Institute Of High Energy Physics Research Articles

High-energy interactions in the region of extreme multiplicities

Hadron and nuclear interactions at high energies in the region of extreme multiplicities (much higher than mean multiplicities) are reviewed. Collective phenomena such as Bose-Einstein condensation, Cherenkov gluon radiation, clustering, and an excess yield of soft photons may manifest themselves in this region. The phenomenological gluon-dominance model developed for describing extreme multiplicities predicts the restrictions on their values and the type of hadronization mechanism and makes it possible to estimate thee size of the hadronization region. The status of the research within the Thermalization project at the U-70 accelerator of the Institute for High Energy Physics (IHEP, Protvino) is reported, and information about searches for new collective phenomena and about studies of known ones in the region of extreme multiplicities is given.

Research trends in neutron activation analysis in nuclear science and technology: a global perspective

This paper quantitatively analyses the growth and development of research in Neutron Activation Analysis (NAA) in terms of publications. As per the International Nuclear Information System (INIS) database during 1993-2007, a total of 6491 publications were published. The highest number of papers in a year (615) was published in 2004. The average number of publications published per year was 432.73. Japan topped the list with 605 publications followed by the USA with 468, Brazil with 449, China with 442, the Russian Federation with 324 and India with 316. The authorship and collaboration trend is towards multi-authored papers. Researchers in Japan, Brazil and China are more inclined to work in larger groups. The highly productive institutions were Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, Brazil with 281 publications; Bhabha Atomic Research Centre, Mumbai, India with 257; Institute of High Energy Physics, Academia Sinica, Beijing, China with 162; and Japan Atomic Energy Agency, Tokai, Ibaraki, Japan with 140. The journals most preferred by the scientists for the publication of papers are the Journal of Radioanalytical and Nuclear Chemistry with 1204 papers, followed by Applied Radiation and Isotopes with 116 papers, and Nuclear Instruments and Methods in Physics Research-A with 84 papers.

Study of K ± → e ± νπ 0 decays at the KMN setup

K± → e±νπ0 decays have been studied using the KMN setup at the Institute for High Energy Physics (Protvino). The experiment has been performed in the 36-GeV/c hadron beams of the IHEP accelerator. The accumulated data allow us to select ∼1.08M candidates for Ke3 decays. Analyzing the Dalitz plot of these events, we estimate the linear slope of the charge form factor to be λ+ = [30.44 ± 0.83(stat.) ± 0.74(syst.)] × 10−3.

Study on cooling process of cryogenic system for superconducting magnets of BEPCII**Supported by the Project of BEPCII

In the upgrade project of the Beijing Electron Positron Collider (BEPCII), three superconducting magnets are employed to realize the goal of two orders of magnitude higher luminosity. A cryogenic system with a total capacity of 0.5 kW at 4.5 K was built at the Institute of High Energy Physics (IHEP) to support the operations of these superconducting devices. For preparing the commissioning of the system, the refrigeration process was simulated and analyzed numerically. The numerical model was based on the latest engineering progress and focused on the normal operation mode. The pressure and temperature profiles of the cryogenic system are achieved with the simulation. The influence of the helium mass flow rates to cool superconducting magnets on the thermodynamic parameters of their normal operation is also studied and discussed in this paper.

PANDA electromagnetic calorimeters

PANDA is a challenging experimental setup to be implemented at the high-energy storage ring (HESR) at the international facility FAIR, GSI (Germany). PANDA physics program relies heavily on the capability to measure photons with excellent energy, position and timing resolution. For this purpose PANDA proposed to employ electromagnetic calorimeters using two different technologies: compact crystal calorimeter cooled to - 25 ∘ C around target and lead–scintillator sandwich calorimeter with optical fibers light collection (so-called shashlyk calorimeter) in the forward region. Institute for High Energy Physics (IHEP) PANDA group reports on two types of measurements performed at IHEP, Protvino: radiation hardness of the PWO crystals at - 25 ∘ C and testbeam studies of the energy and position resolution of the shashlyk calorimeter prototype in the energy range up to 19 GeV.

A drift tracker of the SVD-2 setup

The design and the characteristics of a drift tracker for the SVD-2 setup at the U-70 accelerator of the Institute for High Energy Physics (Protvino, Russia) are described. The drift tracker has been developed to improve the quality of track reconstruction in high-multiplicity events. It is composed of 2304 drift tubes with a diameter of 6 mm and a sensitive region 500–900 mm long. The distance between a track and the anode wire is determined from the drift time. The coordinate resolution and the detection efficiency of the tubes have been determined from the data of the accelerator run in 2006.

A dedicated high-speed trigger generation processor for selecting single particle decay events using coordinate signals from hodoscopes of scintillation counters

A dedicated high-speed trigger generation processor is described. This processor is used to select a single particle (K-meson) decay event on the decay base of the OKA experimental setup at the Institute for High Energy Physics. Useful events are selected by coordinate signals from hodoscopes of scintillation counters with the aid of preprogrammable memory lookup tables. The trigger generation time is <150 ns. A set of 64-channel ЛЭ-76 register modules and a decision-taking ЛЭ-79 module, all based on Altera FPGA technology, are included as components of the processor unit.

