Search

An experiment to search for the bound state of η meson in nuclei has been performed at COSY, Juelich using the ENSTAR detector and Big Karl magnetic spectrometer. Reaction (p,3 He ) on 27 Al target has been used to search for the η-mesic nucleus 25 Mg η in the missing mass distribution from the measured 3 He particles. A preliminary figure of 1.5 nb for the upper limit of the formation cross section of η-nucleus bound state has been determined.

There are three main methods used in individual monitoring: radiographic films, thermoluminescence (TL) and optically stimulated luminescence (OSL). Distinguishing between static (e.g. by leaving it accidentally or purposely in the radiation field) and dynamic exposures can be almost routinely performed for radiographic and OSL methods but is still unsolved for TL detectors. The main aim of this work is to develop a method for identifying static exposures of standard TL detectors at doses which are typical of radiation protection. For this purpose, a new TLD reader equipped with a CCD camera was developed to measure the two-dimensional signal map and not only the total light emitted (as is performed with standard photomultiplier-based TL readers). Standard MCP-N (LiF:Mg,Cu,P) TL pellets of 4.5 mm diameter and 0.9 mm thickness were installed in the standard Rados TL personal badges with special, non-uniform filters and exposed statically to 33 keV X-ray beams at three angles: 0 degrees, 30 degrees and 60 degrees. The detectors were readout in the CCD camera reader and 2-D images were collected. The analysis of these CCD images allows the identification of the static exposure cases and partly the angle of incidence at a dose level of 20 mSv.

Sigma+ hyperon production was measured at the COSY-11 spectrometer via the p p --> n K+ Sigma+ reaction at excess energies of Q = 13 MeV and Q = 60 MeV. These measurements continue systematic hyperon production studies via the p p --> p K+ Lambda/Sigma0 reactions where a strong decrease of the cross section ratio close-to-threshold was observed. In order to verify models developed for the description of the Lambda and Sigma0 production we have performed the measurement on the Sigma+ hyperon and found unexpectedly that the total cross section is by more than one order of magnitude larger than predicted by all anticipated models. After the reconstruction of the kaon and neutron four momenta, the Sigma+ is identified via the missing mass technique. Details of the method and the measurement will be given and discussed in view of theoretical models., 7 pages, 8 figures, Phys. Lett. B in print, in the second version a minor editorial changes have been made by a native speaking proofreader and a note in proof has been added with an additional reference

Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid--fog phase transition deep inside the spinodal region. The experimental data for p(8.1GeV) + Au collisions are analyzed. It is concluded that the decay process of hot nuclei is characterized by two size parameters: transition state and freeze-out volumes. The similarity between dynamics of fragmentation and ordinary fission is discussed. The IMF emission time is related to the mean rupture time at the multi-scission point, which corresponds to the kinetic freeze-out configuration., 7 pages, 3 Postscript figures, Proceedings of IWM 2005, Catania

The PHOBOS collaboration has studied the pseudorapidity and transverse momentum distributions of charged particles produced in heavy ion collisions. Results from Au+Au collisions at various center-of-mass energies and over a broad range of centrality are presented here. The data are compared to Cu+Cu, p+p and d+Au collisions at corresponding energies and centralities. The data are found to exhibit simple scaling properties such as the observed factorization of collision energy and geometry dependences. The presented data help us distinguish between models of particle production in relativistic heavy ion collisions.

Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid-fog phase transition inside the spinodal region. The exclusive data for p(8.1 GeV) + Au collisions are analyzed within the framework of the statistical model SMM. It is found that the partition of hot nuclei is specified after expansion to a volume equal to V t = (2.6 ± 0.3)V 0. The freeze-out volume is found to be twice as large: V f = (5 ± 1)V 0. The similarity between multifragmentation and ordinary fission is discussed.

Angular distributions for the transitions to the ground and excited states of 12 B from the 12 C( 7 Li, 7 Be) 12 B reaction at 82 MeV were measured. The data were analyzed in the framework of distorted wave born approximation for the direct charge-exchange and coupled reaction channels method for the two-step sequential nucleon transfers. It was shown that the two-step sequential nucleon transfer is the dominant mechanism in the investigated angular range and the direct mechanism becomes important only for small angles ( θ cm 10 ° ).

