Kaon decay studies seeking new-physics (NP) effects in leptonic (K_l2) or semileptonic (K_l3) decays are discussed.
A unitarity test of the first row of the CKM mixing matrix is obtained from the KLOE precision measurements of Kl3 widths for K^+-, K_L, and (unique to KLOE) K_S, complemented with the absolute branching ratio for the K_mu2 decay.
KLOE results lead to constraints for NP models and can probe possible charged Higgs exchange contribution in SM extensions with two Higgs doublets.
The main focus in the present document is set on a new measurement of R_K=Gamma(K_e2)/Gamma(K_mu2) with an accuracy at the % level, aiming at finding evidence of deviations from the SM prediction induced by lepton-flavor violation NP effects.
Working at a $ϕ$-factory, KLOE/KLOE-2 has collected a very large and clean sample of $η$ decays, which allow to perform a variety of precision measurements. This report presents the recent results on the $η$-meson decays from KLOE/KLOE-2 experiments, including the search of the $C$-violating decay $η\rightarrowγγγ$, the determination of the $CP$ asymmetry in $η\rightarrowπ^+π^-e^+e^-$, the precision measurement of the $η\rightarrowπ^+π^-π^0$ Dalitz plot distribution, the search for the $CP$-violating decay $η\rightarrowπ^+π^-$ and the precision measurement of ${\cal O}(p^6)$ dominated decay $η…
We describe the KLOE detector at DAFNE, and its physics program. The impact of our results on flavor and hadron physics to date, as well as an outlook for further improvement in the near future, are discussed.
The preliminary result on the absolute branching ratio of the decay K+ to pi+ pi0 (gamma), obtained by the KLOE experiment operating at the DAPHNE Frascati Phi-Factory, is presented.
Using a large sample of pure, slow, short lived K0 mesons collected with KLOE detector at DaFne, we have measured the KS lifetime. From a fit to the proper time distribution we find tau = (89.562 +- 0.029_stat +- 0.043_syst) ps. This is the most precise measurement today in good agreement with the world average derived from previous measurements. We observe no dependence of the lifetime on the direction of the Ks.
The KLOE collaboration has searched for the phi to K0 K0bar gamma decay using a sample of 1.4 fb-1 of e+e- collisions at W ~ M(phi) collected with the KLOE experiment at the Frascati e+e- collider DAFNE. No previous search exists for this decay, while many theory models predict a BR of 10-8 for this channel. We set a preliminary value of the U.L. on this BR to 1.8x10-8 at 90% C.L.. This limit rules out most of the existing theory predictions.
This paper describes the current neutral Kaon dataset and physics measurements of KLOE at DAFNE. A brief discussion on the prospects for detector upgrades and analysis of other K0 rare decays is also included.
Recent results obtained by the KLOE experiment operating at DA$Φ$NE, the Frascati $ϕ$-factory, are presented. They mainly concern neutral kaon decays including the $K_L$ dominant branching ratios, the $K_L$ lifetime and the extraction of the $CKM$ parameter $V_{us}$ from the $K_L$ semileptonic decays and lifetime. The best world upper limit on $K_S \to \pppo$ channel is also presented
The KLOE experiment has been running since April 1999 at the DAFNE e+e- collider at a center of mass energy centered around the phi meson mass. The luminosity integrated up to September 2002 is about 500 pb-1 . Here we present the perspectives on the measurement of the V_{us} CKM-matrix element with the KLOE detector, using both charged and neutral kaon semileptonic decays.
Study of semileptonic decays of neutral kaons allows to perform a test of discrete symmetries, as well as basic principles of the Standard Model. In this paper a general review on dependency between charge asymmetry constructed for semileptonic decays of short- and long-lived kaons and $\mathcal{CPT}$ symmetry is given.
Recent KLOE measurements allowing the extraction of the Vus element of the CKM matrix are here briefly described. The status of the resulting value of Vus is summarized. The perspectives for the completion of ongoing analyses are discussed, with particular emphasis on the measurements of scalar form factor slopes from study of KLmu3 and of Vus from the decay width of K+-l3.
We have measured the branching ratio BR(phi --> pi0 pi0 gamma) with the KLOE detector using a sample of ~5x10^7 phi decays. phi mesons are produced at DAFNE, the Frascati phi-factory. We find BR(phi --> pi0 pi0 gamma) = (1.09 +- 0.03 (stat) +- 0.05 (syst))x10^-4. We fit the two--pion mass spectrum to models to disentangle contributions from various sources.
