arXiv subjects

KLOE Collaboration

Publications and source records attributed to KLOE Collaboration.

At least 19 recordsLinked to original sources

arXiv2011

Measurement of sigma(e+ e- -> pi+ pi-) from threshold to 0.85 GeV^2 using Initial State Radiation with the KLOE detector

We have measured the cross section of the radiative process e+e- -> pi+pi-gamma with the KLOE detector at the Frascati phi-factory DAPHNE, from events taken at a CM energy W=1 GeV. Initial state radiation allows us to obtain the cross section for e+e- -> pi+pi-, the pion form factor |F_pi|^2 and the dipion contribution to the muon magnetic moment anomaly, Delta a_mu^{pipi} = (478.5+-2.0_{stat}+-5.0_{syst}+-4.5_{th}) x 10^{-10} in the range 0.1 < M_{pipi}^2 < 0.85 GeV^2, where the theoretical error includes a SU(3) ChPT estimate of the uncertainty on photon radiation from the final pions. The discrepancy between the Standard Model evaluation of a_mu and the value measured by the Muon g-2 collaboration at BNL is confirmed.

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arXiv2009

Test of lepton flavor violation with Ke2 decay at KLOE

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.

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arXiv2009

Search for the decay phi -> K0 K0bar gamma with the KLOE experiment

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. .

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arXiv2009

Measurement of the branching ratio and search for a CP violating asymmetry in the eta -> pi+pi-e+e-(gamma) decay at KLOE

We have studied the eta->pi+pi-e+e-(gamma) decay using about 1.7 fb^-1 collected by the KLOE experiment at the DAFNE phi-factory. This corresponds to about 72 millions eta mesons produced in phi radiative decays. We have measured the branching ratio, inclusive of radiative effects, with 4% accuracy: BR(eta->pi+pi-e+e-(gamma)) = (26.8 +/- 0.9_Stat. +/- 0.7_Syst.) x 10^-5. We have obtained the first measurement of the CP-odd pipi-ee decay planes angular asymmetry, A_phi = (-0.6 +/- 2.5_Stat. +/- 1.8_Syst.) x 10^-2.

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arXiv2009

Study of the a_0(980) meson via the radiative decay phi->eta pi^0 gamma with the KLOE detector

We have studied the phi->a_0(980) gamma process with the KLOE detector at the Frascati phi-factory DAPhNE by detecting the phi->eta pi^0 gamma decays in the final states with eta->gamma gamma and eta->pi^+ pi^- pi^0. We have measured the branching ratios for both final states: Br(phi->eta pi^0 gamma)=(7.01 +/- 0.10 +/- 0.20)x10^-5 and (7.12 +/- 0.13 +/- 0.22)x10^-5 respectively. We have also extracted the a_0(980) mass and its couplings to eta pi^0, K^+ K^-, and to the phi meson from the fit of the eta pi^0 invariant mass distributions using different phenomenological models.

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arXiv2008

Measurement of $σ(e^+e^-\toπ^+π^-γ(γ))$ and the dipion contribution to the muon anomaly with the KLOE detector

We have measured the cross section $σ(e^+e^-\toπ^+π^-γ(γ))$ at DA$Φ$NE, the Frascati ϕ-factory, using events with initial state radiation photons emitted at small angle and inclusive of final state radiation. We present the analysis of a new data set corresponding to an integrated luminosity of 240 pb$^{-1}$. We have achieved a reduced systematic uncertainty with respect to previously published KLOE results. From the cross section we obtain the pion form factor and the contribution to the muon magnetic anomaly from two pion states in the mass range $0.592 < M_{ππ} < 0.975$ GeV. For the latter we find $Δa^{ππ}_μ= (387.2\pm0.5_{\rm stat}\pm2.4_{\rm exp}\pm2.3_{\rm th})\times 10^{-10}$

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arXiv2008

Recent results from KLOE

In this report I will present the recent results on K mesons from the KLOE experiment at the DAFNE e+e- collider working at the center of mass energy ~1GeV ~m_{phi}. They include V_{us} determinations, the test on the unitarity of the first row of the CKM matrix and the related experimental measurements. Tests of lepton universality from leptonic and semileptonic decays will be also discussed. Then I will present tests of quantum coherence, CPT and Lorentz symmetry performed by studying the time evolution of the neutral kaon system.

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arXiv2008

Measurement of the absolute branching ratios for semileptonic K+/- decays with the KLOE detector

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) = 0.2141 +/- 0.0013.

