Non-factorizable contributions to Bd0ˉ→Ds(∗)Ds(∗)ˉ\bar{B^0_d} \to D_s^{(*)} \bar{D_s^{(*)}}

It is pointed out that decays of the type $B \to D \bar{D}$ have no factorizable contributions, unless at least one of the charmed mesons in the final state is a vector meson. The dominant contributions to the decay amplitudes arise from chiral loop contributions and tree level amplitudes generated by soft gluon emissions forming a gluon condensate. We predict that the branching ratios for the processes $\bar B^0 \to D_s^+ D_s^-$, $\bar B^0 \to D_s^{+*} D_s^-$ and $\bar B^0 \to D_s^+ D_s^{-*}$ are all of order $(3- 4) \times 10^{-4}$, while $\bar B^0 \to D_s^{+*} D_s^{-*}$ has a branching ratio 5 to 10 times bigger. We emphasize that the branching ratios are sensitive to $1/m_c$ corrections.Comment: 4 pages, 4 figures. Based on talk by J.O. Eeg at BEACH 2004, 6th international conference on Hyperons, Charm and Beauty Hadrons, Illionois Institute of Technology, Chicago, june. 27 - july 3, 200

The \beta-term for D^* --> D \gamma within a heavy-light chiral quark model

We present a calculation of the \beta-term for D^* --> D gamma within a heavy-light chiral quark model. Within the model, soft gluon effects in terms of the gluon condensate with lowest dimension are included. Also, calculations of 1/m_c corrections are performed. We find that the value of \beta is rather sensitive to the constituent quark mass compared to other quantities calculated within the same model. Also, to obtain a value close to the experimental value, one has to choose a constituent light quark mass larger than for other quantities studied in previous papers. For a light quark mass in the range 250 to 300 MeV and a quark condensate in the range -(250-270 MeV)^3 we find the value (2.5 +- 0.6) GeV^-1. This value is in agreement with the value of \beta extracted from experiment 2.7 +- 0.2 GeV^-1.Comment: 16 pages, 5 figure

Non-factorizable effects in B-anti-B mixing

We study the B-parameter (``bag factor'') for B-anti-B mixing within a recently developed heavy-light chiral quark model. Non-factorizable contributions in terms of gluon condensates and chiral corrections are calculated. In addition, we also consider 1/m_Q corrections within heavy quark effective field theory. Perturbative QCD effects below \mu = m_b known from other work are also included. Considering two sets of input parameters, we find that the renormalization invariant B-parameter is B = 1.51 +- 0.09 for B_d and B = 1.40 +- 0.16 for B_s.Comment: 23 pages, 7 figures, RevTex 4 Small changes, included more details in the tex

Color suppressed contributions to the decay modes B_{d,s} -> D_{s,d} D_{s,d}, B_{d,s} -> D_{s,d} D^*_{s,d}, and B_{d,s} -> D^*_{s,d} D^*_{s,d}

The amplitudes for decays of the type $B_{d,s} \to D_{s,d} D_{s,d}$, have no factorizable contributions, while $B_{d,s} \to D_{s,d} D^*_{s,d}$, and $B_{d,s} \to D^*_{s,d} D^*_{s,d}$ have relatively small factorizable contributions through the annihilation mechanism. The dominant contributions to the decay amplitudes arise from chiral loop contributions and tree level amplitudes which can be obtained in terms of soft gluon emissions forming a gluon condensate. We predict that the branching ratios for the processes $\bar B^0_d \to D_s^+ D_s^-$, $\bar B^0_d \to D_s^{+*} D_s^-$ and $\bar B^0_d \to D_s^+ D_s^{-*}$ are all of order $(2- 3) \times 10^{-4}$, while $\bar B^0_s \to D_d^+ D_d^-$, $\bar B^0_s \to D_d^{+*} D_d^-$ and $\bar B^0_s \to D_d^+ D_d^{-*}$ are of order $(4- 7) \times 10^{-3}$. We obtain branching ratios for two $D^*$'s in the final state of order two times bigger.Comment: 15 pages, 4 figure

On the color suppressed contribution to $\bar{B_{d}^0} \rightarrow \, \pi^0 \pi^{0}

