What is Decay: Definition and 999 Discussions

In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For example, beta decay of a neutron transforms it into a proton by the emission of an electron accompanied by an antineutrino; or, conversely a proton is converted into a neutron by the emission of a positron with a neutrino in so-called positron emission. Neither the beta particle nor its associated (anti-)neutrino exist within the nucleus prior to beta decay, but are created in the decay process. By this process, unstable atoms obtain a more stable ratio of protons to neutrons. The probability of a nuclide decaying due to beta and other forms of decay is determined by its nuclear binding energy. The binding energies of all existing nuclides form what is called the nuclear band or valley of stability. For either electron or positron emission to be energetically possible, the energy release (see below) or Q value must be positive.
Beta decay is a consequence of the weak force, which is characterized by relatively lengthy decay times. Nucleons are composed of up quarks and down quarks, and the weak force allows a quark to change its flavour by emission of a W boson leading to creation of an electron/antineutrino or positron/neutrino pair. For example, a neutron, composed of two down quarks and an up quark, decays to a proton composed of a down quark and two up quarks.
Electron capture is sometimes included as a type of beta decay, because the basic nuclear process, mediated by the weak force, is the same. In electron capture, an inner atomic electron is captured by a proton in the nucleus, transforming it into a neutron, and an electron neutrino is released.

View More On Wikipedia.org
Recent contents Top users
  1. moenste

    Nuclear equation of the decay, decay constant, # of atoms

    Homework Statement A sample of iodine contains 1 atom of the radioactive isotope iodine 131 (131I) for every 5 * 107 atoms of the stable isotope iodine-127. Iodine has a proton number of 52 and the radioactive isotope decays into xenon 131 (131Xe) with the emission of a single negatively...
  2. S

    Alpha decay in elements under 35

    For a chemistry paper I'm writing, I have to include an example of alpha decay using only elements up to number 35, however, I can't find one that would actually work. Does anyone know of any that could be used?
  3. A

    B Why do radioactive materials decay in half-lifes?

    Why do radioactive materials decay in half-lifes exponential decay and not over mean time, i.e. like a Bell Curve
  4. Vitani11

    What is the energy of the decay photon towards the state....

    Homework Statement A certain molecule has a characteristic rotational energy of 8.81x10-4 eV. What is the energy of the decay photon towards the state with angular momentum quantum number l? Homework Equations E = Erot (L(L+1)) The Attempt at a Solution Why would this not be 12 multiplied by...
  5. O

    Calculate momentum, kinetic energy, speed etc. for a decay

    Homework Statement I have the decay K+ → μ+ + νμ Calculate: 1. Momentum of μ+ 2. Total energy of νμ 3. Mass of K+ 4. Speed of μ+ 5. Speed of νμ Homework Equations The only thing we get are the kinetic energy of μ+ so Kμ+ = 152.53 MeV and the mass of mμ+ = 105.658 MeV/c2 The Attempt at a...
  6. bubbadoobop

    A A Question about a Paper I recently read (about P+ decay)

    So I just read a paper called Fermion masses, mixings and proton decay in a Randall–Sundrum model (it's in Physics Letters B 498(3-4):256–262, but you can also find it at arXiv:hep-ph/0010195v2). Anyways, there us an equation in it [Pg. 8, 4.14] $$ \int \,dx^4 \int \,dy \sqrt{-g}...
  7. P

    Particle Decay After a Certain Distance

    Homework Statement A certain elementary particle lives only a time [T][/0] = 5 sec (proper time) before disintegrating. What velocity must the particle have if it is to reach the Earth from the Sun before disintegrating? Distance between the Earth and Sun is 1.5x10^11 meters.[/B]Homework...
  8. Vitani11

    Direction of alpha particles/protons from isotope decay

    Homework Statement A stationary B nucleus decays into two alpha particles and a proton, and the speed of the proton is found to be 6.0x10^6 m/s. What is the magnitude and direction of the velocities of the alpha particles with respect to the proton? Homework Equations Unnecessary The Attempt...
  9. A

    I Weak force - only free neutrons decay?

