An interpolation of the vacuum polarization function for the evaluation of hadronic contributions to the muon anomalous magnetic moment

We propose a simple parameterization of the two-point correlator of hadronic electromagnetic currents for the evaluation of the hadronic contributions to the muon anomalous magnetic moment. The parameterization is explicitly done in the Euclidean domain. The model function contains a phenomenological parameter which provides an infrared cutoff to guarantee the smooth behavior of the correlator at the origin in accordance with experimental data in e+ e- annihilation. After fixing a numerical value for this parameter from the leading order hadronic contribution to the muon anomalous magnetic moment the next-to-leading order results related to the vacuum polarization function are accurately reproduced. The properties of the four-point correlator of hadronic electromagnetic currents as for instance the so-called light-by-light scattering amplitude relevant for the calculation of the muon anomalous magnetic moment are briefly discussed.Comment: 23 pages in LaTeX, 11 PostScript figures included in the tex

Analytical calculation of heavy baryon correlators in NLO of perturbative QCD

We present analytical next-to-leading order results for the correlator of baryonic currents at the three-loop level with one finite mass quark. We obtain the massless and the HQET limits of the correlator as particular cases from the general formula, we also give explicit expressions for the moments of the spectral density. Calculations have been performed with an extensive use of the symbolic manipulation programs MATHEMATICA and REDUCE.Comment: 16 pages in LaTeX, including 7 Postscript figures, contribution to the "VII International Workshop on Advanced Computing and Analysis Techniques in Physics Research (ACAT2000)", Oct 16-20, 2000, Fermi National Laboratory, Batavia, Illinois, USA, to appear in the proceeding

O(\alpha_s) Corrections to Longitudinal Spin-Spin Correlations in e+e- -> q qbar

We calculate the $O(\alpha_s)$ corrections to longitudinal spin-spin correlations in $e^+e^-\to q\bar q$. For top quark pair production the $O(\alpha_s)$ corrections to the longitudinal spin-spin asymmetry amount to less than 1% in the $q^2$-range from above $t\bar t$-treshold up to $\sqrt{q^2}= 1000 GeV$. In the $e^+e^-\to b\bar b$ case the $O(\alpha_s)$ corrections reduce the asymmetry value from its $m=0$ value of -1 to approximately -0.96 for $q^2$-values around the Z-peak. This reduction can be traced to finite anomalous contributions from residual mass effects which survive the $m\to 0$ limit. We discuss the role of the anomalous contributions and the pattern of how they contribute to spin-flip and no-flip terms.Comment: 10 pages, 2 postscript figure

Analyticity, crossing and the absorptive parts of the one-loop contributions to the quark-quark-gluon gauge boson four-point function

Starting from the known one-loop result for the $e^{+}e^{-}$-annihilation process $e^{+}e^{-}\stackrel{\gamma,Z} {\longrightarrow} q\bar{q}g$ with massless quarks we employ analyticity and crossing to determine the absorptive parts of the corresponding one-loop contributions in Deep Inelastic Scattering (DIS) and in the Drell-Yan process (DY). Whereas the ${\cal O}(\alpha_s^2)$ absorptive parts generate a non-measurable phase factor in the $e^{+}e^{-}$-annihilation channel one obtains measurable phase effects from the one-loop contributions in the deep inelastic and in the Drell-Yan case. We compare our results with the results of previous calculations where the absorptive parts in DIS and in the DY process were calculated directly in the respective channels. We also present some new results on the dispersive and absorptive contributions of the triangle anomaly graph to the DIS process.Comment: 23 pages, 5 figures, typos corrected. Version to appear in Phys. Rev.

Beyond Nationaloper. For a critique of methodological nationalism in reading nineteenth-century Italian and German opera

This article challenges traditional narratives that have tended to highlight the role of opera as a tool of political nationalism in nineteenth-century Europe. Instead, I will show how opera (both the form and the repertoire) served as a means of creating cultural and intellectual connections between peoples, and how it participated in the emergence of a European public. Claims that particular operas played a role in rousing nationalist sentiment are often methodologically unsound, due to the limitations of related sources of reception; or they are based on myths that were constructed long after these works’ original production. Moreover, even works written or described at the time as explicitly ‘national’ operas often relied on musical techniques amalgamated from different national contexts, raising questions over their classification in terms of national culture. Instead, Italian opera in particular assumed a central role in building cultural bridges between and within nations and polities. This was especially the case for the Habsburg monarchy, where opera was understood as a reference to Italy’s humanist legacy, based on a long tradition of reading opera as the reinvention of Greek drama. After 1815 and throughout the 1820s, the triumph of Rossini’s works on almost every stage in Europe shows how opera transcended barriers between peoples, states and nations. A mere ‘national’ reading of such works risks missing the point of why opera became a European art form of a truly global appeal