Determination ofW-boson properties at hadron colliders

Abstract

Methods for measuring the W-boson properties at hadron colliders are discussed. It is demonstrated that the ratio between the W-and Z-boson observables can be reliably calculated using fixed order perturbative QCD, even when the individual W-and Z-boson observables are not. Hence, by using a measured Z-boson observable and the perturbative calculation of the ratio of the W-over Z-boson observable, we can accurately predict the W-boson observable. The use of the ratio reduces both the experimental and theoretical systematic uncertainties substantially. Compared to the currently used methods it might, at high luminosity, result in a smaller overall uncertainty on the measured W-boson mass and width. ͓S0556-2821͑98͒00509-8͔

Towards a fitting procedure for deeply virtual Compton scattering at next-to-leading order and beyond

“…respectively 11 . This mixing arises in NLO and is induced by the breaking of special conformal symmetry in LO.…”

“…In such fits, based on traditional χ 2 minimization, the error estimation using the hypothesis of linear error propagation has become standard in the last few years [3,4,5,8]. To overcome drawbacks of this traditional method, alternative frameworks of statistical inference [11] and neural network parameterization [12,13] have been proposed.…”

Questions on uncertainties in parton distributions

“…Thus fitting the data simultaneously leads to a certain degree of inconsistency. One could keep only those sets which are clearly consistent with each other (within the context of NLO QCD) [9]. However, this leads to a severe restriction in the amount of data used, and the partons in some regions would lose important constraints.…”

“…The procedure of determining parton distributions by so-called global fits to data, mainly structure functions, is long established [1]- [9]. However, it is a rather more recent development to try to determine the errors on these distributions at the same time.…”

HERAFitter - an open source QCD fit framework

“…Various types of uncertainties can be handled using following implemented methods: hessian [17], Monte Carlo [18,19] or offset [20]. The hessian method is a standard way of computing the eigenvectors corresponding to the uncertainty sources by diagonalizing a matrix of second derivatives of the χ 2 distribution.…”