Central Pb+Pb Collisions at 158 A GeV/c Studied by Pion-Pion Interferometry

Two-particle correlations have been measured for identified negative pions from central 158 AGeV Pb+Pb collisions and fitted radii of about 7 fm in all dimensions have been obtained. A multi-dimensional study of the radii as a function of kT is presented, including a full correction for the resolution effects of the apparatus. The cross term Rout-long of the standard fit in the Longitudinally CoMoving System (LCMS) and the vl parameter of the generalised Yano-Koonin fit are compatible with 0, suggesting that the source undergoes a boost invariant expansion. The shapes of the correlation functions in Qinv and Qspace have been analyzed in detail. They are not Gaussian but better represented by exponentials. As a consequence, fitting Gaussians to these correlation functions may produce different radii depending on the acceptance of the experimental setup used for the measurement.Comment: 13 pages including 10 figure

Search for Heavy Neutral and Charged Leptons in e+ e- Annihilation at LEP

A search for exotic unstable neutral and charged heavy leptons as well as for stable charged heavy leptons is performed with the L3 detector at LEP. Sequential, vector and mirror natures of heavy leptons are considered. No evidence for their existence is found and lower limits on their masses are set

Suppression of High-p_T Neutral Pion Production in Central Pb+Pb Collisions at sqrt{s_NN} = 17.3 GeV Relative to p+C and p+Pb Collisions

Neutral pion transverse momentum spectra were measured in p+C and p+Pb collisions at sqrt{s_NN} = 17.4 GeV at mid-rapidity 2.3 < eta_lab < 3.0 over the range 0.7< p_T < 3.5 GeV/c. The spectra are compared to pi0 spectra measured in Pb+Pb collisions at sqrt{s_NN} = 17.3 GeV in the same experiment. For a wide range of Pb+Pb centralities (N_part < 300) the yield of pi0's with p_T > 2 GeV/c is larger than or consistent with the p+C or p+Pb yields scaled with the number of nucleon-nucleon collisions (N_coll), while for central Pb+Pb collisions with N_part > 350 the pi0 yield is suppressed.Comment: 5 pages, 4 figure

Impact and implications of international financial reporting standards in the UK : evidence from the alternative investment market

This paper investigates implications of the IFRS adoption from the perspective of small and growing companies listed on the UK Alternative Investment Market (AIM). The study considers the cost-benefit issues of the IFRS adoption and investigates its economic consequences. The results reveal that only a small number of comparatively larger AIM companies have voluntarily adopted IFRS for some anticipated economic objectives. The results also suggest that most of the mandatory adopters have done so for regulation compliance purposes and that they would have not adopted IFRS if a choice was available to them. As the existing literature mainly covers the impact of IFRS adoption on large listed companies, the findings of this study will give better insights about extending IFRS to private companies. The findings show an association between the early adoption of IFRS and firm size and conclude that size matters in both the adoption and implications of the IFRS. This study also contributes to the debate on the implication of the new IFRS based UK GAAP for SMEs-FRS 102, which will replace the majority of existing UK accounting standards for SMEs with effect from 2015. Our findings have implications for managers, regulators, market participants, practitioners, and other stakeholders

Search for Disoriented Chiral Condensates in 158 AGeV Pb+Pb Collisions

The restoration of chiral symmetry and its subsequent breaking through a phase transition has been predicted to create regions of Disoriented Chiral Condensates (DCC). This phenomenon has been predicted to cause anomalous fluctuations in the relative production of charged and neutral pions in high-energy hadronic and nuclear collisions. The WA98 experiment has been used to measure charged and photon multiplicities in the central region of 158 AGeV Pb+Pb collisions at the CERN SPS. In a sample of 212646 events, no clear DCC signal can be distinguished. Using a simple DCC model, we have set a 90% C.L. upper limit on the maximum DCC production allowed by the data.Comment: 20 Pages, LaTeX, uses elsart.cls, 8 eps figures included, submitted to Physics Letters

