Measurements of flavour-dependent fragmentation functions in {\bf Z^{0} \rightarrow{\rm q}\bar{\rm q}} events

Fragmentation functions for charged particles in events have been measured for bottom (b), charm (c) and light (uds) quarks as well as for all flavours together. The results are based on data recorded between 1990 and 1995 using the OPAL detector at LEP. Event samples with different flavour compositions were formed using reconstructed mesons and secondary vertices. The distributions and the position of their maxima are also presented separately for uds, c and b quark events. The fragmentation function for b quarks is significantly softer than for uds quarks. Received: 29 May 1998 / Published online: 25 January 1999     

The \phi \to \gamma (a_0 (980) + f_0 (980)) \to \gamma {\rm K}\bar {\rm K} decays

We study the decay φ → γK ⁺ K ^? taking into account the scalar meson production φ → γ(a ₀+f ₀ → γK ⁺ K ^? and the final-state radiation. We note that the relative sign between the final-state radiation amplitude and the scalar-meson production amplitude is fixed in the K ⁺ K ^? loop model which describes data on the φ → γf ₀ → γππ and φ → γa ₀ → γπη decays. As consequence, this model predicts the definite interference between the final-state radiation and the scalar resonance production amplitudes. We calculate the mass spectra of the φ → γK ⁺ K ^? decay and the differential cross sections for $e^ + e^ - \to \phi \to \gamma {\rm K}^0 \bar {\rm K}^0 $ reactions.     

Model independent calculation of {\cal{B}}({\bar{B}}^0\rightarrow D^{(*)+} \tau^-{\bar{\nu}})/{\cal{B}}({\bar{B}}^0\rightarrow D^{(*)+} e^-{\bar{\nu}})

Using the formulas for the distribution with non-zero lepton mass and experimentally determined form factors, we calculate the spectra and branching fractions for l = e, and . We obtain the results and . Since we used the experimentally measured form factors, these results are independent of theoretical models of the form factors.     

Recent results on the {K^-_{\rm stop} + A\rightarrow \Sigma^\pm + \pi^\mp + A^{\prime}} reaction with FINUDA

A study of the $K^-_{\rm stop}A\rightarrow \Sigma^\pm\pi^\mp A^{\prime}$ reaction in some p-shell nuclei, i.e., ^6,7Li, ⁹Be, ¹³C and ¹⁶O, performed by the FINUDA experiment, is reported.     

The Semileptonic Decay Modes {\bar{B} \rightarrow D\ell \bar{\nu}} and {\bar{B}_{s} \rightarrow D_{s} \ell \bar{\nu}}: A New Analysis in Potential Model

We consider the Schrödinger equation with a combination of Deng–Fan-type and harmonic terms. To solve the corresponding differential equation, we split the equation to two parts: the parent and the perturbation terms. We use the Nikiforov–Uvarov technique to solve the parent part. For the perturbation part, we apply the series expansion method. Next, using the calculated wave function, we investigate some bottom and charm mesons within the Isgur–Wise function formalism. We present especially semileptonic \({\bar{B} \rightarrow D\ell \bar{\nu}}\) and \({\bar{B}_{s} \rightarrow D_s \ell \bar{\nu }}\) decay widths, branching ratios and \({|V_{cb}|}\) (element of the CKM matrix). Masses of some pseudoscalar mesons are also indicated. Comparisons of our results with experimental values and other approaches are included.     

Analysis of $B^{0}_{d} \to \phi K^{{*0}} $ decay mode with supersymmetry

Motivated by the recent measurement of a low longitudinal polarization fraction in the decay mode , which appears not to be in agreement with the standard model expectation, we analyze this mode in the minimal supersymmetric standard model with the mass insertion approximation. Within the standard model, with the factorization approximation, the longitudinal polarization is expected to be . We find that this anomaly can be explained in the minimal supersymmetric standard model with either the LR or the RL mass insertion approximation. PACS. 13.25.Hw, 11.30.Er, 12.60.Jv Received: 9 May 2005, Revised: 26 July 2005, Published online: 30 August 2005     

\bar K^{0*} (892) andK 0*(892) production at lowp t and the quark parton model

Data on the production of the neutralK ^*(892) resonances at lowp _t by 200 GeVK ^? and π^? is compared with the predictions of various models based on the quark parton model of hadrons.     

Structures of the f 0(980), a 0(980) mesons and the strong coupling constants g_{f_0 K^+ K^-} , g_{a_0 K^+ K^-} with light-cone QCD sum rules

Making the assumption of explicit isospin violation arising from f ₀(980)-a ₀(980) mixing, we take the point of view that the scalar mesons f ₀(980) and a ₀(980) have both strange and non-strange quark-antiquark components and evaluate the strong coupling constants within the framework of the light-cone QCD sum rules approach. The large strong scalar-KK couplings through both the and components , , and will support the hadronic dressing mechanism; furthermore, in spite of the constituent structure differences between the f ₀(980) and a ₀(980) mesons, the strange components have larger strong coupling constants with the K ⁺ K ^- state than the corresponding non-strange ones, and . From the existing controversial values, we cannot reach a general consensus on the strong coupling constants and the mixing angles.Received: 9 January 2004, Revised: 23 July 2004, Published online: 2 September 2004     

Waiting for the discovery of $B^0_d\to K^0\bar K^0$

The CP asymmetries of the decay , which originates from flavor-changing neutral-current processes, and its CP-averaged branching ratio BR offer interesting avenues to explore flavor physics. We show that we may characterize this channel, within the standard model, in a theoretically clean manner through a surface in observable space. In order to extract the relevant information from BR , further information is required, which is provided by the system and the SU(3) flavor symmetry, where we include the leading factorizable SU(3)-breaking corrections and discuss how experimental insights into non-factorizable effects can be obtained. We point out that the standard model implies a lower bound for BR , which is very close to its current experimental upper bound, thereby suggesting that this decay should soon be observed. Moreover, we explore the implications for color suppression in the system, and convert the data for these modes in a peculiar standard-model pattern for the CP-violating observables.Received: 3 August 2004, Published online: 15 November 2004