WHIZARD

Pythia8 error with beam gaussian spread

Asked by Aram Apyan

Hi,

I try to generate e+e- collision events (*) with Whizard with a gaussian beam spread. When I try to shower the events with Pythia8 I get errors and after couple of hundred events it aborts (**).

    11 Abort from Pythia::next: processLevel failed; giving up |
 | 209 Error in ProcessContainer::constructProcess: setting mass failed |

If I remove the beam spread things seem to work and I get back the number of requested events.

Am I missing something with my pythia8 setup when using the beam spread?

Best,

Aram

(*)
For example:

process eeww = e1, E1 => ("W+", "W-")
beams = e1, E1 => gaussian => isr
gaussian_spread1 = 0.165%
gaussian_spread2 = 0.165%
sqrts = 240 GeV
n_events = 10000
sample_format = lhef
simulate (eeww)

(**)
*------- PYTHIA Process Initialization --------------------------*
 | |
 | We collide e- with e+ at a CM energy of 2.400e+02 GeV |
 | |
 |------------------------------------------------------------------|
 | | |
 | Subprocess Code | Estimated |
 | | max (mb) |
 | | |
 |------------------------------------------------------------------|
 | | |
 | Les Houches User Process(es) 9999 | 1.664e-08 |
 | |
 *------- End PYTHIA Process Initialization -----------------------*

 *------- PYTHIA Flag + Mode + Parm + Word + FVec + MVec + PVec + WVec Settings (changes only) ------------------*
 | |
 | Name | Now | Default Min Max |
 | | | |
 | Beams:eCM | 240.00000 | 14000.000 10.00000 |
 | Beams:frameType | 4 | 1 1 5 |
 | Beams:LHEF | /tmp/arapyan/eeww.lhe | void |
 | Init:showChangedParticleData | off | on |
 | Main:numberOfEvents | 200000 | 1000 0 |
 | Next:numberCount | 100 | 1000 0 |
 | Next:numberShowEvent | 0 | 1 0 |
 | StringFlav:etaSup | 0.63000 | 0.60000 0.0 1.00000 |
 | StringFlav:mesonBvector | 3.00000 | 2.20000 0.0 3.00000 |
 | StringFlav:mesonCvector | 1.06000 | 0.88000 0.0 3.00000 |
 | StringFlav:mesonSvector | 0.72500 | 0.55000 0.0 3.00000 |
 | StringFlav:mesonUDvector | 0.62000 | 0.50000 0.0 3.00000 |
 | StringFlav:popcornSpair | 0.50000 | 0.90000 0.0 1.00000 |
 | StringFlav:probQQ1toQQ0 | 0.0270000 | 0.0275000 0.0 1.00000 |
 | StringFlav:probQQtoQ | 0.0900000 | 0.0810000 0.0 1.00000 |
 | StringFlav:probSQtoQQ | 1.00000 | 0.91500 0.0 1.00000 |
 | StringFlav:probStoUD | 0.19000 | 0.21700 0.0 1.00000 |
 | StringPT:sigma | 0.30400 | 0.33500 0.0 1.00000 |
 | StringZ:aExtraDiquark | 0.50000 | 0.97000 0.0 2.00000 |
 | StringZ:aLund | 0.30000 | 0.68000 0.0 2.00000 |
 | StringZ:bLund | 0.80000 | 0.98000 0.20000 2.00000 |
 | StringZ:rFactB | 0.67000 | 0.85500 0.0 2.00000 |
 | StringZ:rFactC | 1.00000 | 1.32000 0.0 2.00000 |
 | TimeShower:alphaSvalue | 0.13830 | 0.13650 0.0600000 0.25000 |
 | TimeShower:pTmin | 0.40000 | 0.50000 0.10000 2.00000 |
 | TimeShower:pTminChgQ | 0.40000 | 0.50000 0.10000 2.00000 |
 | Tune:ee | 3 | 7 -1 7 |
 | |
 *------- End PYTHIA Flag + Mode + Parm + Word + FVec + MVec + PVec + WVec Settings -----------------------------*

 -------- LHA initialization information ------------

  beam kind energy pdfgrp pdfset
     A 11 120.000 -1 -1
     B -11 120.000 -1 -1

  Event weighting strategy = 3

  Processes, with strategy-dependent cross section info
  number xsec (pb) xerr (pb) xmax (pb)
       1 1.6641e+01 3.0473e-02 1.0000e+00

 -------- End LHA initialization information --------

 -------- LHA event information and listing ----------------------------------------------------------------------

    process = 1 weight = 1.0000e+00 scale = 2.3658e+02 (GeV)
                        alpha_em = -1.0000e+00 alpha_strong = 1.1780e-01

    Participating Particles
    no id stat mothers colours p_x p_y p_z e m tau spin
     1 11 -1 0 0 0 0 0.000 0.000 119.880 119.880 0.001 0.000 9.000
     2 -11 -1 0 0 0 0 0.000 0.000 -116.720 116.720 0.001 0.000 9.000
     3 24 1 1 2 0 0 -27.363 24.724 -76.946 117.251 80.419 0.000 9.000
     4 -24 1 1 2 0 0 27.363 -24.724 80.105 119.349 80.419 0.000 9.000

 -------- End LHA event information and listing ------------------------------------------------------------------

 -------- PYTHIA Info Listing ----------------------------------------

 Beam A: id = 11, pz = 1.200e+02, e = 1.200e+02, m = 5.110e-04.
 Beam B: id = -11, pz = -1.200e+02, e = 1.200e+02, m = 5.110e-04.

