Heavy-light mesons with staggered light quarks

We demonstrate the viability of improved staggered light quarks in studies of heavy-light systems. Our method for constructing heavy-light operators exploits the close relation between naive and staggered fermions. The new approach is tested on quenched configurations using several staggered actionsn combined with nonrelativistic heavy quarks. The B_s meson kinetic mass, the hyperfine and 1P-1S splittings in B_s, and the decay constant f_{B_s} are calculated and compared to previous quenched lattice studies. An important technical detail, Bayesian curve-fitting, is discussed at length.Comment: 38 pages, figures included. v2: Entry in Table IX corrected and other minor changes, version appearing in Phys. Rev.

Exploring the Expression of Cardiac Regulators in a Vertebrate Extremophile: The Cichlid Fish Oreochromis (Alcolapia) alcalica

Although it is widely accepted that the cellular and molecular mechanisms of vertebratecardiac development are evolutionarily conserved, this is on the basis of data from only a fewmodel organisms suited to laboratory studies. Here, we investigate gene expression during cardiacdevelopment in the extremophile, non-model fish species, Oreochromis (Alcolapia) alcalica. Wefirst characterise the early development of O. alcalica and observe extensive vascularisation across the yolk prior to hatching. We further investigate heart development by identifying andcloning O. alcalica orthologues of conserved cardiac transcription factors gata4, tbx5, and mef2cfor analysis by in situ hybridisation. Expression of these three key cardiac developmentalregulators also reveals other aspects of O. alcalica development, as these genes are expressed indeveloping blood, limb, eyes, and muscle, as well as the heart. Our data support the notion that O.alcalica is a direct-developing vertebrate that shares the highly conserved molecular regulation ofthe vertebrate body plan. However, the expression of gata4 in O. alcalica reveals interestingdifferences in the development of the circulatory system distinct from that of the well-studiedzebrafish. Understanding the development of O. alcalica embryos is an important step towardsproviding a model for future research into the adaptation to extreme conditions; this is particularlyrelevant given that anthropogenic-driven climate change will likely result in more freshwaterorganisms being exposed to less favourable conditions

The nucleon's strange electromagnetic and scalar matrix elements

Quenched lattice QCD simulations and quenched chiral perturbation theory are used together for this study of strangeness in the nucleon. Dependences of the matrix elements on strange quark mass, valence quark mass and momentum transfer are discussed in both the lattice and chiral frameworks. The combined results of this study are in good agreement with existing experimental data and predictions are made for upcoming experiments. Possible future refinements of the theoretical method are suggested.Comment: 24 pages, 9 figure

Study of B→D∗∗πB\to D^{**} \pi decays

We investigate the production of the novel $P$-wave mesons $D^{*}_{0}$ and $D^{\prime}_{1} (D_{1})$, identified as $J^{P}=0^+$ and $1^+$, in heavy $B$ meson decays, respectively. With the heavy quark limit, we give our modelling wave functions for the scalar meson $D^{*}_{0}$. Based on the assumptions of color transparency and factorization theorem, we estimate the branching ratios of $B\to D^{*}_{0} \pi$ decays in terms of the obtained wave functions. Some remarks on $D^{(\prime)}_{1}$ productions are also presented.Comment: 16 pages, 2 figures, Revtex4, to be published in Phys. Rev.

