STAR Flow, Chirality and Vorticity PWG

["Huan Zhong Huang" <huang AT physics.ucla.edu>]

No, I am not sure that it is the way to look at this. I do not care about 
your measured vertex Gaussian from tracks and not interested in the tail of 
that Gaussian. What I want to know is if you produce 4000 particles from 
0.480 mm or from 0.520 mm position in X, what would STAR TPC measure. 399.5 
or 400 particles, any difference at all?
Huan

-----Original Message-----
From: James Dunlop <dunlop AT bnl.gov> 
Sent: Tuesday, April 26, 2022 4:54 PM
To: Huan Zhong Huang <huang AT physics.ucla.edu>; STAR Flow, Chirality and 
Vorticity PWG <star-fcv-l AT lists.bnl.gov>
Cc: James Dunlop <dunlop AT bnl.gov>; Jiangyong Jia 
<jiangyong.jia AT stonybrook.edu>
Subject: Re: [Star-fcv-l] STAR presentation by Haojie Xu for Quark Matter 
2022 submitted for review

The beam shifts by ~40 um all the time.  It's beam steering at that level,  
often used to level our luminosity.

The Gaussian in Vx for average tracks is ~1 cm sigma, of which we keep 3 
sigma at 3 cm.
The effect of a 40 um shift is to move that from (-3,3) to (-3.004,2.996)

I am not able to see the difference in the precision of root, looks like it's 
in the 7th decimal place
TF1 *g = new  TF1("g","1./sqrt(2*3.14159265)*exp(-x*x/2)",-20,20)
root.exe [14] g->Integral(-3.004,2.996)
(Double_t)9.97299991776104733e-01
root.exe [15] g->Integral(-3,3)
(Double_t)9.97300204506530563e-01



> On Apr 26, 2022, at 7:33 PM, Huan Zhong Huang via Star-fcv-l 
> <star-fcv-l AT lists.bnl.gov> wrote:
> 
> Hi Jiangyong, All,
>  I am not claiming that the beam position difference is the sole reason for 
> the multiplicity difference between RuRu and ZrZr. I am being a devil's 
> advocate here. I have not seen any study or simulations to quantitatively 
> demonstrate the possible magnitude of the change. If I look at the vertex 
> results from Haojie and attribute the difference in RuRu data to the <Vx> 
> change, then I would estimate 0.5 track change for 60 um <vx> shift. How do 
> I know if this is wrong? Can simulations show what magnitude corresponding 
> to 40 um beam shift? Do you want to show, if there is a systematic error 
> 0.4 track shift out of 300-400 tracks, the systematic error on the ratio 
> that is used to evaluate the nuclear shape? We were not trying to explain 
> the RuRu and ZrZr difference by a constant shift. If there is an 
> efficiency-like issue, it may be a multiplicative factor. We were not 
> positioned to do the simulations. But the sensitivity on the accuracy of 
> the multiplicity does require us to examine the possible beam shift effect 
> quantitatively.
>  Thanks. Regards,
>  Huan
> 
> -----Original Message-----
> From: Star-fcv-l [mailto:star-fcv-l-bounces AT lists.bnl.gov] On Behalf 
> Of Jiangyong Jia via Star-fcv-l
> Sent: Tuesday, April 26, 2022 12:35 PM
> To: star-fcv-l AT lists.bnl.gov
> Subject: Re: [Star-fcv-l] STAR presentation by Haojie Xu for Quark 
> Matter 2022 submitted for review
> 
> Hi, Huan, haojie etc.
> 
> Though this investigation is interesting and should continue, I believe the 
> 40 um shift can not be responsible for the 1.5 track or 0.8% difference 
> between Ru+Ru and Zr+Zr.
> 
> The reason: if any, the change dNch should be proportional to the 
> difference in vertex dr if this is vertex dependent tracking efficiency . 
> If dr=40um leads to dNch/Nch=0.8%, then dr=4mm would lead to dNch/Nch=80%, 
> clearly not possible!  Besides, we also know the p(Nch)_Ru and p(Nch)_Zr 
> has different shapes, and one can not remove the difference by a Re-scaling.
