Coulomb and nuclear breakup of a halo nucleus 11Be

Breakup reactions of the one-neutron halo nucleus 11Be on Pb and C targets at about 70 MeV/u have been investigated by measuring the momentum vectors of the incident 11Be, outgoing 10Be, and neutron in coincidence. The relative energy spectra as well as the angular distributions of the 10Be+n center of mass have been extracted for both targets. For the breakup on Pb target, the selection of forward scattering angles is found to be effective to extract almost purely the first-order E1 Coulomb breakup component, and to exclude the nuclear contribution and higher-order Coulomb breakup components. This angle-selected energy spectrum is thus used to deduce the spectroscopic factor for the 10Be(0+) 2s_1/2 configuration in 11Be which is found to be 0.72+-0.04 with B(E1) up to Ex=4 MeV of 1.05+-0.06 e2fm2. The energy weighted E1 strength up to Ex=4 MeV explains 70+-10% of the cluster sum rule, consistent with the obtained spectroscopic factor. The non-energy weighted sum rule is used to extract the root mean square distance of the halo neutron to be 5.77(16) fm, consistent with previously known values. In the breakup with C target, we have observed the excitations to the known unbound states in 11Be at Ex=1.78 MeV and 3.41 MeV. Angular distributions for these states show the diffraction pattern characteristic of L=2 transitions, resulting in J^pi =(3/2,5/2)+ assignment for these states. We finally find that even for the C target the E1 Coulomb direct breakup mechanism becomes dominant at very forward angles.Comment: 14 pages, 7 figures, accepted for publication on Physical Review

Projectile fragmentation reactions and production of nuclei near the neutron drip-line

The reaction mechanism of projectile fragmentation at intermediate energies has been investigated observing the target dependence of the production cross sections of very neutron-rich nuclei. Measurement of longitudinal momentum distributions of projectile-like fragments within a wide range of fragment mass and its charge was performed using a hundred-MeV/n $^{40}$Ar beam incident on Be and Ta targets. By measurement of fragment momentum distribution, a parabolic mass dependence of momentum peak shift was observed in the results of both targets, and a phenomenon of light-fragment acceleration was found only in the Be-target data. The analysis of production cross sections revealed an obvious enhancement of the target dependence except target size effect when the neutron excess is increased. This result implies the breakdown of factorization (BOF) of production cross sections for very neutron-rich nuclei near the drip line.Comment: 16 pages, 18 figures, submitted to Phys. Rev.

Measurement of two-halo neutron transfer reaction p(11^{11}Li,9^{9}Li)t at 3AA MeV

The p(\nuc{11}{Li},\nuc{9}{Li})t reaction has been studied for the first time at an incident energy of 3$A$ MeV delivered by the new ISAC-2 facility at TRIUMF. An active target detector MAYA, build at GANIL, was used for the measurement. The differential cross sectionshave been determined for transitions to the \nuc{9}{Li} ground andthe first excited states in a wide range of scattering angles. Multistep transfer calculations using different \nuc{11}{Li} model wave functions, shows that wave functions with strong correlations between the halo neutrons are the most successful in reproducing the observation.Comment: 6 pages, 3 figures, submitted to Physical Review Letter

Approximations in Learning & Program Analysis

In this work we compare and contrast the approximations made in the problems of Data Compression, Program Analysis and Supervised Machine Learning. G\uf6del\u2019s Incompleteness Theorem mandates that any formal system rich enough to include integers will have unprovable truths. Thus non computable problems abound, including, but not limited to, Program Analysis, Data Compression and Machine Learning. Indeed, it can be shown that there are more non-computable functions than computable. Due to non- computability, precise solutions for these problems are not feasible, and only approximate solutions may be computed. Presently, each of these problems of Data Compression, Machine Learning and Program Analysis is studied independently. Each problem has it\u2019s own multitude of abstractions, algorithms and notions of tradeoffs among the various parameters. It would be interesting to have a unified framework, across disciplines, that makes explicit the abstraction specifications and ensuing tradeoffs. Such a framework would promote inter-disciplinary research and develop a unified body of knowledge to tackle non-computable problems. As a small step to that larger goal, we propose an Information Oriented Model of Computation that allows comparing the approximations used in Data Compression, Program Analysis and Machine Learning. To the best of our knowledge, this is the first work to propose a method for systematic comparison of approximations across disciplines. The model describes computation as set reconstruction. Non-computability is then presented as inability to perfectly reconstruct sets. In an effort to compare and contrast the approximations, select algorithms for Data Compression, Machine Learning and Program Analysis are analyzed using our model. We were able to relate the problems of Data Compression, Machine Learning and Program Analysis as specific instances of the general problem of approximate set reconstruction. We demonstrate the use of abstract interpreters in compression schemes. We then compare and contrast the approximations in Program Analysis and Supervised Machine Learning. We demonstrate the use of ordered structures, fixpoint equations and least fixpoint approximation computations, all characteristic of Abstract Interpretation (Program Analysis) in Machine Learning algorithms. We also present the idea that widening, like regression, is an inductive learner. Regression generalizes known states to a hypothesis. Widening generalizes abstract states on a iteration chain to a fixpoint. While Regression usually aims to minimize the total error (sum of false positives and false negatives), Widening aims for soundness and hence errs on the side of false positives to have zero false negatives. We use this duality to derive a generic widening operator from regression on the set of abstract states. The results of the dissertation are the first steps towards a unified approach to approximate computation. Consequently, our preliminary results lead to a lot more interesting questions, some of which we have tried to discuss in the concluding chapter

