Hi Alberto,
For the very special case where the positron beam is near the fixed
target threshold of 43.7 GeV for two-muon production AND the target
is only a few tenths of a radiation length so that the EM shower
hasn't fully developed, this process is more than two orders of
magnitude larger than Bethe-Heitler production for muon laboratory
momenta of about half the beam energy.
Right now I don't have a scholarly reference, but I'm attaching a
short .pdf file showing the formula for the muon production cross
section as a function of the positron beam energy. At fixed target
threshold the total cross section is about two microbarns. The cross
section is maximum at threshold and falls as one over the square of
the center-of-mass beam energy (as those who have worked at
e+e- colliders are familiar).
This process is in MUCARLO but it needs the positron track length for
the beam energy and target being studied. So one first needs to get
the positron track length (and photon track length if needed for
Bethe-Heitler production) from FLUKA and transfer that to MUCARLO.
If you want I can send that part of the FORTRAN code from MUCARLO.
Lew
On Nov 10, 2013, at 12:33 AM, Fasso, Alberto wrote:
> Hi Lew,
>
> nice to hear from you again!
> I am afraid that muon production by e+e- annihilation is not
> implemented in FLUKA. Is it in MUCARLO? (I don't remember).
> In any case, do you have any good reference to it?
>
> Alberto
>
> ________________________________________
> From: Lewis Keller [keller_at_slac.stanford.edu]
> Sent: Saturday, November 09, 2013 1:04 PM
> To: Fasso, Alberto
> Cc: Andrea.Mairani_at_mi.infn.it; "belgin piliçer"; fluka-
> discuss_at_fluka.org
> Subject: Re: [fluka-discuss]: muon production frm gamma conversion
> or positron annhilation
>
> Hi Alberto,
>
> As far as I can tell PHOTONUC only biases Bethe-Heitler production
> of muons. How does one bias direct annihilation, e+e- => u+u- ?
>
> Lew Keller
>
> On Nov 9, 2013, at 9:50 AM, "Fasso, Alberto"
> <fasso_at_SLAC.Stanford.EDU> wrote:
>
>> You don't get any muons because the cross section for muon pair
>> production is very small (about 1.E4 times smaller than that for e
>> +e- production). You need to bias the production by a factor of
>> that order.
>> Set WHAT(2) = 1.E-4 in the PHOTONUC card with SDUM=MUMUPAIR.
>>
>> Alberto
>> ________________________________________
>> From: owner-fluka-discuss_at_mi.infn.it [owner-fluka-
>> discuss_at_mi.infn.it] On Behalf Of Andrea.Mairani_at_mi.infn.it
>> [Andrea.Mairani_at_mi.infn.it]
>> Sent: Saturday, November 09, 2013 8:22 AM
>> To: "belgin piliçer"
>> Cc: fluka-discuss_at_fluka.org
>> Subject: Re: [fluka-discuss]: muon production frm gamma conversion
>> or positron annhilation
>>
>> Dear User,
>> Can you please send us your entire input? So we can check it and
>> in case
>> run it..
>> Regards,
>> Andrea
>>
>>> Dear Fluka Users,
>>>
>>> I want to produce the energy spectrum of muons from positron
>>> annihilation
>>> or gamma conversion by impinging the electrons to carbon target.
>>> Is it
>>> possible?
>>> I read that by using PHOTONUC card, MuMuPair option can switch on.
>>> I used these cards but I didn't observe the muons.
>>>
>>> PHOTONUC 1111. 0.0 0.0 CARBON CARBON
>>> 0.0MUMUPAIR
>>> USRTRACK 1. MUONS -26. TARGET
>>> 500.mu
>>> USRTRACK 1500.0 500.
>>> USRBIN 11. MUONS -21. 10.0 0.0
>>> 40.0mu
>>> USRBIN 0.0 0.0 0.0 100.0 1.0
>>> 400. &
>>> USRBIN 11. ENERGY -24. 10.0 0.0
>>> 40.0edep
>>> USRBIN 0.0 0.0 0.0 100.0 1.0
>>> 400. &
>>>
>>> Thanks for your advice and help from now.
>>>
>>
>>
>
Received on Sun Nov 10 2013 - 12:49:25 CET