Studying of the Higgs boson properties
The last element of the Standard Model which has been missing until recently is the Higgs boson. Its discovery was announced at CERN on 4 July 2012. The Higgs boson is the Higgs field particle, responsible for the presence or absence of elementary particles masses. Up to now, the more detailed studies of the newly discovered particle's properties reveal it to be compatible with the Standard Model Higgs boson. However, scientists are looking for more Higgs particles which, according to almost all high energy extensions of the Standard Model, should exist. ATLAS will better measure these properties, enabling a clearer picture to emerge about whether this particle is the Higgs Boson, or the first of a larger family of such particles, or something else entirely.
MEPhI group in collaboration with CERN (Geneva, Switzerland), New York University (New York, USA), University of Copenhagen (Copenhagen, Denmark) and Istituto Nazionale di Fisica Nucleare (Frascati, Italy) takes an active part in these researches.
MEPhI group makes a substantial contribution to the photon identification algorithm, which is used to analyze the H→γγ process and will significantly reduce the systematic uncertainties on the measurements. There was also a significant theoretical work aimed at exploring the possible spin and parity of the Higgs boson.
Pic.2 pp→H→ZZ→4l process recorded by ATLAS in 2012.
MEPhI group focuses on the analysis of the asymmetries in the processes occurring in proton-proton beams collisions. Presence or absence of these asymmetries in the experiment will provide information on the possible CP-violation in the Higgs sector. To obtain a better description of proton-proton collisions we study a performance of new event generators that include radiative corrections to initial and final states (Next to Leading Order generators).
All these researches will help to start effective work with new experimental data in 2015.
Publications made in collaboration with MEPhI group members:
ATLAS Collaboration; «Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC», Phys. Lett. B 726 (2013) 88
ATLAS Collaboration; «Evidence for the spin-0 nature of the Higgs boson using ATLAS data», Phys. Lett. B 726 (2013) 120