What is W boson: Definition and 24 Discussions

In particle physics, the W and Z bosons are vector bosons that are together known as the weak bosons or more generally as the intermediate vector bosons. These elementary particles mediate the weak interaction; the respective symbols are W+, W−, and Z0. The W± bosons have either a positive or negative electric charge of 1 elementary charge and are each other's antiparticles. The Z0 boson is electrically neutral and is its own antiparticle. The three particles have a spin of 1. The W± bosons have a magnetic moment, but the Z0 has none. All three of these particles are very short-lived, with a half-life of about 3×10−25 s. Their experimental discovery was pivotal in establishing what is now called the Standard Model of particle physics.
The W bosons are named after the weak force. The physicist Steven Weinberg named the additional particle the "Z particle", and later gave the explanation that it was the last additional particle needed by the model. The W bosons had already been named, and the Z bosons were named for having zero electric charge.The two W bosons are verified mediators of neutrino absorption and emission. During these processes, the W± boson charge induces electron or positron emission or absorption, thus causing nuclear transmutation.
The Z boson mediates the transfer of momentum, spin and energy when neutrinos scatter elastically from matter (a process which conserves charge). Such behavior is almost as common as inelastic neutrino interactions and may be observed in bubble chambers upon irradiation with neutrino beams. The Z boson is not involved in the absorption or emission of electrons or positrons. Whenever an electron is observed as a new free particle, suddenly moving with kinetic energy, it is inferred to be a result of a neutrino interacting directly with the electron, since this behavior happens more often when the neutrino beam is present. In this process, the neutrino simply strikes the electron and then scatters away from it, transferring some of the neutrino's momentum to the electron.

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  1. G

    I W boson and weak decay

    Hello everyone I have been following Fermilab presentations by Dr Don Lincoln for some years. Recently he did a deeper review into the four fundamental forces. He explained why the weak force is relatively weak. The explanation given was that the “normal” mass of the W boson is relatively high...
  2. 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?
  3. N

    Is my Feynman diagram for production of ##W^-## boson correct?

    I think ##X## appears to be ##\pi^{+}## because it is light and energetically more favourable. Pion should be positive to ensure charge conservation. I am stuck at drawing a Feynman diagram for $$p+\bar{p} \to W^- + \pi^+$$. Is this correct? Is this the leading order diagram or is there a...
  4. 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...
  5. K

    I Does Conservation Hold True for W Boson Spin Changes during Beta Decay?

    Is this true?: During beta decay a quarks' spin is changed and the mass/ energy difference is converted to a W boson which quickly decays into an electron/positron and an anti neutrino/neutrino. The mass/ energy is conserved through E=mc^2.
  6. R

    I W Boson and different generations of quarks

    Can a W Boson convert an up quark into a down quark of the same generation? Where can I find a resource to understand what all the possibilities are for an up quark converting into other quarks of same or other generations?
  7. T

    Association between W Boson Decay and Leptons

    As a physics A Level student, I am interested in understanding particle physics. Recently I have read that a W boson, as a relatively heavy particle, decays into one of three charged anti-leptons, and one of the three neutrinos. If a W boson decays to form an anti-tau lepton, it will also form a...
  8. andrex904

    Computing Differential Decay of W Boson at Rest

    Hi, I'm trying to compute the differential decay of W boson at rest $$W^+ \rightarrow e^+ \nu_e$$ where the boson has fixed spin along z axis, and so specific cirular polarization. Using Feynman rules i get...
  9. J

    What Causes Beta Decay and the Role of the Weak Nuclear Force?

    I am familiar with the proton:neutron ratio and stability but what about this instability actually causes a quark to emit a boson and change flavour? And what does this have to do with the weak nuclear force? Thanks
  10. N

    Uncertainty Principle & W Boson Energy (Mass): Higgs Reconciled?

