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.

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  1. S

    Slope of N - t graph of radioactive decay

    I am not really sure how to interpret the slope. The equation is: $$N=N_o e^{-\lambda t}$$ If the graph is N against t, then what is the slope? I can find the slope if the graph is log: $$log N=log N_o -\lambda t$$ So if the graph is log N against t, then the slope is ##-\lambda## But if...
  2. frhnsaif

    Radioisotope Decay Simulation in MCNP6

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  3. Sturm

    I Why Must a W Boson Always Decay into a Quark Anti Quark Pair of the Same Generation?

    Hi, i was wondering why a W Boson must always decay into a quark anti quark pair of the same generation. Why can it not for example decay into an up ant anti strange pair?
  4. T

    What does lambda in nuclear decay mean if it is big?

    I am thinking about lambda, the nuclear decay constant and what it actually means. I have built spreadsheet models looking at decay using lambda to determine the decay for each time period and then comparing the number left to that determined by using e ˆ- lamda x time. These are my...
  5. S

    Why is the Energy Released in Nuclear Decay Equal to the Change in Binding Energies?

    If we consider a nuclear decay in which element X decays into Y and an alpha particle, we can see that the total energy released is ##c^2(-m(\alpha) -m(y) + m(x))##. If we replace ##m(alpha)## with ##s(alpha) - be(\alpha)/c^2##, and similarly for the other particles, X and Y, we can see that...
  6. Z

    A Branching ratio for one decay channel

    hi, for studying one decay channel of particle - and measuring its decay width or life time - after this how do we proceed to find the branching ratio - do we need to find the decay width of all possible channel - because its possible even by experiment we are missing some possible decay...
  7. Z

    A How to find branching ratio after modelling Lagrangian?

    hi, we have learned that after modelling Lagrangian and extracting Feynman rules from it - we can find matrix element - from which decay width can be calculated - and than Branching ratio - my question is can we use some other way of calculatiing BR , or can we use our Lagrangain in our Euler...
  8. Vanadium 50

    I How do the collider experiments measure the mass of the W boson?

    A few months ago, there was a discussion on the W mass. It unfortunately degeneratd with posters attacking the honesty of the researchers. A pity, because we never got into the issues involved in making a sub 100 ppm measurement. The first problem is that the decay is W to lepton + neutrino...
  9. eneacasucci

    I Q value for a radioactive decay

    The Q value for a reaction is the amount of energy absorbed or released during the nuclear reaction. Is it correct to say that for a radioactive decay, since it is a spontaneous process, to occur the Q-value must be Q>0?
  10. Graham87

    Troubleshooting nuclear decay, electron binding energies, internal contributions

    How do you know which binding energy shell to use? In the solution it uses K and L2. Why specifically L2 and not L3 or L1 for example? And what should I do with the information to omit electrons lower than 20kev? I initially thought that meant to omit the electron binding energies lower than...
  11. Graham87

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    The problem comes with solutions. However, I dont get the 3 steps in the solutions. Why do they calculate decay for 120min in step 3? And why is only the daughter nuclide relevant and no granddaughter? There might be something lacking in my knowledge about nuclear reactions. Also, I don't know...
  12. I

    B Beta Plus Decay: What's Left for the Electron?

    Specifically, this would be beta plus decay and not electron capture, and assumes an electrically neutral radionuclide. Since beta plus decay is the emission of a positron from the nucleus as a proton transmutes into a neutron, the resulting atom now has 1 less elementary charge than before, but...
  13. H

    A What’s the meaning of decay rate in optical Bloch equations?

    i have some questions about decay rate. 1:why do we need decay rate in these equations? 2:is it a constant for a specific medium? 3:it can be changed with respect to some conditions like temprature or pressure? 4:how can i know the decay rate of some energy levels in 85Rubidium
  14. S

    I Observing Proton Decay & Antineutrinos

    antineutrino? I was looking at this article, which says that a proton that interacts with an antineutrion transforms (or whatever the proper verb is here) into a neutron & positron. But this begs the question that if we're trying to observe a proton decaying, how would we know that it had not...
  15. G

