Angular distributions of the decay B 0 → K * 0 µ + µ − are studied using a sample of proton-proton collisions at √ s = 8 TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 20.5 fb −1 . An angular analysis is performed to determine the P 1 and P 5 parameters, where the P 5 parameter is of particular interest because of recent measurements that indicate a potential discrepancy with the standard model predictions. Based on a sample of 1397 signal events, the P 1 and P 5 parameters are determined as a function of the dimuon invariant mass squared. The measurements are in agreement with predictions based on the standard model.
We consider CP violating effects in the decays τ → (3π)ν τ where both the J P = 1 + resonance, a 1 , and J P = 0 − resonance, π ′ , can contribute. The interference between the a 1 and π ′ resonances can lead to enhanced CP-violating asymmetries whose magnitudes depend crucially on the π ′ decay constant,We make an estimate of f π ′ with a simplified chiral Lagrangian coupled to a massive pseudoscalar field, and we compare the estimates from the nonrelativistic quark model and from the QCD sum rule with the estimate from the 'mock' meson model. We then estimate quantitatively the size of CPviolating effects in a multi-Higgs-doublet model and scalar-leptoquark models. We find that, while CP-violating effects in the scalar-leptoquark models may require more than 10 10 τ leptons, CP-violating effects from the multi-Higgsdoublet model can be seen at the 2σ level with about 10 7 τ leptons using the chiral Lagrangian estimate of f π ′ = (1 ∼ 5) × 10 −3 GeV.
A measurement of vector boson scattering and constraints on anomalous quartic gauge couplings from events with two Z bosons and two jets are presented. The analysis is based on a data sample of proton-proton collisions at √ s = 13 TeV collected with the CMS detector and corresponding to an integrated luminosity of 35.9 fb −1 . The search is performed in the fully leptonic final state ZZ → , where , = e or µ. The electroweak production of two Z bosons in association with two jets is measured with an observed (expected) significance of 2.7 (1.6) standard deviations. A fiducial cross section for the electroweak production is measured to be σ EW (pp → ZZjj → jj) = 0.40 +0.21 −0.16 (stat) +0.13 −0.09 (syst) fb, which is consistent with the standard model prediction. Limits on anomalous quartic gauge couplings are determined in terms of the effective field theory operators T0, T1, T2, T8, and T9. This is the first measurement of vector boson scattering in the ZZ channel at the LHC.The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. Within the solenoid volume are silicon pixel and strip tracking detectors, a lead tungstate crystal electromagnetic calorimeter (ECAL), and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections. Forward calorimeters extend the pseudorapidity η coverage provided by the barrel and endcap detectors up to |η| < 5. Muons are measured in gas-ionization detectors embedded in the steel flux-return yoke outside the solenoid.The silicon tracker measures charged particles within the pseudorapidity range |η| < 2.5. It consists of 1440 silicon pixel and 15 148 silicon strip detector modules. For nonisolated particles with 1 < p T < 10 GeV and |η| < 1.4, the track resolutions are typically 1.5% in p T and 25-90 (45-150) µm in the transverse (longitudinal) impact parameter [19].Electrons are measured in the pseudorapidity range |η| < 2.5 using both the tracking system and the ECAL. The momentum resolution for electrons with p T ≈ 45 GeV from Z → e + e − decays ranges from 1.7% for nonshowering electrons in the barrel region (|η| < 1.479) to 4.5% for showering electrons in the endcaps [20].
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