The decay modes of the type $B \rightarrow \pi \, \pi$ are dynamically different. For the case $\bar{B_{d}^0} \rightarrow \, \pi^+ \pi^-$ there is a substantial factorized contribution which dominates. In contrast, the decay mode $\bar{B_{d}^0} \rightarrow \, \pi^0 \pi^{0}$ has a small factorized contribution, being proportional to a small Wilson coefficient combination. However, for the decay mode $\bar{B_{d}^0} \rightarrow \, \pi^0 \pi^{0}$ there is a sizeable nonfactorizable (color suppressed) contribution due to soft (long distance) interactions, which dominate the amplitude. We estimate the branching ratio for the mode $\bar{B_{d}^0} \rightarrow \, \pi^0 \pi^{0}$ in the heavy quark limit for the $b$- quark. In order to estimate color suppressed contributions we treat the energetic light ($u,d,s$) quark within a variant of Large Energy Effective Theory combined with a recent extension of chiral quark models in terms of model- dependent gluon condensates. We find that our calculated color suppressed amplitude is suppressed by a factor of order $\Lambda_{QCD}/m_b$ with respect to the factorizable amplitude, as it should according to QCD-factorization. Further, for reasonable values of the constituent quark mass and the gluon condensate, the calculated nonfactorizable amplitude for $\bar{B_{d}^0} \rightarrow \, \pi^0 \pi^{0}$ can easily accomodate the experimental value. Unfortunately, the color suppressed amplitude is very sensitive to the values of these model dependent parameters. Therefore fine-tuning is necessary in order to obtain an amplitude compatible with the experimental result for $\bar{B_{d}^0} \rightarrow \, \pi^0 \pi^{0}$. A possible link to the triangle anomaly is discussed.Comment: The submitted Latex version correspond to 23 pages in ps-version and contains 4 figure

A Heavy-Light Chiral Quark Model

We present a new chiral quark model for mesons involving a heavy and a light (anti-) quark. The model relates various combinations of a quark - meson coupling constant and loop integrals to physical quantities. Then, some quantities may be predicted and some used as input. The extension from other similar models is that the present model includes the lowest order gluon condensate of the order (300 MeV)^4 determined by the mass splitting of the 0^- and the 1^- heavy meson states. Within the model, we find a reasonable description of parameters such as the decay constants f_B and f_D, the Isgur-Wise function and the axial vector coupling g_A in chiral perturbation theory for light and heavy mesons.Comment: 31 pages, 13 figures, RevTex4.

B0 - anti-B0 mixing beyond factorization

We present a calculation of the B0 - anti-B0 mixing matrix element in the framework of QCD sum rules for three-point functions. We compute alpha_s corrections to a three-point function at the three-loop level in QCD perturbation theory, which allows one to extract the matrix element with next-to-leading order (NLO) accuracy. This calculation is imperative for a consistent evaluation of experimentally-measured mixing parameters since the coefficient functions of the effective Hamiltonian for B0 - anti-B0 mixing are known at NLO. We find that radiative corrections violate factorization at NLO; this violation is under full control and amounts to 10%.Comment: 4 pages, 3 figures, LaTeX2

Lubricating Performance of Polymer-Coated Liposomes

Dry mouth is a troublesome condition linked to lubrication failure and leads to other diseases such as fungal infections and wounds in the oral cavity. There are many commercial salivary substitutes in the market, but none with a long-lasting lubrication effect. Polymer-coated liposomes can be an interesting formulation strategy for retrieving the symptoms of dry mouth by mimicking the micelles of saliva. In the present study, polymer coated-liposomes were prepared by the conventional thin film method and subsequently coated with three different polymers with different charge densities; alginate, chitosan and hydrophobically modified ethyl hydroxyethyl cellulose (HM-EHEC). The prepared polymer-coated liposomes were studied concerning their lubricating properties using a ball-on-disc tribometer at 2 N load at 37 °C, and their flow behaviours were also measured. Solutions of the pure polymers and dispersions of the uncoated liposomes were also studied to investigate any contributions from the individual components. A commercial dry mouth product based on HEC (hydroxyethyl cellulose) and glycerol was also included. The formulations were measured as soon as possible after preparation and some of them after >4 weeks. Results demonstrated that all the positively-charged formulations (chitosan, positive liposomes and chitosan-coated liposomes) had superior lubricating properties with friction coefficients (μ < 0.1) at orally relevant speeds (50 mm/s) as compared to the neutral or negatively-charged systems. At boundary lubrication conditions (3 mm/s), the chitosan-coated liposomes obtained an even lower friction force than the individual components, thus indicating a synergistic effect between the polymer and the liposome