Hi Chi,
indeed for my arguments I assumed that the MC I talked about would use the
realistic version of admixed epel+mascarad.
It does not make any sense at all to use only the generated tail.
Therefore, if MASCARAD is to be used for any future results, the admixing
issue has to be resolved.
In regard of determining "residual kinematic corrections" for v3_4_17 in
preparation of the collaboration meeting, I then suggest the following:
Eugene, Adrian:
-keep MASCARAD off
-compare pml,r-pwl,r with ELOSS=on to determine momentum loss for protons
and electrons (only significant for protons).
-correct measured data for momentum losses (relevant only for protons)
-determine residual dp's and dth's by imposing elastic kinematics.
In case of electrons, this will "effectively" account for the shift
(from rad+resol) and for the real "residual" kinematic correction in
delta_p.
-for all subsequent data analyses, use momentum loss correction + residual
corrections from above to correct reconstructed data.
Regards,
Michael
On Sat, 25 Mar 2006, Chi Zhang wrote:
>
> Hi Michael
>
> I can not agree with your reasoning.
>
> The reasoning is only valid if we generate the delta peak and the tail. The
> MASCARAD channel in DGen only produces the tail. There is a channel that
> mixes epel and MASCARAD but there is a problem of what fraction of events are
> generated in either channel. I do not think we have resolved the problem of
> how to make the admixture of pure elastic and radiate elastic yet.
>
> The bottom line is: without the resolutions, i.e. with the original pml/r
> variables, there shall NOT have any shift. This is NOT the case if one
> generates with MASCARAD channel alone in DGen. This will be the case if the
> mixed channel of epel and mascarad is used but I do not know how to interpret
> the results, both in terms of the cross section and asymmetries.
>
> we are comparing two cases:
> no shift originally + resolution = shift (Bill T's case)
> significant shift originally + resolution = more shift
> I am not convinced that we did not put ourself in the second case.
>
> Since we are trying to derive the kinematic corrections, which themselves are
> at the order of couple tens of MeV, a 10MeV shift in the ORIGINALLY TOSSED
> events is significant.
>
> Chi
>
> On Thu, 23 Mar 2006, Michael Kohl wrote:
>
>> 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
>>>
>>
>>
>> +-------------------------------------+--------------------------+
>> | Office: | Home: |
>> |-------------------------------------|--------------------------|
>> | Dr. Michael Kohl | Michael Kohl |
>> | Laboratory for Nuclear Science | 5 Ibbetson Street |
>> | MIT-Bates Linear Accelerator Center | Somerville, MA 02143 |
>> | Middleton, MA 01949 | U.S.A. |
>> | U.S.A. | |
>> | - - - - - - - - - - - - | - - - - - - - - -|
>> | Email: kohlm@mit.edu | K.Michael.Kohl@gmx.de |
>> | Work: +1-617-253-9207 | Home: +1-617-629-3147 |
>> | Fax: +1-617-253-9599 | Mobile: +1-978-580-4190 |
>> | http://blast.lns.mit.edu | |
>> +-------------------------------------+--------------------------+
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
+-------------------------------------+--------------------------+
| Office: | Home: |
|-------------------------------------|--------------------------|
| Dr. Michael Kohl | Michael Kohl |
| Laboratory for Nuclear Science | 5 Ibbetson Street |
| MIT-Bates Linear Accelerator Center | Somerville, MA 02143 |
| Middleton, MA 01949 | U.S.A. |
| U.S.A. | |
| - - - - - - - - - - - - | - - - - - - - - -|
| Email: kohlm@mit.edu | K.Michael.Kohl@gmx.de |
| Work: +1-617-253-9207 | Home: +1-617-629-3147 |
| Fax: +1-617-253-9599 | Mobile: +1-978-580-4190 |
| http://blast.lns.mit.edu | |
+-------------------------------------+--------------------------+
This archive was generated by hypermail 2.1.2 : Mon Feb 24 2014 - 14:07:33 EST