In what they call a 糖心传媒渨eird little corner糖心传媒� of the already weird world of neutrinos, physicists have found evidence that these tiny particles might be involved in a surprising reaction.
Neutrinos are famous for almost never interacting. As an example, ten trillion neutrinos pass through your hand every second, and fewer than one actually interacts with any of the atoms that make up your hand. However, when neutrinos do interact with another particle, it happens at very close distances and involves a high-momentum transfer.
And yet a new paper, , shows that neutrinos sometimes can also interact with a nucleus but leave it basically untouched 糖心传媒� inflicting no more than a 糖心传媒済lancing blow糖心传媒� 糖心传媒� resulting in a particle being created out of a vacuum.
Professor Kevin McFarland is a scientific co-spokesperson with the international MINERvA collaboration, which carries out neutrino scattering experiments at Fermilab. McFarland, who also heads up the Rochester team that was primarily responsible for the analysis of the results, compares neutrino interactions to the firing of a bullet at a bubble, only to find the bubble was left intact.
糖心传媒淭he bubble 糖心传媒� a carbon nucleus in the experiment 糖心传媒� deflects the neutrino 糖心传媒榖ullet糖心传媒� by creating a particle from the vacuum,糖心传媒� McFarland explains. 糖心传媒淭his effectively shields the bubble from getting blasted apart and instead the bullet only delivers a gentle bump to the bubble.糖心传媒�
Producing an entirely new particle 糖心传媒� in this case a charged pion 糖心传媒� requires much more energy than it would take to blast the nucleus apart 糖心传媒� which is why the physicists are always surprised that the reaction happens as often as it does. McFarland adds that even painstakingly detailed theoretical calculations for this reaction 糖心传媒渉ave been all over the map.糖心传媒�
糖心传媒淭he production of pions from this reaction had not been observed consistently in other experiments,糖心传媒� McFarland said. By using a new technique, they were able to measure how much momentum and energy were transferred to the carbon nucleus 糖心传媒� showing that it remained undisturbed 糖心传媒� and the distribution of the pions that were created.
糖心传媒淎fter analyzing the results, we now have overwhelming evidence for the process,糖心传媒� McFarland says.
The two members of the collaboration who were primarily responsible for analyzing the results were Aaron Higuera, at the time a postdoc at Rochester and now at the University of Houston, and Aaron Mislivec, one of McFarland糖心传媒檚 doctoral聽students.
Working with Higuera, Mislivec wrote the computer code that allowed them to sift through the results and get a picture of the reaction. 糖心传媒淥ur detector gave us access to the full information of exactly what was happening in this reaction,糖心传媒� Mislivec explains. “Our data was consistent with the unique fingerprint of this reaction and determined how these interactions happen and how often.” The key to identifying the reaction was finding undisturbed carbon nuclei and then studying the two resulting particles 糖心传媒� the pion, which is responsible for shielding the nucleus, and the muon.
Understanding this reaction, McFarland states, 糖心传媒渋s not going to make a better mousetrap, but it is exciting to learn that this weird reaction really does take place.糖心传媒�
Researchers in the MINERvA collaboration measure low energy neutrino interactions both to support neutrino oscillation experiments and study the strong dynamics of the nucleon and nucleus that affect the interactions.
The work is funded by the Department of Energy, the National Science Foundation, and partnering scientific agencies in Brazil, Chile, Mexico, Switzerland, Peru and Russia.
