Secondary Beams at High-Intensity Electron Accelerator Facilities

Round 1

Reviewer 1 Report

The manuscript under review discusses the production of muon, neutrino, and BSM particles at Hall A of the CEBAF beam dump, including its energy upgrade to 22 GeV. This is an interesting topic because the intense flux can be opportunistically utilized to enhance the physics program of the facility. The authors extend and leverage tools from reference [13] to evaluate the performance of the BDX experiment. In this paper, they specifically focus on a dark matter model that may be explored by mini-BDX and BDX. The paper is well-crafted and technically sound. I particularly commend the use of biasing and reweighting techniques to address computational challenges in beam dump experiments. I believe the flux estimates they obtained are well-grounded and hold significance for the particle physics community. Consequently, I fully support the publication of this paper in Instruments.

The only aspect that perplexes me pertains to the discussion on dark matter. I observe that the authors have exclusively examined a highly specific model outlined in page 9, lines 261-263 (also referencing [15,16]), along with narrowly defined parameters (page 10, line 286). I recommend that the authors broaden the discussion to encompass other potential dark matter candidates (e.g., inelastic dark matter as discussed in reference [13]) and explore a more extensive parameter space for the leptophilic model presented in references [15,16]. Aside from this, my comments are of a minor nature and are detailed below:

1) page 1 line 26 remove “if properly focused” because we cannot really focus muons and neutrinos except for relying on the production kinematics

2) p.2 l. 44 “Thomas Jefferson” -> “The Thomas Jefferson”

3) p.2 l.64 “will be less consistent” Do you mean less intense?

4) p.3 l.99 “input cards” is jargon. I suggest “input parameters”

5) spaces are missing in p.3 l.100 and 101 (“weights.As”, “EOT.Simulation”)

6) Fig. 4. 235 GeV -> 235 MeV

7) I would have expected to see a 235 MeV peak/excess in Fig. 5, as well. Am I wrong?

8) Fig. 11. What is the physics reach of BDX and BDX-mini if operated at 22 GeV instead of 11 GeV?

9) Fig. 11. What is the reason for the sharp cutoff of the exclusion line at m_s=0.21 GeV?

10) References. Please check the link to the arXiv papers: they link to LANL instead of the new Cornell website and, therefore, they do not work. 

see the comments above

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The article describes the possibility of using muon/neutrino/hypothetical light dark matter generated in the beam dump of high-intensity electron beam facilities like Jlab in the US.

A similar idea is proposed in ILC (https://doi.org/10.1016/j.nima.2023.168144) and maybe other facilities, but the article studies the existing facility concretely and systematically using Monte Carlo simulations. The reviewer judged the study worthwhile for the reader of Instruments, but some descriptions are misleading and had better be revised.

l   In section 3, the scheme of the simulation is generally well described, but the author stated the beam dump is surrounded by 4-5 m of concrete. However, the size of the concrete in Fig. 1 differs from this discretion; an oval sphere or rectangular shape of 8 m in the longitudinal direction and about 3 m in the transverse direction. In addition, there is no explanation for the layer in yellow in the beam dump.

l   The difference between Fig. 4 and Fig. 5 is not so clear. Is Fig.5 tallied at the position of muon’s generation and Fig. 5 at the detector? If so, this should be explained.

l   Comparing the neutrino result, the muon intensity decreases too steeply below around 0.2 GeV in Fig. 4. The reason should be explained.

l   Is the muon rate of 10^-6 /EOT stated in line 179 summed over all energy regions shown in Fig. 5? If so, this should be stated. Also, the comparison with Fermi lab’s g-2 beamline [30] is misleading because its rate is obtained at the so-called magic momentum of about 3 GeV.

l   The neutrino information could be valuable, especially for heavy neutrino or so-called sterile neutrino searches. The horizontal sectional view should be shown to think of the location of detectors in a prospective experiment even if there are geometrical constraints and it is hard to place the detectors.

The following minor points should also be revised.

l  In line 87, trough -> through

l  In line 152, reference 28 is obsolete and should be “C. Chen Y. Bao and Nikolaos Vassilopoulos, J. Phys. Conf. Ser. 2462 012027: https://doi.org/10.1088/1742-6596/2462/1/012027”

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

General Assessment: In this manuscript, the authors conduct a Monte Carlo simulation study of secondary beam productions from primary 11 GeV (and the proposed 22 GeV upgrade) electron beams in the beam dump (BD) at J-Lab, encompassing hypothetical Light Dark Matter (LDM) particles. The study is relevant to the community exploring dark matter particles in beam dump experiments. I recommend the manuscript for publication after addressing the following comments, primarily related to figure clarity, references, and overall readability.

Specific Comments:

1.     Fig. 1 and Text:

• Clarify the color of the neutrino detector, as the text mentions "red," while the figure shows "orange."
• Specify whether the drawings of the muon/neutrino detectors are to scale or merely indicative of their locations. Provide this clarification in both the text and the figure.

2.     Fig. 3 and Text:

• Clearly depict the beam's incoming direction and relevant distances. Elaborate on the two existing pipes downstream of BD, including additional locations and dimensions.
• Redraw Fig. 3 to provide a clear representation of muon production, LDM production, and photon detections with diagrams.

3.     Fig. 4:

• Correct the typo in Fig. 4: "235GeV" should be "235MeV."

4.     sBDX-MINI Experiment (6.3):

• Propose the inclusion of an experimental layout diagram to illustrate how the measurements of S -> gamma + gamma could be conducted. While reference 44 is mentioned, it is advisable to explicitly display this information in the paper.

General Comments:

• Address the following concerns related to the simulation tools (FLUKA and GEANT-4):
1. Specify whether default values were used in the study.
2. Discuss any cross-checks conducted with existing data.
3. Provide insights into the uncertainties associated with the secondary beam yields, muons, and neutrinos.

Minor Typographical/Editorial Suggestions:

• Ensure consistent formatting and usage of units throughout the manuscript.
• Review the manuscript for any grammatical errors or awkward phrasing.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The reviewer appreciates the authors’ revision except for the following point.

In Fig. 4, the spectrum seems to be not obtained at the muon’s generation position, but at the boundary between the BD and its surroundings. If so, this should be stated explicitly, e.g. “Momentum spectrum of muons at the boundary between the inner core of BD and outer one with p>100MeV …"

Author Response

Caption and text edited accordingly in the new version off the paper:

Caption:

'Momentum spectrum of muons at the boundary between the inner core of BD and the outer one with $p>$~100~MeV produced by 11~GeV (blue) electron beam.'

 Text:

'The muon flux has been sampled at the boundary between the inner core of BD and the outer one.'