Re: talk today on the pair spectrometer

[Richard Jones <richard.t.jones@uconn.edu>]

Sascha,

When last we spoke, you were going to make a few tweaks to the pair 
spectrometer detector geometry, and then check it in to svn.  Could you 
let me know when you have done that?  I am planning to do the 
systematics study for the endpoint energy calibration.  Once I have the 
corrected geometry I am able to run the simulations on our cluster to 
get the statistics we need.

Before you check things in, please be sure to update your local gxtwist 
installation with the latest changes from subversion.  I have put in 
numerous fixes, that I would not like to see rolled back.

Richard Jones

Could you let me know when you have checked in theHrachya.Hakobyan wrote:
> Richard,
>
> I don't know if agreement to define the endpoint energy reconstruction 
> is stiil in power.
> I remember more&less how that was done in past. It was the 
> minimisation of the difference(functional)  
> BremMC(xo)-Integral(BrTh(x0)*Gaussian(x-xo)dx, where BremMC(xo) is a  
> simulated incoherent  bremmstrahlung spectrum with all  factors 
> involved, BremTh(x) is its analytical expression for 12 GeV endpoint 
> and Gaussian is the smearing function. The parameters of the fit are: 
> the scale factor, introduced  into argument of BremTh, i.e.k*x instead 
> of x, and the sigma of Gaussian. As a first step before the fit the x 
> value is defined as a ratio of PS energy scale to approximately 
> evaluated experimental endpoint energy  Eeexp  in the same units.
>  If the PS energy scale is correct, the scale factor k obtained should 
> be equal to 1 within errors.If not it will prompt you how to  shift 
> the experimental endpoint energy for the next iteration. Rougly  
> speaking Ee=Eeexp/k. Obviously few bins before and after endpoint 
> energy  are really affected by resolution and so it is evident the 
> precision of  scale factor k should be better by factor 2-2.5  than 
> the resolution itself.
>
> Hrachya
>
>
> On Thu, 18 Sep 2008, Richard Jones wrote:
>
>> Hrachya,
>>
>> Do you have a pointer to your talk on the pair spectrometer for the 
>> collaboration meeting?  It is scheduled for today at 4:30pm.  I know 
>> this will be difficult for you because of the time difference.  If 
>> you can pass me a copy of the talk, I will get it uploaded to the 
>> portal and will assist you with the presentation in any way you wish.
>>
>> Also please let me know how you would like to connect to the 
>> meeting.  If you want us to call you, I will ask our collaborators at 
>> Jlab to make the call as they have for the last couple of meetings.
>>
>> Richard Jones
>>