STAR Flow, Chirality and Vorticity PWG

[Sergei Voloshin <voloshin AT wayne.edu>]

Hi Aihong,

Yes, definitely. This is what is shown in slide 8. "tpc" or "tpc+tof" means the cases with the effect of only efficiency without flow.

The same with "+flow" means that the effect of flow is added. Interesting that the effect of efficiency (without flow) depends rather strongly on the method used to evaluate drho, with "phistar" approach being rather insensitive. I am trying to get that affect analysically, but it is rather difficult to parameterize the efficiency in a general way (beyond phist dependence).

regards,

Sergei

On Fri, Apr 14, 2023 at 12:32 AM Tang, Aihong <aihong AT bnl.gov> wrote:

Hi, Sergei and Diyu :

Excellent thoughts. Just to add one point, I believe that the efficiency dependence on the decay topology exists even without v2. This is because the limitation of detecting fewer topologies of daughters moving in the same or opposite direction as the parent's momentum is evenly spread in two dimensions around z-axis, not three dimensions. To put it another way, it's impossible to create a hollow ball shape (none effect) by cutting a cylinder.   Additionally, surely the inclusion of v2 creates another layer of complexity.

Thanks,

Aihong

On Apr 13, 2023, at 11:14 PM, Sergei Voloshin via Star-fcv-l <star-fcv-l AT lists.bnl.gov> wrote:

Hi Diyu,

If the efficiency dependence on the decay topology (parameterized in my presentation as a function of phist-phi) is known, indeed one can use proper weights to eliminate the effect (or just calculate the corrections). How to calculate the efficiency,  is a separate question. Just the distribution in phist-phi, which you suggest to use, besides the efficiency would also depend on the signal itself (both spin alignment and flow), thow I expect this dependence to be small. My approach/hope, which I did not discuss in this presentation, would be to measure 3 quantities, let us call them "observed": drho_obs, v2_obs, a2_obs, and having the corresponding relations between them  (shown in slide 9 + a similar relation for v2_obs) extract the "real" drho, v2 and a2.

Thank you for comments/question,

regards,

Sergei

On Thu, Apr 13, 2023 at 6:16 AM dshen <dshen AT rcf.rhic.bnl.gov> wrote:

Hi Sergei,

Thanks for sharing your slides.
I have a quick comment, it seems doable to me but has to be confirmed.
In your slide 9, efficiency contributes to spin alignment in the way of 
non-zero a2, which means the efficiency is not isotropic as a function 
of \phistar - \phi. I am wondering if we use the inverse of counts in 
each \phistar - \phi bin as a weight, we are able to eliminate this 
effect, aren't we?

Thanks,
Diyu


On 2023-04-13 09:57, Sergei Voloshin via Star-fcv-l wrote:
> Hi all,
> 
> I have done some (MC) studies on the interplay of tracking efficiency,
> flow and SA and its effect on corresponding measurements.
> 
> I was not able to present this study at FCV (not yet, probably next
> time), so I put some results in the presentation (start from page 5)
> 
> 
> https://www.star.bnl.gov/protected/bulkcorr/voloshin/voloshin_SpinAlgnAcceptance.pdf
> 
> If interested, have a look. Any comments are very welcome.
> 
> Best regards,
> Sergei
> 
> --
> 
> ======================================
>  Sergei A. Voloshin
>  Professor of Physics,  Wayne State University,
>  666 W. Hancock,  Detroit,  Michigan,  48201
>  e-mail: sergei.voloshin AT wayne.edu
>  Phone: 1-313-577-1630;  Fax: 1-313-577-0711
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-- 

======================================
 Sergei A. Voloshin
 Professor of Physics,  Wayne State University, 
 666 W. Hancock,  Detroit,  Michigan,  48201 
 e-mail: sergei.voloshin AT wayne.edu
 Phone: 1-313-577-1630;  Fax: 1-313-577-0711      
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--

======================================
 Sergei A. Voloshin
 Professor of Physics,  Wayne State University,
 666 W. Hancock,  Detroit,  Michigan,  48201
 e-mail: sergei.voloshin AT wayne.edu
 Phone: 1-313-577-1630;  Fax: 1-313-577-0711     
======================================