STAR HardProbes PWG

[David Stewart <0ds.johnny AT gmail.com>]

Hi Nihar,

I have just a few comments on Veronica's nice explanations (thanks Veronica): They are inline below

On Fri, Jan 20, 2023 at 1:18 AM Veronica Verkest <vverkest AT gmail.com> wrote:

Hi Nihar,

I can address some of these questions and Dave can comment/supplement and answer those which I cannot.

1) SLide#6:
_ What is Y-axis "ZDCX-bin data"? how do you calculate efficiency value
from data? (Not clear)

_ are these efficiency values are pT- and eta- integrated one?

These efficiency values are integrated over pT and eta. This plot might be more visually intuitive if you ignore the 7th bin on the x-axis, as this is just the average of the bins to the left. There is a typical pT-dependence shape in the curves and some slight dependence on eta (the asymmetry of the UE means different populations and therefore different efficiency for different eta-ranges in the TPC). The data-ZDCx bins were clear to me (first seeing the plot) as it is directly from the detector, but I had to reconcile to myself that, in doing the embedding, we do get a different ZDCx. The significance here is that the efficiency curves do not vary significantly as a function of the embedding data-ZDCx, but only the embedding ZDCx. This shows us that all tracks (real and PU) from the data can be efficiency-corrected the same way, as the embedding in all ZDCx does not discriminate.

2) SLide#7:
_What is this fit parameter for rho_PU? can you show some plot where do
you have this fitting?

 rho_PU is dN_chg/dEtadPhi. To investivage PU, Dave's code looks at efficiency-corrected charged track mult in data vs embedding as a function of ZDCx. After effic correction, the mult increases as a function of ZDCx. We fit this linearly then extrapolate to zero ZDCx to see the mult we expect at zero-pileup (and this has a systematic). The fit is just a linear fit of the TE-corrected chg mult.

_Are these from "ZDCX-bin embed" or "ZDCX_bin data"?

ZDCx_bin data, as we wish to correct according to the data ZDCx (the previous check was just to ensure that the UE and PU face the same efficiency in the detector).

 

3) What eta range has been used for Slide#9-13 results? And how do you
apply eta-dependence efficiency on them? A bit more elaboration is
required to understand the correction procedure?

This question of eta range is a good insight; when we measure UE (aka charged mult), we measure in the "UE region", which is defined as the area azimuthally perpendicular to the jet/trigger axis in triggered events, but in MB events we take the chg mult in the TPC in the full azimuth. When looking in triggered events, we only look azimuthally transverse to the trigger. We checked eta-dependence of embedding and will send plots to support.

 

4) As we discussed, please separate out correlated and uncorrelated sys
uncertainty. especially for slide-13-14 results.

 To walk through the answer is as follows:

Start with slide 12, which shows all the uncertainties for the EA-high and EA-low plot. They are (as listed in the slide):

(1) "Unf. with EA-hi vs norm" -- the uncertainty measured by generating the response matrix with all-EA events vs the uncertainty using a response matrix with only high-EA events. This uncertainty is common for both EA-high and EA-low events.

(2) "Unf. closure" -- this is shown here only for clarity. It is not added into the total systematic.

(3) "HadCorr 50%" -- the difference between using 100% and 50% hadronic correction

(4) "Tow. Smear Uncert" -- the difference in smearing tower Et values by 3.8% in the response matrix

(5) "Track unc. 4.5%" -- the difference in randomly removing any track with 4.5% probability in the response matrix

(6) "Track unc. 2%" -- same as (5) but with 2% instead of 5%

(7) "sys iter+2 vs -2" -- bin-by-bin the maximum of the difference in unfolding with +2 or -2 iteration vs the nominal value

Therefore, the total systematic uncertainty on the spectra themselves, is root sum square (in each bin) of (1) and (3)-(7) above. The values for each are plotted in the second panel, and labeled according for high and low EA jets.

Some of these systematics uncertainties should affect both the high-EA and low-EA events. For example, the hadronic correction (3) in high-EA and low-EA event tends to change the spectra in the same direction, and therefore should be correlated and may cancel in the ratio. Therefore, when taking the ratio, we take the nominal ratio (the ratio of points in the top bin of slide 12) and also the ratio of the data using 50% hadronic correction. The different between these ratios becomes the hadronic correction contribution to the systematic error on the ratio. If you look closely, you see that this is the case for the first bin, in which the hadronic correction systematic uncertainties in the spectra on slide 12, cancel almost entirely on in the ratio on slide 13. The same correlation allowed canceling is true of the tower smearing and 4.5% track uncertainty, (4) and (5) respectively.

