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A. Kupsc

Publications and source records attributed to A. Kupsc.

At least 37 records · Page 2Linked to original sources
arXiv2016

Search for an Isospin I =3 Dibaryon

Various theoretical calculations based on QCD or hadronic interactions predict that in addition to the recently observed dibaryon resonance $d^*(2380)$ with $I(J^P) = 0(3^+)$ there should also exist a dibaryon resonance with mirrored quantum numbers $I(J^P) = 3(0^+)$. We report here on a search for such a $NN$-decoupled state in data on the $pp \to ppπ^+π^+π^-π^-$ reaction. Since no clear-cut evidence has been found, we give upper limits for the production cross section of such a resonance in the mass range 2280 - 2500 MeV.

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arXiv2016

Mini-Proceedings, 18th meeting of the Working Group on Radiative Corrections and MC Generators for Low Energies

The mini-proceedings of the 18$^{\mathrm{th}}$ Meeting of the "Working Group on Radiative Corrections and MonteCarlo Generators for Low Energies" held in Frascati, 19$^{\mathrm{th}}$ - 20$^{\mathrm{st}}$ May, are presented. These meetings, started in 2006, have as aim to bring together experimentalists and theoreticians working in the fields of meson transition form factors, hadronic contributions to the anomalous magnetic moment of the leptons, and the effective fine structure constant. The development of MonteCarlo generators and Radiative Corrections for precision $e^+e^-$ and $τ$-lepton physics are also covered, with emphasis on meson production. At this workshop, a documentary entitled {\it Bruno Touschek with AdA in Orsay} commemorating the first observation of electron-positron collisions in a laboratory was also presented. With this edition, the working group reaches 10 years of continuous activities.

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arXiv2016

Measurement of the $ϕ\to π^0 e^+e^-$ transition form factor with the KLOE detector

A measurement of the vector to pseudoscalar conversion decay $ϕ\to π^0 e^+e^-$ with the KLOE experiment is presented. A sample of $\sim 9500$ signal events was selected from a data set of 1.7 fb$^{-1}$ of $e^+e^-$ collisions at $\sqrt{s} \sim m_ϕ$ collected at the DA$Φ$NE $e^+e^-$ collider. These events were used to obtain the first measurement of the transition form factor $| F_{ϕπ^0}(q^2) |$ and a new measurement of the branching ratio of the decay: $\rm{BR}\,(ϕ\to π^0 e^+e^-) = (\,1.35 \pm 0.05^{\,\,+0.05}_{\,\,-0.10}\,) \times 10 ^{-5}$. The result improves significantly on previous measurements and is in agreement with theoretical predictions.

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arXiv2016

Limit on the production of a new vector boson in $\mathrm{e^+ e^-}\rightarrow {\rm U}γ$, U$\rightarrow π^+π^-$ with the KLOE experiment

The recent interest in a light gauge boson in the framework of an extra U(1) symmetry motivates searches in the mass range below 1 GeV. We present a search for such a particle, the dark photon, in ${\rm e^+ e^-}\rightarrow {\rm U}γ$, U$\rightarrow π^+π^-$ based on 28 million $\mathrm{e^+ e^-} \rightarrow π^+ π^-γ$ events collected at DA$Φ$NE by the KLOE experiment. The $π^+ π^-$ production by initial-state radiation compensates for a loss of sensitivity of previous KLOE ${\rm U} \rightarrow \mathrm{e^+ e^-}$, $μ^+μ^-$ searches due to the small branching ratios in the $ρ-ω$ resonance region. We found no evidence for a signal and set a limit at 90\% CL on the mixing strength between the photon and the dark photon, $\varepsilon^2$, in the U mass range between $527$ and $987$~MeV. Above 700 MeV this new limit is more stringent than previous ones.

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arXiv2016

Precision measurement of the $η\toπ^+π^-π^0$ Dalitz plot distribution with the KLOE detector

Using $1.6$ fb$^{-1}$ of $e^+ e^-\toϕ\toηγ$ data collected with the KLOE detector at DA$Φ$NE, the Dalitz plot distribution for the $η\to π^+ π^- π^0$ decay is studied with the world's largest sample of $\sim 4.7 \cdot 10^6$ events. The Dalitz plot density is parametrized as a polynomial expansion up to cubic terms in the normalized dimensionless variables $X$ and $Y$. The experiment is sensitive to all charge conjugation conserving terms of the expansion, including a $gX^2Y$ term. The statistical uncertainty of all parameters is improved by a factor two with respect to earlier measurements.

