Alternative methods of monitoring relative spin dependent luminosities for W AL analysis.

Alternative low Pt QCD events recorded in the W-stream were spin sorted. The rato of the yields for those alternatives differ by less than 0.5% from the one obtained using the default rel lumi monitor events used in W AL.

Since the magnitude of W AL is of 0.1, the stability of lumi monitor of 0.005 is sufficient to be neglacted in the error propagation.

/* mapping of spin4-index to helicity at STAR  */   

       ka=10,  /* STAR pol B+ Y +  */

       kb=9,   /* STAR pol B+ Y -  */

       kc=6,   /* STAR pol B- Y +  */

       kd=5,   /* STAR pol B- Y -  */

 

Fig.1 Top row: left - defaul rel lumi monitor: events with flipped isolation cut and ET<20 GeV.

Middle - event count stored in the ttree. Right  - for events with reco prim vertex and at least 1 TPC track w/ pT >10 GeV/c I pick the highest  2x2 ET matched to such 10+ GeV/c track.

Bottom row - 3 subset of events: Left - all with a 10+ GeVc track, middle - additionally 2x2ET=[5,10] GeV, right - as before but 2x2 ET=[10,14] GeV.

Plots show ratio of yileds to the top left plot (the default) - deviatins from a constant are on the level of 0.5%.