• Volume 66, Issue 5

      May 2006,   pages  621-960

    • Foreword

      R K Choudhury

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    • Preface

      Shashi C Phatak Pradip K Sahu Radhey Shyam

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    • Re-hardening of hadron transverse mass spectra in relativistic heavy-ion collisions

      P K Sahu N Otuka M Isse Y Nara A Ohnishi

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      We analyze the spectra of pions and protons in heavy-ion collisions at relativistic energies from 2 A GeV to 65+65 A GeV by using a jet-implemented hadron-string cascade model. In this energy region, hadron transverse mass spectra first show softening until SPS energies, and re-hardening may emerge at RHIC energies. Since hadronic matter is expected to show only softening at higher energy densities, this re-hardening of spectra can be interpreted as a good signature of the quark-gluon plasma formation

    • Hadrons in compact stars

      Debades Bandyopadhyay

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      We discuss β-equilibrated and charge neutral matter involving hyperons and {ie817-1} condensates within relativistic models. It is observed that populations of baryons are strongly affected by the presence of antikaon condensates. Also, the equation of state including {ie817-2} condensates becomes softer resulting in a smaller maximum mass neutron star

    • A new ‘hidden colour hypothesis’ in hadron physics

      Afsar Abbas

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      A new ‘hidden colour hypothesis’ within the framework of QCD, as an extension of and in keeping with the spirit of the ‘colour singlet hypothesis’ is hereby proposed. As such it should play a role in a consistent description of exotic hadrons, such as diquonia, pentaquarks, dibaryons etc. How these exotic hadrons are affected by this new hypothesis is discussed here. This new hypothesis suggests that the experimentalists may not be looking for single exotics but for composites of two or more of the same

    • In-medium properties of hadrons — Recent experimental results and perspectives

      Volker Metag

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      Recent experimental results on the modification of hadron properties in a nuclear medium are discussed. Experiments using hadron, heavy-ion and photon beams are described. Particular emphasis is given to the photonuclear production of light vector mesons and scalar mesons off nuclei. Recent results on the search for meson-nucleus bound states are presented. Perspectives for extending these studies to the charm sector are outlined

    • QCD physics at hadron storage rings: From COSY to FAIR

      James Ritman

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      As a result of the rapid rise of the coupling constant αs at low momentum transfers, perturbation theory is not an appropriate method to describe the strong interaction. In this kinematic regime other methods such as lattice QCD or effective field theories are more appropriate to investigate the appearance of a still unsettled phenomena: confinement and chiral symmetry breaking. Furthermore, the confinement of quarks and gluons to hadrons allows crucial tests of fundamental symmetries that are inherent to the QCD Lagrangian but are broken in hadronic systems. Thus, high precision measurements of the production and decay of specific hadronic states provides decisive benchmarks to investigate the properties of QCD in this regime. A new series of experiments are being prepared using nearly full acceptance detectors for neutral and charged particles around internal targets in high intensity, phase-space-cooled hadronic beams. Later this year, it is planned to transfer the WASA detector from the CELSIUS to the COSY ring in order to measure the production and various decay channels of the η and η′ mesons, thereby investigating the violation of P, C, T, and combinations thereof, as well as isospin violation. The experimental and theoretical techniques employed here will provide an important basis to extend these investigations to the static and dynamical properties of hadrons with charm quark content with the high energy storage ring for antiprotons at the new GSI/FAIR facility. Additional related perspectives will be opened at the new facility ranging from the properties of hadrons in dense nuclear matter to measurements of the nucleon’s transverse spin distribution in the valence quark region using polarized antiprotons

    • Recent physics at COSY — a review

      H Machner

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      The COSY accelerator in Jülich is presented together with its internal and external detectors. The physics program performed recently is discussed with emphasis on strangeness physics and precision experiments

    • Two-pion production in photon-induced reactions

      S Schadmand

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      Differences in the photoproduction of mesons on the free proton and on nuclei are expected to reveal changes in the properties of hadrons. Inclusive studies of nuclear photoabsorption have provided evidence of medium modifications. However, the results have not been explained in a model independent way. A deeper understanding of the situation is anticipated from a detailed experimental study of meson photoproduction from nuclei in exclusive reactions. In the energy regime above the Δ(1232) resonance, the dominant double pion production channels are of particular interest. Double pion photoproduction from nuclei is also used to investigate the in-medium modification of meson-meson interactions

    • ENSTAR detector forη- mesic studies

      A Chatterjee B J Roy V Jha P Shukla H Machner

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      We have initiated a search for a new type of nuclear matter, theη-mesic nucleus, using beams from the multi-GeV hadron facility, COSY at Juelich, Germany. A large acceptance scintillator detector, ENSTAR has been designed and built at BARC, Mumbai and fully assembled and tested at COSY. A test run for calibration and evaluation has been completed. In this contribution we present the design and technical details of the ENSTAR detector and how it will be used to detect protons and pions (the decay products ofη-mesic bound state). The detector is made of plastic scintillators arranged in three concentric cylindrical layers. The readout of the detectors is by means of optical fibres. The layers are used to generate ΔEE spectra for particle identification and total energy information of stopped particles. The granularity of the detector allows for position (θ and ϕø determination making the event reconstruction kinematically complete