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arXiv2015

Limit on the production of a low-mass vector boson in $\mathrm{e}^{+}\mathrm{e}^{-} \to \mathrm{U}γ$, $\mathrm{U} \to \mathrm{e}^{+}\mathrm{e}^{-}$ with the KLOE experiment

The existence of a new force beyond the Standard Model is compelling because it could explain several striking astrophysical observations which fail standard interpretations. We searched for the light vector mediator of this dark force, the $\mathrm{U}$ boson, with the KLOE detector at the DA$Φ$NE $\mathrm{e}^{+}\mathrm{e}^{-}$ collider. Using an integrated luminosity of 1.54 fb$^{-1}$, we studied the process $\mathrm{e}^{+}\mathrm{e}^{-} \to \mathrm{U}γ$, with $\mathrm{U} \to \mathrm{e}^{+}\mathrm{e}^{-}$, using radiative-return to search for a resonant peak in the dielectron invariant-mass distribution. We did not find evidence for a signal, and set a 90\%~CL upper limit on the mixing strength between the Standard Model photon and the dark photon, $\varepsilon^2$, at $10^{-6}$--$10^{-4}$ in the 5--520~MeV/c$^2$ mass range.

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arXiv2015

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.

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arXiv2014

MesonNet 2014 International Workshop. Mini-proceedings

The MesonNet International Workshop was held in the Laboratori Nazionali di Frascati from September the 29th to October the 1st, 2014, being the concluding meeting of the MesonNet research network within EU HadronPhysics3 project. MesonNet is a research network focused on light meson physics gathering experimentalist and theoreticians from Europe and abroad. An overview of the research projects related to the scope of the network is presented in these mini-proceedings.

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arXiv2014

Study of Dalitz decay phi -> eta e+e- with KLOE detector

We have studied the vector to pseudoscalar conversion decay phi -> eta e+e-, with eta -> pi0pi0pi0, with the KLOE detector at DAPHNE. The data set of 1.7 fb-1 of e+e- collisions at sqrt(s)~Mphi contains a clear conversion decay signal of ~31,000 events from which we measured a value of BR(phi -> eta e+e-)=(1.075+-0.007+-0.038)x10-4. The same sample is used to determine the transition form factor by a fit to the e+e- invariant mass spectrum, obtaining b(phi eta) =(1.17 +- 0.10 + 0.07) GeV-2, that improves by a factor of five the precision of the previous measurement and is in good agreement with VMD expectations.

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arXiv2014

Search for light vector boson production in $e^+e^- \rightarrow μ^+ μ^- γ$ interactions with the KLOE experiment

We have searched for a light vector boson $U$, the possible carrier of a "dark force", with the KLOE detector at the DA$Φ$NE \epm\ collider, motivated by astrophysical evidence for the presence of dark matter in the universe. Using \epm\ collisions collected with an integrated luminosity of $239.3$~pb$^{-1}$, we look for a dimuon mass peak in the reaction \epm\to$μ^+ μ^-$\gam, corresponding to the decay $U\toμ^+μ^-$. We find no evidence for a $U$ vector boson signal. We set a 90\% CL upper limit for the mixing parameter squared between the photon and the $U$ boson of 1.6$\times$10$^{-5}$ to 8.6$\times$10$^{-7}$ for the mass region $520<m_{\rm U}<980$ MeV.

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arXiv2014

Evidence for a New Resonance from Polarized Neutron-Proton Scattering

Exclusive and kinematically complete high-statistics measurements of quasifree polarized $\vec{n}p$ scattering have been performed in the energy region of the narrow resonance structure $d^*$ with $I(J^P) = 0(3^+)$, $M \approx$ 2380 MeV/$c^2$ and $Γ\approx$ 70 MeV observed recently in the double-pionic fusion channels $pn \to dπ^0π^0$ and $pn \to dπ^+π^-$. The experiment was carried out with the WASA detector setup at COSY having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process $\vec{d}p \to np + p_{spectator}$. That way the $np$ analyzing power $A_y$ was measured over a large angular range. The obtained $A_y$ angular distributions deviate systematically from the current SAID SP07 NN partial-wave solution. Incorporating the new $A_y$ data into the SAID analysis produces a pole in the $^3D_3 - ^3G_3$ waves as expected from the $d^*$ resonance hypothesis.

