Isospin violation in low-energy charged pion-kaon scattering

We evaluate the isospin breaking corrections to the scattering amplitude \pi^- K^+ -> \pi^- K^+ at threshold in the framework of chiral perturbation theory. This channel is of particular interest for the strong 2S-2P energy level shift in pion-kaon bound states. While a prediction of this level shift is hampered by a large uncertainty in the isoscalar scattering length, we find only a moderate uncertainty of about 3% in the electromagnetic corrections which are relevant for the extraction of the scattering lengths from experimentComment: 9 pp, 2 fig

Baryon form factors in chiral perturbation theory

We analyze the electromagnetic form factors of the ground state baryon octet to fourth order in relativistic baryon chiral perturbation theory. Predictions for the \Sigma^- charge radius and the \Lambda-\Sigma^0 transition moment are found to be in excellent agreement with the available experimental information. Furthermore, the convergence behavior of the hyperon charge radii is shown to be more than satisfactory.Comment: 22 pp, LaTeX2e, FZJ-IKP(TH)-2000-2

Strategies for Improved Servicing of the Customers: Case of Ghaziabad Goods Shed of the Indian Railways

The Ghaziabad (GZB) goods shed was one of the top rail goods handling points in the National Capital Region (NCR). The growth was expected to be robust in the forthcoming years, since GZB and Noida were high growth districts in the Uttar Pradesh part of the NCR. GZB goods shed was one of the fifty high traffic sheds identified for improvement, as part of the Indian Railways (IRs) Mission 900 mt loading. The paper provides a comprehensive description of GZB goods shed, including facilities, traffic flow, customer interface, processes, etc. In this context, the paper raises questions regarding (i) main concerns in GZB goods shed as viewed (a) by customers and (b) from IRs perspective, (ii) analytical support for customer service improvement provided by demurrage (wharfage) data, (iii) operational, process and infrastructure improvements at GZB, (iv) long term improvements, and (v) need for perspective changes.

The effects of spatially distributed ionisation sources on the temperature structure of HII region

Spatially resolved studies of star forming regions show that the assumption of spherical geometry is not realistic in most cases, with a major complication posed by the gas being ionised by multiple non-centrally located stars or star clusters. We try to isolate the effects of multiple non-centrally located stars on the temperature and ionisation structure of HII regions, via the construction of 3D photoionisation models using the 3D Monte Carlo photoionisation code MOCASSIN. We find that the true temperature fluctuations due to the stellar distribution (as opposed to the large-scale temperature gradients due to other gas properties) are small in all cases and not a significant cause of error in metallicity studies. Strong emission lines from HII regions are often used to study the metallicity of star-forming regions. We compare integrated emission line spectra from our models and quantify any systematic errors caused by the simplifying assumption of a single, central location for all ionising sources. We find that the dependence of the metallicity indicators on the ionisation parameter causes a clear bias, due to the fact that models with a fully distributed configuration of stars always display lower ionisation parameters than their fully concentrated counterparts. The errors found imply that the geometrical distribution of ionisation sources may partly account for the large scatter in metallicities derived using model-calibrated empirical methods.Comment: 13 pages, 6 figures, Accepted by MNRA

Isospin violation in low-energy pion-nucleon scattering revisited

We calculate isospin breaking in pion-nucleon scattering in the threshold region in the framework of covariant baryon chiral perturbation theory. All effects due to quark mass differences as well as real and virtual photons are consistently included. As an application, we discuss the energy dependence of the triangle relation that connects elastic scattering on the proton pi+- p --> pi+- p with the charge exchange reaction pi- p --> pi0 n.Comment: 82 pages, 22 figures, version published in Nucl. Phys.

Analysis of the pion-kaon sigma-term and related topics

We calculate the one-loop contributions to the difference \Delta_{\pi K} between the isoscalar on-shell pion-kaon scattering amplitude at the Cheng-Dashen point and the scalar form factor \Gamma_K (2M_\pi^2) in the framework of three flavor chiral perturbation theory. These corrections turn out to be small. This is further sharpened by treating the kaons as heavy fields (two flavor chiral perturbation theory). We also analyze the two-loop corrections to the kaon scalar form factor based on a dispersive technique. We find that these corrections are smaller than in the comparable case of the scalar form factor of the pion. This is related to the weaker final state interactions in the pion-kaon channel.Comment: 25 pp, 3 fig

Ballistic reflection at a side-gate in a superconductor-semiconductor-superconductor structure

We have fabricated a sub-micron-sized structure consisting of an InAs-based 2DEG, two narrow Nb leads and a gate, where the indirect ballistic transport between the non-oppositely superconducting contacts can be controlled by the voltage applied to the gate. This new kind of tuneable junction can be used for applications and allows several fundamental questions related to the transport mechanism to be studied. First results of experiments carried out in this respect are presented.Comment: 6 pages, 4 eps-figure

Improved dispersive analysis of the scalar form factor of the nucleon

We present a coupled system of integral equations for the pi pi --> Nbar N and Kbar K --> Nbar N S-waves derived from Roy-Steiner equations for pion-nucleon scattering. We discuss the solution of the corresponding two-channel Muskhelishvili-Omnes problem and apply the results to a dispersive analysis of the scalar form factor of the nucleon fully including Kbar K intermediate states. In particular, we determine the corrections Delta_sigma and Delta_D, which are needed for the extraction of the pion-nucleon sigma term from pi N scattering, and show that the difference Delta_D - Delta_sigma=(-1.8 +/- 0.2) MeV is insensitive to the input pi N parameters.Comment: 6 pages, 3 figures, Proceedings for the 7th International Workshop on Chiral Dynamics, Newport News, Virginia, USA, August 6-10, 201