Warnings in HepEvt translation of QED radiation blobs

[Frank Siegert]

In 10k photon+jet events, the following warnings are shown from the translation into HepEvt events and from Signal_Process_FS_QED_Correction:

----------------------------------------------------------
-- SHERPA generates events with the following structure --
----------------------------------------------------------
Perturbative       : Signal_Processes
Perturbative       : Hard_Decays
Perturbative       : Jet_Evolution:CSS
Perturbative       : Lepton_FS_QED_Corrections:None
Perturbative       : Multiple_Interactions:None
Hadronization      : Beam_Remnants
Hadronization      : Hadronization:Ahadic
Hadronization      : Hadron_Decays,Photons
---------------------------------------------------------
===================================================i May 21 18:58
ERROR in Momenta_Stretcher::MassThem :
   Too little energy: 1.777 + 1.777 > 2.86200741898.
Error in Momenta_Stretcher::StretchMomenta(const Particle_Vector&, masses).
Signal_Process_FS_QED_Correction::Treat(0x87d2354,1630.39196956):
  Leptons could not be put on their mass shell.
  Trying new event.
HepEvt_Interface::QEDBlobs2HepEvt:("Warning: QED Radiation blob with more than two incoming particles. Translation skipped.")
HepEvt_Interface::Sherpa2HepEvt:("Warning(1): Unusual hadron-decay blob, cannot yet correct for it.")
===================================================
ERROR in Momenta_Stretcher::MassThem :
   Too little energy: 1.777 + 1.777 > 2.27525272969.
Error in Momenta_Stretcher::StretchMomenta(const Particle_Vector&, masses).
Signal_Process_FS_QED_Correction::Treat(0x87d2354,500.887404699):
  Leptons could not be put on their mass shell.
  Trying new event.
HepEvt_Interface::QEDBlobs2HepEvt:("Warning: QED Radiation blob with more than two incoming particles. Translation skipped.")
HepEvt_Interface::QEDBlobs2HepEvt:("Warning: QED Radiation blob with more than two incoming particles. Translation skipped.")
===================================================A: Fri May 21 18:57
ERROR in Momenta_Stretcher::MassThem :
   Too little energy: 1.777 + 1.777 > 3.47800837307.
Error in Momenta_Stretcher::StretchMomenta(const Particle_Vector&, masses).
Signal_Process_FS_QED_Correction::Treat(0x87d2354,896.343561712):
  Leptons could not be put on their mass shell.
  Trying new event.
HepEvt_Interface::QEDBlobs2HepEvt:("Warning: QED Radiation blob with more than two incoming particles. Translation skipped.")
===================================================A: Fri May 21 18:57
ERROR in Momenta_Stretcher::MassThem :
   Too little energy: 1.777 + 1.777 > 3.29069418031.
Error in Momenta_Stretcher::StretchMomenta(const Particle_Vector&, masses).
Signal_Process_FS_QED_Correction::Treat(0x87d2354,1879.02524031):
  Leptons could not be put on their mass shell.
  Trying new event.
HepEvt_Interface::QEDBlobs2HepEvt:("Warning: QED Radiation blob with more than two incoming particles. Translation skipped.")
HepEvt_Interface::QEDBlobs2HepEvt:("Warning: QED Radiation blob with more than two incoming particles. Translation skipped.")
HepEvt_Interface::Sherpa2HepEvt:("Warning(1): Unusual hadron-decay blob, cannot yet correct for it.")
HepEvt_Interface::QEDBlobs2HepEvt:("Warning: QED Radiation blob with more than two incoming particles. Translation skipped.")
HepEvt_Interface::QEDBlobs2HepEvt:("Warning: QED Radiation blob with more than two incoming particles. Translation skipped.")
HepEvt_Interface::Sherpa2HepEvt:("Warning(1): Unusual hadron-decay blob, cannot yet correct for it.")
HepEvt_Interface::QEDBlobs2HepEvt:("Warning: QED Radiation blob with more than two incoming particles. Translation skipped.")
===================================================Fri May 21 18:57
ERROR in Momenta_Stretcher::MassThem :
   Too little energy: 1.777 + 1.777 > 3.26500527797.
Error in Momenta_Stretcher::StretchMomenta(const Particle_Vector&, masses).
Signal_Process_FS_QED_Correction::Treat(0x87d2354,4112.91448032):
  Leptons could not be put on their mass shell.
  Trying new event.
===================================================Fri May 21 18:57
ERROR in Momenta_Stretcher::MassThem :
   Too little energy: 1.777 + 1.777 > 3.48514458838.
Error in Momenta_Stretcher::StretchMomenta(const Particle_Vector&, masses).
Signal_Process_FS_QED_Correction::Treat(0x87d2354,4348.96459019):
  Leptons could not be put on their mass shell.
  Trying new event.
HepEvt_Interface::QEDBlobs2HepEvt:("Warning: QED Radiation blob with more than two incoming particles. Translation skipped.")
HepEvt_Interface::QEDBlobs2HepEvt:("Warning: QED Radiation blob with more than two incoming particles. Translation skipped.")
HepEvt_Interface::QEDBlobs2HepEvt:("Warning: QED Radiation blob with more than two incoming particles. Translation skipped.")
===================================================ri May 21 18:58
ERROR in Momenta_Stretcher::MassThem :
   Too little energy: 1.777 + 1.777 > 2.30383874575.
Error in Momenta_Stretcher::StretchMomenta(const Particle_Vector&, masses).
Signal_Process_FS_QED_Correction::Treat(0x87d2354,1822.43410189):
  Leptons could not be put on their mass shell.
  Trying new event.
===================================================ri May 21 18:58
ERROR in Momenta_Stretcher::MassThem :
   Too little energy: 1.777 + 1.777 > 2.52753814344.
Error in Momenta_Stretcher::StretchMomenta(const Particle_Vector&, masses).
Signal_Process_FS_QED_Correction::Treat(0x87d2354,138.085328036):
  Leptons could not be put on their mass shell.
  Trying new event.
  Event 10000 ( 257 s total )
In Event_Handler::Finish : Summarizing the run may take some time.
+-----------------------------------------------------+
|                                                     |
|  Total XS is 272.056 pb +- ( 11.2581 pb = 4.13 % )  |
|                                                     |
+-----------------------------------------------------+
Return_Value::PrintStatistics(): Statistics {
  Generated events: 10000
  New events {
    From "Jet_Evolution:CSS": 25695 (36480) -> 70.4 %
    From "Lepton_FS_QED_Corrections:None": 8 (315) -> 2.5 %
  }
  Retried phases {
    From "Hadron_Decays::RejectExclusiveChannelsFromFragmentation": 16 (1077) -> 1.4 %
  }
  Retried methods {
    From "Hadrons::DiceUncorrelatedKinematics": 14 (521712) -> 0 %
  }
}

