We have now decided to follow the advice of the editors and transfer
our paper herewith to PRR Letters. Regarding the second referee to
elaborate on the effect on baryon asymmetry, we emphasize that this
will be the topic of a separate and longer paper for PRD (Ref. [32]),
with a different composition of authors. The basic theory of explaining
baryon asymmetry has been the subject of many recent papers, but with
ill-know input regarding the correct decay law. This is why we feel that
our present paper in its current form is well suited for PRR Letters.

> ----------------------------------------------------------------------
> Second Report of Referee A -- LB17688/Brandenburg
> ----------------------------------------------------------------------
> 
> The authors have clarified a lot of issues with the first version of 
> their manuscript. However, the novelty still remains in question. The 
> adaptation of the Hosking integral by the addition of the chemical 
> potential term could be important in some scenarios. The situation 
> with zero total helicity (as defined in the paper) seems rather 
> special. In generic situations, the magnetic helicity and the chemical 
> potential won't cancel each other. I view this paper as an interesting 
> study in MHD evolution, with a potentially important conservation 
> principle, but have reservations about its physical applications. 

The case of zero total chirality is the most generic situation, because
then no specific mechanism needs to be invoked for causing the net
chirality to be either positive or negative. We thus regard our work
as a critical paper where the new decay properties for fully helical
magnetic fields with balanced chiral chemical potential are studied for
the first time.

> ----------------------------------------------------------------------
> Second Report of Referee B -- LB17688/Brandenburg
> ----------------------------------------------------------------------
> 
> I have gone through the authors' reply and the revised manuscript. The
> authors now stress that the power-law decay of the magnetic helicity
> and the chiral chemical potential, found in this manuscript, has a
> significant impact on our understanding of the baryon asymmetry of the
> Universe. If so, these results would be interesting and important, and
> should have been the main part of the Letter.

Such a paper is in fact in preparation for PRD with a different
composition of authors, but there the theoretical understanding of
the origin of the generic decay law for such situations is not being
presented or explored. This is the purpose of the present paper, whose
readership clearly goes beyond that of just the PRD reader, because it
includes members of the turbulence and MHD communities, for example.

> The present manuscript, however, does not elaborate on how the
> power-law decay changes our understanding of the baryon asymmetry of
> the Universe. This manuscript rather looks a technical report of
> (routine, according to Referee A) simulation results, which is not
> very readable for non-experts. Therefore, it lacks physical
> significance and novel innovations, and I cannot recommend its
> publication in Physical Review Letters.

We have addressed this comment of the other referee in our earlier
response to referee A, where we wrote

  The idea that a Hosking-type integral can describe the decay of a
  fully helical magnetic field with helicity that is canceled by fermion
  chirality was a long shot, but it worked. The numerical calculation
  of chiral MHD is standard and implemented in the Pencil Code, but the
  interpretation of the results is not routine.

In our new response to referee A, we recall that the case of zero total
chirality is a generic situation; no specific mechanism for causing the
net chirality to be either positive or negative needs to be invoked.
We also emphasize that the generic decay properties of fully helical
magnetic fields with a balanced chiral chemical potential are studied
here for the first time.