As an international collaboration PISA (Proton Induced SpAllation) has initiated measurements of total and double differential cross-sections for products of spallation reactions at the proton accelerator COSY in Julich (Germany) in order to study secondary particle production created in structural, window, and target materials by proton beams up to 2.5 GeV incident kinetic energy. In the framework of Spallation Neutron Sources and accelerator-driven systems, residual nuclei (H, He up to intermediate mass fragrments) production cross-sections are of great importance for estimation of damage in target and structural materials. Reliable and comprehensive experimental data, especially for p-energies beyond 1 GeV will serve as benchmarks for code development and validation. Data taken by Bragg curve spectroscopy and silicon detector telescopes for the reaction 1.9 GeV p+Ni(Au) will be discussed and kinetic energy spectra of light ions and intermediate mass fragments will be presented.

Different approaches for the measurement of a relatively small gamma dose in strong fields of thermal and epithermal neutrons as used for Boron Neutron Capture Therapy (BNCT) have been studied with various thermoluminescence detectors (TLDs). CaF(2):Tm detectors are insensitive to thermal neutrons but not tissue-equivalent. A disadvantage of applying tissue-equivalent (7)LiF detectors is a strong neutron signal resulting from the unavoidable presence of (6)Li traces. To overcome this problem it is usual to apply pairs of LiF detectors with different (6)Li content. The experimental determination of the thermal neutron response ratio of such a pair at the Geesthacht Neutron Facility (GeNF) operated by PTB enables measurement of the photon dose. In the experimental mixed field of thermal neutrons and photons of the TRIGA reactor at Mainz the photon dose measured with different types of (7)LiF/(nat)LiF TLD pairs agree within a standard uncertainty of 6% whereas the CaF(2):Tm detectors exhibit a photon dose by more than a factor of 2 higher. It is proposed to determine suitable photon energy correction factors for CaF(2):Tm detectors with the help of the (7)LiF/(nat)LiF TLD pairs in the radiation field of interest.

The dosimetry around the X-ray tube with a needle-like anode (NAXT), developed at the Institute of Nuclear Studies, for interstitial brachytherapy has been performed using (1) dye films (Gafchromic XR-T), (2) large-area thermoluminescent (TL) detectors--prepared either by gluing TL powder onto thin Al foil (so-called planar detectors with spatial resolution of 0.1 mm) and (3) miniature (2 mm diameter and 0.5 mm thick) TL detectors. The measurements were performed in following geometries. (1) Needle inside a PMMA cylinder--the planar TL detector mounted on the surface of the cylinder. (2) Needle inside a thick block of PMMA and TL detector mounted vertically 7 mm from needle axis. TL detectors were read with the planar (2D) thermoluminescence reader, developed at IFJ, with a sensitive CCD (charge couple device) camera. Gafchromic films were evaluated with a system based on Agfa Arcus 1200 scanner and calibrated with X rays (35 kV) filtered with 0.03 mm Mo and with Co-60 photons. The intensity distribution of TL light on the planar detector was calibrated in terms of absorbed dose to water, using (137)Cs gamma-rays. TL planar detectors seem to be a promising tool for 2D dosimetry of miniature X-ray sources. Obtained results for TLDs and Gafchromic films seem to be comparable but differences have been found. Both methods are useful for measurements of dose distribution around the NAXT X-rays source.

In this talk I will review PHOBOS data on charged particle multiplicities, obtained in Au + Au and d + Au collisions at RHIC. The general features of the Au + Au pseudorapidity distributions results will be discussed and compared to those of [Formula: see text] collisions. The total charged particle multiplicity, scaled by the number of participant pairs, is observed to be about 40% higher in Au + Au collisions than in [Formula: see text] and d + Au systems, but, surprisingly at the same level of e+e- collisions. Limiting fragmentation scaling is seen to be obeyed in Au + Au collisions.

