Comment on: "The interaction of neutrons with 7Be at BBN temperatures: Lack of Standard Nuclear Solution to the Primordial 7Li Problem" by M. Gai et al
aa r X i v : . [ nu c l - e x ] O c t Comment on: ”The interaction of neutrons with Be at BBNtemperatures: Lack of Standard Nuclear Solution to the“Primordial Li Problem” by M. Gai et al.
M. Paul, R. Dressler, U. K¨oster, and D. Schumann Racah Institute of Physics, Hebrew University, Jerusalem, Israel 91904 Paul Scherrer Institute, Villigen, Switzerland Institut Laue-Langevin, Grenoble, France
Abstract
The article recently published by M. Gai et al. claims to reach conclusions from a collaborativeexperiment dedicated to the study of the Be( n, α ) reaction. These claims were published withno authorization from key collaborators, including a PI of the experiment. The Authors of thepresent Comment reject the conclusions of M. Gai et et al. and condemn the scientific and ethicalmisconduct involved in their publication. A formal Comment, similarly expressing the Authors’rejection of these conclusions was submitted to EPJ Web of Conferences who published the abovearticle. Be( n, α ) as possiblybearing consequences in the resolution of the so-called “Primordial Lithium Problem” [3].An experiment aimed at the study of the above reaction was initiated, lead by PI’s M.P.(Hebrew University of Jerusalem, HUJ) and M. Gai (University of Connecticut, UC) underthe auspices of US-Israel Binational Science Foundation [4]. The experiment involved a widecollaboration of researchers from UC, Soreq Nuclear Research Center (SNRC, Israel), PaulScherrer Institute (PSI, Switzerland), Institut Laue-Langevin (ILL, France), HUJ, Trian-gle Universities Nuclear Laboratories (TUNL, Duke University, USA), Weizmann Instituteof Science (Israel), and CERN (Switzerland). The experiment itself was performed at theSoreq Applied Research Accelerator Facility (SARAF, SNRC) [5] using a Be target preparedspecifically for this purpose at PSI and the Liquid-Lithium Target [6, 7] designed and builtat SARAF by a HUJ-SARAF collaboration. The SARAF-LiLiT setup is known to producean intense yield ( ∼ × n/s) of quasi-Maxwellian neutrons in the range kT = 30 − α particles and discrimination from abun-dant protons from the Li( n, p ) reactions in the presence of the intense neutron and gammabackground and electromagnetic noise from the LiLiT apparatus. A preparation experimentdesigned to observe α particle tracks produced by neutrons from the B( n, α ) Li was per-formed at SARAF-LiLiT by the HUJ-SARAF groups in the frame of the BSF project. Theexperiment successfully demonstrated the feasibility of detection of α particles in this hostileenvironment with semi-quantitative results, nonetheless justifying a first experiment with a Be target. A number of calibration experiments were designed and performed by the UCgroup to characterize α and proton pits in a CR-39 detector. Irradiation runs with quasi-Maxwellian neutrons produced at LiLiT by the intense ( ∼ B (for proof of principle), B and Be (background) targets under different experimental conditions. Etching and scanningof the CR-39 plates were performed in part at HUJ and UC and for the scanning also atBar-Ilan University (in collaboration with A. Weiss, HUJ).In spite of the methodology described above, the Authors of the present Comment (theAuthors) are of the opinion that the SARAF-LiLiT failed to reach reliable or quantitativeresults. This assessment was repeatedly expressed to M. Gai by the Authors and spelled2ut by Schumann et al. [8]. We list below the severe flaws leading to our rejection of theconclusions of [1].1. The calibration experiments for α particles detected in the CR-39 track detectorspresented by M. Gai and collaborators in [1] and in other Conference contributions [9–11]display notable discrepancies. The source of these discrepancies is not clear and the arbitrarychoice of one set among the others, not confirmed by any additional independent calibrationexperiment, is considered unacceptable by the Authors and unfit for extraction of physicalinformation.2. The background present in the spectra of pit radii attributed to alpha particles fromthe Be( n, α ) reaction in the SARAF-LiLiT experiment (Fig. 2 in [1]) is considered by theAuthors unfit to identify a reliable signal and to extract quantitative information on thereaction cross