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266 results on '"Kovoor, J"'

1. Status of experimental knowledge on the unbound nucleus $^{13}$Be

Author

Jones, K. L., Kovoor, J., and Kanungo, R.

Subjects
Nuclear Experiment, Nuclear Theory
Abstract

The structure of the unbound nucleus $^{13}$Be is important to understanding the Borromean, two-neutron halo nucleus $^{14}$Be. The experimental studies conducted over the last four decades are reviewed in the context of the beryllium chain of isotopes and some significant theoretical studies. One focus of this paper is the comparison of new data from a $^{12}$Be(d,p) reaction in inverse kinematics, which was analyzed using GEANT4 simulations and a Bayesian fitting procedure, with previous measurements. Two possible scenarios to explain the strength below 1~MeV above the neutron separation energy were proposed in that study: a single $p$-wave resonance, or a mixture of an $s$-wave virtual state with a weaker either $p$-wave or $d$-wave resonance. Comparisons of recent invariant mass and the (d,p) experiments show good agreement between the transfer measurement and the two most recent high-energy nucleon removal measurements., Comment: 10 pages 2 figures

Published
2023
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2. Structure Studies of $^{13}\text{Be}$ from the $^{12}$Be(d,p) reaction in inverse kinematics on a solid deuteron target

Author

Kovoor, J., Jones, K. L., Hooker, J., Vostinar, M., Kanungo, R., Pain, S. D., Alcorta, M., Allen, J., Andreoiu, C., Atar, L., Bardayan, D. W., Bhattacharjee, S. S., Blankstein, D., Burbadge, C., Burcher, S., Catford, W. N., Cha, S., Chae, K., Connolly, D., Davids, B., Esker, N. E., Garcia, F. H., Gillespie, S., Ghimire, R., Gula, A., Hackman, G., Hallam, S., Hellmich, M., Henderson, J., Holl, M., Jassal, P., King, S., Knight, T., Kruecken, R., Lepailleur, A., Liang, J., Morrison, L., O'Malley, P. D., Pereira-Lopez, X., Psaltis, A., Radich, A., Refsgaard, J., Shotter, A. C., Williams, M., and Workman, O.

Subjects
Nuclear Experiment
Abstract

The low-lying structure of $^{13}$Be has remained an enigma for decades. Despite numerous experimental and theoretical studies, large inconsistencies remain. Being both unbound, and one neutron away from $^{14}$Be, the heaviest bound beryllium nucleus, $^{13}$Be is difficult to study through simple reactions with weak radioactive ion beams or more complex reactions with stable-ion beams. Here, we present the results of a study using the $^{12}$Be(d,p)$^{13}$Be reaction in inverse kinematics using a 9.5~MeV per nucleon $^{12}$Be beam from the ISAC-II facility. The solid deuteron target of IRIS was used to achieve an increased areal thickness compared to conventional deuterated polyethylene targets. The Q-value spectrum below -4.4~MeV was analyzed using a Bayesian method with GEANT4 simulations. A three-point angular distribution with the same Q-value gate was fit with a mixture of $s$- and $p$-wave, $s$- and $d$-wave, or pure $p$-wave transfer. The Q-value spectrum was also compared with GEANT simulations obtained using the energies and widths of states reported in four previous works. It was found that our results are incompatible with works that revealed a wide $5/2^+$ resonance but shows better agreement with ones that reported a narrower width., Comment: 10 pages, 5 figures

Published
2023
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3. Use of Bayesian Optimization to Understand the Structure of Nuclei

Author

Hooker, J., Kovoor, J., Jones, K. L., Kanungo, R., Alcorta, M., Allen, J., Andreoiu, C., Atar, L., Bardayan, D. W., Bhattacharjee, S. S., Blankstein, D., Burbadge, C., Burcher, S., Catford, W. N., Cha, S., Chae, K., Connolly, D., Davids, B., Esker, N., Garcia, F. H., Gillespie, S., Ghimire, R., Gula, A., Hackman, G., Hallam, S., Hellmich, M., Henderson, J., Holl, M., Jassal, P., King, S., Knight, T., Kruecken, R., Lepailleur, A., Liang, J., Morrison, L., O'Malley, P. D., Pain, S. D., Pereira-Lopez, X., Psaltis, A., Radich, A., Shotter, A. C., Vostinar, M., Williams, M., and Workman, O.

