Why lower limits on proton decay lifetimes depend on channel

In summary, the different lower limits on the proton decay lifetime \tau set by, say, Super-Kamiokande, are due to different background rates.
  • #1
Anchovy
99
2
If I look at the lower limits on the proton decay lifetime [itex]\tau[/itex] set by, say, Super-Kamiokande, I'll see different lower limits depending on what the proton could decay into, eg. [itex]\tau_{min}(p \rightarrow K^{+} \overline{\nu}) < \tau_{min}(p \rightarrow \mu^{+} \pi^{0}) < \tau_{min}(p \rightarrow e^{+} \pi^{0})[/itex].

What is the reason for this? Is it to do with what the theoretical prediction for each decay channel's decay rate is? Or is experimental, ie. how good the detector is at picking up each observable decay product? Or perhaps to do with different background rates? Or something else?
 
Physics news on Phys.org
  • #2
It is an experimental effect. If you observe a fixed amount of protons, and expect to see 50% of all decays to kaons but only 5% of all decays to muons, you'll probably set better limits on the kaon decay. On the other hand, if you have a lot of background for some decay channel, your limit can be much worse.

Assuming protons decay at all, those three decay channels will have different partial lifetimes (= different branching fractions = different partial decay widths).

The 50% and 5% numbers are made up, didn't check the actual numbers.
 
  • #3
mfb said:
It is an experimental effect. If you observe a fixed amount of protons, and expect to see 50% of all decays to kaons but only 5% of all decays to muons, you'll probably set better limits on the kaon decay..

OK, so what would cause such difference in a water Cerenkov? (I think in your example it'd be the other way round, I think Super K has set a higher lower-limit for the muon channel than a kaon channel). Do kaons produce worse-quality rings at the PMTs? Or would more muons be energetic enough exceed the threshold at which they can radiate Cerenkov light? Or something else?
 
  • #4
Kaons are slower, their Cherenkov cones (assuming they are fast enough at all) will be wider and not as bright. They decay to other particles which can make the event look messy.

Muons lead to a nicer Cherenkov cone, but they could suffer from more background from neutrino-induced events. Same for electrons.

The publications should give the detection efficiencies and the background levels.
 
  • #5
mfb said:
Kaons are slower, their Cherenkov cones (assuming they are fast enough at all) will be wider and not as bright. They decay to other particles which can make the event look messy.

Muons lead to a nicer Cherenkov cone, but they could suffer from more background from neutrino-induced events. Same for electrons.

The publications should give the detection efficiencies and the background levels.

OK, thanks.
 

1. Why is it important to study proton decay lifetimes?

Proton decay is a fundamental process that can provide insights into the behavior of the building blocks of our universe. Understanding the lifetime of proton decay can help us better understand the laws of nature and the origins of the universe.

2. How do lower limits on proton decay lifetimes depend on channel?

The channel refers to the specific decay mode of the proton, for example, whether it decays into a positron and a neutral pion or a muon and a neutral pion. The lower limits on proton decay lifetimes depend on the channel because different decay modes have different probabilities and energy requirements, which can affect the observed decay rate and thus the estimated lifetime.

3. What factors affect the lower limits on proton decay lifetimes?

Several factors can affect the lower limits on proton decay lifetimes, such as the energy of the decaying proton, the mass of the decay products, and the strength of the fundamental forces involved in the decay process.

4. How do scientists measure proton decay lifetimes?

Scientists use large-scale experiments, such as underground detectors, to observe and measure the decay of protons. These experiments involve studying the byproducts of proton decay, such as photons and leptons, to determine the lifetime of the decaying proton.

5. What are the current lower limits on proton decay lifetimes?

The current lower limits on proton decay lifetimes vary depending on the specific decay channel being studied. However, they are typically on the order of 10^33 years, which is a very long time compared to the age of the universe. This makes proton decay a very rare event, and measuring its lifetime is a challenging task for scientists.

Similar threads

Proton decay lifetime prediction SU(5)?
    • High Energy, Nuclear, Particle Physics
Replies
22
Views
2K
I Pion Decay Rate: Verifying Decay Rate Formula
    • High Energy, Nuclear, Particle Physics
Replies
13
Views
3K
Prerequisites for learning MSSM --> proton decay prediction?
    • High Energy, Nuclear, Particle Physics
Replies
8
Views
1K
I Exploring the Limitations of Preon Models in Particle Physics
    • High Energy, Nuclear, Particle Physics
Replies
6
Views
4K
Confused by these proton decay diagrams
    • High Energy, Nuclear, Particle Physics
Replies
4
Views
2K
I How do the collider experiments measure the mass of the W boson?
    • High Energy, Nuclear, Particle Physics
Replies
4
Views
2K
I Implications of no proton decay, simplest GUT ruled out
    • Beyond the Standard Models
Replies
28
Views
4K
I B -> s µµ decays: Current status
    • High Energy, Nuclear, Particle Physics
2
Replies
49
Views
9K
Calculating proton decay lifetime correctly?
    • Advanced Physics Homework Help
Replies
5
Views
1K
A Hints for lepton flavor violation in B-hadron decays
    • Beyond the Standard Models
Replies
1
Views
2K

Hot Threads

Recent Insights

Back
Top