The KLOE detector at DAFNE has collected about 30 pb-1 by the end of year 2000,' allowing, among other things, accurate measurements on several decay channels of the K0S meson. With data acquired in the year 2000 run we have measured the ratio of the branching ratios of the K0S to two charged and neutral pions to 1.5 percent accuracy. The branching ratio of the semileptonic decay of the K0S is also measured to 5 percent accuracy, the best measurement of this BR to date.
The absolute branching ratio of the $K^+ \rightarrow π^+π^-π^+(γ)$ decay, inclusive of final-state radiation, has been measured using $\sim$17 million tagged $K^+$ mesons collected with the KLOE detector at DA$Φ$NE, the Frascati $ϕ$-factory. The result is: \[ BR(K^+ \rightarrow π^+π^-π^+(γ)) = 0.05565 \pm 0.00031_{stat} \pm 0.00025_{syst} \] a factor $\simeq$ 5 more precise with respect to the previous result. This work completes the program of precision measurements of the dominant kaon branching ratios at KLOE.
In a sample of 5.3x10^7 phi-decays observed with the KLOE detector at the Frascati phi-factory Dafne we find 605 eta pi0 gamma events with eta --> gammaγand 197 eta pi0 gamma events with eta --> pi+ pi- pi0. The decay phi --> eta pi0 gamma is dominated by the process phi --> a0 gamma. From a fit to the eta pi0 mass spectrum we find BR(phi --> ao(980) gamma)= (7.4 +- 0.7)x10^-5.
Study of semileptonic decays of neutral kaons allows to perform a test of discrete symmetries, as well as basic principles of the Standard Model. In this paper a general review on dependency between charge asymmetry constructed for semileptonic decays of short- and long-lived kaons and CPT symmetry is given. The current status of determination of charge asymmetry for short-lived kaon, obtained by reconstruction of about 10^5 KS -> pen decays collected at DAFNE with the KLOE detector is also reviewed.
We have measured the fully inclusive K+ -> mu+nu(gamma) absolute branching ratio with the KLOE experiment at DAFNE, the Frascati Phi-factory. From some 865,283 K+ -> mu+nu(gamma) decays obtained from a sample of about 5.2x10^8 Phi-meson decays, we find BR(K+ -> mu+ nu (gamma)) = 0.6366 +-0.0009(stat.) +-0.0015(syst.), corresponding to an overall fractional error of 0.27%. Using recent lattice results on the decay constants of pseudoscalar mesons one can obtain an estimate for the CKM mixing matrix element |Vus|=0.2223+-0.0026.
The KLOE experiment has collected 2.4 1/pb of integrated luminosity during the commissioning of the DAFNE phi-factory in 1999. The performance of the detector has been studied using phi -> KL KS decays collected during this period, yielding also first measurements of relevant K parameters such as masses and lifetimes. A clean Kshort -> pi+ pi- sample is used to select Klong -> 2pi CP-violating decays and Klong -> Kshort regeneration events in the detector material. Results on the regeneration probability in beryllium-alluminum alloy and carbon-fiber plus aluminum composite are presented.
The existence of a light dark force mediator has been tested with the KLOE detector at DAPHNE. This particle, called U, is searched for using the decay chain phi-->etaU, eta-->pi+pi-pi0, U-->e+e-. No evidence is found in 1.5 fb-1 of data. The resulting exclusion plot covers the mass range 5<M_U<470 MeV, setting an upper limit on the ratio between the U boson coupling constant and the fine structure constant, alpha'/alpha, of <= 2x10^-5 at 90% C.L. for 50<M_U<420 MeV.
We have searched for the decay Ks->3p^0 with the KLOE experiment at DAFNE using data from e^+ e^- collisions at a center of mass energy W= m(phi) for an integrated luminosity L=450 pb^-1. The search has been performed with a pure Ks beam obtained by tagging with Kl interactions in the calorimeter and detecting six photons. We find an upper limit for the branching ratio of 1.2x10^-7 at 90% C.L.