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    I'm reviewing history of subatomic physics. By 1931AD the nuclear physics community had decided to propose the neutrino because they couldn't explain beta decay without it. Alpha and Gamma decays were more confined wrt the energy they would extract from the nucleus i.e. they had energy bands. By...
  16. Graham87

    Radiation Physics - Decay Diagram

    In the solution below it says 22% goes to 0.0309keV. From the diagram above I interpret 22% goes to 0.1298keV with EC(L)/EC(K)=3.0 and not 4.4. Why is that wrong ? Thanks alot!
  17. eneacasucci

    I Gamma radiation decay intensity (IAEA nuclide chart)

    I was looking at the gamma radiation data from IAEA's website: (https://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html) and was confused by the absolute intensity listed in the page. I Googled it and it seems to be the probability of emission but why it doesn't add up to 100%? For example...
  18. G

    A Scalar decay to one-loop in Yukawa interaction

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  19. uxioq99

    Instantaneous Decay of Tritium into Helium

    I have been self-studying the MIT 8.04 Introduction to Quantum Mechanics course. This question is not graded, so I have no reservation asking about it on the internet. Imagine an electron bound by tritium (Z=1). One of the two neutrons undergoes beta decay and becomes a proton, causing the...
  20. ribella

    A Question about the decay of the W boson to tau lepton

    Why is generally the decay of the W boson to tau lepton not taken in the calculations?
  21. D

    I Theoretical pressure decay of a pressurised vessel

    I am looking to derive a method of plotting the theoretical pressure decay of a pressurised vessel. I would like to end up with a graph that plots internal vessel pressure against time. Is this possible? What assumptions would I need to make? The following inputs will be known. Gas: air...
  22. R

    I Muon Decay Example from Morin's Book: Issues Explained

    From the Lorentz transformation equations we know that $$t = \gamma(t^{'} - x^{'} v/c^2)$$ but for the Muon decay example where the setup is as follows : "Assume for simplicity that a certain muon is created at a height of 50 km, moves straight downward, has a speed v = .99998 c, decays in...
  23. D

    I Higgs decay to Z and Z* at LHC

    Goodmornig.I would like to explain me What is the Z* at higgs decay and why it has different mass from Z ?
  24. S

    What causes the radioactive decay of an unstable nucleus?

    A philosopher whose work I'm using in a paper uses a radium atom's decay as an example of a "spontaneous power," or an uncaused event. My professor, though, says "quantum fluctuations" cause radioactive decay. What are these fluctuations, and do we know what causes them? It's a college paper, so...
  25. M

    Free Decay analysis on SIMPACK

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  26. M

    I Neutrinoless double beta decay derivation

    Hello! Can someone point me towards a derivation (whether with Fermi Golden rule, or full QFT calculations) of the decay rate for the neutrinoless double beta decay: $$\Gamma_{\beta\beta}^{0\nu} = G^{0\nu}|M^{0\nu}|^2<m_{\beta\beta}>^2$$ Thank you!
  27. P

    Engineering Velocity Decay Curve for a Rocket

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  28. dark_nebula

    Question regarding a decay spectrum graph

    I am not sure what is the description of Channel.
  29. Dario

    B Where does the mass of a W boson come from in beta decay?

    During beta decay an electron and neutrino are emitted at very high speeds. I thought that the electron and neutrino were the product of w boson decay but I recently learned w bosons are over 80 GeV worth of energy. My question is, where does this mass come from? I know that atoms get enough...
  30. C

    A Beta/gamma decay probabilities

    Hi all, I have received this following question which I can't really figure out all the way to the end: Consider the beta decay of 212Pb: * What is the probability that the decay leads to the second excited state of 212Bi at 238.6 keV? This is straight forward - from nndc NuDat, it seems...
  31. person123

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  32. PainterGuy

    I How Does Beta Decay Relate to the Role of W Bosons in Weak Nuclear Force?

