Heavy Flavour Physics at HERA - a Survey

At the HERA collider at DESY, high energy electron and positron beams interact with proton beams. A review is presented of the variety of ways in which these collisions produce final states containing charm and beauty quarks.Comment: 45 pages including 30 figures. Submitted to International Journal of Modern Physics

The lightest scalar glueball

Recently performed investigations of meson spectra allow us to determine the resonance structure for the waves $IJ^{PC}=00^{++}$, $10^{++}$, $02^{++}$, $12^{++}$ = $IJ^P= 1/2 0^+$ in the mass region up to 1900 MeV, thus establishing the meson multiplets $1^3P_0q\bar q$ and $2^3P_0q\bar q$. Experimental data demonstrate that there are five scalar/isoscalar states in this mass region. Four of them are $q\bar q$ states, that is, members of the $1^3P_0q\bar q$ and $2^3P_0q\bar q$ nonets, while the fifth state is an extra one not accomodated by $q \bar q$ systematics; it has the properties of the lightest scalar glueball. Analysis of the $00^{++}$-wave performed within the framework of the dispersion relation technique allows us to reconstruct the mixing of a pure gluonium with neighbouring scalar $q \bar q$ states belonging to $1^3P_0q\bar q$ and $2^3P_0q\bar q$ nonets: three scalar mesons share the gluonium state between each other -- those are two comparatively narrow resonances $f_0(1300)$ and $f_0(1500)$ and a broad resonance $f_0(1530^{+90}_{-250})$. The broad state is a descendant of the gluonium, keeping about 40-50% of its component.Comment: 48 pages, LaTeX, 25 PostScript figures, epsfig.sty. Submitted to Russian Journal Uspekhi Fiz. Nauk (Phys-Uspekhi

B→ππB \to \pi \pi decays: branching ratios and CP asymmetries

Theoretically motivated smallness of the penguin amplitude in $B \to \pi \pi$ decays allowes to calculate the value of the unitarity triangle angle $\alpha (\phi_2)$ with good accuracy. The relatively large branching ratio of the decay into $\pi^0 \pi^0$ is explained by the large value of FSI phase difference between $\Delta I = 1/2$ and $\Delta I = 3/2$ tree amplitudes.Comment: Analysis of direct CPV asymmetries is expanded; the relation with that in $K\pi$ decays is discussed. Submitted to Yad. Fi