A sample of 1.25x10^9 phi decays, collected with the KLOE detector at the Frascati phi-factory DAFNE at center of mass energy ~ Mphi, has been used to study the radiative decay phi to eta pi0 gamma. This decay is dominated by phi to a0(980) gamma. Two decay chains, corresponding to eta to gamma gamma and eta to pi+ pi- pi0, have been selected. We found respectively: Br(phi to eta pi0 gamma)=(6.92 +/- 0.10 (stat.) +/- 0.20 (syst.))x10^(-5) and (7.19 +/- 0.17 (stat.) +/- 0.24 (syst.))x 10 ^(-5). The eta pi0 invariant mass distributions have been fitted to obtain the relevant a0(980) parameters.
A proposal for maintaining CP conservation in $K_{L}^{0}$ decays is resumed, by adding a heterodox hypothesis. One recovers a consistent picture with a $2π$ $K_{L}^{0}$ decay branching ratio proportional to the vertical $K_{L}^{0}$ displacement. This can be clearly tested at the KLOE experiment, where important vertical $K_{L}^{0}$ displacements occur.
From a sample of about 10^9 Phi mesons produced at DAFNE, we have selected KL mesons tagged by observing KS->pi+pi- decays. We present results on the major KL branching ratios, including those of the semileptonic decays needed for the determination of Vus. These branching ratio measurements are fully inclusive with respect to final-state radiation. The KL lifetime has also been measured.
We present a measurement of the ratio R = Γ(\keg;\Estar>30\mev,\qstar>20^\circ)$/$Γ(\kegf)$ and a first measurement of the direct emission contribution in KL semileptonic decays. The measurement is done at the DAFNE phi-factory selecting phi->KL KS decays with the KLOE detector. We use 328 pb^{-1}$ of data corresponding to about 3.5 million Ke3(g) events and about 9000 radiative events. Our result is R=(924 +/- 23(stat) +/-16(syst)10^{-5} for the branching ratio and X=-2.3 +/- 1.3(stat) +/- 1.4(syst) for the parameter describing direct emission.
We present a precise measurement of the ratio R_K = Γ(Ke2(γ))/Γ(K\mu2(γ)) performed with the KLOE detector. The results are based on data collected at the Frascati e^+e^- collider DAFNE for an integrated luminosity of 2.2 fb^{-1}. We find R_K = (2.493\pm0.025_{stat}\pm0.019_{syst})\times 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 present a study of the reaction e+e- --> pi+pi-pi0 at the phi peak W=M(phi)=1019.4 MeV observed with the KLOE detector at Dafne. The reaction is dominated by phi production and decay, e+e- --> phi --> pi+pi-pi0. From a fit to the Dalitz plot density distribution we obtain the rho-meson parameters for its three charge states. We also find the relative amplitudes for phi --> rhopi and phi -> pi+pi-pi0 and the cross-section for e+e- --> omega pi0 with omega --> pi+pi-.
We present a measurement of the branching ratio of the CP violating decay KL->pi+pi- performed by the KLOE experiment at the phi factory DAFNE. We use 328 pb-1 of data collected in 2001 and 2002, corresponding to ~ 150 million tagged KL mesons. We find BR(KL->pi+pi-) = $(1.963 +/- 0.012 +/- 0.017)x 10^-3. This branching ratio measurement is fully inclusive of final-state radiation. Using the above result, we determine the modulus of the amplitude ratio |η_{+-}| to be (2.219 +/- 0.013)x 10^{-3} and |ε| to be (2.216 +/- 0.013)x 10^{-3}.
The KLOE experiment running at the phi-factory DAPHNE has collected ~ 450 pb^(-1) in the 2001--2002 data taking. We report preliminary results on light meson spectroscopy based on this data sample; particles are all produced through phi radiative decays. The nature of f0(980) and a0(980) is investigated by studying the shape of the resulting mass spectra, which is sensitive to their structure. A detailed study of the eta --> pi pi pi dynamics through a Dalitz plot analysis gives the possibility to extract information on the quark mass difference. Finally, the branching ratio for the eta --> pi…
A new measurement of the absolute branching ratio BR($K^\pm \to π^\pm π^0 π^0$) with the KLOE detector at the DA$Φ$NE $e^+e^-$ collider is presented, based on a sample of $\sim 3.3\times 10^7$ charged kaons tagged events, produced in the reaction $e^+e^-\toϕ\to K^+K^-$.The value BR($K^\pm \to π^\pm π^0 π^0$) $= (1.781\pm 0.013_{stat}\pm 0.016_{syst})%$ has been obtained.
