Moshe Gai | University of Connecticut - Avery Point (original) (raw)
Papers by Moshe Gai
The cross section of the ^4He(^3He,gamma)^7Be reaction is of interest for understanding the produ... more The cross section of the ^4He(^3He,gamma)^7Be reaction is of interest for understanding the production of ^7Be solar neutrinos. We have chosen to study the cross section of this reaction with an implanted helium target. A number of implanted He targets were fabricated using thin (100 mu g/cm^2) aluminum foils using the TUNL low energy facility. The targets were tested with
Journal of Physics: Conference Series, 2016
Journal of Physics: Conference Series, 2015
Journal of Physics: Conference Series, 2012
AIP Conference Proceedings, 2006
ABSTRACT The ``world average'' of the astrophysical cross section factor , S17(0)... more ABSTRACT The ``world average'' of the astrophysical cross section factor , S17(0), is driven by the Seattle result due to the very small quoted uncertainty, which we however demonstrate it to be an overestimated accuracy. We propose more realistic error bars for the Seattle results based on the published Seattle data. This leads to a an uncertainty of the measured slope of S17 and thus an uncertainty due to extrapolation that can be reasonably estimated to be -3.0+0.0 eV-b.
AIP Conference Proceedings, 2008
The GSI1, GSI2 (as well as the RIKEN2 and the corrected GSI2) measurements of the Coulomb Dissoci... more The GSI1, GSI2 (as well as the RIKEN2 and the corrected GSI2) measurements of the Coulomb Dissociation (CD) of 8B are in good agreement with the most recent Direct Capture (DC) 7Be(p,gamma)8B reaction measurement performed at Weizmann and in agreement with the Seattle result. Yet it was claimed that the CD and DC results are sufficiently different and need to be reconciled. We show that these statements arise from a misunderstanding (as well as misrepresentation) of CD experiments. We recall a similar strong statement questioning the validity of the CD method due to an invoked large E2 component that was also shown to arise from a misunderstanding of the CD method. In spite of the good agreement between DC and CD data the slope of the astrophysical cross section factor (S17) can not be extracted with high accuracy due to discrepancies among the most recent DC data as well as a discrepancies among the three reports of the GSI CD data. The slope is directly related to the d-wave component that dominates at higher energies. This d-wave component must be subtracted from measured data to extrapolate to zero energy. Hence the uncertainty of the measured slope leads to an additional downward uncertainty (-3.0+0.0 eV-b) of the extrapolated zero energy cross section factor, S17(0). Such an uncertainty is also consistent with the smaller value of S17(0) extracted using the ANC method. This uncertainty must be alleviated by future experiments to allow a precise determination of S17(0), a goal that so far has not be achieved in spite of strong statement(s) that appeared in the literature.
Physics Letters B, 1977
ABSTRACT Systematic DeltaJ = 2 bands have been observed on the d5/2, g7/2 and h11/2 quasi-proton ... more ABSTRACT Systematic DeltaJ = 2 bands have been observed on the d5/2, g7/2 and h11/2 quasi-proton states in A = 117-127 odd-I nuclei. The DeltaJ = 2 energy spacings decrease (relative to the Te cores) as A decreases for the h1/2 band but not for the others. Also DeltaJ = 1 bands on unsually low-lying g9/2 proton-hole states exist.
AIP Conference Proceedings, 2004
No doubt, among the most exciting discoveries of the third millennium thus far are oscillations o... more No doubt, among the most exciting discoveries of the third millennium thus far are oscillations of massive neutrinos and dark energy that leads to an accelerated expansion of the Universe. Accordingly, Nuclear Physics is presented with two extraordinary challenges: the need for precise (5% or better) prediction of solar neutrino fluxes within the Standard Solar Model, and the need for an accurate (5% or better) understanding of stellar evolution and in particular of Type Ia super nova that are used as cosmological standard candle. In contrast, much confusion is found in the field with contradicting data and strong statements of accuracy that can not be supported by current data. We discuss an experimental program to address these challenges and disagreements.
