Publications (60)159.22 Total impact

Article: On the effect of the Delta(1232) in hypernuclear nonmesonic weak decay: a microscopic approach
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ABSTRACT: The nonmesonic weak decay of $\Lambda$hypernuclei is studied within a microscopic diagrammatic approach which includes, for the first time, the effect or the $\Delta$baryon resonance. We adopt a nuclear matter formalism extended to finite nuclei via the local density approximation, a onemeson exchange weak transition potential, a Bonn nucleonnucleon strong potential and a $\Delta N\to NN$ strong potential based on the LandauMigdal theory. Ground state correlations and final state interactions (FSI), at second order in the baryonbaryon strong interaction, are introduced on the same footing for all the isospin channels of one and twonucleon induced decays. Weak decay rates and single and doublecoincidence nucleon spectra are predicted for $^{12}_\Lambda$C and compared with recent KEK and FINUDA data. The $\Delta(1232)$ introduces new FSIinduced decay mechanisms which lead to an improvement when comparing the obtained nucleon spectra with data, while it turns out to have a negligible effect on the decay rates. Discrepancies with experiment remain only for emission spectra involving protons, but are mostly restricted to doublenucleon correlations in the nonbacktoback kinematics.Physics Letters B 07/2012; 716(1). · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Selected topics in strangeness nuclear physics are critically reviewed. This includes production, structure and weak decay of $\Lambda$Hypernuclei, the $\bar K$ nuclear interaction and the possible existence of $\bar K$ bound states in nuclei. Perspectives for future studies on these issues are also outlined.European Physical Journal A 03/2012; 48(3). · 2.04 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The nonmesonic weak decay of polarized Λ hypernuclei is studied with a microscopic diagrammatic formalism in which one and twonucleoninduced decay mechanisms, Λ⃗N→NN and Λ⃗NN→NNN, are considered together with (and on the same ground of) nucleon final state interactions. We adopt a nuclear matter formalism extended to finite nuclei via the local density approximation. Our approach adopts different onemesonexchange weak transition potentials, while the strong interaction effects are accounted for by a Bonn nucleonnucleon interaction. We also consider the twopionexchange effect in the weak transition potential. Both the twonucleoninduced decay mechanism and the final state interactions reduce the magnitude of the asymmetry. The quantum interference terms considered in the present microscopic approach give rise to an opposite behavior of the asymmetry with increasing energy cuts to that observed in models describing the nucleon final state interactions semiclassically via the intranuclear cascade code. Our results for the asymmetry parameter in Λ12C obtained with different potential models are consistent with the asymmetry measured at KEK.Physical Review C 02/2012; 85(2). · 3.72 Impact Factor 
Article: Microscopic approach to the proton asymmetry in the nonmesonic weak decay of Lambdahypernuclei
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ABSTRACT: The nonmesonic weak decay of polarized $\Lambda$hypernuclei is studied with a microscopic diagrammatic formalism in which one and twonucleon induced decay mechanisms, $\vec{\Lambda} N \to NN$ and $\vec{\Lambda} NN \to NNN$, are considered together with (and on the same ground of) nucleon final state interactions. We adopt a nuclear matter formalism extended to finite nuclei via the local density approximation. Our approach adopts different onemesonexchange weak transition potentials, while the strong interaction effects are accounted for by a Bonn nucleonnucleon interaction. We also consider the twopionexchange effect in the weak transition potential. Both the twonucleon induced decay mechanism and the final state interactions reduce the magnitude of the asymmetry. The quantum interference terms considered in the present microscopic approach give rise to an opposite behavior of the asymmetry with increasing energy cuts to that observed in models describing the nucleon final state interactions semiclassically via the intranuclear cascade code. Our results for the asymmetry parameter in $^{12}_{\Lambda}$C obtained with different potential models are consistent with the asymmetry measured at KEK.12/2011;  [Show abstract] [Hide abstract]