Investigation of resonance structure in the system of two Ks-mesons in the mass region around 1450 MeV

Results are presented that were obtained by studying the narrow resonance of mass about 1450 MeV. This state was discovered in the system of two Ks-mesons. The experimental data subjected to the analysis here come from the 6-m spectrometer (MIS ITEP) 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, Serpukhov) with the aim of studying π−p and π−C interactions. The statistical significance is better than six standard deviations. The mass and width of the observed meson are M = 1449.5 ± 2.0 ± 3.0 MeV and s = 7.5 ± 1.5 MeV, respectively, the product of the cross section for its formation and the relevant branching ratio 25-5+25 (stat.) ± 4(syst.) nb. The spin-parity Jpc is 0++ or 2++. Seeing its very narrow width this resonance is likely to be cryptoexotics (see [1], [2] for details).

A study of the RAMPEX electromagnetic calorimeter stability

The short- and long-term stabilities of the electromagnetic calorimeter for the RAMPEX experiment at the accelerator of the Institute for High Energy Physics has been investigated. Brief descriptions of the experimental setup, the calorimeter, and the monitoring system of the calorimeter are provided. A procedure for measuring the stability is described, and results of these measurements are presented. The necessity to study the stability has been dictated by the weakness of the effect in measuring the single-spin asymmetry of hadron production in the inclusive reaction π− = p↑(↓) → h + X at energies of 40 and 70 GeV/c.

E-Os dating of the porphyry copper deposits in southern Gangdese metallogenic belt, Tibet

† Key Laboratory of Lithospheric Tectonics and Lithoprobing Technology, China University of Geosciences, Ministry of Education, China, Beijing, 100083, CHINA ‡ China National Research Center of Geoanalysis, Beijing 100037, CHINA § Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, CHINA ¶ Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100080, CHINA

Solution structure of human DESR1, a CSL zinc‐binding protein

Solution structure of human DESR1, a CSL zinc-binding protein Fangming Wu, Jiahai Zhang, Jianping Sun, Hongda Huang, Peng Ji, Wangsheng Chu, Meijuan Yu, Feifei Yang, Ziyu Wu, Jihui Wu,* and Yunyu Shi* 1National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China 2 Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China

Longitudinal instability of a continuous beam in a proton synchrotron

The results of a calculation of the threshold for longitudinal coherent instability of a continuous beam circulating in a proton synchrotron and constant energy are presented. A beam in an intermediate state — not bunched into bunches but not uniform over the azimuth — is said to be continuous. Such a beam moves outside (possibly, near) empty rf separatrices of the longitudinal sinusoidal electric field and has a ribbon portrait in the longitudinal phase plane. The computational method is used for the U-70 synchrotron at the Institute of High Energy Physics, where in the course of stochastic slow extraction of a circulating beam is continuous in the sense indicated. It bends around empty separatrices of the 200-MHz accelerating field and for several seconds interacts with the electromagnetic fields of the working oscillations of the disconnected resonators of the main accelerating system with frequency 5.5–6 MHz, which can result in a loss of longitudinal stability.

A new gadolinium-loaded liquid scintillator for reactor neutrino detection

A high flash point, low toxicity gadolinium-loaded liquid scintillator (Gd-LS) has been developed for the detection of reactor neutrino. Carboxylic acid 3,5,5-trimethylhexanoic acid is used as complexing ligand to form organo-complex with gadolinium chloride, and 2,5-diphenyloxazole (PPO), and 1,4-bis[2-methylstyryl]benzene (bis-MSB) are used as primary fluor and wavelength shifter, respectively. The scintillator base is linear alkyl benzene (LAB). The Gd-LS prepared with such recipe has long attenuation length, high light yield and long-term stability. Eight hundred liters of Gd-LS (1 g/L Gd) was synthesized and tested in a prototype detector at Institute of High Energy Physics. Preliminary results of the obviously peaks corresponding to neutron captured by H and Gd give an additional evidence that such Gd-LS are very promising for anti-neutrino detection.

Single-spin asymmetry for high-p T charged hadrons at negative x F in proton-nucleus collisions at an energy of 40 GeV

The transverse single-spin asymmetry was measured for charged hadrons ({pi}{sup {+-}}, K{sup {+-}}, p, p-bar) produced in proton-nucleus collisions. The measurements were performed with the aid of the FODS-2 spectrometer by using a 40-GeV polarized proton beam from the accelerator of the Institute for High Energy Physics (IHEP, Protvino) and carbon and copper nuclear targets. The data subjected to the analysis in the present study were obtained for c.m. angles in the range 95{sup o}-112{sup o} in the vicinity of the central region (-0.08 < x{sub F} < -0.06, 0.7 < p{sub T} < 3.4 GeV/c). The analyzing power is found to be only slightly dependent on the mass number of the target nucleus. The basic results obtained by measuring the single-spin asymmetry at three values of the particle-detection angle are discussed.

