arXiv subjects

F. Ambrosino

Publications and source records attributed to F. Ambrosino.

At least 73 records · Page 4Linked to original sources

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.

hep-ex↗

arXiv2008

Measurement of the absolute branching ratio of the K+ -> pi+ pi0 (gamma) decay with the KLOE detector

We have measured the absolute branching ratio of the K+ -> pi+ pi0 (gamma) decay, using about 20 million tagged K+ mesons collected with the KLOE detector at DAFNE, the Frascati phi-factory. Signal counts are obtained from the fit of the distribution of the momentum of the charged decay particle in the kaon rest frame. The result, inclusive of final-state radiation, is BR(K+ -> pi+ pi0 (gamma))=0.2065+/-0.0005_{stat}+/- 0.0008_{syst}.

hep-ex↗

arXiv2008

Study of the process e+e- -> omega pi0 in the phi-meson mass region with the KLOE detector

We have studied the e+e- -> omegapi0 cross section in the sqrt(s) interval 1000-1030 MeV using the pi+pi-pi0pi0 and pi0pi0gamma final states with a sample of ~600 pb^-1 collected with the KLOE detector at DAFNE. By fitting the observed interference pattern around M_phi for both final states, we extract the ratio of the decay widths Gamma(omega->pi0gamma)/Gamma(omega->pi+pi-pi0) = 0.0897 +- 0.0016 and derive the branching fractions BR(omega -> pi+pi-pi0)= (90.24 +- 0.19)%, BR(omega -> pi0gamma) = (8.09 +- 0.14)%. The parameters describing the e+e- -> omegapi0 reaction around M_ϕare also used to extract the branching fraction for the OZI and G-parity violating phi -> omegapi0 decay: BR(phi->omegapi0) = (4.4 +- 0.6)x10^-5.

hep-ex↗

arXiv2008

Study of the process e+e- -> omega p0 with the KLOE detector

Using ~600 pb-1 collected with the KLOE detector at DAPhiNE, we have studied the production cross section of pi+ pi- pi0 pi0 and p0p0 gamma final states in e+e- collisions at center of mass energies between 1000 and 1030 MeV. By fitting the observed interference pattern around Mphi for both final states, we extract a measurement (preliminary) for the ratio Gamma(omega -> pi0 gamma)/Gamma(omega -> pi+ pi- pi0) = 0.0934 +- 0.0022. Since these two final states represent the 98% of the omega decay channels, we use unitarity to derive BR(omega -> pi+pi-pi0)= (89.94 +- 0.23)% and BR(omega -> pi0 gamma) = (8.40 +- 0.19)%. Moreover, the parameters describing the e+e- -> pi+ pi- pi0 pi0 reaction around Mphi are used to extract the branching fraction for the OZI and G-parity violating phi -> omega pi0 decay: BR(phi -> omega pi0) = (5.63 +- 0.70) x 10^-5.

hep-ex↗

arXiv2008

Recent results from KLOE experiment

We report the newest results from the KLOE experiment on hadronic physics, such as the parameters of scalars f0 and a0, the eta meson mass measurements and dynamics, the first observation of the eta -> p+p-e+e- rare decay, and study of e+e- -> omega p0 cross section around the phi resonance.

hep-ph↗

arXiv2008

Determination of $η\toπ^+π^-π^0$ Dalitz plot slopes and asymmetries with the KLOE detector

We have studied, with the KLOE detector at the DA$Φ$NE $Φ$-Factory, the dynamics of the decay $η\toπ^+π^-π^0$ using $η$ mesons from the decay $ϕ\toηγ$ for an integrated luminosity ${\mathcal L}$ = 450 pb$^{-1}$. From a fit to the Dalitz plot density distribution we obtain a precise measurement of the slope parameters. An alternative parametrization relates the $π^+π^-π^0$ slopes to that for $η\to 3π^0$ showing the consistency of KLOE results for both channels. We also obtain the best confirmation of the $C$-invariance in the $η\toπ^+π^-π^0$ decay.

hep-ex↗

arXiv2008

Vus and lepton universality from kaon decays with the KLOE detector

KLOE has measured most decay branching ratios of Ks, Kl and K+/- mesons. It has also measured the Kl and the K+- lifetime and determined the shape of the form factors involved in kaon semileptonic decays. We present in the following a description of the above measurements and a well organized compendium of all of our data, with particular attention to correlations. These data provide the basis for the determination of the CKM parameter Vus and a test of the unitarity of the quark flavor mixing matrix. We also test lepton universality and place bounds on new physics using measurements of Vus from Kl2 and Kl3 decays.

hep-ex↗

arXiv2008

Measurement of the charged kaon lifetime with the KLOE detector

We have measured the charged kaon lifetime using a sample of 15 \times 10^6 tagged kaon decays. Charged kaons were produced in pairs at the DA\PhiNE ϕ-factory, e^+e^- \to ϕ\to K^+ K^-. The decay of a K^+ was tagged by the production of a K^- and viceversa. The lifetime was obtained, for both charges, from independent measurements of the decay time and decay lenght distributions. From fits to the four distributions we find τ= (12.347\pm0.030) ns.

