# ##Ds^{\pm}## to ##\tau## question on Branching Ratio

• ChrisVer
In summary, the pdg values for the tau to muon branching ratio are incompatible, and the more precise value from 2006 is more accurate.
ChrisVer
Gold Member
Hi I have some question...I want to find what fraction of some produced ##D_s^\pm## to decay into ##\tau##'s.
I was looking around the pdg and I came across something that confused me.
Here:
http://pdg.lbl.gov/2014/listings/rpp2014-list-Ds-plus-minus.pdf
on page 4 it lists the semileptonic decays, and an example for the ratio to muons it gives: ##Br(D_s^\pm \rightarrow \mu^\pm \nu_\mu)=(5.56 \pm 0.25)~ \times 10^{-3}##

However in this:
http://pdg.lbl.gov/2006/reviews/dsdecaycons_s034310.pdf
Equation (2) gives a totally different Branching ratio...
##Br(D_s^\pm \rightarrow \mu^\pm \nu_\mu)=0.0074\pm 0.0013= (7.4 \pm 1.3) \times 10^{-3}##

Why is this happening? (or what am I reading wrong?)

Well, the muonic branching fraction won't tell you the tau branching fraction, which is about 6%. But besides that, why shouldn't the number change and become more precise over the last 8 years?

5.6 is compatible with 7.4 +- 1.3 at a level of ~1.4 standard deviations. Nothing unusual.
If you check the http://pdg8.lbl.gov/rpp2014v1/pdgLive/BranchingRatio.action?parCode=S034&desig=7 , you'll see multiple measurements after 2006 going into this new, more precise average.

Last edited by a moderator:
ChrisVer
Well, the muonic branching fraction won't tell you the tau branching fraction, which is about 6%.

I would take the value from pdg for the branching ratio, however I came across this incompatible values and I became more aware of using those numbers...

But besides that, why shouldn't the number change and become more precise over the last 8 years?

I think because the values are not compatible (with errors)

They are perfectly compatible, see the post above (we posted nearly at the same time).

Table 6.6 gives 6.4% for tau neutrinos, you are looking at the wrong decay (##D^\pm##).

Oh I am sorry, for my last post, it's 100% wrong.

However @mfb I would like to ask how you can see the 1.4 std in the above... thanks

Last edited:
7.4-5.6 = 1.8 deviation

A better estimate would take the uncertainty on the more precise value into account. The uncertainties could have some positive correlation, however (from systematic effects), so not taking it into account it is a conservative estimate.

ChrisVer

## 1. What is the significance of the branching ratio in ##Ds^{\pm}## to ##\tau## decay?

The branching ratio in ##Ds^{\pm}## to ##\tau## decay represents the probability that a ##Ds^{\pm}## particle will decay into a ##\tau## particle compared to all other possible decay modes. It is an important parameter in understanding the behavior of subatomic particles.

## 2. How is the branching ratio in ##Ds^{\pm}## to ##\tau## decay determined?

The branching ratio in ##Ds^{\pm}## to ##\tau## decay is determined through experimental measurements. Scientists analyze data from particle colliders and other experiments to determine the number of observed decay events and the corresponding number of ##Ds^{\pm}## particles. This information is used to calculate the branching ratio.

## 3. Can the branching ratio in ##Ds^{\pm}## to ##\tau## decay change over time?

Yes, the branching ratio in ##Ds^{\pm}## to ##\tau## decay can change over time. This is because it is dependent on the decay rate of the ##Ds^{\pm}## particle, which can be affected by various factors such as temperature and external forces.

## 4. How does the branching ratio in ##Ds^{\pm}## to ##\tau## decay differ from other particles?

The branching ratio in ##Ds^{\pm}## to ##\tau## decay differs from other particles because it is specific to the decay of the ##Ds^{\pm}## particle. Each particle has its own unique set of decay modes and corresponding branching ratios.

## 5. What can the branching ratio in ##Ds^{\pm}## to ##\tau## decay tell us about the properties of the ##Ds^{\pm}## particle?

The branching ratio in ##Ds^{\pm}## to ##\tau## decay can provide information about the lifetime, mass, and interactions of the ##Ds^{\pm}## particle. By studying the branching ratio, scientists can gain a better understanding of the fundamental properties of this particle and its role in the Standard Model of particle physics.

• High Energy, Nuclear, Particle Physics
Replies
5
Views
1K
• Beyond the Standard Models
Replies
1
Views
2K
• High Energy, Nuclear, Particle Physics
Replies
1
Views
2K
Replies
7
Views
2K
Replies
13
Views
4K
Replies
8
Views
1K