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

Measurement of \Gamma(\eta -> \pi^+\pi^-\gamma)/\Gamma(\eta -> \pi^+\pi^-\pi^0) with the KLOE Detector

The ratio R_{\eta}=\Gamma(\eta -> \pi^+\pi^-\gamma)/\Gamma(\eta -> \pi^+\pi^-\pi^0) has been measured by analyzing 22 million \phi \to \eta \gamma decays collected by the KLOE experiment at DA\PhiNE, corresponding to an integrated luminosity of 558 pb^{-1}. The \eta \to \pi^+\pi^-\gamma proceeds both via the \rho resonant contribution, and possibly a non-resonant direct term, connected to the box anomaly. Our result, R_{\eta}= 0.1856\pm 0.0005_{stat} \pm 0.0028_{syst}, points out a sizable contribution of the direct term to the total width. The di-pion invariant mass for the \eta -> \pi^+\pi^-\gamma decay could be described in a model-independent approach in terms of a single free parameter, \alpha. The determined value of the parameter \alpha is \alpha = (1.32 \pm 0.08_{stat} +0.10/-0.09_{syst}\pm 0.02_{theo}) GeV^{-2}Comment: Paper in press, accepted by PL

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

KLOE results in kaon physics and prospects for KLOE-2

The phi-factory DAPHNE offers a possibility to select pure kaon beams, charged and neutral ones. In particular, neutral kaons from phi->KS KL are produced in pairs and the detection of a KS (KL) tags the presence of a KL (KS). This allows to perform precise measurements of kaon properties by means of KLOE detector. Another advantage of a phi-factory consists in fact that the neutral kaon pairs are produced in a pure quantum state (J^(PC) = 1^(--)), which allowsto investigate CP and CPT symmetries via quantum interference effects, as well as the basic principles of quantum mechanics.A review of the most recent results of the KLOE experiment at DAPHNE using pure kaon beams or via quantum interferometry is presented together with prospects for kaon physics at KLOE-2.Comment: 5 pages, 4 figures, From Phi To Psi 2011 conference, to be published in Nuclear Physics B (Proceedings Supplements

GASTONE64: A new front-end ASIC for the cylindrical GEM Inner Tracker of KLOE-2 experiment at DAΦNE

GASTONE64 (Gem Amplifier Shaper Tracking ON Events) is a novel 64-channel mixed analog-digital ASIC developed to readout the cylindrical GEM inner tracking detector of the KLOE-2 apparatus at the e+e- DAΦNE collider. It has been designed in the CMOS 0.35μm technology and each analog channel is made of preamplifier, shaper and discriminator. The expected input charge ranges between few fC up to 40 fC, the charge sensitivity is 16 mV/fC while the equivalent input noise charge (ENC) is 800 e -+40 e-/pF. The discriminated signals are read-out using a 100 MBit/s LVDS serial data link. The power consumption is about 6 mW/channel. © 2013 Elsevier B.V

Charge reconstruction in large-area photomultipliers

Large-area PhotoMultiplier Tubes (PMT) allow to efficiently instrument Liquid Scintillator (LS) neutrino detectors, where large target masses are pivotal to compensate for neutrinos' extremely elusive nature. Depending on the detector light yield, several scintillation photons stemming from the same neutrino interaction are likely to hit a single PMT in a few tens/hundreds of nanoseconds, resulting in several photoelectrons (PEs) to pile-up at the PMT anode. In such scenario, the signal generated by each PE is entangled to the others, and an accurate PMT charge reconstruction becomes challenging. This manuscript describes an experimental method able to address the PMT charge reconstruction in the case of large PE pile-up, providing an unbiased charge estimator at the permille level up to 15 detected PEs. The method is based on a signal filtering technique (Wiener filter) which suppresses the noise due to both PMT and readout electronics, and on a Fourier-based deconvolution able to minimize the influence of signal distortions ---such as an overshoot. The analysis of simulated PMT waveforms shows that the slope of a linear regression modeling the relation between reconstructed and true charge values improves from $0.769 \pm 0.001$ (without deconvolution) to $0.989 \pm 0.001$ (with deconvolution), where unitary slope implies perfect reconstruction. A C++ implementation of the charge reconstruction algorithm is available online at http://www.fe.infn.it/CRA