Observation of Direct Photons in Central 158 A GeV 208Pb+208Pb^{208}Pb+^{208}Pb Collisions

A measurement of direct photon production in 208Pb + 208Pb collisions at 158 A GeV has been carried out in the CERN WA98 experiment. The invariant yield of direct photons in central collisions is extracted as a function of transverse momentum in the interval 0.5 1.5 GeV/c. The results constitute the first observation of direct photons in ultrarelativistic heavy-ion collisions which could be significant for diagnosis of quark gluon plasma formation.A measurement of direct photon production in 208Pb + 208Pb collisions at 158 A GeV has been carried out in the CERN WA98 experiment. The invariant yield of direct photons in central collisions is extracted as a function of transverse momentum in the interval 0.5 1.5 GeV/c. The results constitute the first observation of direct photons in ultrarelativistic heavy-ion collisions which could be significant for diagnosis of quark gluon plasma formation

Directed Flow in 158 A GeV 208Pb^{208}Pb + 208Pb^{208}Pb Collisions

The directed flow of protons and positive pions have been studied in 158 A GeV Pb + Pb collisions. A directed flow analysis of the rapidity dependence of the average transverse momentum projected onto the reaction plane is presented for semi-central collisions with impact parameters of approximately 8 fm, where the flow effect is largest. The magnitude of the directed flow is found to be significantly smaller than observed at AGS energies and than RQMD model predictions.The directed flow of protons and positive pions have been studied in 158 A GeV Pb + Pb collisions. A directed flow analysis of the rapidity dependence of the average transverse momentum projected onto the reaction plane is presented for semi-central collisions with impact parameters of approximately 8 fm, where the flow effect is largest. The magnitude of the directed flow is found to be significantly smaller than observed at AGS energies and than RQMD model predictions

Facing the Challenge of Data Transfer from Animal Models to Humans: the Case of Persistent Organohalogens

A well-documented fact for a group of persistent, bioaccumulating organohalogens contaminants, namely polychlorinated biphenyls (PCBs), is that appropriate regulation was delayed, on average, up to 50 years. Some of the delay may be attributed to the fact that the science of toxicology was in its infancy when PCBs were introduced in 1920's. Nevertheless, even following the development of modern toxicology this story repeats itself 45 years later with polybrominated diphenyl ethers (PBDEs) another compound of concern for public health. The question is why? One possible explanation may be the low coherence between experimental studies of toxic effects in animal models and human studies. To explore this further, we reviewed a total of 807 PubMed abstracts and full texts reporting studies of toxic effects of PCB and PBDE in animal models. Our analysis documents that human epidemiological studies of PBDE stand to gain little from animal studies due to the following: 1) the significant delay between the commercialisation of a substance and studies with animal models; 2) experimental exposure levels in animals are several orders of magnitude higher than exposures in the general human population; 3) the limited set of evidence-based endocrine endpoints; 4) the traditional testing sequence (adult animals – neonates – foetuses) postpones investigation of the critical developmental stages; 5) limited number of animal species with human-like toxicokinetics, physiology of development and pregnancy; 6) lack of suitable experimental outcomes for the purpose of epidemiological studies. Our comparison of published PCB and PBDE studies underscore an important shortcoming: history has, unfortunately, repeated itself. Broadening the crosstalk between the various branches of toxicology should therefore accelerate accumulation of data to enable timely and appropriate regulatory action

Measurement of electroweak parameters from hadronic and leptonic decays of the Z 0

We have studied the reactions e + e − →hadrons, e + e − , μ + μ − and τ + τ − , in the energy range 88.2 GeV. A total luminosity of 5.5 pb −1 , corresponding to approximately 115000 hadronic and 10000 leptonic Z 0 decays, has been recorded with the L3 detector. From a simultaneous fit to all of our measured cross section data, we obtain assuming lepton universality:Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47890/1/10052_2005_Article_BF01475788.pd