AIP Conference Proceedings, 2004
The large value of \S17 = 22.1 \xpm 0.6 eV-b, reported by the Seattle group, suggests a larger to... more The large value of \S17 = 22.1 \xpm 0.6 eV-b, reported by the Seattle group, suggests a larger total \b8 solar neutrino flux. Together with the two high precision values quoted for \s34 it is either 20% or 9% larger than measured by SNO. While the accuracy of the Standard Solar Model has recently been revisited, precise nuclear inputs are still relevant, but a detailed examination of current data on \xs17 (as opposed to an examination of \S17 only) excludes quoting \S17 with sufficiently small uncertainty. In contrast to suggestions that \S17 is now known with the (impressive) accuracy of \xpm 3%, the exact value of \S17 is dependent on the choice of the data and the choice of theory used for extrapolation. In addition recent high precision results (including the Seattle data) on \xs17 which are in good agreement, still differ on the measured slopes, as does the theory, precluding an accurate extrapolation to zero energy of the consistent data. Using a common extrapolation of only the consistent high precision data, suggests a value of \S17 = 21.2 \xpm 0.5 eV-b, but a value equal to or smaller than 19.0 eV-b can not be excluded due to the uncertainty in the extrapolation, leading to an additional error of +0.0−3.0^{+0.0}_{-3.0}+0.0−3.0 eV-b. A proposal to remedy this situation is discussed.
Acta Physica Hungarica a Heavy Ion Physics, 2002
GeV beams of light ions and electrons are used for creating a high flux of real and virtual photo... more GeV beams of light ions and electrons are used for creating a high flux of real and virtual photons, with which some problems in Nuclear Astrophysics are studied. GeV 8B beams are used to study the Coulomb dissociation of 8B and thus the 7Be(p,gamma)8B reaction. This reaction is one of the major source of uncertainties in estimating the 8B solar neutrino flux and a critical input for calculating the 8B Solar neutrino flux. The Coulomb dissociation of 8B appears to provide a viable method for measuring the 7Be(p,gamma)8B reaction rate, with a weighted average of the RIKEN1, RIKEN2, GSI1 and MSU published results of S17(0) = 18.9 +/- 1.0 eV-b. This result however does not include a theoretical error estimated to be +/- 10 %. GeV electron beams on the other hand, are used to create a high flux of real and virtual photons at TUNL-HIGS and MIT-Bates, respectively, and we discuss two new proposals to study the 12C(alpha,gamma)16O reaction with real and virtual photons. The 12C(alpha,gamma)16O reaction is essential for understanding Type II and Type Ia supernova. It is concluded that virtual and real photons produced by GeV light ions and electron beams are useful for studying some problems in Nuclear Astrophysics.
Eprint Arxiv Nucl Ex 9707008, Jul 1, 1997
We dispute the alteration by Azuma et al. of the energy calibration of the Mainz('71) data on the... more We dispute the alteration by Azuma et al. of the energy calibration of the Mainz('71) data on the beta-delayed alpha-particle emission of 16N^{16}N16N as well as the very justification of the recalibration. We use the unaltered data to observe a pronounced disagreement between the TRIUMF('94) and Mainz('71) data sets on both the high and low energy sides of the primary peak (at 2.36 MeV) of the 16N^{16}N16N alpha-spectrum. We cannot support the dismissal of the Mainz('71) spectrum by the TRIUMF collaboration and emphasize the need to include it in R-matrix fits. We discuss the need for new improved data to resolve this disagreement and its implication for the extracted p-wave astrophysical S-factor of the 12C(alpha,gamma)16O^{12}C(\alpha,\gamma)^{16}O12C(alpha,gamma)16O reaction.
J Phys G Nucl Particle Phys, 1998
Contrary to claims that the problem has been solved, the astrophysical E1 S-factor of \c12ag is n... more Contrary to claims that the problem has been solved, the astrophysical E1 S-factor of \c12ag is not yet well known. R-Matrix analyses of elastic scattering data,\c12ag data, and data on the beta-delayed alpha-particle emission of N16 are not consistent and a small S-factor solution SE1(300) cannot be ruled out. In particular, data on the beta- delayed alpha-particle emission of N16 do not agree. The unaltered Mainz data do not agree with TRIUMF, but agree with both Seattle and Yale-UConn. The TRIUMF col- laboration has recalibratedthe Mainz('71) data; however, we dispute both the alteration of the Mainz data performed by the TRIUMF col- laboration and the very justification for the recalibration.
Nucl Phys a, 1998
We study the breakup reactions of 8B projectiles in high energy (50 and 250 MeV/u) collisions wit... more We study the breakup reactions of 8B projectiles in high energy (50 and 250 MeV/u) collisions with heavy nuclear targets (208Pb). The intrinsic nuclear wave functions are calculated using a simple model, as well as a simple optical potential. We demonstrate that nuclear effects are negligible and evaluate the contributions of various (E1, E2 and M1) multipolarities. A good agreement with measured data is obtained with insignificant M1 contribution (at 50 MeV/u) and very small E2 contribution.
