STAR Flow, Chirality and Vorticity PWG

[James Dunlop <dunlop AT bnl.gov>]

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 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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