> 
> I also do not understand why one think vertex shift should cause Nch to be 
> shifted by a constant independent of centrality.
> 
> Maybe I
> Cheers,
> Jiangyong
> 
> On 4/26/22 3:28 AM, haojiexu via Star-fcv-l wrote:
>> Hi Huan,
>> 
>> I am sorry I may not get your point.
>> 
>> If we think the vertex variations come from real beam position 
>> variations, why do we just focus on the few outlier runs, but ignore 
>> the variations for the rest of the runs? These variations could be 
>> also larger than 40 um. It would be a good question why the first few 
>> runs (in blue, see the attached file) have large offsets in refmult, 
>> but this small piece of the dataset will not change our conclusions.
>> Actually, if we put a tough cut on refmult,i.e 2sigma, most of these 
>> outliers can be regarded as bad runs, see figure 2 in attachment.
>> 
>> with best regards,
>> Haojie
>> 
>> 
>> 
>> 
>> 
>> On 2022-04-26 13:27, Huan Zhong Huang wrote:
>>> Hi Haojie,
>>>  Even if I looked at your Fig. 2, I would conclude that the data 
>>> support the same hypothesis.
>>>  Fig.1 showed that <Vx> = -540 um with RMS 20 um for RuRu, and -582 
>>> um with RMS 18 um. I do not know enough about the beam properties to 
>>> interpret whether the RMS about 20 um is entirely due to beam 
>>> position variation or combination of beam position and vertex 
>>> reconstruction resolutions. So if I want to make sure that I look at 
>>> events truly from beam position variation, then I need to look at 
>>> runs out side of the central blob. You can see these <Vx> outlier 
>>> runs in both Fig. 1 and Fig. 2 for RuRu collisions. Clearly you 
>>> observe a multiplicity variation with the beam position. Since we 
>>> examine the same RuRu collisions, the difference may be due to the beam 
>>> position change.
>>>  Then you see that there is a 42 um difference in beam position 
>>> between RuRu and ZrZr. There could be multiplicity variations due to 
>>> the position difference.
>>>  When you make your interesting ratios with different regions, 
>>> please state your assumptions. Then we can learn whether the 
>>> assumptions are valid or need further justification.
>>>  Thanks. Regards,
>>>  Huan
>>> 
>>> -----Original Message-----
>>> From: haojiexu <haojiexu AT rcf.rhic.bnl.gov>
>>> Sent: Monday, April 25, 2022 7:39 PM
>>> To: Huan Zhong Huang <huang AT physics.ucla.edu>
>>> Cc: 'STAR Flow, Chirality and Vorticity PWG'
>>> <star-fcv-l AT lists.bnl.gov>; 'ShinIchi Esumi'
>>> <esumi.shinichi.gn AT u.tsukuba.ac.jp>
>>> Subject: Re: [Star-fcv-l] STAR presentation by Haojie Xu for Quark 
>>> Matter 2022 submitted for review
>>> 
>>> Hi Huan,
>>> 
>>> Thank you for the comment.
>>> The results show in Fig.3 are just two specific small run periods. I 
>>> think we should focus on Fig. 2 (the full runIds) instead of Fig. 3.
>>> The obvious Ref-vx correlations shown in Fig.3 is only because we 
>>> select few runIds that have large offset, see the Ref-vx 
>>> distribution in Fig.2, and rest of the runIds are quite symmety 
>>> around their center. Actually, if we select two other subsets of 
>>> runIds in Figures 2, we can get any correlaitons that we want. For 
>>> example, if we chose some other run periods in RuRu, say 300-330 and 
>>> 350-380, we will get Ref-vx correlations opposite to Fig.3.
>>> 
>>> I don't see any issue for the comparing in a signle system or two 
>>> system. The only different is that we only need two sets of 
>>> comparisons instead of four show in Fig.5. If there is any 
>>> difference in one system, it will directly affect the ratios between 
>>> the two systems. Since our goal is the ratio between two system, I 
>>> think it is better to show all the comparisons.
>>> 
>>> with best regards,
>>> Haojie
>>> 
>>> On 2022-04-26 09:33, Huan Zhong Huang wrote:
>>>> Hi Haojie,
>>>>  Thanks for the update.