Discovery of a 1731-MeV narrow resonance

Results obtained by studying a previously unknown narrow meson of mass about 1731 MeV are presented. This state was found in a system of two K S mesons. The experimental-data set subjected to the present analysis was obtained with a 6-m spectrometer of the Institute of Theoretical and Experimental Physics (ITEP, Moscow). The statistical sample of event of double K S -meson production was accumulated in π− p interactions by using a beam of 40-GeV pions from the U-70 accelerator of the Institute of High Energy Physics (IHEP, Protvino). There are 58 events at the respective maximum, its statistical significance being close to six standard deviations. The parameters of the observed meson are the following; the mass is M = 1731 ± 2.5 MeV, the width is σ = 3.2 ± 2 MeV, and the product of the production cross section and the respective branching ratio is not less than 20 nb. The fact that the observed meson is extremely narrow does not have a satisfactory theoretical explanation.

Measurement of the analyzing power of high-transverse-momentum charged hadrons in proton-nucleus collisions at an energy of 40 GeV

The transverse single-spin asymmetry was measured for charged hadrons (π ±, K ±, p, $$\bar p$$ ) produced in proton-nucleus collisions. The measurements were performed at the FODS-2 spectrometer by using a polarized proton beam that was accelerated to an energy of 40 GeV at the accelerator of the Institute for High Energy Physics (IHEP, Protvino) and which was made to hit carbon and copper nuclear targets. The data in question were obtained in the range of c.m. angles between 73° and 94° near the central region (−0.01 < x F < 0.27, 0.7 < p T < 3.6 GeV/c). The single-spin asymmetry for π + and K + mesons is significant at high values of p T and moderately small positive values of x F. The analyzing power for other hadrons (π −, K −, p, $$\bar p$$ ) is compatible with zero in the p T range studied here. The dependence of the analyzing power on the mass number of the target nucleus is insignificant.

Observation of the f 2(1525) resonance in the ηη system produced in K − p interactions at a momentum of 32.5 GeV/c

The reaction K − p → ηη(Λ/Σ0) at a momentum of 32.5 GeV/c was studied for the first time. The experiment was performed by using the GAMS-4π spectrometer at the 70-GeV accelerator of the Institute for High Energy Physics (IHEP, Protvino). The f 2(1525) resonance was observed in the effective-mass spectrum of the ηη system at a low background level. The cross section for f 2(1525) production was measured. The branching ratio for f 2(1525)-meson decay to ηη and K \(\bar K\) was found to be R = 0.119 ± 0.015(stat.) ± 0.036(syst.), which is in agreement with the world-average value.

A vertex microstrip detector of the SVD setup for experiments on the IHEP accelerator

A precision vertex microstrip detector has been developed for the spectrometer with a vertex detector (SVD) setup on which the properties of hadrons and short-lived unstable particles are investigated on the accelerator of the Institute for High Energy Physics. The structure and the design of the main detector components—microstrip sensors and an active target—are presented, as well as techniques for manufacturing them. The readout electronics, the data acquisition system, and its software are also described. The accuracy in determining the vertex position is 70–250 µm along the beam axis and 8–15 µm in a transverse direction at a throughput of 500–1000 events/s.

Single-spin asymmetry for charged hadrons produced in proton-nucleus collisions at 40 GeV for c.m. production angles in the range 40°–79°

The transverse single-spin asymmetry for charged hadrons ({pi}{sup {+-}}, K{sup {+-}}, p, p-bar) produced in proton-nucleus collisions was measured for c.m. production angles in the range 40{sup o}-79{sup o}. The measurements were performed with the FODS-2 setup by using a 40-GeV polarized proton beam originating from the accelerator of the Institute for High Energy Physics (Protvino) and hitting carbon and copper nuclear targets. The data in question were obtained in the polarized-proton-fragmentation region (0.0 < x{sub F} < 0.7, 0.6 < pT < 2.5 GeV/c). In agreement with data obtained at other energies, the single-spin asymmetry for {pi}{sup {+-}} mesons is significant at high x{sub F}. For the first time, a sizable analyzing power, which changes sign at x{sub F} = 0.43, is observed for protons. The dependence of the analyzing power on the target-nucleus mass is insignificant.

PRELIMINARY COMMISSIONING OF SUPERCONDUCTING MAGNETS AND CRYOGENIC SYSTEM OF BEPC II

A helium cryogenic system with cooling capacity of 1 kW at 4.5 K was set up at Institute of High Energy Physics, Chinese Academy of Sciences, Beijing. This helium refrigerating system is dedicated for the cooling of two superconducting radio frequency (SRF) cavities, two interaction region superconducting collision quadrupole (SCQ) magnets, a detector superconducting solenoid magnet (SSM), which are the key items of the upgrade project of Beijing Electron-Positron Collider (BEPC II). Commissioning with the detector and SCQ magnets was carried out, which will be introduced in this paper. The cryogenic system shows very robust as SSM quench. This paper presents the overall status and some test results of superconducting and cryogenic system.