STAR QA Board

[videbaek <videbaek@bnl.gov>]

Dear Ashish,

I am not an exert on this but it looks to me that the vertex 
ordering/assignment is not corect
(not selected correctly).I would suspect that in pp 500 it is not easy 
to get the right vertex even with the fast detectors.
I think we need some input from experts on this.

best Flemming


On 2022-02-18 17:39, Ashish Pandav wrote:
> 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
> > > _______________________________________________
> > > STAR-QAboard-l mailing list
> > > STAR-QAboard-l@lists.bnl.gov
> > > https://lists.bnl.gov/mailman/listinfo/star-qaboard-l
> >
> > --
> > Flemming Videbaek
> > senior scientist
> > videbaek @ bnl.gov [1]
> > Brookhaven National Lab
> > Physics Department
> > Bldg 510D
> > Upton, NY 11973
> >
> > phone: 631-344-4106
> > cell     :  631-681-1596
>
>
> Links:
> ------
> [1] http://bnl.gov

--
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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