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I. Sarra

Publications and source records attributed to I. Sarra.

67 records · Page 4Linked to original sources
arXiv2012

Measurement of η meson production in γγ interactions and Γ(η-->γγ) with the KLOE detector

We present a measurement of η 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 ϕ-factory DAΦNE with an integrated luminosity of 0.24 fb^{-1}. The e^+e^- --> e^+e^-η cross section is measured without detecting the outgoing electron and positron, selecting the decays η-->π^+π^-π^0 and η-->π^0π^0π^0. The most relevant background is due to e^+e^- --> ηγ when the monochromatic photon escapes detection. The cross section for this process is measured as σ(e^+e^- -->ηγ) = (856 \pm 8_{stat} \pm 16_{syst}) pb. The combined result for the e^+e^- -->e^+e^-η cross section is σ(e^+e^- -->e^+e^-η) = (32.72 \pm 1.27_{stat} \pm 0.70_{syst}) pb. From this we derive the partial width Γ(η-->γγ) = (520 \pm 20_{stat} \pm 13_{syst}) eV. This is in agreement with the world average and is the most precise measurement to date.

hep-ex↗
arXiv2012

Measurement of Γ(η-> π^+π^-γ)/Γ(η-> π^+π^-π^0) with the KLOE Detector

The ratio R_η=Γ(η-> π^+π^-γ)/Γ(η-> π^+π^-π^0) has been measured by analyzing 22 million ϕ\to ηγdecays collected by the KLOE experiment at DA\PhiNE, corresponding to an integrated luminosity of 558 pb^{-1}. The η\to π^+π^-γproceeds both via the ρresonant contribution, and possibly a non-resonant direct term, connected to the box anomaly. Our result, R_η= 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 η-> π^+π^-γdecay could be described in a model-independent approach in terms of a single free parameter, α. The determined value of the parameter αis α= (1.32 \pm 0.08_{stat} +0.10/-0.09_{syst}\pm 0.02_{theo}) GeV^{-2}

hep-ex↗
arXiv2011

Observation of the rare eta->e+e-e+e- decay with the KLOE experiment

We report the first observation of the rare eta->e+e-e+e- decay based on 1.7 fb^{-1} collected by the KLOE experiment at the DAFNE phi-factory. The selection of the e+e-e+e- final state is fully inclusive of radiation. We have identified 362 +- 29 events resulting in a branching ratio of (2.4 +- 0.2_stat+bckg +- 0.1_syst) x 10^{-5}.

hep-ex↗
arXiv2011

Measurement of $Γ(η\to π^+π^-γ)/Γ(η\to π^+π^-π^0)$ with KLOE experiment

We report the measurement of the ratio $Γ(η\to π^+π^-γ)/Γ(η\to π^+π^-π^0)$ analyzing a large sample of $ϕ\to ηγ$ decays recorded with the KLOE experiment at the DA$Φ$NE $e^+ e^-$ collider, corresponding to an integrated luminosity of 558 pb$^{-1}$. The $η\to π^+π^-γ$ process is supposed to proceed both via a resonant contribution, mediated by the $ρ$ meson, and a non resonant direct term, connected to the box anomaly. The presence of the direct term affects the partial width value. Our result $R_η=Γ(η\to π^+ π^- γ)/Γ(η\to π^+ π^- π^0)= 0.1838\pm 0.0005_{stat} \pm 0.0030_{syst}$ is in agreement with a recent CLEO measurement, which differs by more 3 $σ$ from the average of previous results.

hep-ex↗
arXiv2011

$γγ$ physics with the KLOE experiment

The processes $e^+e^-\to e^+e^-X$, with $X$ being either the $η$ meson or $π^0π^0$, are studied at DA$Φ$NE, with $e^+e^-$ beams colliding at $\sqrt{s}\simeq1$ GeV, below the $ϕ$ resonance peak. The data sample is from an integrated luminosity of 240 pb$^{-1}$, collected by the KLOE experiment without tagging of the outgoing $e^+e^-$. Preliminary results are presented on the observation of the $γγ\toη$ process, with both $η\toπ^+π^-π^0$ and $η\toπ^0π^0π^0$ channels, and the evidence for $γγ\toπ^0π^0$ production at low $π^0π^0$ invariant mass.

hep-ex↗
arXiv2011

U boson searches at KLOE

The existence of a secluded gauge sector could explain several puzzling astrophysical observations. This hypothesis can be tested at low energy e+e- colliders such as DAPHNE. Preliminary results obtained with KLOE data and perpectives for the KLOE-2 run, where a larger data sample is expected, are discussed.

