sPHENIX Event Plane Detector discussion

[Ejiro Umaka <ejironaomiumaka AT gmail.com>]

Hi Rosi,

That's a good point- the GEANT description of our detectors has changed quite a bit from 2 years ago.

BTW, I'm not attributing the reason for the difference to be due to pileup- I just tried to recollect what changed in those events versus the current sims.

I'll take a look at what the ring by ring psi_2 looks like, thanks for the idea!

Regards,

Ejiro

On Thu, Apr 27, 2023 at 11:58 AM Rosi Reed <rosijreed AT lehigh.edu> wrote:

Hi All,

The main source of an asymmetry is material in front of the EPD.  What I don't know (as Jamie mentioned in our earlier meeting) is how well the material in the simulation matches reality.  But cables, frames, etc, aren't all azimuthally symmetric.  I agree with Chris that it shouldn't have anything to do with pile-up - though in reality we will have to worry about downstream collision remnants going through the detector, etc. 

What does the psi_2 look like when you calculate it ring by ring and South vs North?

Cheers,

Rosi

On Thu, Apr 27, 2023 at 11:46 AM pinkenburg <pinkenburg AT bnl.gov> wrote:

P.S. one other difference is that (likely) you use the tiles and not the
G4Hits anymore. Do you have systematic offsets between the G4Hits
location and the tile location? Does the mean G4Hit phi/radius in each
tile (integrated over many events) match what the tile geometry says?

On 4/27/2023 11:27 AM, pinkenburg wrote:
> Hi Ejiro,
>
> I sincerely doubt that this is pileup. The epd integrates over a
> single bunch crossing and for a single bunch crossing the pileup is
> somewhere in the sub percent range. Basically the events you get from
> the sims for the epd are single events without pileup. Also you can
> remove pileup events from your analysis if you want to make sure
>
> Chris
>
>
>
> On 4/27/2023 11:14 AM, Ejiro Umaka wrote:
>> Hi all,
>>
>> I've been working on the event plane determination for the EPD (and
>> other subsystems). Initially (~ 2 years ago) when we first looked at
>> the EPD raw psi_2, we got a flat distribution, but the most recent
>> simulation results were not. The only thing I can think of as to what
>> changed between then and now is pile-up in the current simulations.
>> I proceeded to look at the phi -weighted psi_2 distributions and they
>> are flat (attached)!
>>
>> I'd like to discuss this further at the EPD/bulk meeting next week.
>>
>> Best regards,
>> Ejiro
>

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Christopher H. Pinkenburg       ;    pinkenburg AT bnl.gov
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Rosi Reed
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Lehigh University
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