The CMS experiment announces new results for the EPS-HEP conference 2025 in Marseille. The new results comprise searches for new phenomena using exotic signatures to precision measurements of standard model processes. Links to the Physics Analysis Notes for EPS-HEP and to briefings will be added to this page throughout the conference, as the new results are presented and the notes are made public. In the following, a subset of the results is highlighted.

Searches for new phenomena

• For Run 3, the reach of the CMS experiment for so-called exotic signatures, such as long-lived particles, was significantly increased, and new trigger strategies were developed. CMS releases a preliminary version of a detailed report about “Long-lived particle triggers at CMS: strategy and performance during early LHC Run 3” (EXO-23-016).
• The search for decays of the known 125 GeV Higgs boson into two light bosons which then each decay further into two fermions or bosons are important components of the program to fully explore the properties of the Higgs boson. For EPS-HEP, results for two unexplored decay channels are made public, the process H→aa→μμττ (SUS-23-005) and H→aa→μμhh, where h denotes a pion or a kaon (EXO-24-034). To reach the lowest possible mass of experimental signatures in which the two τ-leptons or hadrons are merged into one single detector object are exploited, yielding exclusion limits down to masses of 3.4 and 0.4 GeV, about two times the τ and h rest masses, respectively.

Properties of the Higgs boson

• Possible anomalous couplings of the Higgs boson to vector bosons and fermions are studied using multivariate analysis techniques in the decay of the Higgs bosons into two photons. Competitive limits on anomalous couplings and CP-violating contributions are set (HIG-24-006).
• At the LHC, the ratio of the production cross sections for a Higgs boson in association with a W⁺ or W^– boson is expected to show an asymmetry, due to the parton distribution functions of the proton favoring W⁺ over W^– production. Significant deviations could hint to unexpected charm quark coupling to the Higgs boson. CMS presents a first analysis of this process and finds agreement with expectations within the currently large statistical uncertainties (HIG-24-019).
• Another first analysis presented by CMS is the search for events containing three Higgs bosons. With the current data an upper limit of about 3400 times the standard model expectation is set (HIG-24-015).

Using the LHC as a collider of photons

• At the LHC, photons radiate off the incoming protons, and “fuse” into a final state with two heavy W bosons. The process of WW production in photon-fusion is expected to be mediated by trilinear and quartic gauge couplings. Moreover, effects from the strong interactions can be suppressed experimentally. CMS presents a precise measurement of the cross section, with an uncertainty of about 13%, in agreement with standard model expectations (SMP-24-019).

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