Particle decay Definition and 68 Threads

Particle decay is the spontaneous process of one unstable subatomic particle transforming into multiple other particles. The particles created in this process (the final state) must each be less massive than the original, although the total invariant mass of the system must be conserved. A particle is unstable if there is at least one allowed final state that it can decay into. Unstable particles will often have multiple ways of decaying, each with its own associated probability. Decays are mediated by one or several fundamental forces. The particles in the final state may themselves be unstable and subject to further decay.
The term is typically distinct from radioactive decay, in which an unstable atomic nucleus is transformed into a lighter nucleus accompanied by the emission of particles or radiation, although the two are conceptually similar and are often described using the same terminology.

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  1. K

    What is the Speed of the CM Frame in Particle Decay?

    Homework Statement A particle of mass M, traveling horizontally through the laboratory, decays into two daughter particles, each of mass 0.4M. One of the daughters, A, is produced at rest in the Lab frame. Show that vcm , the speed with which the CM frame moves in the Lab frame, is equal...
  2. P

    Understanding Particle Decay and Momentum Conservation in Relativity

    I am answering a question about a particle decaying into two other particles and one needs to find the momentum of the children particles from the rest frame of the parent. I found a very helpful article on Wikipedia under 'Particle Decay', however I am really confused by their mathematical...
  3. H

    Why Alpha Particle Decay Q Leads to Lifetime Change

    Hi, I want to know why a small change in energy released, Q, in alpha particle decay leads to a large change in the lifetime. Also could anyone provide me with a link that shows a diagram of the energy spectrum of alpha particles. Thanks.
  4. T

    Special Relativity and Particle Decay

    Homework Statement A particle with rest mass M_0 can decay at rest into a pair of particles each with rest mass m_0. Calculate the following in the rest inertial frame of the original particle using M_0c^2=600MeV and m_0c^2=150 MeV . (i) The total energy of each particle produced in the...
  5. K

    Relativistic speed involving particle decay

    Homework Statement A particle of rest mass M0 is at rest in the laboratory when it decays into three identical particles, each of rest mass m. Two of the particles have velocity u1=-4/5c i(vector) u2=-3/5c j(vector) Calculate the direction and speed of particle 3Homework Equations pf-pi=0...
  6. K

    Energy released in particle decay w/ relativity

    One of the possible decay modes of the neutral kaon is K-> pion + pion The rest energies of the K0 and pion are 498 MeV and 135 MeV, respectively. The kaon is initially at rest when it decays. a) How much energy is released in the decay? b) What are the momentum and relative direction of...
  7. M

    Compute Breit-Wigner for particle decay

    Hey, I am just woondering if anyone here have computed (numerically) the Breit-Wigner for a particle decay. I have to do some nonlinear fitting of data but I need to compute this, any ideas? My case is specific, and I am brand new to particle physics, it's for a tau decay into Kaon, pion and...
  8. M

    How does a magnetic field affect the decay of a meson into charged pions?

    Homework Statement hello everybody I am new too these forums and am looking for a little help on a problem. I don't want anyone to give me the answer so i will just post the basic question and any help would be appreciated. If an uncharged meson decays into two charged pions in the presence...
  9. M

    Calculating Particle Decay in a Magnetic Field

    hello everybody I am new too these forums and am looking for a little help on a problem. I don't want anyone to give me the answer so i will just post the basic question and any help would be appreciated. If an uncharged meson decays into two charged pions in the presence of a magnetic field...
  10. S

    Kinetic Energies of Neutron and Pion After Lambda Hyperon Decay?

    Homework Statement A lambda hyperon \Lambda^{0} (mass = 1115.7 MeV/c^2) at rest in the lab frame decays into a neutron n (mass = 939.6 MeV/c^2) and a pion \pi^{0}: \Lambda^{0} \rightarrow n + \pi^{0} What are the kinetic energies (in the lab frame) of the neutron and pion after the decay...
  11. T

    Exploring Particle Decay Width Dependencies

    Is there a general dependence of some physical quantities for the decay width of any particles?
  12. F

    Calculating Particle Speed in a Relativistic Decay Scenario

    Homework Statement A particle with mass M decays into 2 particles of equal mass m. 1: Calculate the speed of the decay particles 2: Concider the case ρ->\Pi\Pi: M = 770 MeV and m\Pi= 140 MeV Homework Equations m = \gammam(restmass) ? The Attempt at a Solution I suppose M/2...
  13. N

    Energy conservation in particle decay

    two massive particles a finite distance from each other are bound to each other gravitationally, so if one disappeared the other one would have its energy altered, and the conservation of mass-energy would be broken. so what happens when a massive particle decays to a less massive particle...
  14. F

    Spin Polarization and Momentum in Particle Decay

    In an elementary particle decay, such as the decay of a positive pion into a positive muon and a muon neutrino, are the spin polarizations of either product always parallel (or anti-parallel) to their momentum? If so why?
  15. T

    Comprehensive List of Subatomic Particle Decay Modes and Probabilities

    Hello I'm looking for a list,as complete as possible, of decay modes and their probabilities, for all known subatomic particles. I've been googling, but found only bits and pieces. Perhaps someone knows a place on internet, or has found a free document to share, or anything like that thanks
  16. K

    Calculating Particle Decay Energies in Relativistic Systems

    Homework Statement A particle with momentum p0, mass m0 and energy E0 decays into two particles with mass m1 and m2. Find the energy of the particle E1 and E2. Homework Equations Four-momentum! The Attempt at a Solution I calculated the energy of particle 1 in S' (system where...
  17. S

    What are the factors that determine the different lifetimes of particle decays?

    I'm revising for an exam on particle physics and understand the lot, however I'd like clarification on the calculation of lifetimes of particles. I understand that particles decaying by the strong interaction last roughly 10^-23s because that is the minimum time that information can cross a...
  18. M

    Stationary particle decay into two particles with DIFFERENT masses

    I have been thinking and thinking this over, but I just can't find the solution - can anyone help? A particle of mass 7m which is initially at rest in the laboratory frame decays into two fragments whose rest masses are 2m and 3m. Find the energies of the fragments and their speeds in the lab...
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