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We present a nonperturbative dynamical study of $mu^+mu^-$ production in proton-nucleus and nucleus-nucleus collisions at SPS energies on the basis of the covariant transport approach HSD. For p + W reactions at 200 GeV bombarding energy the dimuon yield for invariant masses m $leq $ 1.6 GeV is found to be dominated by the decays of the $eta, rho, omega$ and $Phi$ mesons. For 200 GeV/A S + W collisions, however, the dimuon yield shows an additional large contribution from $pi^+pi^-$, $K^+K^-$ and $pi rho$ channels. We find that for `free meson masses and form factors the experimental cross section is clearly underestimated for S + W in the invariant mass range 0.35 GeV $leq$ m $leq$ 0.65 GeV and that the HELIOS-3 data can only be reproduced within a hadronic scenario, if the $rho/omega$-meson mass drops with baryon density. This finding suggests a partial restoration of chiral symmetry in S + W collisions at SPS energies.
In the absence of direct evidence for New Physics at present LHC energies, the focus is set on the anomalies and discrepancies recently observed in rare $b to sellell$ transitions which can be interpreted as indirect hints. Global fits have shown tha
We analyse the results recently presented on the $B^{+} to K^{*+} mu^+ mu^-$ angular observables by the LHCb Collaboration which show indications for New Physics beyond the Standard Model. Within a model-independent analysis, we compare the fit resul
We report on recent developments in the phenomenology of exclusive b -> s mu^+ mu^- decays in testing the standard model and explore its borders: the benefits of the region of large dimuon invariant masses and the exploitation of the angular distribu
Supposing only Lorentz and the gauge invariances of the Lagrangian, we derive energy and angular distributions for $tau^pm to mu^pm mu^pm mu^mp$ lepton flavor violating decay process. Using these results, we discuss methods to determine the parameter
We present an angular analysis of the $B^{+}rightarrow K^{ast+}(rightarrow K_{S}^{0}pi^{+})mu^{+}mu^{-}$ decay using 9$,mbox{fb}^{-1}$ of $pp$ collision data collected with the LHCb experiment. For the first time, the full set of CP-averaged angular