>>>>  In order to see any multiplicity shift due to vertex position 
>>>> difference, one has to focus on the same collision system, not 
>>>> comparing the two isobar systems. The figure that points to 
>>>> potential vertex related multiplicity effect is the Figure 3. If 
>>>> you examine the
>>>> Ru+Ru and Zr+Zr data separately, one conclusion may be that a 
>>>> Ru+slight
>>>> shift in <Vx> changes the multiplicity (middle panel Ru+Ru), when 
>>>> Vx change small corresponding multiplicity shift small too (Zr+Zr); 
>>>> the <Vy> change does not cause multiplicity shift (bottom panel Zr+Zr).
>>>> Then the multiplicity shift of Ru+Ru as a function of <Vr> and <Vy> 
>>>> was actually caused by the underlying <Vx> shift. This 
>>>> interpretation would be consistent with your measurements.
>>>>   I tend to think that these are the more sensitive aspects of your 
>>>> results in these figures.
>>>>  Thanks.
>>>>  Huan
>>>> 
>>>> -----Original Message-----
>>>> From: Star-fcv-l <star-fcv-l-bounces AT lists.bnl.gov> On Behalf Of 
>>>> haojiexu via Star-fcv-l
>>>> Sent: Monday, April 25, 2022 4:24 PM
>>>> To: ShinIchi Esumi <esumi.shinichi.gn AT u.tsukuba.ac.jp>; STAR Flow, 
>>>> Chirality and Vorticity PWG <star-fcv-l AT lists.bnl.gov>
>>>> Subject: Re: [Star-fcv-l] STAR presentation by Haojie Xu for Quark 
>>>> Matter 2022 submitted for review
>>>> 
>>>> Hi SchinIchi,
>>>> 
>>>> Thank you for the comments. Yes, the plots on page 4 are all e-by-e 
>>>> quantities, I have corrected the titles.
>>>> I also add two plots on the same page under your suggestion. 
>>>> Attached please find the new version.
>>>> 
>>>> with best regards,
>>>> Haojie
>>>> 
>>>> On 2022-04-25 11:23, ShinIchi Esumi via Star-fcv-l wrote:
>>>>> Dear Haijie
>>>>> Thank you very much for the plots.
>>>>> Could you please re-plot the page 4 figures (x-/y- reversed axis) 
>>>>> and as profile plot, like <V_r,x,y,z> vs RefMult? And please 
>>>>> expand the vertical axis at least a few mm range...
>>>>> You have indicated "< >” in the x- and y- axis labels for all 4 
>>>>> plots, but this is not the average, they are all event-by-event 
>>>>> quantities, right?
>>>>> Best regards, ShinIchi
>>>>> 
>>>>>> 2022/04/25 8:03、haojiexu via Star-fcv-l
>>>>>> <star-fcv-l AT lists.bnl.gov>のメール:
>>>>>> 
>>>>>> Dear ShinIchi, Huan, Jie, and all,
>>>>>> 
>>>>>> Thank you for the suggestions. The comparison between two 
>>>>>> different run periods is shown on page 3 of the attached file. 
>>>>>> The correlation in RuRu collision is just a coincidence, as we do 
>>>>>> not see any obvious correlations for the rest of the runs.
>>>>>> 
>>>>>> The second page is for run-by-run distributions. I also made a 
>>>>>> plot for e-by-e distributions on page 4. As I have mentioned in 
>>>>>> the last FCV meeting, these distributions are due to the 
>>>>>> multiplicity-dependent vertex resolutions.
>>>>>> 
>>>>>> Therefore, as mentioned by Fuqiang, we can not re-weight or cut 
>>>>>> events at the event level due to resolutions. I then apply the 
>>>>>> cut on run level, i.e., divide the events into two groups by 
>>>>>> run-by-run mean vx and vy, the results are shown on page 5. The 
>>>>>> distributions are almost the same in two different <vx> and <vy> 
>>>>>> groups, which confirm that no efficiency difference over vx, vy 
>>>>>> variations on this level.
