A neutral particle

PHYSICS · Multi-part · Fermi University Physics · Particle Physics & Quantum Fields · Particles, interactions and experiment · Particles, interactions and experiment

Particle Physics, Ch Hadrons: baryons, mesons and their quark content

Problem

A neutral particle, which leaves no track, decays into two oppositely charged tracks forming a "

V

", both identified from their curvature and energy loss as pions. Their measured energies sum to

E_{\text{tot}} = 608.4\,\mathrm{MeV}

, and the vector sum of their momenta has magnitude

|\mathbf{p}_{\text{tot}}|c = 350\,\mathrm{MeV}

. The decay point lies

L = 1.9\,\mathrm{cm}

from the point where the neutral particle was produced, measured in the laboratory frame. ((a)) Find the invariant mass

Mc^2

of the parent particle. ((b)) Using

\beta = |\mathbf{p}_{\text{tot}}|c/E_{\text{tot}}

and

\gamma = E_{\text{tot}}/(Mc^2)

, find the proper time

t_0

this parent lived before decaying, measured in its own rest frame. ((c)) State which of the four interactions is responsible for the decay, and name the parent particle together with its quark content and strangeness.

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