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Replies to Referee B
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The most important issue to be addressed is that the data shown in figures
1, 2 and 3 do not appear to be consistent. The main message of the paper, a
decrease in particle yield in dAu compared to pp with increasing rapidity,
is clearly visible in figure 3. However, in figure 2 the suppression effect
appears to be significant only at the approximately 2 sigma level. 

We’ve addressed the problems of consistency of Figures 1 and 2 in the covering letter to the editor and have updated both Figures.

Figure 2 shows a consistent change with rapidity and transverse momentum and is to be viewed as a systematic trend not as point by point deviations from the value of 1.  At eta=0 we see a clear enhancement similar to the so called Cronin effect measured at lower energies in fixed target experiments, as the pseudo-rapidity changes, such enhancement changes to suppression.

 The nuclear modification factor from the yield ratio in central to peripheral
collisions has been observed to exceed the nuclear modification factor
calculated by comparing to p+p collisions. Indeed this is the case for the
data in this paper at pseudorapidity 0 and 1 and at low pT for more forward
rapidities. However, for high pT at forward angles the trend appears
reversed.
 
The RdAu ratio is measured using minimum bias data and consequently should be compared with the semi-central Rcp.  Within errors we see agreement between both results.
If we compare the Rcp corresponding to our most central events we see a very clear change of trend as you’ve noted.	
 
 However, the rightmost panel of figure 2 is simply not consistent at
higher pT with the spectra presented in figure 1 for negatively charged
particles at pseudorapidity = 3.2! At the highest pT bin, the d+Au spectrum
actually falls below that in p+p, yet the RdAu reported in Fig.2 for that pT
bin is not the smallest value for pseudorapidity = 3.2. It is not possible
for this reviewer to determine whether Figure 2 is incorrect or Figure 1 is
incorrect, but one of them must be.

As explained in the letter to the editor, Figures 1 and 2 have been updated and the analysis procedures reviewed.
 
Looking at the spectrometer acceptance plot in the upper part of figure 1, one notes that the acceptance
at this setting is quite tiny. Furthermore, based upon the figure, the small
acceptance results in few particles measured, which must cause considerable
uncertainty on the acceptance correction. Undoubtedly many Monte Carlo
events were generated to study this, however, the reader is given no measure
of how well this correction has been determined. Since the acceptance
correction clearly must be very large, the authors need to recheck that this
is done properly, state the magnitude of the correction and the uncertainty
on it. It is very difficult to accept that the systematic uncertainty on the
forward spectra at high pT in Fig. 1 is the same 15% as where the
spectrometer acceptance is large and easily determined. In the ratio of d+Au
to p+p collisions, much of this uncertainty may be expected to cancel.
However, it is clear that this ratio will still reflect residual
uncertainties in the reproducibility of positioning the forward spectrometer
at 4 degrees. The authors should state the magnitude of this uncertainty
explicitly, as the main conclusion of the paper rests so heavily on this
spectrometer angle.

   The upper part of Figure 1 is not an acceptance map, but rather shows the outline of the data sample in eta and pt.  To clarify this we have altered the caption to that figure (see item 4 of the Summary of Changes).

   In fact the values of the geometrical acceptance at eta=3.2 are similar to those applied at other angles and range from 2% to 4% and is almost uniform in pt with an uncertainty that ranges from 3 to 5% of those values.
The back portion of the Forward spectrometer can be positioned within 0.08 mr and this angular resolution contributes negligibly to the systematic error.  Consequently it has been ignored.

As explained in item 2 of the Summary of Changes, we have allocated a systematic error equal to 20% from pt ~ 1 to  2 GeV/c where field settings overlap.  

As it is so important to the conclusion of the paper, which may be the first
observation of gluon saturation in nuclear collisions, further clarification
is needed for figure 3, as well. Because the suppression is more apparent in
this variable, it is important to also publish the centrality selected
spectra upon which this ratio is based. The statistical errors on the
minimum bias spectra are not visible in figure 1, and the shape as well as
value of the nuclear modification factor is very different in figures 3 and
2. I would therefore like to see the paper include the centrality selected
spectra, perhaps as a second set of panels to Fig. 3. 

The  Rcp ratios are easier to calculate than the RdAu because they are the ratio of raw counts in pt and eta bins. No spectra are produced.   Because they are extracted from the same run, and with counts in wider eta bins, these ratios have less fluctuations, but the physics information is different because they do not compare to a system as simple as p+p collisions, but to an average of 3.3 nucleon-nucleon collisions.
 
In the physics discussion in the last two paragraphs of the paper, there are
several issues, as well. The penultimate paragraph discusses two models
incorporating related, but quantitatively different, physics assumptions.
However, it does not give a clear message to the reader. Do the data prove
that one model is closer to the truth than the other? The concluding
paragraph appears to indicate that this is the case, but includes a sentence
whose meaning I was unable to figure out. Can the authors please replace
this sentence "Such modification produces a suppression at all values of pT
similar to the one observed when comparing multiplicity densities." with
something simpler and clearer? Presumably "the one observed" refers to the
amount of suppression, not the pT values... 

The rapidity and centrality behavior seen in our results are consistent with descriptions that include the onset of saturation and the effects of quantum evolution at high rapidity, but as pointed out by both referees it may not be up to us to settle a discussion that has only begun. We have thus modified our summary as noted in item 10 of the Summary of Changes.  

Also, for the general reader
of PRL, it would be useful if the pT range in which suppression is observed
were related back to the value of Q_s expected for the relevant rapidity
range to support conclusions about the gold wavefunction at small x. 

According to the color glass theory the suppression appears for all measured pt values and Qs ~ 2-3 GeV/c.   The detailed extraction of Qs remains a controversial theoretical problem that requires subtle analysis and can be found in the theoretical papers referenced.  We have nonetheless added a theoretical estimate to guide the general reader as in item 3 of the Summary of Changes.