A search for high-energy neutrinos coming from the direction of the Sun has been performed using the data recorded by the ANTARES neutrino telescope during 2007 and 2008. The neutrino selection ...criteria have been chosen to maximize the selection of possible signals produced by the self-annihilation of weakly interacting massive particles accumulated in the centre of the Sun with respect to the atmospheric background. After data unblinding, the number of neutrinos observed towards the Sun was found to be compatible with background expectations. The $90\%$ CL upper limits in terms of spin-dependent and spin-independent WIMP-proton cross-sections are derived and compared to predictions of two supersymmetric models, CMSSM and MSSM-7. The ANTARES limits are competitive with those obtained by other neutrino observatories and are more stringent than those obtained by direct search experiments for the spin-dependent WIMP-proton cross-section.
The quantum interference between the decays of entangled neutral kaons is studied in the process \(\phi\rightarrow K_S K_L \rightarrow\pi^+\pi^-\pi^+\pi^-\), which exhibits the characteristic ...Einstein--Podolsky--Rosen correlations that prevent both kaons to decay into \(\pi^+\pi^-\) at the same time. This constitutes a very powerful tool for testing at the utmost precision the quantum coherence of the entangled kaon pair state, and to search for tiny decoherence and CPT violation effects, which may be justified in a quantum gravity framework. The analysed data sample was collected with the KLOE detector at DA\(\Phi\)NE, the Frascati \(\phi\)-factory, and corresponds to an integrated luminosity of about 1.7 fb\(^{-1}\), i.e. to about \(1.7 \times 10^9\) \(\phi\rightarrow K_S K_L\) decays produced. From the fit of the observed \(\Delta t\) distribution, being \(\Delta t\) the difference of the kaon decay times, the decoherence and CPT violation parameters of various phenomenological models are measured with a largely improved accuracy with respect to previous analyses. The results are consistent with no deviation from quantum mechanics and CPT symmetry, while for some parameters the precision reaches the interesting level at which -- in the most optimistic scenarios -- quantum gravity effects might show up. They provide the most stringent limits up to date on the considered models.
J. High Energ. Phys. 2020, 47 (2020) Based on an integrated luminosity of 1.61 fb$^{-1}$ $e^+e^-$ collision data
collected with the KLOE detector at DA$\Phi$NE, the Frascati $\phi$-factory, a
search ...for the $P$- and $CP$-violating decay $\eta\to\pi^{+}\pi^{-}$ has been
performed. Radiative $\phi\to\eta\gamma$ decay is exploited to access the
$\eta$ mesons. No signal is observed in the $\pi^{+}\pi^{-}$ invariant mass
spectrum, and the upper limit on the branching fraction at 90\% confidence
level is determined to be ${\mathcal
B}(\eta\to\pi^{+}\pi^{-})<4.9\times10^{-6}$, which is approximately three times
smaller than the previous KLOE result. From the combination of these two
measurements we get ${\mathcal B}(\eta\to\pi^{+}\pi^{-}) < 4.4\times10^{-6}$ at
90\% confidence level.
Based on a sample of 300 million $K_S$ mesons produced in $\phi \to K_L K_S$
decays recorded by the KLOE experiment at the DA$\Phi$NE $e^+e^-$ collider we
have measured the branching fraction for the ...decay $K_S \to \pi \mu \nu$. The
$K_S$ mesons are identified by the interaction of $K_L$ mesons in the detector.
The $K_S \to \pi \mu \nu$ decays are selected by a boosted decision tree built
with kinematic variables and by a time-of-flight measurement. Signal
efficiencies are evaluated with data control samples of $K_L \to \pi \mu \nu$
decays. A fit to the reconstructed muon mass distribution finds $7223 \pm 180$
signal events. Normalising to the $K_S \to \pi^+ \pi^-$ decay events the result
for the branching fraction is $\mathcal{B}(K_S \to \pi \mu \nu) = (4.56 \pm
0.11_{\rm stat} \pm 0.17_{\rm syst})\times10^{-4}$.
