Body mass distributions along successional gradients in epigeic carabid beetle fauna (Coleoptera: Carabidae)

Background and purpose: Body mass distributions may be related to the stage of succession of a habitat and provide with information for assessing successional processes. Therefore, body mass distributions of carabid assemblages were studied in three research areas, which were post-industrial areas near the city of Bełchatów (Central Poland) planted with different tree and shrub species, moist and wet forest stands in the Puszcza Knyszyńska forest (Northeastern Poland), and beech stands in the Ruhr valley (Western Germany) in order to analyze the changes in body mass distributions within single assemblages along successional gradients.   Materials and Methods: For each carabid assemblage, the mean individual biomass (MIB) as well as MIB standard deviation (SD) and coefficient of variation (CV) were calculated. SD and CV were plotted against the age of study sites and MIB values, respectively. Analyses of Covariance (ANCOVA) were carried out with SD and CV as dependent variables and the age of study sites and MIB as covariates.   Results: SD was low at young stages of succession, but increased rapidly and plateaued at advanced stages in beech but not in wet forest stands. Accordingly, CV was low at very young stages of succession, showing a rapid increase and subsequent decrease in the beech stands, whereas in the wet stands it stayed on a constant level. ANCOVA revealed significant differences in SD and CV between the research areas and significant changes with age or MIB, but, with the exception of CV as dependent variable and MIB as covariate, interactions were also significant.   Conclusions: The results of the study suggest that data on body mass distributions within single carabid assemblages may be useful in the assessment and comparison of successional stages and processes between different habitat types.</p

On the Scale Uncertainties in the B→XsγB \to X_s \gamma Decay

We analyze the theoretical uncertainties in $Br(B\to X_s\gamma)$ due to the choice of the high energy matching scale \mu_W=\ord(\mw) and the scale $\mu_t$ at which the running top quark mass is defined: \mtb(\mu_t). To this end we have repeated the calculation of the initial conditions confirming the final results of Adel and Yao and Greub and Hurth and generalizing them to include the dependences on $\mu_t$ and $\mu_W$ with $\mu_t\not=\mu_W$. In the leading order the $\mu_W$ and $\mu_t$ uncertainties in $Br(B\to X_s\gamma)$ turn out to be $\pm 13$ and $\pm 3$ respectively. We show analytically how these uncertainties are reduced after including next-to-leading QCD corrections. They amount to $\pm 1.1$ and $\pm 0.4$ respectively. Reanalyzing the uncertainties due to the scale \mu_b=\ord(m_b) we find that after the inclusion of NLO effects they amount to $\pm 4.3$ which is a factor 2/3 smaller than claimed in the literature. Including the uncertainties due to input parameters as well as the non-perturbative $1/m_b^2$ and $1/m_c^2$ corrections we find $Br(B{\to}X_s \gamma) = (3.60 \pm 0.33) \times 10^{-4}$ where the error is dominated by uncertainties in the input parameters. This should be compared with $(3.28 \pm 0.33) \times 10^{-4}$ found by Chetyrkin et al. where the error is shared evenly between the scale and parametric uncertainties.Comment: 11 pages, Latex. The paper is updated by incorporating recently modified results of the literature that were used for the numerical evaluation of eq. (17). A term originally missing in eq. (22) is adde

Electroweak effects in the B0−Bˉ0B^0-{\bar B}^0 mixing

We compute analytically the complete electroweak two-loop corrections to the $B^0-{\bar B}^0$ mixing. These corrections fix the normalization of the electroweak coupling employed in the extraction of $|V_{td}|$ and reduce the theoretical uncertainty due to higher order electroweak effects from several percent to a few parts in a thousand. If the LO result is expressed in terms of $G_\mu$ or of the $\bar{MS}$ coupling $\hat{g}(M_Z)$, the two-loop corrections are $O(1$, the exact value depending on the mass of the Higgs boson. We discuss in detail the renormalization procedure and the scheme and scale dependence, and provide practical formulas for the numerical implementation of our results. We also consider the heavy top mass expansion and show that in the case at hand it converges very slowly.Comment: LaTeX, 29 pages, 6 postscript figures include

Next-To-Leading-Order Matching for the Magnetic Photon-Penguin Operator in the B→XsγB \to X_s \gamma Decay

The initial condition at the matching scale $\mu_W = O(M_W)$ for the Wilson coefficient of the magnetic photon-penguin operator in the decay $B\to X_s \gamma$ is calculated in the next-to-leading-order approximation. The technical details of the necessary two-loop calculation in the full theory are described and the matching with the corresponding result in the effective theory is discussed in detail. Our outcome for the initial condition confirms the final results of Adel and Yao and Greub and Hurth. We show that --- contrary to the claims in the second of these papers --- the matching procedure can be properly performed for infrared divergent amplitudes, i.e. independently of contributions from gluon bremsstrahlung.Comment: 24 pages, Latex, 3 Figure