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STAR's measurements of directed flow (v1) around midrapidity for π±, K±, K0S, p and p¯ in Au + Au collisions at $\sqrtsNN = 200$ GeV are presented. A negative v1(y) slope is observed for most of produced particles (π±, K±, K0S and p¯). In 5-30% central collisions a sizable difference is present between the v1(y) slope of protons and antiprotons, with the former being consistent with zero within errors. The v1 excitation function is presented. Comparisons to model calculations (RQMD, UrQMD, AMPT, QGSM with parton recombination, and a hydrodynamics model with a tilted source) are made. For those models which have calculations of v1 for both pions and protons, none of them can describe v1(y) for pions and protons simultaneously. The hydrodynamics model with a tilted source as currently implemented cannot explain the centrality dependence of the difference between the v1(y) slopes of protons and antiprotons.
STAR's measurements of directed flow (v1) around midrapidity for π±, K±, K0S, p and p¯ in Au + Au collisions at $\sqrtsNN = 200$ GeV are presented. A negative v1(y) slope is observed for most of produced particles (π±, K±, K0S and p¯). The proton v1(y) slope is found to be much closer to zero compared to antiprotons. A sizable difference is seen between v1 of protons and antiprotons in 5-30% central collisions. The v1 excitation function is presented. Comparisons to model calculations (RQMD, UrQMD, AMPT, QGSM with parton recombination, and a hydrodynamics model with a tilted source) are made. Anti-flow alone cannot explain the centrality dependence of the difference between the v1(y) slopes of protons and antiprotons.
The paper is a follow-up to an article published in Technique Financière et Developpement in 2000 (see the appendix to the hardcopy version), which portrayed the first results of a new strategy in the field of development finance implemented in South-East Europe. This strategy consists in creating microfinance banks as greenfield investments, that is, of building up new banks which specialise in providing credit and other financial services to micro and small enterprises, instead of transforming existing credit-granting NGOs into formal banks, which had been the dominant approach in the 1990s. The present paper shows that this strategy has, in the course of the last five years, led to the emergence of a network of microfinance banks operating in several parts of the world. After discussing why financial sector development is a crucial determinant of general social and economic development and contrasting the new strategy to former approaches in the area of development finance, the paper provides information about the shareholder composition and the investment portfolio of what is at present the world's largest and most successful network of microfinance banks. This network is a good example of a well-functioning "private public partnership". The paper then provides performance figures and discusses why the creation of such a network seems to be a particularly promising approach to the creation of financially self-sustaining financial institutions with a clear developmental objective.
New results from the energy scan programme of NA49, in particular kaon production at 30 AGeV and phi production at 40 and 80 AGeV are presented. The K+/pi+ ratio shows a pronounced maximum at 30 AGeV; the kaon slope parameters are constant at SPS energies. Both findings support the scenario of a phase transition at about 30 AGeV beam energy. The phi/pi ratio increases smoothly with beam energy, showing an energy dependence similar to K-/pi-. The measured particle yields can be reproduced by a hadron gas model, with chemical freeze-out parameters on a smooth curve in the T-muB plane. The transverse spectra can be understood as resulting from a rapidly expanding, locally equilibrated source. No evidence for an earlier kinetic decoupling of heavy hyperons is found.
Results are presented from a search for the decays D0 -> K min pi plus and D0 bar -> K plus pi min in a sample of 3.8x10^6 central Pb-Pb events collected with a beam energy of 158A GeV by NA49 at the CERN SPS. No signal is observed. An upper limit on D0 production is derived and compared to predictions from several models.
The paper is a follow-up to an article published in Technique Financière et Developpement in 2000 (see the appendix to the hardcopy version), which portrayed the first results of a new strategy in the field of development finance implemented in South-East Europe. This strategy consists in creating microfinance banks as greenfield investments, that is, of building up new banks which specialise in providing credit and other financial services to micro and small enterprises, instead of transforming existing credit-granting NGOs into formal banks, which had been the dominant approach in the 1990s. The present paper shows that this strategy has, in the course of the last five years, led to the emergence of a network of microfinance banks operating in several parts of the world. After discussing why financial sector development is a crucial determinant of general social and economic development and contrasting the new strategy to former approaches in the area of development finance, the paper provides information about the shareholder composition and the investment portfolio of what is at present the world's largest and most successful network of microfinance banks. This network is a good example of a well-functioning "private public partnership". The paper then provides performance figures and discusses why the creation of such a network seems to be a particularly promising approach to the creation of financially self-sustaining financial institutions with a clear developmental objective.
Directed and elliptic flow of charged pions and protons in Pb + Pb collisions at 40 and 158 A GeV
(2003)
Directed and elliptic flow measurements for charged pions and protons are reported as a function of transverse momentum, rapidity, and centrality for 40 and 158A GeV Pb + Pb collisions as recorded by the NA49 detector. Both the standard method of correlating particles with an event plane, and the cumulant method of studying multiparticle correlations are used. In the standard method the directed flow is corrected for conservation of momentum. In the cumulant method elliptic flow is reconstructed from genuine 4, 6, and 8-particle correlations, showing the first unequivocal evidence for collective motion in A+A collisions at SPS energies.
The energy dependence of rapidity distributions and flow effects was studied in central Ar+Pb collisions at 400, 800, and 1800 MeV/nucleon using a streamer chamber. Rapidity distributions for proton and pions are found to have a Gaussian shape whereas those for deuterons exhibit a two-peak structure at the two higher energies. The average in-plane transverse momentum per/nucleon and per/event shows saturation of flow around 800 MeV/nucleon for this asymmetric system. The aspect ratio of the sphericity tensor is closely correlated with the flow angle. This correlation appears to be independent of beam energy. The number of participating nucleons in central collisions varies from 213 at 400 to 135 at 1800 MeV/nucleon indicating that at the lowest energy almost the entire target nucleus participates in the collision.
An event by event analysis is carried out for all charged particles observed in central collisions of 40Ar + KCl and 40Ar + Pb at 1.808 and 0.772 GeV/nucleon, respectively. Total transverse energy is used for impact parameter selection within the central trigger condition. The central Ar + KCl reaction exhibits a forward-backward oriented momentum flux. The flux distribution of the most central Ar + Pb events is approximately isotropic in the fireball center of mass.
The negative-pion multiplicity is measured for central collisions of 40Ar with KCl at eight energies from 0.36 to 1.8 GeV/nucleon and for 4He on KCl and 40Ar on BaI2 at 977 and 772 MeV/nucleon, respectively. A systematic discrepancy with a cascade-model calculation which fits proton- and pion-nucleus cross sections but omits potential-energy effects is used to derive the energy going into bulk compression of the system. A value of the incompressibility constant of K=240 MeV is extracted in a parabolic form of the nuclear-matter equation of state.