We present results of a direct search for the decay KS --> e+e- with the KLOE detector, obtained with a sample of e+e- --> phi --> KSKL events produced at DAFNE, the Frascati phi-factory, for an integrated luminosity of 1.3fb-1. The Standard Model prediction for this decay is BR(KS --> e+e-) = 1.6*10^-15. The search has been performed tagging the KS decays by simultaneous detection of a KL interaction in the calorimeter. Background rejection has been optimized by using both kinematic cuts and particle identification. At the end of the analysis chain we find BR(KS --> e+e-) < 2.1*10^-8 at 90% C…
We present the measurement of the ratio R = \frac{Γ(\keg;\Estar>30\mev,\qstar>20^\circ)}{Γ(\kegf)} and a first measurement of the direct emission contribution for the same process. We use 328 pb^{-1} of data collected at \kloe in 2001 and 2002, corresponding to about 3 million of \kegf events and about 9 thousand \keg radiative events. Our result is R= (924 \pm 23_{stat} \pm 16_{syst})10^{-5} for the branching ratio and X =-2.3\pm 1.3_{stat}\pm 1.4_{syst} for the parameter describing direct emission.
Precise measurements of semileptonic kaon decay rates at KLOE provide the measurement of the CKM mixing matrix element \vus\ and information about lepton universality. Leptonic kaon decays provide an independent measurement of $\abs{\vus}^2/\abs{\vud}^2$, through the ratio $Γ(K\toμν)/Γ(π\toμν)$. These measurements, together with the result of $|\vud|$ from nuclear $β$ transitions, provide the most precise test of CKM unitarity, allowing the universality of lepton and quark weak couplings to be tested. After the completion of the KLOE data taking, the proposal of a new run with an upgraded KLOE…
We have searched with the KLOE detector for the P and CP violating decay eta -> pi^+pi^- in a sample of 1.55 x 10^7 eta's from the decay phi -> eta gamma of phi mesons produced in e+e- annihilations at DAFNE. No signal is found. We obtain the upper limit BR(eta -> pi^+pi^-) < 1.3 x 10^-5 at 90% confidence level.
Since april 1999, the KLOE experiment at DAFNE has collected about 200 inverse pb of data, produced in electron-positron collision at the c.m. energy of 1020 MeV, the mass of the phi meson. These data have been used for detailed studies on the phi radiative decays, as well as on rare K short decays. The first results, based on the 20 inverse pb collected in year 2000 are presented here
The $K_S \to 3 π^0$ decay is a pure CP violating process which, assuming CPT invariance, allows one to investigate direct CP violation. This decay has not been observed so far, and the best upper limit on the branching ratio $BR(K_S to 3π^0) < 1.2 \cdot 10^{-7}$ is two orders of magnitude larger than predictions based on the Standard Model: $BR(K_S \to 3π^0) \sim 2 \cdot 10^{-9}$. In this article we present the search for the $K_S \to 3π^0$ decay performed with the KLOE detector operating at the DAFNE Φ-factory at the Frascati Laboratory. We describe the analysis techniques used in the backgro…
We measured, with the KLOE detector, the spectrum of pi+pi- invariant mass in a sample of 6.7 x 10^5 e+e- --> pi+pi-g events with the photon at large polar angle (theta_g>45^o) at a centre of mass energy sqrt(s) around the phi mass. We observe a clear contribution from the intermediate process phi --> f0(980)g. A sizeable effect is also observed in the distribution of the forward-backeard asymmetry. We use different theoretical models to fit the spectrum and we determine the f_0 mass and coupling constants to the phi, to pi+pi- and to KK.
