to 11.02 GeV. Based on these results, we determine σ(e+e- → B_(s)⁰B̅_(s)⁰ X) and σ(e+e- → BB̅ X) in the same energy range. We measure the fraction of B_(s)⁰ events at Υ(10860) to be fs = (22.0_(-2.1)^(+2.0))%. We determine also the ratio of the B_(s)⁰ inclusive branching fractions 𝓑(B_(s)⁰ → D0/ D̅⁰X)/𝓑(B_(s)⁰ → D_(s)^(±)X) = 0.416 ± 0.018 ± 0.092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider.

The target asymmetry T , recoil asymmetry P , and beam-target double polarization observable H were determined in exclusive$$\\pi ^0$$π 0 and$$\\eta $$η photoproduction off quasi-free protons and, for the first time, off quasi-free neutrons. The experiment was performed at the electron stretcher accelerator ELSA in Bonn, Germany, with the Crystal Barrel/TAPS detector setup, using a linearly polarized photon beam and a transversely polarized deuterated butanol target. Effects from the Fermi motion of the nucleons within deuterium were removed by a full kinematic reconstruction of the final state invariant mass. A comparison of the data obtained on the proton and on the neutron provides new insight into the isospin structure of the electromagnetic excitation of the nucleon. Earlier measurements of polarization observables in the$$\\gamma p \\rightarrow \\pi ^0 p$$γ p → π 0 p and$$\\gamma p \\rightarrow \\eta p$$γ p → η p reactions are confirmed. The data obtained on the neutron are of particular relevance for clarifying the origin of the narrow structure in the$$\\eta n$$η n system at$$W = 1.68\\ \\textrm{GeV}$$W = 1.68 GeV . A comparison with recent partial wave analyses favors the interpretation of this structure as arising from interference of the$$S_{11}(1535)$$S 11 ( 1535 ) and$$S_{11}(1650)$$S 11 ( 1650 ) resonances within the$$S_{11}$$S 11 -partial wave.

Using a data sample of 980 fb − 1 collected with the Belle detector at the KEKB asymmetric-energy e + e − collider, we study the processes of$$ {\\Xi}_c^0\\to \\Lambda {\\overline{K}}^{\\ast 0} $$Ξ c 0 → Λ K ¯ ∗ 0 ,$$ {\\Xi}_c^0\\to {\\Sigma}^0{\\overline{K}}^{\\ast 0} $$Ξ c 0 → Σ 0 K ¯ ∗ 0 , and$$ {\\Xi}_c^0\\to {\\Sigma}^{+}{K}^{\\ast -} $$Ξ c 0 → Σ + K ∗ − for the first time. The relative branching ratios to the normalization mode of$$ {\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+} $$Ξ c 0 → Ξ − π + are measured to be$$ {\\displaystyle \\begin{array}{c}\\mathcal{B}\\left({\\Xi}_c^0\\to \\Lambda {\\overline{K}}^{\\ast 0}\\right)/\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right)=0.18\\pm 0.02\\left(\\mathrm{stat}.\\right)\\pm 0.01\\left(\\mathrm{syst}.\\right),\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Sigma}^0{\\overline{K}}^{\\ast 0}\\right)/\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right)=0.69\\pm 0.03\\left(\\mathrm{stat}.\\right)\\pm 0.03\\left(\\mathrm{syst}.\\right),\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Sigma}^{+}{K}^{\\ast -}\\right)/\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right)=0.34\\pm 0.06\\left(\\mathrm{stat}.\\right)\\pm 0.02\\left(\\mathrm{syst}.\\right),\\end{array}} $$B Ξ c 0 → Λ K ¯ ∗ 0 / B Ξ c 0 → Ξ − π + = 0.18 ± 0.02 stat . ± 0.01 syst . , B Ξ c 0 → Σ 0 K ¯ ∗ 0 / B Ξ c 0 → Ξ − π + = 0.69 ± 0.03 stat . ± 0.03 syst . , B Ξ c 0 → Σ + K ∗ − / B Ξ c 0 → Ξ − π + = 0.34 ± 0.06 stat . ± 0.02 syst . , where the uncertainties are statistical and systematic, respectively. We obtain$$ {\\displaystyle \\begin{array}{c}\\mathcal{B}\\left({\\Xi}_c^0\\to \\Lambda {\\overline{K}}^{\\ast 0}\\right)=\\left(3.3\\pm 0.3\\left(\\mathrm{stat}.\\right)\\pm 0.2\\left(\\mathrm{syst}.\\right)\\pm 1.0\\left(\\mathrm{ref}.\\right)\\right)\\times {10}^{-3},\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Sigma}^0{\\overline{K}}^{\\ast 0}\\right)=\\left(12.4\\pm 0.5\\left(\\mathrm{stat}.\\right)\\pm 0.5\\left(\\mathrm{syst}.\\right)\\pm 3.6\\left(\\mathrm{ref}.\\right)\\right)\\times {10}^{-3},\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Sigma}^{+}{K}^{\\ast 0}\\right)=\\left(6.1\\pm 1.0\\left(\\mathrm{stat}.\\right)\\pm 0.4\\left(\\mathrm{syst}.\\right)\\pm 1.8\\left(\\mathrm{ref}.\\right)\\right)\\times {10}^{-3},\\end{array}} $$B Ξ c 0 → Λ K ¯ ∗ 0 = 3.3 ± 0.3 stat . ± 0.2 syst . ± 1.0 ref . × 10 − 3 , B Ξ c 0 → Σ 0 K ¯ ∗ 0 = 12.4 ± 0.5 stat . ± 0.5 syst . ± 3.6 ref . × 10 − 3 , B Ξ c 0 → Σ + K ∗ 0 = 6.1 ± 1.0 stat . ± 0.4 syst . ± 1.8 ref . × 10 − 3 , where the uncertainties are statistical, systematic, and from$$ \\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right) $$B Ξ c 0 → Ξ − π + , respectively. The asymmetry parameters$$ \\alpha \\left({\\Xi}_c^0\\to \\Lambda {\\overline{K}}^{\\ast 0}\\right) $$α Ξ c 0 → Λ K ¯ ∗ 0 and$$ \\alpha \\left({\\Xi}_c^0\\to {\\Sigma}^{+}{K}^{\\ast -}\\right) $$α Ξ c 0 → Σ + K ∗ − are 0 . 15 ± 0 . 22(stat . ) ± 0 . 04(syst . ) and − 0 . 52 ± 0 . 30(stat . ) ± 0 . 02(syst . ), respectively, where the uncertainties are statistical followed by systematic.

