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BNL Nuclear Physics Seminar - Shared screen with speaker view
Xin-Nian Wang (LBNL)
01:03:37
What is behind the multiplicity distribution difference between Ru+Ru and Zr+Zi?
Fuqiang Wang
01:04:44
The overall size of Ru is slightly smaller than Zr, because Zr has a thicker neutron skin. So the energy density in RuRu is a bit larger, thus multiplicity is larger.
Xin-Nian Wang (LBNL)
01:06:29
Thanks
Shuxiangma
01:08:18
prottay
01:08:47
One of the main assumption to perform the isobar study was background in two systems will be same, now it is shown to be different....Then is the main aim achieved?
Xin-Nian Wang (LBNL)
01:12:15
Same question here: what is the consequences of the multiplicity distribution and v2 difference for the background to CME signal ? Should they be different for the two isobar collisions?
Fuqiang Wang
01:12:40
The next step is to understand the background difference to precision of the level of sub-percent (much better than 1%) needed to look for possibly small CME signal.
Prithwish Tribedy
01:13:23
v2 difference is taken care of in the observables, multiplicity difference will be discussed in the following slides
prottay
01:13:50
ok thanks
David Morrison
01:21:14
Will today’s slides be uploaded to the Indico page?
Rongrong Ma
01:22:03
Yes, we will collect the slides and upload to Indico.
Xin-Nian Wang (LBNL)
01:23:29
Question: do we understand why the ratio is smaller than 1?
Fuqiang Wang
01:24:22
Because the multiplicity ratio is larger than 1. The Delta gamma is inversely proportional to multiplicity. That's a trivial multiplicity dilution effect.
Karen McNulty Walsh
01:24:42
Brookhaven Lab press release now posted: https://www.bnl.gov/newsroom/news.php?a=119062
angel
01:25:23
p.s. the article is posted already: https://arxiv.org/pdf/2106.09243.pdf
Prithwish Tribedy
01:26:00
This is not the right article
Rongrong Ma
01:26:11
That was a different article.
Md Rihan Haque
01:27:10
Can this analysis be done in Nch (corrected) instead of centrality ? v2 should be consistent in Nch binning rather than in centrality binning.
Fuqiang Wang
01:27:15
The ratio is lower than 1 simply because of the multiplicity difference. We should look at N*\Delta\gamma/v2.
Derek Teaney
01:27:22
Is the first thing to understand, implied by slide 21, why 1/Ntrk lower for Zr and Ru …
Roy Lacey
01:28:34
the background difference between both isobars will be explicitly measured
Fuqiang Wang
01:29:29
Ru is slightly smaller than Zr, so RuRu energy density is slightly higher, so the multiplicity is slightly higher. That's why the Ru/Zr ratio of inverse multiplicity (1/N) is below 1.
Derek Teaney
01:29:53
Thanks Fuqiang
Rongrong Ma
01:29:55
The correct link to the paper is: https://drupal.star.bnl.gov/STAR/files/starpublications/362/STAR_IsobarCME_aug31_2021.pdf
Thomas Schaefer
01:30:37
I guess nobody ever looked at elliptic flow + neutron skin background?
Jinfeng L
01:31:08
@Thomas: both Fuqiang and we looked at that.
Fuqiang Wang
01:31:21
Actually we did, and predicted the difference of 2-3%.
Xin-Nian Wang (LBNL)
01:31:30
So the next step is to understand quantitatively the effect of the multiplicity difference and the effect on the CME signals
Jinfeng L
01:31:33
@Thomas: and that is why we suggested to use explicit cut for making sure that the two isobar samples are identical
Fuqiang Wang
01:32:03
PHYSICAL REVIEW LETTERS 121, 022301 (2018)
Md Rihan Haque
01:32:11
measuring gamma in Nch binning there would be two control: 1. similar v2, 2. Similar dilution of signal.
Prithwish Tribedy
01:32:36
Multiplicity dependence affects the third order CME insensitive variable in a similar way, they are consistent with CME sensitive observables
Jie Zhao
01:32:50
@angel “p.s. the article is posted already: https://arxiv.org/pdf/2106.09243.pdf“ this paper is AuAu result using spectator and participant planes, not isobar data
Jurgen Schukraft
01:34:33
@xinnian: Unfortunately the sign is wrong, so no easy way to look for a smaller signal. First one has to fond a larger background..
Fei Li
01:34:52
except the neutron skin, the different deformation of Ru and Zr seems to also lead to the difference of v2
Jinfeng L
01:35:13
@Jurgen: I am not sure the sign is wrong. It depends a correct baseline!
Jurgen Schukraft
01:35:51
Ru < Zr, while inverse is predicted. That is what I mean by sign..
Md Rihan Haque
01:36:34
yes, there are opposite predictions on which one is more deformed..
Fuqiang Wang
01:36:57
@Jurgen @Jinfeng With N*Dgamma/v2, the ratio would be above 1, but we do need to understand better nonflow effects.
Jurgen Schukraft
01:37:04
Sorry Ru > Zr
angel
01:37:08
@Jie Zhao yes sorry it was the wrong one. @Rongrong Ma shared the correct one above!