Higgs boson lifetime and decay length?

Click For Summary

Discussion Overview

The discussion centers around the lifetime and decay length of the Higgs boson, particularly in the context of its behavior in detectors at the LHC. Participants explore the implications of decay widths, the Heisenberg Uncertainty Principle, and relativistic effects on the Higgs boson's travel distance.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant calculates the Higgs boson's lifetime to be 1 zeptosecond based on a decay width of 0.002 GeV and the Heisenberg Uncertainty Principle, questioning the assumptions about speed for distance calculations.
  • Another participant suggests using the relation ħc/Γ to estimate the distance traveled, indicating that a Higgs boson with a width of 200 MeV would travel about 100 fermis, noting that time dilation could allow a highly energetic Higgs to travel farther.
  • A participant questions whether the assumption of the Higgs traveling close to the speed of light (c) is valid, highlighting the significance of time dilation in this context.
  • Another participant discusses the implications of the resonance peak being centered on the Higgs rest mass, suggesting that if Γ is much smaller than mH, the Higgs will have lower momentum and thus travel less distance.
  • One participant argues that corrections for travel time on the order of zeptoseconds may not significantly affect practical outcomes.

Areas of Agreement / Disagreement

Participants express differing views on the assumptions regarding the Higgs boson's speed and the implications of time dilation, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

Participants rely on specific decay width values and assumptions about relativistic effects, which may not be universally accepted or applicable in all contexts.

MarekS
Messages
33
Reaction score
0
I am trying to figure out how fast the Higgs decays and how far it travels in a detector at the LHC. Figure 2.5 in http://www.hep.lu.se/atlas/thesis/egede/thesis-node14.html gives decay widths of the Higgs as a function of its mass.

For a Higgs of 125 GeV, it is 0.002 GeV. Using the Heisenberg Uncertainty eq. lifetime*decay width = h-bar/2, I find lifetime = 1 zeptosecond. Is this correct? What kind of assumptions can I make about its speed so that I could calculate distance travelled?
 
Physics news on Phys.org
An easy way is to use the value of Planck's constant in the form ħc ≈ 200 MeV-f. This says that a particle with a width of 200 MeV will travel about a fermi before it decays. More generally the distance traveled is ħc/Γ. So if the width of the Higgs boson is, as this guy claims, 2 MeV, the distance it travels will be about 100 fermis. A highly energetic Higgs will travel somewhat farther than this due to time dilation.
 
Dear Bill_K,

thanks for the input. By using c in the equation, you are assuming that the Higgs travels at (close to) c, are you not? If this is the case, then time dilation will be a significant effect.

Marek
 
If the resonance peak is centred on the Higgs rest mass, and Γ << mH, then it will be slow.

Its momentum will be of the order

pH ≈ Γ / c

so, by the uncertainty principle, this implies an uncertainty in its position of

Δx > ħ / pH = ħc / Γ

which gives an indication of how far it will travel.
 
I think you will find that if it travels for zeptoseconds that any correction of a factor of a few does not make any practical difference.
 

Similar threads

  • · Replies 13 ·
Replies
13
Views
5K
  • · Replies 11 ·
Replies
11
Views
4K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 17 ·
Replies
17
Views
6K
  • · Replies 13 ·
Replies
13
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 19 ·
Replies
19
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 6 ·
Replies
6
Views
6K