![Research paper thumbnail of Comment on E2 Contribution to the 8B ---> p + 7Be Coulomb Dissociation Cross Section [K. Langanke and T.D. Shoppa, Phys. Rev. C49(1994)R1771, ER(1994)]](https://attachments.academia-assets.com/50590664/thumbnails/1.jpg)
](Phys Rev C, May 21, 1994
The E2 cross section calculated by Langanke and Shoppa for the Riken experiment on the Coulomb Di... more The E2 cross section calculated by Langanke and Shoppa for the Riken experiment on the Coulomb Dissociation of 8B uses E2 nuclear matrix elements from one specific model. Other nuclear models predict a considerably smaller E2 cross section (by a pproximately a factor of 3 to 4), and Langanke and Shoppa appear to assume the most optimistic scenario predicting large E2 cross section. We also note that Barker has already criticised the nuclear model used by Langanke and Shoppa. A MODEL INDEPENDENT Chi-Square analysis of the Riken data, suggest the best fit for the current Riken data is obtained with E1 amplitudes only. The upper limit (90% confidence) on the E2 component derived from our Chi-Square analysis is considerably smaller than used by Langanke and Shoppa. The MODEL DEPENDENT analysis of Langanke-Shoppa should not be considered as a correction to the Riken result, as claimed, and their quoted S17(0) is not substantiated.
In celebrating Iachello's 60th birthday we underline many seminal contributions for the study of ... more In celebrating Iachello's 60th birthday we underline many seminal contributions for the study of the degrees of freddom relevant for the structure of nuclei and other hadrons. A dipole degree of freedom, well described by the spectrum generating algebra U(4) and the Vibron Model, is a most natural concept in molecular physics. It has been suggested by Iachello with much debate, to be most important for understanding the low lying structure of nuclei and other hadrons. After its first observation in 18O it was also shown to be relevant for the structure of heavy nuclei (e.g. 218Ra). Much like the Ar-benzene molecule, it is shown that molecular configurations are important near threshold as exhibited by states with a large halo and strong electric dipole transitions. The cluster-molecular Sum Rule derived by Alhassid, Gai and Bertsch (AGB) is shown to be a very useful model independent tool for examining such dipole molecular structure near thereshold. Accordingly, the dipole strength observed in the halo nuclei such as 6He, 11Li, 11Be,17O, as well as the N=82 isotones is concentrated around threshold and it exhausts a large fraction (close to 100%) of the AGB sum rule, but a small fraction (a few percent) of the TRK sum rule. This is suggested as an evidence for a new soft dipole Vibron like oscillations in nuclei.
Phys Rev C, 2003
The absolute branching ratio of the β -delayed γ -ray emission of 18 N was measured, providing ab... more The absolute branching ratio of the β -delayed γ -ray emission of 18 N was measured, providing absolute normalization of the previous work by
Journal of Physics Conference Series, 2011
An Optical Readout Time Projection Chamber (O-TPC) operating with the gas mixture of CO2(80%) + N... more An Optical Readout Time Projection Chamber (O-TPC) operating with the gas mixture of CO2(80%) + N2(20%) at 100 torr with gamma beams from the HIγS facility of TUNL at Duke University were used to study the formation of carbon and oxygen during helium burning. Measurements were carried out with circularly polarized gamma-ray beams at energies: Eγ = 9.08, 9.38, 9.58, 9.78, 10.08, 10.38 and 10.68 MeV. We have begun the process of extracting complete angular distributions for the 16O(γ,α)12C reaction and the 12C(γ,3α) reaction (eventually with energy bins of approximately 100 keV) in order to determine the values of SE1, SE2 and the mixing phase phi12 of the 16O(γ, α)12C reaction. The rate of carbon formation at high temperatures (T > 3 GK) was suggested to increase due to contributions from a higher lying 2+ state. We have measured an angular distribution of (essentially) pure E2 transition at Eγ = 9.78 MeV of the 12C(γ, 3α) reaction, providing conclusive evidence for the elusive 2+2 state in 12C.