 In 1: id = 11, x = 9.990e-01, pdf = 0.000e+00 at Q2 = 5.597e+04.
 In 2: id = -11, x = 9.727e-01, pdf = 0.000e+00 at same Q2.

 Process Les Houches User Process(es) with code 9999 is 2 -> 2.
 Subprocess user process 1 with code 1 is 2 -> 2.
 It has sHat = 5.597e+04, tHat = -4.009e+04, uHat = -2.942e+03,
       pTHat = 3.688e+01, m3Hat = 8.042e+01, m4Hat = 8.042e+01,
    thetaHat = 2.703e+00, phiHat = 2.407e+00.
     alphaEM = 7.903e-03, alphaS = 1.178e-01 at Q2 = 5.597e+04.

 Impact parameter b = 0.000e+00 gives enhancement factor = 1.000e+00.
 Max pT scale for MPI = 2.400e+02, ISR = 2.400e+02, FSR = 2.400e+02.
 Number of MPI = 1, ISR = 2, FSRproc = 0, FSRreson = 20.

 -------- End PYTHIA Info Listing ------------------------------------

 -------- PYTHIA Event Listing (hard process) -----------------------------------------------------------------------------------

    no id name status mothers daughters colours p_x p_y p_z e m
     0 90 (system) -11 0 0 0 0 0 0 0.000 0.000 0.000 240.000 240.000
     1 11 (e-) -12 0 0 3 0 0 0 0.000 0.000 120.000 120.000 0.001
     2 -11 (e+) -12 0 0 4 0 0 0 0.000 0.000 -120.000 120.000 0.001
     3 11 (e-) -21 1 0 5 6 0 0 0.000 0.000 119.880 119.880 0.000
     4 -11 (e+) -21 2 0 5 6 0 0 0.000 0.000 -116.720 116.720 0.000
     5 24 (W+) -22 3 4 7 8 0 0 -27.363 24.724 -76.946 117.251 80.419
     6 -24 (W-) -22 3 4 9 10 0 0 27.363 -24.724 80.105 119.349 80.419
     7 -3 sbar 23 5 0 0 0 0 101 -37.047 28.203 -89.537 100.921 0.500
     8 4 c 23 5 0 0 0 101 0 9.684 -3.479 12.591 16.330 1.500
     9 1 d 23 6 0 0 0 102 0 15.979 23.856 4.951 29.139 0.330
    10 -2 ubar 23 6 0 0 0 0 102 11.383 -48.579 75.154 90.210 0.330
                                   Charge sum: 0.000 Momentum sum: 0.000 -0.000 3.160 236.600 236.579

 -------- End PYTHIA Event Listing -----------------------------------------------------------------------------------------------
 PYTHIA Error in ProcessContainer::constructProcess: setting mass failed
 PYTHIA Abort from Pythia::next: processLevel failed; giving up
** 99 events processed
 Pythia::next(): 100 events have been generated
Event generation aborted prematurely, owing to error!
** 165 events processed

 *------- PYTHIA Event and Cross Section Statistics -------------------------------------------------------------*
 | |
 | Subprocess Code | Number of events | sigma +- delta |
 | | Tried Selected Accepted | (estimated) (mb) |
 | | | |
 |-----------------------------------------------------------------------------------------------------------------|
 | | | |
 | Les Houches User Process(es) 9999 | 364 364 155 | 7.132e-09 4.343e-10 |
 | ... whereof user classification code 1 | 364 364 155 | |
 | | | |
 | sum | 364 364 155 | 7.132e-09 4.343e-10 |
 | |
 *------- End PYTHIA Event and Cross Section Statistics ----------------------------------------------------------*

 *------- PYTHIA Error and Warning Messages Statistics ----------------------------------------------------------*
 | |
 | times message |
 | |
 | 11 Abort from Pythia::next: processLevel failed; giving up |
 | 209 Error in ProcessContainer::constructProcess: setting mass failed |
 | 1 Warning in JetMatchingMadgraph:init: Madgraph merging parameters not found |
 | 1 Warning in JetMatchingMadgraph:init: No alpsfact |
 | 1 Warning in JetMatchingMadgraph:init: No ickkw |
 | 1 Warning in JetMatchingMadgraph:init: No maxjetflavor |
 | 1 Warning in JetMatchingMadgraph:init: No xqcut |
 | |
 *------- End PYTHIA Error and Warning Messages Statistics ------------------------------------------------------*

Question information

Language:
English Edit question
Status:
Solved
For:
WHIZARD Edit question
Assignee:
Juergen Reuter Edit question
Last query:
Last reply:
Revision history for this message
Juergen Reuter (j.r.reuter) said : 		#1

Hi Aram,
this error comes from Pythia8 not (easily) accepting variable beam energies as they are triggered by the Gaussian energy spread. Effectively, the main23.cc example that ships with the Pythia8 distribution does exactly that, a Gaussian beam momentum/energy spread. There is a numerical tolerance in Pythia8 of the order (2 times) 1E-6 for the beam energy to vary. If a lower the Gaussian spread of your beams below that threshold, the events run true. If you are using the WHIZARD built-in Pythia8 interface such an event would just be skipped (as Simon has written in Launchpad question 696900), however, clearly one wants also the extreme events from the Gaussian beam distribution. I thought this could be solved by setting
Beams:allowMomentumSpread = on
in Pythia8, but this doesn't help. You should contact the Pythia8 authors and ask them what to do in such a case.
Cheers,
    JRR (Juergen Reuter)

Revision history for this message
Aram Apyan (arapyan) said : 		#2

Hi Juergen,

Ok thank you. I will contact the Pythia8 authors.

Best,

Aram

Revision history for this message
Juergen Reuter (j.r.reuter) said : 		#3

Seems to be solved.