Two-loop corrections to Higgs boson production

In this paper we present the complete two-loop vertex corrections to scalar and pseudo-scalar Higgs boson production for general colour factors for the gauge group ${\rm SU(N)}$ in the limit where the top quark mass gets infinite. We derive a general formula for the vertex correction which holds for conserved and non conserved operators. For the conserved operator we take the electromagnetic vertex correction as an example whereas for the non conserved operators we take the two vertex corrections above. Our observations for the structure of the pole terms $1/\epsilon^4$, $1/\epsilon^3$ and $1/\epsilon^2$ in two loop order are the same as made earlier in the literature for electromagnetism. However we also elucidate the origin of the second order single pole term which is equal to the second order singular part of the anomalous dimension plus a universal function which is the same for the quark and the gluon. [3mm]Comment: 27 pages LaTeX.We correct some misprints. Moreover we have discovered that the second order single pole term is equal to the singular part of the second order anomalous dimension plus a universal function which is the same for the quark and the gluon. This holds for vertex corrections as well as for scattering amplitude

QCD and power corrections to sum rules in deep-inelastic lepton-nucleon scattering

In this paper we study QCD and power corrections to sum rules which show up in deep inelastic lepton-hadron scattering. Furthermore we will make a distinction between fundamental sum rules which can be derived from quantum field theory and those which are of a phenomenological origin. Using current algebra techniques the fundamental sum rules can be expressed into expectation values of (partially) conserved (axial-) vector currents sandwiched between hadronic states. These expectation values yield the quantum numbers of the corresponding hadron which are determined by the underlying flavour group $SU(n)_F$. In this case one can show that there exist an intimate relation between the appearance of power and QCD corrections. The above features do not hold for phenomenological sum rules, hereafter called non-fundamental. They have no foundation in quantum field theory and they mostly depend on certain assumptions made for the structure functions like superconvergence relations or the parton model. Therefore only the fundamental sum rules provide us with a stringent test of QCD

Higgs Production at NNLO

We describe the calculation of inclusive Higgs boson production at hadronic colliders at next-to-next-to-leading order (NNLO) in perturbative quantum chromodynamics. We have used the technique developed in reference [4]. Our results agree with those published earlier in the literature.Comment: Talk given at PASCOS'03, TIFR, Mumbai, LaTeX, 5 page

Relations among polarized and unpolarized splitting functions beyond leading order

The role of various symmetries in the evaluation of splitting functions and coefficient functions is discussed. The scale invariance in hard processes is known to be a guiding tool to understand the dynamics. We discuss the constraints on splitting functions coming from various symmetries such as scale, conformal and supersymmetry. We also discuss the Drell-Levy-Yan relation among splitting and coefficient functions in various schemes. The relations coming from conformal symmetry are also presented

Differential Cross Sections for Higgs Production

We review recent theoretical progress in evaluating higher order QCD corrections to Higgs boson differential distributions at hadron-hadron colliders

Pressure-induced structural transitions in MgH2{_2}

The stability of MgH$_2$ has been studied up to 20~GPa using density-functional total-energy calculations. At ambient pressure $\alpha$-MgH${_2}$ takes a TiO$_2$-rutile-type structure. $\alpha$-MgH$_2$ is predicted to transform into $\gamma$-MgH${_2}$ at 0.39~GPa. The calculated structural data for $\alpha$- and $\gamma$-MgH${_2}$ are in very good agreement with experimental values. At equilibrium the energy difference between these modifications is very small, and as a result both phases coexist in a certain volume and pressure field. Above 3.84~GPa $\gamma$-MgH${_2}$ transforms into $\beta$-MgH${_2}$; consistent with experimental findings. Two further transformations have been identified at still higher pressure: i) $\beta$- to $\delta$-MgH${_2}$ at 6.73 GPa and (ii) $\delta$- to $\epsilon$-MgH${_2}$ at 10.26~GPa.Comment: 4 pages, 4 figure

NLO Corrections to lepton pair production beyond the Standard Model at hadron colliders

We consider lepton pair production at a hadron collider in a class of effective theories with the relevant operators being four-fermion contact interaction. Despite the nonrenormalizable nature of the interaction, we explicitly demonstrate that calculating QCD corrections is both possible and meaningful. Calculating the corrections for various differential distributions, we show that these can be substantial and significantly different from those within the SM. Furthermore, the corrections have a very distinctive flavour dependence. And finally, the scale dependence of the cross sections are greatly reduced once the NLO corrections are taken into account.Comment: 23 pages, 14 figures, few typos corrected, written in JHEP styl