Decays of mesons with charm quarks on the lattice

We investigate mesons containing charm quarks on fine lattices with a^{-1} \sim 5 GeV. The quenched approximation is employed using the Wilson gauge action at \beta = 6.6 and nonperturbatively O(a) improved Wilson quarks. We present results for decay constants using various interpolating fields and give preliminary results for form factors of semileptonic decays of D_s mesons to light pseudoscalar mesons.Comment: 7 pages, 3 figures, talk presented at the XXV International Symposium on Lattice Field Theory, 30 July - 4 August 2007, Regensburg, German

QCD dynamics in a constant chromomagnetic field

We investigate the phase transition in full QCD with two flavors of staggered fermions in presence of a constant abelian chromomagnetic field. We find that the critical temperature depends on the strength of the chromomagnetic field and that the deconfined phase extends to very low temperatures for strong enough fields. As in the case of zero external field, a single transition is detected, within statistical uncertainties, where both deconfinement and chiral symmetry restoration take place. We also find that the chiral condensate increases with the strength of the chromomagnetic field.Comment: 18 pages, 8 figures, 1 tabl

Semileptonic form factors D → \rightarrow π \pi , K and B → \rightarrow π \pi , K from a fine lattice

We extract the form factors relevant for semileptonic decays of D and B mesons from a relativistic computation on a fine lattice in the quenched approximation. The lattice spacing is a = 0.04 fm (corresponding to a -1 = 4.97 GeV), which allows us to run very close to the physical B meson mass, and to reduce the systematic errors associated with the extrapolation in terms of a heavy-quark expansion. For decays of D and Ds mesons, our results for the physical form factors at \ensuremath q^2 = 0 are as follows: \ensuremath f_+^{D\rightarrow\pi}(0) = 0.74(6)(4) , \ensuremath f_+^{D \rightarrow K}(0) = 0.78(5)(4) and \ensuremath f_+^{D_s \rightarrow K} (0) = 0.68(4)(3) . Similarly, for B and Bs we find \ensuremath f_+^{B\rightarrow\pi}(0) = 0.27(7)(5) , \ensuremath f_+^{B\rightarrow K} (0) = 0.32(6)(6) and \ensuremath f_+^{B_s\rightarrow K}(0) = 0.23(5)(4) . We compare our results with other quenched and unquenched lattice calculations, as well as with light-cone sum rule predictions, finding good agreemen

Decay constants of charm and beauty pseudoscalar heavy-light mesons on fine lattices

We compute decay constants of heavy-light mesons in quenched lattice QCD with a lattice spacing of a ~ 0.04 fm using non-perturbatively O(a) improved Wilson fermions and O(a) improved currents. We obtain f_{D_s} = 220(6)(5)(11) MeV, f_D = 206(6)(3)(22) MeV, f_{B_s} = 205(7)(26)(17) MeV and f_B = 190(8)(23)(25) MeV, using the Sommer parameter r_0 = 0.5 fm to set the scale. The first error is statistical, the second systematic and the third from assuming a +-10% uncertainty in the experimental value of r_0. A detailed discussion is given in the text. We also present results for the meson decay constants f_K and f_\pi and the \rho meson mass.Comment: 13 pages, 7 figures. Replaced version contains analysis in terms of improved quark masses instead of bare quark masses, result for f_B changed by 1 MeV. Several typos corrected, in particular error bars in table 4. Version accepted in PL

A lattice calculation of vector meson couplings to the vector and tensor currents using chirally improved fermions

We present a quenched lattice calculation of $f_V^\perp/f_V$, the coupling of vector mesons to the tensor current normalized by the vector meson decay constant. The chirally improved lattice Dirac operator, which allows us to reach small quark masses, is used. We put emphasis on analyzing the quark mass dependence of $f_V^\perp/f_V$ and find only a rather weak dependence. Our results at the $\rho$ and $\phi$ masses agree well with QCD sum rule calculations and those from previous lattice studies.Comment: 6 pages, 3 figures, one sentence remove

Decay Constants of B and D Mesons from Non-pertubatively Improved Lattice QCD

The decay constants of B and D mesons are computed in quenched lattice QCD at two different values of the coupling. The action and operators are ? (a) improved with non-perturbative coefficients where available. The results and systematic errors are discussed in detail. Results for vector decay constants, flavour symmetry breaking ratios of decay constants, the pseudoscalar-vector mass splitting and D meson masses are also presented

A Stochastic Soft Constraints Fuzzy Model for a Portfolio Selection Problem

The financial market behavior is affected by several non-probabilistic factors such as vagueness and ambiguity. In this paper we develop a multistage stochastic soft constraints fuzzy program with recourse in order to capture both uncertainty and imprecision as well as to solve a portfolio management problem. The results we obtained confirm the studies carried out in literature addressed to integrate stochastic and possibilistic programming

Hotel chain performance: a gravity-DEA approach

This paper explores the evolution of the efficiency of a hotel chain and its implications in terms of competitiveness. A gravity model and a data envelopment analysis (DEA) are implemented in a dynamic framework. The former generates the tourism demand towards each hotel of the chain whereas DEA Window analysis is run to capture efficiency changes over time. A DEA based Malmquist productivity index is used to measure the productivity change and to decompose any change into the catching-up and the frontier-shift effect. We find that policies implemented according to DEA Window analysis increase the efficiency scores for the hotel chain and its competitiveness

The Dynamics of Quote Prices in an Artificial Financial Market with Learning Effects

In this paper we study the evolution of bid and ask prices in an electronic financial market populated by portfolio traders who optimally choose their allocation strategy on the basis of their views about market conditions. We design an order book market system where agents enter the market sequentially and trade to adjust their portfolio according to their optimal target allocations. They apply a copula function to generate the joint distribution of returns to be used to determine the optimal portfolio allocations. We create asynchronous updating assuming that different groups of agents entered the market at different moments in time. We simplify the optimization problem assuming that investors are myopic: at the beginning of the investment horizon they choose their portfolios as if there will be no further trading