287 research outputs found
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 1.8
million decays, we have measured the form factor
parameters. The structure of the 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 and for testing lepton universality in kaon decays. Using a
new parametrization for the vector and scalar form factors, we find
=\pt(25.7\pm 0.6),-3, and =\pt(14.0\pm 2.1),-3,. Our
result for , together with recent lattice calculations of ,
and , 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
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