From: Christopher Tunnell (tunnell@mail.utexas.edu)
Date: Wed Sep 21 2005 - 11:57:27 CDT
Does Glenn read this list?
It was my belief that events were independent. Even though some
information travels over through one event changing properties of the
scintillator, I am pretty sure that Geant4 runs each event separately
and measures hit-times relative to when the event started. There is a
global event clock in which hit-times are calculated relative to the
global time. This means that events can happen concurrently, but the
event data will not show this.
What would generate these neutrons other than a bug though? Can you
test out your muon command a little more by seeing if the command works
for, let's say, a 200 MeV muon with a momentum vector pointing in
(1,1,1) at the center of the detector? Can you find any cases in which
it does work and also do you get the same data I get when you run my
commands?
Are you running the CVS head?
Stephen Jacob Sekula wrote:
> Hi Chris,
>
> This is me brainstorming, too: could the primaries in later events be
> secondaries from prior events? I noticed that there is a time
> structure in these events; can events overlap? If so, a neutron from
> one event might end up being the first thing in the next event.
>
> Steve
>
> Christopher Tunnell wrote:
>
>> As I think about it more, it might also be the combination of two
>> things. First, it seems like, after looking at my last e-mail's
>> data, that primaries can be muons post-decay (GLG4sim specific).
>> This makes sense for why the electrons (see last e-mail) are there,
>> but if you run "/particle/find 13", it says muons decay into
>> anti-electron neutrinos. I believe some IBD code was submitted
>> recently. Could it be that the IBD code somehow enters a loop or
>> makes an error when it generates the neutrons from IBD?
>>
>> This is me brainstorming, but I figured that you might not have
>> thought this since you thought the mysterious particles were protons
>> instead of neutrons. Tell me if you get any use from this reasoning
>> and also if I am right about new IBD code please.
>>
>> Good luck,
>> Chris
>>
>> Stephen Jacob Sekula wrote:
>>
>>> Hi Again,
>>>
>>> I did a little more investigating on this muon generation issue. I
>>> replace "mu-" with "e-" everywhere in my .mac file and re-ran the
>>> study. That worked perfectly - all the primaries were e-. So, it
>>> looks like I need to concentrate on how the particle gun handles
>>> muons...
>>>
>>> Any more info would still be helpful.
>>>
>>> Cheers,
>>> Steve
>>>
>>> Stephen Jacob Sekula wrote:
>>>
>>>> Hi Folks,
>>>>
>>>> I need some help. I'm trying to test my addition to the RAT event
>>>> tree (I wrote a processor for the veto system, etc.). To do this, I
>>>> wanted to fire 1000 "cosmic ray" muons into the cave. I wanted to
>>>> sample from a spectrum that was logarithmically flat in energy
>>>> (10^2-10^6 MeV) and flat in zenith angle (cosTheta -1.0 - -0.3).
>>>>
>>>> I tried making a HEPEVT file, as for the IBD events. This wasn't
>>>> successful, so instead I generated a .mac file with lines as follows:
>>>>
>>>> /generator/pos/set 9 "7275.89 6585.75 10000"
>>>> /generator/vtx/set 17 "mu- -0.246024 0.769951 -0.588767 270.184"
>>>> /run/beamOn 1
>>>> /generator/pos/set 9 "9825.88 7919.56 10000"
>>>> /generator/vtx/set 17 "mu- -0.39135 -0.220177 -0.893514 145.48"
>>>> /run/beamOn 1
>>>> /generator/pos/set 9 "9357.36 7233.58 10000"
>>>> /generator/vtx/set 17 "mu- -0.546423 0.101814 -0.831298 577776"
>>>> /run/beamOn 1
>>>> .
>>>> .
>>>> .
>>>>
>>>> I did this 1000 times.
>>>>
>>>> This should have produced 1000 events with a primary being the
>>>> muon. When I look at the root file - in particular, when I scan the
>>>> primary in each event (and here I might have already made a mistake):
>>>>
>>>> root [3] T->Scan("mcparticle.pdgcode[0]")
>>>> ************************
>>>> * Row * mcparticl *
>>>> ************************
>>>> * 0 * 13 *
>>>> * 1 * 13 *
>>>> * 2 * 2112 *
>>>> * 3 * 2112 *
>>>> * 4 * 2112 *
>>>> * 5 * 2112 *
>>>> * 6 * 2112 *
>>>> * 7 * 2112 *
>>>> * 8 * 2112 *
>>>>
>>>> As you can see, the first two (for example) are muons. However, the
>>>> next 998 events appear to have protons as primaries.
>>>>
>>>> I assumed that the structure of my .mac file was the problem. So,
>>>> instead, I just ran this:
>>>>
>>>> /generator/pos/set 9 "7275.89 6585.75 10000"
>>>> /generator/vtx/set 17 "mu- 0.0 0.0 -1.0 270.184"
>>>> /run/beamOn 1000
>>>>
>>>>
>>>> But I got something similar to the above in the ROOT file.
>>>>
>>>> I think my fundamental problem is that I've either misunderstood
>>>> the way events are generated, or that I have misunderstood how
>>>> particles are counted as "primary" in these events. However, it's
>>>> also possible I've made some other mistake. Any help is very welcome!
>>>>
>>>>
>>>> By the way, I want to say that so far I've found the documentation
>>>> for RAT and the wiki to be excellent. I hope the above problem
>>>> isn't covered in the docs -- I thought I'd read all of it before
>>>> asking this here.
>>>>
>>>> Regards,
>>>> Steve
>>>>
>>>>
>>>
>>
>
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