Massive Quark Production in Electron Positron Annihilation to Order αs2\alpha_s^2

Recent analytical and numerical results for the three-loop polarization function allow to present a phenomenological analysis of the cross section for massive quark production in electron positron annihilation to order $\alpha_s^2$. Numerical predictions based on fixed order perturbation theory are presented for charm and bottom production above 5 and 11.5 GeV, respectively. The contribution from these energy regions to $\alpha(M_Z^2)$, the running QED coupling constant at scale M_Z, are given. The dominant terms close to threshold, i.e. in an expansion for small quark velocity $\beta$, are presented.Comment: 26 pages (Latex), 16 figures (Postscript

Determination of αs\alpha_s and heavy quark masses from recent measurements of R(s)R(s)

In this paper we compare recent experimental data for the total cross section $\sigma(e^+e^-\to{hadrons})$ with the up-to-date theoretical prediction of perturbative QCD for those energies where perturbation theory is reliable. The excellent agreement suggests the determination of the strong coupling $\alpha_s$ from the measurements in the continuum. The precise data from the charm threshold region, when combined with the recent evaluation of moments with three loop accurracy, lead to a direct determination of the short distance $\bar{\rm MS}$ charm quark mass. Our result for the strong coupling constant $\alpha_s^{(4)}(5 {GeV})=0.235^{+0.047}_{-0.047}$ corresponds to $\alpha_s^{(5)}(M_Z)=0.124^{+0.011}_{-0.014}$, for the charmed quark mass we find $m_c(m_c)=1.304(27)$. Applying the same approach to the bottom quark we obtain $m_b(m_b)=4.191(51)$ GeV. Whereas our result for $\alpha_s(M_Z)$ serves as a useful cross check for other more precise determinations, our values for the charm and bottom quark masses are more accurate than other recent analyses.Comment: 16 pages, minor change in numerical result for mb(mb

The Impact of σ(e+e−→hadrons)\sigma(e^+e^-\to {hadrons}) Measurements at Intermediate Energies on the Parameters of the Standard Model

We discuss the impact of precision measurements of $\sigma(e^+e^-\to {hadrons})$ in the center-of-mass range between 3 and 12 GeV, including improvements in the electronic widths of the narrow charmonium and bottonium resonances, on the determination of parameters of the Standard Model. In particular we discuss the impact of potential improvements on the extraction of the strong coupling constant $\alpha_s$, on the evaluation of the hadronic contributions to the electromagnetic coupling $\alpha(M_Z)$, and the determination of the charm and bottom quark masses.Comment: 8 page

Determination of the strong coupling constant from the CLEO measurement of the total hadronic cross section in e+e−e^+e^- annihilation below 10.56 GeV

Using recent CLEO III results for the cross section for $e^+e^- \to {\rm hadrons}$ at seven centre-of-mass energies between 6.964 and 10.538 GeV, we derive a value for the strong coupling constant $\alpha_s(M_Z^2)=0.110_{-0.012}^{-0.010}{}_{-0.011}^{+0.010}$ where the uncertainties are uncorrelated and correlated, respectively. Our result differs significantly from the one derived by CLEO III, as a consequence of inclusion of quark mass effects and the proper matching between the effective theories with four and five flavours. Combining this new result with an analysis based on earlier cross section measurements in the energy region between 2 and 10.6 GeV, we obtain $\alpha_s(M_Z^2)=0.119^{+0.009}_{-0.011}$, well consistent with the current world average

Shapley Supercluster Survey: Ram-Pressure Stripping vs. Tidal Interactions in the Shapley Supercluster

We present two new examples of galaxies undergoing transformation in the Shapley supercluster core. These low-mass (stellar mass from 0.4E10 to 1E10 Msun) galaxies are members of the two clusters SC-1329-313 (z=0.045) and SC-1327-312 (z=0.049). Integral-field spectroscopy complemented by imaging in ugriK bands and in Halpha narrow-band are used to disentangle the effects of tidal interaction (TI) and ram-pressure stripping (RPS). In both galaxies, SOS-61086 and SOS-90630, we observe one-sided extraplanar ionized gas extending respectively 30kpc and 41kpc in projection from their disks. The galaxies' gaseous disks are truncated and the kinematics of the stellar and gas components are decoupled, supporting the RPS scenario. The emission of the ionized gas extends in the direction of a possible companion for both galaxies suggesting a TI. The overall gas velocity field of SOS-61086 is reproduced by ad hoc N-body/hydrodynamical simulations of RPS acting almost face-on and starting about 250Myr ago, consistent with the age of the young stellar populations. A link between the observed gas stripping and the cluster-cluster interaction experienced by SC-1329-313 and A3562 is suggested. Simulations of ram pressure acting almost edge-on are able to fully reproduce the gas velocity field of SOS-90630, but cannot at the same time reproduce the extended tail of outflowing gas. This suggests that an additional disturbance from a TI is required. This study adds a piece of evidence that RPS may take place in different environments with different impacts and witnesses the possible effect of cluster-cluster merger on RPS.Comment: 27 pages, 28 figures, MNRAS accepte