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What is the difference between a mass state and an interaction state ?

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fpa2011
#1
Jun8-11, 09:54 AM
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I've encountered these terms a few times with no explanation, and googling around turns up absolutely nothing. Can anyone give me a brief description of the two terms, suitable for undergraduate level?
thanks.
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Bill_K
#2
Jun8-11, 11:39 AM
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I've never heard the terms used, but maybe a mass state is an eigenstate of H0 and an interaction state is an eigenstate of H0 + Hint.
vanhees71
#3
Jun8-11, 01:02 PM
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In which context have you heard these somewhat strange notions?

Perhaps you refer to mixing phenomena (nowadays mostly coming up in the context of neutrino oscillations), where the mass-eigen states are different from the charge-eigen states of the interaction in which these particles are involved? In the case of neutrinos the mass eigenstates that admit to define asymptotically free Fock states are different from the flavor-eigen states, i.e., an electron antineutrino (coming, e.g., from the beta decay of a neutron) is a superposition of antineutrino-mass eigenstates.

Longer known is the mixing of the quarks, where the corresponding unitary matrix which transforms from the flavor-eigen state basis to the mass-eigen state basis is named the CKM matrix (named after Cabibbo, Kobayashi, and Maskawa).

clem
#4
Jun8-11, 03:12 PM
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What is the difference between a mass state and an interaction state ?

Quote Quote by fpa2011 View Post
I've encountered these terms a few times with no explanation, and googling around turns up absolutely nothing. Can anyone give me a brief description of the two terms, suitable for undergraduate level?
thanks.
The terms are when their are two or more states that are connected by some, usually small, interaction.
The "mass state" in the linear combination of the states that propagates like a state with definite mass. The "interaction state" is the linear combination that is produced by some interation.

For example, two different neutral K meson states are produced in a strong interaction.
The "interaction states" are K_1 which decays to two pions, and K_2 which decays to three pions. The "mass states" are K_short and K_long which move at slightly different velocities with the same energy. The mass and interaction states are related by a 2X2 matrix, and this leads to oscillation between the K_1 and K_2 states.


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