# Why is there still disagreement over the b quark's name?

• B
Gold Member
Some physics papers today describe the b quark as a beauty quark. For example:

Others physics papers today refer to b quarks as bottom quarks. For example:

The b quark is a particle that was theoretically predicted to exist in 1973 and first observed experimentally in 1977.

But, here we are in late 2018 and there still doesn't seem to be a consensus (if there is actually a widely adopted rule regarding the contexts in which you use one versus the other, that would also be an acceptable answer to this question).

Is there are pattern regarding who uses which terminology in terms of geography, educational pedigree, or position on issues in physics, or is it just a matter of personal preference? Are there style guides addressing the issue at places like CERN and Fermilab and Jefferson Labs?

Why does the dual terminology persist?

Last edited:

jtbell
Mentor
From the International Union of Pure and Applied Physics:

Symbols, Units, Nomenclature and Fundamental Constants in Physics, 1987 revision (page 12)

The names for quarks are the symbols themselves; the names ‘up’, ‘down’,
‘charm’, ‘strange’, ‘top (truth)’ and ‘bottom (beauty)’ are to be considered only as mnemonics for these symbols.
(where "the symbols" are u, d, c, s, t, b.)

I remember some people using 'truth' and 'beauty' when I was a grad student in particle physics 35-40 years ago, but 'top' and 'bottom' became conventional. I'm rather surprised to see someone use 'beauty' nowadays, although I admit I haven't paid attention to this particular issue. The paper you cited is a preprint that has not yet gone through editorial review by a journal. I don't know whether a journal editor would change it to 'bottom' or just 'b' for publication. It might depend on the journal.

ohwilleke
fresh_42
Mentor
top / bottom is far easier to speak than truth / beauty. Since particle physics is very international, this might have been the reason.

Gold Member
I haven't seen the term "truth" used for a t quark for ages (maybe never). But, see "beauty" used for a b quark on a regular basis, including in published articles (I link to pre-prints simply because its easier to quickly find examples and I review them every day). I wonder if beauty just sounds nicer when describing hadrons with it as a component than bottom.

mfb
Mentor
I wonder if beauty just sounds nicer when describing hadrons with it as a component than bottom.
I think that is the point. I see "bottom" more often, but some people like "beauty", and everyone understands them, so there is no strong incentive to unify it.

dlgoff
MathematicalPhysicist
Gold Member
the beauty is in the bottom... :-D

eloheim
mfb
Mentor
There is certainly some charm to the name beauty. Especially as the two often come together in particle physics. You have b->c as dominant decay and often charm as background as well. Or B hadrons as background if you study charm.

eloheim and ohwilleke
fresh_42
Mentor
There is certainly some charm to the name beauty. Especially as the two often come together in particle physics. You have b->c as dominant decay and often charm as background as well. Or B hadrons as background if you study charm.
Does this imply truth is often strange?

Klystron
jtbell
Mentor
the beauty is in the bottom... :-D
Especially at CLEO.

dlgoff
Gold Member
Especially at CLEO.
I don't think I've ever seen that many references (198) on a Wikipedia article.

mfb
Mentor
Wikipedia has a list of articles with most references
The CLEO article is exceptionally detailed due to this edit.
Does this imply truth is often strange?
t->Wb is the only decay observed so far. For the other quarks the status is better, with all the transitions seen. t->Ws should be the second-most decay, but so rare and so hard to distinguish from background that it won't be measured anytime soon (unless it is much more frequent than predicted).

Gold Member
t->Ws should be the second-most decay, but so rare and so hard to distinguish from background that it won't be measured anytime soon (unless it is much more frequent than predicted).

Or, unless we find some clever way to distinguish it from background statistically, for example, by carefully integrating data about angular momentum and linear momentum of decay products in each decay chain to distinguish t->Ws from decays such as c->Ws, so that lots of background can be efficiently distinguished.

One could also measure the rare, but far less background ridden process s->Wt for highly energetic s quarks, and get the inverse from which the measured rate could be determined.

Staff Emeritus
t->Ws should be the second-most decay

Actually, I believe it's $$t \rightarrow W + b + \gamma$$.

mfb
Mentor
Or, unless we find some clever way to distinguish it from background statistically, for example, by carefully integrating data about angular momentum and linear momentum of decay products in each decay chain to distinguish t->Ws from decays such as c->Ws, so that lots of background can be efficiently distinguished.

One could also measure the rare, but far less background ridden process s->Wt for highly energetic s quarks, and get the inverse from which the measured rate could be determined.
Good luck...
Actually, I believe it's $$t \rightarrow W + b + \gamma$$.
Didn't think about that. It doesn't sound easy to measure either.