Re: [Brahms-l] qm04- first drafts

Hi Zhongbao,

> For scaledown correction, it is clear that the inel trigger scaledown
> factor is vertex position and centrality dependent from a two-dimensional
> histogram. I think it is quite understandable since the inel trigger
> efficiency has weak centrality and vertex position dependence. Certainly
> if ignoring this weak dependence, the yield for central collisions will be
> lowered, but I think that not the right thing to do. I would appreciate
> if you could show your experience in how to deal with the scale down
> factor correctly or reasonablly.

As I understand it the inel trigger is equally efficient in the vertex
range were normally looking at, so I don't think we should worry about
this. It's correct that the inel trigger is less efficient for the more
peripheral events (<60% for d+Au I think), but it doesn't matter as
long as you only look at centrality ranges below 60% or MB.

For the inel trigger efficieny for p+p collisions I use 90%. In d+Au it's
91% so I think that 90% for p+p is a bit high, I would expect it to be
lower that for d+Au. Any comments on this?

In your analysis you count the number of tracks and the number of events.
If you want to correct for the scaledown you should select events only
with the event trigger and multiply with the scaledown factor (for the
event count) and select tracks in events with the track trigger and
multiply with the corresponding scale down factor. It's quite simple.

> I still doubt the acceptance map. The map generated from BRAG is very much
> different from map generated from Claus' pure geometrical method (the
> same cut on slats of tofw is applied). And the map from BRAG for B1000 is
> also very much different from that for B1050. The map generated from BRAG
> doesn't match data at all. Then I would think it the current is wrong, I
> mean much lower than 1050 actally, then the acceptance correction might
> be larger, then the yield will be lower.

Did you check if the TOFW panels and slat numbering in BRAG changed with
the new setup? My guess is that this is the problem (since this is what
have been changed from last run). You say that the B1000 and B1050 maps
are different. Did you make both of them using the current BRAG setup or
are you comparing the new B1050 with the old B1000?

> I would use constructed spectra from PHENIX pi^0 spectra for pp
> collisions+Pythia  simulation as reference spectrum for R_AA of pi at both
> mid-rapidity and forward rapidity.
>
> By the way I have re-studied the RICH efficiency via simulation for 12A427
> with a fiducial cut applied on track intersetion with RICH mid-plane. The RICH
> efficiecy for pion at pt>3GeV/c is ~97% constantly.

That sounds reasonalbe.

Thanks for the update,

Claus

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