[Clas12_verystrange] Very Strange Meeting May 2nd

[dugger at jlab.org]

Derek,

Thanks for the info. I will put in the full expression for the photon
energy as you do.

I already reset the particle energy to PDG.

Can you be a bit more specific about your using

"FT particle from the REC::Particle bank"

I'm using energy from the FT bank and think this is where I might be going
wrong.

Take care,
Michael

> Hi Michael,
>
>  Â Â  That looks approximately right. You could make a lorentz vector for
> the electron in the FT then subtract this from the electron beam lorentz
> vector. This way you also get linear polarisation plane, Q2 etc I am not
> sure if it makes a big difference on the missing mass or not, but is
> what I do.
>
>  Â  I just use the FT particle from the REC::Particle bank. You should be
> aware that the FT particles are already part of this array in case you
> use them twice.
>
> If you use FT_particles it should probably look more like
>
> TLorentzVector eBeam(0.0,0.0,6.423,6.423);
>
> TLorentzVector FTe(ftCx*ftEnergy, ftCy*ftEnergy, ftCz*ftEnergy, ftEnergy);
>
> TLorentzVector gamma=eBeam-FTe;
>
>
> If you use REC::Particle, you also need to loop over REC::ForwardTagger
> and match the pindex to the REC::Particle array index to identify the FT
> entries.
>
> Do you set the mass of the proton to the PDG mass or just use the energy
> and momentum from REC::Particle ? I guess this could give an offset of
> 0.1 in MM^2 (if you do the latter).
>
>
> Cheers
>
> Derek
>
>
> On 02/05/18 21:53, Michael Dugger wrote:
>>
>> Derek,
>>
>> Your stuff looks better than mine. I am using 6.423 GeV for the
>> electron beam energy and then subtract off the tagger energy like:
>>
>> TLorentzVector beam(0.0,0.0,6.423-ftEnergy,6.423-ftEnergy);
>>
>> with ftEnergy taken from
>>
>> FT_particles_energy
>>
>> Does that look wrong?
>>
>> Any help is appreciated.
>>
>> Take care,
>> Michael
>>
>> On Wed, 2 May 2018, Derek Glazier wrote:
>>
>>> Hi Mike,
>>>
>>>
>>>> ** There are a lot more events at large angle and low momentum. I
>>>> assume
>>>> these events are coming from CTOF, but have not checked that
>>>> assumption.
>>> This is possibly the new CVT tracking algorithm which seems to be
>>> much more efficient, while also introducing some extra background.
>>>> The Bad and the Ugly->
>>>>
>>>> * I tried to do a missing mass for the reaction gamma p -> p X. Get
>>>> huge
>>>> bump at massX squared = - 0.1 . Can't figure out what is going on
>>>> there.
>>> For FT e- and run 3050 I would expect a large elastic peak at
>>> massX=0, this is what I get. Could some calibration be off? For run
>>> 3050 I use 6.4GeV beam energy.
>>>>
>>>> * The invariant mass of the proton pi^- system is just a blob at
>>>> masses
>>>> that look somewhat high. Just a mess really.
>>>>
>>>> If anyone can get any good looking physics (some sort of invariant
>>>> mass
>>>> peak at about the right location), please let me know. My stuff is
>>>> just
>>>> kind of awful :(
>>> I attach a slide for eppi+pi- final state. I seem to get missing mass
>>> peaks at the right place and the 2pi invariant mass looks like a rho.
>>> The last few updates have certainly improved the cooked data quality.
>>> Although I do not see any Deltas for some reason.
>>> Cheers
>>> Derek
>>>>
>>>> Take care,
>>>> Michael
>>>>
>>>>> We shall have meeting tomorrow, Wednesday May 2nd at 11:15 JLab time.
>>>>> Those at JLab meet in L210a
>>>>>
>>>>>
>>>>> Meeting Title: Very Strange Meeting
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