hep-ex↗
arXiv2010

Physics with the KLOE-2 experiment at the upgraded DA$ϕ$NE

Investigation at a $ϕ$--factory can shed light on several debated issues in particle physics. We discuss: i) recent theoretical development and experimental progress in kaon physics relevant for the Standard Model tests in the flavor sector, ii) the sensitivity we can reach in probing CPT and Quantum Mechanics from time evolution of entangled kaon states, iii) the interest for improving on the present measurements of non-leptonic and radiative decays of kaons and eta/eta$^\prime$ mesons, iv) the contribution to understand the nature of light scalar mesons, and v) the opportunity to search for narrow di-lepton resonances suggested by recent models proposing a hidden dark-matter sector. We also report on the $e^+ e^-$ physics in the continuum with the measurements of (multi)hadronic cross sections and the study of gamma gamma processes.

hep-ex↗
arXiv2009

Test of a LYSO matrix with an electron beam

The angular coverage extension of the KLOE-2 electromagnetic calorimeter, from a polar angle of 20$^{\circ}$ down to $8^{\circ}$, will increase the multiphoton detection capability of the experiment enhancing the search reach for rare kaon, $η$ and $η'$ prompt decay channels. The basic layout of the calorimeter extension consists of two small barrels of LYSO crystals readout with APD photosensors aiming to achieve a timing resolution between 300 and 500 ps for 20 MeV photons. The first test of a (5.5$\times6\times$13) cm$^3$ prototype for such a detector was carried out in april 2009 at the Beam Test Facility of Laboratori Nazionali di Frascati of INFN with an electron beam from 100 to 500 MeV. In the selected energy range, we measured a light yield of 500$÷$800 p.e./Mev, an energy resolution which can be parametrized as $0.05 \oplus 0.01/({\rm E/GeV}) \oplus 0.015/\sqrt{\rm{E/GeV}}$, a position resolution of 2.8 mm and a timing resolution of 200$÷$300 ps.

physics.ins-det↗
arXiv2009

Measurement of neutron detection efficiency between 22 and 174 MeV using two different kinds of Pb-scintillating fiber sampling calorimeters

We exposed a prototype of the lead-scintillating fiber KLOE calorimeter to neutron beam of 21, 46 and 174 MeV at The Svedberg Laboratory, Uppsala, to study its neutron detection efficiency. This has been found larger than what expected considering the scintillator thickness of the prototype. %To check our method, we measured also the neutron %detection efficiency of a 5 cm thick NE110 scintillator. We show preliminary measurement carried out with a different prototype with a larger lead/fiber ratio, which proves the relevance of passive material to neutron detection efficiency in this kind of calorimeters.

physics.ins-det↗
arXiv2009

QCALT: a tile calorimeter for KLOE-2 upgrade

The upgrade of the DA$Φ$NE machine layout requires a modification of the size and position of the inner focusing quadrupoles of KLOE-2 thus asking for the realization of two new calorimeters covering the quadrupoles area. To improve the reconstruction of $K_L\to 2π^0$ events with photons hitting the quadrupoles a calorimeter with high efficiency to low energy photons (20-300 MeV), time resolution of less than 1 ns and space resolution of few cm, is needed. To match these requirements, we are designing a tile calorimeter, QCALT, where each single tile is readout by mean of SiPM for a total granularity of 2400 channels. We show first tests of the different calorimeter components.

physics.ins-det↗
arXiv2009

Tile and crystal calorimeter for KLOE-2 experiment

The upgrade of the DA$Φ$NE machine layout requires a modification of the size and position of the inner focusing quadrupoles of KLOE$^2$ thus asking for the realization of two new calorimeters covering the quadrupoles area. To improve the reconstruction of $K_L\to 2π^0$ events with photons hitting the quadrupoles, a tile calorimeter, QCALT, with high efficiency to low energy photons (20-300 MeV), time resolution of less than 1 ns and space resolution of few cm, is needed. We propose a tile calorimeter with a high granularity readout corresponding to about 2500 silicon photomultipliers (SiPM) of $1\times 1$ mm$^2$ area. Moreover, the low polar angle regions need the realization of a dense crystal calorimeter with very high time resolution performances to extend the acceptance for multiphotons events. Best candidates for this calorimeter are LYSO crystals with APD readout or PbWO$_4$ crystals with large area SIPM readout.

physics.ins-det↗