Re: GEANT-3 grkuta

Hello,

To transport a particle backward I either switch the sign of momentum and direction cosines or the sign of step. If I'm not mistaken, the two are mathematically equivalent, and I was trying to do the latter, hence found the bug.
Of course, for the purpose of simulation the step is always positive, but in case of reconstruction, it may be negative.

Regards,
Andre.

Victor Perevoztchikov wrote:
> Hi Andre,
>
>> - Speed of light is 299,792,510 instead of 299,792,458 (PDG value)
>>
> you are right, but:
> - we never know mag field with accuracy better 1e-6
> - grkuta is estimation, neglecting energy loss, multiple scatterring,
> etc...
> So it is no important.
>
>
>> - In line 110 comparison "IF (EST.GT.H)" assumes that H is positive,
>>
> H is always positive. It is a step in direction of particle momentum.
>
>
>> while if I'm not mistaken it doesn't have to be (and elsewhere
>> comparison is always to abs(h))
>>
> You right, abs(H) is redundant.
>
> Victor
>
>
> Victor M. Perevoztchikov perev_at_bnl.gov
> Brookhaven National Laboratory MS 510A PO Box 5000 Upton NY 11973-5000
> tel office : 631-344-7894; fax 631-344-4206;
>
> ----- Original Message -----
> From: "Andre Lebedev" <lebedev_at_fas.harvard.edu>
> To: <vmc_at_pcroot.cern.ch>
> Sent: Monday, November 27, 2006 7:09 PM
> Subject: [VMC] GEANT-3 grkuta
>
>
>
>> Hello.
>>
>> I've noticed 2 minor issues with GEANT3 Runge-Kutta stepper
>> - Speed of light is 299,792,510 instead of 299,792,458 (PDG value)
>> - In line 110 comparison "IF (EST.GT.H)" assumes that H is positive,
>> while if I'm not mistaken it doesn't have to be (and elsewhere
>> comparison is always to abs(h))
>>
>> Neither is a show stopper, but given the fact that G3 is still sort of
>> supported in the realm of virtual MC, you may be in a good position to
>> address these bugs.
>>
>> Best regards,
>> Andre.
>>
>>
Received on Tue Nov 28 2006 - 14:55:04 MET