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We present a measurement of the doubly radiative decay η → π0γγ based ona sample of 82 million η mesons produced in the e+e− → ϕ → ηγ process at the Frascatiϕ-factory DAΦNE. From the data analysis, 1246 ± 133 signal events were observed. Bynormalising the signal to the well-known η → 3π0 decay the branching fraction B(η → π0γγ) ismeasured to be (0.98 ± 0.11stat ± 0.14syst) × 10−4. This result agrees with a preliminary KLOEmeasurement, but is a factor of two smaller than the current world average. Results for dΓ(η →π0γγ)/dM 2(γγ) are also presented and compared with the latest theoretical predictions.

A bstract We present a measurement of the doubly radiative decay η → π 0 γγ based on a sample of 82 million η mesons produced in the e + e − → ϕ → ηγ process at the Frascati ϕ -factory DAΦNE. From the data analysis, 1246 ± 133 signal events were observed. By normalising the signal to the well-known η → 3 π 0 decay the branching fraction is measured to be (0 . 98 ± 0 . 11 stat ± 0 . 14 syst ) × 10 − 4 . This result agrees with a preliminary KLOE measurement, but is a factor of two smaller than the current world average. Results for d Γ( η → π 0 γγ ) /dM 2 ( γγ ) are also presented and compared with the latest theoretical predictions.

A bstract The ratio R = Γ( K S → πeν ) / Γ( K S → π + π − ) has been measured with a sample of 300 million K S mesons produced in ϕ → K L K S decays recorded by the KLOE experiment at the DAΦNE e + e − collider. K S → πeν events are selected by a boosted decision tree built with kinematic variables and time-of-flight measurements. Data control samples of K L → πeν decays are used to evaluate signal selection efficiencies. With 49647 ± 316 signal events we measure R = (1 . 0421 ± 0 . 0066 stat ± 0 . 0075 syst ) × 10 − 3 . The combination with our previous measurement gives R = (1 . 0338 ± 0 . 0054 stat ± 0 . 0064 syst ) × 10 − 3 . From this value we derive the branching fraction B ( K S → πeν ) = (7 . 153 ± 0 . 037 stat ± 0 . 044 syst ) × 10 − 4 and f + (0) |V us | = 0 . 2170 ± 0 . 009.

The sensitivity of reaction mechanism in the formation of compound nucleus (CN) by the analysis of kinetic energy spectra of light particles and of reaction products are shown. The dependence of the PCN fusion probability of reactants and Wsur survival probability of CN against fission at its deexcitation on the mass and charge symmetries in the entrance channel of heavy-ion collisions, as well as on the neutron numbers is discussed. The possibility of conducting a complex program of investigations of the complete fusion by reliable ways depends on the detailed and refined methods of experimental and theoretical analyses.

The investigation of various properties of deexcitation of the same 220Th compound nucleus (CN), formed by the different mass (charge) asymmetric 16O+204Pb, 40Ar+180Hf, 82Se+138Ba and 96Zr+124Sn reactions is presented. The effective fission barrier < Bfis > value, as a function of the excitation energy ECN*, determined for each intermediate excited nucleus reached along the deexcitation cascade of the CN obtained by the four considered reactions is strongly sensitive to the various orbital angular momentum L=ℓℏ distributions of CN formed with the same excitation energy ECN* by the various entrance channels. Therefore, the competition between the fission and evaporation of light particles (neutron, proton, and α-particle) processes along the deexcitation cascade of CN is dependent on the orbital angular momentum distribution of CN. In fact, the ratio between the evaporation residue cross sections obtained when also the charged particles are emitted and the ones obtained after neutron emission only for the same CN with a fixed excitation energy ECN* is sensitive to the mass (charge) asymmetry of the entrance channel.