The other uncertainties, (1), (6), and (7), are not taken to be entirely correlated and are dealt with as follows. For (1), this uncertainty is common to both spectra, and is added in to the sum of squared uncertainties once (not once for each spectra). (6) is carried over from both the high-EA and low-EA spectra. This is arguably over conservative and perhaps worth further discussion. (7) captures uncertainty in the unfolding, and due to small correlation between ZDCx and EA, probably doesn't cancel entirely in the ratio. Therefore, it is also carried forward into the ratio in each bin as the maximum value of the uncertainty in that bin in the EA-high spectra or that bin in the EA-low spectra.

Now, if STAR's tracking uncertainty is 

 

 

5)Slide17- I think we need to correct the y-axis (although Delta phi
correction is negligible but still we need what is that contribution
is). In this paper, all other results are corrected for detector effect
and presented with sys. uncertainty expect this Delta_phi result. It
sounds sloppy.
Same for Slide-19 Aj results.

I have considered this much myself. I do not think that the physics is lost here by not correcting--if anything, I feel that correcting this could make the plot less insightful. EA here is measured by the BBC, as we know p+A is not simple for centrality. As we investigate potential hard and soft correlations, I believe that discussing observables with respect to the minimum hardness of the jet (at a detector level) is very helpful to complement the other plots--especially the semi-inclusive jet measurement. Additionally, although not shown today since it is still under progress, the UE mult distribution as a function of leading jet pT will not be fully corrected for tracking efficiency. We have been considering working all these observables together, and it seems to make the most sense to present Aj and deltaPhi as per-dijet quantities rather than per-trigger.

Thanks so much to you and all for the attention and feedback today!

Veronica

On Thu, Jan 19, 2023 at 11:51 PM Nihar Sahoo via Star-hp-l <star-hp-l AT lists.bnl.gov> wrote:

Hi David,

  Please find my follow up comment and questions.

1) SLide#6:
_ What is Y-axis "ZDCX-bin data"? how do you calculate efficiency value
from data? (Not clear)
_ are these efficiency values are pT- and eta- integrated one?

2) SLide#7:

_What is this fit parameter for rho_PU? can you show some plot where do
you have this fitting?
_Are these from "ZDCX-bin embed" or "ZDCX_bin data"?

3) What eta range has been used for Slide#9-13 results? And how do you
apply eta-dependence efficiency on them? A bit more elaboration is
required to understand the correction procedure?

4) As we discussed, please separate out correlated and uncorrelated sys
uncertainty. especially for slide-13-14 results.

5)Slide17- I think we need to correct the y-axis (although Delta phi
correction is negligible but still we need what is that contribution
is). In this paper, all other results are corrected for detector effect
and presented with sys. uncertainty expect this Delta_phi result. It
sounds sloppy.

Same for Slide-19 Aj results.


Cheers
Nihar



On 2023-01-19 20:19, David Stewart via Star-hp-l wrote:
> Hi all,
> Please find attached ours slides for tomorrow's (now this morning --
> sorry, message didn't send!) meeting,
> Best regards,
> Dave
>
> On Wed, Jan 18, 2023 at 11:42 AM Roy Chowdhury Priyanka (DOKT) via
> Star-hp-l <star-hp-l AT lists.bnl.gov> wrote:
>
>> Hello all,
>>
>> I would like to present an update on D0-hadron femtoscopic
>> correlation function analysis at Au+Au@200 GeV.
>>
>> Regards,
>> Priyanka
>>
>> -------------------------
>>
>> From: Star-hp-l <star-hp-l-bounces AT lists.bnl.gov> on behalf of
>> Barbara Trzeciak via Star-hp-l <star-hp-l AT lists.bnl.gov>
>> Sent: Tuesday, January 17, 2023 10:58 AM
>> To: STAR HardProbes PWG <Star-hp-l AT lists.bnl.gov>
>> Subject: [Star-hp-l] HP-pwg meeting Thursday (19th Jan) 10 AM, BNL
>> time
>>
>> Dear All,
>>
>> We will have our HP-pwg meeting this Thursday (19th Jan) at 10 AM
>> EDT.
>> Please let us know if you want to present and discuss your analysis.
>>
>> HP working group weekly meeting info:
>>
> https://drupal.star.bnl.gov/STAR/pwg/Hard-Probes/Weekly-HP-PWG-meeting
>>
>> Join ZoomGov Meeting
>>
> https://bnl.zoomgov.com/j/1611419615?pwd=VW1hNm43ZDd5d2EvK2R4aEJsQ2ZNZz09
>> [1]
>>
>> Meeting ID: 161 141 9615
>> Passcode: 744968
>>
>> Best regards,
>> Barbara, Nihar, Yi
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>
> --
>
> David Stewart
> Postdoctoral Fellow | Department of Physics, Wayne State University
>
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David Stewart

Postdoctoral Fellow | Department of Physics, Wayne State University