Octet baryon magnetic moments from QCD sum rules

A comprehensive study is made for the magnetic moments of octet baryons in the method of QCD sum rules. A complete set of QCD sum rules is derived using the external field method and generalized interpolating fields. For each member, three sum rules are constructed from three independent tensor structures. They are analyzed in conjunction with the corresponding mass sum rules. The performance of each of the sum rules is examined using the criteria of OPE convergence and ground-state dominance, along with the role of the transitions in intermediate states. Individual contributions from the u, d and s quarks are isolated and their implications in the underlying dynamics are explored. Valid sum rules are identified and their predictions are obtained. The results are compared with experiment and previous calculations.Comment: 21 pages, 11 figures, 6 figures; added a reference, minor change in tex

Methods for Measuring New-Physics Parameters in B Decays

Recently, it was argued that new-physics (NP) effects in B decays can be approximately parametrized in terms of a few quantities. As a result, CP violation in the $B$ system allows one not only to detect the presence of new physics (NP), but also to measure its parameters. This will allow a partial identification of the NP, before its production at high-energy colliders. In this paper, we examine three methods for measuring NP parameters. The first uses a technique involving both \btos and \btod penguin B decays. Depending on which pair of decays is used, the theoretical error is in the range 5--15%. The second involves a comparison of $B\to \pi K$ and $B\to\pi\pi$ decays. Although the theoretical error is large (\gsim 25%), the method can be performed now, with presently-available data. The third is via a time-dependent angular analysis of \bvv decays. In this case, there is no theoretical error, but the technique is experimentally challenging, and the method applies only to those NP models whose weak phase is universal to all NP operators. A reliable identification of the NP will involve the measurement of the NP parameters in many different ways, and with as many B decay modes as possible, so that it will be important to use all of these methods.Comment: 33 pages, latex, no figures. Appendix added. Analysis and conclusions unchange

Tau contamination in the platinum channel at neutrino factories

The platinum channel (\nu_e or anti-\nu_e appearance) has been proposed at neutrino factories as an additional channel that could help in lifting degeneracies and improving sensitivities to neutrino oscillation parameters, viz., \theta_{13}, \delta_{CP}, mass hierarchy, deviation of \theta_{23} from maximality and its octant. This channel corresponds to \nu_\mu -> \nu_e (or the corresponding anti-particle) oscillations of the initial neutrino flux, with the subsequent detection of (positrons) electrons from charged current interactions of the (anti-) \nu_e in the detector. For small values of \theta_{13}, the dominant \nu_\mu \to \nu_\tau (or corresponding anti-particle) oscillation results in this signal being swamped by electrons arising from the leptonic decay of taus produced in charge-current interactions of \nu_\tau (anti-\nu_\tau) with the detector. We examine for the first time the role of this tau contamination to the electron events sample and find that it plays a significant role in the platinum channel compared to other channels, not only at high energy neutrino factories but surprisingly even at low energy neutrino factories. Even when the platinum channel is considered in combination with other channels such as the golden (muon appearance) or muon disappearance channel, the tau contamination results in a loss in precision of the measured parameters.Comment: 13 pages latex file with 10 eps figure file

Collective behavior of stock price movements in an emerging market

To investigate the universality of the structure of interactions in different markets, we analyze the cross-correlation matrix C of stock price fluctuations in the National Stock Exchange (NSE) of India. We find that this emerging market exhibits strong correlations in the movement of stock prices compared to developed markets, such as the New York Stock Exchange (NYSE). This is shown to be due to the dominant influence of a common market mode on the stock prices. By comparison, interactions between related stocks, e.g., those belonging to the same business sector, are much weaker. This lack of distinct sector identity in emerging markets is explicitly shown by reconstructing the network of mutually interacting stocks. Spectral analysis of C for NSE reveals that, the few largest eigenvalues deviate from the bulk of the spectrum predicted by random matrix theory, but they are far fewer in number compared to, e.g., NYSE. We show this to be due to the relative weakness of intra-sector interactions between stocks, compared to the market mode, by modeling stock price dynamics with a two-factor model. Our results suggest that the emergence of an internal structure comprising multiple groups of strongly coupled components is a signature of market development.Comment: 10 pages, 10 figure

Response to sub-threshold stimulus is enhanced by spatially heterogeneous activity

Sub-threshold stimuli cannot initiate excitations in active media, but surprisingly as we show in this paper, they can alter the time-evolution of spatially heterogeneous activity by modifying the recovery dynamics. This results in significant reduction of waveback velocity which may lead to spatial coherence, terminating all activity in the medium including spatiotemporal chaos. We analytically derive model-independent conditions for which such behavior can be observed.Comment: 5 pages, 5 figure

On the superposition principle in interference experiments

The superposition principle is usually incorrectly applied in interference experiments. This has recently been investigated through numerics based on Finite Difference Time Domain (FDTD) methods as well as the Feynman path integral formalism. In the current work, we have derived an analytic formula for the Sorkin parameter which can be used to determine the deviation from the application of the principle. We have found excellent agreement between the analytic distribution and those that have been earlier estimated by numerical integration as well as resource intensive FDTD simulations. The analytic handle would be useful for comparing theory with future experiments. It is applicable both to physics based on classical wave equations as well as the non-relativistic Schrodinger equation.Comment: 8 pages, 4 figures, To appear in Scientific Reports (Nature

Core-tube morphology of multiwall carbon nanotubes

The present paper investigates the cross-sectional morphology of Multiwalled Carbon Nanotubes (MWNTs) restrained radially and circumferentially by an infinite surrounding elastic medium, subjected to uniform external hydrostatic pressure. In this study, a two-dimensional plane strain model is developed, assuming no variation of load and deformation along the tube axis. We find some characteristic cross-sectional shapes from the elastic buckling analysis. The effect of the surrounded elastic medium on the cross-sectional shape which occurs due to pressure buckling is focused on by the comparison with the shape for no elastic medium case in our discussion. It is suggested that in no embedded elastic medium cases, the cross-sectional shapes of inner tubes maintain circle or oval; on the other hand, an embedded medium may cause inner tube corrugation modes especially when the number of shells for MWNTs is small.Comment: 7 figures, 2 figure