# Calculating Gamma Coincidence Likelihood

• nlieb
In summary, the conversation discusses the likelihood of two gamma rays hitting two detectors simultaneously as a function of the angle between the detectors and the source. The likelihood is affected by the size of the detector and the rate of gamma production. To observe this, the speaker suggests using Perturbed Angular Correlation Spectroscopy (PAC), which does not necessarily require very low temperatures. They also provide a link for further information on the subject. Overall, the conversation delves into the directional symmetry of gamma decays and how it can be observed through PAC.
nlieb
So we know gamma decays are directionally symmetric, but assume we have two detectors and we want to know the likelihood of two γs hitting each detector at the same time as a function of the angle between the line connecting the first detector and the source and the line connecting the second detector and the source. Assume the detectors are equidistant from the source. Obviously, the likelihood has to be related to the size of the detector and to the rate at which the γs are being produced, since if the detectors were infinitesimally sized the only coincidences would be either a result of two separate decays or would occur at $\theta$=$\pi$ radians. How might we go about doing this?

Check out Perturbed Angular Correlation Spectroscopy (PAC). I'll post a good link when I find one...

 Oh, I forgot: When you orient the nuclei, the gamma emissions are not isotropic (directionally symmetric) anymore. But you need very low (milliKelvin) temperatures for that.

To observe PAC you don't necessarily need very low temperatures. That you need only if you want to observe an asymmetry of the uncorrelated emissions.

This one is quite good, but you need a bit of background knowledge in condensed matter physics.

http://physik2.uni-goettingen.de/research/2_hofs/methods/pac

This one give more of the gory details.

http://www.ias.ac.in/pramana/v70/p835/fulltext.pdf

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## 1. What is gamma coincidence likelihood?

Gamma coincidence likelihood is a statistical method used to determine the probability that two or more gamma rays detected in a radiation experiment originated from the same nuclear event. It takes into account the timing and energy of the gamma rays to determine the likelihood of them being emitted from the same source.

## 2. How is gamma coincidence likelihood calculated?

The calculation of gamma coincidence likelihood involves comparing the energy and timing information of two or more gamma rays detected in a radiation experiment. This is usually done using computer software or specialized equipment that can measure and analyze the data. The likelihood is then determined based on the probability of the detected gamma rays originating from the same nuclear event.

## 3. What factors can affect gamma coincidence likelihood?

The accuracy of gamma coincidence likelihood calculations can be affected by several factors. These include the energy resolution and timing resolution of the detectors used, background radiation, and any potential errors in the experimental setup or data analysis. Additionally, the likelihood may be affected by the type of radiation source being used and the distance between the source and the detectors.

## 4. Why is gamma coincidence likelihood important in radiation experiments?

Gamma coincidence likelihood is important in radiation experiments because it allows scientists to distinguish between different types of radiation and accurately measure their energies. By determining the likelihood of gamma rays originating from the same source, researchers can better understand the properties of the nuclear events that produced them. This information can be useful in fields such as nuclear physics, medical imaging, and environmental monitoring.

## 5. Are there any limitations to using gamma coincidence likelihood?

While gamma coincidence likelihood is a useful tool in analyzing radiation data, it does have some limitations. These include the dependence on accurate timing and energy measurements, and the potential for errors due to background radiation or other experimental factors. Additionally, the likelihood may not be accurate for very low energy gamma rays or when multiple nuclear events occur in close succession. It is important for scientists to carefully consider these limitations when using gamma coincidence likelihood in their research.

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