1,721,393 research outputs found
Phi Radiative decays at KLOE
No full textWe present results from the KLOE experiment about the phi -> f(0)(980)gamma -> pi(+)pi(-)gamma, the phi -> f(0)(980)gamma -> pi(0)pi(0)gamma, the measurement of the eta mass and the branching fractions BR(phi -> eta'gamma)/BR(phi -> eta gamma) with the pi(+)pi(-)7 gamma final state
Rare phi decays
No full textThe Kloe experiment has collected an integrated luminosity similar to 500pb (1) up to now, which means similar to 1.65 x 10(9) phi decays. The huge amount of events allowed us to measure rare phi decays. We measured the radiative decays of the phi meson into pi(0), eta and eta' (958). These measurements are relevant to assess the mixing in the pseudoscalar nonet as well as to evaluate the gluon content in the. eta' (958). Moreover also the radiative decays into pi(0)pi(0)gamma and eta pi(0)gamma have been measured. These decays are dominated by the final states f(0)(980) and a(0)(980). The measurement of the branching ratios and of the pi(0)pi(0) or eta pi(0) invariant mass spectrum helps to understand the controversial nature of the above scalar mesons
Study of the η â Ï+Ï-e+e-decay at KLOE
No full textThe KLOE experiment has concluded its data taking in March 2006, having acquired an integrated luminosity of 2.5 fb-1of e+e- collisions at the center of mass energy around the à ̧(1020) resonance. The complete data set includes a sample of 100 million η's produced through the radiative decay à ̧ ηÎ3 and tagged by means of the monochromatic recoil photon. This huge amount of data allows to perform the first test of CP violation in η decays through the study of the rare η Ï+Ï-e+e channel, measuring the asymmetry between the Ï+Ï-and the e+e-decay planes in the η rest frame (Ï). Being this process flavor conserving, such an observation will point to unexpected mechanism of CP violation, thus providing an hint of new physics beyond the Standard Model. A study of the η Ï+Ï-e+e-decay based on a data sample of 1.7 fb-1will be presented. Electrons and pions are identified using both the time of flight to the calorimeter and the momentum of each track. Cuts on track momenta and on photon conversion on the beam pipe allow to significantly reduce the background, with a final 20% contamination. The analysis efficiency for the signal is 8%, dominated by geometrical acceptance. The final sample of about 1600 signal events, 100 times larger than today best measurement, is used to measure both the η Ï+Ï-e+e-(Î3) branching fraction and the asymmetryÏ. © 2009 IOP Publishing Ltd
Search for CPT violation and decoherence effects in the neutral kaon system
No full textThe neutral kaon system offers a unique possibility to perform fundamental tests of CPT invariance, as well as of the basic principles of quantum mechanics. The most recent limits on several kinds of possible CPT violation and decoherence mechanisms, which in some cases might be justified in a quantum gravity framework, are reviewed, including the latest results obtained by the KLOE experiment at the DAΦNE e+e-collider. No deviation from the expectations of quantum mechanics and CPT symmetry is observed, while the precision of the measurements, in some cases, reaches the interesting Planck scale region. © 2009 IOP Publishing Ltd
Search for high-mass diboson resonances with boson-tagged jets in proton-proton collisions at √s = 8TeV with the ATLAS detector
No full textAbstract: A search is performed for narrow resonances decaying into WW, WZ, or ZZ boson pairs using 20.3 fb−1 of proton-proton collision data at a centre-of-mass energy of s=8 \sqrts=8 TeV recorded with the ATLAS detector at the Large Hadron Collider. Diboson resonances with masses in the range from 1.3 to 3.0 TeV are sought after using the invariant mass distribution of dijets where both jets are tagged as a boson jet, compatible with a highly boosted W or Z boson decaying to quarks, using jet mass and substructure properties. The largest deviation from a smoothly falling background in the observed dijet invariant mass distribution occurs around 2 TeV in the WZ channel, with a global significance of 2.5 standard deviations. Exclusion limits at the 95% confidence level are set on the production cross section times branching ratio for the WZ final state of a new heavy gauge boson, W′, and for the WW and ZZ final states of Kaluza-Klein excitations of the graviton in a bulk Randall-Sundrum model, as a function of the resonance mass. W′ bosons with couplings predicted by the extended gauge model in the mass range from 1.3 to 1.5 TeV are excluded at 95% confidence level.[Figure not available: see fulltext.
