ARGUS distribution

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In physics, the ARGUS distribution, named after the particle physics experiment ARGUS[1], is the probability distribution of the reconstructed invariant mass of a decayed particle candidate in continuum background. Its probability density function (not normalized) is:

f(x)=x\cdot\sqrt{1-\left(\frac{x}{c}\right)^2}\exp\left\{-\chi\cdot\left(1-\left(\frac{x}{c}\right)^2\right)\right\}\text{ for }x>0.

Sometimes a more general form is used to describe a more peaking-like distribution:

f(x)=x\cdot\left[1-\left(\frac{x}{c}\right)^2\right]^p\exp\left\{-\chi\cdot\left(1-\left(\frac{x}{c}\right)^2\right)\right\}

Here parameters c, χ, p represent the cutoff, curvature, and power (p = 0.5 gives a regular ARGUS) respectively.

[edit] References

  1. ^ ARGUS Collaboration, H. Albrecht, Phys. Lett. B 241, 278 (1990). In this paper, the function has been defined with parameter c representing the beam energy and parameter p set to 0.5. The normalization and the parameter χ have been obtained from data.
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