[Clas12_verystrange] Xi(1820)

[Michael Dugger]

Hi,

Sorry about that. I should have included all of the numbers.

For the Xi(1820) reaction, here are the detection efficiency comparisons:

K+ K+ K-
Johann: 18.73%
Mike: 19.7%

K+ K+ K- pi-
Johann: 0.3%
Mike: 0.2%

K+ K+ K- p
Johann: 4.66%
Mike: 9%


-Michael

On Fri, 13 Apr 2012, Lei Guo wrote:

>
> On Apr 13, 2012, at 11:47 AM, Michael Dugger wrote:
>
>> 
>> Hi,
>> 
>> There was some concern regarding Johann's number for the detection 
>> efficiency of gamma p -> K+ K+ Xi(1820) when K+ K+ K- pi- are detected. The 
>> concern was that the reaction requires four charged particles but is much 
>> lower than gamma p -> K+ K+ K0 Omega- when K+ K+ pi+ pi- are detected. Both 
>> reactions have four charged particles detected but the Omega- reaction has 
>> a reported efficiency of about 3.85 % and the Xi(1820) reaction has a 
>> reported efficiency of about 0.3%.
>> 
>> I think I know what the problem is.
>> 
>> For the K+ K+ K0 Omega- reaction, when we see: K+ K+ pi+ pi- there are 
>> three positive charged particles and one negative. For the K+ K+ Xi-(1820) 
>> reaction, when we detect K+ K+ K- pi- there are two positive charged 
>> particles and two negative particles.
>> 
>> The negative particle detection efficiency for CLAS12 is not very good. You 
>> can see a plot of efficiencies (in percent) versus momentum for pions, 
>> kaons, and protons at
>> http://www.jlab.org/Hall-B/secure/clas12/omegaMinus/ASU/efficiencyPlots.gif
>> 
>> When I create gamma p -> K+ K+ Xi-(1820) events (phase space), where 
>> Xi-(1820) -> Lambda K- (phase space again), and have Pythia decay the 
>> Lambda, I get an efficiency of 0.2% when K+ K+ K- pi- are seen.
>
>
> What about detecting K+K+K-proton?
>
> Lei
>
>> 
>> The efficiency I get is actually lower than what Johann sees (0.3%). I 
>> think that the difference is probably due to the differences in the assumed 
>> distribution. Since Johann uses a model and I just have a simplistic phase 
>> space generation, Johann's numbers are probably more realistic.
>> 
>> Take care,
>> Michael,