    Hi, Please note that I'm trying to understand it at very basic level. I'd really appreciate if you could help me with the queries below. I was reading this article, https://www.space.com/four-fundamental-forces.html, on the four fundamental forces of nature. Under the section The weak force...
  33. chwala

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    My interest is on question ##11.ii## only. I think there is a mistake on the markscheme...i just need a second opinion on this...find attached the question and markscheme... markscheme here: it ought to be, ##e^{0.0277t}=1.6797##
  34. Phys pilot

    I Energy distribution plot of neutrinos in beta decay

    Hello, When you have a beta decay you get the typical continuos spectrum representing counts against the kinetic energy of the electron. But what's the shape and how I get the spectrum of the kinetic energy of the neutrinos? Thanks
  35. nomadreid

    I Entangled particles in black hole decay?

    First, I was not sure whether this should go into the Relativity or the Quantum Physics rubric, but since the central question is about entanglement, I opted for the Quantum. I do not have the necessary sophistication to follow string theory arguments, and even most explanations in...
  36. T

    MHB How Does Newton's Law of Cooling Apply to a Roast Turkey?

    Newtons Law of Cooling states that the rate of cooling of an object is proportional to the temperature difference between object and it's surroundings. A roast turkey is taken from the oven when it's temperature has reached 185 F and is placed on a table in a room where temperature is 75 F. 1...
  37. L

    Calculation on spontaneous fission and effect from alpha decay

    Summary:: Help needed on how to calculate on spontaneous fission and effect from alpha decay Heat from alpha decay from Pu-238 is used to generate direct current. At the beginning (1977) it generated 470W, how large is the effect now? And if the efficiency between the electricity and heat...
  38. F

    A How to Extract Decay Chain Data from ENSDF Files?

    Dear community, I am trying to construct the decay chains and the decay radiations from ENSDF files. Until now, I have used the ones included in the ENDF6 file format such as JEFF3 or ENDFBVIII etc... However, I have been told that ENSDF was especially done for decay data. I found the software...
  39. P

    I Can 41Ca Decay to 40K through Proton Removal in Certain Situations?

    As I understand 41Ca usually decays to 41K through electron capture. However, if given a situation like the following: 41Ca+H+N=NK: where 41Ca+ only has one electron, and that electron is bounded to a nitrogen atom (essentially making 41Ca+2), is electron capture still the best option for...
  40. P

    I Radioactive decay question for K --> Ca

    As I understand 40K decays into 40Ca over a period of ##1.248(3)×10^9## yrs. Assuming this is the natural rate of decay, is there any way to shorten the period of decay (increase the rate of decay), for example, under extreme pressure or heat? Thanks:biggrin:
  41. G

    I Proton decay at the end of the Universe

    I wish this forum allowed indentation using tabs. Some of these questions are dependent on the answers to others. I have used outline numbers to indicate nested questions. I have BA in physics and mathematics, 40+ years ago. I was thinking (always a dangerous thing). I had some questions. I...
  42. Elon Musk

    Nuclear Physics help please (alpha decay of a Po-216 atom)

    I think that when an atom of polonium (Po-216) is moving slowly enough that it can be considered to be at rest. The Po-216 undergoes alpha decay and becomes lead ( Ph-212 ), via the reaction 깝 Po → Pb + ta. After the decay. the lead atom is moving to the left with speed v. and the alpha particle...
  43. Admiralibr123

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  44. JD_PM

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  45. P

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  46. T

    Which threshold value provides the most accurate results for muon decay time?

    I am trying to understand my results for my muon experiment. I conducted the experiment using a plastic scintillator photomultiplier detector. I have four different data sets, with different discriminator thresholds: 148 mV, 190 mV, 260 mV and 550 mV. I made a histogram of the counts of all four...
  47. T

    What is the purpose of the decay time distribution equation?

    I know for muons that the the probability that a muon decays in some small time interval ##dt## is ##\lambda dt##, where ##\lambda## is a decay rate. Thus the change in the population of muons is just ##dN/N(t) = −\lambda dt##. Integrating gives ##N(t) = N_0 \exp(−\lambda t)##. This makes sense...
  48. B

    Nuclear Decay Scheme: Learn the Basics

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