37 research outputs found
Studies of the collision-based Xe VI and Xe VII spectra
Collision-based spectroscopy of a Xeq+ (q = 6, 7) beam with a target T (T = Na, Ar) has been performed in the 35-800-nm wavelength region. Twenty-five new Xe VI lines and twenty-two new Xe VII lines were classified, twelve new energy levels of Xe VI and nine new energy levels of Xe VII were established, and one energy level of Xe VI was revised from the classified transitions. The analysis was supported by Hartree-Fock calculations. (C) 1997 Optical Society of America [S0740-3224(97)00512-2].14123277328
Search for dark Higgsstrahlung in e+ e- -> mu+ mu- and missing energy events with the KLOE experiment
We searched for evidence of a Higgsstrahlung process in a secluded sector,
leading to a final state with a dark photon U and a dark Higgs boson h', with
the KLOE detector at DAFNE. We investigated the case of h' lighter than U, with
U decaying into a muon pair and h' producing a missing energy signature. We
found no evidence of the process and set upper limits to its parameters in the
range 2m_mu<m_U<1000 MeV, m_h'<m_U.Comment: 16 pages, 7 figures, submitted to Physics Letters
Precision measurement of and determination of the contribution to the muon anomaly with the KLOE detector
We have measured the ratio
, with the KLOE detector at DANE for a total integrated
luminosity of 240 pb. From this ratio we obtain the cross section
. From the cross section we determine the
pion form factor and the two-pion contribution to the muon anomaly
for GeV, = . This result confirms the
current discrepancy between the Standard Model calculation and the experimental
measurement of the muon anomaly.Comment: 18 pages, 8 figures, minor text corrections, one table added, version
to appear on Physics Letters
A new limit on the CP violating decay KS -> 3pi0 with the KLOE experiment
We have carried out a new direct search for the CP violating decay KS -> 3pi0
with 1.7 fb^-1 of e+e- collisions collected by the KLOE detector at the
phi-factory DAFNE. We have searched for this decay in a sample of about 5.9 x
10^8 KS KL events tagging the KS by means of the KL interaction in the
calorimeter and requiring six prompt photons. With respect to our previous
search, the analysis has been improved by increasing of a factor four the
tagged sample and by a more effective background rejection of fake KS tags and
spurious clusters. We find no candidates in data and simulated background
samples, while we expect 0.12 standard model events. Normalizing to the number
of KS -> 2pi0 events in the same sample, we set the upper limit on BR(KS ->
3pi0 < 2.6 x 10^-8 at 90% C.L., five times lower than the previous limit. We
also set the upper limit on the eta_000 parameter, |eta_000 | < 0.0088 at 90%
C.L., improving by a factor two the latest direct measurement.Comment: Accepted for publication in Physics Letters B (15 pages, 13 figures
Measurement of {\eta} meson production in {\gamma}{\gamma} interactions and {\Gamma}({\eta}-->{\gamma}{\gamma}) with the KLOE detector
We present a measurement of {\eta} meson production in photon-photon
interactions produced by electron-positron beams colliding with \sqrt{s}=1 GeV.
The measurement is done with the KLOE detector at the \phi-factory DA{\Phi}NE
with an integrated luminosity of 0.24 fb^{-1}. The e^+e^- --> e^+e^-{\eta}
cross section is measured without detecting the outgoing electron and positron,
selecting the decays {\eta}-->{\pi}^+{\pi}^-{\pi}^0 and
{\eta}-->{\pi}^0{\pi}^0{\pi}^0. The most relevant background is due to e^+e^-
--> {\eta}{\gamma} when the monochromatic photon escapes detection. The cross
section for this process is measured as {\sigma}(e^+e^- -->{\eta}{\gamma}) =
(856 \pm 8_{stat} \pm 16_{syst}) pb. The combined result for the e^+e^-
-->e^+e^-{\eta} cross section is {\sigma}(e^+e^- -->e^+e^-{\eta}) = (32.72 \pm
1.27_{stat} \pm 0.70_{syst}) pb. From this we derive the partial width
{\Gamma}({\eta}-->{\gamma}{\gamma}) = (520 \pm 20_{stat} \pm 13_{syst}) eV.
This is in agreement with the world average and is the most precise measurement
to date.Comment: Version accepted by JHE
ABC Effect in Basic Double-Pionic Fusion --- Observation of a new resonance?
We report on a high-statistics measurement of the basic double pionic fusion
reaction over the energy region of the so-called ABC
effect, a pronounced low-mass enhancement in the -invariant mass
spectrum. The measurements were performed with the WASA detector setup at COSY.
The data reveal the ABC effect to be associated with a Lorentzian shaped energy
dependence in the integral cross section. The observables are consistent with a
resonance with in both and systems.
Necessary further tests of the resonance interpretation are discussed
Search for dark Higgsstrahlung in e+e-→μ+μ- and missing energy events with the KLOE experiment
We searched for evidence of a Higgsstrahlung process in a secluded sector, leading to a final state with a dark photon U and a dark Higgs boson h', with the KLOE detector at DA Phi NE. We investigated the case of h' lighter than U, with U decaying into a muon pair and h' producing a missing energy signature. We found no evidence of the process and set upper limits to its parameters in the range 2m(mu) < m(U) < 1000 MeV, m(h') < m(U). (C) 2015 The Authors. Published by Elsevier B.V
Dark forces at DAΦNE
The DAΦNE Φ-factory is an ideal place to search for forces beyond the Standard Model. By using the KLOE detector, limits on U-boson coupling ϵ2 of the order of 10-5 ÷ 10-7 and on the αD × ϵ2 product have been set through the study of the Φ Dalitz decay, Uγ events and the Higgsstrahlung process. An improvement of these limits is expected thanks to the KLOE detector and DAΦNE upgrades of KLOE-2
Search for light vector boson production in interactions with the KLOE experiment
We have searched for a light vector boson , the possible carrier of a
"dark force", with the KLOE detector at the DANE \epm\ collider,
motivated by astrophysical evidence for the presence of dark matter in the
universe. Using \epm\ collisions collected with an integrated luminosity of
~pb, we look for a dimuon mass peak in the reaction \epm\to\gam, corresponding to the decay . We find no evidence
for a vector boson signal. We set a 90\% CL upper limit for the mixing
parameter squared between the photon and the boson of 1.610
to 8.610 for the mass region MeV.Comment: 12 pages, 7 figures, version accepted for publication in Physics
Letters