By CMS Collaboration

While the work on improvements on the detector continues during the Long Shutdown 2, physicists are starting to reap the rewards of the LHC dataset collected in LHC Run 2. The dataset is the largest sample ever collected at a collider and equivalent to an integrated luminosity of about 140 inverse femtobarns, equivalent to about 5% of the total data that LHC is expected to deliver in its lifetime. At the 66th Rencontres de Moriond conference, the Compact Muon Solenoid collaboration has presented over 36 new results, of which 7 are using analysis of data collected in 2018 in combination with earlier collected data to amount to the largest datasets ever analysed.

The world-class precision of the Compact Muon Solenoid experiment is taken advantage of in both measurements and searches. Other studies are currently based on smaller datasets while work is proceeding on calibrations with ultimate precision for the most recent data.  But even in the analyses that already exploit this very large dataset, many analyses pursue novel strategies that have not been used before at the large hadron collider. The results cover a wide assortment of topics and range from precision measurements of the Higgs boson and Standard Model processes to searches for rare decays and exotic phenomena.

Since its discovery in 2012 the Higgs boson has become one of the focuses of the essential tests of the Standard Model. New results were presented on the production of Higgs bosons when the Higgs boson decays to two Z bosons, one of the most important ways to observe the Higgs boson and the easiest way to study its properties. It is also possible to use the production of two Z bosons to investigate if there are further subtle changes compared to the Standard Model prediction. The new study of ZZ production provides unprecedented experimental precision on the production probability of about 3%, of similar size as the theoretical predictions. Both analyses use the data collected by the CMS experiment in 2016, 2017 and 2018. [Read more: CMS-PAS-HIG-19-001 - CMS-PAS-SMP-19-001 ]


The CMS collaboration also presents new results on the search for the production of four top quarks. The production is a rare process that is about a factor ten less likely to be produced than Higgs bosons together with two top quarks, and about factor ten thousand smaller than the production of just a top quark pair. The analysis has indirect sensitivity to the strength of the interaction between the Higgs boson and the top quark, called the Yukawa coupling, and shows the currently best sensitivity to the process. As four top quark production can be predicted by calculations in Quantum Chromodynamics, it is possible to test for any deviations from the Standard model production. A complementary and novel approach where the Yukawa coupling is directly measured from the behaviour of top quark pairs is now also available, and this is the first time this model-independent approach is used at a hadron collider. [Read more: Physics summary four tops soon - Physics summary top yukawa from top quark pairs - CMS-PAS-TOP-18-003 - CMS-PAS-TOP-17-019 - CMS-PAS-TOP-17-004 ]


Searches for new, long-lived particles with decay lengths of the order of centimetres have been one of the most active research areas in the past years and require specialised reconstruction techniques. The precise time information obtained in the electromagnetic calorimeters had already been used to search for photons originating from delayed decay. For the first time at the LHC, this technique is applied to jets, leading to the most stringent limits to date for some of the models predicting long-lived particles decaying to jets. [ Read more: physics summary - CMS-PAS-EXO-19-001 ]


The very large new dataset has also been used to extend the sensitivity to the production of strongly interacting supersymmetric particles. This search used the established signature of multiple jets and missing transverse momentum, but has been extended to cover cases where a long-lived, charged particle decays within the tracker volume to soft and invisible products, leading to a signature of a “disappearing” track that would only be identified with dedicated algorithms. Such long-lived, charged particles are predicted by many supersymmetric models. The power of the analysis is illustrated for the case when supersymmetric partners of the gluon (gluino) would produce long-lived particles in their decay chain, and the inclusion of the signature in the analysis significantly increases the sensitivity in terms of the gluino mass. [Read more: physics summary - CMS-PAS-SUS-19-005 ]


Another scenario for physics beyond the Standard Model is the existence of vector-like quarks. Here the data are examined for evidence of these particles using a novel machine learning technique to simultaneously identify and classify jets coming from Higgs, W and Z bosons and top quarks, yielding the strongest limits to date for these particles. [Read more: physics summary - CMS-PAS-B2G-18-005 ]


These results show that the CMS collaboration is not only able to analyse the very large data sample that was only collected recently but also could include many novel techniques that have not been used before. There are many more results in preparation on this dataset, using the large dataset to its full potential.