Angular distributions of the 11 B + 14 C elastic scattering and inelastic scattering for transitions to a few excited states of 14 C were measured at E lab ( 11 B) = 45 MeV over the full angular range. The data were analyzed within the coupled-channels method. Contributions from one- and two-step transfer reactions were found to be negligible. Quadrupole deformation of the 14 C ground state was deduced to be negative, the deformation of the 8.318 MeV (2 + ) state was found to be similar to that of the ground state. The single particle model calculations reproduced the experimental data for transition to the 6.094 (1 − ) state of 14 C much better than the collective model analysis. The fit to this experimental data set was improved when we took into account reorientation of 11 B in its ground state and considerably enlarged the radius of the potential binding the neutron to the 13 C core. The same procedure was tested against the experimental data for transition to the 1/2 + (3.089 MeV) excited state of 13 C, populated in the 11 B + 13 C scattering at E lab ( 11 B) = 45 MeV, with the similar effect.

The COSY-11 collaboration has conducted experiments aiming at the determination of the excitation function and phase-space population of the p p --> p p eta reaction close to the kinematical threshold. The precise data obtained with the stochastically cooled proton beam of the cooler synchrotron COSY and the high resolution zero-degree magnetic spectrometer allowed for the observation of the significant deviations - in the shape of the excitation function and two-particle invariant masses - from the predictions based on the assumption that the reaction phase space is homogenously populated. Comparison of the shape of the excitation function for the p p --> p p eta and p p --> p p eta-prime reaction allows to distinquish in the model independent way an influence originating from the proton-proton and proton-eta interaction. For the comparison the full data set from experiments performed at COSY and other laboratories is used., Talk given at 10th International Symposium on Meson-Nucleon Physics and the Structure of the Nucleon (MENU 2004), Beijing, China, 29 Aug - 4 Sep 2004, 4 pages, 1 figure, to be published in Int. J. Mod. Phys

We present the construction of a planar drift chamber with wires stretched between two arms of a c-shaped aluminium frame. The special shape of the frame allows to extendthe momentum acceptance of the COSY-11 detection system towards lower momenta without suppressing the high momentum particles. The proposed design allows for construction of tracking detectors covering small angles with respect to the beam, which can be installed and removed without dismounting the beam-pipe. For a three-dimensional track reconstruction a computer code was developed using a simple algorithm of hit preselection., Comment: submitted to Nucl. Instr. & Meth A

Elliptic flow is an interesting probe of the dynamical evolution of the dense system formed in the ultrarelativistic heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC). The elliptic flow dependences on transverse momentum, centrality, and pseudorapidity were measured using data collected by the PHOBOS detector, which offers a unique opportunity to study the azimuthal anisotropies of charged particles over a wide range of pseudorapidity. These measurements are presented, together with an overview of the analysis methods and a discussion of the results., Comment: Presented at Hot Quarks 2004; 7 pages, 6 figures

The positively charged pions produced in proton–proton collisions at a beam momentum of 1640 MeV/c were measured in the forward direction with a high resolution magnetic spectrograph. The missing mass distribution shows the bound state (deuteron) clearly separated from the pn continuum. Despite the very good resolution, there is no evidence for any significant

A brief experimental overview on the close-to-threshold eta meson production in proton-proton interactions is presented and the available observables in measurements with unpolarized and polarized beam and target are discussed., Comment: 4 pages; Presented at Meson 2004: 8th International Workshop on Meson Production, Properties and Interaction, Krakow, Poland, 4-8 June 2004; Submitted to International Journal of Modern Physics A

Angular distributions of the 12C( 11B, 15N) 8Be reaction were measured at the energy Elab(11B) = 49 MeV for the transitions to the ground and 2.94 MeV (2+) excited state of 8Be and to the ground and 5.270 MeV (5/2+) + 5.299 MeV (1/2+), 6.324 MeV (3/2-), 7.155 MeV (5/2+) + 7.301 MeV (3/2+), 7.567 MeV (7/2+) excited states of 15N. The data were analyzed by the coupled-reaction-channel method. The elastic, inelastic scattering and one- and two-step transfers were included in the coupling scheme. The data of the 12C( 11B, 8Be) 15N reaction at Ecm = 9.4-17.8 MeV known from the literature, were also included in the analysis. The mechanism of the 12C( 11B, 15N) 8Be reaction and the optical-model potential parameters for the 15N + 8Be channel were deduced. The energy dependence of the optical-model parameters for the 15N + 8Be channel was obtained.

