[G14_run] g14 statistics for K0 Lambda

[Dr. A.M. Sandorfi]

Reinhard,

The proposal assumed a 5 cm long target with the HD density of 0.147 gm/cm^2
(section 3.1, page 54, line 4), which is what we are using in g14 (although
the Dec-Jan target ended up about 20% short.). The text mentions the larger
radius BNL cells (12.6 mm), whereas we are using cells with a radius of 7.5
mm because of the tighter JLab beam spot, but the radius does not affect the
count rates.

So the target thickness assumed in the proposal is the same, but the Mart
and Bennhold cross sections of figure 1 (page 7) are 5 times higher than you
are assuming.

Andy




On 4/6/12 5:29 PM, "Reinhard Schumacher" <schumacher at cmu.edu> wrote:

> Hello All,
> Since this morning's (4-6-12) phone meeting, I revised the estimated
> statistics for the K0 Lambda data.  What we have in-hand so far is from
> the December/January period, runs 68188 to 68770.  I improved the
> estimate for the collimation of beam and for the total tagger count rate.
> 
> See my revised slides posted on the April 6 meeting wiki page.
> 
> I can reconcile my numbers with those in the proposal:  the proposal
> assumed a considerably thicker target and used a higher guesstimated
> total cross section.  That led to an estimate of 1200 to 1800 events per
> day, whereas I think we got only about 250 events per day.
> 
> I conclude that we have only 7000 K0 Lambda events in hand, across all
> production angles and all beam energies.  This is down a factor of 4
> from my previous estimate, and there is still a factor of 2 uncertainty.
>   This number is consistent with Haiyun Lu's estimate based on a
> run-through of the partially-cooked data (See his talk on the meeting
> page).   Can anyone else double check this?  Thus, it looks to me at the
> present time like we don't have enough events to make physics analysis
> of this channel worthwhile.  Fortunately there are some fall-back
> options using other reaction channels.
> 
> The run plan for the rest of the run period should be revisited to see
> whether we have a realistic chance to get anything out of the hyperon
> production channels.
> 
> Reinhard.