Prospects for the Detection of the Diffuse Supernova Neutrino Background with the Experiments SK-Gd and JUNO

Round 1

Reviewer 1 Report

This review discusses an important topic and does so with the right timing. 

The calculations are not particularly complicated, which is good in view of the uncertainties, 

but the details are not shown in sufficient detail for a review. 

Here are some suggestions, mainly intended to increase the clarity and usefulness of this work.

1) Before eq.1 replace

differential neutrino flux 

-->

differential electron antineutrino flux 

2) In the caption of tab.1 you state

"The parameter ranges adopted to reflect the uncertainties"

Please clarify if the uncertainties are treated as uniform distribution. 

3) Why E_total is considered fixed in your calculations?

4) Please justify (e.g. by citing a reference) the value f_BH=0.27

5) Please report explicitly the formula for R_CC(z) and the value 

of cosmological parameters used in the calculation

6) A paper of Fukugita and Kawasaki 

https://arxiv.org/abs/astro-ph/0204376

and your ref. [4] have derived a model for detection and estimated uncertainty, 

based on the only supernova detected with neutrinos so far.  

I think it would be useful to compare with the expectations of your "DSNB reference model".

7) Please indicate usage of efficiency in your calculations

8) I suggest to expand table II (or possibly include a new table)

quoting the parameters of the detectors that 

you use in the calculation and more details:

name, time range, fiducial mass, number of protons, energy threshold,

signal efficiency, signal rate, background rate, background nature,

indicating the references where these values are discussed.

Author Response

Please see the attached.

Author Response File: Author Response.pdf

Reviewer 2 Report

This interesting paper presents a joint discussion of the sensitivity of two large detectors, SuperKamiokande and JUNO, for the diffuse supernova neutrino background.  Publication is recommended after the authors have considered the following remarks.

1. There is no discussion of the effects of neutrino physics on the models. A full discussion is beyond the scope of this article, and the authors are well aware of the complexity of the topic, particularly the non-linear mixing effects that shift flavors in the output flux of a supernova.   The primary effect of interest here is flavor change between electron and other flavors, because the electron spectrum can be hardened that way, to an extent equivalent to a significant change in redshift.  It is suggested that the authors indicate the extent to which (and the way in which) the models are affected.  Section 2 does not mention anywhere that I could find that the fluxes are for electron antineutrinos only. 
2. Section 2 could be made more readable by defining parameters rather than sending readers to a deep dive into the references.
3. Table 1 – assuming anticorrelation between the successful and failed SNe, the entry (0 .. 0.4) should be (0.4 .. 0).
4. Caption to Fig. 1: “fuction”  function
5. Line 123: nearly
6. Line 146: The background rate of 0.9 does not agree with Table 2.
7. Line 150: expected to continue
8. Line 303: precast  forecast
9. The paper is about SK and JUNO as the title says, but there is brief mention at the end of HyperKamiokande, and appropriately so. One other very large underground detector is under construction, DUNE.  There should be some brief discussion of this in the context of the DSNB.  It is very large, uses argon, and is thus sensitive to neutrinos rather than antineutrinos.  There is a tag through the analog state in 40K, and a LAr TPC has exquisite reconstruction capability that might reduce the background in the energy regime of interest.  Even if the answer is that it’s impossible, that should be said so that it does not appear to have been overlooked.
10. One really misses having a figure along the lines of Fig. 7 in Ref. 3, updated with all the new information presented in this and other recent papers. The reactor background in Japan must have gone way down, while at JUNO it is obviously large.  The detailed analysis of the atmospheric NC spectrum and the use of PSD to reduce it are very interesting.  The DSNB spectrum itself has been updated.  It would add a lot to the paper.

Author Response

Please see the attached.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper is well written and organised. The subject is relevant and interesting. I recommend the publication of the manuscript in the present form.

Author Response

The author thanks the reviewers for their helpful comments on the manuscript.