    Reading this article - http://hyperphysics.phy-astr.gsu.edu/hbase/particles/proton.html#c4 there is a statement - "A free neutron will decay with a half-life of about 10.3 minutes but it is stable if combined into a nucleus." So is it only free neutrons that decay into protons? In...
  10. C

    B Proton decay probability (Bayesian or frequentist?)

    If an event has probability occurring say 1/100000000000000000000000000000000 times.. if you do the experiment 100000000000000000000000000000000 times.. you are supposed to get the hit at least once? This is the proton decay experiment.. it's more than the above probability figure.. but if you...
  11. Elvis 123456789

    Another relativistic particle decay question

    Homework Statement Unstable particles cannot live very long. Their mean life time t is defined by N(t) = N0e−t/τ , i.e., after a time of t, the number of particles left is N0/e. (For muons, τ=2.2µs.) Due to time dilation and length contraction, unstable particles can still travel far if their...
  12. Elvis 123456789

    Relativistic particle decay

    Homework Statement Unstable particles cannot live very long. Their mean life time t is defined by N(t) = N0e−t/τ , i.e., after a time of t, the number of particles left is N0/e. (For muons, τ=2.2µs.) Due to time dilation and length contraction, unstable particles can still travel far if their...
  13. ohad

    A Are there BSM which do not predict proton decay?

    Hi, To my knowledge about BSM (which is not much), all of them require or predict proton decay. Do you know of some of them which do not? Thanks, Ohad
  14. R

    I What is the role of entropy in particle decay theory?

    Maybe my question is a bit more philosophical than scientific. In the macroscopic world entropy means that things become more chaotic and less orderly as they decay. It seems to me somewhat paradoxical that in the quantum world lower generation particles "decay" into the first generation...
  15. A

    I Alpha decay and magnetic fields

    How is the alpha decay of a given nucleus affected by the presence of an external electromagnetic field? It's probably an easier question that I think but I've been unable to find a treatment of the tunneling of the alpha particle using WKB method in the presence of a magnetic field.
  16. H

    B Linear amplitude decay function

    I collected data on a periodic mechanical motion. The amplitude is damped linearly. What mathematical function models linear amplitude decay. All I can find is exponential decay of a sine wave.
  17. durant35

    I Radioactive decay, macroscopic objects

    Radioactive decay is known to be a pure quantum effect, the particle from the nucleus is in a superposition until we measure it (according to collapse interpretations). In the Sch. cat experiment the radioactive particle gets entangled with a macroscopic object (Geiger counter) and so the...
  18. mfb

    Insights LHC Part 4: Searching for New Particles and Decays - Comments

    mfb submitted a new PF Insights post LHC Part 4: Searching for New Particles and Decays Continue reading the Original PF Insights Post.
  19. C

    A Proton Decay: The Mystery of Ergodicity

    Why does everyone assume that particles decay is an ergodic random process? After all T is not a symmetry of the Standard Model and I don't see any reason why ensamble averages should be equal to time averages.
  20. J

    I Spin and parity of pion decay

    Hi, I'm recently reading Krane's nuclear physics textbook, and in the meson physics chapter there is a section about the spin and parity of pions. He demonstrated a way to find out the parity of the pion by investigating a pion decay(as in the attached images). I think I understand what he's...
  21. L

    Radioactive decay, relation between binomial to expon. dist

    You can model the probability for radioactive decay as a Poisson distribution. This is the probability for radioactive decay within a specific time interval. (I probably got some of it wrong here). P(k,μ)=λ^k⋅exp(-μ)/k! Is there a way to use this formula to derive the other formula for...
  22. H

    I Radioactive decay, falling pencils and the uncertainty principle

    Consider an ensemble of identically prepared pencils balanced on its tip. If a pencil is precisely vertical, ##x=0##, and precisely at rest, ##p=0##, then it will never fall. But some pencils in the ensemble would fall, because according to the uncertainty principle, the standard deviation...
  23. S

    B Carbon-14 to Nitrogen-14 Decay: Proton Gain & No Electron Loss

    How Carbon-14 effectively gains a proton but no electrons when decaying to Nitrogen-14...?
  24. X

    I Find Lambda Baryon Decays Cross Section Ratio

    I've been asked to find the ratio between the cross sections of the two folowing decais: Using the CKM matrix and the feynman diagrams for both decays, I reach the conclusion that the Ratio is exactly 1. However, consulting this document...
  25. S

    I Is radioactive decay independent of the environment?

