Using PDF in Calc, how to set the Q?

Hello Qiji,

my reply is in lines:

On 18/10/18 18:47, Qiji Xin wrote:
> New question #675342 on CalcHEP:
> https://answers.launchpad.net/calchep/+question/675342
>
> Hi,
>
> I am doing the electron proton DIS using CalcHEP. So I need consider different partons in the proton with the PDF.
>
> There are four input parameters:
> 1: PDF of 1st particle (electron): None
> 2: PDF of 2nd particle (quark): MRST2004
> 3: Energy for the 1st particle (electron): 200 GeV
> 4: Energy for the 2nd particle (quark): 100 GeV.
>
> However, since the PDF depends on Q, the transferred momentum, so which of the parameters above correspond to Q?
The value of Q for DIS is related to the virtuality of the photon.
for
e,q -> e,q
it is equal to (p_e(out) -p_e(initial))^2 = (p_3-p_1)^2 = t

in CalcHEP this will correspond to S13 value which will be negative.

Therefore Q=sqrt(-S13)
will be your natural QCD scale.

We will make the clarification about this in HELP (F1) and manual.

Regards,
Alexander

> Is it the "energy of the 2nd particle (quark)", since I think the energy of the quark energy in proton with a PDF is not specific?
>
> It is my first time using/learning the PDF, so hope my question is not so naive.
>
> Thanks very much!
>
> Best,
> Qiji
>
>
>

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