The production of the Lambda and Sigma0 hyperons has been measured via the pp->pK+Lambda / Sigma0 reaction at the internal COSY-11 facility in the excess energy range between 14 and 60 MeV. The transition of the Lambda/Sigma0 cross section ratio from about 28 at Q

PHOBOS is one of the four heavy ion experiments currently running at the Relativistic Heavy Ion Collider (RHIC). In this paper we will present some of the current results from PHOBOS: the study of charged multiplicity distribution as function of pseudorapidity and centrality at = 19.6, 130 and 200 GeV, a discussion of multiplicity scaling, and a measurement of transverse momentum spectra (pT) of charged hadrons produced in d+Au and Au+Au interactions at = 200 GeV. The dependence of the Au+Au yields as function of centrality is found to be independent of pT. A strong suppression in the Au+Au hadron spectra relative to p at high pT is observed. The spectral shape for d+Au collisions is significantly different from the observations in Au+Au, the yield suppression is not observed in d+Au.

An environmental radiation monitoring system using standard MTS-N (LiF:Mg, Ti) and high-sensitive thermoluminescent LiF:Mg,Cu,P (MCP-N) detectors was applied to control the radiation exposure over the area of the Institute of Nuclear Physics (INP) in Krakow. First environmental measurements using MTS-N detectors began in 1970 at five locations and were continued during the Chernobyl accident at six sites. In March 1987 high-sensitive MCP-N detectors read out in a manual TL reader were first introduced into service at the INP. Since 1992 about 60 locations over an area of the INP were selected for quarterly dose rate measurements, using an automatic TLD system based on MTS-N detectors placed in cards. In 2002 MTS-N detectors were replaced by high-sensitive MCP-N pellets. The dose rate in long-term measurements changed over the last 30 years. The average gamma dose rate over the area of INP in the years 1975–1978 was 63 nGy −1 . After the Chernobyl accident the gamma dose rate increased to 880 nGyh −1 . In December 1986 the dose rate at the location place decreased to 103 nGyh −1 . At present, the average dose rate has returned to the pre-Chernobyl level of about 68 nGyh −1 . Construction and beam tests of a new isochronous cyclotron at the INP resulted in highly enhanced environmental dose rates at several monitored INP sites. In this work results of almost 11 years of environmental indoor and outdoor measurements with thermoluminescent detectors are summarised.

In the dosimetry of boron neutron capture therapy (BNCT) beams, thermoluminescent (TL) detectors are typically applied in phantom measurements to determine the spatial distribution of the gamma ray and neutron dose. Pairs of 6LiF and 7LiF are applied to discriminate between the thermal neutron and gamma ray field components, exploiting the high cross section for (n,alpha) reaction of 6Li. At the Institute of Nuclear Physics (INP) in Kraków (Poland) a prototype TL-based measuring set has been constructed and tested. This set consists of a miniature TL detector (of 2 mm diameter and 0.4 mm thickness) placed inside a miniature container made of non-thermoluminescent 6LiF. The outer dimensions of the set are 4.5 mm diameter and 1.4 mm thickness, enabling its application in place of a thermoluminescence dosemeter pellet in typical phantoms. The detector sets were tested in the BNCT beam of the Studsvik reactor. By exploiting the ratio of TL signals of the unshielded and shielded detectors, it was possible to estimate the contributions of the thermal and epithermal components of the neutron field.

Lithium fluoride thermoluminescent (TL) detectors, with Li-7 isotope and various activators (MTS-7 LiF:Mg,Ti, MTT-7 LiF:Mg,Ti with enhanced Ti concentration and MCP-7 LiF:Mg,Cu,P) were used for dosimetry of heavy charged particles, within the ICHIBAN experiment. The microdosimetric model has been applied to calculate detection efficiency, η, relative to gamma-ray dose, of these detectors after proton and heavy charged particle (HCP) irradiation for ion charges ranging from Z = 1 to Z = 6 and in the energy range from 0.3 to 20 MeV amu - 1 . The calculated ratio η M C P - 7 /η M T S - 7 lies in the range between 0.2 and 1.0 for protons and between 0.2 and 0.4 for HCP with Z> 1. The calculated value of η M T T - 7 /η M T S - 7 for protons was found range between 1.0 and 1.45 and, for Z>1, between 1.3 and 2. These relationships can be applied to derive information about the 'effective LET' in an unknown HCP field and to correct the TLD readings for dose evaluation.