    I have read that W boson get their energy (mass) by temporarily breaking the energy conservation laws in accordance with the Uncertainty principle. I have also read that the W bosons get their mass through the Higgs mechanism. How are these two things reconciled? Is this the distinction...
  11. Safinaz

    W Boson Propagator in Unitary Gauge

    Hi there, As in Ta-Pei Cheng and Li's book for example the W boson propagator is given by : ## \frac{-i}{k^2-M^2} [g_{\mu\nu}+ (\zeta-1) k_\mu k_\nu/(k^2 - \zeta M^2)] ## At the unitary gauge ## \zeta = \infty ##, where the W propagator becomes : ## \frac{-i}{k^2-M^2} [g_{\mu\nu}- k_\mu...
  12. A

    Simple question on W boson decay products

    Hi, I'm working on an assignment in which the following reaction takes place: \nu_e e^- \rightarrow \nu_e e^- And I'm wondering whether its possible to have an electron neutrino and an electron annihilate to form a W^- boson, after which that boson decays into a \nu_e e^- pair...
  13. G

    Proton to neutron conversion at relativistic energies

    The reaction p→n+e++νe is common inside nucleus. But it not considered when we talk about free particle and reason is simply given mass of products being larger than reactants. Now my question is if there is a high energy proton having total energy in order of 2 GeV or let it to be 100 GeV (To...
  14. R

    How do the W and Z Gauge Bosons work in the weak nuclear force?

    I've seen explanations that when a neutrino with a W+ Boson comes near a neutron, it affects one of the bottom quarks and changes it to a up quark which effectively turns the neutron into a proton. The neutrino then turns into an electron. Source: (2:20 onwards) I've seen other explanations...
  15. M

    Understanding the W Boson: How are New W Bosons Created?

    So if W bosons decay so quickly from what are new W boson made? Is it made of an electron and anti-electron neutrino (which is what they decay into) but then again this wouldn't make sense since it is an "elementary" particle. Please clear my confusion.
  16. K

    W Boson Vertices: Incoming vs Outgoing

    Hi, a simple question on W boson vertices (and I guess field theory in general). If I have a W boson vertex for incoming particles, i.e. W^+ ubar d and W^- u dbar how do I change this for outgoing W's. The first interaction contains a CKM matrix element Vud and the second a Vud^*, and...
  17. S

    Mass/Energy of W Boson: Where Does it Go?

    From what I understand, which is kind of limited, the neutron (939Mev) decays into a proton (938Mev) giving off a HUGELY massive particle called a W boson (80,000Mev). The W boson exists for 3*10^-25 seconds then gets transformed into an electron (.511Mev) and an electron anti-neutrino (.28ev)...
  18. Thinkor

    Questions About W Bosons: Speed, Isolation & Existence

    Has the speed of W (or Z) bosons ever been measured? I presume not, because I have read they exist for only about 10^-25 seconds. So, how is it known that they are not charged particles that move at the speed of light, with energy, but no mass, like photons? Have they ever been isolated...
  19. A

    Understanding W Boson Decay: Exploring Quark Pair Possibilities

    Hey Guys, Just a quick question. Can a W boson decay to a u and anti s or does it have to decay to a quark and anti-quark of the same generation? Thanks!
  20. F

    A massive force carrying particle? The weak nuclear force, the W boson has mass?

    I was looking at the list of the force carrying particles and all of their masses read zero other than the W boson of the weak nuclear force. Q: Does the W boson travel at the speed of light even if it is massive? (I am guessing not) Q: If the W boson is massive then it emits other gauge...
  21. T

    Predicting the charge of a W boson

    For my Physics exam, I need to know 3 Feynman diagrams: beta-plus/minus decay, proton electron capturing, and neutrinos interacting with matter. I know that there's a W- in \beta- decay, W+ in \beta+ decay, which seems logical. However, in proton electron capture there is a W+ boson, and...
  22. F

    The W boson mass is exp(-4pi^2) of a Planck mass

    Almost: the result is 85 GeV, the measured mass is 80.4 GeV. Is there anybody who has ever looked at this coincidence? François
  23. I

    The different lifetimes of W boson and Pion?

    The positive W boson decays to a anti-muon and a muon neutrino, it should be a weak interaction. And the positive Pion can decays to a anti-muon and a muon neutrino, too. But the lifetimes of them are totally different, so why? I know the positive Pion is composed of two quarks, but could you...
  24. S

    What Is the W Boson and Its Role in Beta Decay?

    So I was reading about beta decay and they talk about the 2 forms W- and W+ but what i don't understand is what is the boson doing before this happens? I thought a proton or a neutron were made with gluons and 3 quarks? Is it that the boson is created during beta decay and if not what is its...
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