Measurement of the branching ratio Gamma(Λb0→ψ(2S)Λ0)/G(Λb0→J/ψΛ0) with the ATLAS detector
No full textAn observation of the Λb0→ψ(2S)Λ0 decay and a comparison of its branching fraction with that of the Λb0→J/ψΛ0 decay has been made with the ATLAS detector in proton-proton collisions at s=8 TeV at the LHC using an integrated luminosity of 20.6 fb-1. The J/ψ and ψ(2S) mesons are reconstructed in their decays to a muon pair, while the Λ0→ pπ- decay is exploited for the Λ0 baryon reconstruction. The Λb0 baryons are reconstructed with transverse momentum pT>10 GeV and pseudorapidity |η|<2.1. The measured branching ratio of the Λb0→ψ(2S)Λ0 and Λb0J/ψΛ0 decays is Gcyrillic(Λb0→ψ(2S)Λ0/Gcyrillic(Λb0J/ψΛ0)=0.501±0.033(stat)±0.019(syst), lower than the expectation from the covariant quark model
Measurement of the Lambda(0)(b) lifetime and mass in the ATLAS experiment
No full textA measurement of the Lambda(0)(b) lifetime and mass in the decay channel Lambda(0)(b) -> J/psi (mu(+) mu(-))Lambda(0)(p pi(-)) is presented. The analysis uses a signal sample of about 2200 Lambda(0)(b) and (Lambda) over bar (0)(b) decays that are reconstructed in 4.9 fb(-1) of ATLAS pp collision data collected in 2011 at the LHC center-of-mass energy of 7 TeV. A simultaneous mass and decay time maximum likelihood fit is used to extract the Lambda(0)(b) lifetime and mass. They are measured to be tau(Lambda b) = 1.449 +/- 0.036(stat) +/- 0.017(syst) ps and m(Lambda b) = 5619.7 +/- 0.7(stat) +/- 1.1(syst) MeV. DOI: 10.1103/PhysRevD.87.03200
Search for resonant diboson production in the WW/WZ -> lvjj decay channels with the ATLAS detector at root s=7 TeV
No full textA search for resonant diboson production using a data sample corresponding to 4.7 fb(-1) of integrated luminosity collected by the ATLAS experiment at the Large Hadron Collider in pp collisions at root s = 7 TeV is presented. The search for a narrow resonance in the WW or WZ mass distribution is conducted in a final state with an electron or a muon, missing transverse momentum, and at least two jets. No significant excess is observed and limits are set using three benchmark models: WW resonance masses below 940 and 710 GeV are excluded at 95% confidence level for spin-2 Randall-Sundrum and bulk Randall-Sundrum gravitons, respectively; WZ resonance masses below 950 GeV are excluded at 95% confidence level for a spin-1 extended gauge model W' boson
Vusand CP violation from kaon decays with the KLOE detector
No full textThe KLOE experiment has provided precise measurements of the branching ratio of the main neutral and charged kaon decay modes, of the Kland the K lifetimes, and of the Klvector and scalar form factors. We present a description of the above measurements and an overall fit of all our data, with particular attention to correlations. These data provide the basis for the determination of the value of the CKM matrix element Vusand a test of the unitarity of the quark mixing matrix. In addition our first measurement of the charge asimmetry in KSsemileptonic decays, AS, gaves us the possibility to contribute to the knowledge of () and testing the CPT symmetry through the Bell Steinberger relation. © 2009 IOP Publishing Ltd
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