List of new CMS results for conferences in the winter of 2019:


Search for standard model production of four top quarks in final states with same-sign and multiple leptons in proton-proton collisions at sqrt(s) = 13 TeV


Search for new physics in multilepton final states in pp collisions at sqrt(s) = 13 TeV


Measurement of the pp→ZZ production cross section at sqrt(s) = 13 TeV with the Run 2 data set


Measurements of properties of the Higgs boson in the four-lepton final state in proton-proton collisions at sqrt(s) = 13 TeV


Measurement of Higgs boson production and decay to the ττ final state


First constraints on invisible Higgs boson decays using tt¯H production at sqrt(s) = 13 TeV


Search for a heavy Higgs boson decaying to a pair of W bosons in proton-proton collisions at sqrt(s) = 13 TeV


Search for heavy Higgs bosons decaying to a top quark pair in proton-proton collisions at sqrt(s) = 13 TeV


Combined search for gauge-mediated supersymmetry with photons in 13 TeV collisions at the CMS experiment


Search for a pseudoscalar boson in the mass range from 4 to 15 GeV produced in decays of the 125 GeV Higgs boson in the final states with two muons and two nearby tracks at sqrt(s) = 13 TeV


Search for long-lived particles using delayed jets and missing transverse momentum with proton-proton collisions at sqrt(s) = 13 TeV


Search for excited leptons decaying via contact interaction to two leptons and two jets


Evidence for WW production from double-parton interactions in proton-proton collisions at sqrt(s)=13 TeV


Search for τ→3μτ→3μ decays using ττ leptons produced in D and B meson decays


Search for physics beyond the standard model in events with two same-sign leptons or at least three leptons and jets in proton-proton collisions at sqrt(s)=13 TeV


Searches for new phenomena in events with jets and high values of the MT2 variable, including signatures with disappearing tracks, in proton-proton collisions at sqrt(s)=13 TeV - Read the physics summary


Search for boosted quark-antiquark resonances produced in association with a photon at sqrt(s)=13 TeV

SMP-17-011 arXiv:1903.04040

Measurement of electroweak production of a W boson in association with two jets in proton-proton collisions at sqrt(s)=13 TeV


Search for new physics in events with collimated photons and gluons


Search for pair production of vector-like quarks in the fully hadronic channel - read the physics summary


Measurements of Higgs boson production via gluon fusion and vector boson fusion in the diphoton decay channel at sqrt(s)=13 TeV

SUS-17-011 arXiv:1903.07070

Search for supersymmetry in final states with photons and missing transverse momentum in proton-proton collisions at 13 TeV


Search for a charged Higgs boson decaying into top and bottom quarks in proton-proton collisions at sqrt(s)=13 TeV in events with electrons or muons


Search for resonances decaying to a pair of Higgs bosons in the bbqqℓν final state in proton-proton collisions at sqrt(s)=13 TeV


Statistical combination of CMS searches for heavy resonances decaying to a pair of bosons or leptons at sqrt(s)=13 TeV


Search for neutral MSSM Higgs bosons decaying to μ+μ− in pp collisions at sqrt(s)=13 TeV


Search for a light charged Higgs boson decaying to a W boson and a CP-odd Higgs boson in eμμ/μμμ + jets channels in proton-proton collisions at sqrt(s)=13 TeV


Search for a heavy pseudoscalar Higgs boson decaying into a 125 GeV Higgs boson and a Z boson in final states of two light leptons and two tau leptons at sqrt(s)=13 TeV


Search for Higgs and Z boson decays to J/ψ J/ψ  or ΥY pairs in proton-proton collisions at sqrt(s)=13 TeV


Measurement of differential cross sections and charge ratios for t-tbar-channel single top quark production at 13 TeV


Search for the production of W±W±W∓ events with two equally charged or three leptons at sqrt(s)=13 TeV


Search for standard model production of four top quarks with the single-lepton and opposite-sign dilepton final states in proton-proton collisions at sqrt(s)=13 TeV


Measurement of top quark pair production in association with a Z boson in proton-proton collisions at sqrt(s)=13 TeV


Constraining the top quark Yukawa coupling from tt¯tt¯ differential cross sections in the lepton+jets final state in proton-proton collisions at sqrt(s)=13 TeV - read the physics summary


Search for anomalous electroweak production of WW/WZ/ZZ boson pairs in association with two jets in proton-proton collisions at 13 TeV


Search for dark matter particles produced in association with the Higgs boson in proton-proton collisions at sqrt(s)=13 TeV





Observation of two excited B+c states and measurement of the B+c (2S) mass in pp collisions at √s = 13 TeV

All CMS preliminary results - All CMS journal papers