Quark energy loss and shadowing in nuclear Drell-Yan process

The energy loss effect in nuclear matter is another nuclear effect apart from the nuclear effects on the parton distribution as in deep inelastic scattering process. The quark energy loss can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of three kinds of quark energy loss parameterizations given in literature and the nuclear parton distribution extracted only with lepton-nucleus deep inelastic scattering experimental data, measured Drell-Yan production cross sections are analyzed for 800GeV proton incident on a variety of nuclear targets from FNAL E866. It is shown that our results with considering the energy loss effect are much different from these of the FNAL E866 who analysis the experimental data with the nuclear parton distribution functions obtained by using the deep inelastic lA collisions and pA nuclear Drell-Yan data . Considering the existence of energy loss effect in Drell-Yan lepton pairs production,we suggest that the extraction of nuclear parton distribution functions should not include Drell-Yan experimental data.Comment: 12 page

Resonant and nonresonant D+ -> K- pi+ l+ nu(l) semileptonic decays

We analyse the semileptonic decay D+ -> K- pi+ l+ nu(l) using an effective Lagrangian developed previously to describe the decays D -> P l nu(l) and D -> V l nu(l). Light vector mesons are included in the model which combines the heavy quark effective Lagrangian and chiral perturbation theory approach. The nonresonant and resonant contributions are compared. With no new parameters the model correctly reproduces the measured ratio Gamma(nres)/Gamma(nres + res). We also present useful nonresonant decay distributions. Finally, a similar model, but with a modified current which satisfies the soft pion theorems at the expense of introducing another parameter, is analyzed and the results of the models are compared.Comment: 17 pages, 3 Postscript figures, standard Latex, extended revision, title, abstract and text (especially Sec. IV) changed, results unchange

Investigation of a hydraulic impact: a technology in rock breaking

The finite element method and dimensional analysis have been applied in the present paper to study a hydraulic impact, which is utilized in a non-explosive rock breaking technology in mining industry. The impact process of a high speed piston on liquid water, previously introduced in a borehole drilled in rock, is numerically simulated. The research is focused on the influences of all the parameters involved in the technology on the largest principal stress in the rock, which is considered as one of the key factors to break the rock. Our detailed parametric investigation reveals that the variation of the isotropic rock material properties, especially its density, has no significant influence on the largest principal stress. The influences of the depth of the hole and the depth of the water column are also very small. On the other hand, increasing the initial kinetic energy of the piston can dramatically increase the largest principal stress and the best way to increase the initial kinetic energy of the piston is to increase its initial velocity. Results from the current dimensional analysis can be applied to optimize this non-explosive rock breaking technology

Predicting chronic copper and nickel reproductive toxicity to Daphnia pulex-pulicaria from whole-animal metabolic profiles

The emergence of omics approaches in environmental research has enhanced our understanding of the mechanisms underlying toxicity; however, extrapolation from molecular effects to whole-organism and population level outcomes remains a considerable challenge. Using environmentally relevant, sublethal, concentrations of two metals (Cu and Ni), both singly and in binary mixtures, we integrated data from traditional chronic, partial life-cycle toxicity testing and metabolomics to generate a statistical model that was predictive of reproductive impairment in a Daphnia pulex-pulicaria hybrid that was isolated from an historically metal-stressed lake. Furthermore, we determined that the metabolic profiles of organisms exposed in a separate acute assay were also predictive of impaired reproduction following metal exposure. Thus we were able to directly associate molecular profiles to a key population response - reproduction, a key step towards improving environmental risk assessment and management

Quantum Hall activation gaps in bilayer graphene

We have measured the quantum Hall activation gaps in bilayer graphene at filling factors $\nu=\pm4$ and $\nu=\pm8$ in high magnetic fields up to 30 T. We find that energy levels can be described by a 4-band relativistic hyperbolic dispersion. The Landau level width is found to contain a field independent background due to an intrinsic level broadening and a component which increases linearly with magnetic field.Comment: 4 pages, accepted version (just removed a few typos), will appear as Fast Track Communication in Solid State Commu

