sPHENIX discussion of physics

[Xin Dong <xdong AT lbl.gov>]

Hi Cameron,

Thank you for the nice simulation study. It is excellent to see the full GEANT+tracking study which is expected to show more realistic performance. I have a few comments/questions to your write-up. I apologize for my overlook in case that some of these have been discussed before, but would also appreciate your clarifications.

1) Page 1, in Eq. 1, you have the term epsilon_acc^2, while epsilon_acc seems to be the single track geometry acceptance. However, for D0->K-pi decays, the two daughter track momentum directions are correlated, particularly in rapidity direction, they are probably large correlations. So the geometric acceptance better calculated for the D0->K-pi+ decay as a whole instead of applying the single track acceptance.

2) Page 3, line 74-75 regarding the out-of-time pileup hits. Do you have the numbers on what is the fraction of the pileup contribution compared to hits from signal events in saying MB events? In the out-of-time pileup, have you included the UPC electron contributions? In the STAR PXL detector case, the UPC electrons are much more than the hadronic pileup hits. With MVTX, the integration time window is much shorter, but I would still expect the relative contribution between UPC electrons and hadronic pileup should stay similar.

3) Before moving to the D0 simulation, I am very interested to see the single track performance figures from the full simulation, e.g. track DCA pointing resolution, tracking efficiency and ghost rate vs. pT and maybe the full DCA distributions etc. These performances are quite essential and also our KPP deliverables. They, I think, pretty much define the secondary vertex performance as well.

4) Page 6-7, the TMVA optimization for cut tuning. This is a nice study. I am wondering why you also include D0 pT as a tuning parameter. Usually physics observables are analyzed in term pT bins, so I would think one will just do the tuning pT-bin by pT-bin.

    Talking about pT dependence, my understanding is that now the tuning is done for the whole pT region which is OK. For future, I would recommend that we can do the tuning in each pT bin as the background level changes significantly vs. pT.

6) Page 6, line 187 and 190, the signal and background sample selection mass windows:

     signal:  from Fig. 6 on Page 10, the signal is clearly much narrower than 1.7-2.0. Why not use saying 3sigma window to select signals

     background:  selected only using higher mass region 2.00-2.10, I would recommend maybe select side-bands from both left and right sides and take the average (geometric or arithmetic both can be checked) as a better proxy to estimate the background.

7) Page 10, Table 3, the D0 mass position seems to be a bit lower than the PDG value. I understand there can be some momentum distortion due to the energy loss correction etc., but the 2 MeV difference seems to be not small. And later on in Table 7, 8 the results from AuAu, the mass position seems to be 2-3 MeV higher than the PDG value instead. Do we understand these? Although I know they don't have a considerable impact in extracting the D0 signal.

These are all so far. Thank you again for carrying out the full simulation studies. I am looking forward to further developments and I hope I can also make some contributions in the future.

Best Regards

/xin 

On Fri, Jan 13, 2023 at 3:28 PM Cameron Thomas Dean <cameron.dean AT cern.ch> wrote:

Hi Dennis,

Oops, I should’ve remembered that. I’ve attached a version with line numbers.

Cheers,

Cameron

On Jan 13, 2023, at 6:10 PM, Perepelitsa, Dennis via sPHENIX-HF-jets-l <sphenix-hf-jets-l AT lists.bnl.gov> wrote:

Hi Cameron,

Thanks for sending this around. Can I ask you to re-circulate to the lists but with a line-numbered version of the draft?

That would help with giving comments.

Dennis

On Jan 13, 2023, at 4:32 PM, Cameron Thomas Dean <cameron.dean AT cern.ch> wrote:

Dear colleagues,

Following my presentation in today’s heavy flavor and quarkonia meeting, I’ve attached the analysis note I wrote on reconstructing D0’s during the commissioning period.

I will circulate this in the sPHENIX physics mailing lists for 2 weeks to collect any comments before circulating it in the general mailing list.

Cheers,
Cameron

<D0_in_AuAu_sPHENIX_C_Dean.pdf>_______________________________________________
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Dennis V. Perepelitsa
Associate Professor, Physics Department
University of Colorado Boulder
on sabbatical at Brookhaven National Laboratory

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Xin Dong
Nuclear Science Division, Lawrence Berkeley National Laboratory
MS70R0319, One Cyclotron Road
Berkeley, CA 94720, USA
Tel: +1-510-486-4121
Email: XDong AT lbl.gov
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