Volume 66, Issue 4
April 2006, pages 621-960
pp 621-621 April 2006
pp 623-624 April 2006
Shashi C Phatak Pradip K Sahu Radhey Shyam
pp 625-645 April 2006
Structure and reactions of pentaquark baryons
We review the current status of the exotic pentaquark baryons. After a brief look at experiments of both positive and negative results, we discuss theoretical methods to study the structure and reactions for the pentaquarks. First we introduce the quark model and the chiral soliton model, where we discuss the relation of mass spectrum and parity with some emphasis on the role of chiral symmetry. It is always useful to picture the structure of the pentaquarks in terms of quarks. As for other methods, we discuss a model-independent method, and briefly mention the results from the lattice and QCD sum rule. Decay properties are then studied in some detail, which is one of the important properties of ⊝^{+}. We investigate the relation between the decay width and the quark structure having certain spin-parity quantum numbers. Through these analyses, we consider as plausible quantum numbers of ⊝^{+},J^{P} = 3/2^{−}. In the last part of this note, we discuss production reactions of ⊝^{+} which provide links between the theoretical models and experimental information. We discuss photoproductions and hadron-induced reactions which are useful to explore the nature of ⊝^{+}
pp 647-655 April 2006
Pentaquarks in chiral color dielectric model
Recent experiments indicate that a narrow baryonic state having strangeness +1 and mass of about 1540 MeV may be existing. Such a state was predicted in chiral model by Diakonovet al. In this work I compute the mass and width of this state in chiral color dielectric model. I show that the computed width is about 30 MeV. I find that the mass of the state can be fitted to the experimentally observed mass by invoking a color neutral vector field and its interaction with the quarks
pp 657-668 April 2006
Theoretical expectations for σ^{tot} at the large hadron collider
Rohini M Godbole Agnes Grau Rohit Hegde Giulia Pancheri Yogi Srivastava
In this note, we summarize and compare various model predictions forpp total cross-section σ_{tot}^{pp}, giving an estimate of the range of predictions for the total cross-section, σ_{tot}^{pp} expected at the LHC. We concentrate on the results for σ_{tot}^{pp} obtained in a particular QCD based model of the energy dependence of the total cross-section, including the effect of soft gluon radiation. We obtain the range of predictions in this model by exploring the allowed range of model parameters. We further give a handy parametrisation of these results which incidentally spans the range of various other available predictions at the LHC as well
pp 669-687 April 2006
Some applications of thermal field theory to quark-gluon plasma
We briefly introduce the thermal field theory within imaginary time formalism, the hard thermal loop perturbation theory and some of its applications to the physics of the quark-gluon plasma, possibly created in relativistic heavy-ion collisions
pp 689-701 April 2006
Weak pion production from nuclei
S K Singh M Sajjad Athar Shakeb Ahmad
The charged current pion production induced by neutrinos in^{12}C,^{16}O and^{56}Fe nuclei has been studied. The calculations have been done for the coherent as well as the incoherent processes assuming Δ dominance and takes into account the effect of Pauli blocking, Fermi motion and the renormalization of Δ in the nuclear medium. The pion absorption effects have also been taken into account
pp 703-708 April 2006
Proton electromagnetic form factors at large momentum transfer
We review the current experimental and theoretical status of the proton electromagnetic form factors.
pp 709-729 April 2006
In these lectures I first give the motivation for investigations of in-medium properties of hadrons. I discuss the relevant symmetries of QCD and how they might affect the observed hadron properties. I then discuss at length the observable consequences of in-medium changes of hadronic properties in reactions with elementary probes, and in particular photons, on nuclei. Here I put an emphasis on new experiments on changes of the σ- and ω-mesons in medium
pp 731-752 April 2006
Chiral dynamics of baryon resonances and hadrons in a nuclear medium
E Oset D Cabrera V K Magas L Roca S Sarkar M J Vicente Vacas A Ramos
In these lectures I make an introduction to chiral unitary theory applied to the meson-baryon interaction and show how several well-known resonances are dynamically generated, and others are predicted. Two very recent experiments are analyzed, one of them showing the existence of two Λ(1405) states and the other one providing support for the Λ(1520) resonance as a quasi-bound state of Σ(1385)π. The use of chiral Lagrangians to account for the hadronic interaction at the elementary level introduces a new approach to deal with the modification of meson and baryon properties in a nuclear medium. Examples of it for $$\bar K$$ andø modification in the nuclear medium are presented
pp 753-764 April 2006
Hadron production near threshold
B K Jain N G Kelkar K P Khemchandani
Final state interaction effects inpp→ pΛK^{+} andpd →^{3}Heη reactions are explored near threshold to study the sensitivity of the cross-sections to thepΛ potential and theηN scattering matrix. The final state scattering wave functions between Λ andp andη and^{3}He are described rigorously. The Λ production is described by the exchange of one pion and aK-meson between two protons in the incident channel. Theη production is described by a two-step model, where in the first step a pion is produced. This pion then produces anη by interacting with another nucleon
pp 765-780 April 2006
Strangeness production in proton—proton and proton—nucleus collisions
We discuss the investigation of the strange meson production in proton-proton (pp) and proton-nucleus (pA) reactions within an effective Lagrangian model. The kaon production proceeds mainly via excitations ofN*(1650),N*(1710), andN* (1720) resonant intermediate nucleonic states, in the collision of two initial state nucleons. Therefore, the strangeness production is expected to provide information about the resonances lying at higher excitation energies. For beam energies very close to the kaon production threshold the hyperon-proton final state interaction effects are quite important. Thus, these studies provide a check on the models of hyperon-nucleon interactions. The inmedium production of kaons shows strong sensitivity to the self-energies of the intermediate mesons
pp 781-790 April 2006
One consequence of the chiral restoration is the mixing of parity partners. We look for a possible signature of the mixing of vector and axial vector mesons in heavyion collisions. We suggest an experimental method for its observation. The dynamical evolution of the heavy-ion collision is described by a transport equation of QMD-type evolving nucleons,N* and Δ resonances, Λ’s and gS baryons, and furthermore,π’s,η’sρ’sσ’sΩ’s and kaons with their isospin degrees of freedom. The input cross-sections and resonance parameters of the model are fitted to the available nucleon-nucleon and pion-nucleon cross-sections
pp 791-796 April 2006
Resonances inη-light nucleus systems
K P Khemchandani N G Kelkar M Nowakowski B K Jain
We locate resonances inη-light nucleus elastic scattering using the time delay method. We solve few-body equations within the finite rank approximation in order to calculate the t-matrices and hence the time delay for theη-^{3}He andη-^{4}He systems. We find a resonance very close to the threshold inη-^{3}He elastic scattering, at about 0.5 MeV above threshold with a width of ∼2 MeV. The calculations also hint at the presence of sub-threshold states in both the cases
pp 797-807 April 2006
Collective flows in high-energy heavy-ion collisions at AGS and SPS energies
A Ohnishi M Isse N Otuka P K Sahu Y Nara
Proton collective flows in heavy-ion collisions from AGS ((2–11) A GeV) to SPS ((40,158) A GeV) energies are investigated in a nonequilibrium transport model with nuclear mean-field (MF). Sideward (p_{x}), directedv_{1}, and ellipticv_{2} flows are systematically studied with different assumptions on the nuclear equation of state (EoS). We find that momentum dependence in the nuclear MF is important for understanding the proton collective flows at AGS and SPS energies. Calculated results with momentum-dependent MF qualitatively reproduce the experimental data of proton sideward, directed, and elliptic flows in an incident energy range of (2–158) A GeV
pp 959-960 April 2006
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