Discovery of a narrow resonance state of the system K S K S at mass 1520 MeV

Data are presented which indicate the existence of a previously unknown narrow resonance near mass 1520 MeV, discovered while analyzing the system K _S K _S . The data were obtained at ITEP using the 6-m magnetic spectrometer in a beam of 40-GeV negative particles. The resonance is observed in π⁻ p and K ⁻ p interactions with a total statistical confidence of not less than 5 standard deviations. The width of this state is comparable to the mass resolution of the spectrometer (∼5 MeV). The mass is 1521.5±2.5 MeV. Estimates of the product σ·BR (K _S K _S ) give ∼5.0 nb in π⁻ p interactions and ∼250 nb in K ⁻ p interactions. From the fact that the production cross section of this resonance in the K ⁻ beam is approximately 50 times greater than the production cross section in the π⁻ beam, it can be concluded that this new state belongs to a system of mesons with hidden strangeness. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 4, 242–246 (25 August 1999)     

Discovery of a narrow resonance at 1070 MeV in the system of two K S mesons

Results are presented that were obtained by studying the previously unknown narrow resonance of mass about 1070 MeV. This state was discovered in the system of two K _S mesons. The experimental data subjected to the analysis here come from the 6-m spectrometer created at the Institute of Experimental and Theoretical Physics (ITEP, Moscow) and irradiated with a 40-GeV beam of negatively charged pions from the U-70 accelerator at the Institute for High Energy Physics (IHEP, Protvino) with the aim of studying π ^? p and π ^?C interactions. At the respective maximum, there are 69 events, the statistical significance being not less than six standard deviations. The mass and width of the observed meson are M = 1072.4 ± 0.8 MeV and Γ = 3.5 _+1.5 ^?1.0 MeV, respectively, the product of the cross section for its formation and the relevant branching ratio being not less than 20 nb. The preferable J ^PC assignment for this resonance is 0⁺⁺. Its extraordinary small width has no satisfactory theoretical explanation.     

Observation of a narrow feature at 1545 MeV in the system of two K S mesons

Preliminary results of examining the system of two K _S mesons in the region of comparatively high transferred momenta are reported. The events were observed in the π^? p interactions at an energy of 40 GeV on the ITEP 6-m magnetic spectrometer with a neutral trigger. At transferred momenta |t|>0.5 GeV², a maximum with width Γ?10 MeV was observed in the K _S K _S system at a mass of 1545 MeV with statistical significance of no less than 6 standard deviations. This phenomenon can be interpreted as the manifestation of a resonance with the indicated parameters.     

Resonance behavior of a K S K S system near the mass 1775 MeV

The preliminary results of an investigation of a system of two K _S mesons in the mass interval 1600–1950 MeV are reported. The events were obtained on a 6-m magnetic spark spectrometer at ITEP in π ⁻ p interactions at 40 GeV, using a neutral trigger which suppressed both charged particles and γ rays. A peak of width ≃30 MeV with statistical significance not lower than six standard deviations is observed with momentum transfer selection |tu|0.23 GeV² near the mass 1775 MeV of the K _S K _S system. The observed phenomena can be interpreted as the existence of one resonance with the indicated parameters, or two narrower resonances. In the latter case, their masses are 1768±1.5 and 1787±1.5 MeV. The widths of these states are comparable to the mass resolution of the spectrometer (∼5 MeV). Estimates of the product σ ⋅BR(K _S K _S ) give ∼1.5 and 2.5 nb, respectively, for the first and second states. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 10, 727–731 (25 November 1998)     

Observation of a spin 4 boson resonance at 2050 MeV

We report the observation of a spin 4 resonance from the analysis of the reaction π^?p→ K⁺K^?n. The mass and width of the h-meson were determined to be 2050 MeV and 225 MeV. The quantum numbers are J^P = 4⁺, C = +1 and very probably I^G = 0⁺.     

Remarks on an s-wave Kπ resonance at 1360 MeV

The $\text{K}{}^{\mathrm{O}}\text{π}{}^{\mathrm{?}}\text{and K}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$ mass distributions obtained from a K^?p experiment at 5.5 GeV/c are used to study the recent suggestion of an s-wave Kπ resonance at 1360 MeV. Using a model including $\text{I =}\text{3}\text{2}$ s- and p- wave and $\text{I =}\text{1}\text{2}$, s-, p- and d-wave amplitudes, we analyze the spherical harmonic moments 〈Y_l⁰〉 of the Kπ decay angular distribution in the K¹ (1420) mass region and obtain the result that the reported mass of 1360 MeV does not necessarily represent the resonance position and is influenced by cuts made in the Kπ decay angle.     

Observation of a narrow enhancement at 1940 MeV

A narrow enhancement is observed in states produced inclusively in proton-proton interactions at 93 GeV. The mass 1940 ± 1 MeV is consistent with that of the S(1936).     

