A search for directional violations of the Lorentz invariance through the study of a possible anisotropy of particle lifetimes

From the study of a sample of about 62.3 million well-reconstructed K0S → π+π− decays recorded by the KLOE detector at the DAΦNE accelerator in Frascati, the lifetimes of K0S mesons parallel and antiparallel to the direction of motion of the Earth with respect to the Cosmic Microwave Background (CMB) reference frame have been studied. No difference has been found, and a limit on a possible asymmetry of the lifetime with respect to the CMB has been set at 95% CL: |A|CMB = |τ+CMB − τ−CMB|/(τ+CMB + τ−CMB) < 0.98×10−3. This is presently the best experimental limit on such quantity, and it is smaller of the speed, expressed in natural units, of the Solar System with respect to the CMB (V/c = 1.23×10−3). The present limit might constrain possible Lorentz-violating anisotropical theories

The Extreme Energy Events HECR array: status and perspectives

The Extreme Energy Events Project is a synchronous sparse array of 52 tracking detectors for studying High Energy Cosmic Rays (HECR) and Cosmic Rays-related phenomena. The observatory is also meant to address Long Distance Correlation (LDC) phenomena: the network is deployed over a broad area covering 10 degrees in latitude and 11 in longitude. An overview of a set of preliminary results is given, extending from the study of local muon flux dependance on solar activity to the investigation of the upward-going component of muon flux traversing the EEE stations; from the search for anisotropies at the sub-TeV scale to the hints for observations of km-scale Extensive Air Shower (EAS).Comment: XXV ECRS 2016 Proceedings - eConf C16-09-04.

A global fit to determine the pseudoscalar mixing angle and the gluonium content of the eta' meson

We update the values of the eta-eta' mixing angle and of the eta' gluonium content by fitting our measurement R_phi = BR(phi to eta' gamma)/ BR(phi to eta gamma) together with several vector meson radiative decays to pseudoscalars (V to P gamma), pseudoscalar mesons radiative decays to vectors (P to V gamma) and the eta' to gamma gamma, pi^0 to gamma gamma widths. From the fit we extract a gluonium fraction of Z^2_G = 0.12 +- 0.04, the pseudoscalar mixing angle psi_P = (40.4 +- 0.6) degree and the phi-omega mixing angle psi_V = (3.32 +- 0.09) degree. Z^2_G and psi_P are fairly consistent with those previously published. We also evaluate the impact on the eta' gluonium content determination of future experimental improvements of the eta' branching ratios and decay width.Comment: 13 pages, 7 figures to submit to JHE

Precision Measurement of KS Meson Lifetime with the KLOE detector

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.Comment: 5 pages, 7 figure

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.Comment: 17 pages, 6 figures, submitted to Physics Letters B. Corrected typos in eq.

Measurement of the K_L \to \pi\mu\nu form factor parameters with the KLOE detector

Using 328 pb^{-1}of data collected at DAFNE corresponding to $\sim$ 1.8 million $K_L\to \pi\mu\nu$ decays, we have measured the $K_{\mu 3}$ form factor parameters. The structure of the $K-\pi$ 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 $\lambda_+$=\pt(25.7\pm 0.6),-3, and $\lambda_0$=\pt(14.0\pm 2.1),-3,. Our result for $\lambda_0$, together with recent lattice calculations of $f_\pi$, $f_K$ and $f(0)$, satisfies the Callan-Trieman relatio

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_\phi are 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.Comment: 12 Pages, 4 figures, submitted to Physics Letter

Search for the K_S -> e+e- decay with the KLOE detector

We present the result of a direct search for the decay K_S -> e+e-, obtained with a sample of e+e- -> phi -> K_S K_L events produced at DAFNE, the Frascati phi-factory, for an integrated luminosity of 1.9 fb^-1. The search has been performed using a pure K_S beam tagged by the simultaneous detection of a K_L interaction in the calorimeter. Background rejection has been optimized by using both kinematic and particle identification cuts. We find BR(K_S -> e+e-) < 9x10^-9 at 90% CL, which improves by an order of magnitude on the previous best limit.Comment: 13 pages, 11 figures, submitted to Physics Letters