    Is the rate of radioactive decay fixed or does the environment have any impact eg would the rate of decay be the same in a low or very high gravitational field (in both cases measured from the viewpoint of the radioactive material)?
  26. entropy1

    I Is CPT symmetry violated in beta decay?

    I read that CP-symmetry violation occurs (or can occur) in beta decay. Does that mean that, since CPT-symmetry must hold, there is no T-symmetry?
  27. Quandry

    I Time Dilation Explained: Muon Decay & Reaching Earth

    As I understand it muons have a half life of 2.2 microseconds, thus, at the speed of light cannot get to the earth. But based on exponential decay, of every billion muons which head or way, about 70 will actually get here. Using time dilation the full billion will get here. Do we need a billion...
  28. O

    I How Bosons Decay: Exploring Particle Physics

    Hey! I'm studying some particle physics. I ran into this example of a gluon decaying into a u - anti-u pair. (According to example 9: http://teachers.web.cern.ch/teachers/archiv/HST2002/feynman/examples.htm) How come this happens via strong force. Why isn't a Z0 boson doing this instead? Thanks!
  29. victorhugo

    Experiment to simulate the radioactive decay of U-235

    Basic high-school homework. I mostly just want feedback on my answers and advice :) The experiment was to: Drop pins into a box. Pick out the one's upside down and count them and these are the ones that underwent decay. Get the ones that weren't upside down and throw them into the box again...
  30. T

    Predict whether a molecule will decay due to heat.

    I'm trying to understand the chemistry of stars. At what point do molecules really end? I guess there would be no one temperature where every molecule of hydrogen breaks apart in unison, but there should be an equation that says: if a diatomic gas is held together by 100 kJ/mol, at a...
  31. P

    Weak Decay of Nucleus: 3-Momentum Analysis

    Homework Statement An example of a weak decay of a nucleus is (Z, A) → (Z +1, A) + τ- + ντ-bar where (Z,A) represents a nucleus with Z protons and A−Z neutrons. (d) Suppose the gauge boson in the above process is produced at rest. Assuming the neutrino is massless, what must the 3-momenta of...
  32. P

    Calculate the energy of the neutrino in the following decay

    Homework Statement Stopped pions provide a useful mono-energetic source of neutrinos. For a pion at rest, calculate the energy of the neutrino in the decay $$\pi^+\rightarrow \mu^++\nu_{\mu}$$ You do not need to consider the subsequent decay of the ##\mu^+## and you can assume that the...
  33. C

    How do I determine if a certain nuclear decay is allowed?

    Hi, I am struggling with a question where they want me to determine whether or not three different decay are allowed. From what I have understood all decays must follow a set of conservation law. These laws are: 1 Conservation of Baryon number 2 Conservation of Lepton number 3 Conservation of...
  34. Hepth

    A Strategies for kinematics of a four-body decay?

    Does anyone have suggestions on the strategies for a four-body decay's kinematics? I'm just wondering what is out there. Last time I had to calculate something I just did it straightforward, but I know there must be other methods. (Like preferring to work in energies over invariants). I usually...
  35. N

    Atom charge after ionizing (nuclei/particle) radiation

    Homework Statement When an instable atom emits alpha or beta particles. Doesn't the overal electrical charge of the remaining atom change? For example when an atom emits alpha decay, a helium core is emitted, this results in the lose of two protons (forthe radiating atom). But doens't this mean...
  36. I

    Beta decay, electron capture Q value

    Homework Statement Find the ##Q## value for electron capture of ##^{196}Au##. Homework Equations ##Q_\epsilon = [m(^AX)-m(^AX')]c^2-B_n## The Attempt at a Solution How do I know if I have an ##K##- or ##L##-shell for the electron? Assuming I have an ##K## shell taking ##B_n = \; ^{196m1}Au##...
  37. C

    A Accelerating an electron in beta decay

    The electron created and emitted in the beta decay of a proton has an initial velocity close to the speed of light. When I try to calculate, not taking into account relativity, the force needed to accelerate an electron to that velocity over a distance the size of a proton, I get about 45 N...
  38. I

