By CMS Collaboration

The CMS collaboration continues with its rich harvesting of the large Run 2 dataset with 21 new results presented at the LHCP 2018 conference in Bologna, Italy. The results cover a wide assortment of topics and range from precision measurements of the Higgs boson and Standard Model (SM) processes to searches for rare decays and exotic phenomena.

A recent highlight from CMS has been the first observation of the associated production of a Higgs boson with a top quark-antiquark pair or “ttH production”. This measurement, first reported in April 2018 and now published in the journal Physical Review Letters [Phys. Rev. Lett. 120, 231801 (2018)], establishes the tree-level coupling of the Higgs boson to the top quark and is a major milestone towards the measurement of the Higgs boson coupling to fermions. CMS has now extended this exploration of Higgs couplings and presents at LHCP a new analysis that studies in a more general way the coupling of the Higgs boson to the top quark by searching for Higgs boson production in association with a single top quark (tH). CMS also presents measurements of the properties of the Higgs boson using the latest dataset collected in 2017 and the H -> ZZ -> 4l (l=e, μ) decay channel. The results have been combined with the 2016 dataset and are found to be consistent, within their uncertainties, with the expectations for the SM Higgs Boson.

A major highlight for CMS at LHCP is the first observation of well-resolved chi_b1(3P) and chi_b2(3P) signals, and a measurement of their masses, using Y(3S)+photon decays reconstructed from 80 fb-1 of pp data collected at 13 TeV. The photons interact in the material of the CMS tracker and convert to electron-positron pairs whose momentum is measured in CMS magnetic spectrometer, providing the superb resolution needed to separate the two states whose mass differs by only 10 MeV. Measurements of the chi_bJ(3P) triplet states, with total angular momentum J=0,1, and 2, probe details of the bbbar interaction and contribute to an improved understanding of quarkonium spectroscopy and hadron formation.

 

A detailed scrutiny of the Standard Model continues with precision measurements of the inclusive photon and the photon + jets production cross sections as well as measurements of the differential ttbar cross section. A notable highlight from CMS includes the first experimental evidence for single top quark production in association with a photon.

 

CMS has also released 11 direct searches for new physics using the Run 2 dataset. A wide array of topics have been covered and stringent constraints have been set on the production of black holes and string balls, supersymmetric particles, new, heavy gauge bosons and other hypothetical particles such as leptoquarks. In particular, CMS presents at LHCP a novel search for a Z’ gauge boson using Z->4μ events and including the latest dataset from 2017. The results from this search place strong constraints on theories that attempt to explain various experimental anomalies including the lack of a dark matter signal in direct detection experiments, tension in the measurement of the anomalous magnetic moment of the muon, and reports of possible lepton flavor universality violation in B-meson decays.

These results come soon after Quark Matter 2018 where a number of CMS results utilizing the heavy ion data-taking runs were presented.

 

An event candidate for the production of a top quark and top anti-quark pair in conjunction with a Higgs Boson in the CMS detector. The Higgs decays into a tau+ lepton and a tau- lepton; the tau+ in turn decays into hadrons and the tau- decays into an electron.  The decay product symbols are in blue. The top quark decays into three jets (sprays of lighter particles) whose names are given in purple. One of these is initiated by a b-quark. The top anti-quark decays into a muon and b-jet, whose names appear in red.

 
Distribution of the four-lepton reconstructed invariant mass m4l in the full mass range combining 2016 and 2017. Points with error bars represent the data and stacked histograms represent expected distributions of the signal and background processes.
 

The invariant mass distribution of the χbJ(3P) → Υ(3S)γ candidates. The vertical bars are the statistical uncertainties. The curves represent the fitted contributions of the two signal peaks, the background, and their sum.

 

List of new results for LHCP2018:

  1. B2G-16-027: http://cds.cern.ch/record/2621420​​
  2. B2G-17-017: http://cds.cern.ch/record/2621631​
  3. B2G-17-019: http://cds.cern.ch/record/2621541
  4. BPH-13-002: http://cds.cern.ch/record/2621286
  5. BPH-16-003: http://cds.cern.ch/record/2621562
  6. BPH-17-008: arXiv:1805.11192 (Submitted to PRL)
  7. EXO-16-056: arXiv:1806.00843 (Submitted to JHEP)
  8. EXO-17-008: http://cds.cern.ch/record/2621539
  9. EXO-17-018: http://cds.cern.ch/record/2621291
  10. EXO-17-019: http://cds.cern.ch/record/2621548
  11. EXO-17-021: http://cds.cern.ch/record/2621292
  12. EXO-17-023: arXiv:1805.06013 (Submitted to JHEP)
  13. EXO-18-008: http://cds.cern.ch/record/2621297
  14. HIG-17-016: http://cds.cern.ch/record/2621422
  15. HIG-18-001: http://cds.cern.ch/record/2621419
  16. HIG-18-007: http://cds.cern.ch/record/2621550
  17. LUM-17-004: http://cds.cern.ch/record/2621960
  18. SMP-16-003: http://cds.cern.ch/record/2621421
  19. SUS-17-008: http://cds.cern.ch/record/2621561
  20. TOP-17-014: http://cds.cern.ch/record/2621975
  21. TOP-17-016: http://cds.cern.ch/record/2621426

News