SPINUP(I) = 9 for all particles in all events for calchep_batch generated .lhe files

Asked by Atanu Guha

 I am facing a problem while using calchep generated .lhe files in pythia8 interface. The beam polarization option is not working and in the generated .lhe files, the last column of all the events (I guess the spin info for the corresponding particles, the standrad .lhe format SPINUP(I)) is set to value 9.0 for all particles. This signifies lack of spin info in .lhe files, Unknown or unpolarized particles generally be given SPINUP(I)=9. For that reason Pythia8 is crashing.

Please find my batch file attached. Is there a way to resolve this issue?

##################################
Model: SM
Model changed: False
Gauge: Feynman
Process: e%,E%->n,N,A

Polarization1:-0.5
Polarization2:0.5

#Composite: le=e,m
#Composite: Le=E,M
Composite: n=ne,nm
Composite: N=Ne,Nm

Kinematics : 12 -> 34 , 5
Kinematics : 34 -> 3 , 4

pdf1: ISR & Beamstrahlung
pdf2: ISR & Beamstrahlung

Bunch x+y sizes (nm) : 480
Bunch length (mm) : 0.3
Number of particles : 2E+10

p1: 500
p2: 500

Cut parameter: T(A)
Cut invert: False
Cut min: 10
Cut max: 500

Cut parameter: E(A)
Cut invert: False
Cut min: 10
Cut max: 500

Cut parameter: Y(A)
Cut invert: False
Cut min: -2.5
Cut max: +2.5

Regularisation momentum: 12
Regularization mass: MZ
Regularization width: wZ
Regularization power: 2

Regularisation momentum: 34
Regularization mass: MZ
Regularization width: wZ
Regularization power: 2

Regularisation momentum: 13
Regularization mass: MW
Regularization width: wW
Regularization power: 2

Regularisation momentum: 24
Regularization mass: MW
Regularization width: wW
Regularization power: 2

Regularisation momentum: 24
Regularization mass: MW
Regularization width: wW
Regularization power: 2

Regularisation momentum: 14
Regularization mass: MW
Regularization width: wW
Regularization power: 2

Dist parameter: M(n,N)
Dist min: 0
Dist max: 600
Dist n bins: 100
Dist title: e,E->n,N,A
Dist x-title: M(n,N) (GeV)

Dist parameter: N(A)
Dist min: -5
Dist max: 5
Dist n bins: 300
Dist title: e,E->n,N,A
Dist x-title: N(A)

Dist parameter: T(A)
Dist min: 0
Dist max: 600
Dist n bins: 100
Dist title: e,E->n,N,A
Dist x-title: T(A) (GeV)

Dist parameter: E(A)
Dist min: 0
Dist max: 600
Dist n bins: 100
Dist title: e,E->n,N,A
Dist x-title: E(A) (GeV)

Dist parameter: Y(A)
Dist min: -4.0
Dist max: +4.0
Dist n bins: 100
Dist title: e,E->n,N,A
Dist x-title: Y(A)

Dist parameter: J(n,N)
Dist min: 0
Dist max: 7
Dist n bins: 300
Dist title: e,E->n,N,A
Dist x-title: J(n,N)

Number of events (per run step): 11000
Filename: ee_nNA1

NTuple: False
Cleanup: False
Max number of cpus: 8

nSess_1: 5
nCalls_1: 100000
nSess_2: 5
nCalls_2: 100000
##################################

Question information

Language:
English Edit question
Status:
Solved
For:
CalcHEP Edit question
Assignee:
No assignee Edit question
Solved by:
Alexander Belyaev
Solved:
Last query:
Last reply:
Revision history for this message
Atanu Guha (atanu-guha) said :
#1

Sorry. The problem were somewhere else. I was just playing with different options. What I found is as following.

I tried producing the same above mentioned process using the same batch file

I just removed the following two lines

pdf1: ISR & Beamstrahlung
pdf2: ISR & Beamstrahlung

Then everything is working fine. The moment I switch off the pdf option, pythia8 also recognising all the events and I am able to generate hepMC file out of that.

Do I need to use some extra option with the pdf-- ISR & Beamstrahlung

Please help me out in this regard.

Revision history for this message
Alexander Belyaev (alexander.belyaev) said :
#2

Dear Atanu,

the problem is that PYTHIA is crashing
when you use
pdf1: ISR & Beamstrahlung
pdf2: ISR & Beamstrahlung

Therefore the problem look slike in your PYTHIA main program.
Please send us PYTHIA main program and cards, so we can investigate details.

Please send these details to me to <email address hidden>

Let me also note that the absence of the information about the polarization of the initial beam in the .lhe file is not a problem at all. This absence does not affect the correctness of the physics you are exploring. We will ad this infrmation in the next release but is will be usefull only for bookeeping purposes.

Best,
Alexander

Revision history for this message
Atanu Guha (atanu-guha) said :
#3

Yeah.. That was my mistake. The absence of the information about the polarization of the initial beam in the .lhe file is not a problem at all. I am sending you the pythia main program in which I just wanted to convert the .lhe events in hepMC format.

Revision history for this message
Atanu Guha (atanu-guha) said :
#4

Dear sir,

I just wanted to provide you some more information.

I tried to produce the following process

e,E -> ne,Ne (Previously I was producing e,E -> ne,Ne, A)
with the pdf option

pdf1: ISR & Beamstrahlung
pdf2: ISR & Beamstrahlung

The .lhe file, I am exporting to pythia and using the main42.cc attached above. This is giving the same error as earlier (as listed below)

PYTHIA Error in Pythia::next: partonLevel failed; try again
 PYTHIA Abort from Pythia::next: parton+hadronLevel failed; giving up
 Event generation aborted prematurely, owing to error!

The problem is that PYTHIA is crashing when I use
pdf1: ISR & Beamstrahlung
pdf2: ISR & Beamstrahlung

I guess I need to use some extra constraints with the pdf option ISR & Beamstrahlung, either is pythia or in calchep. But I don't know how to resolve this issue.

Thank you. With best regards.

Revision history for this message
Best Alexander Belyaev (alexander.belyaev) said :
#5

Dear Atanu,

the problem is solved now. This was a problem on PYTHIA side introduced in the recent versions.
We have identified the problem and have decided to resolve it using the modification we have done in CalcHEP. So, instead of you wait for new PYTHIA version, you can download new CalcHEP version 3.83 now and run your events with PYTHIA.
In short -- electrons with ISR&Beanstrahlug have often momentum very close to initial one such that they numerically indistinguishable. Previous versions of PYTHIA were able to deal with sch events, reconstructing initial electron as electron + photon after ISR&Beanstrahlug even if the
energy of the photon is zero at the numerical level. The recent versions of PYTHIA fail to do this and this cause the problem you have faced with. We have mofied CalcHEP to solve this problem.

Best,
Alexander Pukhov and Alexander Belyaev

Revision history for this message
Atanu Guha (atanu-guha) said :
#6

Thank you very much sir for the updation of calchep. I downloaded and used the events in pythia... now it is running successfully without any error.

Thanks a lot again.

With best regards.

Atanu

Revision history for this message
Atanu Guha (atanu-guha) said :
#7

Thanks Alexander Belyaev, that solved my question.