# Quark Matter 2018

13-19 May 2018
Venice, Italy
Europe/Zurich timezone
The organisers warmly thank all participants for such a lively QM2018! See you in China in 2019!

## Practical considerations for measuring global spin alignment of vector mesons in relativistic heavy ion collisions

15 May 2018, 17:00
2h 40m
First floor and third floor (Palazzo del Casinò)

### First floor and third floor

#### Palazzo del Casinò

Poster Chirality, vorticity and polarisation effects

### Speaker

Dr Aihong Tang (Brookhaven National Lab)

### Description

The study of global polarization and spin alignment can help us probe the vorticity field generated by the initial global angular momentum and understand particle production mechanisms during hadronization. For those reasons this topic is gaining increasing interest in recent years. The study of spin alignment (quantified by $\rho_{00}$) of vector mesons involves the reconstruction of the direction of global angular momentum (L), which is the normal to the reaction plane (RP). In experiments the RP is estimated with correlations among particles and has finite resolution. In this poster, we demonstrate a procedure to correct $\rho_{00}$ for the finite RP resolution. In addition, since the 1st- and 2nd-order RP are usually not the same and they have different sensitivity to L, we derive a relationship to explain the $\rho_{00}$ obtained between the two RP. Furthermore, a deviation of $\rho_{00}$ from 1/3 can be caused by finite acceptance in pseudo rapidity (e.g., the case for STAR and ALICE). We demonstrate that this effect can be corrected elegantly in a data-driven approach. At last, because vector mesons can have an apparent spin alignment in the helicity frame (local $\rho_{00}$), this will cause an artificial azimuthal angle dependence when study the global $\rho_{00}$ as a function of emission angle with respect to the RP. We lay down a procedure to correct for this effect as well as a procedure to correct for the effect of smearing $\rho_{00}$ in azimuth bins.

Content type Experiment Presenter name already specified

### Primary authors

Dr Aihong Tang (Brookhaven National Lab) Mr Zhou Chensheng (Shanghai Institute Of Applied Physics Chines Academy Of Sciences) Mr Biao Tu (Central China Normal University)

### Presentation Materials

There are no materials yet.