How long can a neutron live?

Hello, my name is Fangchen Li. This summer I’m working with Professor Crawford on a Neutron lifetime research. We are part of a research group. This group is trying to design an in-beam experiment to measure neutron lifetime.
Neutrons in stable nuclei can exist forever; a free neutron can last for about 15 minutes before decaying to a proton, an electron, and an antineutrino. People’ve done two experiments to measure this quantity. One is the bottle method. A certain number of neutrons are placed in a container. After a fixed time, people open the container and count how many neutrons are left. And another method is called the beam method. As a beam of neutrons passes through a particular volume of space, the number of neutrons decay to a proton can be measured. Then we can calculate neutron lifetime from this number.

But the beam and the bottle experiments do not agree. Our group is trying to improve the beam experiment to get a better measurement. Professor Crawford and I are working on developing Matlab programs to simulate the beam experiment. We use Monte Carlo Method to simulate neutrons. Then we trace each neutron as it goes through the experimental apparatus. In a computer simulation, we can easily find out how the results change as we vary the experiment setup.

So what am I doing every day? I sit in front of my computer, write code, and test my code.


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