From: Stephen Jacob Sekula (sekula@mit.edu)
Date: Wed Sep 21 2005 - 12:35:12 CDT
Hi Chris,
I have run both with a CVS checkout from a few days ago, and with the current
head (with all that RatDB stuff now in there). Same results.
I have a lot of suggestions to try, thanks to all the feedback from the group.
I'll start working on these tests (repeating your commands, repeating with
different energies) but not today. I have to set this work aside for a few days
for my BaBar work. I'll return to it either on the weekend or early next week.
Regards,
Steve
Christopher Tunnell wrote:
> 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
>>>>>
>>>>>
>>>>
>>>
>>
>
-- +--------------------+-------------------------------------------+ | Stephen J. Sekula | http://www.slac.stanford.edu/~sekula | | Post-Doc | http://steve.cooleysekula.org/ | +--------------------+-----------------+-------------------------+ | MIT Laboratory for Nuclear Science | SLAC: (650)-926-8596 | +--------------------------------------+-------------------------+
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