Abstract The production of a pair of τ leptons via photon–photon fusion, , is observed for the first time in proton–proton collisions, with a significance of 5.3 standard deviations. This observation is based on a data set recorded with the CMS detector at the LHC at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb−1. Events with a pair of τ leptons produced via photon–photon fusion are selected by requiring them to be back-to-back in the azimuthal direction and to have a minimum number of charged hadrons associated with their production vertex. The τ leptons are reconstructed in their leptonic and hadronic decay modes. The measured fiducial cross section of is . Constraints are set on the contributions to the anomalous magnetic moment ( ) and electric dipole moments ( ) of the τ lepton originating from potential effects of new physics on the vertex: and (95% confidence level), consistent with the standard model.
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Test of lepton flavor universality in B±→K±μ+μ− and B±→K±e+e− decays in proton-proton collisions at s=13TeV
Abstract A test of lepton flavor universality in and decays, as well as a measurement of differential and integrated branching fractions of a nonresonant decay are presented. The analysis is made possible by a dedicated data set of proton-proton collisions at recorded in 2018, by the CMS experiment at the LHC, using a special high-rate data stream designed for collecting about 10 billion unbiased b hadron decays. The ratio of the branching fractions to is determined from the measured double ratio of these decays to the respective branching fractions of the with and decays, which allow for significant cancellation of systematic uncertainties. The ratio is measured in the range , whereqis the invariant mass of the lepton pair, and is found to be , in agreement with the standard model expectation . This measurement is limited by the statistical precision of the electron channel. The integrated branching fraction in the sameq2range, , is consistent with the present world-average value and has a comparable precision.
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- Award ID(s):
- 2121686
- PAR ID:
- 10521896
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Reports on Progress in Physics
- Volume:
- 87
- Issue:
- 7
- ISSN:
- 0034-4885
- Format(s):
- Medium: X Size: Article No. 077802
- Size(s):
- Article No. 077802
- Sponsoring Org:
- National Science Foundation
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