>>>>>> 
>>>>>> The mean multiplicity difference between Ru+Ru and ZrZr is about 
>>>>>> 0.2% in the high multiplicity range, as I have shown in my QM talk.
>>>>>> One bin shift will cause ~0.16% differences in the mean 
>>>>>> multiplicity ratio. To achieve our goal on determine the slope 
>>>>>> parameter of symmetry energy, if any effect causes a difference 
>>>>>> above ~0.02%, I will consider such effect seriously. The effect 
>>>>>> shown on page 5 is only about ~0.002%, negligible in our measurements.
>>>>>> 
>>>>>> Yes, the shape differences are very important in our study and 
>>>>>> very sensitive at high multiplicity range. That’s the reason we 
>>>>>> put more effort into the refined centrality in isobar collisions.
>>>>>> We found the shape corrections from previous official centrality 
>>>>>> definition are quite large, which will cause large sys 
>>>>>> uncertainties in our study.
>>>>>> We then improved vz corrections and now such uncertainty is 
>>>>>> negligibly small.  I think this may answer Huan’s question about 
>>>>>> the efficiency effect on multiplicity distribution shape at the 
>>>>>> very tail region, as the efficiency do have vz dependent but only 
>>>>>> affects the high-end-point value. Here are my slides from the 
>>>>>> last collaboration meeting for your reference
>>>>>> 
>>>>>> https://drupal.star.bnl.gov/STAR/system/files/FCV20220216.pdf
>>>>>> 
>>>>>> Again, thank you for the suggestions.
>>>>>> 
>>>>>> With best regards,
>>>>>> Haojie
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> On 2022-04-24 00:39, Wang, Fuqiang via Star-fcv-l wrote:
>>>>>>> Hi, Huan, Jie,
>>>>>>> Yes, cutting or reweighting events will be biasing the events.
>>>>>>> Haojie’s highend point multiplicity vs Vx, Vy already showed that.
>>>>>>> The vx vy distributions are mainly due to the vertex position 
>>>>>>> resolutions therefore dependent on event multiplicity. Cutting 
>>>>>>> on them is cutting on resolution. One cannot apply cuts or 
>>>>>>> selection on event level, but only on runs or run periods.
>>>>>>> Best regards,
>>>>>>> Fuqiang
>>>>>>> On Apr 23, 2022, at 3:02 AM, Huan Zhong Huang via Star-fcv-l 
>>>>>>> <star-fcv-l AT lists.bnl.gov> wrote:
>>>>>>>> Hi Jie,
>>>>>>>> That is an interesting idea. I do not know enough about beam 
>>>>>>>> physics to have a firm answer. I assume that the actual beam 
>>>>>>>> size is much smaller than the measured Vx and Vy distributions, 
>>>>>>>> but the center value should be correct beam position. 
>>>>>>>> Therefore, the measured Vx, Vy width may be mostly due to track 
>>>>>>>> resolutions. Then if you only take events on one side of the 
>>>>>>>> resolution function in order to match the RuRu and ZrZr 
>>>>>>>> distributions, I do not know if it will introduce any bias.
>>>>>>>> Regards,
>>>>>>>> Huan
>>>>>>>> From: Jie Zhao <jiezhao1119 AT hotmail.com>
>>>>>>>> Sent: Friday, April 22, 2022 5:21 PM
>>>>>>>> To: Huan Zhong Huang <huang AT physics.ucla.edu>; STAR Flow, 
>>>>>>>> Chirality and Vorticity PWG <star-fcv-l AT lists.bnl.gov>
>>>>>>>> Cc: ShinIchi Esumi <esumi.shinichi.gn AT u.tsukuba.ac.jp>
>>>>>>>> Subject: Re: [Star-fcv-l] STAR presentation by Haojie Xu for 
>>>>>>>> Quark Matter 2022 submitted for review Dear Huan, ShinIchi, 
>>>>>>>> Haojie, i am wondering, whether a data driven method would be 
>>>>>>>> helpful or not, for example, artificially weight or throw away 
>>>>>>>> part of the RuRu data to match the ZrZr vx/vy/vz distribution, 
>>>>>>>> and see how big the difference?