This paper presents the first PHOBOS results on charged particle multiplicity fluctuations measured for Au+Au collisions at the highest RHIC energy within a wide pseudorapidity range of |η| < 3. The dependence on collision geometry is removed in the analysis by using the normalized difference between the number of particles in separate η bins. We compare our data to HIJING model predictions.

The $\eta^\prime$ -meson production in the reaction $pp\rightarrow pp\eta^\prime$ has been studied at excess energies of Q = 26.5, 32.5 and 46.6 MeV using the internal beam facility COSY-11 at the cooler synchrotron COSY. The total cross-sections as well as one angular distribution for the highest Q-value are presented. The excitation function of the near-threshold data can be described by a pure s-wave phase space distribution with the inclusion of the proton-proton final-state interaction and Coulomb effects. The obtained angular distribution of the $\eta^\prime$ -mesons is also consistent with pure s-wave production.

INTRODUCTION Treatment of open abdomen following secondary peritonitis is a challenge for surgery and intensive care units (ICU). The aim of this study was to compare three different concurrent treatment strategies. METHODS Patients suffering an open abdomen following surgery for secondary peritonitis at the Department of General Surgery from 01/01 to 12/03 were investigated. Factor studied: duration of open abdomen, incidence of multi-organ failure, need for surgical revisions, length of stay (LOS) in ICU, nursing requirements (change of dressing/day), survival and integrity of abdominal wall after discharge. Treatment strategies included: open packing (OP), classic vacuum assisted (V.A.C.(R))-therapy with silicone net protection for the intestine (CV) and V.A.C.(R)-therapy with "abdominal dressing" a newly developed meshed polyvinyl wrap (AD). RESULTS 21 patients were studied: 5 patients were treated with OP, 8 patients with CV and 8 patients with AD. Mean LOS was 65 (OP) vs. 53 (CV) vs. 42 (AD) days (NS), peritonitis related death was 3 (OP) vs. 1 (CV) vs. 0 (AD) (p < 0.05 Chisquare test). Median nursing effort was 4 dressings/day (OP), 0.5 (CV) and 0.5 (AD) (p < 0.005 OP vs CV, AD Kruskal-Wallis test). CONCLUSION The "abdominal dressing"-therapy seems to be a more efficient treatment option in patients suffering from open abdomen following secondary peritonitis. A trend towards shorter ICU-LOS, lower mortality rates and reduced nursing requirements support our hypothesis.

Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid-fog phase transition. The charge distributions of the intermediate mass fragments produced in p(3.6 GeV) + Au and p(8.1 GeV) + Au collisions are analyzed within the statistical multifragmentation model with the critical temperature for the nuclear liquid-gas phase transition Tc as a free parameter. The analysis presented here provides strong support for a value of Tc > 15 MeV., 4 pages, 2 figures, Submittet to Proc. of NN2003 to be published in Nucl. Phys. A

PHOBOS is one of the four experiments at the Relativistic Heavy Ion Collider measuring p + p, d + Au , and Au + Au collisions over a broad range of energies. PHOBOS is a silicon-pad based detector with a 4π multiplicity detector and a high resolution mid-rapidity spectrometer, along with other detectors (time-of-flight walls, proton and zero degree calorimeters). PHOBOS is able to measure particles at low transverse momentum, spectra, flow, particle ratios, and multiplicity over a large region of phase space. A comparison of results for Au + Au and d + Au collisions at √S NN = 220GeV will be discussed.

