Based on ( 27.12 ± 0.14 ) × 10 8 ψ ( 2 S ) events collected by the BESIII detector, we search for the decay η c ( 2 S ) → π + π − η c via ψ ( 2 S ) → γ η c ( 2 S ) . No significant signal is ...observed, and the upper limit on the product branching fraction B ( ψ ( 2 S ) → γ η c ( 2 S ) ) × B ( η c ( 2 S ) → π + π − η c ) is determined to be 2.21 × 10 − 5 at the 90% confidence level. In addition, the η c ( 2 S ) → π + π − K S 0 K ± π ∓ decay is studied via ψ ( 2 S ) → γ η c ( 2 S ) and is observed with a statistical significance of 10 σ for the first time. The branching fraction of η c ( 2 S ) → π + π − K S 0 K ± π ∓ is determined to be ( 1.33 ± 0.11 ± 0.40 ± 0.95 ) × 10 − 2 , where the first uncertainty is statistical, the second is systematic, and the third uncertainty is due to the quoted B ( ψ ( 2 S ) → γ η c ( 2 S ) ) . Published by the American Physical Society 2024
We present a measurement of the azimuthal asymmetries of two charged pions in the inclusive process e+ e- arrow right pipiX, based on a data set of 62 pb super(-1) at the center-of-mass energy of ...3.65 GeV collected with the BESIII detector. These asymmetries can be attributed to the Collins fragmentation function. We observe a nonzero asymmetry, which increases with increasing pion momentum. As our energy scale is close to that of the existing semi-inclusive deep inelastic scattering experimental data, the measured asymmetries are important inputs for the global analysis of extracting the quark transversity distribution inside the nucleon and are valuable to explore the energy evolution of the spin-dependent fragmentation function.
A bstract Using e + e − collision data collected with the BESIII detector at the BEPCII collider at center-of-mass energies between 3.510 and 4.914 GeV, corresponding to an integrated luminosity of ...25 fb − 1 , we measure the Born cross sections for the process $$ {e}^{+}{e}^{-}\to {K}^{-}{\overline{\Xi}}^{+}\Lambda /{\Sigma}^0 $$ e + e − → K − Ξ ¯ + Λ / Σ 0 at thirty-five energy points with a partial-reconstruction strategy. By fitting the dressed cross sections of $$ {e}^{+}{e}^{-}\to {K}^{-}{\overline{\Xi}}^{+}\Lambda /{\Sigma}^0 $$ e + e − → K − Ξ ¯ + Λ / Σ 0 , evidence for $$ \psi (4160)\to {K}^{-}{\overline{\Xi}}^{+}\Lambda $$ ψ 4160 → K − Ξ ¯ + Λ is found for the first time with a significance of 4.4 σ , including systematic uncertainties. No evidence for other possible resonances is found. In addition, the products of electronic partial width and branching fraction for all assumed resonances decaying into $$ {K}^{-}{\overline{\Xi}}^{+}\Lambda /{\Sigma}^0 $$ K − Ξ ¯ + Λ / Σ 0 are determined.
Radiation hardness of different types of GaN based epitaxial structures which can be used as elements of electronic devices is studied by Hall effect,CV and IV measurements, as well as ...photoluminescence and Raman scattering. It is shown that proton irradiation leads to formation of deep acceptor states reducing conductivity of high electron mobility transistors (HEMTs) and Si-doped layers and is accompanied by a redistribution of the defect-related lines in the photoluminescence spectra. Our results demonstrate that proton irradiation increases conductivity for GaN:C, while decreases it for GaN:Fe and GaN:(Fe+C) layers.
The Jülich Electric Dipole moment Investigation (JEDI) collaboration aims at a direct measurement of the Electric Dipole Moment (EDM) of protons and deuterons using a storage ring. The measurement is ...based on a polarization measurement. In order to reach highest accuracy, one has to know the exact trajectory through the magnets, especially the quadrupoles, to avoid the influence of magnetic fields on the polarization vector. In this paper, the development of a beam-based alignment technique is described that was developed and implemented at the COoler SYnchrotron (COSY) at Forschungszentrum Jülich. Well aligned quadrupoles permit one to absolutely calibrate the Beam Position Monitors (BPMs). The method is based on the fact that a particle beam, which does not pass through the center of a quadrupole, experiences a deflection. The precision reached by the method is approximately 40μm. Some consequences for the design of a new high precision storage ring for EDM mesasurements are discussed.
The Dalitz decay π0 → e+e-γ has been measured in the γp → π0p reaction with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The value obtained for the slope parameter of the π0 ...electromagnetic transition form factor, aπ= 0.030 ± 0.010tot, is in agreement with existing measurements of this decay and with recent theoretical calculations. The uncertainty obtained in the value of aπ is lower than in previous results based on the π0 → e+e-γ decay.
The 'exciton gas-plasma' transition (the Mott transition) in a Si{sub 0.93}Ge{sub 0.07}/Si thin quantum well is investigated using low-temperature photoluminescence. It is demonstrated that this ...transition is smooth and occurs in the concentration range from approximately 6 x 10{sup 10} to 1.2 x 10{sup 12} cm{sup -2}. At a temperature of 23 K and excitation densities of higher than 10 W/cm{sup 2}, the shape and location of the luminescence line associated with the electron-hole plasma remain unchanged with an increase in the pump density. This can indicate the occurrence of an 'electron-hole gas-liquid' transition. It is shown that, in the spectrum of the quantum well, the luminescence of boron-bound excitons dominates at liquid-helium temperatures and low excitation densities, whereas the free-exciton luminescence dominates at temperatures above 10 K. The influence of the homogeneous and inhomogeneous broadening on the electron-hole plasma and exciton luminescence is discussed.
In this study, it is found that furfural in the presence of Pt–M/Al
2
O
3
-catalysts (where M is Cu and Ni) at a temperature of 90°С is converted into furfuryl alcohol with selectivity reaching 90%; ...and at 150°C, it is converted to α-methylfuran with a selectivity of 92%. Note that the yield of furfural resinification products in the experiments performed does not exceed 5%. It is shown that tetralin is the most effective solvent, which prevents the resinification of furfural, and the use of aluminum oxide as a carrier makes it possible, at the same temperatures, to increase the degree of conversion of furfural in comparison with silicon oxide and sibunite. The results obtained allow us to propose an efficient method for the production of valuable petrochemical products from renewable raw materials.
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