Polarization Measurements of p^↑ and ³He^↑ Beams at RHIC and Future EIC Using the Polarized Atomic Hydrogen Gas Jet Target

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Every new experimental facilities with polarized beams require a polarization measurement technique. This paper proposes application of the hydrogen gas target (HJET) polarimeter, previously well developed and tested in fixed-target experiments at RHIC, for polarimetry at the forthcoming Electron-Ion Collider (EIC). Detailed calculations are provided for polarimetry of a polarized helium-3 beams. 

 

As usual, the method is based on equality of the measured analyzing power in scattering with incoming polarized beam (or target), and polarization of the hadron in the final state in scattering of unpolarized hadrons. The process can be turn around due to T-invariance of the amplitude. This theorem has been proven only for 2-2 scattering, but not for a process with target/beam particle excitation, certainly not for He-3 break up.

 

I disagree with the statement \omega(0)=0 for parametrization (40). In the standard Glauber model forward quasi-elastic scattering (in particular He3-dp breakup) is incoherent process an has a non-zero cross section even for forward scattering (t=0).

 

I would recommend the paper for publication in spite of my critical comments, because the break up probability is quite small, about 1%, and any mistakes related to this channel are not important numerically.

 

Author Response

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Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presented a comprehensive polarized atomic Hydrogen gas jet target polarimeter for proton beam polarization measurement. The results measured at RHIC were well summarized and a prospective projection to future electron ion collider was also studied. The results are of interest for publication. However, there is still some room for improvement.

- Eq.1, is it for the resolution < 1% instead of < 1?

- From Eq. 9 and Eq. 12-15, the |r_5|^2 is simply calculated much smaller than 0.02, which is inconsistent with L.93, please double check.

- Fig.2, some labels on the plot would be better for the readers to distinguish the curves and bands without reading the captions.

- The conclusion Ajet_N< Aelastic_N<Abeam_N was made in L.190. However, from Fig.8, there are many hot spots at Z_R > 10 for Ajet_N, which is above the elastic line. An explanation here would be good.

- Fig.9, looks like some of the points fluctuate but without any error bars except the green ones on the right figure. Is there any error on those points?

Comments on the Quality of English Language

The language reads fine.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

This paper discussed the future measurements of the polarization of p and He-3 using the HJET. It's very important for our field. The manuscript is clear and well-written. Before its publication,  I have a short question, can you estimate the anticipated Bjorken x and Q^2 ranges achievable with the HJET target at RHIC and EIC facilities?

Author Response

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