Why is the W cross section so much larger than the Z cross section?

The cross-sections are generally larger due to the higher production rate of W bosons compared to Z bosons, and the branching fractions play a role in determining the overall size of the cross-sections. In summary, the W boson has a consistently larger cross-section at hadron colliders compared to the Z boson due to its higher production rate and the influence of branching fractions. The CKM matrix element and the neutral current couplings also contribute to this difference.
  • #1
JoePhysicsNut
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I had a look at the production cross sections for W/Z at hadron colliders. These differ as a function of energy with the W x-sec being consistently ~10 times larger than the Z cross sections. Why is the W cross section so much larger? I think the coupling strength is similar and the mass difference is not that large either (~10%).
 
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  • #2
I don't fully understand the reasoning, but this paper gives the ratio as σWZ ≈ 3.33, and this book derives (Eq. 85) the ratio as

σWZ ~ |Vqq'|2/(vq2 + aq2)

where Vqq' ≈ 0.97 is the CKM matrix element and aq = 1/2 and vq ≈ -0.3 are the neutral current vector and axial vector couplings.

Which works out about right.
 
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  • #3
What you are probably looking at are not cross-sections but cross-sections times branching fractions.
 

What is the significance of W/Z production cross sections in physics?

The production cross section is a measure of the likelihood that a certain particle will be created in a collision between two particles. In the case of W/Z production, it helps us understand the strength of the weak force, one of the four fundamental forces in the Standard Model of particle physics.

How are W/Z production cross sections measured?

W/Z production cross sections are typically measured using collider experiments, such as the Large Hadron Collider (LHC) at CERN. These experiments involve accelerating particles to high energies and colliding them together, and then using detectors to measure the particles and their interactions.

What factors can affect W/Z production cross sections?

The production cross section can be influenced by a variety of factors, including the energy of the colliding particles, the type of particles involved, and the physical environment in which the collision takes place. The cross section can also be affected by the presence of other particles or interactions.

What is the difference between W and Z production cross sections?

W and Z production cross sections are both related to the weak force, but they involve different particles. W production refers to the creation of the W boson, which is responsible for the weak nuclear force, while Z production refers to the creation of the Z boson, which mediates interactions between weakly interacting particles.

Why is it important to study W/Z production cross sections?

Studying W/Z production cross sections can help us better understand the fundamental forces and particles that make up our universe. It also allows us to test and refine our theories of particle physics, and can potentially lead to new discoveries and insights about the nature of matter and energy.

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