Meson Mixing and Dilepton Production in Heavy Ion Collisions

We study the possibility of $\rho-a_0$ mixing via N-N excitations in dense nuclear matter. This mixing is found to induce a peak in the dilepton spectra at an invariant mass equal to that of the $a_0$. We calculate the cross section for dilepton production through mixing and we compare its size with that of $\pi-\pi$ annihilation. In-medium masses and mixing angles are also calculated. Some preliminary results of the mixing effect on the dilepton production rates at finite temperature are also presented.Comment: To be published in the proceedings of CIPANP 200

A unique parametrization of the shapes of secondary dilepton spectra observed in central heavy-ion collisions at CERN-SPS energies

A unique parametrization of secondary (thermal) dilepton yields in heavy-ion experiments at CERN-SPS is proposed. This parametrization resembles a thermal $q \bar q$ annihilation rate. This is inspired by the observation that lepton pair production rates are quantitatively similar, whether expressed in a hadronic or partonic basis. Adding the thermal yield and the background contributions (hadronic cocktail, Drell-Yan, correlated semileptonic decays of open charm) the spectral shapes of the CERES/NA45, NA38, NA50 and HELIOS/3 data from experiments with lead and sulfur beams can be well described.Comment: 23 pages including figures (new version: only new output format

An evaluation of staff engagement programmes in four National Health Service Acute Trusts

Purpose – The purpose of this paper is to report the findings from an evaluation project conducted to investigate the impact of two staff engagement programmes introduced to four National Health Service (NHS) hospital Trusts in England. It seeks to examine this development in the context of current policy initiatives aimed at increasing the level of staff involvement in decision-making, and the related literature. \ud \ud Design/methodology/approach – A mixed-methods approach incorporating document analysis, interviews, a survey and appreciative inquiry, informed by the principles of impact evaluation design, was used. \ud \ud Findings – The main finding to emerge was that leadership was crucial if widespread staff engagement was to be achieved. Indeed, in some of the trusts the staff engagement programmes were seen as mechanisms for developing leadership capability. The programmes had greater impact when they were “championed” by the Chief Executive. Effective communication throughout the organisations was reported to be a prerequisite for staff engagement. Problems were identified at the level of middle management where the lack of confidence in engaging with staff was a barrier to implementation. \ud \ud Practical implications – The nature of the particular organisational context is crucial to the success of efforts to increase levels of staff engagement. The measures that were found to work in the trusts would need to be adapted and applied to best meet the needs of other organisations. \ud \ud Originality/value – Many health care organisations in England will need to harness the efforts of their workforce if they are to meet the significant challenges of dealing with financial restraint and increasing patient demand. This paper provides some insights on how this can be done

Elliptic flow of thermal dileptons in relativistic nuclear collisions

We calculate the transverse momentum and invariant mass dependence of elliptic flow of thermal dileptons for Au+Au collisions at the Relativistic Heavy Ion Collider. The system is described using hydrodynamics, with the assumption of formation of a thermalized quark-gluon plasma at some early time, followed by cooling through expansion, hadronization and decoupling. Dileptons are emitted throughout the expansion history: by annihilation of quarks and anti-quarks inthe early quark-gluon plasma stage and through a set of hadronic reactions during the late hadronic stage. The resulting differential elliptic flow exhibits a rich structure, with different dilepton mass windows providing access to different stages of the expansion history. Elliptic flow measurements for dileptons,combined with those of hadrons and direct photons, are a powerful tool for mapping the time-evolution of heavy-ion collisions.Comment: Latex 8 pages including a total of 13 postscript figures. Added 2 figures, additional references, and expanded discussions. Figures modified for better viewing. To appear in Phys. Rev.