>>>>>>>> Best regards,
>>>>>>>> Jie
>>>>>>>> On Apr 23, 2022, at 3:56 AM, Huan Zhong Huang via Star-fcv-l 
>>>>>>>> <star-fcv-l AT lists.bnl.gov> wrote:
>>>>>>>> Dear Haojie and ShinIchi,
>>>>>>>> Thanks for the update and sorry for the late response. It is 
>>>>>>>> very typical nowadays that I lag behind in my email responses.
>>>>>>>> On a gross scale, I do not have any problem if you claim that 
>>>>>>>> there is no effect related to vertex and/or efficiency 
>>>>>>>> differences. But when you focus on the ratio at the very tail 
>>>>>>>> region, we know that the sensitivity is very much enhanced. So 
>>>>>>>> I have not seen any quantitative estimate that demonstrated 
>>>>>>>> that there is nothing to worry about.
>>>>>>>> When you examine the multiplicity and the vertex positions to 
>>>>>>>> see if there is any correlations, you did it as a function of 
>>>>>>>> run number. I am afraid that this approach may not be a sensitive 
>>>>>>>> way.
>>>>>>>> As you may know the vertex position averaged over a run 
>>>>>>>> contains too many effects including the z vertex and the slope 
>>>>>>>> parameters which may be run dependent. You may be better off to 
>>>>>>>> focus on data within one run. I understand that you have 
>>>>>>>> already done the Vz dependent corrections. So you may ask the 
>>>>>>>> question whether you correctly attributed the physical reason 
>>>>>>>> for the Vz correction and whether the correction method (for 
>>>>>>>> the turning point, instead of the falling shape for example) is well 
>>>>>>>> justified.
>>>>>>>> When I suggested you to carry out quantitative systematic 
>>>>>>>> estimate, it probably does not make sense to you. Let me try to 
>>>>>>>> elaborate a little. Since you focus on the ratio of 
>>>>>>>> multiplicity in the tail region, you may check how the ratio 
>>>>>>>> changes with possible multiplicity shift (more detailed and 
>>>>>>>> finer steps than Yu did).
>>>>>>>> Then if you decide that in order to constrain nuclear shape 
>>>>>>>> parameters well using the ratios in the tail region, you may 
>>>>>>>> decide our goal of systematic error allowed. That would be our 
>>>>>>>> quantitative goal for controlling the systematics for this 
>>>>>>>> physics measurement.
>>>>>>>> Once you know the goal that you need to achieve, you may be 
>>>>>>>> able to examine if your Vz/Vx/Vy studies are compatible with 
>>>>>>>> achieving the goal. We know that the average multiplicity 
>>>>>>>> between Ru+Ru and
>>>>>>>> Zr+Zr differ by a few counts while the average Vx and Vy are
>>>>>>>> slightly different. I wondered that among these two refmult 
>>>>>>>> difference how much should be attributed to true shape 
>>>>>>>> difference and how much to run condition difference. What makes 
>>>>>>>> you so confident that there is no effect from vertex difference 
>>>>>>>> at the accuracy level that we need to achieve. If we trust the 
>>>>>>>> simulation package, we may have to simulate the same collisions 
>>>>>>>> with a slight shift in vertex positions in order to guage the 
>>>>>>>> sensitivity.
>>>>>>>> In any case, thanks for the hard work.
>>>>>>>> Regards,
>>>>>>>> Huan
>>>>>>>> -----Original Message-----
>>>>>>>> From: Star-fcv-l <star-fcv-l-bounces AT lists.bnl.gov> On Behalf 
>>>>>>>> Of ShinIchi Esumi via Star-fcv-l
>>>>>>>> Sent: Thursday, April 21, 2022 8:58 PM
>>>>>>>> To: STAR Flow, Chirality and Vorticity PWG 
>>>>>>>> <star-fcv-l AT lists.bnl.gov>
>>>>>>>> Subject: Re: [Star-fcv-l] STAR presentation by Haojie Xu for 
>>>>>>>> Quark Matter 2022 submitted for review Dear Haojie Thanks for the 
>>>>>>>> plots.
>>>>>>>> I have one question.