section.3. M. Gai et al. claim in [1] to identify protons emitted in the same experiment bythe Be( n, p ) Li reaction and to determine the cross section of this reaction, based on acalibration shown in their Fig. 3. The spectrum of pit radii taken as calibration for protonsin their Fig. 3 is however a steep decreasing function of the radius. In these conditions, theinterval [0.8 µ m, 1.4 µ m] taken by Gai et al. as the radii region of interest for protons cannotlead to a quantitative determination of proton-induced pits. In fact, a recent publication ofthe same group [12] establishes the uncertainty of pit radius determination at 0.2 µ m, causedby temperature variations during the etching procedure: this uncertainty leads to a changeof one order of magnitude in assigned pits owing to the steepness of the calibration curve.A low efficiency of proton counting of 8.7%, determined with ambiguous uncertainty of 3%(relative uncertainty of 34%) [1] and 1.3% (relative uncertainty of 14%) [12], compoundsthe problem. The Authors reject the quantitative extraction of the Be( n, p ) cross sectionclaimed by Gai et al. in [1].The Authors express again and unequivocally their position that the above experimentfailed to achieve its goals and that in no circumstance it can be used to extract quantitativeinformation on a physical quantity such as a reaction cross section. The flawed approachtaken by M. Gai in the handling, interpretation and presentation of data culminated inhis unethical publication of results rejected and disavowed by key Collaborators. A normalcourse of action following an unsuccessful experiment or conflicting opinions between co-experimenters, neither an infrequent circumstance, is identifying and correcting their likely3auses and having a repeat trial. We regret that irreconcilable standpoints and unilateralsteps of M. Gai rendered collaboration with him unfeasible. They led a PI (M.P.) to withdrawfrom collaboration in his own experiment and key members to distance themselves fromfurther publications and prevented the pursuit of an interesting scientific project. [1] M. Gai, E. E. Kading, M. Hass, K. Nollett, S. Stern, T. Stora, and A. Weiss,EPJ Web of Conferences , 01007 (2020).[2] M. Gai, (2018), https://arxiv.org/abs/1812.09914.[3] B. D. Fields, Annu. Rev. Nucl. Part. Sci. , 47 (2011).[4] https://drive.google.com/file/d/1v71PhAld3WTyzkvwUT7Dhn7H8aI1_wMJ/view?usp=sharing .[5] I. Mardor, O. Aviv, M. Avrigeanu, D. Berkovits, A. Dahan, T. Dickel, I. Eliyahu, M. Gai,I. Gavish-Segev, S. Halfon, M. Hass, T. Hirsh, B. Kaiser, D. Kijel, A. Kreisel, Y. Mish-nayot, I. Mukul, B. Ohayon, M. Paul, A. Perry, H. Rahangdale, J. Rodnizki, G. Ron,R. Sasson-Zukran, A. Shor, I. Silverman, M. Tessler, S. Vaintraub, and L. Weissman,Eur. Phys. J. A , 91 (2018).[6] S. Halfon, A. Arenshtam, D. Kijel, M. Paul, L. Weissman, O. Aviv, D. Berkovits,O. Dudovitch, Y. Eisen, I. Eliyahu, G. Feinberg, G. Haquin, N. Hazenshprung,A. Kreisel, I. Mardor, G. Shimel, A. Shor, I. Silverman, M. Tessler, and Z. Yungrais,Rev. Sci. Instrum. , 056105 (2014).[7] M. Paul, M. Tessler, M. Friedman, S. Halfon, T. Palchan, L. Weissman, A. Arenshtam,D. Berkovits, Y. Eisen, I. Eliahu, G. Feinberg, D. Kijel, A. Kreisel, I. Mardor, G. Shimel,A. Shor, and I. Silverman, Eur. Phys. J. A , 44 (2019).[8] D. Schumann and R. Dressler, (2019), https://arxiv.org/abs/1904.03023v3.[9] E. E. Kading, M. Gai, M. Kahn, M. Lee, M. Tessler, M. Paul, A. Weiss, D. Berkovits,S. Halfon, D. Kijel, A. Kreisler, A. Shor, I. Silverman, L. Weissman, M. Hass, I. Mukul,E. A. Maugeri, R. Dressler, D. Schumann, S. Heinitz, T. Stora, and D. Ticehurst, (2015),https://indico.psi.ch/event/3671/.[10] E. E. Kading, M. Gai, M. Tessler, M. Paul, A. Weiss, D. Berkovits, S. Halfon, D. Ki-jel, A. Kreisel, A. Shor, I. Silverman, L. Weissman, M. Hass, I. Mukul, E. A. Maugeri,R. Dressler, D. Schumann, S. Heinitz, T. Stora, D. Ticehurst, and C. R. Howell, PS Conference Proceedings (2017), 14th International Symposium on Nuclei in the Cosmos(NIC2016).[11] M. Gai, (2017), https://agenda.infn.it/event/10834/contributions/5673/.[12] E. E. Kading, O. Aviv, I. Eliyahu, M. Gai, S. Halfon, M. Hass, C. Howell, D. Kijel, Y. Mish-nayot, I. Mukul, A. Perry, Y. Shachar, C. Seiffert, A. Shor, I. Silverman, S. Stern, T. Stora,D. Ticehurst, A. Weiss, and L. Weissman, Phys. Rev. Res. , 023279 (2020)., 023279 (2020).