Letter sent to all people involved and some prominent scientists
on 12.04.2003

Dear friends,

Now that, thanks to your efforts, the exotic S=+1 baryon seems 
to become gradually a reality and not just a fancy dream of a 
theorist, we have to think how to name the child to be born, 
hopefully.  

The tentative name Z+ we all have used is, to my mind, 
unfortunate. First, I have noticed that the first reaction by 
people hearing about it is that the new particle has some 
association with the electroweak Z boson. This association
is completely missleading and may create lots of confusion
in future and cause us much trouble. Second, the tradition 
is that baryons are named by capital Greek letters: Delta, Lambda, 
Sigma, Xi, Omega. (Except the nucleon but one cannot change it.)
Third, "Z" is pronounced very differently in different languages;
even in English it is "zee" in American English and "zet" in
British which is mostly used in Europe and elsewhere. Fourth,
and probably most important, the name "Z" was imposed on us 
by the unsuccessful searches of exotic baryons in the far higher 
mass region, as summarized in the 1986 edition of Particle Data. 
This was `prehistoric' time, before the discovery of the Z boson,
and in any case nothing has been found worth mentioning in 
Particle Data Listings since the 1986 edition. The 1540 MeV
signal has nothing to do with the broad and always suspicious
one-star candidates in the 1700 MeV region. I regret that
we uncritically and unthoughtfully borrowed this queer name 
and used it in our paper with Petrov and Polyakov. But at that 
time it was so far from experiment! 

I suggest that the name for this baryon should satisfy the 
following criteria:

1) It must be a capital Greek letter, according to the tradition
of naming baryons

2) It must be distinct from anything used before and carry no
associations with bosons
 
3) Last but not least, the character must exist in LaTeX.

If you look into the list of upper case Greek letters used in 
LaTeX you'll find that there is one and only one character 
satisfying all criteria, and it is 

THETA. 

When I discovered it I realized that I kind of liked this name.  
It is a symmetric and "round" character like the Omega also 
sitting at the vertex of the big decuplet triangle and, like Omega, 
alluding to that it is a singlet. If you disregard the historic 
"tau-theta problem" of the last century's 50s, this character 
has been never used in particle physics, as far as I know. It
carries no associations and hints that it is something really 
new, which it certainly is. Last, "Theta" is pronounced more or 
less in the same way in all languages I know. 
   
Therefore, I suggest that we, experimentalists and theorists,
will henceforth call the new candidate for the exotic baryon 
with strangeness +1 and mass around 1540 MeV a

\Theta^+  baryon.

Any objections? 

With my best regards,
Dmitri Diakonov