The Atomki group has produced three previous papers on their beryllium-8 experiments — conference proceedings in 2008, 2012 and 2015. The first paper claimed evidence of a new boson of mass 12 MeV, and the second described an anomaly corresponding to a 13.45-MeV boson. (The third was a preliminary version of the Physical Review Letters paper.) The first two bumps have disappeared in the latest data, collected with an improved experimental setup. “The new claim now is [a] boson with a mass of 16.7 MeV,” Naviliat-Cuncic said. “But they don’t say anything about what went wrong in their previous claims and why we should not take those claims seriously.” One naturally wonders, he said, “Is this value that they quote now going to change in the next four years?”
In their papers and in an email, the Hungarian group expressed gratitude to Fokke de Boer, a Dutch physicist who led their experiments from 2001 to 2005. Naviliat-Cuncic’s sleuthing revealed that de Boer had been reporting anomalies in nuclear transitions and attributing them to missing bosons for decades, seldom replicating his results from one experiment to the next. In his years at Atomki, de Boer detected multiple anomalies in beryllium, carbon and oxygen nuclear transitions — evidence, he claimed, of “a pandemonium of more than 10 candidate bosons.”
When the team upgraded their experimental apparatus, the boson pandemonium disappeared. “He was very unhappy that we could not confirm his previous results with our new spectrometer,” said Attila Krasznahorkay, the current leader of the Atomki group. De Boer’s bosons failed to reappear in the group’s subsequent findings, but as they tweaked their instruments, they continued to strike upon new possibilities. This time, Krasznahorkay said, “We are very much confident about our experimental results.” De Boer, who died in 2010, was not involved in the new work.
When pressed, Krasznahorkay did not fully explain the disappearance of the earlier anomalies. He did not mention the 12-MeV bump and claimed that the 13.45-MeV bump was actually the 16.7-MeV one, incorrectly measured — a possibility that Naviliat-Cuncic considers unlikely when comparing the two bumps. Martin Savage, a cross-disciplinary nuclear and particle physicist at the University of Washington, agrees that the explanation seems unlikely, but said that even if it is true the unstated assumptions in the faulty 13.45-MeV measurement raise concerns. “If a scientific collaboration is making a claim about discovering a new particle, they are obligated to understand and estimate the systematic uncertainties associated with their measurements,” he said. “As far as the 12-MeV signal is concerned, they need to be able to explain exactly where that came from and why it is no longer present in order to convincingly demonstrate that they understand their apparatus.”
What Naviliat-Cuncic finds most astonishing about Krasznahorkay’s account of the past decade is his group’s failure to report any of their results that did not indicate new bosons; instead, they seemed to view these experiments as failures. “Is it not a rather flagrant (and naive) admission of a bias?” he said. Thaler explained, “The gold standard in particle physics is blind analysis, where you first decide what you are going to measure, you perform all cross-checks without looking at the final result, and you report the results regardless of the outcome.” Not doing so “sounds like cherry-picking evidence,” he said, which “can be a way to manufacture false positives.”