The run card is attached.

We should check that these warnings are indeed harmless.

[marek]

The issue arises because of >2 non-strongly-charged particles (here usually three or more photons) leaving the Shower event phase. Thus, the QED_Radiation blobs have >3 incoming particles, which the current setup of the HepEvt translation can't cope with. These blobs are thus omitted from the HepEvt record. However, unfortunately, I am not an expert on the HepEvt event record details. Jan, could you look into this? Marek

[Jan Winter]

Dealt with the QED_Radiation blobs that have more than two incoming particles in the best possible way as allowed by the HepEvt format (the assignment of the mothers of the outgoing particles of the QED blob is not 100% optimal), i.e. the translation of these blobs will not be skipped anymore, the warnings HepEvt_Interface::QEDBlobs2HepEvt:("Warning: QED Radiation blob with more than two incoming particles. Translation skipped.")] have been resolved. The changes have been committed to branch 1.2.1 and trunk, a patch is available on the download page for version 1.2.1. Still open issues: 1) HepEvt_Interface::Sherpa2HepEvt:("Warning(1): Unusual hadron-decay blob, cannot yet correct for it.") This is rare but e.g. decaying J/psi's lead to additional shower and fragmentation blobs (not liked by interface). Have to see how to catch these cases and put into one hadron-decay blob. 2) There are still these errors "ERROR in Momenta_Stretcher::MassThem : ..." and "Error in Cluster::RescaleMomentum:" that have nothing to do with the sherpa-hepevt interface. They seem to lead to trying a new event. If this is OK we can ignore it, if not I'd like to ask FrankS and/or Marek to comment on this issue.

[Frank Siegert]

Replying to jan:

2) There are still these errors "ERROR in Momenta_Stretcher::MassThem : ..." and "Error in Cluster::RescaleMomentum:" that have nothing to do with the sherpa-hepevt interface. They seem to lead to trying a new event. If this is OK we can ignore it, if not I'd like to ask FrankS and/or Marek to comment on this issue.

This issue has been files as #82 such that this report here only deals with the HepEvt problems. Thanks for looking into those, and just ignore the Momenta_Stretcher warnings for the time being.

[Frank Siegert]

Jan, as far as I remember correctly, this is closed, right?

[Stefan Hoeche]

Milestone old deleted