Study of radiation background at the north crossing point of the BEPCⅡ in collision mode

Understanding the radiation background at the north crossing point (NCP) in the tunnel of BEPCII is crucial for the performance safety of the High Purity Germanium (HPGe) detector, and in turn of great significance for long-term stable running of the energy measurement system. Therefore, as the first step, a NaI(Tl) detector is constructed to continuously measure the radiation level of photons as background for future experiments. Furthermore, gamma and neutron dosimeters are utilized to explore the radiation distribution in the vicinity of the NCP where the HPGe detector will be located. Synthesizing all obtained information, the shielding for neutron irradiation is studied based on model-dependent theoretical analysis.     

Study of the Process $${e}^{{+}}{e}^{{-}}{\to}{\eta\pi}^{{0}}{\gamma}$$ in the Cossision-Energy Range of $$\sqrt{{s}}{=}{1.05{-}2.00}$$ GeV

Physics of Atomic Nuclei - The process $$e^{+}e^{-}\to\eta\pi^{0}\gamma$$ is studied in the range of center-of-mass (c.m.) collision energies between 1.05 and 2.00 GeV on the basis of data...     

Measurement of the Cross Section for the Process $${e^{+}e^{-}}{\to}{K}^{{+}}{K}^{{-}}{\pi}^{{0}}$$ with the SND Detector at Collision Energies of $$\sqrt{{s}}{=}{1.3{-}2.0}$$ GeV in the Center-of-Mass Frame

Physics of Atomic Nuclei - In an experiment with the SND detector at the VEPP-2000 $$e^{+}e^{-}$$ collider, the cross sections for the processes $$e^{+}e^{-}\to K^{+}K^{-}\pi^{0}$$ and...     

How learn the branching ratio X(3872) \to D*^0 \bar D^0 + c.c.

Enfant terrible of charmonium spectroscopy, the resonance X(3872), generated a stream of interpretations and ushered in a new exotic XYZ spectroscopy. In the meantime, many (if not all) characteristics of X(3872) are rather ambiguous. We construct spectra of decays of the resonance X(3872) with good analytical and unitary properties which allows to define the branching ratio of the \(X(3872) \to D*^0 \bar D^0 + c.c.\) decay studying only one more decay, for example, the X(3872) → π⁺π^? J/ψ(1S) decay. We next define the range of values of the coupling constant of the X(3872) resonance with the \(X(3872) \to D*^0 \bar D^0 + c.c.\) system. Finally, we show that our spectra are effective means of selection of models for the resonance X(3872).     

Analysis of the φ → γπη and φ → γπ 0 π 0 decays

We study interference patterns in the φ → (γa ₀+π ⁰ ρ) → γπη and φ → (γf ₀+π ⁰ ρ) → γπ ⁰ π ⁰ reactions. Taking into account the interference, we fit the experimental data and show that the background reaction does not distort the π ⁰ η spectrum in the decay φ → γπη everywhere over the energy region and does not distort the π ⁰ π ⁰ spectrum in the decay φ → γπ ⁰ π ⁰ in the wide region of the π ⁰ π ⁰-system invariant mass, π ^ππ > 670 MeV, or when the photon energy is less than 300 MeV. We discuss the details of the scalar meson production in the radiative decays and note that there are reasonable arguments in favor of the one-loop mechanism φ → K ⁺ K ^? → γa ₀ and φ → K ⁺ K ^? → γf ₀. We also discuss distinctions between the four-quark, molecular, and two-quark models and argue that the Novosibirsk data give evidence in favor of the four-quark nature of the scalar a ₀(980) and f ₀(980) mesons.     

Evidence for ψ' decays into γπ0 and γη

The decays ψ'→γπ(0), γη and γη' are studied using data collected with the BESIII detector at the BEPCII e(+)e(-) collider. The processes ψ'→γπ(0) and ψ'→γη are observed for the first time with signal significances of 4.6σ and 4.3σ, respectively. The branching fractions are determined to be B(ψ'→γπ(0))=(1.58±0.40±0.13)×10(-6), B(ψ'→γη)=(1.38±0.48±0.09)×10(-6), and B(ψ'→γη')=(126±3±8)×10(-6), where the first errors are statistical and the second ones systematic.     

Once more about gauge invariance in <Emphasis Type="Italic">ϕ</Emphasis> → <Emphasis Type="Italic">γπ</Emphasis><Superscript>0</Superscript><Emphasis Type="Italic">π</Emphasis><Superscript>0</Superscript>

It is argued that the realization of gauge invariance condition as a consequent of cancellation between the ϕ → γf ₀ → γπ ⁰ π ⁰ resonance contribution and the ϕ → γπ ⁰ π ⁰ background one, suggested by A.V. Anisovich et al., Yad. Fiz. 68, 1614 (2005), is misleading. The text was submitted by the author in English.     

Effective Lagrangians and IG(JPC)=1?(1?+) exotic resonance state in the VP and the PP channel

For I ^G (J ^PC)=1⁻(1⁻⁺) exotic waves in the reactions ρπ → ρπ, ρπ → ηπ, ρπ → η′π, and ρπ → and in allied reactions, a model is constructed that satisfies the conditions of unitarity and analyticity and which employs, as an input, an “anomalous” nondiagonal VPPP interaction relating the ρπ, ηπ, η′π, and channels. The possibility of obtaining, within this simple field-theoretical model, a resonance behavior of the I ^G(J ^PC)=1⁻(1⁻⁺) amplitudes corresponding to the {10} − and {8} representations of the SU(3) group and their mixing is demonstrated explicitly in the mass range 1.3–1.6 GeV, where data of present-day experiments suggest a rich exoticism. __________ Translated from Yadernaya Fizika, Vol. 65, No. 3, 2002, pp. 579–588. Original Russian Text Copyright ? 2002 by Achasov, Shestakov.     

Measurement of the relative probability of the decay φ → η′γ in the channel η′ → ηπ0π0, η → γγ

The process e ⁺ e ^? → η′γ, η′ → η π⁰π⁰, η → γγ is investigated by an SND detector in experiment on a VEPP-2M equipment with colliding electron-positron beams. The analysis of experimental data yields a value of B(? → η′γ)=(6.7 _?4.2 ^+5.0 ±1.5)×10^?5 for the decay probability. Taking into account a previous measurement of this quantity by an SND detector in the decay channel η′ → π⁺π^?η, one finally obtains B(?→η ′γ)=(6.7 _?2.4 ^+2.8 ±0.8)×10^?5.     

S wave of pion-pion scattering from data on the reaction π?p → π0π0n

The results of recent experiments performed at KEK, Brookhaven National Laboratory, the Institute for High-Energy Physics (Protvino), and CERN to study the reaction π ⁻ p → π ⁰ π ⁰ n are analyzed in detail. For S-wave pion-pion scattering in the channel of isospin I=0, new data are obtained for the phase shift δ ₀ ⁰ and the inelasticity parameter η ₀ ⁰ . Difficulties that arise in using, for the amplitudes of the S and D waves of the final π ⁰ π ⁰ system, physical solutions selected on the basis of partial-wave analyses are discussed. It is noteworthy that other solutions are preferable in principle in the region of the invariant mass m of the π ⁰ π ⁰ system above 1 GeV. With the aim of clarifying the situation and further studying the properties of the f ₀(980) resonance, it is proposed to perform, in the reaction π ⁻ p → π ⁰ π ⁰ n, an especially careful examination of the m region in the vicinity of the threshold. __________ Translated from Yadernaya Fizika, Vol. 67, No. 7, 2004, pp. 1380–1391. Original Russian Text Copyright ? 2004 by Achasov, Shestakov.