Приведены результаты измерений временного и энергетического разрешений для четырех прототипов электромагнитного калориметра PHOS эксперимента ALICE на Большом адронном коллайдере ЦЕРН. Каждый из прототипов состоит из девяти одинаковых детектирующих элементов, собранных в виде матрицы 3 × 3. Основой детектирующего элемента является неорганический сцинтиллирующий кристалл вольфрамата свинца PbWO 4 длиной 180 мм с поперечным сечением 22 × 22 мм 2 , просматриваемый с торца фотодетектором. В качестве фотодетекторов использовались лавинные фотодиоды и кремниевые фотоумножители различной чувствительной площади (Hamamatsu, Япония). Измерения проведены при температуре 17.5°C на электронной компоненте вторичных пучков частиц протонного синхротрона PS в ЦЕРН в диапазоне импульсов от 1 до 10 ГэВ/ с .

— The time and energy resolutions were measured for four prototypes of the PHOS electromagnetic calorimeter for the ALICE experiment at the Large Hadron Collider at CERN. Each prototype was made up of nine identical detection elements assembled as a 3 × 3 array. The detection element was based on a lead tungstate (PbWO 4 ) scintillating crystal with a length of 180 mm and a cross section of 22 × 22 mm 2 , which was viewed from its end face by a photodetector. Avalanche photodiodes and silicon photomultipliers with different active areas (Hamamatsu, Japan) were used as photodetectors. The measurements were made with the electron component of secondary particle beams of the PS proton synchrotron at CERN in the momentum range of 1−10 GeV/ c at a temperature of 17.5°C.

It is shown that an increase in the area of photodetectors allows the PHOS electromagnetic calorimeter of the ALICE experiment to operate at room temperature with better spectrometric characteristics. The linearity of the calorimeter response has been investigated in the 1–110 GeV energy range using both Hamamatsu S8664-1010 avalanche photodiodes with a large area (10 × 10 mm2) and arrays of MPPC Hamamatsu S12572-015C silicon photomultipliers with a sensitive area of 6 × 6 mm2. The calorimeter based on avalanche photodiodes is linear in the energy range under investigation compared to a calorimeter composed of silicon-photomultiplier arrays.

The use of S12572 MPPC silicon photomultipliers (Hamamatsu) for improving the timing characteristics of the PHOS electromagnetic calorimeter in the ALICE experiment at CERN is described. It is shown that by introducing an additional photodetector, that is, a silicon photomultiplier, it is possible, without worsening the energy resolution, to significantly improve the time resolution of the PHOS spectrometer from the current values of 3–4 ns to 150–200 ps.

The light radiation from various internal targets at the nuclotron can be utilized for the operative control and time optimization of the interaction intensity of the beam. The examples presented in the paper illustrate information about the space characteristics of the circulating beam during one cycle of the accelerator run at the stages of injection, acceleration and during the physical experiments, respectively.

The OZI rule have been tested in a number of experiments in a wide interval of energies. It was found that the rule is fulfilled well, within few percent of accuracy. The results of experiments with stopped antiprotons at LEAR (CERN), where unexpected large violation (by a factor 3-70) of the OZI rule was found, were quite surprising. Later experiments found strong violation of the OZI rule not only in antiproton annihilation but also in reactions with protons and pions. In the review we consider the phenomenology of the OZI rule, to what extent it is valid in the hadron interactions. The experimental evidences of the large OZI violation are discussed. The polarized strangeness model and its explanation of the large OZI violation is discussed, the review of other theoretical models is given.

The SPIN@U-70 experiment plans to measure the one-spin analyzing power A. for 70 GeV proton-proton elastic scattering at large P-perpendicular to(2) values of 1 to 12 (GeV/c)(2). The Michigan frozen NH3 polarized proton target (Solid PPT) should later be installed in the Channel 8 extracted beam-line of the 70 GeV U-70 accelerator in IHEP, Protvino. The forward-scattered protons are detected by small scintillation counters placed at about 9 m from the PPT, while the recoil-scattered protons are detected by a 35-m-long focusing magnetic spectrometer, with a 12 degree vertical bend, placed at 30 degrees to the beam. A tune-up run for testing the beam and the spectrometer, using a polyethylene target was carried out in April 2002 at IHEP. The layout and the results of the test run are presented.

The light response of a BGO crystal has been measured for particles Z=1–8, A=1–16 in the energy range ∼2–60AMeV. The reaction products are identified by a ΔE(Si)−E(Sci/PD) telescope. The position of the jump in the value of the signal from the PD at the punch-through points is used to calibrate both the ΔE(Si) and E(Sci/PD) scales in MeV. The dependence of the light output on the energy E, ion atomic number Z and mass A is parameterized by the power law relation, L(Z,A,E)=a1(Z,A)Ea2(Z,A). The parameters a1 and a2 have a smooth dependence on Z for all three crystals. The mass dependence of a1,a2 is deduced as a simple analytical expression. The systematics of these parameters is presented for BGO, CsI(Tl) and GSO(Ce) scintillators as a function of Z,A. Calculations of the response function, based on the Murray–Mayer model provide an excellent description of the shape of L(Z,A,E) versus E dependence, but show some deviations in the individual ion normalization constant for the BGO and GSO(Ce) scintillators.

