486 research outputs found

    Measurement of the η\eta -η\eta' mixing angle in π\pi^{-} and KK^{-} beams with GAMS-4π4\pi Setup

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    The results of mixing angle measurement for η\eta', η\eta mesons generated in charge exchange reactions with π\pi^{-} and KK^{-} beams are preseneted. When the η\eta', η\eta mesons are described in nonstrange(NS)--strange(S) quark basis the π\pi^{-} and KK^{-} beams allow to study ηq>|\eta_{q}> and ηs>|\eta_{s}> parts of the meson wave function. The cross section ratio at t=0t'=0 (GeV/c)2^{2} in the π\pi^{-} beam is Rπ(η/η)=0.56±0.04R_{\pi}(\eta'/\eta)= 0.56 \pm 0.04, results in mixing angle ϕP=(36.8±1.)o\phi_{P} = (36.8 \pm 1.)^{o} . For KK^{-} beam the ratio is RK(η/η)=1.30±0.16R_{K}(\eta'/\eta)= 1.30 \pm 0.16. It was found that gluonium content in η\eta' is sin2ψG=0.15±0.06\sin^{2}\psi_{G}= 0.15 \pm 0.06. The experiment was carried out with GAMS-4π\pi Setup.Comment: 6 pages, 4 figures, 1 table, to be submitted in European physical journal C. Minor changes, the Bibliography extende

    On the possibility of observing tetraquarks in the K+ beam

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    Various models of tetraquark generation in the reaction K+pT(us;sˉsˉ)XK^{+} p \rightarrow T (us; \bar{s}\bar{s})X are considered. The predictions for corresponding inclusive spectra were evaluated at the energy 32 and 250 GeV.Comment: 22 pages, 12 figures, 4 tables, 22 ref

    Energy flow problem solution based on state estimation approaches and smart meter data

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    Accurate electric energy (EE) measurements and billing estimations in a power system necessitate the development of an energy flow distribution model. This paper summarizes the results of investigations on a new problem related to the determination of EE flow in a power system over time intervals ranging from minutes to years. The problem is referred to as the energy flow problem (EFP). Generally, the grid state and topology may fluctuate over time. An attempt to use instantaneous (not integral) power values obtained from telemetry to solve classical electrical engineering equations leads to significant modeling errors, particularly with topology changes. A promoted EFP model may be suitable in the presence of such topological and state changes. Herein, EE flows are determined using state estimation approaches based on direct EE measurement data in Watt-hours (Volt-ampere reactive-hours) provided by electricity meters. The EFP solution is essential for a broad set of applications, including meter data validation, zero unbalance EE billing, and nontechnical EE loss check. © 202

    Study of the ηπo\eta\pi^o system in the mass range up to 1200 MeV

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    The reaction πpηπon\pi^-p \to \eta\pi^o n has been studied with GAMS-2000 spectrometer in the secondary 38 GeV/c π\pi^--beam of the IHEP U-70 accelerator. Partial wave analysis of the reaction has been performed in the ηπo\eta\pi^o mass range up to 1200 MeV. The a0(980)a_0(980)-meson is seen as a sharp peak in S-wave. The tt-dependence of a0(980)a_0(980) production cross section has been studied. Dominant production of the a0(980)a_0(980) at a small transfer momentum tt confirms the hypothesis of Achasov and Shestakov about significant contribution of the ρ2\rho_2 exchange (IGJPC=1+2I^GJ^{PC}=1^+2^{--}) in the mechanism of a0(980)a_0(980) meson production in tt-channel of the reaction.Comment: 4 pages, 3 figures, talk given at HADRON'9

    An Improved Limit on Invisible Decays of Positronium

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    The results of a new search for positronium decays into invisible final states are reported. Convincing detection of this decay mode would be a strong evid ence for new physics beyond the Standard Model (SM): for example the existence of extra--dimensions, of milli-charged particles, of new light gauge bosons or of mirror particles. Mirror matter could be a relevant dark matter candidate. In this paper the setup and the results of a new experiment are presented. In a collected sample of about (6.31±0.28)×106(6.31\pm0.28) \times 10^6 orthopositronium decay s, no evidence for invisible decays in an energy window [0,80] keV was found and an upper limit on the branching ratio of orthopositronium \invdecay could be set: \binvdecay<4.2\times 10^{-7} (90% C.L.) Our results provide a limit on the photon mirror-photon mixing strength ϵ1.55×107\epsilon \leq 1.55\times 10^{-7} (90% C.L.) and rule out particles lighter than the electron mass with a fraction Qx3.4×105Q_x \leq 3.4 \times 10^{-5} of the electron charge. Furthermore, upper limits on the branching ratios for the decay of parapositronium Br(pPsinvisible)4.3×107Br(p-Ps\to invisible)\leq 4.3 \times 10^{-7} (90% C.L.) and the direct annihilation Br(e+einvisible)2.1×108Br(e^+e^-\to invisible)\leq 2.1 \times 10^{-8} (90% C.L.) could be set.Comment: 17 pages, 7 figures, added references, fixed limit on millicharged particles and changed two plots accordingl

    Search for invisible decays of sub-GeV dark photons in missing-energy events at the CERN SPS

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    We report on a direct search for sub-GeV dark photons (A') which might be produced in the reaction e^- Z \to e^- Z A' via kinetic mixing with photons by 100 GeV electrons incident on an active target in the NA64 experiment at the CERN SPS. The A's would decay invisibly into dark matter particles resulting in events with large missing energy. No evidence for such decays was found with 2.75\cdot 10^{9} electrons on target. We set new limits on the \gamma-A' mixing strength and exclude the invisible A' with a mass < 100 MeV as an explanation of the muon g_\mu-2 anomaly.Comment: 6 pages, 3 figures; Typos corrected, references adde
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