C. Oleari

Next-to-leading order jet distributions for Higgs boson production via weak boson fusion

The weak-boson fusion process is expected to provide crucial information on Higgs boson couplings at the Large Hadron Collider at CERN. The achievable statistical accuracy demands comparison with next-to-leading order QCD calculations, which are presented here in the form of a fully flexible parton Monte Carlo program. QCD corrections are determined for jet distributions and are shown to be modest, of order 5 to 10% in most cases, but reaching 30% occasionally. Remaining scale uncertainties range from order 5% or less for distributions to below +-2% for the Higgs boson cross section in typical weak-boson fusion search regions.

The tensor reduction and master integrals of the two-loop massless crossed box with light-like legs

Abstract The class of the two-loop massless crossed boxes, with light-like external legs, is the final unresolved issue in the program of computing the scattering amplitudes of 2→2 massless particles at next-to-next-to-leading order. In this paper, we describe an algorithm for the tensor reduction of such diagrams. After connecting tensor integrals to scalar ones with arbitrary powers of propagators in higher dimensions, we derive recurrence relations from integration-by-parts and Lorentz-invariance identities, that allow us to write the scalar integrals as a combination of two master crossed boxes plus simpler-topology diagrams. We derive the system of differential equations that the two master integrals satisfy using two different methods, and we use one of these equations to express the second master integral as a function of the first one, already known in the literature. We then give the analytic expansion of the second master integral as a function of ϵ=(4−D)/2, where D is the space–time dimension, up to order O (ϵ 0 ) .

The two-loop scalar and tensor Pentabox graph with light-like legs

We study the scalar and tensor integrals associated with the pentabox topology: the class of two-loop box integrals with seven propagators — five in one loop and three in the other. We focus on the case where the external legs are light-like and use integration-by-parts identities to express the scalar integral in terms of two master-topology integrals and present an explicit analytic expression for the pentabox scalar integral as a series expansion in e=(4−D)/2. We also give an algorithm based on integration by parts for relating the generic tensor integrals to the same two master integrals and provide general formulae describing the master integrals in arbitrary dimension and with general powers of propagators.

Scalar one loop integrals using the negative dimension approach

Abstract We study massive one-loop integrals by analytically continuing the Feynman integral to negative dimensions as advocated by Halliday and Ricotta and developed by Suzuki and Schmidt. We consider n -point one-loop integrals with arbitrary powers of propagators in general dimension D . For integrals with m mass scales and q external momentum scales, we construct a template solution valid for all n which allows us to obtain a representation of the graph in terms of a finite sum of generalised hypergeometric functions with m + q −1 variables. All solutions for all possible kinematic regions are given simultaneously, allowing the investigation of different ranges of variation of mass and momentum scales. As a first step, we develop the general framework and apply it to massive bubble and vertex integrals. Of course many of these integrals are well known and we show that the known results are recovered. To give a concrete new result, we present expressions for the general vertex integral with one off-shell leg and two internal masses in terms of hypergeometric functions of two variables that converge in the appropriate kinematic regions. The kinematic singularity structure of this graph is sufficiently complex to give insight into how the negative-dimension method operates and gives some hope that more complicated graphs can also be evaluated.

Physics at a 100 TeV pp collider: Standard Model processes

This chapter documents the production rates and typical distributions for a number of benchmark Standard Model processes, and discusses new dynamical phenomena arising at the highest energies available at this collider. We discuss the intrinsic physics interest in the measurement of these Standard Model processes, as well as their role as backgrounds for New Physics searches.This chapter documents the production rates and typical distributions for a number of benchmark Standard Model processes, and discusses new dynamical phenomena arising at the highest energies available at this collider. We discuss the intrinsic physics interest in the measurement of these Standard Model processes, as well as their role as backgrounds for New Physics searches.This chapter documents the production rates and typical distributions for a number of benchmark Standard Model processes, and discusses new dynamical phenomena arising at the highest energies available at this collider. We discuss the intrinsic physics interest in the measurement of these Standard Model processes, as well as their role as backgrounds for New Physics searches.

A phenomenological study of heavy-quark fragmentation functions in e+e− annihilation

Abstract We consider the computation of D and B fragmentation functions in e + e − annihilation. We compare the results of fitting present data using the next-to-leading-logarithmic resummed approach, versus the O (α s 2 ) fixed-order calculation, including also mass-suppressed effects. We also propose a method for merging the fixed-order calculation with the resummed approach.We consider the computation of D and B fragmentation functions in e+e- annihilation. We compare the results of fitting present data using the next-to-leading-logarithmic resummed approach, versus the O(alpha_s^2) fixed-order calculation, including also mass-suppressed effects. We also propose a method for merging the fixed-order calculation with the resummed approach.

QCD corrections to electroweak nu(l) j j and l+ l- j j production

The production of W or Z bosons in association with two jets is an important background to the Higgs boson search in vector-boson fusion at the LHC. The purely electroweak component of this background is dominated by vector-boson fusion, which exhibits kinematic distributions very similar to the Higgs boson signal. We consider the next-to-leading order QCD corrections to the electroweak production of l nu_l jj and l^+ l^- jj events at the LHC, within typical vector-boson fusion cuts. We show that the QCD corrections are modest, increasing the total cross sections by about 10%. Remaining scale uncertainties are below 2%. A fully-flexible next-to-leading order partonic Monte Carlo program allows to demonstrate these features for cross sections within typical vector-boson-fusion acceptance cuts. Modest corrections are also found for distributions.

Sudakov resummation effects in prompt-photon hadroproduction

We compute the effects of soft-gluon resummation, at the next-to-leading-logarithmic level, in the fixed-target hadroproduction cross section for prompt photons. We find in general that the corrections to the fixed next-to-leading-order results are large for large renormalization scales, and small for small scales. This leads to a significant reduction of the scale dependence of the results for most experimental configurations of interest. We compare our results to the recent measurements by the E706 and UA6 collaborations.

Application of the negative-dimension approach to massless scalar box integrals

Abstract We study massless one-loop box integrals by treating the number of space-time dimensions D as a negative integer. We consider integrals with up to three kinematic scales ( s , t and either zero or one off-shell legs) and with arbitrary powers of propagators. For box integrals with q kinematic scales (where q =2 or 3) we immediately obtain a representation of the graph in terms of a finite sum of generalised hypergeometric functions with q −1 variables, valid for general D . Because the power each propagator is raised to is treated as a parameter, these general expressions are useful in evaluating certain types of two-loop box integrals which are one-loop insertions to one-loop box graphs. We present general expressions for this particular class of two-loop graphs with one off-shell leg, and give explicit representations in terms of polylogarithms in the on-shell case.

Kinematical limits on Higgs boson production via gluon fusion in association with jets

In this paper, we analyze the high-energy limits for Higgs boson plus two jet production. We consider two high-energy limits, corresponding to two different kinematic regions: a) the Higgs boson is centrally located in rapidity between the two jets, and very far from either jet; b) the Higgs boson is close to one jet in rapidity, and both of these are very far from the other jet. In both cases the amplitudes factorize into impact factors or coefficient functions connected by gluons exchanged in the t channel. Accordingly, we compute the coefficient function for the production of a Higgs boson from two off-shell gluons, and the impact factors for the production of a Higgs boson in association with a gluon or a quark jet. We include the full top quark mass dependence and compare this with the result obtained in the large top-mass limit.