STAR task force for evaluating tracking efficiency uncertainty

["Van Buren, Gene" <gene AT bnl.gov>]

Hi, all

> On Oct 20, 2022, at 8:38 AM, Ma, Rongrong via Star-tf-trkeff-l 
> <star-tf-trkeff-l AT lists.bnl.gov> wrote:
> 
> Hello Robert
> 
> Thanks a lot. The new fit looks very nice, and the p1 value is very close 
> to what we have seen based on Jpsi width from Run18 Isobar data.

So the fit is actually p0 + p1 *pT, and the finding is that p1 is 0.0075.

If we focus on the high pT region, then I think we can all agree that the 
relative resolution of pT (the absolute resolution of pT, divided by pT) is 
equal to the relative resolution of (1/pT), and that these rise linearly in 
pT. This relation can be derived from the understanding that the TPC measures 
points in physical space with a generally pT-independent spatial resolution, 
such that the absolution resolution of (1/pT) is generally constant at high 
pT. That constant is p1:

dpT / pT = d(1/pT) / (1/pT)
=>
relative resolution = p1 / (1/pT) = p1 * pT

Rongrong's study has me a little confused. Is his momentum resolution the 
relative resolution, or the absolute resolution? If it is relative 
resolution, then his "a" parameter is the same as p1, determining the high pT 
behavior of the resolution.

Past studies have shown (see the links I sent)  that p1 for tracks without a 
primary vertex in their fit get values near 0.01.  The cosmic ray study I did 
got something like 0.014. I managed to find one of the Monte Carlo QA plots 
from 2016 when the S&C team was trying to get HFT tracking working:
https://www.star.bnl.gov/~jwebb/2016/BaseQA_April_13/evals1/pidPtiRGl_zy_1.png
In that plot we can see a rise of ~0.008 between pT = 2 GeV/c to 3 GeV/c, so 
perhaps as good as 0.008 with the HFT.

Robert's result of 0.0075 manages to get close to that even without the HFT. 
And Rongrong's past results of 0.0054 are much better, and his 0.0035 number 
from embedding blows that away. I don't see how we could have ever had it 
that good.

So, I'm confused about these numbers and findings. If someone understands 
something I've missed, please let me know.

> So we have a good consistency here. I really appreciate if you can help 
> analyze other datasets (Run11, 14, 19) as well. Hopefully, this won't take 
> too much of your time. 
> 
> Gene: is it possible that you can restore cosmic ray data from Run11, Run14 
> and Run19? I think a quarter of the Run18 statistics used here for each 
> dataset is probably sufficient. 

Run 11, I see P11id FullField and ReverseFullField MuDsts that I will restore.

Run 14, I see P14ih Half, Fulll, and ReverseFullField MuDsts that I will 
restore.

Run 19, I do not think we did an official production, but I believe Yuri 
handled a private production for use in TPC calibration work. We can do an 
official production if it is desired.

Thanks,
-Gene

> 
> 
> Best
> Rongrong
> 
>> On Oct 20, 2022, at 8:21 AM, Robert Líčeník <licenik AT ujf.cas.cz> wrote:
>> 
>> Hello Rongrong,
>> 
>> since the y axis is log-scale (but the values are not), a simple linear 
>> function will not work, so I think you meant something like p0 + p1*10^x . 
>> It seems to do much better.
>> Here are the updated slides:
>> https://drupal.star.bnl.gov/STAR/event/2022/10/18/Tracking-Efficiency-Uncertainty-meeting/Cosmics-2018-update
>> Would it be helpful if I shared the file with the produced TTree with you? 
>> That way you can have a quick look by yourself and you don't have to wait 
>> for me in a different time zone every time.
>> However, I understand that you are very busy and I am of course more than 
>> happy to help.
>> 
>> Cheers,
>> Robert
>> 
>> On Wed, Oct 19, 2022 at 8:06 PM Ma, Rongrong <marr AT bnl.gov> wrote:
>> Hello Robert
>> 
>> Could you try a linear function y = p0 + p1*x to do the fit? Thanks. 
>> 
>> Best
>> Rongrong
>> 
>>> On Oct 19, 2022, at 11:55 AM, Robert Líčeník <licenik AT ujf.cas.cz> wrote:
>>> 
>>> Hi Rongrong,
>>> 
>>> you are correct. The fit function is written on the first slide with 
>>> momentum resolution and the range is the full histogram for the red fit 
>>> and (-0.4 - 2) for the blue fit.
>>> 
>>> Cheers,
>>> Robert
>>> 
>>> On Wed 19. 10. 2022 at 17:40 Ma, Rongrong <marr AT bnl.gov> wrote:
>>> Hi Robert
>>> 
>>> Thanks for the update. However, the fit does not seem to work well. What 
>>> function and fit range are you using? Thanks. 
>>> 
>>> Best
>>> Rongrong
>>> 
>>>> On Oct 19, 2022, at 9:05 AM, Robert Líčeník <licenik AT ujf.cas.cz> wrote:
>>>> 
>>>> Hi Rongrong,
>>>> 
>>>> no problem, here are the updated slides:
>>>> https://drupal.star.bnl.gov/STAR/event/2022/10/18/Tracking-Efficiency-Uncertainty-meeting/Cosmics-2018-update
>>>> 
>>>> Cheers,
>>>> Robert
>>>> 
>>>> On Tue, Oct 18, 2022 at 11:00 PM Ma, Rongrong <marr AT bnl.gov> wrote:
>>>> Hello Robert
>>>> 
>>>> Thanks. If possible, could you redo the fit starting from the lowest 
>>>> point, i.e. log(pt) ~ -0.4, and add the slope of the fit to the figures? 
>>>> 
>>>> Best
>>>> Rongrong
>>>> 
>>>>> On Oct 18, 2022, at 2:38 PM, Robert Líčeník via Star-tf-trkeff-l 
>>>>> <star-tf-trkeff-l AT lists.bnl.gov> wrote:
>>>>> 
>>>>> Hi everyone,
>>>>> I uploaded my slides from today's meeting:
>>>>> https://drupal.star.bnl.gov/STAR/event/2022/10/18/Tracking-Efficiency-Uncertainty-meeting/Cosmics-2018-update
>>>>> The only difference is that I replotted the momentum resolution figures 
>>>>> in log-log scale, as requested. 
>>>>> Cheers,
>>>>> Robert
>>>>> 
>>>>> On Mon, Oct 17, 2022 at 12:07 PM Petr Chaloupka via Star-tf-trkeff-l 
>>>>> <star-tf-trkeff-l AT lists.bnl.gov> wrote:
>>>>> Dear All,
>>>>> 
>>>>> Please join our meeting tomorrow at 10:00 New York time.
>>>>> 
>>>>> Please upload any material for discussion to the drupal page:
>>>>> https://drupal.star.bnl.gov/STAR/event/2022/10/18/Tracking-Efficiency-Uncertainty-meeting
>>>>> 
>>>>> With best regards,
>>>>> Petr
>>>>> 
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>>>>> 
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