Observation of Bs production at the Y(5S) resonance

Using the CLEO detector at the Cornell Electron Storage Ring, we have observed the Bs meson in e+e- annihilation at the Y(5S) resonance. We find 14 candidates consistent with Bs decays into final states with a J/psi or a Ds(*)- . The probability that we have observed a background fluctuation is less than 8 x 10(-10) . We have established that at the energy of the Y(5S) resonance Bs production proceeds predominantly through the creation of Bs*Bs* pairs. We find sigma(e+e- --> Bs*Bs*) = [0.11(-0.03))(+0.04)(stat) +/- 0.02(syst)]nb , and set the following limits: sigma(e+e- --> BsBs)/ sigma(e+ e- --> Bs*Bs*) <0.16 and [sigma(e+e- --> BsBs*) + sigma(e+e- --> Bs*Bs)]/sigma(e+e- -->Bs*Bs*) < 0.16 (90% C.L.). The mass of the Bs* meson is measured to be M(Bs*) = [5.414+/- 0.001(stat) +/- 0.003(syst)] GeV/c2 .     

Evidence for a spin-5 boson resonance at 2300 MeV

Evidence is given for the existence of a spin-5 boson resonance from the analysis of the reaction π^?p→K⁺K^?n at 62 GeV incident momentum. A simplified amplitude analysis with a Breit-Wigner ansatz leads to a mass 2307 ± 6 MeV and a width of 245 ± 20 MeV. The quantum numbers of the resonance are J^P = 5^?, C = ?1, and very probably I^G = 1⁺.     

Observation of a resonance in the KSp decay channel at a mass of 1765?MeV/c2

We report on the observation of a K_Sp resonance signal at a mass of 1765 ± 5 MeV/c ², with intrinsic width Γ = 108 ± 22 MeV/c ², produced inclusively in Σ^--nucleus interactions at 340 GeV/c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region x_F>0.7, in this region its production cross section rises approximately linearly with (1-x_F), reaching BR(X→K_Sp)dσ/dx_F=(5.2±2.3)μb per nucleon at x_F=0.8. The hard x_F spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a Σ^*+ state. No corresponding peaks were observed in the K^-p and Λπ^± mass spectra. PACS 25.80.-e; 13.60.Rj; 14.20.Jn     

Observation of stochastic resonance in a monostable magnetic system

A stochastic resonance on mixed harmonics is observed experimentally in a monostable magnetic system. The curve of the stochastic resonance at higher-order harmonics in systems with a weak nonlinearity is calculated. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 10, 788–792 (25 May 1997)     

7 MeV注入剥离膜系统设计

设计了一台注入能量为7 MeV的快循环同步加速器剥离膜装置,介绍了主体结构设计及高精度换膜运动结构,实现膜片精确定位及在线换膜功能。针对注入参数对膜片开展分析计算,分析了7 MeV的负氢离子束注入时相应的碳膜材料的反应截面及不同厚度的剥离效率,给出了膜片厚度的参数选择。对所设计膜片的温升和寿命进行分析,膜片的温升最高点达到755 K,远小于同类的加速器的剥离膜温度,具有更高的寿命和可靠性。     

Inclusive K(S);(0)K(S);(0) resonance production in ep collisions at HERA

Inclusive K_{S};{0}K_{S};{0} production in ep collisions at the DESY ep collider HERA was studied with the ZEUS detector using an integrated luminosity of 0.5 fb;{-1}. Enhancements in the mass spectrum were observed and are attributed to the production of f_{2}(1270)/a_{2};{0}(1320), f_{2};{'}(1525) and f_{0}(1710). Masses and widths were obtained using a fit which takes into account theoretical predictions based on SU(3) symmetry arguments, and are consistent with the Particle Data Group values. The f_{0}(1710) state, which has a mass consistent with a glueball candidate, was observed with a statistical significance of 5 standard deviations. However, if this state is the same as that seen in gammagamma-->K_{S};{0}K_{S};{0}, it is unlikely to be a pure glueball state.     

The 19.7 MeV resonance in the system 16O + 12C

The 19.7 MeV structure in the system ¹²C + ¹⁶O is investigated by measuring angular distributions and excitation functions for elastic and inelastic scattering with very high resolution. From a quasi phase shift analysis, it is deduced that the structure is a true resonance with J^π = 14⁺. The deduced small elastic partial width indicates that the structure of this state is intermediate between a molecular and a compound state.     

Observation of a baryon resonance with positive strangeness in K + collisions with Xe nuclei

The status of our investigation of low-energy K ⁺Xe collisions in the xenon bubble chamber DIANA is reported. In the charge-exchange reaction K ⁺Xe → K ⁰ pXe′, the spectrum of K ⁰ p effective mass shows a resonant enhancement with M=1539±2 MeV/c ² and Γ≤9 MeV/c ². The statistical significance of the enhancement is near 4.4σ. The mass and width of the observed resonance are consistent with expectations for the lightest member of the antidecuplet of exotic pentaquark baryons, as predicted in the framework of the chiral soliton model.