Streptococcus (S.) suis causes meningitis and various other diseases in pigs and humans. Healthy piglets carrying virulent S. suis strains on their mucosal surfaces are epidemiologically very important. The objective of this study was to establish an intranasal S. suis mouse model for invasion and colonisation of the respiratory tract. CD1 mice were intranasally infected with a highly virulent S. suis serotype 2 strain under different conditions. Clinical, histological and bacteriological screenings revealed that invasion of host tissue occurred in the majority of mice only after predisposition with 12.5 µl 1 % acetic acid per nostril. Severe fibrinosuppurative or purulent necrotizing pneumonia associated with S. suis was a common manifestation. Furthermore, a novel model to study nasopharyngeal colonisation was established by reducing the volume of 1 % acetic acid per nostril to 5 µl prior S. suis application. This model mimics asymptomatic carriage in swine as all mice carried S. suis on their respiratory mucosa 7 days post infection in moderate to high numbers without development of pneumonia or any other invasive S. suis disease. This intranasal S. suis model was applied to investigate the function of suilysin in colonisation. Though an isogenic suilysin mutant was isolated from the upper respiratory tract at a lower recovery rate than its wild type parental strain 14 days post infection, differences were not significant and did not indicate severe attenuation in colonisation. In conclusion, this work describes the first intranasal mice model to study colonisation of the respiratory tract by a highly virulent S. suis pathotype.

We report transverse momentum (p_{T}≤15  GeV/c) spectra of π^{±}, K^{±}, p, p[over ¯], K_{S}^{0}, and ρ^{0} at midrapidity in p+p and Au+Au collisions at sqrt[s_{NN}]=200  GeV. Perturbative QCD calculations are consistent with π^{±} spectra in p+p collisions but do not reproduce K and p(p[over ¯]) spectra. The observed decreasing antiparticle-to-particle ratios with increasing p_{T} provide experimental evidence for varying quark and gluon jet contributions to high-p_{T} hadron yields. The relative hadron abundances in Au+Au at p_{T}≳8  GeV/c are measured to be similar to the p+p results, despite the expected Casimir effect for parton energy loss.

We report new STAR measurements of midrapidity yields for the Λ, Λ[over ¯], K_{S}^{0}, Ξ^{-}, Ξ[over ¯]^{+}, Ω^{-}, Ω[over ¯]^{+} particles in Cu+Cu collisions at sqrt[s_{NN}]=200  GeV, and midrapidity yields for the Λ, Λ[over ¯], K_{S}^{0} particles in Au+Au at sqrt[s_{NN}]=200  GeV. We show that, at a given number of participating nucleons, the production of strange hadrons is higher in Cu+Cu collisions than in Au+Au collisions at the same center-of-mass energy. We find that aspects of the enhancement factors for all particles can be described by a parametrization based on the fraction of participants that undergo multiple collisions.

Flow coefficients v_{n} for n=2, 3, 4, characterizing the anisotropic collective flow in Au+Au collisions at sqrt[s_{NN}]=200  GeV, are measured relative to event planes Ψ_{n}, determined at large rapidity. We report v_{n} as a function of transverse momentum and collision centrality, and study the correlations among the event planes of different order n. The v_{n} are well described by hydrodynamic models which employ a Glauber Monte Carlo initial state geometry with fluctuations, providing additional constraining power on the interplay between initial conditions and the effects of viscosity as the system evolves. This new constraint can serve to improve the precision of the extracted shear viscosity to entropy density ratio η/s.

Back-to-back hadron pair yields in d+Au and p+p collisions at √s(NN)=200 GeV were measured with the PHENIX detector at the Relativistic Heavy Ion Collider. Rapidity separated hadron pairs were detected with the trigger hadron at pseudorapidity |η|<0.35 and the associated hadron at forward rapidity (deuteron direction, 3.0<η<3.8). Pairs were also detected with both hadrons measured at forward rapidity; in this case, the yield of back-to-back hadron pairs in d+Au collisions with small impact parameters is observed to be suppressed by a factor of 10 relative to p+p collisions. The kinematics of these pairs is expected to probe partons in the Au nucleus with a low fraction x of the nucleon momenta, where the gluon densities rise sharply. The observed suppression as a function of nuclear thickness, p(T), and η points to cold nuclear matter effects arising at high parton densities.

