Valentina Zaccolo - University and INFN, Trieste, Italy
Soft-QCD physics at the LHC
The hadronic interactions are accurately described when the perturbative QCD
approach is used. This is true for hard processes with large momentum
transfer compared to the QCD scale. However, perturbative QCD fails to describe
hadronic interactions when the effective strong coupling constant is large,
i.e. for processes at low transverse momentum called soft.
Multiple Parton Interactions (MPI) are composed of semi-hard parton
interactions. Their contribution becomes more relevant at high centre-of-mass
energy of the colliding hadrons. However, the non-perturbative component of
MPI cannot be trivially separated from products of initial and final state
soft radiation and beam remnants from the proton break up. Therefore,
experimentally, one attempts to topologically separate the partons produced in
the hardest scattering from the softer part, called the Underlying Event.
In this seminar, some of the newest results about soft QCD at LHC will be
discussed. The focus will be on the characterisation of the event based on
topological constraints and on how these techniques can bring minimum-bias
and identified-particles studies to the precision era.