    Alpha decay ##Q##-value, recoil energy, momentum

    Homework Statement Calculate the ##Q##-value for ##^{230}Th\to \; 226Ra + \alpha##. Also calculate the kinetic energy and the velocity of the daughter nuclei. Homework Equations Alpha decay ##Q = (m_X-m_X'-m_\alpha)c^2## Kinetic energy ##T_\alpha = \frac{Q}{1+\frac{m_\alpha}{m_{X'}}}##...
  39. kiwaho

    I How can the e- escape by overcome the suck force in β- decay

    Not like decay of β+ or EC(electron capture), in β- decay, the nucleus positive charges definitely exerts strong suck force to negative charged electron, and the heavier the nuclide, the stronger the force! So, no coulomb barrier for β+/EC, but does for β- decay. How can the electron in a β-...
  40. kiwaho

    I Can electron beam accelerate electron capture beta decay?

    Some nuclides undergo decay of electron capture or beta plus. Can electron beam with appropriate energy accelerate electron capture beta decay? Same scenario: If I am looking for something, and my friend kindly hands it over to me, then I say thanks, because my seeking time is shorten.
  41. Kara386

    Kinetic energy of alpha particle in alpha decay

    Homework Statement Consider the nuclear decay 21486Rn → 21084Po2- + α. Calculate the Q for this decay, and give the value of the kinetic energy of the alpha particle in the rest frame of the Rn nuclide. The rest mass of the Rn nuclide is 213.9954u, of Po is 209.9829u, of α is 4.00015u and of...
  42. N

    I How to determine the energy of photons released in decay

    What equation would I need to use to determine the energy of photons released when radio-isotopes decay? I would like to figure out the energies of photons released when tritium and plutonium 237 decay.
  43. M

    A Decay of polarized particle into two spinless

    Hi All, I want to understand the decay of a spin-1 massive vector particle into two spinless massive particles. Given a massive vector particle V with spin Sz = +1, 0, -1 decays into 2 massive spinless particles. I have to compute the amplitude M but I don't know what should I do with the...
  44. F

    I Nonexistence or Feynman diagram of a decay

    Hi everyone! In an exam on particle physics there has been a problem where for a number of decays we were asked to either reason their non-existence (i.e. name a conservation law that it contradicts to) or draw a Feynman diagram. However, with one of those decays I have a problem: \gamma + p...
  45. O

    A Conservation of Information: Neutron Formation and Decay

    Has anyone analyzed the process of Neutron formation and decay from the perspective of "information conservation"? Does anyone have any thoughts on what the results of such an analysis would be? What is the status of the observed evidence of reality in respect of whether one should conclude...
  46. edguy99

    I Does the anti-neutron decay with same timing as a neutron?

    There is some discussion regarding the decay time of the neutron here for example. Has the decay time of the anti-neutron been predicted or seen to any degree of accuracy that could be compared to the decay times seen for the neutron? Is it expected to be the same?
  47. S

    B Neutral Pion Decay: Exploring Spin Conservation

    Hi everyone, I am curious about how a neutral pion decays in two photons. I don't understand how it is possible since the pion has spin = 1 and the photons have spin = 1 as well: doesn't this mean that spin is not conserved in this decay? What am I missing? Another question I have is about...
  48. C

    I Do more unstable elements decay faster than more stable ones?

    Do more unstable elements decay faster than more stable ones? Thanks!
  49. C

    I Can We Neglect Electron Binding Energies in Beta Decay Calculations?

    Hi, I was reading the wiki article here on beta decay and energy release: https://en.wikipedia.org/wiki/Beta_decay#Energy_release In obtaining a condition on the masses of the initial and final atoms we neglected the difference in electron binding energies of the two atoms. Does this mean we...
  50. amyy

    Why does 3H beta-decay to 3He?

    Homework Statement 3H has more tightly bound than 3He. Why is it, then, that 3H beta-decays to 3He? Homework Equations I also wonder what is the physical meaning of the value mass excess Δ(Z,A)≡[M(Z,A)-A]c2, or it is just for the convenience of calculations. The Attempt at a Solution B/A of...
Back
Top