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<p>Hi Michael,</p>
<p> 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.<br>
</p>
<p> 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.</p>
<p>If you use FT_particles it should probably look more like</p>
<p>TLorentzVector eBeam(0.0,0.0,6.423,6.423);</p>
<p>TLorentzVector FTe(ftCx*ftEnergy, ftCy*ftEnergy, ftCz*ftEnergy,
ftEnergy);</p>
<p>TLorentzVector gamma=eBeam-FTe;</p>
<p><br>
</p>
<p>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.</p>
<p>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).<br>
</p>
<p><br>
</p>
<p>Cheers</p>
<p>Derek<br>
</p>
<br>
<div class="moz-cite-prefix">On 02/05/18 21:53, Michael Dugger
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:Pine.LNX.4.64.1805021649480.9647@jlabl1.jlab.org">
<br>
Derek,
<br>
<br>
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:
<br>
<br>
TLorentzVector beam(0.0,0.0,6.423-ftEnergy,6.423-ftEnergy);
<br>
<br>
with ftEnergy taken from
<br>
<br>
FT_particles_energy
<br>
<br>
Does that look wrong?
<br>
<br>
Any help is appreciated.
<br>
<br>
Take care,
<br>
Michael
<br>
<br>
On Wed, 2 May 2018, Derek Glazier wrote:
<br>
<br>
<blockquote type="cite">Hi Mike,
<br>
<br>
<br>
<blockquote type="cite">** There are a lot more events at large
angle and low momentum. I assume
<br>
these events are coming from CTOF, but have not checked that
assumption.
<br>
</blockquote>
This is possibly the new CVT tracking algorithm which seems to
be much more efficient, while also introducing some extra
background.
<br>
<blockquote type="cite">The Bad and the Ugly->
<br>
<br>
* I tried to do a missing mass for the reaction gamma p ->
p X. Get huge
<br>
bump at massX squared = - 0.1 . Can't figure out what is going
on there.
<br>
</blockquote>
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.
<br>
<blockquote type="cite">
<br>
* The invariant mass of the proton pi^- system is just a blob
at masses
<br>
that look somewhat high. Just a mess really.
<br>
<br>
If anyone can get any good looking physics (some sort of
invariant mass
<br>
peak at about the right location), please let me know. My
stuff is just
<br>
kind of awful :(
<br>
</blockquote>
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.
<br>
Cheers
<br>
Derek
<br>
<blockquote type="cite">
<br>
Take care,
<br>
Michael
<br>
<br>
<blockquote type="cite">We shall have meeting tomorrow,
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