The CMS collaboration is presenting over 25 new results at the 39th International Conference on High Energy Physics (ICHEP 2018) taking place in Seoul, South Korea from July 4th-July 11th, 2018.
A key highlight is a comprehensive combination of searches for Higgs boson pair production using the 2016 dataset. Such "di-Higgs" searches are crucial for constraining the Higgs boson self-coupling and help set constraints on new physics scenarios that predict enhancements in the production rate. Four different final states are considered, with one Higgs boson decaying into a bbbar pair and the other decaying into γγ, ττ, bbbar, or a pair of vector bosons. An observed (expected) 95% confidence level upper limit corresponding to 22.2 (12.8) times the theoretical prediction for the standard model (SM) cross section is set (Fig. 1) and is the most stringent to date at the LHC.
Fig. 1: 95% confidence level exclusion limits on the SM nonresonant Higgs boson pair production cross section for different channels. The inner (green) band and the outer (yellow) bands indicate the regions containing 68 and 95%, respectively, of the distribution of limits expected under the background-only hypothesis.
CMS continues to perform precision measurements in the Higgs sector with a comprehensive combination of measurements of differential Higgs boson production cross sections being presented at ICHEP. These measurements are sensitive probes for new physics beyond the standard model and allow CMS to set competitive new constraints on Higgs boson couplings.
An important result presented by CMS at ICHEP is a combination of analyses that studies the coupling of the Higgs boson to the top quark by searching for Higgs boson production in association with a single top quark (tH). Several decay modes and signatures are used to derive stringent constraints on the magnitude and relative sign of the Higgs couplings to top quarks and vector bosons. This exploration of Higgs couplings serves as an important extension of the original observation of Higgs production in association with two top quarks (ttH) by CMS.
CMS continues to perform a detailed scrutiny of the Standard Model with a measurement of electroweak WZ scattering in the leptonic decay channel WZ → lνl′l′, where l, l′ = e, μ. Electroweak production in association with two jets is measured with an observed (expected) significance of 1.9 (2.7) standard deviations. Stringent constraints on charged Higgs production and on anomalous quartic gauge couplings in terms of dimension-eight effective field theory operators are also presented. Measurements of the pp → WZ inclusive and differential production cross section and constraints on charged anomalous triple gauge couplings are presented as well.
Thirteen direct searches for new physics using the Run 2 dataset are being showcased by CMS at ICHEP. This includes a novel search using the 2016+2017 dataset (~80 fb-1) for dark matter in final states with a leptoquark and missing transverse momentum (Fig. 2). Leptoquarks appear in many well-motivated extensions of the SM, such as grand unification theories and models with composite quarks and leptons and have generated a lot of interest recently for addressing flavor anomalies observed in the B sector. While no significant excess is observed in the data, the dark matter signature investigated by CMS represents an until now uncovered signature in the search for dark matter. The study excludes leptoquarks with masses up to 1160 GeV for a dark matter mass of mDM≈ 300 GeV, and up to 1000 GeV for mDM ≈ 425 GeV. Other searches presented by CMS at ICHEP cover a wide range of topics and set stringent constraints on exotic resonances, leptoquarks, long-lived particles, dark matter models, and supersymmetric particles.
Fig 2: [Left] Feynman diagram for the signal process where g is a gluon, LQ a leptoquark, DM a dark matter particle, and X a new Dirac fermion. The superscript “*” indicates an off-shell particle. [Right] Observed upper limits at 95% confidence level (CL) on the product of cross section and branching fraction, for the signal model shown. The hatched (blue) band represents the region where the dark matter relic density requirement can be satisfied within 3 standard deviations (σ), including the Atomic Parity Violation (APV) bounds. The solid and dashed (black) curves show the observed and expected 95% CL exclusion limits.
List of recent results from CMS for the ICHEP2018 conference:
- B2G-17-015: Search for a heavy resonance decaying to a top quark and a vector-like top quark in the lepton+jets final state
- B2G-17-018: Search for a vector-like quark decaying to a top quark and a W boson
- EXO-16-050: Search for associated production of dark matter with a Higgs boson that decays to a pair of bottom quarks
- EXO-16-053: Search for new physics in final states with a single photon plus missing transverse momentum in proton-proton collisions at sqrt(s) = 13 TeV using 2016 data
- EXO-17-009: Search for pair production of first generation scalar leptoquarks at sqrt(s)=13 TeV
- EXO-17-015: Search for dark matter in final states with a leptoquark and missing transverse momentum in proton-proton collisions at 13 TeV
- EXO-17-016: Search for heavy neutrinos and third-generation leptoquarks in final states with two hadronically decaying τ leptons and two jets in proton-proton collisions at sqrt(s) = 13 TeV
- EXO-17-024: Search for low mass resonances decaying into bottom quark-antiquark pairs in pp collisions at sqrt(s) = 13 TeV
- EXO-17-030: Search for pair-produced three-jet resonances in proton-proton collisions at sqrt(s) = 13 TeV
- EXO-18-001: Search for new particles decaying to a jet and an emerging jet
- EXO-18-004: Coming soon.
- HIG-17-017: Search for Non-Resonant Higgs Pair-Production in the 4b Final State with the CMS detector
- HIG-17-025: Coming soon.
- HIG-17-028: Combined measurement and interpretation of differential Higgs boson production cross sections at sqrt(s) =13 TeV
- HIG-17-030: Combination of searches for Higgs boson pair production in proton-proton collisions at sqrt(s) =13 TeV
- HIG-18-005: Search for a heavy pseudoscalar boson decaying to a Z boson and a Higgs boson at sqrt(s)=13 TeV
- HIG-18-009: Search for the associated production of a Higgs boson and a single top quark in pp collisions at sqrt(s)=13TeV
- SMP-17-005: Measurement of differential cross sections for Z boson pair production in association with jets at sqrt(s) = 8 and 13 TeV
- SMP-18-001: Coming soon.
- SMP-18-002: Measurements of the pp→WZ inclusive and differential production cross section and constraints on charged anomalous triple gauge couplings.
- SUS-17-003: Coming soon.
- SUS-17-012: Search for supersymmetry using events with a photon, a lepton, and missing transverse momentum in pp collisions at sqrt(s) = 13 TeV
- TOP-17-008: Measurement of the top quark mass in the all-jets final state at sqrt(s)=13 TeV
- TOP-17-011: Measurement of the single top quark and antiquark production cross sections in the t channel and their ratio in pp collisions at sqrt(s)=13 TeV
- FTR-18-003: Search for vector boson fusion production of a massive resonance decaying to a pair of Higgs bosons in the four b quark final state at the HL-LHC using the CMS Phase 2 detector
- JME-17-001: Performance of missing transverse momentum in pp collisions at sqrt(s)=13 TeV using the CMS detector.
- LUM-17-002: CMS luminosity measurement using 2016 proton-nucleus collisions at nucleon-nucleon center-of-mass energy of 8.16 TeV