Using a data sample of 980 fb-1 collected with the Belle detector at the KEKB asymmetric-energy e+e- collider, we study the processes of ${\\Xi}_c^0\\to \\Lambda {\\overline{K}}^{\\ast 0}$, ${\\Xi}_c^0\\to {\\Sigma}^0{\\overline{K}}^{\\ast 0}$, and ${\\Xi}_c^0\\to {\\Sigma}^{+}{K}^{\\ast -}$ for the first time. The relative branching ratios to the normalization mode of ${\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}$ are measured to be ${\\displaystyle \\begin{array}{c}\\mathcal{B}\\left({\\Xi}_c^0\\to \\Lambda {\\overline{K}}^{\\ast 0}\\right)/\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right)=0.18\\pm 0.02\\left(\\mathrm{stat}.\\right)\\pm 0.01\\left(\\mathrm{syst}.\\right),\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Sigma}^0{\\overline{K}}^{\\ast 0}\\right)/\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right)=0.69\\pm 0.03\\left(\\mathrm{stat}.\\right)\\pm 0.03\\left(\\mathrm{syst}.\\right),\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Sigma}^{+}{K}^{\\ast -}\\right)/\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right)=0.34\\pm 0.06\\left(\\mathrm{stat}.\\right)\\pm 0.02\\left(\\mathrm{syst}.\\right),\\end{array}}$ where the uncertainties are statistical and systematic, respectively. We obtain ${\\displaystyle \\begin{array}{c}\\mathcal{B}\\left({\\Xi}_c^0\\to \\Lambda {\\overline{K}}^{\\ast 0}\\right)=\\left(3.3\\pm 0.3\\left(\\mathrm{stat}.\\right)\\pm 0.2\\left(\\mathrm{syst}.\\right)\\pm 1.0\\left(\\mathrm{ref}.\\right)\\right)\\times {10}^{-3},\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Sigma}^0{\\overline{K}}^{\\ast 0}\\right)=\\left(12.4\\pm 0.5\\left(\\mathrm{stat}.\\right)\\pm 0.5\\left(\\mathrm{syst}.\\right)\\pm 3.6\\left(\\mathrm{ref}.\\right)\\right)\\times {10}^{-3},\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Sigma}^{+}{K}^{\\ast 0}\\right)=\\left(6.1\\pm 1.0\\left(\\mathrm{stat}.\\right)\\pm 0.4\\left(\\mathrm{syst}.\\right)\\pm 1.8\\left(\\mathrm{ref}.\\right)\\right)\\times {10}^{-3},\\end{array}}$ where the uncertainties are statistical, systematic, and from $\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right)$, respectively. The asymmetry parameters $\\alpha \\left({\\Xi}_c^0\\to \\Lambda {\\overline{K}}^{\\ast 0}\\right)$ and $\\alpha \\left({\\Xi}_c^0\\to {\\Sigma}^{+}{K}^{\\ast -}\\right)$ are 0.15 ± 0.22(stat.) ± 0.04(syst.) and -0.52 ± 0.30(stat.) ± 0.02(syst.), respectively, where the uncertainties are statistical followed by systematic.