We consider variants of dimensional regularization, including the four-dimensional helicity scheme (FDH) and dimensional reduction (DRED), and present the gluon and quark form factors in the FDH scheme at next-to-next-to-leading order. We also discus
s the generalization of the infrared factorization formula to FDH and DRED. This allows us to extract the cusp anomalous dimension as well as the quark and gluon anomalous dimensions at next-to-next-to-leading order in the FDH and DRED scheme, using $overline{text{MS}}$ and $overline{text{DR}}$ renormalization. To obtain these results we also present the renormalization procedure in these schemes.
We present a calculation of O(alpha_s) contributions to the process of t-channel single-top production and decay, which include virtual and real corrections arising from interference of the production and decay subprocesses. The calculation is organi
zed as a simultaneous expansion of the matrix elements in the couplings alpha_{ew},alpha_s and the virtuality of the intermediate top quark, (p_t^2-m_t^2)/m_t^2 ~ Gamma_t/m_t, and extends earlier results beyond the narrow-width approximation.
We consider a different power counting in potential NRQCD by incorporating the static potential exactly in the leading order Hamiltonian. We compute the leading relativistic corrections to the inclusive electromagnetic decay ratios in this new scheme
. The effect of this new power counting is found to be large (even for top). We produce an updated value for the $eta_b$ decay to two photons. This scheme also brings consistency between the weak coupling computation and the experimental value of the charmonium decay ratio.
We present a method to compute off-shell effects for processes involving resonant particles at hadron colliders with the possibility to include realistic cuts on the decay products. The method is based on an effective theory approach to unstable part
icle production and, as an example, is applied to t-channel single top production at the LHC.
This article is a very basic introduction to supersymmetry. It introduces the two kinds of superfields needed for supersymmetric extensions of the Standard Model, the chiral superfield and the vector superfield, and discusses in detail how to constru
ct supersymmetric, gauge invariant Lagrangians. The main ideas on how to break supersymmetry spontaneously are also covered. The article is meant to provide a platform for further reading.
We present an analysis to determine the charm quark mass from non-relativistic sum rules, using a combined approach taking into account fixed-order and effective-theory calculations. Non-perturbative corrections as well as higher-order perturbative c
orrections are under control. For the PS mass we find m_{PS}(0.7 GeV) = 1.50pm 0.04 GeV, which translates into a MS-bar mass of m = 1.25pm 0.04 GeV.
We discuss how to apply regularization by dimensional reduction for computing hadronic cross sections at next-to-leading order. We analyze the infrared singularity structure, demonstrate that there are no problems with factorization, and show how to
use dimensional reduction in conjunction with standard parton distribution functions. We clarify that differe
We combine the fixed-order evaluation of the $bbar{b}$ sum rules with a non-relativistic effective-theory approach. The combined result for the $n$-th moment includes all terms suppressed with respect to the leading-order result by ${cal O}(alpha_s^3
)$ and ${cal O}((alpha_s sqrt{n})^l alpha_s^2)$, counting $alpha_s sqrt{n} sim 1$. When compared to experimental data, the moments thus obtained show a remarkable consistency and allow for an analysis in the whole range $1le nlesssim 16$.
We study the effect of the resummation of logarithms for tbar{t} production near threshold and inclusive electromagnetic decays of heavy quarkonium. This analysis is complete at next-to-next-to-leading order and includes the full resummation of logar
ithms at next-to-leading-logarithmic accuracy and some partial contributions at next-to-next-to-leading logarithmic accuracy. Compared with fixed-order computations at next-to-next-to-leading order the scale dependence and convergence of the perturbative series is greatly improved for both the position of the peak and the normalization of the total cross section. Nevertheless, we identify a possible source of large scale dependence in the result. At present we estimate the remaining theoretical uncertainty of the normalization of the total cross section to be of the order of 10% and for the position of the peak of the order of 100 MeV.