Mass spectra of the reaction (p,2p) at the beam energy 500 MeV on nuclei C,Al,Cu and Pb were measured on two-armed nonmagnetic scintillation spectrometer (candlepower - 0.2 sr, mass allowance - 4 MeV), which is lokated on the TRIUMF cyclotron (Canada). Observable anomalies in these spectra can be stipulated by forming of two-nucleon resonance states.

The research of abnormal phenomena in the spectra of the particles effective mass in nucleon-nucleon and nucleon-nucleus interactions is of great interest. To the present time in scientific centers of CIS, France, Germany, USA, Japan and etc. a lot of studies with the purpose of baryon structure discovering in the two-nucleon system have been executed. Obtained results, however, are not convincing because of the presence of both numerous indications on dinucleon resonances existence in the wide range of effective mass (from the sum of two nucleon masses to the value ~ 2.9 GeV), and experiments, which do not confirm the production of such structures in nucleon systems [4]. These facts force us to search for a new possibility for discovering of di-baryon resonance [5] and to make higher demands to the measurement conditions in traditional experiments. With the purpose of dibaryon structures research in mass spectra of the reaction A(p, 2p)X, whose investigation were carried out at the energy of polarized proton

The reaction products emitted in the 14N(45AMeV)+(CH2/CD2) interactions are identified by a ΔE(Si)–E(Scintillator/Photodiode) telescope by the conventional ΔE–E method. The position of “jumps” in the amplitude of the photodiode signal for ions passing through the scintillator (Sci) is used to calibrate on-beam both the ΔE and the Sci/PD scales in MeV. The accuracy of an absolute energy calibration is better than 2.3% and 1.8% for CsI(Tl) and GSO(Ce) detectors, respectively. It is defined mostly by the correctness of the range-energy relations of ions in the Si and Sci crystals. The light response function, L(E,Z,A), of isotopes up to Z(A)=8(16) in the range of energy ∼(2.5–60)AMeV is extracted. The effects of doping concentration and pulse shaping on the light response are analyzed. The validity of the existing empirical light-energy relations is checked in a wide interval of ion energies and a new power law relation is proposed. Calculations of the response function based on the Murray–Mayer model are found to be in excellent agreement with experimental data for the CsI(Tl) crystal.

Data taken by the DELPHI experiment at centre-of-mass energies of 183 GeV and 189 GeV with a total integrated luminosity of 212 pb −1 have been used to search for the supersymmetric partners of the electrons, muons, and taus in the context of the Minimal Supersymmetric Standard Model (MSSM). The decay topologies searched for were the direct decay (˜ ℓ → ℓ ˜ χ 0 1), producing acoplanar lepton pairs plus missing energy, and the cascade decay (˜ ℓ → ℓ ˜ χ 0 2 → ℓγ˜χ 0 1), producing acoplanar lepton and photon pairs plus missing energy. The observed number of events is in agreement with Standard Model predictions. The 95% CL excluded mass limits for selectrons, smuons and staus are m ˜ e ≤ 87 GeV/c 2 , m ˜ µ ≤ 80 GeV/c 2 and m ˜ τ ≤ 75 GeV/c 2 , respectively, for values of µ=-200 GeV/c 2 and tanβ=1.5.

The reaction (p) over bar p --> K+K- pi(0) was analysed for antiproton annihilations at rest at three hydrogen target densities. A strong dependence of the (p) over bar p --> phi pi(0) yield on the quantum numbers of the initial state is observed. The branching ratio of the phi pi(0) channel from the S-3(1) initial state is more than 15 times larger than the one from the P-1(1) state. A large apparent violation of the OZI rule for tensor meson production from (p) over bar p-annihilations from the P-waves (1(++) + 2(++)) is observed: R-exp(f(2)'pi(0)/f(2)pi(0)) = (149 +/- 20) . 10(-3), significantly exceeding the OZI-rule prediction R = 16 . 10(-3). (C) 1998 Elsevier Science B.V. All rights reserved.

The OBELIX spectrometer, studying at the Low Energy Antiproton Ring (LEAR) of CERN the <(N)over bar N> annihilation, has collected annihilation data with very low momentum (p) over tilde (approximate to 50MeV/c). The results of the spin-parity analysis on the <(p)over bar p> annihilation into four and five pions are briefly described.