ABSTRACT: The decay of Λhypernuclei without π emission, known as NonMesonic Weak Decay (NMWD), gives an effective tool to investigate ΔS=1 fourbaryon interactions. It was theoretically suggested that the twonucleon induced mechanism could play a substantial role in reproducing the observed NMWD decay rates and nucleon spectra, but at present no direct evidence of such a mechanism has been obtained. The FINUDA experiment, exploiting the possibility to detect both charged and neutral particles coming from the hypernucleus decay, has allowed us to deduce the relative weight of the two nucleon induced decay rate to the total NMWD rate. The value of Γ2N/Γ=0.21±0.07stat0.02+0.03 has been deduced, well consistent with the previous determinations.Physics Letters B 06/2011; 701:556561. · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The decay of $\Lambda$hypernuclei without pion emission, known as Non Mesonic Weak Decay (NMWD), gives an effective tool to investigate $\Delta$S=1 fourbaryon interactions. It was theoretically suggested that the twonucleon induced mechanism could play a substantial role in reproducing the observed NMWD decay rates and nucleon spectra, but at present no direct evidence of such a mechanism has been obtained. The FINUDA experiment, exploiting the possibility to detect both charged and neutral particles coming from the hypernucleus decay, has allowed us to deduce the relative weight of the two nucleon induced decay rate to the total NMWD rate. The value of $\Gamma_{2N}$/$\Gamma_{NMWD}$=0.24$\pm$${0.03_{stat}}^{+0.03_{sys}}_{{{0.02_{sys}}}}$ has been deduced, with an error reduced by a factor more than two compared with the previous assessment.01/2011;  [Show abstract] [Hide abstract]
ABSTRACT: A consistent microscopic diagrammatic approach is applied for the first time to the calculation of the nucleon emission spectra in the nonmesonic weak decay of Λhypernuclei. We adopt a nuclear matter formalism extended to finite nuclei via the local density approximation, a onemeson exchange weak transition potential and a Bonn nucleon–nucleon strong potential. Ground state correlations and final state interactions, at second order in the nucleon–nucleon interaction, are introduced on the same footing for all the isospin channels of one and twonucleon induced decays. Single and doublecoincidence nucleon spectra are predicted for 12ΛC and compared with recent KEK and FINUDA data. The key role played by quantum interference terms allows us to improve the predictions obtained with intranuclear cascade codes. Discrepancies with data remain for proton emission.Physics Letters B 01/2011; · 4.57 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The ratio Nnn/Nnp between the number of neutron–neutron and neutron–proton pairs emitted in the non–mesonic weak decay of Λ–hypernuclei is calculated within a nuclear matter formalism extended to via the local density approximation. The single–nucleon emission spectra, Np and Nn, are also evaluated. Our formalism takes care of both ground state correlations (gsc) and final state interactions (FSI). The evaluation of Nnn/Nnp — which, unlike Γn/Γp≡Γ(Λn→nn)/Γ(Λp→np), is an actual observable quantity in non–mesonic decay — is performed within a fully microscopic model where a proper treatment of FSI, gsc and ground state normalization is considered. All the isospin channels contributing to one– and two–nucleon induced decays are included. Our final result for the coincidence number ratio, Nnn/Nnp=0.374, is in agreement with the KEK–E508 datum, exp(Nnn/Nnp)=0.40±0.10.Nuclear Physics A 02/2010; · 2.50 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Single and double coincidence nucleon spectra in the weak decay of Λhypernuclei are studied within a nuclear matter formalism extended to finite nuclei via the local density approximation. With respect to previous calculations, the present work adopts a unified microscopic approach for both the one and twobody induced mechanisms, including the channels Λnn→nnn and Λpp→npp in addition to the mode Λnp→nnp already considered in earlier phenomenological studies. The propagation of the final nucleons in the residual nucleus is simulated by an intranuclear cascade code. Through the comparison of our predictions with 12ΛC KEK nucleon coincidence data obtained with a nucleon kinetic energy threshold of 30 MeV and an opening angle region we determine