Subjects
Physics - Computational Physics, Nuclear Experiment
Abstract

Monte Carlo simulations are widely used in nuclear physics to model experimental systems. In cases where there are significant unknown quantities, such as energies of states, an iterative process of simulating and fitting is often required to describe experimental data. We describe a Bayesian approach to fitting experimental data, designed for data from a $^{12}$Be(d,p) reaction measurement, using simulations made with GEANT4. Q-values from the $^{12}$C(d,p) reaction to well-known states in $^{13}$C are compared with simulations using BayesOpt. The energies of the states were not included in the simulation to reproduce the situation for $^{13}$Be where the states are poorly known. Both cases had low statistics and significant resolution broadening owing to large proton energy losses in the solid deuterium target. Excitation energies of the lowest three excited states in $^{13}$C were extracted to better than 90 keV, paving a way for extracting information on $^{13}$Be., Comment: 8 pages, 6 figures

Published
2021
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4. Use of Bayesian Optimization to understand the structure of nuclei

Author

Hooker, J, Kovoor, J, Jones, KL, Kanungo, R, Alcorta, M, Allen, J, Andreoiu, C, Atar, L, Bardayan, DW, Bhattacharjee, SS, Blankstein, D, Burbadge, C, Burcher, S, Catford, WN, Cha, S, Chae, K, Connolly, D, Davids, B, Esker, N, Garcia, FH, Gillespie, S, Ghimire, R, Gula, A, Hackman, G, Hallam, S, Hellmich, M, Henderson, J, Holl, M, Jassal, P, King, S, Knight, T, Kruecken, R, Lepailleur, A, Liang, J, Morrison, L, O’Malley, PD, Pain, SD, Pereira-Lopez, X, Psaltis, A, Radich, A, Shotter, AC, Vostinar, M, Williams, M, and Workman, O

Subjects
Affordable and Clean Energy, Bayesian optimization, Geant4 simulation, Low-energy reactions, Stable ion beam, Radioactive ion beam, Transfer reaction, Direct reaction, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Geochemistry, Interdisciplinary Engineering, Applied Physics
Abstract

Monte Carlo simulations are widely used in nuclear physics to model experimental systems. In cases where there are significant unknown quantities, such as energies of states, an iterative process of simulating and fitting is often required to describe experimental data. We describe a Bayesian approach to fitting experimental data, designed for data from a 12Be(d,p) reaction measurement, using simulations made with GEANT4. Q-values from the 12C(d,p) reaction to well-known states in 13C are compared with simulations using BayesOpt. The energies of the states were not included in the simulation to reproduce the situation for 13Be where the states are poorly known. Both cases had low statistics and significant resolution broadening owing to large proton energy losses in the solid deuterium target. Excitation energies of the lowest three excited states in 13C were extracted to better than 90 keV, paving a way for extracting information on 13Be.

Published
2022

5. Use of Bayesian Optimization to understand the structure of nuclei

Author

Hooker, J., Kovoor, J., Jones, K.L., Kanungo, R., Alcorta, M., Allen, J., Andreoiu, C., Atar, L., Bardayan, D.W., Bhattacharjee, S.S., Blankstein, D., Burbadge, C., Burcher, S., Catford, W.N., Cha, S., Chae, K., Connolly, D., Davids, B., Esker, N., Garcia, F.H., Gillespie, S., Ghimire, R., Gula, A., Hackman, G., Hallam, S., Hellmich, M., Henderson, J., Holl, M., Jassal, P., King, S., Knight, T., Kruecken, R., Lepailleur, A., Liang, J., Morrison, L., O’Malley, P.D., Pain, S.D., Pereira-Lopez, X., Psaltis, A., Radich, A., Shotter, A.C., Vostinar, M., Williams, M., and Workman, O.

