STAR Correlations and Fluctuations PWG

[William Llope <fr4526 AT wayne.edu>]

Hello Xiaofeng,

> On May 17, 2022, at 6:59 PM, Xiaofeng Luo <xfluo.star AT hotmail.com> wrote:
> 
> Hi Bill,
> 
>     Very nice talk !
>     Please find my comments and suggestions below : 
> 
>     General comments : 
>     1. Since this seminar is on behalf of STAR on topic of Correlation and 
> Fluctuations, I feel it is Inappropriate that 
>         a lot of STAR results are missing, such as p-p, p-d, d-d 
> femtoscopic correlation just shown in QM2022,
>         BES-I and 3 GeV higher-order fluctuations. 

i will mention these results and add the references to the slides

>     2. It is very unusual to me that we present new preliminary results at 
> a seminar, not a conference.

i'll take this as a comment. 

>    Details : 
>     1. Currently, for the new preliminary results at 3 GeV, there are small 
> dip at Delta_phi ~ 0 for p-d and d-d pairs., and not seen in other pairs. 
>         Could you explain this ? 

yes - it is very interesting. Track crossing is very small for these pairs, 
and of course
we correct for that small amount, so this is not crossing. that is a true SRC 
effect
that deserves further investigation, as i will point out. It is one of the 
interesting observations
from this slide for sure. I do not intend to speculate on the physics 
interpretation
of it in this talk. Thanks for noticing it!

>     2. Could you explain, why the d-t pair show larger enhancement ~ 48% 
> than d-d ~ 24% and t-t ~ 36% ?

These are the experimental results. The shape of these correlations
suggest a clan-like or "multifragmentation" process where "clusters"
outflow and break up in flight, causing near-side intermediate range
positive correlations. 
Remember that these percentages are values of R2.
Which means, formally, that there are about 25% more dd pairs
moving in similar directions in the event ensemble than can be explained 
on the basis of the single particle spectra of d's in those same events.
Near side is enhanced and far side is depleted because of the
kinematic focussing of the decay products from these flowing clans.
This is a very old picture for multifragmentation - i used the same picutre
when i was at the NSCL in the 90's.

>     3. In the summary, It is stated that those strong correlations are 
> coming mainly from a spectator source     
>         I think it can be more specific : the enhancement could be mainly 
> due to nuclear fragmentation, but it needs further investigation.

i don't ascribe any real difference in meaning to those two terms.
I mean 'spectator source' in the sense of the simple participant spectator
model (from gary westfall and collaborator's "firestreak" model at the 
bevalac).
anyway, i consider "nuclear fragmentation" to be an equivalent term to 
"spectator source" - more or less - and i'll happy to mention your terms also
in the talk. cheers
bill

>  
> 
> Thank you, 
> Best Regards,
> Xiaofeng
> 
> On 2022/5/17 04:47, William Llope via Star-cf-l wrote:
>> hi all - i remain eager to address your comments on my presentation (which 
>> is this friday, 5/20, at 10am).
>> thanks, cheers
>>      bill
>> 
>> 
>>> On May 9, 2022, at 3:41 PM, webmaster--- via Star-cf-l 
>>> <star-cf-l AT lists.bnl.gov>
>>>  wrote:
>>> 
>>> [EXTERNAL]
>>> 
>>> Dear 
>>> star-cf-l AT lists.bnl.gov
>>>  members,
>>> 
>>> W.J. Llope (
>>> wjllope AT wayne.edu
>>> ) has submitted a material for a review, please
>>> have a look:
>>> 
>>> https://drupal.star.bnl.gov/STAR/node/59591
>>> 
>>> 
>>> ---
>>> If you have any problems with the review process, please contact
>>> 
>>> webmaster AT www.star.bnl.gov
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> 
> -- 
> Xiaofeng Luo
> Professor of Physics
> College of Physical Science and Technology
> Central China Normal University
> Luoyu Road 152, Wuhan China
> Office Phone #: +86-27-67867500
>