Γn/Γp=0.66±0.24. We find that the value of Γn/Γp extracted from single nucleon distributions is strongly affected by final state interaction effects. Some discrepancies between measured and calculated proton spectra are also pointed out.Nuclear Physics A 01/2010; · 2.50 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A theoretical review is presented of hypernuclear weak decay, with special emphasis on the non–mesonic modes. We focus on recent progress which lead to the solution of long–standing puzzles on the Γn/Γp ratio and on the asymmetry parameter. Perspectives for the future are also indicated.Nuclear Physics A 01/2010; 835(1):144151. · 2.50 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We discuss the problem of finding the most favorable conditions for closing the detection loophole in a test of local realism with a Bell inequality. For a generic nonmaximally entangled twoqubit state and two alternative measurement bases we apply Hardy's proof of nonlocality without inequality and derive an Eberhardlike inequality. For an infinity of nonmaximally entangled states we find that it is possible to refute local realism by requiring perfect detection efficiency for only one of the two measurements: the test is free from the detection loophole for any value of the detection efficiency corresponding to the other measurement. The maximum tolerable noise in a loopholefree test is also evaluated. Comment: 4 pages, 2 figures12/2009;  [Show abstract] [Hide abstract]
ABSTRACT: New spectra from the FINUDA experiment of the NonMesonic Weak Decay (NMWD) proton kinetic energy for , , , , and are presented and discussed along with the published data on and .Exploiting the large mass number range and the low energy threshold (15 MeV) for the proton detection of FINUDA, an evaluation of both Final State Interactions (FSI) and the twonucleon induced NMWD contributions to the decay process has been done. Based on this evaluation, a linear dependence of FSI on the hypernuclear mass number A is found and for the twonucleon stimulated decay rate the experimental value of Γ2/Γp=0.43±0.25 is determined for the first time. A value for the twonucleon stimulated decay rate to the total decay rate Γ2/ΓNMWD=0.24±0.10 is also extracted.Physics Letters B. 10/2009;  [Show abstract] [Hide abstract]
ABSTRACT: The contribution of groundstate correlations (GSCs) to the nonmesonic weak decay of Λ12C and other medium to heavy hypernuclei is studied within a nuclearmatter formalism implemented in a localdensity approximation. We adopt a weak transition potential including the exchange of the complete octets of pseudoscalar and vector mesons, as well as a residual strong interaction modeled on the Bonn potential. Leading GSC contributions, at first order in the residual strong interaction, are introduced on the same footing for all isospin channels of one and twonucleon induced decays. Together with fermion antisymmetrization, GSCs turn out to be important for an accurate determination of the decay widths. Besides opening the twonucleon stimulated decay channels, for Λ12C GSCs are responsible for 14% of the rate Γ1 while increasing the Γn/Γp ratio by 4%. Our final results for Λ12C are ΓNM=0.98, Γn/Γp=0.34, and Γ2/ΓNM=0.26. The saturation property of ΓNM with increasing hypernuclear mass number is clearly observed. The agreement with data of our predictions for ΓNM, Γn/Γp, and Γ2 is rather good.Physical Review C 07/2009; 81(6). · 3.72 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The contribution of Pauli exchange terms to the twonucleon induced nonmesonic weak decay of hypernuclei, ΛNN→nNN (N=n or p), is studied within a nuclear matter formalism implemented in a local density approximation. We have adopted a weak transition potential including the exchange of the complete octets of pseudoscalar and vector mesons as well as a residual strong interaction modeled on the Bonn potential. Among the exchange contributions, only the dominant ones have been evaluated microscopically from the corresponding Goldstone diagrams; a Landau–Migdal model has been adopted for the remaining exchange terms. The introduction of exchange terms turns out to reduce the twonucleon induced nonmesonic rate by 18% and, jointly with an increase in the onenucleon induced rate by the same magnitude, reveals to be significant for an accurate determination of the full set of hypernuclear nonmesonic decay widths in theoretical and experimental