The Proton-Induced SpAllation (PISA) experiment performed at the internal beam facility of the COSY storage ring in Julich, Germany, which is aimed at the precise measurement of double differential cross-sections over a broad range of energies and angles for spallation reactions induced by protons of 200– 2500 MeV energy in various targets, is presented. In this paper the emphasis is put on the design, principles of operation and performance of a Bragg Curve Detector (BCD) optimized for internal beam experiments at storage rings. Very clean and distinct product identification (with Z up to ∼14) from reactions, in which a Ni target was bombarded with a 1.9 GeV circulating proton beam, is obtained. The individual elements are resolved for emission energies higher than 0.5 MeV / nucleon . Moreover, due to the detector read-out achieved by coupling a specially designed current sensitive preamplifier directly to a sampling ADC, the shape analysis of the signals from the BCD allows the isotope identification of light particles with A up to ∼11. It is also found that the BCD can be used efficiently as a thin Δ E detector for the telescope consisting of the BCD and a series of silicon detectors.

Thermoluminescent MCP-N detectors based on LiF:Mg,Cu,P are by about 2 orders of magnitude more sensitive than TLD-100 detectors based on conventional LiF:Mg,Ti, which makes it possible to use them in short-term monitoring of ionizing radiation in the environment (e. g., over a two-week period, rather than over 3-12 months). We describe the properties of MCP-N detectors and methods of their application in environmental monitoring. The system was tested in short and long-term exposure periods at 100 sites around Krakow region. MCP-N detectors were then applied to measure variation of radiation dose rate at four selected villages in Serbia, where depleted uranium ammunition was deployed in 1999. Together with short-term thermoluminescent dosimetry, in situ measurements using proportional counters were per formed in order to assess the range of variation of natural radiation background in these villages. The mean terrestrial kerma dose rate in these villages was found to vary between 85 and 116 nGyh?1 and the average ambient dose equivalent rate H*(10) determined by thermoluminescent detectors and by proportional counter measurements was 160 nSvh?1. These values of natural radiation back ground dose rates can be applied as reference levels for field measurements around other sites where depleted uranium ammunition was deployed.

Introduction Reassessment of doses in film and OSL dosimetry is well known and standard method in contrary to TL dosimetry. By using the phototransferred thermoluminescence (PTTL) method which consist of the first readout, UV exposure and second readout it is possible to reassess doses in TL dosimetry. Purpose The PTTL method was developed and applied to reassess doses in whole body and ring dosimetry at Laboratory of Individual and Environmental Laboratory at IFJ PAN. Materials and methods Standard MTS-N (LiF: Mg, Ti) sintered thermoluminescent detectors (4.5 mm diameter and 0.9 mm thickness for whole body dosimeters and 0.7 mm thickness for ring dosimeters) have been applied. Some of them were used in routine control since 12 years. The TL detectors were read in automatic RE200 (Rados Oy, Finland) readers. After readout the PTTL method was applied. Detectors were subjected to UV radiation (254 nm length) and read once again in a reader. Results The PTTL method was applied to dose reassessment in individual and ring dosimetry. The reassessed doses are observed to be linear over the dose range 5–100 mSv in whole body dosimetry and 5–1000 mSv in ring dosimetry. Conclusion Due to checking behavior of different batches and different dose history it is possible to observe influence of residual dose to the PTTL effect. By using the PTTL method it is possible to reassess doses in whole body and ring dosimetry.

Some of the latest results of the PHOBOS experiment from the √s NN = 200 GeV Au+Au data are discussed. Those relevant to strangeness production are emphasized. These observations relate to the nature of the matter created when heavy ions collide at the highest achieved energy. The invariant yields of strange and non-strange charged hadrons at very low transverse momentum have been measured, and used to differentiate between different dynamical scenarios. In the intermediate transverse momentum range, the measured ratios of strange and anti-strange kaons approach one, while the antibaryon to baryon ratio is still significantly less, independent of collision centrality and transverse momentum. At high transverse momenta, we find that central and peripheral Au+Au collisions produce similar numbers of charged hadrons per participant nucleon pair, rather than per binary nucleon-nucleon collision.