Acta Physica Hungarica a Heavy Ion Physics, 2004
The much needed nuclear input to the Standard Solar Model, S17(0)S_{17}(0)S17(0), has now been measured wit... more The much needed nuclear input to the Standard Solar Model, S17(0)S_{17}(0)S17(0), has now been measured with high precision ($\pm$5% or better) by different groups and good agreement is found, even when very different methods are employed. We review the decade long research program to measure the cross section of the 7Be(p,gamma)8B^7Be(p,\gamma)^8B7Be(p,gamma)8B reaction using the Coulomb dissociation method, including the pioneering RIKEN1 experiment carried out during March 1992, followed by RIKEN2, GSI1, GSI2 and an MSU experiment. Our RIKEN and GSI data allow us to rule out the much tooted large E2 contribution to the Coulomb dissociation of 8B^8B8B. Specifically recent results of the MSU experiment are not confirmed. The GSI1 and GSI2 high precision measurements are in good (to perfect) agreement with the newly published high precision measurements of direct capture with 7Be^7Be7Be targets. From these GSI-Seattle-Weizmann high precision data we conclude that the astrophysical cross section factor, S17(0)S_{17}(0)S17(0), is most likely in the range of 20 - 22 eV-b. We point out to an additional large uncertainty (-10% +3%) that still exists due to uncertainty in the measured slope of the S-factor and the theoretical extrapolation procedure which may still lower S17(0)S_{17}(0)S17(0) down to approximately 18.5 eV-b. For quoting S17(0)S_{17}(0)S17(0) with an uncertainty of pm\pmpm5% or better, yet another measurement needs to be performed at very low energies, as recently discussed by the UConn-Weizmann-LLN collaboration for the CERN/ISOLDE facility.
The E2 cross section calculated by Langanke and Shoppa (LS) for the RIKEN data on the Coulomb dis... more The E2 cross section calculated by Langanke and Shoppa (LS) for the RIKEN data on the Coulomb dissociation of â¸B, uses E2 matrix elements from a specific model that predicts large E2 component. But when all nuclear models are considered no large E2 is implied. The authors also note that Fred Barker has already criticized the nuclear model used by LS. In addition LS have incorrectly calculated the cross section, ignoring among other things the finite angular resolution of the RIKEN experiment. A chi-square model independent analysis of the RIKEN data (with angular averaging etc.) allow the authors to deduce an upper limit on the E2 component and exclude LS result (more than a factor of 2). The model dependent analysis of LS should not be considered as a correction to the RIKEN result, as claimed, and their so called quoted corrected Sââ(0) is not substantiated.
The cross section of the ^4He(^3He,gamma)^7Be reaction is of interest for understanding the produ... more The cross section of the ^4He(^3He,gamma)^7Be reaction is of interest for understanding the production of ^7Be solar neutrinos. We have chosen to study the cross section of this reaction with an implanted helium target. A number of implanted He targets were fabricated using thin (100 mu g/cm^2) aluminum foils using the TUNL low energy facility. The targets were tested with
Journal of Physics: Conference Series, 2016
Journal of Physics: Conference Series, 2015
Journal of Physics: Conference Series, 2012
AIP Conference Proceedings, 2006
ABSTRACT The ``world average'' of the astrophysical cross section factor , S17(0)... more ABSTRACT The ``world average'' of the astrophysical cross section factor , S17(0), is driven by the Seattle result due to the very small quoted uncertainty, which we however demonstrate it to be an overestimated accuracy. We propose more realistic error bars for the Seattle results based on the published Seattle data. This leads to a an uncertainty of the measured slope of S17 and thus an uncertainty due to extrapolation that can be reasonably estimated to be -3.0+0.0 eV-b.
AIP Conference Proceedings, 2008
The GSI1, GSI2 (as well as the RIKEN2 and the corrected GSI2) measurements of the Coulomb Dissoci... more The GSI1, GSI2 (as well as the RIKEN2 and the corrected GSI2) measurements of the Coulomb Dissociation (CD) of 8B are in good agreement with the most recent Direct Capture (DC) 7Be(p,gamma)8B reaction measurement performed at Weizmann and in agreement with the Seattle result. Yet it was claimed that the CD and DC results are sufficiently different and need to be reconciled. We show that these statements arise from a misunderstanding (as well as misrepresentation) of CD experiments. We recall a similar strong statement questioning the validity of the CD method due to an invoked large E2 component that was also shown to arise from a misunderstanding of the CD method. In spite of the good agreement between DC and CD data the slope of the astrophysical cross section factor (S17) can not be extracted with high accuracy due to discrepancies among the most recent DC data as well as a discrepancies among the three reports of the GSI CD data. The slope is directly related to the d-wave component that dominates at higher energies. This d-wave component must be subtracted from measured data to extrapolate to zero energy. Hence the uncertainty of the measured slope leads to an additional downward uncertainty (-3.0+0.0 eV-b) of the extrapolated zero energy cross section factor, S17(0). Such an uncertainty is also consistent with the smaller value of S17(0) extracted using the ANC method. This uncertainty must be alleviated by future experiments to allow a precise determination of S17(0), a goal that so far has not be achieved in spite of strong statement(s) that appeared in the literature.
