Today the CMS collaboration revealed several new analyses based on the full dataset the LHC collected in 2011. As usually, the recurrent theme was "no-significant-excess-was-found". Here is a selection of the most interesting searches and limits.
In this analysis, filed under "4th generation", one looks for a heavier copy of the top quark: a fermionic particle with charge 2/3 produced in pairs and decaying to one b-quark and one W boson. We sort of know by now there is no 4th generation of quarks and leptons in nature, nevertheless this search is relevant to more interesting new physics models. For example, in a large class of little Higgs and composite Higgs models the fermionic partner of the top quark decays as t' → b W about half of the time. The current limit on the t' mass assuming 100% branching fraction for the t' → b W decay is 525 GeV. For little Higgs et al. the limit is slightly weaker, slightly above 400 GeV (due to the smaller branching fraction) but that is also beginning to feel uncomfortable from the point of view of naturalness of these models.
This time the target is a heavy cousin of the W boson, decaying to one lepton and one neutrino. Unlike in the former case, there is no compelling theoretical reasons for such a creature to exist. However they represent a characteristic and clean signature that is fairly straightforward to look for: an energetic electron or muon accompanied by missing energy from a neutrino. To tell W' from the ordinary W boson one looks for events with a large transverse mass (for an on-shell particle whose decay products include a neutrino the transverse mass is less than the particle mass). Intriguingly, in the muon channel an outlier event with a very large transverse mass of 2.4 TeV is observed in the data. Of course, most likely it's just a fluke, but in any case it'll be interesting to see what ATLAS has in store.
t-tbar resonance searches
This search targets heavy (more than 1 TeV) particles decaying to a pair of top quarks, a signature very common in models with a new strongly interacting sector, like composite Higgs or the Randall-Sundrum model. Such a particle would produce a bump in the invariant mass spectrum of t-tbar pairs, which are otherwise copiously produced at the LHC. Top quark decays most often to 3 hadronic jets, but for a heavy mother resonance the daughter top quarks move so quickly that their decay products merge into one fat jet. Therefore this search relies on fancy modern techniques of studying substructure of jets, in order to identify closely packed jets that could originate from a fast moving top quark. No resonance is observed in the t-tbar spectrum. What is interesting is that the LHC sensitivity now reaches the cross sections predicted by popular versions of the Randall-Sundrum model, excluding Kaluza-Klein gluons lighter than about 1.5 TeV. My guess is that the explanation of the Tevatron anomalous top forward-backward asymmetry in terms of heavy KK gluon is now dead and gone.
The only vanilla SUSY search updated with the full 2011 dataset is the one in the Z+jets+missing energy channel. This is not the first place you'd look for supersymmetry (that would be jets+MET); this search is relevant to a subset of models where a cascade of neutralinos and gravitons produces, often enough, an shell Z boson. Therefore the limits on the gluino mass are not stunning: 600-900 GeV depending on how squeezed is the SUSY spectrum. More spectacular SUSY limits are probably saved for the Moriond conference in about 1 month from now.
For more details, more models, more limits, and more disappointment have a look at the slides or the original summary notes on the CMS wiki page.