Impurity (Fe, Cl, and P)-induced grain boundary and secondary phases in commercially pure titanium (CP-Ti)

A detailed transmission electron microscopy (TEM) study has been made of the microstructures of two as-sintered CP-Ti materials. We show that iron content at the impurity level of 1280 ppm, less than the limit (2000 ppm) for CP-Ti ASTM Grade 1, is sufficient to lead to the formation of a grain boundary (GB) β-Ti phase in the as-sintered microstructure due to segregation. The Fe-stabilized GB β-Ti phase contains ∼7 at. pct Fe and ∼1.5 at. pct Cl. In addition, nano-precipitates of ω-Ti exist in the Fe-stabilized GB β-Ti phase. A phosphorus (P)-enriched Ti-P-based phase was also identified, which has a tetragonal crystal structure with lattice parameters of (a = b = 8.0 ± 0.2 Å and c = 2.7 ± 0.2 Å) and is new to the existing database for Ti-P-enriched phases. As-sintered CP-Ti materials are thus not necessarily a single α-Ti phase material. These impurity-induced phases may exert potential impacts on the properties of sintered CP-Ti

Convergence of the stochastic Euler scheme for locally Lipschitz coefficients

Stochastic differential equations are often simulated with the Monte Carlo Euler method. Convergence of this method is well understood in the case of globally Lipschitz continuous coefficients of the stochastic differential equation. The important case of superlinearly growing coefficients, however, has remained an open question. The main difficulty is that numerically weak convergence fails to hold in many cases of superlinearly growing coefficients. In this paper we overcome this difficulty and establish convergence of the Monte Carlo Euler method for a large class of one-dimensional stochastic differential equations whose drift functions have at most polynomial growth.Comment: Published at http://www.springerlink.com/content/g076w80730811vv3 in the Foundations of Computational Mathematics 201

Dipolar origin of the gas-liquid coexistence of the hard-core 1:1 electrolyte model

We present a systematic study of the effect of the ion pairing on the gas-liquid phase transition of hard-core 1:1 electrolyte models. We study a class of dipolar dimer models that depend on a parameter R_c, the maximum separation between the ions that compose the dimer. This parameter can vary from sigma_{+/-} that corresponds to the tightly tethered dipolar dimer model, to R_c --> infinity, that corresponds to the Stillinger-Lovett description of the free ion system. The coexistence curve and critical point parameters are obtained as a function of R_c by grand canonical Monte Carlo techniques. Our results show that this dependence is smooth but non-monotonic and converges asymptotically towards the free ion case for relatively small values of R_c. This fact allows us to describe the gas-liquid transition in the free ion model as a transition between two dimerized fluid phases. The role of the unpaired ions can be considered as a perturbation of this picture.Comment: 16 pages, 13 figures, submitted to Physical Review

Nonresonant Three-body Decays of D and B Mesons

Nonresonant three-body decays of D and B mesons are studied. It is pointed out that if heavy meson chiral perturbation theory (HMChPT) is applied to the heavy-light strong and weak vertices and assumed to be valid over the whole kinematic region, then the predicted decay rates for nonresonant charmless 3-body B decays will be too large and especially B^- --> pi^- K^+ K^- greatly exceeds the current experimental limit. This can be understood as chiral symmetry has been applied there twice beyond its region of validity. If HMChPT is applied only to the strong vertex and the weak transition is accounted for by the form factors, the dominant B^* pole contribution to the tree-dominated direct three-body B decays will become small and the branching ratio will be of order 10^{-6}. The decay modes B^- --> (K^- h^+ h^-)_{NR} and bar{B}^0 --> (bar{K}^0 h^+h^-)_{NR} for h = pi, K are penguin dominated. We apply HMChPT in two different cases to study the direct 3-body D decays and compare the results with experiment. Theoretical uncertainties are discussed.Comment: 24 pages, 2 figures. New experimental results of direct 3-body D decays as Reported at ICHEP2002 are included. To appear in Phys. Re