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Reply to questions and comments from PWGC meeting

Updated on Thu, 2022-04-14 04:09. Originally created by clhu on 2022-04-08 11:47.

Replies to questions and comments from PWGC meeting:

1. Q. In abstract, “260M (5-40%) collisions” may be misleading and should be rephrased.
    A: Modify: From 165 million 5–40% good events.

2. Q. For Fig.1, how was the BG estimated?
    A. Rotational method was used for the BG. We rotate heavier daughter particles with random angle from 10 to 350 degree 20 times.
    Q. In 3 body-decay, the BG is not smooth under the peak.

    A. This background consists of two parts, one is“d + p + pi-”, and the other is from “d+Lambda”, this step structure is due to the contribution of “d+Lambda”. If we rotate proton or pi-, it will not have this bump, and the background will come smoothly, but it can not well describe the data mass.
    C. Good to check the yield and B.R. of 2 vs. 3 body decays.
    A: From Yuanjing’s analysis, after purity correction, the yields of combined 2-body and 3-body decays are consistant with the yield of 2-body decay for H3L, and the B.R. of 2 vs. 3 body decays is about 0.272±0.030±0.027.


3. Q. Any comment on the small peak near mass = 3 GeV?

    A. We use a Gaussian function to fit with this small peak, the significance is about 2.3. We also checked whether this bump came from the miss PID of proton and deuteron, after we select deuteron to be more strict, the bump still exists. We have not exmined the source of this small bump. However the mass interval of our H3L(3-body) signal is from 2.988 to 2.998 GeV/c2, which does not cover this bump. So this small bump does not affect our v1 results.



4. Q. For signal distribution, the tail is not described well by Gaussian fit. So you can please try student-t.

    A. We have modified the fitting function of mass spectra to student-t, it can well describe the subtracted invariant mass spectra for Lambda.

5. Q. Fig. 3: The light nuclei data look to curve a bit with rapidity. For Lambda the trend is opposite to light nuclei. Any physics reason?
    A. This may be related to collision dynamics, we do not know. But the model predicts the similar trend for Lambda.

6. Q. Maybe related to the curve trend, data points close to mid rapidity for H3L and H4L look lower than the neighbor bin though the uncertainty is large. Maybe related to pT acceptance in Fig. 2? Mean pT may be different with rapidity.

    A. The pT-y efficiency was applied. Considering the acceptance of H4L, we exclude the point in the rapidity bin from -0.2 to 0.

7. Q. Fig. 4: How can we conclude the coalescence from this plot?
    A. The mass dependence of the v1 slopes of the hyper-nuclei is similar to that of light nuclei and coalescence approach worked.
    C. The model fails to describe Lambda. If we need to rely on this model, this statement may not be justified.
    A. In the coalescence approach, the final results with in the hyper-nuclei yields or v1, are the contributions of Lambda+(A-1) nucleons. Strictly speaking, is it possible that a consistent results from model calculations with the perfect agreement for Lambda distributions. In our case, the coalescence parameters are fixed by the yields of the corresponding hyper nucleus. We are, in fact, are impressed by the mass dependent of the v1 slopes.

8. Q. For s15, “JAM plus coalescence afterburner” Does the coalescence is a part of JAM or added by PAs?
    A. The coalescence is not a part of JAM. 
    Q. One needs to treat n&p density and there are some parameters which could be improved more since the current model in Fig. 4 underestimates Lambda and also p&d slightly.
    A. p, n and Lambda yields and collective motions are given by the JAM/UrQMD model (Initial parameters of JAM/UrQMD are typical settings);  Still, the collective motion of p and Lambda can be described by these models qualitatively. The yields of light nuclei and hypernuclei change with the coalesence parameters but v1 of light nuclei and hypernuclei have a weak dependence. (https://drupal.star.bnl.gov/STAR/blog/hexh/light-nucleus-v1-and-v2-3-gev)

    Q. This part in detail should be followed up in LFSUPC since the other groups are also working on the coalescence model at 3 GeV to reproduce centrality/pt/rapidity.
    Q. Since this is home made model, the detail should be discussed in Appendix or supplemental material.
    A. This part of model calculations are discussed in the analysis notes on Page 73, and the same methods and parameters are used in the H3L and H4L lifetime and yield measurements at 3 GeV paper (gpc 321) by Yue-Hang. (arXiv:2110.09513)
 
9. Q. Last 2 sentences in the conclusions about YN interaction are not supported by presented materials. This part should be either removed or revisited with supporting materials.
    A: We have modified the conclusion.

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