Published
2022
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11. Structure studies of Be13 from the Be12(d,p) reaction in inverse kinematics on a solid deuteron target

Author

Kovoor, J., primary, Jones, K. L., additional, Hooker, J., additional, Vostinar, M., additional, Kanungo, R., additional, Pain, S. D., additional, Alcorta, M., additional, Allen, J., additional, Andreoiu, C., additional, Atar, L., additional, Bardayan, D. W., additional, Bhattacharjee, S. S., additional, Blankstein, D., additional, Burbadge, C., additional, Burcher, S., additional, Catford, W. N., additional, Cha, S., additional, Chae, K., additional, Connolly, D., additional, Davids, B., additional, Esker, N. E., additional, Garcia, F. H., additional, Gillespie, S., additional, Ghimire, R., additional, Gula, A., additional, Hackman, G., additional, Hallam, S., additional, Hellmich, M., additional, Henderson, J., additional, Holl, M., additional, Jassal, P., additional, King, S., additional, Knight, T., additional, Kruecken, R., additional, Lepailleur, A., additional, Liang, J., additional, Morrison, L., additional, O'Malley, P. D., additional, Pereira-Lopez, X., additional, Psaltis, A., additional, Radich, A., additional, Refsgaard, J., additional, Shotter, A. C., additional, Williams, M., additional, and Workman, O., additional

Published
2023
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24. Investigation of secondary γ -ray angular distributions using the N 15 (p,α1γ) C ∗ 12 reaction

Author

Deboer R. J., Boeltzig A., Macon K. T., Aguilar S., Gomez O., Frentz B., Henderson S. L., Kelmar R., Renaud M., Seymour G., Kolk B. V., Wiescher M., Brune C. R., Burcher S. P., Jones K. L., Kovoor J. M., Febbraro M., Imbriani G., Mosby S., Smith K., Toomey R., Deboer, R. J., Boeltzig, A., Macon, K. T., Aguilar, S., Gomez, O., Frentz, B., Henderson, S. L., Kelmar, R., Renaud, M., Seymour, G., Kolk, B. V., Wiescher, M., Brune, C. R., Burcher, S. P., Jones, K. L., Kovoor, J. M., Febbraro, M., Imbriani, G., Mosby, S., Smith, K., and Toomey, R.

Subjects
Experimental N nuclear Astrophysics
Abstract

The observation of secondary γ-rays provides an alternative method of measuring cross sections that populate excited final states in nuclear reactions. The angular distributions of these γ-rays also provide information on the underlying reaction mechanism. Despite the large number of data of this type in the literature, publicly available R-matrix codes do not have the ability to calculate these types of angular distributions. In this paper, the mathematical formalism derived by C. R. Brune and R. J. deBoer [Phys. Rev. C 102, 024628 (2020)2469-998510.1103/PhysRevC.102.024628] is implemented in the R-matrix code azure2 and calculations are compared with previous data from the literature for the N15(p,α1γ)C∗12 reaction. In addition, new measurements, made at the University of Notre Dame Nuclear Science Laboratory using the Hybrid Array of Gamma Ray Detectors (HAGRiD), are reported that span the energy range from Ep=0.88 MeV to Ep=4.0MeV. Excellent agreement between the data and the phenomenological fit is obtained up to the limit of the previous fit at Ep=2.0MeV and the R-matrix fit is extended from Ex≈13.5 MeV up to Ex≈15.3 MeV, where N15+p and C12+α reactions are fit simultaneously for the first time. An excellent reproduction of the N15(p,α1γ)C∗12 and C12(α,α)C12 data is achieved, but inconsistencies and difficulty in fitting other data are encountered and discussed.

