QCD Factorization for Spin-Dependent Cross Sections in DIS and Drell-Yan Processes at Low Transverse Momentum

Based on a recent work on the quantum chromodynamic (QCD) factorization for semi-inclusive deep-inelastic scattering (DIS), we present a set of factorization formulas for the spin-dependent DIS and Drell-Yan cross sections at low transverse momentum.Comment: 12 pages, two figures include

Nonlinear Simultaneous Equations for Individual-Tree Diameter Growth and Mortality Model of Natural Mongolian Oak Forests in Northeast China

A nonlinear equation system for individual tree diameter growth and mortality of natural Mongolian oak forests was developed based on 13,360 observations from 195 permanent sample plots in Northeast China. Weighted regression was used in a distance-independent diameter growth equation for dealing with heterocedasticity. Since diameter growth and mortality models have common predictors including the diameter at breast height (DBH), stand basal area (BA), basal-area-in-larger trees (BAL), and site index (SI), parameters were estimated using nonlinear three-stage least squares (N3SLS) and seemingly unrelated regression (SUR) which accounts for correlations of errors across models. The system equation provided better projection than individual fitting of the equation based on maximum likelihood estimation. Compared with the separate tree growth model, the simultaneous equations using N3SLS and SUR produced more efficient parameter estimation and smaller bias. Furthermore, N3SLS had more accurate projection. Overall, the simultaneous model will facilitate the growth and yield projection for better management of Mongolian oak forests in the region

Threshold Resummation for Higgs Production in Effective Field Theory

We present an effective field theory to resum the large double logarithms originated from soft-gluon radiations at small final-state hadron invariant masses in Higgs and vector boson (\gamma^*, $W$ and $Z$) production at hadron colliders. The approach is conceptually simple, indepaendent of details of an effective field theory formulation, and valid to all orders in sub-leading logarithms. As an example, we show the result of summing the next-to-next-to-next leading logarithms is identical to that of standard pQCD factorization method.Comment: A version to appear in Phys. Rev.

Price Convergence and Market Integration in China

Whether China has successfully transformed from a formally centrally-controlled economy to a market economy is an issue of immense interest and considerable debate. The current study complements the received literature by testing price movements in China using panel data of monthly price indexes across 36 major Chinese cities over a thirteen-year period. By so doing, it extends the early work by Fan and Wei (2006) and thereby adds to the literature in four main aspects. First, price index data provide a wider coverage of all goods traded in the market than a group of individual commodity prices. Thus, it has more relevant implications for monetary and other macroeconomic policies. Second, as Taylor (2001) notes, there are crucial differences of methodologies in the study of price convergence between individual commodity data and index data. Thus, the present study not only further examines market integration in China, but also provides a comparative study of price index movements in a major transitional economy with for example the study for the US by Cecchetti, Mark, and Sonora (2002). Third, a recently developed new nonlinear unit root test is applied in this paper, which is more relevant to our study than other traditional linear unit root tests. Fourth, we developed a new nonlinear half-life estimation procedure that is consistent with the concept of the linear counterpart. We find that not only price indexes do converge to the law of one price in China but also the half life of price index convergence is relatively quick (about 5 to 16 months in the linear cases, and 7 to 24 months in the nonlinear situation)