STAR task force for tuning PYTHIA

[Raghav Kunnawalkam Elayavalli <kunnawalkamraghav AT gmail.com>]

Hi Yuanjing,

Thanks for your comments. Please find my follow up questions below - 

Cheers

Raghav 

**************************************

Raghav Kunnawalkam Elayavalli

email: raghav.ke AT yale.edu 

Associate Research Scientist  

Yale University and 

Brookhaven National Lab

<he/him/his>

**************************************

On Feb 23, 2021, at 7:51 PM, Yuanjing Ji <jiyj AT rcf.rhic.bnl.gov> wrote:

Hi Raghav,

1) why do you have a BBC trigger in your code? We use that as a
minbias trigger yes? and when you generate pythia, it is by definition
having some activity in the event.  do you have cases where your BBC
trigger fails?

I do observe there are some events that cannot be triggered. There are about ~90% MC events could be triggered in SoftQCD:nonDiffraction (regarded as minbias events) or HardQCD:all events. And nearly half of the events won't pass the trigger if we set a high mPtHat cut such as 50<mPtHat<100 GeV. When I do the normalization, only the events that are triggered by BBC will be counted. I have checked that the spectra and particle ratios are consistent with or without BBC trigger.

In this case, i think that we should remove the trigger given that we presented corrected data. 

2) when you fill the pT histograms, why do you fill with the inverse
pT weight?

This weight is due to we are calculating pT spectra which is d^2N/(2pi*pT*dpT*dy).

Ah yeah that makes sense. sorry i didnt check the y axis in a bit more detail :) 

Regarding the systematic shift in the comparison, I think probably it is due to the Pythia sample I generated are from HardQCD:all. The cross-section for HardQCD:all (66.7ub) is higher than SoftQCD:nonDiffraction (29.6ub). I now add a scale factor to scale back to STAR pp cross-sections (30ub in the paper) as the experiment observable is d^2N/(2pi*pT*dpT*dy). While I don't expect HardQCD:all events can describe low pT identified particle spectra, but there is still a shift at high pT:

https://drupal.star.bnl.gov/STAR/system/files/pythiatune0223.pdf

Hmm that is interesting… given that we are using pythia8 we might be ok in using a using a scale factor but I need to think about it a bit. How different are the plots? do you have better agreement now? 

Best,
Yuanjing

On 2021-02-18 12:36, Raghav Kunnawalkam Elayavalli wrote:

Hi Yuanjing,
Thanks for your slides and sorry i wasnt able to attend the meeting
yesterday. I have a couple of questions in your analysis - looking at
your plots, while i would not expect pythia to exactly reproduce the
data, it looks like there is a systematic shift in the comparison...
1) why do you have a BBC trigger in your code? We use that as a
minbias trigger yes? and when you generate pythia, it is by definition
having some activity in the event.  do you have cases where your BBC
trigger fails?
2) when you fill the pT histograms, why do you fill with the inverse
pT weight?
Cheers
Raghav
**************************************
Raghav Kunnawalkam Elayavalli
email: raghav.ke AT yale.edu
Associate Research Scientist
Yale University and
Brookhaven National Lab
<he/him/his>
**************************************

On Feb 17, 2021, at 3:16 PM, Yuanjing Ji via Star-tf-tunepy-l
<star-tf-tunepy-l AT lists.bnl.gov> wrote:
Hi all,
Please find my today's slides in the following link:
https://drupal.star.bnl.gov/STAR/system/files/pythiatune0217.pdf
Thanks
Yuanjing
On 2021-02-16 10:52, Matthew Kelsey via Star-tf-tunepy-l wrote:

Hi all,
Let’s have our regular pythia 8 tuning task force meeting
tomorrow
(2/17) at 3 PM BNL time. I have copied the connection details
below.
Cheers,
Matt
——————————
Matthew Kelsey
Postdoctoral Fellow
Wayne State University
<he/him/his>
Topic: STAR PYTHIA 8 Tune Task Force
Time: Feb 17, 2021 03:00 PM Eastern Time (US and Canada)
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