Particle production in Au+Au collisions has been measured in the PHOBOS experiment at RHIC for a range of collision energies for a large span of pseudorapidities, |η| 65. This scaling occurs both for the total multiplicity and for highp T particles (3

The production of eta and eta-prime mesons in elementary nucleon-nucleon collisions has been investigated at the synchrotrons CELSIUS, COSY and SATURNE. The magnitude and energy dependence of the total cross section as well as the occupation distribution of the phase space serve as observables for investigating the mechanisms underlying the production processes and the interaction of mesons with nucleons. The precise data on the eta and eta-prime creation via the pp --> pp eta(eta-prime) reactions allowed to settle the general features of the eta and eta-prime meson production and revealed the sensitivity of the mentioned observables to the nucleon-nucleon-meson final state interaction. The particular production properties, like for example the determination of the dominating exchange processes which lead to the excitation of the S_11 nucleon isobar in the case of eta creation, must be established by confrontation with other observables. The present status of this investigation with an emphasis on the results of the COSY-11 collaboration is briefly presented. The available data are interpreted in view of the production mechanism and the meson-nucleon interaction., 3 pages, 3 figures, Presented at Conference on Quarks and Nuclear Physics (QNP 2002), Julich, Germany, 9-14 Jun 2002

The problem of magnetic field reconstruction inside a sub-region in R3 from magnetic measurements on the closed boundary of this sub-region is considered. Efficiency of the proposed method, the algorithm and associated software for precision magnet systems are discussed. The results of the software verification and numerical experiments are presented. A comparison between the reconstructed field and the measured field in the M1 magnet of the separator COMBAS is given. Requirements to the position accuracy of sensors consistent with the required accuracy of magnetic field reconstruction are defined. Recommendations on magnetic scheme design for field mapping are given. These investigations have been performed at the Flerov Laboratory of Nuclear Reactions, JINR.

Angular distributions of the 9 Be( 11 B, 10 B) 10 Be reaction were measured at E lab ( 11 B)=45 MeV for the transitions to the ground and excited states of the 10 B and 10 Be nuclei. The data were analyzed within the coupled-reaction-channels (CRC) method. One- and two-step transfers were studied. The optical potential parameters for the 10 Be+ 10 B interaction were deduced. We also analyze the 9 Be+ 10 B elastic scattering data at energies E cm =8.42–47.37 MeV known from the literature in order to study isotopic effect for the 9 Be+ 10 B, 9 Be+ 11 B and 10 Be+ 10 B channels. The energy dependence of the 9 Be+ 10 B and 10 Be+ 10 B OM potential parameters was deduced.

Angular distributions of the 13C+11B elastic and inelastic scattering were measured for the first time at E lab ( 11 B )=45 MeV in the full angular range for the transitions to the ground and excited states of the 11B and 13C nuclei. The data were analyzed within the optical model (OM) and coupled-reaction-channels (CRC) method. The mechanism of the 13C+11B anomalous large angle scattering (ALAS) was studied. The isotopic effects in the elastic and inelastic scattering of 13C+11B and 12C+11B are discussed. The OM potential parameters for the 13C+11B elastic scattering and deformation parameters of 11B and 13C were deduced.

Multiple emission of intermediate-mass fragments (IMF) in the collisions of protons (up to 8.1 GeV), 4He (4 and 14.6 GeV), and 12C (22.4 GeV) on Au has been studied with the 4π setup FASA. In all the cases, thermal multifragmentation of the hot and diluted target spectator takes place. The fragment multiplicity and charge distributions are well described by the combined model including the modified intranuclear cascade followed by the statistical multibody decay of the hot system. IMF-IMF-correlation study supports this picture, giving a very short time scale of the process (≤70 fm/c). This decay process can be interpreted as the first-order nuclear “liquid-fog” phase transition inside the spinodal region. The evolution of the mechanism of thermal multifragmentation with increasing projectile mass was investigated. The onset of the radial collective flow was observed for heavier projectiles. The analysis reveals information on the fragment space distribution inside the breakup volume: heavier IMFs are formed predominantly in the interior of the fragmenting nucleus possibly due to the density gradient.