Using a sample of over 600 million phi->K+K- decays collected at the Dafne e+e- collider, we have measured with the KLOE detector the absolute branching ratios for the charged kaon semileptonic decays, K+/- -> p0 e nu (gamma) (Ke3) and K+/- -> p0 mu nu (gamma) (Kmu3). The results, BR(Ke3) = 0.04965 +/- 0.00038_{stat} +/- 0.00037_{syst} and BR(Kmu3) = 0.03233 +/- 0.00029_{stat} +/- 0.00026_{syst}, are inclusive of radiation. Accounting for correlations, we derive the ratio Kmu3/Ke3 = 0.6511+/-0.0064. Using the semileptonic form factors measured in the same experiment, we obtain V_{us}f_{+}(0) =…
The KLOE detector at DAFNE, the Frascati Phi-factory, has collected about 8 millions phi decays in 1999. Measurements of Phi decays into pi0, eta, eta', f0(980), a0(980) and pi+pi-pi0 have been performed with statistical accuracy better than previously in a single detector, as well as new decay modes. Phi radiative decays can clarify the nature of f0 and a0 (are they 4 quark states?) and measure the eta-eta' mixing angle. Analysis of Phi->pi+pi-pi0 allows us to extract the possible existence of direct decay in addition to the dominant rho-pi mode and to obtain a precise measurement of the rho …
The phi-meson leptonic widths, Gee and Gmm, are obtained, respectively, from the e+e- forward-backward asymmetry and the muon cross section around the phi-mass energy. We find Gee=1.32⊕0.05⊕0.03 kev and sqrt(GeeGmm)= 1.320⊕0.018⊕0.017 kev. These results, compatible with Gee=Gmm, provide a precise test of lepton universality. Combining the two results gives G_lept=1.320⊕0.023 kev.
The most precise determination of Vus comes from semileptonic kaon decays. The KLOE experiment at DA\PhiNE the Frascati ϕ-factory, has measured all the exeperimental inputs to Vus for both neutral and charged kaons. Preliminary results for BR(K^\pm\toπ^0 e^\pmν) and BR(K^\pm\toπ^0 μ^\pmν), and for τ_\pm are presented, together with measurements of the K_Le3 and K_L\mu3 decay BR, the K_Se3 decay BR and the K_L lifetime τ_L. From our results for the 5 braching ratios and τ_L we find Vus=0.2258\pm0.0022. We have also measured the fully inclusive K^+\mu2(γ) absolute branching ratio for which we ob…
We have searched for the C-violating decay eta to gamma gamma gamma in a sample of ~ 18 million eta mesons produced in phi to eta gamma decays, collected with the KLOE detector at the Frascati phi-factory DAFNE. No signal is observed and we obtain the upper limit BR(eta to gamma gamma gamma) less equal than 1.6x10^(-5) at 90 % C.L.
Kaon physics can test new-physics effects in leptonic or semileptonic decays. A unitarity test of the first row of the CKM mixing matrix is obtained from the precision measurements of Kl3 widths for K{\pm}, KL, and (unique to KLOE) KS. The KLOE measurement of RK = Γ(Ke2)/Γ(Kμ2) with an accuracy at the % level, aims at finding evidence of deviations from the SM prediction induced by lepton-flavor violation new-physics effects.
We present a measurement of the K-pi vector current form-factor parameters for the Ke3 decay. We use 328 pb$^{-1}$ of data collected in 2001 and 2002, corresponding to about 2 million Ke3 events. Measurements of semileptonic form factors provide information about the dynamics of the strong interaction and are necessary for evaluation of the phase-space integral Ie_K needed to measure the CKM matrix element Vus for Ke3 decays. Our result is $l=(28.6\pm0.5\pm0.4)10^{-3}$ for a linear fit, and $l'=(25.5\pm1.5\pm1.0)10^{-3}$, $l''=(1.4\pm0.7\pm0.4)10^{-3}$ for a quadratic fit.
This work presents prospects for conducting a novel direct test of time-reversal symmetry at the KLOE-2 experiment. Quantum entanglement of neutral K meson pairs uniquely available at KLOE-2 allows to probe directly the time-reversal symmetry (T) independently of CP violation. This is achieved by a comparison of probabilities for a transition between flavour and CP-definite states and its inverse obtained through exchange of initial and final states. As such a test requires the reconstruction of the $K_L\to 3π^0$ decay accompanied by $K_S\toπ^{\pm}\ell^{\mp}ν$ with good timing information, a n…
Among some 400 million KsKl pairs produced in e+e- annihilations at DAFNE, about 6500 each of Ks->pi+e-nubar and Ks->pi-e+nu decays have been observed with the KLOE detector. From these, the ratio G(Ks->pienu)/G(Ks->p+p-(g))=(10.19+-0.13)10-4 is obtained, improving the accuracy on BR(Ks->pienu) by a factor of four and providing the most precise test of the DeltaS=DeltaQ rule. From the partial width Gamma(Ks->pienu), a value for f+(K0)Vus is obtained that is in agreement with unitarity of the quark-mixing matrix. The lepton charge asymmetry AS=(1.5+-9.6stat+-2.9syst)10-3 is compatible with the …
The decay $η\rightarrow π^+ π^- π^0$ is studied with the KLOE detector, at the DA$ϕ$NE e$^+$e$^-$ collider. Using a data sample corresponding to an integrated luminosity of $1.6$ fb$^{-1}$ a new study of the Dalitz plot is presented.
