Chi,
as long as the cutoff energy (10MeV) is much smaller than the resolution
(30MeV) the resulting Mascarad-W is very well approximating the real one.
Therefore, if we see a shift in the Mascarad centroid, that's expected!!
Imagine the Blast resolution was 1 MeV, then one would have to choose a
cutoff energy of significantly less than 1 MeV and hence the centroid
would be shifted significantly less. This is exactly what we had discussed
several times, remember BillT reporting at the January collaboration
meeting:
"The higher the resolution with which we looked at the scattered electron
energy, the less of a shift we actually saw ... however the centroid
does appear shifted because the radiation tail is convoluted with the
resolution ... and the amount of shift is resolution-dependent"
>> -What we really need is pml,r(before RAD+ELOSS) - pwl,r(after RAD+ELOSS)
>
> This is impossible. the best you can do is:
> pwl,r(before RAD+ELOSS) - pwl,r(after RAD+ELOSS)
> after binning and averaging pwl,r
Can we use the "delta peak" for pml,r(before RAD+ELOSS)?
Is pml,r with MASCARAD just the tail, or is it an admixture of the "delta
peak" and the Mascarad-tail?
Regards,
Michael
On Thu, 23 Mar 2006, Chi Zhang wrote:
>
>
>> -I'm still doubtful about the electron spectrum with and without Mascarad.
>> In Adrian's plot "Wcorr.gif" from 2006/03/01 (see meeting minutes) the
>> radiated elastic peak maximum differs from the unradiated one by ~10-15
>> MeV. I don't see such a difference in your comparison of MASCARAD on/off.
>> I have a suspicion why. MASCARAD is used in the generator. Is it
>> perhaps that pml,r is the generated momentum *after* the event has been
>> radiated? (Experts may want to comment!!) Then, of course, both pml,r
>> and pwl,r are shifted by the same amount, and the differences pml,r-pwl,r
>> must look the same for both MASCARAD on and off.
>
> This is the case. when comparing pml-pwl, there is no point to do
> with/without MASCARAD. The non gaussian shape is a result of the "impact
> angle" dependent resolution that is simulated in the blastmc. The resolution
> is worse at very forward angle as you can see form the tossed1.ps. The
> wiggling, if I remember correctly, is an artifact due to the non-exact
> reversion of the cubic t2d/d2t relation used in recon/blastmc. It is not
> present when one uses the linear t2d/d2t. but the size of the wiggles is only
> 5 MeV anyway.
>
>> -What we really need is pml,r(before RAD+ELOSS) - pwl,r(after RAD+ELOSS)
>
> This is impossible. the best you can do is:
> pwl,r(before RAD+ELOSS) - pwl,r(after RAD+ELOSS)
> after binning and averaging pwl,r
>
> I would like to repeat a point I made before. I think we should be careful
> reading into Adrian's W plot. The mascarad has a minimum photon energy of
> 10MeV!!!!
>
> I repeat, minimum photon energy 10MeV!!!!
>
> This means every single event MASCARAD generates emits a photon with energy
>> =10MeV. so none of them belongs to the original delta peak. but we know the
> delta peak persists and is only reduced by about 20%. i.e. significant
> fraction of the events do not radiate. So all MASCARAD generates is some kind
> of tail. Then ofcourse the peak is shifted by about 10MeV but this is merely
> an artifact. if you do kinematic correction based on this artifact ... ...
>
> On the other hand, it is not clear to me after a few attmept to understand
> it, how to reproduce the delta part with MASCARAD. I think MASCARAD experts
> should gather and give a better view of what is being generated and what it
> means.
>
> Chi
>
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