The special role played by singly polarized high-energy hadron-hadron collisions in Spin Physics is discussed: In such processes, the measured and the calculated quantities can be and have been directly compared with each other — without data-extrapolation and without sum rules. It is in this kind of processes, where significant asymmetries (up to 30-40%) have been observed. It is also in this ...

The production of W and Z0 bosons in collisions of longitudinally polarized protons allows to access various combinations of the polarized quark distributions from the study of double and single spin asymmetries. We compute the O(αs) corrections to these asymmetries as function of the vector boson rapidity y in the hadron–hadron centre-of-mass frame. Detailed studies of the numerical impact of ...

We describe a general approach to quark flavor tagging in polarized hadronic processes, with particular emphasis on semi-inclusive deep inelastic scattering. A formalism is introduced that allows one to relate chosen quark flavor polarizations to an arbitrary combination of final-state hadron asymmetries. Within the context of the presented formalism, we quantify the sensitivity of various semi...

Large Hadron Collider (LHC) experiments this year have shown the existence of a new boson that resembles the Higgs boson. Although it is known that this particle has couplings to other particles that increase with their masses, the spin of the newly discovered boson is undetermined as of yet. The Higgs boson has been predicted to be a spin 0 particle. The LHC boson is not a spin 1 particle, sug...

We investigate the Collins effect in single spin asymmetries (SSAs) of the pp→ πX process, by taking into account the transverse momentum dependence of the microscopic sub-process cross sections, with the transverse momentum in the Collins function integrated over. We find that the asymmetries due to the Collins effect can only explain the available data at best qualitatively, by using our choi...

The transverse polarization, or transversity, distribution of quarks h1(x) – also called ∆T q(x) – has been the subject of an intense theoretical work in the last decade (for reviews, see Refs. 1 and 2), and the corresponding observables are now actively investigated in many experiments. Let us start by recalling the partonic definition of h1(x). Given a transversely polarized hadron, if we den...

In this paper we describe Herwig++ version 2.1, a general-purpose Monte Carlo event generator for the simulation of hard lepton-lepton and hadron-hadron collisions. A number of important hard scattering processes are available, together with an interface via the Les Houches Accord to specialized matrix element generators for additional processes. The simulation of Beyond the Standard Model (BSM...

COMPASS is a running fixed-target experiment at the CERN SPS with a rich physics program focused on nucleon spin structure and on hadron spectroscopy. One of the main goals of the spin program is the measurement of the transverse spin effects in semi-inclusive DIS off transversely polarised nucleons. In the years 2002, 2003 and 2004 data have been taken using a 160 GeV /c naturally polarised µ ...

In the past year, polarized deep inelastic scattering experiments at CERN and SLAC have obtained structure function measurements off proton, neutron and deuteron targets at a level of precision never before achieved. The measurements can be used to test the Bjorken and Ellis-Jaffe sum rules, and also to obtain information on the parton distributions in polarized nucleons. We perform a global le...