We have analyzed 1.62 fb$^{-1}$ of $e^{+}e^{-}$ collisions at a center of mass energy $\sim M_ϕ$ collected by the KLOE experiment at DA$Φ$NE. This sample corresponds to a production of $\sim$ 1.7 billion of $\ks$ $\kl$ pairs which allowed us to search for the rare $K_S\to γγ$ decay. $K_S$ are tagged by the $K_L$ interaction in the calorimeter and the signal is searched for by requiring two additional prompt photons. Strong kinematic requirements reduce the initial 0.5$\times 10^6$ events to 2300 candidates from which we extract a signal of 600 $\pm$ 35 events. By normalizing to the $\ks \to 2 …
While measuring the ratio R_K = Γ(K+e2(γ))/Γ(K+\mu2(γ)), the KLOE Collaboration has studied the radiative process Ke2γ. The ratio of the width for the Ke2γdecay with a positively polarized photon from structure-dependent radiation to the inclusive K\mu2(γ) width is found to be 1.484(68) 10-5. The observed radiation spectrum agrees with predictions from chiral perturbation theory and is in contrast with predictions based on the light front quark model. This result reduces the contribution to systematic uncertainties on measurements of R_K. In a separate study, KLOE has measured the ratio of the…
The most recent results from the KLOE experiment are presented, covering: the measurement of the running fine-structure constant alpha_em,the Dalitz plot measurement of eta to pi+pi-pi0, the search of a U boson, tests of discrete symmetries and quantum coherence. The KLOE-2 Collaboration will take data until mid 2018 aiming to collect 5 inversed fb increasing the data set, in order to produce new precision measurements and continue studies of fundamental symmetries and New Physics.
The most precise determination of Vus comes from semileptonic kaon decays. We have measured with the KLOE detector at DAFNE, the Frascati phi-factory, all the experimental inputs to Vus for both neutral and charged kaons. Using our results we extract the value of Vus with about 0.9% fractional error, which is entirely dominated by the theoretical error on the knowledge of the normalization of the decay form factors, f0. A new determination of the ratio Vus/Vud is also presented, based on our precise measurement of the absolute branching ratio for the decay K+ -> mu+nu, combined with recent lat…
We present a new search for the $K_S \to 3π^0$ decay performed with the KLOE detector operating at the DA$Φ$NE $ϕ$--factory. The $K_S$ mesons were tagged via registration of $K_L$ mesons which crossed the drift chamber without decaying and interacted with the KLOE electromagnetic calorimeter. The $K_S \to 3π^0$ decay was then searched requiring six prompt photons. To suppress background, originating from fake $K_S$ tags and $K_S \to 2π^0$ decays with additional two spurious clusters, we have performed a discriminant analysis based on kinematical fit, testing of the signal and background hypoth…
All relevant inputs for the extraction of the CKM matrix element \vus from \kl, \ks and \kpm decays have been measured at KLOE. From a global fit using only KLOE results, but \ks lifetime, a value of $|\vus|\fzero = 0.2157 \pm 0.0006$ is obtained, where \fzero is the form factor parametrizing the hadronic matrix element evaluated at zero momentum transfer. Comparison of the values of \fVus for $K_{e3}$ and $K_{\mu3}$ modes provides a test of lepton universality at 0.8% level of accuracy. The value $\vus/\vud=0.2323(15)$ has been obtained from the ratio $Γ(K\toμν)/Γ(π\toμν)$ using KLOE measurem…
We describe the status of the analyses in progress on light meson spectroscopy in the KLOE experiment. We present the analyses of phi decays into f0(980)gamma and a0(980)gamma, the Dalitz plot analysis of the eta to pie+ pie- pie0 decay, the branching ratio measurement of eta to pie0 gamma gamma, the upper limits on Br(eta to 3 gamma) and Br(eta to pie^+ pie^-), the measurement of the ratio Br(phi to eta' gamma)/Br(phi to eta gamma) and phi leptonic width measurements.