Sea quark effects in B Spectroscopy and Decay Constants

We present comprehensive results for the spectrum and decay constants of hadrons containing a single b quark. The heavy quark is simulated using an $O(1/M)$ NRQCD action and the light quark using the $O(a)$ tadpole-improved clover action on gauge configurations containing two degenerate flavours of sea quarks at $\beta^{n_f=2}=5.6$ provided by the HEMCGC collaboration. We present detailed results for the lower lying $S$ and $P$ wave $B$ meson states and the $\Lambda_b$ baryon. We find broad agreement with experiment. In addition, we present results for the pseudoscalar and, for the first time, the vector decay constants fully consistent to $O(\alpha/M): f_B = 186(5)(stat)(19)(pert)(9)(disc)(13)(NRQCD)(+50)(a^{-1})MeV, f_B^* = 181(6) (stat)(18)(pert)(9)(disc)(13)(NRQCD)(+55)(a^{-1})MeV$ and $f_{B_s}/f_B = 1.14(2)(stat)(-2)(\kappa_s)$. We present an investigation of sea quark effects in the $B$ spectrum and decay constants. We compare our results with those from similar quenched simulations at $\beta^{n_f=0}=6.0$. For the spectrum, the quenched results reproduce the experimental spectrum well and there is no significant difference between the quenched and $n_f=2$ results. For the decay constants, our results suggest that sea quark effects may be large. We find that $f_B$ increases by approximately 25% between $n_f=0$ and $n_f=2$.Comment: 49 pages, 16 figures, revtex, the discussion of systematic errors and the comparison of the pseudoscalar decay constant at nf=0 and nf=2 has been expande

Scaling of the B and D meson spectrum in lattice QCD

We give results for the $B$ and the $D$ meson spectrum using NRQCD on the lattice in the quenched approximation. The masses of radially and orbitally excited states are calculated as well as $S$-wave hyperfine and $P$-wave fine structure. Radially excited $P$-states are observed for the first time. Radial and orbital excitation energies match well to experiment, as does the strange-non-strange $S$-wave splitting. We compare the light and heavy quark mass dependence of various splittings to experiment. Our $B$-results cover a range in lattice spacings of more than a factor of two. Our $D$-results are from a single lattice spacing and we compare them to numbers in the literature from finer lattices using other methods. We see no significant dependence of physical results on the lattice spacing. PACS: 11.15.Ha 12.38.Gc 14.40.Lb 14.40.NdComment: 78 pages, 29 tables, 30 figures Revised version. Minor corrections to spelling and wordin

The Cosmic Microwave Background in an Inhomogeneous Universe - why void models of dark energy are only weakly constrained by the CMB

The dimming of Type Ia supernovae could be the result of Hubble-scale inhomogeneity in the matter and spatial curvature, rather than signaling the presence of a dark energy component. A key challenge for such models is to fit the detailed spectrum of the cosmic microwave background (CMB). We present a detailed discussion of the small-scale CMB in an inhomogeneous universe, focusing on spherically symmetric `void' models. We allow for the dynamical effects of radiation while analyzing the problem, in contrast to other work which inadvertently fine tunes its spatial profile. This is a surprisingly important effect and we reach substantially different conclusions. Models which are open at CMB distances fit the CMB power spectrum without fine tuning; these models also fit the supernovae and local Hubble rate data which favours a high expansion rate. Asymptotically flat models may fit the CMB, but require some extra assumptions. We argue that a full treatment of the radiation in these models is necessary if we are to understand the correct constraints from the CMB, as well as other observations which rely on it, such as spectral distortions of the black body spectrum, the kinematic Sunyaev-Zeldovich effect or the Baryon Acoustic Oscillations.Comment: 23 pages with 14 figures. v2 has considerably extended discussion and analysis, but the basic results are unchanged. v3 is the final versio

Cosmological constraints on the generalized holographic dark energy

We use the Markov ChainMonte Carlo method to investigate global constraints on the generalized holographic (GH) dark energy with flat and non-flat universe from the current observed data: the Union2 dataset of type supernovae Ia (SNIa), high-redshift Gamma-Ray Bursts (GRBs), the observational Hubble data (OHD), the cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and the cosmic microwave background (CMB) data. The most stringent constraints on the GH model parameter are obtained. In addition, it is found that the equation of state for this generalized holographic dark energy can cross over the phantom boundary wde =-1.Comment: 14 pages, 5 figures. arXiv admin note: significant text overlap with arXiv:1105.186