Physics Letters B, 1977
ABSTRACT Systematic DeltaJ = 2 bands have been observed on the d5/2, g7/2 and h11/2 quasi-proton ... more ABSTRACT Systematic DeltaJ = 2 bands have been observed on the d5/2, g7/2 and h11/2 quasi-proton states in A = 117-127 odd-I nuclei. The DeltaJ = 2 energy spacings decrease (relative to the Te cores) as A decreases for the h1/2 band but not for the others. Also DeltaJ = 1 bands on unsually low-lying g9/2 proton-hole states exist.
AIP Conference Proceedings, 2004
No doubt, among the most exciting discoveries of the third millennium thus far are oscillations o... more No doubt, among the most exciting discoveries of the third millennium thus far are oscillations of massive neutrinos and dark energy that leads to an accelerated expansion of the Universe. Accordingly, Nuclear Physics is presented with two extraordinary challenges: the need for precise (5% or better) prediction of solar neutrino fluxes within the Standard Solar Model, and the need for an accurate (5% or better) understanding of stellar evolution and in particular of Type Ia super nova that are used as cosmological standard candle. In contrast, much confusion is found in the field with contradicting data and strong statements of accuracy that can not be supported by current data. We discuss an experimental program to address these challenges and disagreements.
AIP Conference Proceedings, 2004
The large value of \S17 = 22.1 \xpm 0.6 eV-b, reported by the Seattle group, suggests a larger to... more The large value of \S17 = 22.1 \xpm 0.6 eV-b, reported by the Seattle group, suggests a larger total \b8 solar neutrino flux. Together with the two high precision values quoted for \s34 it is either 20% or 9% larger than measured by SNO. While the accuracy of the Standard Solar Model has recently been revisited, precise nuclear inputs are still relevant, but a detailed examination of current data on \xs17 (as opposed to an examination of \S17 only) excludes quoting \S17 with sufficiently small uncertainty. In contrast to suggestions that \S17 is now known with the (impressive) accuracy of \xpm 3%, the exact value of \S17 is dependent on the choice of the data and the choice of theory used for extrapolation. In addition recent high precision results (including the Seattle data) on \xs17 which are in good agreement, still differ on the measured slopes, as does the theory, precluding an accurate extrapolation to zero energy of the consistent data. Using a common extrapolation of only the consistent high precision data, suggests a value of \S17 = 21.2 \xpm 0.5 eV-b, but a value equal to or smaller than 19.0 eV-b can not be excluded due to the uncertainty in the extrapolation, leading to an additional error of +0.0−3.0^{+0.0}_{-3.0}+0.0−3.0 eV-b. A proposal to remedy this situation is discussed.
Acta Physica Hungarica a Heavy Ion Physics, 2002
GeV beams of light ions and electrons are used for creating a high flux of real and virtual photo... more GeV beams of light ions and electrons are used for creating a high flux of real and virtual photons, with which some problems in Nuclear Astrophysics are studied. GeV 8B beams are used to study the Coulomb dissociation of 8B and thus the 7Be(p,gamma)8B reaction. This reaction is one of the major source of uncertainties in estimating the 8B solar neutrino flux and a critical input for calculating the 8B Solar neutrino flux. The Coulomb dissociation of 8B appears to provide a viable method for measuring the 7Be(p,gamma)8B reaction rate, with a weighted average of the RIKEN1, RIKEN2, GSI1 and MSU published results of S17(0) = 18.9 +/- 1.0 eV-b. This result however does not include a theoretical error estimated to be +/- 10 %. GeV electron beams on the other hand, are used to create a high flux of real and virtual photons at TUNL-HIGS and MIT-Bates, respectively, and we discuss two new proposals to study the 12C(alpha,gamma)16O reaction with real and virtual photons. The 12C(alpha,gamma)16O reaction is essential for understanding Type II and Type Ia supernova. It is concluded that virtual and real photons produced by GeV light ions and electron beams are useful for studying some problems in Nuclear Astrophysics.
