Search results for "Collider"
showing 10 items of 1690 documents
Searching for Invisibly Decaying Higgs Bosons at LEP II
1996
We study the potential of LEP II to unravel the existence of invisibly decaying Higgs bosons, predicted in a wide class of models. We perform a model independent analysis, focusing our attention to the final state topologies exhibiting $b \bar{b}$ or $\ell^+ \ell^-$ ($\ell=\mu$ or $e$) pairs and missing energy. We carefully evaluate the signals and backgrounds, choosing appropriate cuts to enhance the discovery limits. Our results demonstrate that LEP II is capable of discovering such a Higgs boson for a wide range of masses and couplings.
Search for Higgs boson production in oppositely charged dilepton and missing energy events inpp¯collisions ats=1.96 TeV
2012
We present a search for the standard model Higgs boson using events with two oppositely charged leptons and large missing transverse energy as expected in $H\rightarrow WW$ decays. The events are selected from data corresponding to 8.6 \ifb\ of integrated luminosity in $p \bar{p}$ collisions at $\sqrt{s}=1.96$ TeV collected with the D0 detector at the Fermilab Tevatron Collider. No significant excess above the standard model background expectation in the Higgs boson mass range this search is sensitive to is observed, and upper limits on the Higgs boson production cross section are derived.
Measurement of the Higgs boson mass from theH→γγandH→ZZ*→4ℓchannels inppcollisions at center-of-mass energies of 7 and 8 TeV with the ATLAS detector
2014
An improved measurement of the mass of the Higgs boson is derived from a combined fit to the reconstructed invariant mass spectra of the decay channels H -> gamma gamma and H -> ZZ* -> 4l. The analysis uses the pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at center-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of 25 fb(-1). The measured value of the Higgs boson mass is m(H) = 125.36 +/- 0.37(stat) +/- 0.18 (syst) GeV. This result is based on improved energy-scale calibrations for photons, electrons, and muons as well as other analysis improvements, and supersedes the previous result from ATLAS. Upper limits on t…
Further search for supersymmetry ats=7 TeVin final states with jets, missing transverse momentum, and isolated leptons with the ATLAS detector
2012
This work presents a new inclusive search for supersymmetry (SUSY) by the ATLAS experiment at the LHC in proton-proton collisions at a center-of-mass energy root s = 7 TeV in final states with jets, missing transverse momentum and one or more isolated electrons and/or muons. The search is based on data from the full 2011 data-taking period, corresponding to an integrated luminosity of 4.7 fb(-1). Single-lepton and multilepton channels are treated together in one analysis. An increase in sensitivity is obtained by simultaneously fitting the number of events in statistically independent signal regions, and the shapes of distributions within those regions. A dedicated signal region is introduc…
Measurements of the electron and muon inclusive cross-sections in proton–proton collisions at s=7 TeV with the ATLAS detector
2012
This Letter presents measurements of the differential cross-sections for inclusive electron and muon production in proton-proton collisions at a centre-of-mass energy of root s = 7 TeV, using data collected by the ATLAS detector at the LHC. The muon cross-section is measured as a function of p(T) in the range 4 < p(T) < 100 GeV and within pseudorapidity vertical bar eta vertical bar < 2.5. In addition the electron and muon cross-sections are measured in the range 7 < p(T) < 26 GeV and within vertical bar eta vertical bar < 2.0, excluding 1.37 < vertical bar eta vertical bar < 1.52. Integrated luminosities of 1.3 pb(-1) and 1.4 pb(-1) are used for the electron and muon measurements, respecti…
Vector-like leptons: Higgs decays and collider phenomenology
2013
We study the impact of heavy vector-like leptons on several observables in collider and low-energy physics. These states, present in many well-motivated extensions of the Standard Model, can induce lepton flavour violation and non-standard Higgs decays. We study these effects in an effective model inspired by the composite Higgs scenario. After deriving bounds on the mass and production cross-section of the vector-like states using recent LHC data on multilepton searches, we discuss the modification of the Higgs decays to dilepton, diphoton and $Z\gamma$ final states as well as low-energy observables like radiative lepton decays, the anomalous magnetic moment of the muon and the electric di…
ATLAS Tile Calorimeter performance with Run 1 data
2016
Abstract The performance of the central hadronic calorimeter, TileCal, in the ATLAS Experiment at the Large Hadron Collider is studied using cosmic-ray muons and the large sample of proton-proton collisions acquired during the Run 1 of LHC (2010–2012). Results are presented for the precision of the absolute energy scale and timing, noise characterization, and time-stability of the detector. The results show that the Tile Calorimeter performance is within the design requirements of the detector.
Status of the g-2 experiment at BNL
1999
The muon g-2 experiment at Brookhaven has successfully completed two exploratory runs using pion injection and direct muon injection for checkout and initial data taking. The main components of the experiment, which include the pion beam line, the superconducting storage ring and inflector magnets, the muon kicker and the lead-scintillating fiber calorimeters have been satisfactorily commissioned. First results on the anomalous magnetic moment of the positive muon from pion injection are in good agreement with previous experimental results for a(mu+) and a(mu-) from CERN and of comparable accuracy (13 ppm). Analysis of the 1998 muon injection run is in progress and expected to improve the p…
New measurements of at COMPASS
2007
One of the main goals of the COMPASS experiment at CERN is the determination of the gluon polarisation in the nucleon, Δ G / G . It is determined from spin asymmetries in the scattering of polarised muons at 160 GeV/c on a polarised LiD target. The gluon polarisation is accessed by the selection of photon-gluon fusion events. Such events are tagged either with a charmed meson or a hadron pair with high transverse momenta in the final state. The selection of charmed mesons is based on the reconstruction of decayed D ⋆ and D 0 mesons in the COMPASS spectrometer. For the high- p T hadron pairs two independent analyses are performed in the kinematic regimes of DIS ( Q 2 > 1 ( GeV / c ) 2 ) and …
Charmonium Production at Tevatron, HERA and LHC
1998
Charmonia hadro- and photo-production are analyzed in the framework of the color-octet model taking into account higher-order effects induced by initial-state radiation of gluons. We argue that color-octet matrix elements obtained from Tevatron data might be reconciled with those extracted from HERA data on inelastic $J/\psi$ photoproduction. Finally we estimate cross sections for events with muons from prompt $J/\psi$'s as a background for the B physics programme at LHC experiments.