STAR task force for tuning PYTHIA

[Yuanjing Ji <jiyj AT rcf.rhic.bnl.gov>]

Hi Raghav,

The new plots are put in the link slide 4-5:
https://drupal.star.bnl.gov/STAR/system/files/pythiatune0223.pdf
And the scale factor is (HardQCD:all cross-section=66.7 ub) /  (STAR pp 
cross-section = 30 ub). The assumption is we are comparing the total 
cross section E*dsigma/p = sigma_pp * d^2N/(2pi*pT*dpT*dy).

Yuanjing

On 2021-02-24 05:40, Raghav Kunnawalkam Elayavalli wrote:
> 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)
> > Join Zoom Meeting
>
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>
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