STAR QA Board

["Ke, Hongwei" <kehw@bnl.gov>]

Hi Ashish,

Thank you very much for checking that.

These results are surprising to me, especially the hlt_vpd100_mon.

It has a vpd timing cut for |Vz| < 100, which is not visible in the hlt_vpd100_mon plot.

Do we need any special vertex selection for pp data?

Best regards,

Hongwei Ke

On Feb 19, 2022, at 2:46 AM, Ashish Pandav <ashish.pandav@niser.ac.in> wrote:

Dear Hongwei and all,

I did a quick check over a few st_physics picodst files.

Please find the Vz distributions from the two triggers: hlt_vpd100_mon and hlt_dimuon_mon attached below.

Both the triggers show such structure in Vz.

Best,

Ashish

On Sat, Feb 19, 2022 at 5:23 AM Ke, Hongwei via STAR-QAboard-l <star-qaboard-l@lists.bnl.gov> wrote:

Hi Ashish and Gene,

L4 has only two triggers

hlt_vpd100_mon

hlt_dimuon_mon (if in the run)

They are based on VPDTAC-100 and dimuon trigger, respectively.

Can we check these two triggers?

Best regards,

Hongwei Ke

On Feb 18, 2022, at 5:56 PM, Van Buren, Gene via STAR-QAboard-l <star-qaboard-l@lists.bnl.gov> wrote:

Hi,

Offline QA also sees this divided z vertex distribution without any selection criteria on the vertex (these are all vertices stored in StEvent).

-Gene

On Feb 18, 2022, at 5:51 PM, videbaek via STAR-QAboard-l <star-qaboard-l@lists.bnl.gov> wrote:

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
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--
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
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<Vz_dists.pdf>