We derive compact analytical formulae of the Bonneau-Martin type for the reaction e + e − → ¯ f f γ with cuts on minimal energy and acollinearity of the fermions, where the photons may be emitted both from the initial or final states. Soft photon exponentiation is also taken into account. One of the cleanest scattering processes at elementary particle accelerators is fermion-pair production in ...

One of the major goals of the Large Hadron Collider is to probe the electroweak symmetry breaking mechanism and the generation of the masses of the elementary particles. We review the physics of the Higgs sector in the Standard Model and some of its extensions such as supersymmetric theories and models of extra dimensions. The prospects for discovering the Higgs particles at the LHC and the stu...

T he search for physics beyond the standard model—our current best description of fundamental particles and the interactions between them—is a top priority at high-energy particle accelerators. But researchers are also searching for new physics in the “low-energy” environment of the nucleus through a process known as neutrinoless double-beta (0νββ) decay. This hypothetical decay would show that...

In addition to optimal conditions, invariant laws of Lorentz, parity and time reversal are imposed to find the relation between observables (spin rotation parameters) and bilinear combination of helicity amplitudes in pion-proton elastic scattering at 6.0 GeV/c. By normalizing the differential cross-section to unity, the magnitudes of helicity amplitudes and the angle between them are dete...

Antiproton proton annihilation reactions allow unique access to the moduli and phases of nucleon electromagnetic form factors in the time like region. We present the helicity amplitudes for the unequal mass single photon reaction p p̄ → l+ l− in the s channel including the lepton mass. The relative signs of these amplitudes are determined using simple invariance properties. Helicity amplitudes f...

INTRODUCTION Protons, electrons, neutrons, neutrinos and even quarks are often featured in news of scientific discoveries. All of these, and a whole "zoo" of others, are tiny sub-atomic particles too small to be seen even with the microscopes. While molecules and atoms are the basic elements of familiar substances that we can see and feel, we have to "look" within atoms in order to learn about ...

That a Majorana neutrino theory is different from a Dirac neutrino theory (even in the zero mass limit) is proved in two sentences. Fermion Statistics For the reactions (Dirac) e + e − → ν ¯ ν and (Majorana) e + e − → νν wherein the two final particles are presumed to have opposite helicity, in the Dirac case the neutrino and anti-neutrino are different particles so that Ψ Dirac (p 1 , λ 1 ; ¯ ...

The new matrix element generator AMEGIC++ is introduced, dedicated to describe multi–particle production in high energy particle collisions. It automatically generates helicity amplitudes for the processes under consideration and constructs suitable, efficient integration channels for the multi–channel phase space integration. The corresponding expressions for the amplitudes and the integrators...

We discuss the possible applications supersymmetric theories might nd in the eld of elementary particle physics. The supersymmetric generalization of the SU(3) SU(2) U(1) standard model is discussed in detail. Special attention has been devoted to the question of gauge coupling constant uni cation in the framework of supersymmetric grand uni ed models. * Lecture given at the conference "Gauge T...