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title: TwoParticleCorrelation_20200717_CommitteeDiscussion

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## Main issues associated to results publishment with two-particle correlation measurement at Belle

C.-W. Lin, Y.-C. Chen, Y.-J. Lee, P. Chang
National Taiwan University
2020/07/17

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## Concept (Standpoint) for [CONF draft v1](https://belle.kek.jp/secured/belle_note/gn1532/CONF_draft_v1.0.pdf)
+ About the results to make public on ICHEP:
(\* Now in the CONF paper are about (1) results we want to show (2) final conclusions we want to mark)

1. I think we agreed to concentrate in the conference paper and presentation only on the **off-resonance results** and try to **explain the motivation and methods in more detail**. 
    > That is even more so necessary for the thrust axis analysis and **why the near-side peak is not visible there anymore**.
2. clearly explain all the HI-jargon words (particularly flow, ridge, etc) including references. 
    > You should try to be precise in your wording and for example not talk about jets when you do not explicitly measure them (though words such as two-jet-like topology at higher thrust can be used).
    > 

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### Abstract: 
+ [x] I think you need to clearly specify why you want to study this in e+e-. 
    > Beam: clean envioronment
    > Thrust: gluon-jet
+ [x] **Now no ridge signal**: Also, the "signal" you see is not coming from qqbar production and you need to say so in the abstract as otherwise this is misleading. (I guess that needs to change anyway after only concentrating on the continuum data)
+ [x] You have not measured jets, so do not talk about jet fragmentation. If at all, talk about fragmentation itself .

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### Content
+ [x] For the paper you need to use the **usual Belle conference authorlist**, please add the latest from the Belle pages.
    > Authorship stuff: https://belle.kek.jp/secured/publication/pubproc.html (item 6)
    > https://omega.phys.vt.edu/author/
    > 

+ Some more detailed comments about the conference paper:

+ [x] line 63 explain **Delta r and z**.

+ [x] line 113 You need to reference and explain what that is
    > Original text: The systematic uncertainties of the correlation function measurement are calculated with respect to the long-range azimuthal associated yield.
    > This is my bad. Suggest swapping with next section.

+ [x] line 127 What is **Flow**? You need to explain it. Afaik even Hi people do not necessarily agree what that term means. Everybody else does not know this term at all.

+ [x] Fig2 is very useful, but I have no idea what would correspond to a **ridge signal**. You need to explain it some more. I guess a nonzero signal at Delta phi around zero?
    > Neet to re-define the near-side. Or we want to drop this term

+ **We need to reiterate this some more after you have implemented the changes we discussed so far. It would be great if you could have that ready before the BAM presentation.**
----

### Physics concepts and terminology ([CONF](https://belle.kek.jp/secured/belle_note/gn1532/CONF_draft_v1.0.pdf))
+ [x] line 10-11: "the ridge signal is associated with the hydrodynamic flow expansion of the Quark-Gluon Plasma" is misleading. At RHIC the ridge in HI collisions is generally described as a result of fluctuations in the density and shape of the initial overlap geometry, not the subsequent hydro expansion.
    > Should explain explicitly on the **flow-like** behaviour we refer to.
+ [x] The title we set "Search for flow-like signal" (see above, means what w.r.t. ridge). In e.g., pp and at LHC **have indicated there may be some other composite phenomena**, and this has excited folks as to what this might arise from. But one certainly needs to be precise as to the goal/terminology and then careful when addressing a "heavy ion audience" at ICHEP.
    > We can have a separate title for paper (apart from talk): "Measurement of two-particle correlation in hadronic $e^{+}e^{−}$ collisions at BELLE".

----

### Unanswered questions and todo 
+ Why is there no near-side peak
    + We've tried on manipulation with the collision energies with generator sample, and we see the relation with the magnitude of near-side peak and collision energy. 
    + We are still deciding whether to put this study onto the publication.
        > 1. Beam axis intra-jet correlation descreases (some of them go into correlation in $0≤\Delta\phi≤2\pi$) when turning into thrust axis coordinate measurement.
        > 2. Two-particle correlation measurement are thus sensitive to transverse direction tracks' correlation of a reference axis, and less-sensitive to the correlation very collimated with the refernce axis. (as argued above)
        > 
        |  | Beam axis coord. | Thrust axis coord.  |
        | -------- | -------- | -------- |
        | Sensitive     | possible expansion of QGP's flucuation    | soft gluonic radiation in the dijet event |
        | Insensitive   | beam remnant | quark, anti-quark jet |

        > 3. We don't have the origin peak in thrust axis coordinate, it could relate to the gluon-jet emitted in this energy level is a fatter jet with low multiplicity, c.f. high energy. We observe the magnitude of this origin peak correlation is some function of collision energy.
        > 4. Explain that details in BN.
+ [x] B meson effects and other channel contributions.
    + We think there is value to compare in the on-resonance data. 
        > Narrow the scope for ICHEP talk (to be able to show all materials/explanation in time) to off-resonance data. We can include the on-resonance sample in a comprehensive version of journal paper.
    + We analyze with $N_{Trk} \ge 6$, which largely suppress low-multicplity QED events.

----

### Details of analysis steps -- suitable goals
+ [x] again, all this focus on exclusion at 10^-{high power} or so really makes no sense to me (are you trying to exclude a underlying LHC composite particle?). The ridge was originally a visible phenomena ... how has this turned into some thing one wants to try and quantify at some "5 sigma" level?
    > This can be useful in terms of comparison between different sample under different experiment (the methodology of quantifying ridge yield is very mature and well-defined).
    > 
----

### What analysis parts / conclusions are solid for talk/conf paper?
+ [ ] in spite of comments/cautions, the draft paper now includes just about everything (kitchen sink?) touched on in the Belle Note .... plus I see now new calculations and graphs.
    > Will narrow the materials in terms of ICHEP.
+ [x] what of this should/can be actually presented on this relatively short notice? Has this been discussed at all in the Charm PWG?
    > Yes. And we will give a talk in the Special BAM: 
    > + Indico link: https://kds.kek.jp/indico/event/35104/
    > + Time: 17:45-18:10 Asia/Tokyo

----

### Miscellaneous
+ [x] line-by-line comments on the emerging conf. draft (does analysis note also need update for ICHEP? -- I see now what look like new graphs in the conf. paper relating to predictions from pythia, herwig and sherpa?)
+ [x] UL results: Plan to replace UL arrows by dots to represent ridge yield for on-resonance sample in thrust axis analysis. 
+ Belle Note v3.1
    + Thrust-binned 2PC results.
    + To address detailed questions (talk about later).
    + Is it planned to publish this as a journal article? Improve style & grammar for BN to be more readable?
<!-- + Systematic uncertainty on Y(Δɸ): (1) Quote the value of correlated constant error. (2) Plot dashed curves to demonstrate correlated sinusoidal error come from parametrization of mix event re-weighting. -->




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## Detailed questions and plots to be approved

+ [Recap of analysis procedure to clarify ambiguous (not-well-explained) points](https://www.dropbox.com/s/7tyex2jrupbqtmz/TwoParticleCorrelation_20200717_CommitteeDiscussion.pdf?dl=0).
+ Discuss on materials we want to present on ICHEP.
    + [ ] We need to generate more Belle MC in order to shrink the error band. (there is 6x Belle data sample to be used)