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arXiv2014

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

Neutral kaon pairs produced in phi 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 phi->K_S K_L->pi+pi-pi+pi- based on 1.7 fb-1 of data collected by the KLOE experiment at the Frascati phi-factory DAFNE. The data are used to perform a measurement of the CPT-violating parameters Delta_amu for neutral kaons in the contest of the Standard Model Extension framework. The parameters measured in the reference frame of the fixed stars are: Delta_ao = (-6.0 +- 7.7_{stat} +- 3.1_{syst}) x 10^{-18} GeV Delta_ax = ( 0.9 +- 1.5_{stat} +- 0.6_{syst}) x 10^{-18} GeV Delta_ay = (-2.0 +- 1.5_{stat} +- 0.5_{syst}) x 10^{-18} GeV Delta_az = ( 3.1 +- 1.7_{stat} +- 0.5_{syst}) x 10^{-18} GeV These are presently the most precise measurements in the quark sector of the Standard Model Extension.

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arXiv2013

Dispersive analysis for $η\to γγ^*$

A dispersion integral is derived that connects data on $η\to π^+π^-γ$ to the $η\to γγ^*$ transition form factor. A detailed analysis of the uncertainties is provided. We find for the slope of the $η$ transition form factor at the origin $b_η= (2.05 {}^{+0.22}_{-0.10})\, {\rm GeV}^{-2}$. Using an additional, plausible assumption, one finds for the corresponding slope of the $η'$ transition form factor, $b_{η'} = (1.58 {}^{+0.15}_{-0.08})\, {\rm GeV}^{-2}$. Both values are consistent with all recent data, but differ from some previous theoretical analyses.

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arXiv2013

MesonNet 2013 International Workshop. Mini-proceedings

The mini-proceedings of the MesonNet 2013 International Workshop held in Prague from June 17th to 19th, 2013, are presented. MesonNet is a research network within EU HadronPhysics3 project (1/2012 -- 12/2014). The web page of the conference, which contains all talks, can be found at http://ipnp.mff.cuni.cz/mesonnet13

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arXiv2013

Search for the eta-mesic 4He with WASA-at-COSY detector

An exclusive measurement of the excitation function for the dd->3Heppi- reaction was performed at the Cooler Synchrotron COSY-Juelich with the WASA-at-COSY detection system. The data were taken during a slow acceleration of the beam from 2.185 GeV/c to 2.400 GeV/c crossing the kinematic threshold for the eta meson production in the dd->4He-eta reaction at 2.336 GeV/c. The corresponding excess energy with respect to the 4He-eta system varied from -51.4MeV to 22MeV. The integrated luminosity in the experiment was determined using the dd->3Hen reaction. The shape of the excitation function for the dd->3Heppi- was examined. No signal of the 4He-eta bound state was observed. An upper limit for the cross-section for the bound state formation and decay in the process dd->(4He-eta)bound->3Heppi- was determined on the 90% confidence level and it varies from 20nb to 27nb for the bound state width ranging from 5MeV to 35MeV, respectively.

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arXiv2013

MesonNet Workshop on Meson Transition Form Factors

The mini-proceedings of the Workshop on Meson Transition Form Factors held in Cracow from May 29th to 30th, 2012 introduce the meson transition form factor project with special emphasis on the interrelations between the various form factors (on-shell, single off-shell, double off-shell). Short summaries of the talks presented at the workshop follow.

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arXiv2013

Recent results on hadron physics at KLOE

One of the basic motivations of the KLOE and KLOE-2 collaborations is the test of fundamental symmetries and the search for phenomena beyond the Standard Model via the hadronic and leptonic decays of ground-state mesons and via their production in the fusion of virtual gamma quanta exchanged between colliding electrons and positrons. This contribution includes brief description of results of recent analysis of the KLOE data aimed at (i) the search for the dark matter boson, (ii) determination of the hadronic and light-by-light contributions to the g-2 muon anomaly and (iii) tests of QCD anomalies.

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