We study the effect of the static characteristics of nuclei and dynamics of the nucleus-nucleus interaction in the capture stage of reaction, in the competition between quasifission and complete fusion processes, as well as the angular momentum dependence of the competition between fission and evaporation processes along the de-excitation cascade of the compound nucleus. The results calculated for the mass-asymmetric and less mass-asymmetric reactions in the entrance channel are analyzed in order to investigate the role of the dynamical effects on the yields of the evaporation residue nuclei. We also discuss about uncertainties at the extraction of such relevant physical quantities as Γn/Γtot ratio or also excitation functions from the experimental results due to the not always realistic assumptions in the treatment and analysis of the detected events. This procedure can lead to large ambiguity when the complete fusion process is strongly hindered or when the fast fission contribution is large. We emphasize that a refined multiparameter model of the reaction dynamics as well as a more detailed and checked data analysis are strongly needed in heavy-ion collisions.

The AMADEUS collaboration studied the K− absorptions at low momentum in light nuclei leading to Σ0p final state. Those events were recorded by the KLOE detector, used as an active target, installed in the the DAΦNE collider. The results show that it is possible to isolate the process where the K− is absorbed by two nucleons and the decay products are emitted without any further final state interactions among other contributions involving more than two nucleons. Further, the possible contribution of a ppK− bound state was investigated. The best fit gives space to a yield of ppK−/Kstop− = (0.044 ± 0.009 stat−0.005+0.004) × 10−2 corresponding to a binding energy and a width of 45 and 30 MeV/c2, respectively. A statistical analysis of this result shows although that its significance is only at the level of 1σ.

The dynamical fusion process of 48Ca + 144Sm with different impact parameters near barrier is studied by an extended quantum molecular dynamics (EQMD) model, where width of wavepacket is dynamically treated based on variational principle. The time evolution of different energy components such as potential energy, kinetic energy, Coulomb energy and Pauli potential are analyzed when dynamical or fixed width is assumed in calculation. It is found that the dynamical wavepacket width can enhance the dissipation of incident energy and the fluctuations, which are important to form compound nuclei. Moreover, we compare the fusion barrier dependence on the incident energy when it is determined by both dynamical and fixed wavepacket width.

The DA[Phi]NE [Phi]-factory is an ideal place to search for forces beyond the Standard Model. By using the KLOE detector, limits on U-boson coupling [varepsilon] super(2) of the order of 10 super(-5) / 10 super(-7) and on the alpha sub(D) x [varepsilon] super(2) product have been set through the study of the [Phi] Dalitz decay, U gamma events and the Higgsstrahlung process. An improvement of these limits is expected thanks to the KLOE detector and DA[Phi]NE upgrades of KLOE-2.

The hindrance to complete fusion is a phenomenon presenting in the most part of the capture events in reactions with massive nuclei. This phenomenon is due to the onset of the quasifission process which competes with complete fusion during the evolution of the composed system formed at capture stage. The branching ratio between quasifission and complete fusion strongly depends from different characteristics of reacting nuclei in the entrance channel. The experimental and theoretical investigations of reaction dynamics connected with the formation of composed system is nowadays the main subject of the nuclear reactions. There is ambiguity in establishment of the reaction mechanism leading to the observed binary fissionlike fragments. The correct estimation of the fusion probability is important in planning experiments for the synthesis of superheavy elements. The experimental determination of evaporation residues only is not enough to restore the true reaction dynamics. The experimental observation of fissionlike fragments only cannot assure the correct distinguishing of products of the quasifission, fast fission, and fusion-fission processes which have overlapping in the mass (angular, kinetic energy) distributions of fragments. In this paper we consider a wide set of reactions (with different mass asymmetry and mass symmetry parameters) with the aim to explain the role played by many quantities on the reaction mechanisms. We also present the results of study of the 48Ca+249Bk reaction used to synthesize superheavy nuclei with Z 117 by the determination of the evaporation residue cross sections and the effective fission barriers < Bf > of excited nuclei formed along the de-excitation cascade of the compound nucleus.