Eur.Phys.J. C79 (2019) no.3, 190 The determination of low-energy cross sections and branching ratios of the
K$^-$ multi-nucleon absorption processes in $\Lambda$p and $\Sigma^0$p final
states ...performed by the AMADEUS collaboration is presented. Low momentum K$^-$
($p_\mathrm{K} \simeq$ 127 MeV/c) produced at the DA$\Phi$NE collider are
impinged on a Carbon target within the KLOE detector and the two and three
nucleon absorption processes are disentangled by comparing the experimental
data to phenomenological calculations. The $\Lambda$p spectra are interpreted
in terms of K$^-$ multi-nucleon absorption processes; the possible contribution
of a K$^-$pp bound state is demonstrated to overlap with the two nucleon
capture process, its absolute yield thus resulting indistinguishable.
Physics Letters B 784 (2018), 336 We searched for the $\mu^+\mu^-$ decay of a light vector gauge boson, also
known as dark photon, in the $e^+ e^- \to \mu^+ \mu^- \gamma_{\rm ISR}$ process
by means ...of the Initial State Radiation (ISR) method. We used 1.93~fb$^{-1}$ of
data collected by the KLOE experiment at the DA$\Phi$NE $\phi$-factory. No
structures have been observed over the irreducible $\mu^+ \mu^-$ background. A
90\% CL limit on the ratio $\varepsilon^2=\alpha^{\prime}/\alpha$ between the
dark coupling constant and the fine structure constant of $ 3\times
10^{-6}-2\times 10^{-7}$ has been set in the dark photon mass region between
519 MeV and 973 MeV. This new limit has been combined with the published result
obtained investigating the hypothesis of the dark photon decaying into hadrons
in $e^+ e^- \to \pi^+ \pi^- \gamma_{\rm ISR}$ events. The combined 90\% CL
limit increases the sensitivity especially in the $\rho-\omega$ interference
region and excludes $\varepsilon^2$ greater than $(13-2)\times 10^{-7}$. For
dark photon masses greater than 600 MeV the combined limit is lower than
8~$\times\, 10^{-7}$ resulting more stringent than present constraints from
other experiments.
Using 1.63 fb$^{-1}$ of integrated luminosity collected by the KLOE
experiment about $7\times 10^4$ $K_S \rightarrow \pi^{\pm}e^{\mp}\nu$ 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 in
agreement with CPT invariance.
The three precision measurements of the cross section
$\sigma\big(e^+e^-\rightarrow\pi^+\pi^-\gamma(\gamma)\big)$ using initial state
radiation by the KLOE collaboration provide an important input ...for the
prediction of the hadronic contribution to the anomalous magnetic moment of the
muon. These measurements are correlated for both statistical and systematic
uncertainties and, therefore, the simultaneous use of these measurements
requires covariance matrices that fully describe the correlations. We present
the construction of these covariance matrices and use them to determine a
combined KLOE measurement for
$\sigma\big(e^+e^-\rightarrow\pi^+\pi^-\gamma(\gamma)\big)$. We find, from this
combination, a two-pion contribution to the muon magnetic anomaly in the energy
range $0.10 < s < 0.95$ GeV$^2$ of $a_{\mu}^{\pi^+\pi^-} = (489.8 \pm 1.7_{\rm
stat} \pm 4.8_{\rm sys} ) \times 10^{-10}$.
We describe the first two European cases of acute axonal motor neuropathy with both IgG and IgA anti-GD1a antibodies following
Campylobacter enteritis. Both patients acutely developed severe weakness ...without sensory involvement, had antibodies to
Campylobacter jejuni and polyclonal IgG and IgA titers ≥ 12 800 to GD1a at onset, which decreased during follow-up. Serial electrophysiologic studies showed: 1, normal or only slightly slowed motor conductions; 2, evidence of a progressive loss of excitability and conduction failure in nerve fibers undergoing axonal degeneration in intermediate nerve segments and evidence of distal axonal involvement in one nerve; 3, normal sensory conductions, sensory potential amplitudes and somatosensory evoked potentials. Although we cannot exclude that axonal degeneration followed demyelination, we think that anti-GD1a antibodies account for the axonal involvement because GD1a is present in the axolemma and exposed at the node of Ranvier and in nerve terminals. The exclusive motor involvement could be explained by the fact that GD1a has a different internal structure in motor and sensory fibers.
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