analyses.Nuclear Physics A 01/2009; · 2.50 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The physics of the weak decay of hypernuclei is briefly reviewed from a theoretical point of view. Special regard is devoted to the recent progress concerning the determination of the nonmesonic decay widths and the asymmetry parameters. Convincing evidence has been achieved for a solution of the longstanding puzzle on the ratio Γn/Γp. Very recently, it has been shown that the exchange of a ππ pair in the weak mechanism plays a crucial role in explaining the discrepancies between theory and experiment on the decay asymmetries.Nuclear Physics A 01/2008; · 2.50 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We illustrate two basic aspects of quantum mechanics applied to the neutral kaon system. A quantitative formulation of Bohr's complementarity principle is first described for the free space evolution of single kaons and entangled kaon pairs. We then show that the neutral kaon system is also suitable for an optimal demonstration of the 'quantum eraser', including its operation in the 'delayed choice' mode.AIP Conference Proceedings 12/2007; 962(1). 
Article: Quantum Mechanics with Neutral Kaons
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ABSTRACT: We briefly illustrate a few tests of quantum mechanics which can be performed with entangled neutral kaon pairs at a Phifactory. This includes a quantitative formulation of Bohr's complementarity principle, the quantum eraser phenomenon and various forms of Bell inequalities.Acta Physica Polonica Series B 04/2007; · 1.01 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The physics of the weak decay of hypernuclei is briefly reviewed from a theoretical point of view. Special regard is devoted to the recent progress concerning the determination of the nonmesonic decay widths and the asymmetry parameters. While convincing evidence has been achieved for a solution of the longstanding puzzle on the ratio Gamma_n/Gamma_p, the discrepancies between theory and experiment on the decay asymmetries clearly highlight the exigence of dedicating further efforts in exploring new aspects of the dynamics underlying the nonmesonic weak decay.02/2007;  [Show abstract] [Hide abstract]
ABSTRACT: The use of the Boson Loop Expansion is proposed for investigating the static properties of nuclear matter. We explicitly consider a schematic dynamical model in which nucleons interact with the scalar–isoscalar σ meson. The suggested approximation scheme is examined in detail at the mean field level and at the one and twoloop orders. The relevant formulas are provided to derive the binding energy per nucleon, the pressure and the compressibility of nuclear matter. Numerical results of the binding energy at the oneloop order are presented for Walecka’s σω model in order to discuss the degree of convergence of the Boson Loop Expansion.Annals of Physics 02/2007; · 3.32 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The nonmesonic weak decay of Λhypernuclei is studied within a onemesonexchange potential supplemented by a chirally motivated twopionexchange mechanism. The effects of final state interactions on the outgoing nucleons are also taken into account. Particular attention is payed to the asymmetry of the protons emitted by polarized hypernuclei. The onemesonexchange model describes the nonmesonic rates and the neutrontoproton ratio satisfactorily but predicts a too large and negative asymmetry parameter. The twopion exchange mechanism modifies the strength and sign of some decay amplitudes. As a consequence, while the rates change moderately, the asymmetry parameter is strongly affected, acquiring values that lie well within the experimental observations.Physics Letters B 01/2007; · 4.57 Impact Factor
Publication Stats
513  Citations  
159.22  Total Impact Points  
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Institutions

1999–2012

Università degli Studi di Torino
 Department of Physics
Torino, Piedmont, Italy


2009–2010

National University of La Plata
 Departamento de Física
Eva Perón, Buenos Aires, Argentina


2002–2006

Autonomous University of Barcelona
 Department of Physics
Cerdanyola del Vallès, Catalonia, Spain 
Instituto de Estructura de la Materia
Madrid, Madrid, Spain


2002–2004

University of Barcelona
 Department of Structure and Constituents of Matter
Barcino, Catalonia, Spain


2000

University of Oxford
Oxford, England, United Kingdom
