# Notation Question

1. Mar 9, 2005

### Norman

In older nuclear physics papers the convention for describing reactions is kinda hard to understand.
example:
$$p(p,n)\Delta^{++}$$

Now this must mean:

$$p+p \rightarrow n+\Delta^{++}$$

But does the older notation imply anything about targets vs. projectiles? Does the grouping of (p,n) imply anything?
Thanks

2. Mar 9, 2005

### James R

The notation does tell you something about the projectile and target, but I can't for the life of me remember which way round it is.

At a vague guess, I think the incoming projectile is the "p" in the brackets.

3. Mar 9, 2005

### dextercioby

What are u doing searching among older nuclear physics books/articles...?You live in the 21-st century,i presume...

Daniel.

4. Mar 10, 2005

### Norman

I didn't know that physics and it's laws have changed over time? Either way the notation was used as recently as the late 80's and I am working through a paper that uses it. I am also doing a prelimenary literature search for some research and want to know what has been done before me. What are you doing questioning why I am doing something?

5. Mar 10, 2005

### dextercioby

I wasn't questioning what you were doing,just that it seemed weird to wirk with something that's OLD.Weren't u able to find the same things in a newer source...?

Daniel.

6. Mar 10, 2005

### dextercioby

It's the same situation as working today with Minkowski metric (+,+,+,+) instead of Bjorken-Drell (+,-,-,-).

Daniel.

7. Mar 10, 2005

### Norman

(-,+,+,+) for minkowski right? Or are you talking about some kind of imaginary time issue... so that you can treat the time and spatial pieces on the same footing? I haven't studies GR, so I don't know. Anyways, the answer to the questions is that I was not able to find the information in a more recent source, at least not that I could discern. Plus I have seen a lot of papers in Nuclear Physics that have this kind of notation, and was basically just wishing to understand the notation, since I am reading the paper it would be nice to know what the title implies about the reaction. But in the end I was just curious.

8. Mar 10, 2005

### dextercioby

It's actually a trick.In QFT,one uses (out of commodity and habit) the mostly minus (+,-,-,-) metric,while in the flat limit of GR they use mostly plus (-,+,+,+)...

Daniel.

9. Mar 10, 2005

### Norman

I was confused by whether you meant (++++) or simply mistyped (-+++). And I was thinking the other day about what it would mean analytically continueing the time to the imaginary axis and treating it with the same sign as the spatial pieces... such that :
$$p^{\mu}p_{\mu}=E^2 + \vec{p}\cdot\vec{p}$$

I was just pondering it and thought oddly enough you might be saying they do that in GR.

10. Mar 19, 2005

### nrqed

I have to say that I found this incredibly rude.

It does not matter how old the source was. First of all there are many things published in the 80's or even 70's and 60's still useful for current research.
Second of all, even if someone wanted to understand a paper 100 years old, what would be wrong with that? Besides, I don't see what says that the notation asked about in the original post is not still in use today.

In any case, I found the reply condescending and rude.

Sorry, I had to say it.

Patb

11. Mar 20, 2005

### Norman

Thanks Patb.
I felt the same way, but I guess I don't really care since Dexter tends to do this a lot on here and some of us have given up caring or listening.
Anyways, I am still waiting to hear if James R is correct about the implication of the projectile and target.
Thanks,
Norm.

12. Mar 28, 2005

### Norman

I have figured out the answer. For the notation:
$$p(p,n)\Delta^{++}$$
This Decodes as:

Target (Projectile, Particles with projectiles rapidity) Final State Target

Hope this helps someone else.

13. Apr 4, 2005

### Meir Achuz

That notation is still common in nucler physics. Norman is close.
It goes: projectile(target nucleus,final nucleus)ougoing particle.
e.g. p([A,Z],[A,Z+1])n. When the target is just a proton, it does seem a bit silly.