We present measurements of J/ψ yields in d+Au collisions at sqrt[s(NN)]=200  GeV recorded by the PHENIX experiment and compare them with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/ψ rapidity (-2.2<y<2.4) with high statistical precision and are compared with two theoretical models: one with nuclear shadowing combined with final state breakup and one with coherent gluon saturation effects. In order to remove model dependent systematic uncertainties we also compare the data to a simple geometric model. The forward rapidity data are inconsistent with nuclear modifications that are linear or exponential in the density weighted longitudinal thickness, such as those from the final state breakup of the bound state.

We report the first measurement of the parity-violating single-spin asymmetries for midrapidity decay positrons and electrons from W+ and W- boson production in longitudinally polarized proton-proton collisions at sqrt[s]= 500 GeV by the STAR experiment at RHIC. The measured asymmetries, A(L)(W+)=-0.27 ± 0.10(stat.) ± 0.02(syst.) ± 0.03(norm.) and A(L)(W-)= 0.14 ± 0.19(stat.) ± 0.02(syst.) ± 0.01(norm.), are consistent with theory predictions, which are large and of opposite sign. These predictions are based on polarized quark and antiquark distribution functions constrained by polarized deep-inelastic scattering measurements.

The production of e;{+}e;{-} pairs for m_{e;{+}e;{-}}<0.3 GeV/c;{2} and 1<p_{T}<5 GeV/c is measured in p+p and Au+Au collisions at sqrt[s_{NN}]=200 GeV. An enhanced yield above hadronic sources is observed. Treating the excess as photon internal conversions, the invariant yield of direct photons is deduced. In central Au+Au collisions, the excess of the direct photon yield over p+p is exponential in transverse momentum, with an inverse slope T=221+/-19;{stat}+/-19;{syst} MeV. Hydrodynamical models with initial temperatures ranging from T_{init} approximately 300-600 MeV at times of approximately 0.6-0.15 fm/c after the collision are in qualitative agreement with the data. Lattice QCD predicts a phase transition to quark gluon plasma at approximately 170 MeV.

Parity-odd domains, corresponding to nontrivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the system's orbital momentum axis. We investigate a three-particle azimuthal correlator which is a P even observable, but directly sensitive to the charge separation effect. We report measurements of charged hadrons near center-of-mass rapidity with this observable in Au+Au and Cu+Cu collisions at sqrt[s_{NN}]=200 GeV using the STAR detector. A signal consistent with several expectations from the theory is detected. We discuss possible contributions from other effects that are not related to parity violation.

Nuclear collisions recreate conditions in the universe microseconds after the Big Bang. Only a very small fraction of the emitted fragments are light nuclei, but these states are of fundamental interest. We report the observation of antihypertritons-comprised of an antiproton, antineutron, and antilambda hyperon-produced by colliding gold nuclei at high energy. Our analysis yields 70 +/- 17 antihypertritons ($${}_{\overline{\Lambda }};{3}\overline{\mathrm{H}}$$) and 157 +/- 30 hypertritons ($${}_{\Lambda };{3}\mathrm{H}$$). The measured yields of $${}_{\Lambda };{3}\mathrm{H}$$($${}_{\overline{\Lambda }};{3}\overline{\mathrm{H}}$$) and (3)He ((3)$$\overline{\mathrm{He}}$$) are similar, suggesting an equilibrium in coordinate and momentum space populations of up, down, and strange quarks and antiquarks, unlike the pattern observed at lower collision energies. The production and properties of antinuclei, and nuclei containing strange quarks, have implications spanning nuclear/particle physics, astrophysics, and cosmology.