Higgs Candidate and Mass and Spin-Parity Analysis – CHAMPS

The project consists of developping complete analysis chain, from triggering system to statistical interpretation with :
- innovative algorithms exploiting the new Level 1 Trigger (L1) architecture of the CMS detector,
- new reconstruction algorithms for leptons, adapated to th new data taking conditions and integrated in a global event description of collisions recorded by CMS
- deployement of a new approach of Matrix Element Techniques (MEM) at Next-to-Leading-Order (NLO) to measure the properties of the Higgs boson.

- New electron energy estimate by means of a MVA regression technique. New MVA combination of ECAL and tracker measurements for best resolution on electron momentum (30% improvement).
- Innovative algorithms exploiting the new L1 Trigger architecture for electrons/photons and taus : dynamtic clustering, shower shape to discriminate signal from background, isolation and pile-up mitigation.
- Preliminary of a Matrix Element Method at Leading Order for H->TauTau final state.

The main outstanding feature are the performances of the L1 algorithms wrt current system:
- 30% gain in energy resolution,
- factor 4 improvement in position resolution,
- L1 trigger rates divided by a factor 2.
The implementation in the firmwares of the electronic cards is on-going. It will be validated in 2015 and fully deployed in 2016.

MEM at LO for H->TauTau will be deployed in a full analysis chain in 2015, for a publication in 2016.
VBF production mode of the Higgs will be observed in 2016 in both H->ZZ->4 leptons and H->2 taus thanks to the new MEM techniques we developed.

The results obtained by the team have been included in several publications :

[1] S. Chatrchyan et al. [CMS Collaboration], Phys. Rev.D 89 (2014) 9, 092007 [arXiv:1312.5353 [hep-ex]]
[2] V.Khachatryan et al. [CMS Collaboration], Submitted to JINST, arXiv:1502.02701
[3] J.B. Sauvan [CMS Collaboration], J. Phys.Conf. 587 (2015)
[4] L. Mastrolorenzo [CMS Collaboration] Proceedings of ICHEP 2014, to be published.

The recent discovery of a new boson X by the two experiments (ATLAS and CMS) of the Large Hadron Collider (LHC) is a major breakthrough in the understanding of the fundamental interactions. It could help to elucidate the nature of the spontaneous electroweak symmetry breaking (EWSB) mechanism presumed responsible for the appearance of the mass of the elementary particles in the early moments of the Universe.
The decay channels with charged leptons in the final state offer the best opportunities for an exhaustive study of the properties of the new boson. The X-> ZZ*-> 4l channel (where l is an electron or a muon) is the « golden » mode for the discovery. It allows in stand-alone for a precise determination of the mass mX. It moreover can provide a determination of the spin-parity state (S^CP) by exploiting the kinematics of disintegration in the center of mass of the resonance. The X -> 2 taus channel is essential to establish the existence of a direct coupling to leptons. The coupling to tau leptons is the only lepton coupling eventually accessible at the LHC in the timescale of this project. It moreover can provide a good sensitivity to SP, through the study of the polarization of the tau leptons, while offering some sensitivity to boson mass.
The X boson production modes can be distinguished experimentally in a rather clean manner in both of the X-> ZZ* -> 4l and X -> 2 taus channels, by the presence of additional leptons or jets. In particular, the distinction between the production by gluon fusion (through virtual loops of top quarks), by associated production with a vector boson W or Z, or by vector boson fusion (ZZH and WWH) is particularly important for the constraint on the couplings.
The aim of this very challenging project is to develop and deploy innovative and powerful analysis techniques to provide the best measurements of the properties of the new boson, via leptonic final states, at the LHC with higher energy and luminosity. It consists of providing for the first time at the LHC an analysis chain with new lepton reconstruction techniques incorporated in a global description of the events, interleaved with a full interpretation via event weighting based on a novel Matrix Element approach at next-to-leading order. It will benefit from the unique expertise in Europe at the Laboratoire Leprince Ringuet (LLR) of the Ecole Polytechnique, and with partners from the Fakultet elektrotehnike strojarstva i brodogradnje (FESB) in Split (Croatia), on leptons (reconstruction, identification and isolation of charged leptons), as well as on the X-> ZZ*->4l and X ->2 taus analysis in the CMS experiment at the LHC.