In this paper we discuss the recent finalized analyses by the KLOE experiment at DA$Φ$NE: the CPT and Lorentz invariance test with entangled $K^0 \bar{K}^0$ pairs, and the precision measurement of the branching fraction of the decay ${ K^+} \rightarrow π^+π^-π^+(γ)$. We also present the status of an ongoing analysis aiming to precisely measure the $K^{\pm} $ mass.
We have searched for the decay KS->gg in a sample of 2x10^9 phi->KS KL decays collected at DAPHNE with an integrated luminosity of 1.9 fb^{-1}. KS are tagged by the KL interaction in the calorimeter. Two prompt photons must also be detected. Kinematic constraints reduce the initial 6x10^5 events to 2740 candidates, from which a signal of 711\pm 35 events is extracted. By normalizing to the KS->2pi^0 decays counted in the same sample, we measure BR(KS->gg)= (2.26\pm0.12_{stat}\pm0.06_{syst})x10^{-6}, in agreement with O(p^4) Chiral Perturbation Theory predictions.
Using 1.63 fb$^{-1}$ of integrated luminosity collected by the KLOE experiment about $7\times 10^4$ $K_S \rightarrow π^{\pm}e^{\mp}ν$ decays have been reconstructed. The measured value of the charge asymmetry for this decay is $A_S = (-4.9 \pm 5.7_{stat} \pm 2.6_{syst}) \times 10^{-3}$, which is almost twice more precise than the previous KLOE result. The combination of these two measurements gives $A_S = (-3.8 \pm 5.0_{stat} \pm 2.6_{syst}) \times 10^{-3}$ and, together with the asymmetry of the $K_L$ semileptonic decay, provides significant tests of the CPT symmetry. The obtained results are…
The basic motivation of the KLOE-2 experiment is the test of fundamental symmetries and Quantum Mechanics coherence of the neutral kaon system, and the search for phenomena beyond the Standard Model in the hadronic and leptonic decays of ground-state mesons. Perspectives for experimentation by means of the KLOE-2 apparatus equipped with the inner tracker, new scintillation calorimeters, and the gamma-gamma taggers at the DA\$Phi$NE electron-positron collider upgraded in luminosity and energy are presented.
Recent results from the KLOE experiment at the DAPHNE e+e- collider are presented. KLOE has collected about 500 pb^-1 of data in the years from 2000 to 2002. Preliminary results are obtained using wide samples of the full statistics and include: the BR of the Ke3 decay of the K_S and the first measurement of its charge asymmetry, the ratio BR(K_S-->pi+pi-(gamma))/BR(K_S-->pi^0pi^0), the ratio BR(K_L-->gammagamma)/BR(K_L-->3pi^0), a detailed study of the decay phi-->pi+pi-pi^0, the ratio BR(phi-->eta' gamma)/BR(phi-->eta gamma) and the pseudoscalar mixing angle phi_P, the phi-->f_0 gamma and th…
The most precise determination of Vus comes from semileptonic kaon decays. We have measured with the KLOE detector at DAFNE, the Frascati phi-factory, all the experimental inputs to Vus for both neutral and charged kaons. Using our results we extract the value of Vus with ~0.9% fractional error, which is dominated by the theoretical error on the form factor, f+(0). A new determination of the ratio Vus/Vud is also presented, based on our precise measurement of the absolute branching ratio for the decay K -> mu nu (gamma), combined with lattice results for the ratio f_K/f_pi. New results on CPT …
We have searched for the decay phi -> K0 K0bar gamma, by detecting K_s pairs plus a photon and with the K_s-mesons decaying to pi^+ pi^-, in a sample of about 1.5x 10^9 phi-decays collected by the KLOE experiment at DAFNE. The reaction proceeds through the intermediate states f_0(980) gamma, a_0(980) gamma. We find five events with 3.2 events expected from background processes. We obtain the upper limit: BR (phi -> K0 K0bar gamma) < 1.9x10^-8 at 90% C.L. .