    • Isospin symmetry violation, meson production and η-nucleus interaction studies

      B J Roy V Jha A Chatterjee H Machner

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      We have studied isospin symmetry violation in nuclear reactions by measuring simultaneously the cross-section of the following two reactionsp +d3H π+ andp +d3He π0. The experiment was perfomed at the cooler synchrotron accelerator COSY, Jülich at several beam energies close to the correspondingη production threshold. We also have ongoing programmes onη-nucleus final-state interaction studies viap+6 Li →7 Be +η reactions, high resolution search for dibaryonic resonances and lambda-proton final state interaction studies. The experimental details and results obtained so far are presented here

    • Tagged photon facility at Centre for Advanced Technology, Indore: Possible scenarios

      L M Pant

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      Photoproduction of ω in nuclear medium with the ELSA facility at Bonn is discussed in the context of medium modification of hadronic properties. Utilization of Indus-2 at CAT, Indore for producing tagged bremsstrahlung photons and laser backscattered photons has been explored with a comparison between the two techniques for producing tagged high energy photons for the first time in the country with emphasis on the ADSS programme to have a precise information of (γ,n) reactions

    • Investigation of in-medium ω photoproduction

      David Trnka

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      Recent experimental results on the in-medium modification of the ω meson are discussed. The experiment described was performed at the ELSA accelerator facility in Bonn using the combined detector system of Crystal Barrel and TAPS. Theω-meson was identified via the reaction γ+A → ω +X → π0 γ +X

    • Investigations ofη → π0γγ

      Ankhi Roy

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      In this paper we report the efforts carried out to measure the branching ratio of η π0γγ. The experiment was done using the tagged photon facility at ELSA, Bonn. A nearly full 4π set-up comprising of the Crystal Barrel and TAPS detector system was used. We describe the procedure followed to extract the branching ratio of this rare decay mode of eta. The simulations necessary to establish this procedure are presented first followed by data analysis

    • Nucleon resonance decay by theK0Σ+ channel: Preliminary results

      S V Shende R Castelijns J C S Bacelar H Löhner J Messchendorp

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      The strange meson production on a proton target in theK0Σ+ channel is sensitive to nucleon resonance contributions. TheK0 production on a deuteron target can provide information on the hyperon-nucleon final-state interaction. The experiments γpK0Σ+ andγd →K0Σ+n have been carried out at the ELSA facility at Bonn. In this paper, we report the preliminary results of both experiments

    • Search for non-strange dibaryons

      Arun K Jain

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      Inspite of tremendous interest there has been sporadic searches for dibaryon resonances in the past few decades. The main hurdle one faces in this search is their identification, their signature and practically no guide to their location. With the identification of the pentaquark-θ+ resonance one is encouraged to look for the discovery of strange dibaryons also. However where and how to look for non-strange dibaryons is not clear. The transition from a bipolar to a unipolar non-strange dibaryon may possibly be seen in the (p, 2p) reactions on heavy nuclei. The change of the finite size of thep-p interaction vertex can be identified as a sudden change in the extracted DWIA spectroscopic factor. The DWIA anomalies are to be searched for in the existing (p, 2p) reaction data for the identification of non-strange dibaryons

    • Study ofη-nucleus interaction through the formation ofη-nucleus bound state

      V Jha B J Roy A Chatterjee H Machner

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      The question of possible existence ofη-mesic nuclei is quite intriguing. Answer to this question will deeply enrich our understanding ofη-nucleus interaction which is not so well-understood. We review the experimental efforts for the search ofη-mesic nuclei and describe the physics motivation behind it. We present the description of an experiment for the search ofη-nucleus bound state using the GeV proton beam, currently being performed at COSY

    • (γ, π0γ) reaction on a nucleus in the GeV region

      Swapan Das

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      π0γ invariant mass distribution spectrum has been calculated for the (γ, π0γ) reaction on12C nucleus at 2.5 GeV beam energy. These π0 and γ are assumed to originate due to the decay of vector mesons produced in the photonuclear reaction. The nuclear medium effect on vector mesons and the effect of π0 rescattering on the π0γ invariant mass spectrum have been investigated

    • Properties ofBc meson

      Ajay Kumar Rai P C Vinodkumar

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      The mass spectrum ofcb meson is investigated with an effective quark-antiquark potential of the form -αc/r +Arνwith ν varying from 0.5 to 2.0. TheS andP-wave masses, pseudoscalar decay constant, weak decay partial widths in spectator model and the lifetime ofBcmeson are computed. The properties calculated here are found to be in good agreement with other theoretical and experimental values at potential index,ν = 1

    • List of Participants

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