Yazar "Bertini, O." seçeneğine göre listele

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    Hypernuclear production cross section in the reaction of Li-6+C-12 at 2 A GeV
    (ELSEVIER SCIENCE BV, 2015) Rappold, C.; Saito, T. R.; Bertini, O.; Bianchin, S.; Bozkurt, V.; Kim, E.; Achenbach, P.
    Hypernuclear production cross sections have been deduced for the first time with induced reaction of heavy ion beam on fixed target and by means of the invariant mass method by the HypHI Collaboration exploiting the reaction of Li-6 C-12 at 2 A GeV or root S-NN = 2.70 GeV. A production cross section of 3.9 +/- 1.4 mu b for H-3(Lambda) and of 3.1 +/- 1.0 mu b for H-4(Lambda) respectively in the projectile rapidity region was inferred as well as the total production cross section of the Lambda hyperon was measured and found to be equal to 1.7 +/- 0.8 mb. A global fit based on a Bayesian approach was performed in order to include and propagate statistical and systematic uncertainties. Production ratios of H-3(Lambda)/H-4(Lambda), H-3(Lambda)/Lambda and H-4(Lambda)/Lambda were included in the inference procedure. The strangeness population fattors S-3 and S-4 of H-3(Lambda) and H-4(Lambda) respectively were extracted. In addition, the multiplicities of the Lambda hyperon, H-3(Lambda), and H-4(Lambda) together with the rapidity and transversal momentum density distributions of the observed hypemuclei were extracted and reported. (C) 2015 The Authors. Published by Elsevier B.V.
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    Hypernuclear spectroscopy of products from Li-6 projectiles on a carbon target at 2 A GeV
    (ELSEVIER SCIENCE BV, 2013) Rappold, C.; Kim, E.; Nakajima, D.; Saito, T. R.; Bertini, O.; Bianchin, S.; Achenbach, P.
    A novel experiment, aiming at demonstrating the feasibility of hypernuclear spectroscopy with heavy ion beams, was conducted. Using the invariant mass method, the spectroscopy of hypernuclear products of Li-6 projectiles on a carbon target at 2 A GeV was performed. Signals of the Lambda-hyperon and H-3(Lambda) and H-4(Lambda) hypernuclei were observed for final states of p + pi(-), He-3 + pi(-) and He-4 + pi(-), respectively, with significance values of 6.7, 4.7 and 4.9 sigma. By analyzing the proper decay time from secondary vertex distribution with the unbinned maximum likelihood fitting method, their lifetime values were deduced to be 262(-43)(+56) +/- 45 ps for Lambda, 183(-32)(+42) +/- 37 ps for H-3(Lambda), and 140(-33)(+48) +/- 35 ps for H-4(Lambda). (c) 2013 Elsevier B.V. All rights reserved.
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    On the measured lifetime of light hypernuclei H-3(Lambda) and H-4(Lambda)
    (ELSEVIER SCIENCE BV, 2014) Rappold, C.; Saito, T. R.; Bertini, O.; Bianchin, S.; Bozkurt, V.; Kavatsyuk, M.; Yoshida, K.
    A statistical combination of the experimental lifetime estimations available in the literatures is performed for H-3(Lambda) and H-4(Lambda), including several recent measurements. The combined average values of the lifetime for H-3(Lambda) and H-4(Lambda) are respectively 216(-16)(+19) ps and 192(-18)(+20) ps with a reduced chi(2) of 0.89 and 0.48. A new insight into the lifetime estimation of the HypHI Phase 0 experiment by a Bayesian approach is also presented. In this approach, several different prior distributions including the combination of previous lifetime data and a Jeffrey prior are used. The principal mode and the smallest credible interval at 68% of the posterior distribution, given by the prior belief of the previous measurements, are 217(-16)(+19) ps and 194(-18)(+20) ps respectively for H-3(Lambda) and H-4(Lambda). The two employed approaches have revealed that the lifetime of hypernuclei H-3(Lambda) and H-4(Lambda) can be shorter than the Lambda-hyperon lifetime. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
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    Search for evidence of (3)(Lambda)n by observing d + pi(-) and t + pi(-) final states in the reaction of Li-6+C-12 at 2A GeV
    (AMER PHYSICAL SOC, 2013) Rappold, C.; Kim, E.; Saito, T. R.; Bertini, O.; Bianchin, S.; Bozkurt, V.; Achenbach, P.
    The experimental data obtained from the reaction of Li-6 projectiles at 2A GeV on a fixed graphite target were analyzed to study the invariant mass distributions of d + pi(-) and t + pi(-). Indications of a signal in the d + pi(-) and t + pi(-) invariant mass distributions were observed with significances of 5.3 sigma and 5.0 sigma, respectively, when including the production target, and 3.7 sigma and 5.2 sigma, respectively, when excluding the target. The estimated mean values of the invariant mass for d + pi(-) and t + pi(-) signal were 2059.3 +/- 1.3 +/- 1.7 MeV/c(2) and 2993.7 +/- 1.3 +/- 0.6 MeV/c(2) respectively. The lifetime estimation of the possible bound states yielding to d + pi(-) and t + pi(-) final states were deduced to be as 181(-24)(+30) +/- 25 ps and 190(-35)(+47) +/- 36 ps, respectively. Those final states may be interpreted as the two-body and three-body decay modes of a neutral bound state of two neutrons and a Lambda hyperon, (3)(Lambda)n.
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    Summary of the HypHI Phase 0 experiment and future plans with FRS at GSI (FAIR Phase 0)
    (ELSEVIER SCIENCE BV, 2016) Saito, T. R.; Rappold, C.; Bertini, O.; Bianchin, S.; Bozkurt, V.; Geissel, H.; Oezel-Tashenov, B.
    Results of the HypHI Phase 0 experiment with the reaction of Li-6+C-12 at 2 A GeV are summarised. Invariant mass distributions as well as,the lifetime measurements for H-3(Lambda) and H-4(Lambda) are discussed. The lifetime values for both the hypernuclei are respectively observed to be 18(-32)(+42) ps and 140(-33)(+48) ps, being significantly shorter than those of the Lambda-hyperon. Statistical analyses of existing lifetime data for H-3(Lambda) up to 2014 confirm a significantly short lifetime of H-3(Lambda), which is not explained by present models. Observed hypernuclear production cross section values for H-3(Lambda) and H-4(Lambda) are also summarised. In addition, observed signals for the final states of d + pi(-) and t + pi(-) are discussed. All the discussions on the results of the HypHI Phase 0 experiment in this article are based on [1-4]. We also present a new proposed experiment with the FRS (FRagment Separator) at GSI (FAIR Phase 0) to improve the precision of the hypernuclear spectroscopy with peripheral heavy ion induced reactions. (C) 2016 Elsevier B.V. All rights reserved.