Probing Contact Interactions at High Energy Lepton Colliders

Fermion compositeness and other new physics can be signalled by the presence of a strong four-fermion contact interaction. Here we present a study of $\ell\ell qq$ and $\ell\ell\ell'\ell'$ contact interactions using the reactions: $\ell^+ \ell^- \to \ell'^+\ell'^-,b\bar b, c\bar c$ at future $e^+e^-$ linear colliders with $\sqrt s=0.5-5$ TeV and $\mu^+\mu^-$ colliders with $\sqrt s=0.5,4$ TeV. We find that very large compositeness scales can be probed at these machines and that the use of polarized beams can unravel their underlying helicity structure.Comment: 12 pg, to appear in the {\it Proceedings of the 1996 DPF/DPB Summer Study on New Directions for High Energy Physics - Snowmass96}, Snowmass, CO, 25 June - 12 July, 199

A probe of the Radion-Higgs mixing in the Randall-Sundrum model at e^+ e^- colliders

In the Randall-Sundrum model, the radion-Higgs mixing is weakly suppressed by the effective electroweak scale. A novel feature of the existence of gravity-scalar mixing would be a sizable three-point vertex among the KK graviton, Higgs and radion. We study this vertex in the process e^+ e^- -> h phi, which is allowed only with a non-zero radion-Higgs mixing. It is shown that the angular distribution is a unique characteristic of the exchange of massive spin-2 gravitons, and the total cross section at the future e^+ e^- collider is big enough to cover a large portion of the parameter space where the LEP/LEP II data cannot constrain.Comment: 14pages, RevTeX, 5 figure

A Reappraisal of the Border Effect on Relative Price Volatility

Engel and Rogers (1996) find that crossing the US-Canada border can considerably raise relative price volatility and that exchange rate fluctuations explain about one-third of the volatility increase. In re-evaluating the border effect, this study shows that cross-country heterogeneity in price volatility can lead to significant bias in measuring the border effect unless proper adjustment is made to correct it. The analysis explores the implication of symmetric sampling for border effect estimation. Moreover, using a direct decomposition method, two conditions governing the strength of the border effect are identified. In particular, the more dissimilar the price shocks are across countries, the greater the border effect will be. Decomposition estimates also suggest that exchange rate fluctuations actually account for a large majority of the border effect.price volatility, exchange rate volatility, national border, distance, dissimilar shocks

Nominal Exchange Rate Flexibility and Real Exchange Rate Adjustment: Evidence from Dual Exchange Rates in Developing Countries

This study investigates whether exchange rate flexibility aids real exchange rate adjustment based on intra-period data on dual exchange rates from developing countries. Specifically, it analyzes whether the flexible parallel market rate produces faster or slower real exchange rate adjustment than the much less flexible official rate does. Half-life estimates of adjustment speeds are obtained using fractional time series analysis. We find no systematic evidence that greater exchange rate flexibility tends to produce faster or slower real exchange rate adjustment, albeit there is substantial heterogeneity in speed estimates across countries. With officially pegged exchange rates, developing countries often use parallel exchange markets as a back-door channel to facilitate real exchange rate adjustment, but the empirical evidence suggests that these parallel markets in most cases fail to help promote real rate adjustment.real exchange rate, fractional time series, half life