>>>>>>>> Is the second page for the entire run and event for both RuRu 
>>>>>>>> and ZrZr?
>>>>>>>> Could you plot the 2nd page correlation just for the two run 
>>>>>>>> ranges for each of 2 species, where you draw 2 black lines (run
>>>>>>>> ranges) in each panel of the 1st page, and plot one range for 
>>>>>>>> red and another range for blue points?
>>>>>>>> Could you also plot each point event-by-event, not run-by-run 
>>>>>>>> for these two run ranges.
>>>>>>>> Best regards, ShinIchi
>>>>>>>> On Apr 22, 2022, at 10:33, haojiexu <haojiexu AT rcf.rhic.bnl.gov>
>>>>>>>> wrote:
>>>>>>>> Dear ShinIchi, Huan, and all,
>>>>>>>> Under Jiangyong's suggestion, I have plotted the run-by-run 
>>>>>>>> vertex distributions in both Ru+Ru and Zr+Zr collisions, 
>>>>>>>> attached please find the plots. The vertex variations in each 
>>>>>>>> system are larger than the average difference between the two 
>>>>>>>> systems. I also plot the <RefMult> vs <vx>, <vy> and <vr> in each 
>>>>>>>> collision system.
>>>>>>>> There is no evidence of efficiency difference over vx, vy 
>>>>>>>> variations on this level.
>>>>>>>> with best regards,
>>>>>>>> Haojie
>>>>>>>> On 2022-04-21 20:49, ShinIchi Esumi via Star-fcv-l wrote:
>>>>>>>> Dear Huan and all
>>>>>>>> There were some interesting discussions about this in the PWG 
>>>>>>>> meeting yesterday, the results presented by Haojie in the 
>>>>>>>> meeting were not enough to fully answer your question (you can 
>>>>>>>> see his slide in the usual PWG agenda page at :
>>>>>>>> https://drupal.star.bnl.gov/STAR/blog/jjiastar/bulkcorr). One 
>>>>>>>> difficulty is the vertex resolution changes with centrality 
>>>>>>>> (track multiplicity in the tpc),  but there were few more 
>>>>>>>> suggestions made during the meeting, so let’s see his future 
>>>>>>>> updates. Do we just worry about the actual vertex position 
>>>>>>>> dependence of the tpc efficiency?, which is basically the 
>>>>>>>> homework for Haojie to see the vertex position (3D xyz vertex) 
>>>>>>>> dependence of efficiency (effectively number of reconstructed 
>>>>>>>> track for a given acceptance), Or do we also need to worry 
>>>>>>>> about beam tuning/focusing differences, for example, beam 
>>>>>>>> crossing angle difference etc between the species?
>>>>>>>> One thing I forgot to ask yesterday was about the simulation 
>>>>>>>> test, where we used say our accuracy of tracking efficiency is 
>>>>>>>> of the order of 5% for the systematic error evaluation in the 
>>>>>>>> absolute yield measurements, which is clearly not enough for 
>>>>>>>> these studies, so the most of the people seem to be given up in 
>>>>>>>> this direction, but I remember there were some task force 
>>>>>>>> formed sometime ago, to revisit our accuracy of 5% on the 
>>>>>>>> absolute efficiency in the tpc, and to see if we can improve this or 
>>>>>>>> not.
>>>>>>>> We need to see if there is any progress in this direction or 
>>>>>>>> not, too… Best regards, ShinIchi On Apr 15, 2022, at 11:42, 
>>>>>>>> Huan Zhong Huang <huang AT physics.ucla.edu>
>>>>>>>> wrote:
>>>>>>>> Hi ShinIchi and Haojie,
>>>>>>>> Thanks for the discussion. To pursue the physics topic, we need 
>>>>>>>> to demonstrate that we have done the systematic study to the 
>>>>>>>> accuracy of much better than 1/(300-400) in multiplicity 
>>>>>>>> measurement. We may have done lots of systematic studies, but I 
>>>>>>>> am not aware one which showed the accuracy matched what is 
>>>>>>>> needed for this physics topic.
