Regularization for effective field theory with two heavy particles

A regularization for effective field theory with two propagating heavy particles is constructed. This regularization preserves the low-energy analytic structure, implements a low-energy power counting for the one-loop diagrams, and preserves symmetries respected by dimensional regularization.Comment: 12 pages, 4 figures. Some typos have been corrected, a sentence has been moved, and two formulas have been further simplifie

pi-N charge exchange and pi(+)-pi(0) scattering at low energies

pi-N and pi-pi interactions near threshold are uniquely sensitive to the chiral symmetry breaking part of the strong interaction. The pi-N sigma-term value with its implications for nucleon quark structure and the recent controversy concerning the size of the scalar quark condensate have renewed the experimental interest in these two fundamental systems. We report new differential cross sections for the reaction $pi^-p \to \pi^0n$ at 27.5 MeV pion incident kinetic energy, measured between $\theta_{CM} = 0^\circ$ and $55^\circ$. Our results are in excellent agreement with the existing comprehensive pi-N phase shift analysis. We also report on a Chew-Low analysis of exclusive $\pi^+ p \to \pi^+\pi^0p$ data at 260 MeV pion incident energy.Comment: Talk given by D. Pocanic at QULEN97, Osaka, 20-23 May 1997; 4 pages, 2 PostScript figures, writen in LaTeX 2e, uses packages "epsfig" and "espcrc1

Studies and Design of the ECAL (CMS) Cooling System

The Electromagnetic CALorimeter (ECAL) sub-detector for the CMS experiment has to achieve very tight requirements in terms of temperature stability. The CV group is now involved in the design of a cooling system for ECAL. The status and the content of the work which has been done will be explained. The theoretical studies which helped to understand the ECAL thermal behaviour and the efficiency of the hydraulic network in charge of the cooling will first be briefly presented. Moreover, it will be shown how these studies helped to improve the cooling design inside ECAL. A proposal for an external cooling system of ECAL will be presented as well. Finally, experimental thermal tests, which are planned for April 2000 on a prototype corresponding to a part of ECAL, will be described. These tests aim to check the technical solutions which can be applied in the context of the real ECAL detector

Target Cooling for the TOF Experiment

In the TOF experiment, a high-energy proton beam is sent on a lead target, which releases an important amount of heat inside. In order to avoid that the target temperature rises over the lead melting point, a cooling system was designed. Starting from the heat distribution generated inside the target by the proton beam, steady and unsteady simulations of the target thermal behavior were carried out. These simulations were performed with different ways of cooling and in the various beam configurations foreseen for the experiment. It will be explained how these simulations helped to design a suitable water cooling system for the target. The hydraulic circuit providing the cool water will be briefly described as well

Chiral Corrections to Lattice Calculations of Charge Radii

Logarithmic divergences in pion and proton charge radii associated with chiral loops are investigated to assess systematic uncertainties in current lattice determinations of charge radii. The chiral corrections offer a possible solution to the long standing problem of why present lattice calculations yield proton and pion radii which are similar in size.Comment: PostScript file only. Ten pages. Figures included. U. of MD Preprint #92-19

Isospin Violation in Chiral Perturbation Theory and the Decays \eta \ra \pi \ell \nu and \tau \ra \eta \pi \nu

I discuss isospin breaking effects within the standard model. Chiral perturbation theory presents the appropriate theoretical framework for such an investigation in the low--energy range. Recent results on the electromagnetic contributions to the masses of the pseudoscalar mesons and the $K_{\ell 3}$ amplitudes are reported. Using the one--loop formulae for the $\eta_{\ell 3}$ form factors, rather precise predictions for the decay rates of $\eta \rightarrow \pi \ell \nu$ can be obtained. Finally, I present an estimate of the \tau \ra \eta \pi \nu branching ratio derived from the dominant meson resonance contributions to this decay.Comment: 10 pages, latex, one figure available upon reques

Pion mass dependence of the Kl3K_{l3} semileptonic scalar form factor within finite volume

We calculate the scalar semileptonic kaon decay in finite volume at the momentum transfer $t_{m} = (m_{K} - m_{\pi})^2$, using chiral perturbation theory. At first we obtain the hadronic matrix element to be calculated in finite volume. We then evaluate the finite size effects for two volumes with $L = 1.83 fm$ and $L= 2.73 fm$ and find that the difference between the finite volume corrections of the two volumes are larger than the difference as quoted in \cite{Boyle2007a}. It appears then that the pion masses used for the scalar form factor in ChPT are large which result in large finite volume corrections. If appropriate values for pion mass are used, we believe that the finite size effects estimated in this paper can be useful for Lattice data to extrapolate at large lattice size.Comment: 19 pages, 5 figures, accepted for publication in EPJ

Structural features of laser ablation particulate from Si target, as revealed by focused ion beam technology

Heterogeneity in laser-induced particle structures was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of individual particles micro-machined using focused ion beam (FIB). The primary particle size distribution spanned over three orders of magnitude, i.e., in the range 10nm-10μm with few larger secondary objects. The particulate larger than 0.5μm often resulted from particle-particle aggregation, mostly upon a spherical core, seldom in chain-like structures. The core of these fractal aggregates was found to be polycrystalline. The heterogeneity of the particles with respect to structure and chemistry is surely of importance for elemental analysis using laser ablation as sample introduction techniqu

Nonparametric maximum likelihood estimation of the structural mean of a sample of curves

A random sample of curves can be usually thought of as noisy realisations of a compound stochastic process X(t) = Z{W(t)}, where Z(t) produces random amplitude variation and W(t) produces random dynamic or phase variation. In most applications it is more important to estimate the so-called structural mean µ(t) = E{Z(t)} than the crosssectional mean E{X(t)}, but this estimation problem is difficult because the process Z(t) is not directly observable. In this paper we propose a nonparametric maximum likelihood estimator of µ(t). This estimator is shown to be {surd}n-consistent and asymptotically normal under the assumed model and robust to model misspecification. Simulations and a realdata example show that the proposed estimator is competitive with landmark registration, often considered the benchmark, and has the advantage of avoiding time-consuming and often infeasible individual landmark identificatio

The size of flavor changing effects induced by the symmetry breaking sector

It has recently been shown that strong interactions underlying electroweak symmetry breaking will induce four-fermion amplitudes proportional to m_t^2, which in turn will influence a variety of flavor changing processes. We argue that the size of these effects are likely to be far below the current experimental bounds.Comment: 5 pages, LaTeX, 1 figur