Exclusive data on the reactions pp -> ppK+K- and pp -> pK+ Lambda/Sigma0 have been taken at the cooler synchrotron COSY close to threshold. At equal excess energies, an enhancement of the Lambda/Sigma0 ratio by one order of magnitude has been observed compared to data at higher excess energies. New results obtained at the COSY-11 facility explore the transition region between this low-energy Sigma0 suppression and excess energies of 60 MeV. A first total cross section for elementary antikaon production below the phi threshold has been determined, two orders of magnitude smaller compared to kaon production at the same excess energy., 4 pages, 2 figures, Talk given by P. Moskal at 16th International Conference on Particles and Nuclei (PANIC 02), Osaka, Japan, 30 Sep - 4 Oct 2002

The high-resolution wide aperture separator COMBAS was installed and commissioned in the Flerov Laboratory of Nuclear Reactions, JINR (Dubna) [Nucl. Instr. and Meth. A 306 (1991) 123; 426 (1999) 605; 479 (2002) 467]. It is designed for in-flight radioactive beam production of short-lived isotopes and experiments with them. The separator operates in the (20–50)A MeV ion energy region. It consists of the two stages, dispersive and achromatising. The second half of the separator is a mirror symmetrical counterpart of the first one, the intermediate focal plane being the plane of the symmetry. Multipole magnets with special profiled poles are used to correct higher order aberrations at the intermediate and final foci. The 3D magnetic measurements of the analysing magnets of the separator were done. The KOMPOT program for the 3D magnetic field calculations [Doinikov et al., 1986, Preprint/CNNI atominform: B-0741, 13p; Belyaev et al., Int. Conf. “Optimisation of Finite Element Approximations”, St.Pt., Russia, 25–29 June 1995, p.101; IEEE Transact. On Magnetics, 28 (1) (1992) 908; Frenkel, Selected works, USSR Academy of Sciences publ., Moscow–Leningrad, v.1 (Electrodynamics), 1956; Proc. IEEE, 114 (7) (1967) 995; Livingston, Blewett, Particle accelerators, No. 7, McGraw-Hill, 1962, p. 253] was used for the analysis of these magnetic measurements data, as well as for the reconstruction of the magnet fields inside the total volume closed by the 3D surface, where the magnetic measurements had been performed. As a result of the magnetic field reconstruction we obtained field maps, which would be used in simulations of particle trajectories.

The yields of identified particles have been measured at RHIC for Au+Au collisions at sqrt{s_NN} = 200 GeV using the PHOBOS spectrometer. The ratios of antiparticle to particle yields near mid-rapidity are presented. The first measurements of the invariant yields of charged pions, kaons and protons at very low transverse momenta are also shown.

We present transverse momentum distributions of charged hadrons produced in Au+Au collisions at sqrt(s_NN) = 200 GeV. The evolution of the spectra for transverse momenta p_T from 0.25 to 5GeV/c is studied as a function of collision centrality over a range from 65 to 344 participating nucleons. We find a significant change of the spectral shape between proton-antiproton and peripheral Au+Au collisions. Comparing peripheral to central Au+Au collisions, we find that the yields at the highest p_T exhibit approximate scaling with the number of participating nucleons, rather than scaling with the number of binary collisions.

This manuscript contains a detailed description of the PHOBOS experiment as it is configured for the Year 2001 running period. It is capable of detecting charged particles over the full solid angle using a multiplicity detector and measuring identified charged particles near mid-rapidity in two spectrometer arms with opposite magnetic fields. Both of these components utilize silicon pad detectors for charged particle detection. The minimization of material between the collision vertex and the first layers of silicon detectors allows for the detection of charged particles with very low transverse momenta, which is a unique feature of the PHOBOS experiment. Additional detectors include a time-of-flight wall which extends the particle identification range for one spectrometer arm, as well as sets of scintillator paddle and Cherenkov detector arrays for event triggering and centrality selection.

Angular distributions of the 9Be+11B elastic and inelastic scattering were measured at Elab(11B)=45 MeV in a large angular range for the transitions to the ground and excited states of the 11B and 9Be nuclei. The data were analyzed within the coupled-reaction-channels (CRC) method. We have also included the data of the 11B+9Be elastic scattering at Ecm≈9–22 MeV known from the literature. The mechanisms of the 9Be+11B anomalous large angle scattering (ALAS) were studied both for the elastic and inelastic channels including the 9Be and 11B reorientations and transfer reactions. The optical potential parameters for the 9Be+11B elastic scattering and the 11B and 9Be deformation parameters were deduced.