The Monte Carlo generator MAJOR 1.5 simulates the production and decay of heavy Majorana neutrinos via lepton mixing or exchange of 'light' right-handed W-bosons in deep inelastic scattering, i.e. e±p → NX → e±W∓X or veZX. Physics and programming aspects are described in this manual.

We show that the 'orthogonal' characteristics of the observed rapidity gaps and large forward energy flows in deep inelastic scattering at HERA, can be described within a single framework. Our Monte Carlo model is based on perturbative QCD matrix elements and parton showers together with Lund string model hadronization, but has in addition a new mechanism for soft colour interactions which modifie

The direct charmonium and bottomonium production rate observed at high [Formula presented] in [Formula presented] collisions at the Fermilab Tevatron is factors of 10 larger than predictions based on conventional perturbative QCD. We show that this excess can be accounted for by our model for soft color interactions, previously introduced to describe in a novel way the large rapidity gap events ob

We discuss our model for soft colour interactions and present results on the diffractive structure function F2D(β, xℙ, Q2) and inclusive transverse energy flows, which agree with available HERA data.

The color structure needed for resummation of all colored 2 -> 3 processes is calculated using multiplet inspired s-channel bases. In this way the resulting matrices, describing the color structure, are guaranteed to obey simplifying symmetries.

We introduce soft colour interactions as a novel mechanism to understand the observed events with large rapidity gaps in ep collisions at HERA. Colour exchanges between produced partons and colour-charges in the proton remnant modifies the colour structure for hadronization, such that colour singlet systems may appear well separated in rapidity. Our explicit model show characteristics of diffracti

We discuss how the renormalization scheme ambiguities in QCD can be fixed, when two observables are related, by requiring the coefficients in the perturbative expansion relating the two observables to have their conformal limit values, i.e., to be independent of the [Formula presented] function of the renormalized coupling. We show how the next-to-leading order BLM automatic scale-fixing method ca

The deep inelastic scattering 2+1 jet cross-section is a useful observable for precision tests of QCD, e.g. measuring the strong coupling constant αs. A consistent analysis requires a good understanding of the theoretical uncertainties and one of the fundamental ones in QCD is due to the renormalisation scheme and scale ambiguity. Different methods, which have been proposed to resolve the scale am

We analyze some of the different determinations of αs(mτ 2) that can be found in the literature and the numerical impact of their possible weaknesses with the publicly available non-strange spectral function from ALEPH tau decays. We also introduce some novel approaches. We find very stable results and uncertainties dominated by the perturbative part. Our final value is αs(mτ 2)=0.328±0.013.

Heavy Majorana neutrinos (N), predicted in various extensions of the standard model, are examined with respect to the present limits on their masses and mixings with ordinary leptons resulting in explicit examples of allowed values of interest for present and planned accelerator energies. The decay N→Zv is added to the previously available formalism and all dominating branching ratios are calculat

We present a comprehensive study of the determination of the strong coupling from τ decay, using the most recent release of the experimental ALEPH data. We critically review all theoretical strategies used in previous works and put forward various novel approaches which allow one to study complementary aspects of the problem. We investigate the advantages and disadvantages of the different methods

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The strong coupling from ALEPH tau decays. We use the publically available non-strange spectral function from ALEPH tau decays to critically analyze the different determinations of αs(mτ2) that can be found in the literature and the numerical impact of their possible weaknesses. We also introduce some novel approaches. We find that perturbative uncertainties dominate. Our results with different ap

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Using the most recent release of the ALEPH τ decay data, we present a very detailed phenomenological update of the αs(mτ 2) determination. We have exploited the sensitivity to the strong coupling in many different ways, exploring several complementary methodologies. All determinations turn out to be in excellent agreement, allowing us to extract a very reliable value of the strong coupling. We fin

In a previous paper, one of us pointed out that the anomalous dimension matrices for all physical processes that have been calculated to date are complex symmetric, if stated in an orthonormal basis. In this paper we prove this fact and show that it is only true in a subset of all possible orthonormal bases, but that this subset is the natural one to use for physical calculations.

Using the updated ALEPH V-. A spectral function from τ decays, we determine the lowest spectral moments of the left-right correlator and extract dynamical information on order parameters of the QCD chiral symmetry breaking. Uncertainties associated with violations of quark-hadron duality are estimated from the data, imposing all known short-distance constraints on a resonance-based parametrization