STAR Flow, Chirality and Vorticity PWG

[James Dunlop <dunlop AT bnl.gov>]

Thanks, Gene,
  As Haojie's plots show on a finer time scale, each fill has drifts up to 
~30 um in vx but actually
quite a bit larger in vy.  I don't know which direction thee machine used to 
tune the collision
rate, could be either.

In any case, your second point brings up a real potential for difference 
between
Ru and Zr that should be investigated.  We did try to get the TPC occupancy
to be the same between Ru and Zr, by tuning the ZDC coincidence rate
to be equal,  but i don't actually know the level to which that was 
successful.
Since the overall reconstruction efficiency depends on TPC occupancy, there 
could
be a systematic difference there.  How different is the occupancy
between Ru and Zr?
--J


> On Apr 26, 2022, at 11:54 PM, Van Buren, Gene <gene AT bnl.gov> wrote:
> 
> Hi, Jamie and all,
> 
> On this particular point....
> 
>> On Apr 26, 2022, at 7:53 PM, James Dunlop via Star-fcv-l 
>> <star-fcv-l AT lists.bnl.gov> wrote:
>> 
>> The beam shifts by ~40 um all the time.  It's beam steering at that level,
>> often used to level our luminosity.
> 
> I offer the following not as a contradiction, but as complementary 
> information on the beam positions (and I'm certainly not making any kind of 
> statement on noticeable impacts from beam positions on track reconstruction 
> efficiency)...
> 
> The mean <Vx> at z=0 for each fill (which I labeled as "x0") is shown in 
> the below plot obtained from only a small fraction of the event statistics. 
> The colors show the two beam species. I would conclude that whatever beam 
> steering they were doing, they managed to get x0 consistent within a given 
> species to within +/-15 microns fill-to-fill. If it weren't for that 
> consistency, we wouldn't see the apparent offset between the two species.
> 
> But on the core topic of this thread of tracking efficiency differences 
> between the two species, I do not have the confidence to say that 
> SpaceCharge & GridLeak distortion corrections are consistent between the 
> two species at the level necessary to avoid systematic track reconstruction 
> efficiency differences at the 0.1% level. That level of confidence would be 
> difficult to achieve, in my opinion.
> 
> -Gene
> 
> <PastedGraphic-1.png>

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