Published
2021

27. Investigation of secondary γ -ray angular distributions using the N15(p,α1γ)C*12 reaction

Author

deBoer, R. J., primary, Boeltzig, A., additional, Macon, K. T., additional, Aguilar, S., additional, Gomez, O., additional, Frentz, B., additional, Henderson, S. L., additional, Kelmar, R., additional, Renaud, M., additional, Seymour, G., additional, Kolk, B. Vande, additional, Wiescher, M., additional, Brune, C. R., additional, Burcher, S. P., additional, Jones, K. L., additional, Kovoor, J. M., additional, Febbraro, M., additional, Imbriani, G., additional, Mosby, S., additional, Smith, K., additional, and Toomey, R., additional

Published
2021
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38. Cross-section measurements to low-lying excited final states in the Mg24(α,p)Al*27(γ) reaction as an energy source for x-ray bursts

Author

Ahn, T., primary, Aguilar, S., additional, deBoer, R. J., additional, Bardayan, D. W., additional, Boeltzig, A., additional, Brune, C. R., additional, Burcher, S. P., additional, Chae, K. Y., additional, Henderson, S. L., additional, Grzywacz, R. K., additional, Jones, K. L., additional, Kovoor, J. M., additional, Macon, K. T., additional, Manukyan, K., additional, Mosby, S., additional, O'Malley, P. D., additional, Renaud, M., additional, Smith, K., additional, Thornsberry, C., additional, Vande Kolk, B., additional, and Wiescher, M., additional

Published
2020
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40. Precision Measurements of the \(^{24}\text{Mg}(\alpha ,p\gamma )^{27}\text{Al}\) and \(^{27}\text{Al}(p,\alpha \gamma )^{24}\text{Mg}\) Cross Sections

Author

Ahn, T., primary, Aguilar, S., additional, deBoer, R. J., additional, Bardayan, D. W., additional, Boeltzig, A., additional, Brune, C. R., additional, Burcher, S. P., additional, Chae, K. Y., additional, Henderson, S. L., additional, Jin, S., additional, Jones, K. L., additional, Kovoor, J., additional, Macon, K. T., additional, Majumdar, A., additional, Manukyan, K., additional, Morales, L., additional, Mosby, S., additional, Moylan, S., additional, O’Malley, P. D., additional, Renaud, M., additional, Smith, K., additional, Tan, W., additional, Vande Kolk, B., additional, and Wiescher, M., additional

Published
2020
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41. Neurohydatidosis

Author

Kovoor, J ME, Thomas, R D, Chandrashekhar, H S, Jayakumar, P N, Pillai, S, and Shankar, S K

Published
2007

45. Safety and feasibility of carotid revascularization in patients with cerebral embolic strokes associated with carotid webs and histopathology revisited.

Author

Mathew, S, Davidson, Darrell D, Tejada, J, Martinez, M, and Kovoor, J

Subjects
CEREBRAL revascularization, TRANSIENT ischemic attack, ISCHEMIC stroke, HISTOPATHOLOGY, CAROTID endarterectomy, CAROTID artery
Abstract

Introduction: Carotid web is increasingly recognized as the cause of ischemic embolic strokes in younger patients. The best way to treat carotid web is debatable and carotid artery stenting (CAS) has been reported as a treatment for the carotid web in only a few case series. In this study we evaluate the safety and feasibility of CAS in symptomatic carotid webs and examined the histopathology of a carotid web. Materials and methods: At our institution between 2017 and 2019, 10 consecutive patients with symptomatic carotid webs were treated. We retrospectively analyzed the data for patient demographics, clinical presentation, imaging, treatment methodology and follow up. Results: All the patients had presented with ipsilateral embolic stroke. The mean age at presentation was 50 years (range 37–71) with seven female and three male patients. All patients underwent CAS except one patient who underwent carotid endarterectomy (CEA). In one stented patient, there was significant hypotension in the post-procedural period lasting a week. The patients were followed for a mean of 5.5 months (range one day-12 months). No recurrent stroke or transient ischemic attack (TIA) occurred. Surgical pathological studies confirmed fibromuscular dysplasia in one specimen. Conclusion: In our experience CAS for carotid web is feasible and safe in patients presenting with ischemic embolic strokes. [ABSTRACT FROM AUTHOR]

Published
2021
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