Study of the Hindrance Effect in Sub-barrier Fusion Reactions

We have measured the fusion cross sections of the 12C(13C, p)24Na reaction through off-line measurement of the beta-decay of 24Na using the beta-gamma coincidence method. Our new measurements in the energy range of Ec.m. = 2.6-3.0 MeV do not show an obvious S-factor maximum but a plateau. Comparison between this work and various models is presented.Comment: 3 pages, 3 figures, Talk at the "10th International Conference on Nucleus-Nucleus Collisions", Beijing, 16-21 August 200

The first direct measurement of ¹²C (¹²C,n) ²³Mg at stellar energies

Neutrons produced by the carbon fusion reaction ¹²C(¹²C,n)²³Mg play an important role in stellar nucleosynthesis. However, past studies have shown large discrepancies between experimental data and theory, leading to an uncertain cross section extrapolation at astrophysical energies. We present the first direct measurement that extends deep into the astrophysical energy range along with a new and improved extrapolation technique based on experimental data from the mirror reaction ¹²C(¹²C,p)²³Na. The new reaction rate has been determined with a well-defined uncertainty that exceeds the precision required by astrophysics models. Using our constrained rate, we find that ¹²C(¹²C,n)²³Mg is crucial to the production of Na and Al in Pop-III Pair Instability Supernovae. It also plays a non-negligible role in the production of weak s-process elements as well as in the production of the important galacti

Discovery of the Isotopes with 11 <= Z <= 19

A total of 194 isotopes with 11 $\le$ Z $\le$ 19 have been identified to date. The discovery of these isotopes which includes the observation of unbound nuclei, is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.Comment: to be pubslihed in At. Data Nucl. Data Table

Velocity-dependent transverse momentum distribution of fragments produced from ^<40>Ar+^9Be at 95 MeV/nucleon

Transverse momentum (P_T) distributions of projectilelike fragments produced at intermediate energy are investigated. P_T distributions of fragments with mass A_F=10-37, produced from an ^<40>Ar beam with E=95MeV/nucleon and a Be target, are observed as a function of fragment velocity by using the Rikagaku Kenkyusho (RIKEN) Projectile Fragment Separator at RIKEN. The width of PT distribution (σT) decreases monotonically with longitudinal momentum (PL). The decreasing trend shows a clear dependence on fragment mass. The observed σT is analyzed with a linear function and successfully reproduced by a parameter to characterize the decreasing trend. σT at the primary beam velocity shows good agreement with the Goldhaber formula, which is obtained on the basis of the contribution of the Fermi momentum. In contrast, the σT at the center of the PL distribution as determined by using the fits and parametrized energy loss in the fragmentation process is consistent with the width, which includes an additional contribution from the orbital deflection of the projectile. The antisymmetrized molecular-dynamics calculation indicates that the contribution of impact parameters is an important factor in understanding the behavior of the PT distribution. In addition, the practical formulation for σT obtained in the present study enables a reliable characterization of the fragments, which would be applicable to various research fields involving, for example, radioactive nuclear beams

Camptocormia in Parkinson's Disease

Objectives. Abnormalities of posture represent one of the main features of Parkinson's disease (PD). Among them, camptocormia has been considered as rare in PD. We investigated frequency and clinical features of camptocormia in PD patients. Methods. 153 PD patients (mean 68.5 ± 10.7 years old, duration 5.9 ± 2.4 years) outpatiently recruited. After neurologic examination, patients were rated on the Unified PD Rating Scale motor scale (UPDRS Part III), minimental state examination (MMSE). Also we evaluated patients with camptocormia by MRI. Of the 153 PD patients, 27 had camptocormia (mean age, 67.9 ± 7.9 years old; disease duration, 6.1 ± 3.9 years). For further evaluation, we recruited age- and sex-matched 27 PD patients without camptocormia (11 men and 16 women; mean age ±  SD, 69.2 ± 10.1 years, duration 6.0 ± 2.7 years) These selected 54 patients completed several self-assessments. Lumbar and thoracic paraspinal muscles were studied by EMG. Results. There were no significant differences in age, duration, severity, and drug dose between patients with and without camptocormia. Analysis of NMSS subitems indicated that PD patients tended to show lower scores for sleep/fatigue, attention/memory, and miscellaneous items. Conclusions. We found significant differences concerning nonmotor signs and symptoms evaluated by FAB, PDQ-8, FSQ, VAS-F, and NMSS between patients with and without camptocormia. Our findings indicate that camptocormia is a relatively common sign in PD and that patients with camptocormia scores on the PDQ-8 compared with PD patients without camptocormia. This suggests that improvements in camptocormia of PD patients may improve their QOL