>>>>>>>> It will be useful to keep this requirement in mind when you 
>>>>>>>> consider more studies. It would certainly be very useful to 
>>>>>>>> have a full geant simulation of Ru collisions with realistic 
>>>>>>>> beam profile and with the correct magnitude of position shifts 
>>>>>>>> to see any effect.
>>>>>>>> Haojie: if you think that your previous results have the 
>>>>>>>> accuracy needed, please summarize your results/arguments in a 
>>>>>>>> few slides to circulate. In particular, we will be interested 
>>>>>>>> in why you think that you have the quantitative accuracy of 
>>>>>>>> 1/(300-400).
>>>>>>>> Thanks. Regards,
>>>>>>>> Huan
>>>>>>>> -----Original Message-----
>>>>>>>> From: Star-fcv-l <star-fcv-l-bounces AT lists.bnl.gov> On Behalf 
>>>>>>>> Of ShinIchi Esumi via Star-fcv-l
>>>>>>>> Sent: Wednesday, April 13, 2022 7:50 PM
>>>>>>>> To: STAR Flow, Chirality and Vorticity PWG 
>>>>>>>> <star-fcv-l AT lists.bnl.gov>
>>>>>>>> Subject: Re: [Star-fcv-l] STAR presentation by Haojie Xu for 
>>>>>>>> Quark Matter 2022 submitted for review Dear Haojie Thank you 
>>>>>>>> for the confirmation. The question is how accurately we do know 
>>>>>>>> the relative efficiency difference between species, compared to 
>>>>>>>> the observed level of multiplicity difference of ~1/(a few 
>>>>>>>> 100). TPC condition itself is unchanged as we filled two beams 
>>>>>>>> alternatively, but the beam optics/position seems to be different.
>>>>>>>> The effect coming from less than mm difference of beam using 
>>>>>>>> the meter size detector would be small, but we just need to 
>>>>>>>> make sure the effect is at lease much smaller than ~1/(a few 
>>>>>>>> 100) in the realistic experimental condition.
>>>>>>>> Best regards, ShinIchi
>>>>>>>> On Apr 14, 2022, at 11:35, haojiexu <haojiexu AT rcf.rhic.bnl.gov>
>>>>>>>> wrote:
>>>>>>>> Dear ShinIchi,
>>>>>>>> The efficiency corrections are not implemented yet. As we have 
>>>>>>>> discussed during my presentation, we plan to use the same 
>>>>>>>> efficiency for two isobar systems, as the accuracy may not be 
>>>>>>>> good enough to do it separately.
>>>>>>>> with best regards,
>>>>>>>> Haojie
>>>>>>>> On 2022-04-14 09:29, ShinIchi Esumi via Star-fcv-l wrote:
>>>>>>>> Dear Haojie and all
>>>>>>>> I think Huan has a point, if the tracking efficiency is really 
>>>>>>>> different between the two species caused by the small beam 
>>>>>>>> shift (or any beam related systematic difference), the beam 
>>>>>>>> luminosity and/or zvertex corrections for the refmult would not 
>>>>>>>> correct such difference, since
>>>>>>>> “97 vs 98” difference remain unchanged after the corrections 
>>>>>>>> and this difference of “1 out of 500” that we believe that it 
>>>>>>>> is coming from the nuclear structure, but I‘m not sure we have 
>>>>>>>> ruled out any small fraction of “1” that might be coming from 
>>>>>>>> the beam systematics or not.
>>>>>>>> Do we correct for the tracking efficiency (for the refmult) 
>>>>>>>> independently between two species?
>>>>>>>> This might be a question of accuracy of our embedding 
>>>>>>>> simulation, that does use the real data, but how precisely we 
>>>>>>>> can reproduce the beam quality/position difference for the 
>>>>>>>> embedded track to be combined into the real events for each 
>>>>>>>> species independently. Or we might need to test this with full 
>>>>>>>> geant simulation with realistic beam optics/profile, to see if 
>>>>>>>> our TPC (with realistic holes of inactive RDOs etc) is 
>>>>>>>> sensitive to this or not. This is to ask ourselves, if we 
>>>>>>>> already know our TPC efficiency (better than
>>>>>>>> ~1/500) relatively between two species, that is being questioned.