Eprint Arxiv Nucl Ex 9707008, Jul 1, 1997
We dispute the alteration by Azuma et al. of the energy calibration of the Mainz('71) data on the... more We dispute the alteration by Azuma et al. of the energy calibration of the Mainz('71) data on the beta-delayed alpha-particle emission of 16N^{16}N16N as well as the very justification of the recalibration. We use the unaltered data to observe a pronounced disagreement between the TRIUMF('94) and Mainz('71) data sets on both the high and low energy sides of the primary peak (at 2.36 MeV) of the 16N^{16}N16N alpha-spectrum. We cannot support the dismissal of the Mainz('71) spectrum by the TRIUMF collaboration and emphasize the need to include it in R-matrix fits. We discuss the need for new improved data to resolve this disagreement and its implication for the extracted p-wave astrophysical S-factor of the 12C(alpha,gamma)16O^{12}C(\alpha,\gamma)^{16}O12C(alpha,gamma)16O reaction.
J Phys G Nucl Particle Phys, 1998
Contrary to claims that the problem has been solved, the astrophysical E1 S-factor of \c12ag is n... more Contrary to claims that the problem has been solved, the astrophysical E1 S-factor of \c12ag is not yet well known. R-Matrix analyses of elastic scattering data,\c12ag data, and data on the beta-delayed alpha-particle emission of N16 are not consistent and a small S-factor solution SE1(300) cannot be ruled out. In particular, data on the beta- delayed alpha-particle emission of N16 do not agree. The unaltered Mainz data do not agree with TRIUMF, but agree with both Seattle and Yale-UConn. The TRIUMF col- laboration has recalibratedthe Mainz('71) data; however, we dispute both the alteration of the Mainz data performed by the TRIUMF col- laboration and the very justification for the recalibration.
Nucl Phys a, 1998
We study the breakup reactions of 8B projectiles in high energy (50 and 250 MeV/u) collisions wit... more We study the breakup reactions of 8B projectiles in high energy (50 and 250 MeV/u) collisions with heavy nuclear targets (208Pb). The intrinsic nuclear wave functions are calculated using a simple model, as well as a simple optical potential. We demonstrate that nuclear effects are negligible and evaluate the contributions of various (E1, E2 and M1) multipolarities. A good agreement with measured data is obtained with insignificant M1 contribution (at 50 MeV/u) and very small E2 contribution.
Phys Rev C, May 21, 1994
The E2 cross section calculated by Langanke and Shoppa for the Riken experiment on the Coulomb Di... more The E2 cross section calculated by Langanke and Shoppa for the Riken experiment on the Coulomb Dissociation of 8B uses E2 nuclear matrix elements from one specific model. Other nuclear models predict a considerably smaller E2 cross section (by a pproximately a factor of 3 to 4), and Langanke and Shoppa appear to assume the most optimistic scenario predicting large E2 cross section. We also note that Barker has already criticised the nuclear model used by Langanke and Shoppa. A MODEL INDEPENDENT Chi-Square analysis of the Riken data, suggest the best fit for the current Riken data is obtained with E1 amplitudes only. The upper limit (90% confidence) on the E2 component derived from our Chi-Square analysis is considerably smaller than used by Langanke and Shoppa. The MODEL DEPENDENT analysis of Langanke-Shoppa should not be considered as a correction to the Riken result, as claimed, and their quoted S17(0) is not substantiated.
In celebrating Iachello's 60th birthday we underline many seminal contributions for the study of ... more In celebrating Iachello's 60th birthday we underline many seminal contributions for the study of the degrees of freddom relevant for the structure of nuclei and other hadrons. A dipole degree of freedom, well described by the spectrum generating algebra U(4) and the Vibron Model, is a most natural concept in molecular physics. It has been suggested by Iachello with much debate, to be most important for understanding the low lying structure of nuclei and other hadrons. After its first observation in 18O it was also shown to be relevant for the structure of heavy nuclei (e.g. 218Ra). Much like the Ar-benzene molecule, it is shown that molecular configurations are important near threshold as exhibited by states with a large halo and strong electric dipole transitions. The cluster-molecular Sum Rule derived by Alhassid, Gai and Bertsch (AGB) is shown to be a very useful model independent tool for examining such dipole molecular structure near thereshold. Accordingly, the dipole strength observed in the halo nuclei such as 6He, 11Li, 11Be,17O, as well as the N=82 isotones is concentrated around threshold and it exhausts a large fraction (close to 100%) of the AGB sum rule, but a small fraction (a few percent) of the TRK sum rule. This is suggested as an evidence for a new soft dipole Vibron like oscillations in nuclei.
