[G12] urgent help needed please
Lei Guo
lguo at jlab.org
Mon Oct 11 16:04:22 EDT 2010
Hi, JOhann,
Sorry, my previous email was meant for sth. else.
Could you explain how you got the 35% ?
Lei
On Oct 11, 2010, at 4:03 PM, Lei Guo wrote:
> Sure.
> On Oct 11, 2010, at 3:41 PM, Johann Goetz wrote:
>
>> which is why i did not use the trigger bits in my analysis.
>> However, I do believe that there is some inefficiency in the lower
>> part of the tagger due solely to the trigger configuration. I can
>> measure this to be about 35% by looking at the triggered flux plot
>> that craig shows here:
>>
>> http://clasweb.jlab.org/rungroups/g12/wiki/index.php/Image:G12_omega_gflux_tid30.png
>>
>> If I correct the flux (reduce the estimated flux below 3.6 GeV by
>> 35% I get the following comparison which I am quite happy with. The
>> shape of the g12 excitation function is extremely reliable here.
>> But there still may be an overall systematic shift and I quote a
>> systematic error of 12% here.
>>
>> <xi1320_xfncomp.png>
>>
>> On Mon, Oct 11, 2010 at 11:16 AM, Craig Bookwalter
>> <craigb at jlab.org> wrote:
>> I believe we had some kind of discussion a while back that the
>> trigger bits in TGBI are not reliable, ie sometimes events are
>> written out with no trigger bits set, or perhaps even the wrong
>> bits set...
>>
>> Lei Guo wrote:
>> Hi, Johann,
>>
>> I would think there is inefficiency for your two prong events below
>> 3.6 (or is it 3.8?) GeV. I'd love to be proven wrong though. I
>> assume you got your events from the two prong trigger, correct?
>> Then in your Xi events below 3.6 GeV, you would have to have
>> another higher energy photon (>3.6GeV) in the same time window for
>> this event to have triggered the event, otherwise, your real event
>> would not have been included in the two prong triggered events.
>> THis obviously means you overestimated your flux (or did not
>> acccount for trigger inefficiency, or whatever you want to call
>> it), therefore your current Xsection would have been lower THAN
>> what it should be. This is in line with what one observe now when
>> you compare your results with g11 and g12. There is better
>> agreement above 3.6 GeV, but your results are systematically lower
>> below that.
>>
>> I think in g11, the events below the lowest energy (1.9GeV) in the
>> trigger had to be scaled up by a big factor (~50%?) You sould check
>> Mike Williams's note on Omega.
>> Instead of looking at some benchmark channel's Xsection, which
>> would take a lot of time to figure out, and how appropriate the
>> comparison will be complicate, you best bet would probably be
>> looking at your events above 3.6 GeV, and check how often it also
>> has the 3-prong trigger bit. You can also compare that with your
>> simulation and check how often you have at least another charged
>> particle detected other than the two kaons . THIS FACTOR MIGHT ALSO
>> BE ENERGY DEPENDENT. You can then compare these two methods if
>> they are consistent.
>> On another note, when I did the g11 analysis, total Xsec extracted
>> from different ways of summing the differential cross sections has
>> typically a spread of two nb. I quoted the half of that spread as a
>> systematic error simply on the extraction of total Xsection from
>> differentiall Xsection, in addition to the model dependence. I
>> belive you would have to quote something similar along that line.
>>
>> Good luck!
>> Lei
>> On Oct 9, 2010, at 8:55 PM, Johann Goetz wrote:
>>
>> Hi Craig,
>> did you have total cross section info as a function of beam energy?
>> And if so, did you go below 3.6 GeV?
>>
>> On Fri, Oct 8, 2010 at 9:51 PM, Lei Guo <lguo at jlab.org <mailto:lguo at jlab.org
>> >> wrote:
>>
>> Hi, Johann,
>>
>> YOu intuition seems correct. However, this is not something that
>> I believe you could sort out in a couple of days. To get the
>> cross section right and elimiate the trigger efficiency effect,
>> you really HAVE to look at a benchmark channel (such as Omega) in
>> detail, this would normally takes months of work. If I were you,
>> I would grap whatever craig has for the omega, and try to get the
>> scaling factor from the expected discontinuity, and compare that
>> with existing data.
>>
>>
>> Lei
>>
>>
>> --
>> Johann Goetz
>> jgoetz at ucla.edu <mailto:jgoetz at ucla.edu>
>>
>> UCLA Dept. Physics & Astronomy
>> Nefkens Group
>>
>> **************************************
>> @
>> / *
>> / ___ ___ Lei Guo _______________________
>> L_O_/ ____ Florida International University____/_/
>> \ | Physics Dept., CP
>> 212 / /
>> / \ | Miami, FL
>> 33199 / / /
>> / I_/ \ ____ USA _____ /______/__________/ /
>> / /
>> L
>> / / / / /
>> / / / / / / /
>> /_/__________/______/______/__________/_/
>> /_/__________/______/______/__________/_/
>> 305-348-0234(o)
>>
>> **************************************
>>
>>
>>
>>
>>
>>
>>
>>
>> --
>> -------------------------------------------------------------------------
>> Craig Bookwalter FSU Office: (850) 644 3808
>> Department of Physics JLab Office: (757) 269 5465
>> Florida State University craigb at hadron.physics.fsu.edu
>> Tallahasse, FL 32306 craigb at jlab.org
>>
>>
>> "One toke? You poor fool. Just wait till you see those (expletive)
>> bats."
>> -------------------------------------------------------------------------
>>
>>
>>
>>
>> --
>> Johann Goetz
>> jgoetz at ucla.edu
>> UCLA Dept. Physics & Astronomy
>> Nefkens Group
>
> **************************************
> @
> / *
> / ___ ___ Lei Guo _______________________
> L_O_/ ____ Florida International University____/_/
> \ | Physics Dept., CP
> 212 / /
> / \ | Miami, FL
> 33199 / / /
> / I_/ \ ____ USA _____ /______/__________/ /
> / /
> L
> / / / / /
> / / / / / / /
> /_/__________/______/______/__________/_/
> /_/__________/______/______/__________/_/
> 305-348-0234(o)
>
> **************************************
>
>
>
>
>
>
**************************************
@
/ *
/ ___ ___ Lei Guo _______________________
L_O_/ ____ Florida International University____/_/
\ | Physics Dept., CP
212 / /
/ \ | Miami, FL
33199 / / /
/ I_/ \ ____ USA _____ /______/__________/ /
/ /
L
/ / / / /
/ / / / / / /
/_/__________/______/______/__________/_/
/_/__________/______/______/__________/_/
305-348-0234(o)
**************************************
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