[Clascomment] OPT-IN: Shrunken particles pass freely through nuclear matter

[Charles Hyde]

This is a very interesting paper, that I think is bound to be widely noted.
I think there are a few important points that could be clarified.

First, one minor point,
perhaps the title should be altered to
"Shrundken particles pass freely through COLD nuclear matter"
Making this distinction may actually highlight the connection to RHIC physics.

My only difficulty is with the description of figures 2 and 3.

The text doesn't really specify how the data are sorted or cut to
create Fig. 2.  Is this the same dataset (same cuts) as in fig. 3?
If the formula is l_C = 2\nu/(Q^2+M_qq^2)
Are all of the data just thrown together and you make three bins (C, 4 bins Fe) 
in l_C from the variations in \nu and Q^2?
Do you use m_\rho for M_qq or do you use the full variation of m_\pi\pi from Fig 4?

Fig. 3 is clearly the heart of the paper.  The cuts are only vaguely described.
In particular, in the first paragraph of the Methods Summary, you state
"Kinematic cuts were used to identify exclusive diffractive $\rho^ 0$ 
meson electroproduction events and to reject coherently produced... "
It seems to me important to clarify a little bit how the quasi elastic events 
were selected.  Was it a constant cut on W2 for all Q2?  A constant cut
on a fixed value of \nu - Q^2/(2M_A)?  A fixed cut on x_Bj?
I presume there was both a lower bound to remove the coherent elastic peak,
and an upper bound to remove production of a 3rd pion.
Specifying these cuts is important, because without clarification, it will be
impossible for a theorist to attempt to generate curves for Fig. 3,
Since any calculation must be integrated over nu, (or W2, etc).


Sincerely,
Charles Hyde