Theta angle limit or -0.8<cos(theta)<0.8

You can add your cut in cuts.f

Cheers,

Olivier

> On 4 Mar 2017, at 15:43, Najimuddin Khan <email address hidden> wrote:
>
> New question #525566 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/525566
>
> Hi,
> I am calculating 2->2 processes, say processes w+,w- > w+ w-. Could anyone help me? how can I change the angular limit -0.8<cos(theta)<0.8 from the default values in Madgraph? Where the file is located?
>
>
> I have tried to chanege the file:
> Template/LO/Source/kin_functions.f: TEMP = MAX(-0.99999999D0, (P1(1)*P2(1) + P1(2)*P2(2)) / DENOM)
> Template/LO/Source/kin_functions.f: TEMP = MIN( 0.99999999D0, TEMP)
>
> 0.99999999 to 0.8, Result remain same.
>
> or
>
> Template/LO/Source/kin_functions.f: theta=dacos(p(3)/dsqrt(p(1)**2+p(2)**2+p(3)**2)) to dacos(0.8)
>
> Showing error.
>
>
> Help me regarding this issues.
>
>
> Thanks
> N Khan
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

HI Oliver,
I have use w+w- >w+w-. I have changed cuts.f file in SubProcesses folder :

Here the line are:
            IF(PABS1*PABS2 .NE. 0D0) THEN
              COSTH = ( PJET(I,1)*PJET(J,1) + PJET(I,2)*PJET(J,2) + PJET(I,3)*PJET(J,3) )/(PABS1*PABS2)
            ELSE
C IF 3-MOMENTA VANISH, MAKE JET COSTH = 1D0 SO THAT JET MEASURE VANISHES
              COSTH = 1D0
            ENDIF
C GET PT AND ETA OF JETS

I have replaced COSTH as 0.8D0.

Still result remain same (sigama~10^9 pb for ECM=500 GeV). It should be ~1 pb.

Please help me to find out the exact file.

Thanks
N Khan

Hi,

This is the correct file,
But you have to implement a cut.
I.e. you have to set pass_cuts=.false.
If you have costh>0.8

Here is an example of cut for the energy.
c
c E min & max cuts
c
      do i=nincoming+1,nexternal
         if(debug) write (*,*) 'p(0,',i,')=',p(0,i),' ',emin(i),':',emax(i)
         notgood=(p(0,i) .le. emin(i)).or.
     & (emax(i).ge.0d0 .and. p(0,i) .gt. emax(i))
         if (notgood) then
            if(debug) write (*,*) i,' -> fails'
            passcuts=.false.
            return
         endif
      enddo

Cheers,

Olivier

> On 5 Mar 2017, at 04:17, Najimuddin Khan <email address hidden> wrote:
>
> Question #525566 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/525566
>
> Status: Answered => Open
>
> Najimuddin Khan is still having a problem:
> HI Oliver,
> I have use w+w- >w+w-. I have changed cuts.f file in SubProcesses folder :
>
> Here the line are:
> IF(PABS1*PABS2 .NE. 0D0) THEN
> COSTH = ( PJET(I,1)*PJET(J,1) + PJET(I,2)*PJET(J,2) + PJET(I,3)*PJET(J,3) )/(PABS1*PABS2)
> ELSE
> C IF 3-MOMENTA VANISH, MAKE JET COSTH = 1D0 SO THAT JET MEASURE VANISHES
> COSTH = 1D0
> ENDIF
> C GET PT AND ETA OF JETS
>
> I have replaced COSTH as 0.8D0.
>
> Still result remain same (sigama~10^9 pb for ECM=500 GeV). It should be
> ~1 pb.
>
> Please help me to find out the exact file.
>
> Thanks
> N Khan
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,
I have tried to short out this but can't. I have set passcuts=.false. after setting COSTH=0.8D0. It is not compiled showing error. I have tried many possible way but the problem remain unsolved.

If possible kindly mail me the changes cuts.f file for w+w->w+w- with -0.8<costh<0.8 to "<email address hidden>" or send me few lines related to this cut to include in cuts.f file.

Thanks
N Khan

Hi,

You have to add line like

c
c cos theta cut (center of mass frame for 2 >2) associated to the following parametrisation:
c (E, p cos(theta) sin(phi), p sint(theta) sin(phi), p cos(phi)
C (p(2,3) is the px of the first outgoing particle (particle 1 and 2 are the incoming particle)
C (p(2,3) is the py of the first outgoing particle (particle 1 and 2 are the incoming particle)
        If (DABS(COS(ATAN(p(2,3)/p(1,3))>0.8) then
        passcuts = .false.
        endif

Cheers,

Olivier

PS:
The formatting of the line might be broken by the email, so ensure that your line are correctly formatted for fortran77

> On 5 Mar 2017, at 11:33, Najimuddin Khan <email address hidden> wrote:
>
> Question #525566 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/525566
>
> Status: Answered => Open
>
> Najimuddin Khan is still having a problem:
> Hi Olivier,
> I have tried to short out this but can't. I have set passcuts=.false. after setting COSTH=0.8D0. It is not compiled showing error. I have tried many possible way but the problem remain unsolved.
>
> If possible kindly mail me the changes cuts.f file for w+w->w+w- with
> -0.8<costh<0.8 to "<email address hidden>" or send me few lines
> related to this cut to include in cuts.f file.
>
> Thanks
> N Khan
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Thnks, I have changed few lines using your suggestions.