STAR QA Board

[Ashish Pandav <ashish.pandav@niser.ac.in>]

Dear Flemming,

The Vz distribution is filled before any cuts are applied. The Vz ranges from -200 to +200 cm, as shown in the attached plot.

I simply read the z component of the primary vertex from the picodsts, ( TVector3 vertexPos(picoEvent->primaryVertex()); Vz = vertexPos.Z();).

Just as an example, the file from the below link clearly shows such two peaks in the Vz. 

/star/data12/reco/production_pp500_2022/ReversedFullField/dev/2022/047/23047022/st_fwd_23047022_raw_6000001.picoDst.root

I also had a look at the L4 vz distributions and as you pointed out they look as usual. Not sure, what could be the reason for the difference between L4 and picodsts.

Thanks,

Ashish

On Sat, Feb 19, 2022 at 2:56 AM videbaek <videbaek@bnl.gov> wrote:

Hi Ahsish

can you remind us what your selection criteria is for that vz
distribution. I ask since the HLT (L4) vz dist looks as expected.

-F

On 2022-02-18 15:25, Ashish Pandav via STAR-QAboard-l wrote:
> Dear Ting and all,
>
> Regarding this point,
>
>> From BulkCorr & HF:
>> 1. Continue to see strange multi-peak Vz distributions; do not
>> know what the problem is. We start to see this since last week from
>> st_physics branch.
>
> For the presented QA slides, both  st_physics and st_fwd files were
> combined and analysed, not only the st_physics. But I had a quick
> check at the st_physics and st_fwd picodst files individually, and
> both of them show two peaks for the Vz distributions. For st_fwd
> picodst files, this shape is more pronounced compared to st_physics.
>
> Best,
> Ashish
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--
Flemming Videbaek
senior scientist
videbaek @ bnl.gov
Brookhaven National Lab
Physics Department
Bldg 510D
Upton, NY 11973

phone: 631-344-4106
cell     :  631-681-1596

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