Inclusive Higgs Boson Searches in Four-Lepton Final States at the LHC

The inclusive search for the Standard Model Higgs boson in four-lepton final states with the ATLAS and CMS detectors at the LHC pp collider is presented. The discussion focusses on the H-> ZZ^(*)->4l+X decay mode for a Higgs boson in the mass range 120 ~< M_H ~< 600 GeV/c^2. A prospective analysis is presented for the discovery potential based on a detailled simulation of the detector response in the experimental conditions of the first years of LHC running at low luminosity. An overview of the expected sensitivity in the measurement of the Higgs boson properties is also given.Comment: 4 pages, 5 figures, uses moriond.st

Measurement of gauge boson couplings and W spin density matrix

During the LEP2 period the e+e- collider increased its center of mass energy from 161 GeV to 209 GeV and a total integrated luminosity of approximately 700 pb-1 was recorded per experiment. Pairs of W bosons are produced and allow the study of gauge boson couplings involving W, Z and photon. The coupling of the W boson to the neutral gauge bosons have been measured and are in agreement with the Standard Model prediction. Limits are set on CP-violating couplings by a Spin Density Matrix analysis of the W decay products. No evidence has been found for couplings of three neutral gauge bosons. Limits are derived on couplings of four gauge bosons.Comment: 8 pages, 6 figure

(Anomalous) Gauge boson couplings

During the LEP2 period the e+e − collider increased its center-of-mass energy from 161 GeV up to 209 GeV. A total integrated luminosity of approximately 700 pb−1 was recorded per experiment. Massive W bosons are dominantly produced in pairs via e +e − interactions and gauge couplings involving the charged gauge bosons W+ and W−, and the neutral gauge bosons γ and Z, are studied by the LEP experiments. The LEP measurement of the coupling of the W boson to the neutral gauge bosons, g Z 1 = 0.984+.022 −.019, κγ = 0.973+.044 −.045, and λγ = −0.028+.020 −.021, are in agreement with the Standard Model expectation g Z 1 = 1, κγ = 1, and λγ = 0. Couplings between tree and four neutral gauge bosons are forbidden by the Standard Model. No evidence has been found for couplings of three neutral gauge bosons, parametrized by f Z,γ 4,5 and h Z,γ 1,2,3,4 . Limits are derived on couplings of four gauge bosons, parametrized by a Z,W 0 /Λ 2 , a W n /Λ 2 and a Z,W c /Λ 2 where Λ represents the energy scale for new physics. A lower limit on the techni-ρ mass of 600 GeV/c2 is set at 95% confidence level by the ALEPH experiment

The Data Quality Monitoring for the CMS Silicon Strip Tracker

The CMS Silicon Strip Tracker (SST), consisting of more than 10 million channels, is organized in about 15,000 detector modules and it is the largest silicon strip tracker ever built for high energy physics experiments. The Data Quality Monitoring system for the Tracker has been developed within the CMS Software framework. More than 100,000 monitorable quantities need to be managed by the DQM system that organizes them in a hierarchical structure reflecting the detector arrangement in subcomponents and the various levels of data processing. Monitorable quantities computed at the level of individual detectors are processed to extract automatic quality checks and summary results that can be visualized with specialized graphical user interfaces. In view of the great complexity of the CMS Tracker detector the standard visualization tools based on histograms have been complemented with 2 and 3 dimensional graphical images of the subdetector that can show the whole detector down to single channel resolution. The functionalities of the CMS Silicon Strip Tracker DQM system and the experience acquired during the SST commissioning will be described

Measurement of W Polarisation at LEP

The three different helicity states of W bosons produced in the reaction e+ e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to measure the polarisation of W bosons, and its dependence on the W boson production angle. The fraction of longitudinally polarised W bosons is measured to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model expectation

Neutral-Current Four-Fermion Production in e+e- Interactions at LEP

Neutral-current four-fermion production, e+e- -> ffff is studied in 0.7/fb of data collected with the L3 detector at LEP at centre-of-mass energies root(s)=183-209GeV. Four final states are considered: qqvv, qqll, llll and llvv, where l denotes either an electron or a muon. Their cross sections are measured and found to agree with the Standard Model predictions. In addition, the e+e- -> Zgamma* -> ffff process is studied and its total cross section at the average centre-of-mass energy 196.6GeV is found to be 0.29 +/- 0.05 +/- 0.03 pb, where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model prediction of 0.22 pb. Finally, the mass spectra of the qqll final states are analysed to search for the possible production of a new neutral heavy particle, for which no evidence is found

Measurement of Exclusive rho+rho- Production in Mid-Virtuality Two-Photon Interactions and Study of the gamma gamma* -> rho rho Process at LEP

Exclusive rho+rho- production in two-photon collisions between a quasi-real photon, gamma, and a mid-virtuality photon, gamma*, is studied with data collected at LEP at centre-of-mass energies root(s)=183-209GeV with a total integrated luminosity of 684.8pb^-1. The cross section of the gamma gamma* -> rho+ rho- process is determined as a function of the photon virtuality, Q^2, and the two-photon centre-of-mass energy, W_gg, in the kinematic region: 0.2GeV^2 < Q^2 <0.85GeV^2 and 1.1GeV < W_gg < 3GeV. These results, together with previous L3 measurements of rho0 rho0 and rho+ rho- production, allow a study of the gamma gamma* -> rho rho process over the Q^2-region 0.2GeV^2 < Q^2 < 30 GeV^2

Search for Anomalous Couplings in the Higgs Sector at LEP

Anomalous couplings of the Higgs boson are searched for through the processes e^+ e^- -> H gamma, e^+ e^- -> e^+ e^- H and e^+ e^- -> HZ. The mass range 70 GeV < m_H < 190 GeV is explored using 602 pb^-1 of integrated luminosity collected with the L3 detector at LEP at centre-of-mass energies sqrt(s)=189-209 GeV. The Higgs decay channels H -> ffbar, H -> gamma gamma, H -> Z\gamma and H -> WW^(*) are considered and no evidence is found for anomalous Higgs production or decay. Limits on the anomalous couplings d, db, Delta(g1z), Delta(kappa_gamma) and xi^2 are derived as well as limits on the H -> gamma gamma and H -> Z gamma decay rates

Measurement of W Polarisation at LEP

The three different helicity states of W bosons produced in the reaction e+ e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to measure the polarisation of W bosons, and its dependence on the W boson production angle. The fraction of longitudinally polarised W bosons is measured to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model expectation

Measurement of the Running of the Electromagnetic Coupling at Large Momentum-Transfer at LEP

The evolution of the electromagnetic coupling, alpha, in the momentum-transfer range 1800GeV^2 < -Q^2 < 21600GeV^2 is studied with about 40000 Bhabha-scattering events collected with the L3 detector at LEP at centre-of-mass energies 189-209GeV. The running of alpha is parametrised as: alpha(Q^2) = alpha_0/(1-C Delta alpha(Q^2)), where alpha_0=\alpha(Q^2=0) is the fine-structure constant and C=1 corresponds to the evolution expected in QED. A fit to the differential cross section of the e+e- ->e+e- process for scattering angles in the range |cos theta|<0.9 excludes the hypothesis of a constant value of alpha, C=0, and validates the QED prediction with the result: C = 1.05 +/- 0.07 +/- 0.14, where the first uncertainty is statistical and the second systematic