The electroweak production cross section of single top quarks is an important measurement for LHC, being a potential window on "new physics" effects.
Past achievements of this group include the very first measurement at 7 TeV (in t channel) with 2010 data, followed by the most precise inclusive cross section measurements of t-channel cross section at 7, 8 and 13 TeV, and the first differential measurements at 13 TeV; the most precise |Vtb| extraction from single top in the world; the first measurement of W-helicity fractions in a single-top topology; the first observation of the tW production mode; the first measurement of single-top polarization in t channel; stringent limits on anomalous tWb, tgu, tgc couplings.
External collaborators: CMS collaboration.
During 2012, the CMS and ATLAS collaborations independently reported unambiguous evidence of the existence of a new particle of mass around 125 GeV.
Several analyses are ongoing to challenge the hypothesis that the new particle is the SM Higgs. We focus on the search for its production in association with a single top quark. Due to an effect of quantum interference, this process is strongly suppressed in the Standard Model while it gets enhanced if its couplings to the top quark and to the W boson have opposite sign. An observation of this production mode would therefore be a convincing proof that this new particle does not belong to the Standard Model.
We published the first search for this process using 8 TeV data, and we expect to achieve sensitivity to anomalous values of the top Yukawa phase during the LHC Run-II.
Our group is involved in the trigger design and maintenance for the LHC Run II in order to select the most interesting collision events for topologies with a lepton and a b quark with the CMS detector. Given the final state, this trigger is of particular interest for top quark physics, but it is also relevant to many other analyses (including the single top plus Higgs search ongoing in our group). Studies are carried out to implement the latest CMS developments in physics object definitions into the trigger path as well as to optimize the selections for the best efficiency and the rate possible. Our group is responsible for the b-tagging part together with organizing the whole activities within the CMS top quark group. Andrey Popov is official contact person between the Top Quark group and the Trigger group.
External collaborators: CMS TOP PAG, CMS TSG.