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arXiv2007

Measurement of the K_L \to πμνform factor parameters with the KLOE detector

Using 328 pb^{-1}of data collected at DAFNE corresponding to $\sim$ 1.8 million $K_L\to πμν$ decays, we have measured the $K_{μ3}$ form factor parameters. The structure of the $K-π$ vector-current provides information about the dynamics of the strong interaction; its knowledge is necessary for evaluation of the phase-space integral required for measuring the CKM matrix element $V_{us}$ and for testing lepton universality in kaon decays. Using a new parametrization for the vector and scalar form factors, we find $λ_+$=\pt(25.7\pm 0.6),-3, and $λ_0$=\pt(14.0\pm 2.1),-3,. Our result for $λ_0$, together with recent lattice calculations of $f_π$, $f_K$ and $f(0)$, satisfies the Callan-Trieman relation

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arXiv2007

Measurements of the form-factors slopes of KL -> pi mu nu decay with the KLOE Detector

We present a measurement of the K-$π$ form-factor parameters for the decay \klpmn. We use 328 pb^{-1} of data collected in 2001 and 2002, corresponding to $\sim $ 1.8 million \semil 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 $I^μ_K$ needed to measure the CKM matrix element $|V_{us}|$ for \klpmn decays and to test lepton universality in kaon decays. Using a new parameterization for the vector and scalar form factors we find $λ_+$=\pt(25.6\pm 0.4_{\rm{stat.}}\pm 0.3_{\rm{syst.}}),-3, and $λ_0$=\pt(14.3\pm 1.7_{\rm{stat.}}\pm 1.1_{\rm{stat.}}),-3,. In the more usual quadratic expansion of the form factor the above result is corresponds to $λ'_+=λ_+$, $λ''_+=2λ^2_+$, $λ'_0=λ_0$ and $λ''_0=(λ^2_0+0.000416)/2$. Our results, together with recent lattice calculations of $f_π$, $f_K$ and $f(0)$, satisfy the Callan-Trieman relation.

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arXiv2007

New results from KLOE

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 symmetry and quantum mechanics test have also been achieved, which are based on the first measurement of the charged asymmetry for KS -> pi e nu decay and on interferometry studies using the phi -> KL KS -> pi+ pi- pi+ pi-.

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arXiv2006

Dalitz plot analysis of e+ e- --> pi0 pi0 gamma events at SQRT(s) ~ M(phi) with the KLOE detector

We have studied the Dalitz plot of the e+ e- --> pi0 pi0 gamma events collected at SQRT(s) ~ M(phi) with the KLOE detector. In the dipion invariant mass (Mpp) region below 700 MeV, the process under study is dominated by the non-resonant process e+ e- --> omega pi0 with omega --> pi0 gamma whereas, for higher Mpp values, the radiative phi decay to the f0(980) is the dominant mechanism. Different theoretical models are used to fit the Dalitz plot, taking also into account a possible contribution of the sigma(600). For each model, we extract the f0(980) mass and its coupling to pipi, KKbar and to the phi.

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arXiv2006

CP and CPT tests with the KLOE detector

Neutral kaons provide one of the most sensitive system to CP and CPT violation. Tests on CP, CPT and quantum mechanics have been performed at KLOE operating at the DAFNE e+e- collider. Results on the quantum interference in the channel phi-> KSKL ->pi+pi-pi+pi-, the measurement of the BR(KL ->pi+pi-) and the related CP violating parameter epsilon are presented. Using the Bell-Steinberger relation, CPT violating parameters have been also obtained

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arXiv2006

Measurement of the DA$Φ$NE luminosity with the KLOE detector using large angle Bhabha scattering

We describe the method of measuring the integrated luminosity of the $e^+e^-$ collider DA$Φ$NE, 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 $e^+e^- \to e^+e^-(γ)$ cross section is calculated using different event generators which account for the $O(α)$ 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.

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arXiv2005

Measurement of the Absolute Branching Ratio for the K+ -> mu+ nu(gamma) Decay with the KLOE Detector

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.

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arXiv2005

Measurements of the Absolute Branching Ratios for the Dominant KL Decays, the KL Lifetime, and Vus with the KLOE Detector

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.

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arXiv2005

KLOE results on f0(980), a0(980) scalars and eta decays

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 --> pi0 gamma gamma decay is compared with previous measurements and with the expectations from Chiral Perturbation Theory.

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arXiv2005

Study of the decay phi --> pi+pi-pi0 with the KLOE detector

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-.

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