Test of CPT and Lorentz symmetry in entangled neutral kaons with the KLOE experiment

Neutral kaon pairs produced in Ï\u86 decays in anti-symmetric entangled state can be exploited to search for violation of CPT symmetry and Lorentz invariance. We present an analysis of the CP-violating process Ï\u86 â\u86\u92 KSKL â\u86\u92 Ï\u80 +Ï\u80 -Ï\u80 +Ï\u80 - based on 1.7 fb -1 of data collected by the KLOE experiment at the Frascati Ï\u86-factory DAΦNE. The data are used to perform a measurement of the CPT-violating parameters δaμ for neutral kaons in the context of the Standard Model Extension framework. The parameters measured in the reference frame of the fixed stars are:δa0=(-6.0±7.7stat±3.1syst)Ã\u9710-18 GeV,δaX=(0.9±1.5stat±0.6syst)Ã\u9710-18 GeV,δaY=(-2.0±1.5stat±0.5syst)Ã\u9710-18 GeV,δaZ=(3.1±1.7stat±0.5syst)Ã\u9710-18 GeV. These are presently the most precise measurements in the quark sector of the Standard Model Extension. © 2014 The Authors

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

Measurement of Gamma(eta -> pi(+)pi(-)gamma)/Gamma(eta -> pi(+)pi(-)pi(0)) with the KLOE detector

The ratio R-eta = Gamma(eta -> pi(+)pi(-)gamma)/Gamma(eta -> pi(+)pi(-)pi(0)) has been measured by analysing 22 million phi -> eta gamma decays collected by the KLOE experiment at DANE, corresponding to an integrated luminosity of 558 pb(-1). The eta -> pi(+)pi(-)gamma proceeds both via the rho resonant contribution, and possibly a non-resonant direct term, connected to the box anomaly. Our result, R-eta = 0.1856 +/- 0.0005(stat)+/- 0.0028(syst), points out a sizable contribution of the direct term to the total width. The di-pion invariant mass for the eta -> pi(+)pi(-)gamma decay could be described in a model-independent approach in terms of a(-) single free parameter, alpha. The determined value of the parameter alpha is alpha = (1.32 +/- 0.08(stat-0.09syst)(+0.10) +/- 0.02(theo)) GeV-2. 2012 Elsevier B.V. All rights reserved

Precision measurements of the e⁺e^- → π⁺π^-(γ) cross section with the KLOE detector

The muon anomalous magnetic moment is one of the most precisely measured quantities in particle physics and a persistent discrepancy of about $3 \sigma$ between standard model (SM) prediction and the experimental measurement has been observed. The leading order contribution $a_{\mu }^{hlo}$ is actually the main source of uncertainty in the theoretical evaluation of the muon anomaly. It is obtained by a dispersion integral using the precision measurement of hadronic cross section. The KLOE experiment at the DAΦNE $\phi$ −factory in Frascati was the first to exploit Initial State Radiation (ISR) processes to obtain the $e^{+}e^{-}\rightarrow \pi ^{+}\pi ^{-}\left ( \gamma \right )$ cross section below 1 GeV, that accounts for most (70%) of the leading order contribution to the muon anomaly. In year 2005 and 2008 the KLOE-collaboration has published two measurements of the $\pi ^{+}\pi ^{-}$ cross section with the photon in the initial state emitted at small angle, and an independent measurement with the photon emitted at large angle was finalized in year 2011. These measurements were normalized using luminosity from Bhabha. In the last years, a new analysis of KLOE data has been performed for obtaining the pion form factor directly from the bin-by-bin $\pi ^{+}\pi ^{-}\gamma$ to $\mu ^{+}\mu ^{-}\gamma$ ratio. We present the results of this new measurement, showing the comparison with our previous measurements, and its impact on the hadronic contribution to the muon anomaly