  Understanding the fundamental structure of matter requires an understanding
of how quarks and gluons are assembled to form hadrons and of the structure of
the protons which are the colliding particles at LHC. The arrangement of quarks
and gluons inside nucleons can be probed by accelerating electrons, hadrons or
nuclei to precisely controlled energies, smashing them into a target nucleus
and examining in detail the final products. The LHC physics program is rich and
has been widely described. It encompasses the searches for new particles up to
masses of several TeV, including the elucidation of electroweak symmetry
breaking and the possible observation of new symmetries at higher scales, and
precision measurements of fundamental parameters in the electroweak and strong
gauge sectors. Obviously, this program requires a precise understanding of the
structure of the proton in terms of quarks and gluons, obtained from HERA and
Tevatron. However, the knowledge on parton distribution functions (PDFs) is
still limited for many aspects of LHC physics and the discovery potential is
thus reduced. In this proceeding, we show on one example that it is possible to
find some observables less sensitive to PDF uncertainties to probe with a high
efficency new physics beyond the standard model.