>>>>>>>> Best regards, ShinIchi
>>>>>>>> 2022/04/14 9:41、haojiexu via Star-fcv-l 
>>>>>>>> <star-fcv-l AT lists.bnl.gov>
>>>>>>>> のメール：
>>>>>>>> Hi Huan,
>>>>>>>> Thank you for your comments and interest in my QM talk. And 
>>>>>>>> also thank Yu for the testing on multiplicity shift, the effect 
>>>>>>>> of one bin offset is large but I don’t think this shift is reliable.
>>>>>>>> The multiplicity ratios shown in my QM slides are not the raw 
>>>>>>>> multiplicity distributions. As it was done in the general 
>>>>>>>> centrality definition procedure, we have corrected the 
>>>>>>>> luminosity dependent and the multiplicity distributions in 
>>>>>>>> different vz bins are corrected to vz=0. I think the effect you 
>>>>>>>> mentioned has been taken care of by the procedures. More 
>>>>>>>> details of the procedure can be found in my presentation given 
>>>>>>>> in the centrality definition
>>>>>>>> meeting:
>>>>>>>> https://drupal.star.bnl.gov/STAR/system/files/Centrality20220301.
>>>>>>>> pdf Yes, the neutron skin effect can also be obvious at 
>>>>>>>> peripheral collisions. One of the observables is the net charge 
>>>>>>>> ratios I have shown in my QM presentation.
>>>>>>>> with best regards,
>>>>>>>> Haojie
>>>>>>>> On 2022-04-12 03:19, Huan Zhong Huang wrote:
>>>>>>>> Hi Haojie et al,
>>>>>>>> This is an interesting approach. I am concerned whether you 
>>>>>>>> have done the systematic checks to demonstrate the sensitivity 
>>>>>>>> of potential systematic bias to the physics conclusion. Yu Hu 
>>>>>>>> helped to plot the multiplicity ratio of Ru+Ru/Zr+Zr if the 
>>>>>>>> multiplicity of the Zr+Zr collisions is systematically offset by a 
>>>>>>>> few tracks.
>>>>>>>> When the Zr multiplicity is shifted by one track out of 300-400 
>>>>>>>> tracks, the ratio changes very significantly. Therefore, it is 
>>>>>>>> critical that we show that there is no systematic bias between 
>>>>>>>> two isobar collisions even at one particle level.
>>>>>>>> Because of the isobar charge difference, I tried to ask CAD 
>>>>>>>> what the possible magnitude of beam difference (position and 
>>>>>>>> collision axis).
>>>>>>>> Bill Christie suggested that we should be able to get the data 
>>>>>>>> from reconstructed vertex distributions as a function of Z. 
>>>>>>>> Gene Van Buren has some data on this. He indicated that the 
>>>>>>>> beam position between Ru and Zr could be shifted by 40-50 
>>>>>>>> microns. We may need to examine this shift with the full isobar 
>>>>>>>> data. In order to examine if this magnitude of beam shift will 
>>>>>>>> cause any systematic bias in the measured multiplicity, we may 
>>>>>>>> need to use GEANT simulations of the Ru+Ru collisions and shift 
>>>>>>>> the beam position to measure potential change in the TPC 
>>>>>>>> multiplicity.
>>>>>>>> That would ensure that we have a good control of the systematics.
>>>>>>>> There may be other approaches to use experimental data to 
>>>>>>>> examine the potential shift due to beam variations. But I do 
>>>>>>>> not know how well we can control the systematics with the 
>>>>>>>> experimental approach.
>>>>>>>> If this potential systematic shift is real, we may have to 
>>>>>>>> revisit the model used for centrality definition as well.
>>>>>>>> Naively I would expect that the peripheral collisions would be 
>>>>>>>> more sensitive to the shape and distribution of the neutron skin.
>>>>>>>> In any case, this is an interesting topic. It would be good if 
>>>>>>>> you help evaluate these sensitivity issues. I am sorry that it 
>>>>>>>> took me long to catch up with many interesting QM talks and did 
>>>>>>>> not comment sooner.
>>>>>>>> Thanks. Regards,
>>>>>>>> Huan
> 
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