Phys Rev C, 2003
The absolute branching ratio of the β -delayed γ -ray emission of 18 N was measured, providing ab... more The absolute branching ratio of the β -delayed γ -ray emission of 18 N was measured, providing absolute normalization of the previous work by
Journal of Physics Conference Series, 2011
An Optical Readout Time Projection Chamber (O-TPC) operating with the gas mixture of CO2(80%) + N... more An Optical Readout Time Projection Chamber (O-TPC) operating with the gas mixture of CO2(80%) + N2(20%) at 100 torr with gamma beams from the HIγS facility of TUNL at Duke University were used to study the formation of carbon and oxygen during helium burning. Measurements were carried out with circularly polarized gamma-ray beams at energies: Eγ = 9.08, 9.38, 9.58, 9.78, 10.08, 10.38 and 10.68 MeV. We have begun the process of extracting complete angular distributions for the 16O(γ,α)12C reaction and the 12C(γ,3α) reaction (eventually with energy bins of approximately 100 keV) in order to determine the values of SE1, SE2 and the mixing phase phi12 of the 16O(γ, α)12C reaction. The rate of carbon formation at high temperatures (T > 3 GK) was suggested to increase due to contributions from a higher lying 2+ state. We have measured an angular distribution of (essentially) pure E2 transition at Eγ = 9.78 MeV of the 12C(γ, 3α) reaction, providing conclusive evidence for the elusive 2+2 state in 12C.
Acta Physica Hungarica a Heavy Ion Physics, 2004
The much needed nuclear input to the Standard Solar Model, S17(0)S_{17}(0)S17(0), has now been measured wit... more The much needed nuclear input to the Standard Solar Model, S17(0)S_{17}(0)S17(0), has now been measured with high precision ($\pm$5% or better) by different groups and good agreement is found, even when very different methods are employed. We review the decade long research program to measure the cross section of the 7Be(p,gamma)8B^7Be(p,\gamma)^8B7Be(p,gamma)8B reaction using the Coulomb dissociation method, including the pioneering RIKEN1 experiment carried out during March 1992, followed by RIKEN2, GSI1, GSI2 and an MSU experiment. Our RIKEN and GSI data allow us to rule out the much tooted large E2 contribution to the Coulomb dissociation of 8B^8B8B. Specifically recent results of the MSU experiment are not confirmed. The GSI1 and GSI2 high precision measurements are in good (to perfect) agreement with the newly published high precision measurements of direct capture with 7Be^7Be7Be targets. From these GSI-Seattle-Weizmann high precision data we conclude that the astrophysical cross section factor, S17(0)S_{17}(0)S17(0), is most likely in the range of 20 - 22 eV-b. We point out to an additional large uncertainty (-10% +3%) that still exists due to uncertainty in the measured slope of the S-factor and the theoretical extrapolation procedure which may still lower S17(0)S_{17}(0)S17(0) down to approximately 18.5 eV-b. For quoting S17(0)S_{17}(0)S17(0) with an uncertainty of pm\pmpm5% or better, yet another measurement needs to be performed at very low energies, as recently discussed by the UConn-Weizmann-LLN collaboration for the CERN/ISOLDE facility.
The E2 cross section calculated by Langanke and Shoppa (LS) for the RIKEN data on the Coulomb dis... more The E2 cross section calculated by Langanke and Shoppa (LS) for the RIKEN data on the Coulomb dissociation of â¸B, uses E2 matrix elements from a specific model that predicts large E2 component. But when all nuclear models are considered no large E2 is implied. The authors also note that Fred Barker has already criticized the nuclear model used by LS. In addition LS have incorrectly calculated the cross section, ignoring among other things the finite angular resolution of the RIKEN experiment. A chi-square model independent analysis of the RIKEN data (with angular averaging etc.) allow the authors to deduce an upper limit on the E2 component and exclude LS result (more than a factor of 2). The model dependent analysis of LS should not be considered as a correction to the RIKEN result, as claimed, and their so called quoted corrected Sââ(0) is not substantiated.