We present a precise measurement of the ratio RK=Γ(K→eν(γ))/Γ(K→μν(γ)) and a study of the radiative process K→eνγ, performed with the KLOE detector. The results are based on data collected at the ...Frascati e+e− collider DAΦNE for an integrated luminosity of 2.2 fb−1. We find RK=(2.493±0.025stat±0.019syst)×10−5, in agreement with the Standard Model expectation. This result is used to improve constraints on parameters of the Minimal Supersymmetric Standard Model with lepton flavor violation. We also measured the differential decay rate dΓ(K→eνγ)/dEγ for photon energies 10<Eγ< 250 MeV. Results are compared with predictions from theory.
The 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 obtained by the ...KLOE experiment at the DAΦNE
e
+
e
−
collider on several kinds of possible
CPT
violation and decoherence mechanisms, which in some cases might be justified in a quantum gravity framework, are reviewed. 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. Finally, prospects for this kind of experimental studies at KLOE-2 are presented.
Using a large sample of pure, slow, short lived K0 mesons collected with KLOE detector at DAΦNE, we have measured the KS lifetime. From a fit to the proper time distribution we find ...τ(KS)=(89.562±0.029stat±0.043syst) ps. This is the most precise measurement to date of the short lived K0 meson lifetime, in good agreement with the world average derived from previous measurements. We observe no dependence of the lifetime on the direction of the KS in galactic coordinates.
We describe the method of measuring the integrated luminosity of the e+e- collider DAΦNE, the Frascati φ-factory. The measurement is done with the KLOE detector selecting large angle Bhabha ...scattering events and normalizing them to the effective cross section. The e+e-→e+e-(γ) cross section is calculated using different event generators which account for the \(\mathcal{O}(\alpha)\) radiative initial and final state corrections, and the φ resonance contribution. The accuracy of the measurement is 0.6%, where 0.3% comes from systematic errors related to the event counting and 0.5% from theoretical evaluations of the cross section.
The 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.
Using a sample of over 400 million φ→KSKL decays produced during the years 2001 and 2002 at the DAΦNE e+e- collider, the ratio RSπ=Γ(KS→π+π-(γ))/Γ(KS→π0π0) has been measured with the KLOE detector. ...The result is RSπ=2.2555±0.0012stat±0.0021corr-stat±0.0050syst, which is in good agreement with the previously published result based on the KLOE data sample from the year 2000. The average of the KLOE results is RSπ=2.2549±0.0054, reducing the total error by a factor of three, to 0.25%.
The absolute branching ratio of the K+ → π+π−π+ (γ) decay, inclusive of final- state radiation, has been measured using ~17 million tagged K+ mesons collected with the KLOE detector at DAΦNE, the ...Frascati φ-factory. The result is: BR(K+ → π+π−π+ (γ)) 0.05565 ± 0.00031stat ± 0.00025syst
We have measured the cross section of the radiative process e+e−→π+π−γ with the KLOE detector at the Frascati ϕ-factory DAΦNE, from events taken at a CM energy W=1 GeV. Initial state radiation allows ...us to obtain the cross section for e+e−→π+π−, the pion form factor |Fπ|2 and the dipion contribution to the muon magnetic moment anomaly, Δaμππ=(478.5±2.0stat±5.0syst±4.5th)×10−10 in the range 0.1<Mππ2<0.85 GeV2, where the theoretical error includes a SU(3) χPT estimate of the uncertainty on photon radiation from the final pions. The discrepancy between the Standard Model evaluation of aμ and the value measured by the Muon g-2 collaboration at BNL is confirmed.
The KLOE experiment was the first to exploit Initial State Radiation (ISR) processes to obtain the e+e− → π+π−(γ) cross section below 1 GeV (70% of the leading order contribution to the muon anomaly) ...publishing two measurements with the photon in the initial state emitted at small angle in 2005 and 2008, and an independent measurement with the photon emitted at large angle in 2011. These measurements were normalized using luminosity from Bhabha. Here, we present the latest KLOE results on e+e− → π+π−(γ) cross section, obtained by the ratio σ(e+e− → π+π−)/σ(e+e− → μ+μ−) measurement for a total integrated luminosity of 239.2 pb−1. The comparison of the present results with with the previous ones performed by KLOE shows a good agreement, while they are in substantially agreement with the other ones obtained by CMD-2, SND and BaBar experiments. From the cross section we extract the pion form factor and the two-pion contribution in the invariant mass range of 592–975 MeV to the muon anomaly confirming the current discrepancy between standard model calculation and experimental measurement.
The existence of a light dark force mediator has been tested with the KLOE detector at DAΦNE. This particle, the so called dark photon U, has been searched for in three different processes and four ...different final states: a) Φ → ηU, with U → e+e−, η → π+π−π0 and η → π0π0π0; b) e+e− → Uγ with U → μ+μ−; c) e+e− → Uh' (dark Higgsstrahlung), U → μ+μ−, where h' is a Higgs-like particle responsible for the breaking of the hidden symmetry. We did not find any evidence of the processes above and set upper limits on the parameters of the model, for different MU (and Mh') mass ranges, depending on the considered final state.
PDF
