Publications (71)21.41 Total impact
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Article: Measurement of the analysing power and the differential cross-section of the $\overline{p}$p charge-exchange reaction at LEAR
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Article: Measurement of the analysing power of the charge-exchange $\overline{p}$p --> $\overline{n}$n reaction in the momentum range 546-875 MeV/c at LEAR
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Article: Final results of an experimental study of a large-area planar drift chamber filled with a He-based mixture
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ABSTRACT: This paper reports the final results of an accurate and complete experimental study of the performance of a large-area (1150 × 566 mm2) planar drift chamber filled with a HeiC4H10 (70−30%) mixture. Sixteen chambers of this type will constitute the elements of the central part of the tracking device of FINUDA, one of the two spectrometers approved for running at DAΦNE. The measured spatial resolution across the full drift cell ranges from 80 to 120 μm for particles at normal incidence angle, and the measured spatial resolution along the sense wire, as measured by the charge division method, was better than 1% of the wire length. Efficiency, space-time relationship, long term stability and Lorentz angle were measured as well. Particular care was devoted to the study of the spatial resolution as a function of the incidence angle. The conclusion of this study is that the chamber performances are the same or better than those obtained with Ar-based mixtures.Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. -
Article: p stopping power in hydrogen below 1 MeV and the p4He metastable state.
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ABSTRACT: The stopping power of H, for was measured in the energy interval 1 keV + 120 keV using a low density gas target ( being the Hz density at STP) with the OBELIX spectrometer at the LEAR of CEBN.Furthermore, the formation of metastable states in the interaction at rest, having a mean life of the order of 3 μs, was investigated at six target gas pressures (3 atm and 400,250,200,150,50 mbar). The influence of contaminants (like Ha, Ne, Ar, N2 and Xe) on the life of such metastable states was examined at the target gas pressure of 3 atm.Nuclear Physics A. -
Article: A search for axial vectors in pp → K±Kmiss0π∓π+π− annihilations at rest in gaseous hydrogen at NTP
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ABSTRACT: The study of the K±Kmiss0π∓π+π− channel (7016 events), from annihilations in a gaseous hydrogen target at NTP, with the OBELIX spectrometer at LEAR (CERN), is presented. A spin-parity analysis provides evidence for two axial vectors, one in the low mass region, the well established f1(1285), decaying to a0(980)π, the second, the 1++ component of the old puzzling , the f1(1420), decaying mainly to , seen for the first time in annihilation at rest. The analysis confirms the dominant production of the pseudoscalar η(1405), decaying mainly to , and the existence of a second pseudoscalar in the same mass region, the η(1460), decaying mainly to .Physics Letters B. -
Article: Measurement of the pp→π+π−andpp→K+K− annihilation frequencies in a 5 mb hydrogen gas target
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ABSTRACT: We report the first measurement of the K+K−, π+π− frequencies for annihilations at rest in a gaseous H2 target at low pressure (5 mbar). We have obtained: fππ = (4.26±0.11)×10−3, fKK = (0.46±0.03)×10−3. The ratio R = fKK/fππ has also been measured at a pressure of 2 mbar. Comparison with previous measurements shows that fKK decreases monotonically with the target density but its value at 5 mbar is still higher than the value with L X-ray in coincidence.Physics Letters B. -
Article: The antineutron beam at OBELIX
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ABSTRACT: The antineutron beam facility built for the OBELIX experiment is described. The set-up for producing antineutrons through the charge-exchange reaction of antiprotons on a liquid-hydrogen target, integrated with the whole detector apparatus, is illustrated. The technique for measuring the intensity of the beam and the energy of antineutrons is explained. Finally, the performances of the facility and its unique features for studying the nucleon-antinucleon dynamics as well as selected topics in meson spectroscopy are reported.Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. -
Article: Light baryon production in binary p̄d annihilation reactions at rest
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ABSTRACT: We report the study of light baryon production in two-prong annihilation reactions due to antiprotons stopping in gaseous deuterium and detected by the OBELIX spectrometer (LEAR, CERN). A clear signal of the Δ(1232) production in binary reactions was found in both annihilation channels: and . The annihilation probabilities for these reactions turned out to be Y=(1.01±0.08)×10−5 and Y=(1.12±0.20)×10−5, respectively. In addition, the annihilation probability for the prototype Pontecorvo reaction was measured with the best world statistics: Y=(1.46±0.08)×10−5.Physics Letters B. -
Article: Antiproton stopping power in hydrogen below 120 keV and the Barkas effect
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ABSTRACT: The simultaneous measurement of the spatial coordinates and times of p¯s annihilating at rest in a H2 target at very low density ρ (ρ/ρ0<10-2, ρ0 being the STP density) gives the possibility of evaluating the behavior of the p¯ stopping power in H2 at low energies (below 120 keV). It is different from that of protons (the Barkas effect). Moreover, it is shown that a rise at low-energy values (≲1 keV) is needed to agree with experimental data.Phys. Rev. A. 47(5). -
Article: Contribution from S and P waves in pp̄ annihilation at rest
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ABSTRACT: The annihilation frequencies of 19 annihilation reactions at rest obtained in different target densities are analysed in order to determine the values of the P-wave annihilation percentage at each target density and the average hadronic branching ratios from P- and S-states. Both the assumptions of linear dependence of the annihilation frequencies on the P-wave annihilation percentage of the protonium state and the approach with the enhancement factors of Batty are considered. Furthermore the cases of incompatible measurements are discussed.Nuclear Physics A. -
Article: A new measurement of the Pontecorvo reaction p + d → π− + p with the OBELIX spectrometer at LEAR
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ABSTRACT: Antinucleon-nucleus annihilations into two-body final states containing only one or no meson are unusual annihilations (Pontecorvo reactions), practically unexplored experimentally, with the exception of the channel , for which only two low-statistics measurements exist. Their physical interest lies in the possibility of exploring small-distance nuclear dynamics, in which an important role can be played by non-nucleonic degrees of freedom. A new measurement of the reaction rate at rest, performed with the OBELIX spectrometer at LEAR, with the best statistics up to now and a careful evaluation of systematic effects is reported, together with a critical analysis of the existing theoretical models. The measured branching ratio, which confirms the previous results, can represent a reference point for the studies in the field.Nuclear Physics A.
Top co-authors
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Institutions
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2007
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INFN - Istituto Nazionale di Fisica Nucleare
Frascati, Latium, Italy
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1994–2006
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Politecnico di Torino
Torino, Piedmont, Italy
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1990–1993
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Università degli studi di Cagliari
- Department of Physics
Cagliari, Sardinia, Italy
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