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Re: Minutes from GlueX Software Meeting
Hi All
Regarding a gold-platted reaction study, yesterday we discussed
diffractive omega production with rho-Delta final states as
background (they both yield a pi+pi-pi0proton final state). I
incorrectly assumed that the ratio of 9 for diffractive rho to
omega production would also hold for rho-Delta to omega-p.
It does not. Please see the attached note which has cross sections
and results of a study of the overlap (there seems to be very
little) between gamma p to omega p and gamma p to rho Delta - in
terms of the latter providing a background under the omega in
the former. We may want to think of another candidate reaction
to understand effects of resolution.
Cheers
Alex
At 4:05 PM -0500 2/6/07, David Lawrence wrote:
>Hi Folks,
>
> The minutes from todays software meeting are available on the Wiki at:
>
>http://www.jlab.org/Hall-D/software/wiki/index.php/February_6%2C_2007_Software
>
>and copied below.
>
>Regards,
>-David
>
>==Agenda==
>
># Review minutes from [[January 30, 2007 Software]] meeting
># [[FCAL status]] (Mihajlo)
># Action items
># Golden Channels (Alex)
># Rates in CDC layers added inside ring 1 (Richard)
># Update on the background normalization factor (Richard)
># Results on tagger background from electron beam halo (Richard)
>
>==Minutes==
>
>Attendees: David L., Elke A., Simon T., Elliott W., Elton S., Mark
>I., Eugene C.
>On the phone: Mijhalo K., Richard J., Alex D.
>
>===FCAL status===
>Mihjalo reported on some recent work regarding the FCAL
>reconstruction. The work focussed on the rate of multi-cluster
>backgrounds generated from single photon events. These tend to be
>generated from "pe-shower"-ing off of another part of the detector
>upstream. It appears to come primarily from the FDC cables which
>result in a large increase of multi-cluster events at around 9-11
>degrees.
>
>A linearity correction has been applied to remove most of the
>descrepancy between the reconstructed and thrown cluster energies.
>This descrepancy can be seen in the plots shown at the [[December
>11, 2006 Software]] meeting. With the energy correction, the
>distribution appears to have a floor term of almost 5%. Alex pointed
>out that Rad-φ had a floor term closer to 3.2%. Richard
>suggested another non-linearity correcting iterator algorithm may
>not be enabled in the current reconstruction. Mihjalo will look into
>it.
>
>For next time, Mihjalo was going to look into doing the following:
>*Throw photons distributed evenly over solid angle rather than just angle.
>*Look at the splash profiles of the multi-cluster events. In particular:
>**How close are the clusters (can we merge them?).
>**How is the energy distributed between the clusters.
>
>===Action items===
>''<deferred until next week>''
>
>===Golden Channels===
>Alex gave a brief report on a discussion he'd had with Elton
>regarding the "golden channels" we should look at with the
>simulation. The
><math>\gamma p\rightarrow b_{1}\pi \rightarrow \omega\pi \rightarrow
>\pi\pi\pi</math> channel looks to be a good choice since
>it is a close match to the expected decay path for hybrids.
>
>For the purposes of the upcoming reviews, they thought of combining
>data from the following 2 channels:
>*<math>\gamma p\rightarrow \omega p \rightarrow p\pi\pi\pi</math>
>*<math>\gamma p\rightarrow \Delta\rho \rightarrow (p\pi)(\pi\pi)</math>
>
>The cross-section for the <math>\omega</math> channel is known to be
>9 times smaller than for the <math>\rho</math>. By combining data,
>we can show that the detector resolution is good enough to
>distinguish the <math>\omega</math> from the <math>\rho</math> and
>it will
>use both charged and neutral particles.
>
>===Rates in CDC layers added inside ring 1===
>Richard gave a report on a brief backgound rate study he did where 4
>additional CDC layers were put into the HDGeant geometry.
>The rates are shown in the picture below. The yellow area represents
>the new layers while the white are the layers from the nominal
>design.
>Note that in this simulation, the start counter was removed since it
>overlapped in space with the new layers. The rates in the nominal
>design look to have increased slightly due to the larger amount of
>material in the new layers as compared to the start counter.
>
>[[Image:2007_02_06_cdcrates.gif]]
>
>
>===Update on the background normalization factor===
>Richard reported that he found a bug in the simulation of the
>electron beam source in the upstream simulation program (not
>hdgeant). This program is used to find the factor by which the rates
>obtained using the built-in coherent bremstrahlung generator in
>hdgeant must be scaled in order to get the true rates. This factor
>is nominaly 1.1 for 10^7 running (see
>src/programs/Simulation/HDGeant/control.in). After the bug fix, the
>simulation was rerun to see if it affected the rates in GlueX
>recently obtained from Monte Carlo. The rates were not affected by
>the change.
>
>===Results on tagger background from electron beam halo===
>Richard reported that he is currently writing a note detailing the
>results of a study he has done on the beam halo. In this study,
>Richard has created a model of the beam halo using data generated by
>ray tracing by the CASA group. With the model, he was able to
>estimate the rates in the tagger (both microscope and whole
>hodoscope) due to the beam halo. These indicate the halo-induced
>rates are below the 1% level. It was noted however, that the CASA
>simulation stops tracking particles once they get a certain distance
>fromthe beamline. It may be that particles generated from scattering
>off the beamline will somehow contaminate the beam in the form of
>addition halo which may force the background tagger rates to exceed
>1% of the primary rate.
>
>==Action Items==
>#Freezing tags in subversion through hooks (David)
>#Put tarballs of external packages on Wiki(David)
>#SVN web interface for browsing change logs (David)
>#Design and implement exception and logging scheme for JANA
>#Discuss integration issues
>#Experiment with shared pointers
>
>--
>
>------------------------------------------------------------------------
> David Lawrence Ph.D.
> Staff Scientist Office: (757)269-5567 [[[ [ [ [
> Jefferson Lab Pager: (757)584-5567 [ [ [ [ [ [
> http://www.jlab.org/~davidl davidl@jlab.org [[[ [[ [[ [[[
>------------------------------------------------------------------------
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Alex R. Dzierba
Chancellor's Professor of Physics (Emeritus)
Department of Physics / Indiana U / Bloomington IN 47405 / 812-855-9421
JLab Visiting Fellow
Jefferson Lab / 12000 Jefferson Ave / Newport News, VA 23606 / 757-269-7577
Home Phone: 812-825-4063 Cell: 812-327-1881 Fax: 866-541-1263
http://dustbunny.physics.indiana.edu/~dzierba/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
gxdoc_ard4.pdf