hep-ex↗

arXiv2007

A prototype large-angle photon veto detector for the P326 experiment at CERN

The P326 experiment at the CERN SPS has been proposed with the purpose of measuring the branching ratio for the decay K^+ \to π^+ ν\barν to within 10%. The photon veto system must provide a rejection factor of 10^8 for π^0 decays. We have explored two designs for the large-angle veto detectors, one based on scintillating tiles and the other using scintillating fibers. We have constructed a prototype module based on the fiber solution and evaluated its performance using low-energy electron beams from the Frascati Beam-Test Facility. For comparison, we have also tested a tile prototype constructed for the CKM experiment, as well as lead-glass modules from the OPAL electromagnetic barrel calorimeter. We present results on the linearity, energy resolution, and time resolution obtained with the fiber prototype, and compare the detection efficiency for electrons obtained with all three instruments.

physics.ins-det↗

arXiv2007

Precise measurements of the eta and the neutral kaon meson masses with the KLOE detector

We present precise measurements of the eta and K0 masses using the processes phi to eta gamma, eta to gamma gamma and phi to Ks Kl, Ks to pi+ pi-. The K0 mass measurement, M_K=497.583 +/- 0.005 (stat) +/- 0.020 (syst) MeV, is in acceptable agreement with the previous measurements but is more accurate. We find m(eta) = 547.874 +/- 0.007 (stat) +/- 0.031 (syst) MeV. Our value is the most accurate to date and is in agreement with two recent measurements based on eta decays, but is inconsistent, by about 10 sigma, with a measurement of comparable precision based on eta production at threshold.

hep-ex↗

arXiv2007

Measurement of the slope parameter αfor the η\to 3π^0 decay at KLOE

We report a preliminary measurement of the slope parameter $α$ for the $η\to 3\piz$ decay carried out with KLOE at DA$Φ$NE; where $α$ is the parameter describing the energy dependence of the square of the matrix element for this decay. By fitting the event density in the Dalitz plot with a collected statistic of 420 pb$^{-1}$ we determine $α= -0.027 \pm 0.004 (stat) ^{+0.004}_{-0.006} (syst)$. This result is consistent with current chiral perturbation theory calculations within the unitary approach.

hep-ex↗

arXiv2007

Determination of the η\toπ^+π^-π^0 Dalitz Plot slopes and asymmetries with the KLOE detector

We have studied, with the KLOE detector at the DA$Φ$NE $Φ$-Factory, the dynamics of the decay $η\toπ^+π^-π^0$ using data from the radiative $ϕ\toηγ$ decay for an integrated luminosity $L = 450 \textrm{pb^{-1}}$. From a fit to the Dalitz plot density distribution we obtain a precise measurement of the slope parameters. This should allow to improve the knowledge of the decay amplitude which is sensitive to the u-d quark mass difference. We also present new best results on the C-violating asymmetries in the $η\toπ^+π^-π^0$ decay.

hep-ex↗

arXiv2007

Measurement of the pseudoscalar mixing angle and $η^{\prime}$ gluonium content with KLOE detector

We have measured the ratio $R_ϕ=BR(ϕ\to η^{\prime} γ)/BR(ϕ\to ηγ)$ by looking for the radiative decays $ϕ\to η^{\prime} γ$ and $ϕ\to ηγ$ in the final states $π^+π^-$ 7 $γ$'s and 7 $γ$'s respectively, in a sample of $\sim 1.3\cdot 10^{9}$ $ϕ$ mesons produced at the Frascati $ϕ$-factory. We obtain $R_ϕ=(4.77\pm0.09_{stat}\pm0.19_{sys})\cdot 10^{-3}$ from which we derive $BR(ϕ\to η^{\prime} γ)=(6.20\pm0.11_{stat}\pm0.25_{sys})\cdot 10^{-5}$. In the hypothesis of no gluonium content we extract the pseudoscalar mixing angle in the quark-flavor basis $ϕ_P=(41.4\pm0.3_{stat}\pm0.7_{sys}\pm0.6_{th})^{\circ}$. Combining the value of $R_ϕ$ with other constraints, we estimate the gluonium fractional content of $η^{\prime}$ meson as $Z^2 = 0.14\pm0.04$ and the mixing angle $ϕ_P = (39.7\pm0.7)^{\circ}$.

hep-ex↗

arXiv2007

Search for the K(S) --> e+e- decay with the KLOE detector at DAFNE

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% CL, which improves by a factor of ~7 on the previous best result, obtained by CPLEAR experiment.

hep-ex↗

arXiv2007

Charged kaon lifetime at KLOE

Preliminary result on the charged kaon lifetime, obtained by the KLOE experiment operating at DA$Φ$NE, the Frascati $ϕ$-factory, is presented

hep-ex↗

arXiv2007

eta Physics and phi Radiative Decays at Kloe

Here we present KLOE results on the phi meson decays in pi0 pi0 gamma, pi+ pi- gamma and eta pi0 gamma, the measurement of the ratio Br(phi to eta' gamma)/Br(phi to eta gamma) with the estimate of the eta' gluonium content and the measurement of the eta mass.

hep-ex↗

arXiv2007

Prospects for e+e- physics at Frascati between the phi and the psi

We present a detailed study, done in the framework of the INFN 2006 Roadmap, of the prospects for e+e- physics at the Frascati National Laboratories. The physics case for an e+e- collider running at high luminosity at the phi resonance energy and also reaching a maximum center of mass energy of 2.5 GeV is discussed, together with the specific aspects of a very high luminosity tau-charm factory. Subjects connected to Kaon decay physics are not discussed here, being part of another INFN Roadmap working group. The significance of the project and the impact on INFN are also discussed. All the documentation related to the activities of the working group can be found in http://www.roma1.infn.it/people/bini/roadmap.html.

hep-ex↗

arXiv2006

Measurement of the Form-Factor Slopes for the Decay KLe3 with the KLOE Detector

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.

hep-ex↗