People involved: Eric & Benj

Sample size: example of ttbar dileptonic @ LHC (10,000 events)

• defining a format for jet-clustering output (without fast-simulation detector).

• defining a format which extends the LHCO content (too few information for performing sophisticated analysis).

• the new format will take into account all Delphes 3 potential.

• Using text format. ROOT is rejected ; STDHEP seems to be old.

• Prefering extending an existing format to defining a totally new one (avoiding developers from coding writer and reader functions from scratch). Our choice is to extend the LHE Format (arXiv:hep-ph/0609017) and its structure based on XML tags. Reminder about the LHE structure:

<LesHouchesEvents version="X">
<header>
...
</header>
<init>
2212     2212  0.40000000000E+04  0.40000000000E+04 0 0 10042 10042 3  1
0.47468358499E+01  0.15068796356E-01  0.47469000000E-03   0
...
</init>
<event>
 12   0  0.4746900E-03  0.2312331E+03  0.7957747E-01  0.1132798E+00
 21   -1    0    0  501  502  0.00000000000E+00  0.00000000000E+00  0.74064204368E+02   0.74064204368E+02  0.00000000000E+00 0.  1.
 21   -1    0    0  502  503  0.00000000000E+00  0.00000000000E+00 -0.74552086368E+03  0.74552086368E+03  0.00000000000E+00 0.  1.
 -6    2    1    2    0  503  0.14952840473E+03 -0.23999735524E+02 -0.41424800778E+03  0.47441561784E+03  0.17473990778E+03 0.  0.
-24    2    3    3    0    0  0.56722398399E+02 -0.36860071438E+02 -0.33540004381E+03  0.35186997544E+03  0.82116958530E+02 0.  0.
  6    2    1    2  501    0 -0.14952840473E+03  0.23999735524E+02 -0.25720865153E+03  0.34516945021E+03  0.17335203433E+03 0.  0.
 24    2    5    5    0    0 -0.16699616992E+03  0.38357854935E+02 -0.25987491067E+03  0.32192128147E+03  0.82093218139E+02 0.  0.
-13    1    6    6    0    0 -0.76026472087E+02  0.53922169130E+02 -0.95737952146E+02  0.13361654188E+03  0.00000000000E+00 0.  1.
 14    1    6    6    0    0 -0.90969697833E+02 -0.15564314195E+02 -0.16413695853E+03  0.18830473960E+03  0.00000000000E+00 0. -1.
  5    1    5    5  501    0  0.17467765185E+02 -0.14358119410E+02  0.26662591415E+01  0.23248168736E+02  0.46999998093E+01 0. -1.
 11    1    4    4    0    0  0.50813684997E+02 -0.61274565657E+02 -0.22556131392E+03  0.23919554619E+03  0.00000000000E+00 0. -1.
-12    1    4    4    0    0  0.59087134026E+01  0.24414494219E+02 -0.10983872989E+03  0.11267442925E+03  0.00000000000E+00 0.  1.
 -5    1    3    3    0  503  0.92806006335E+02  0.12860335914E+02 -0.78847963972E+02  0.12254564240E+03  0.46999998093E+01 0.  1.
</event>
<event>
...
</LesHouchesEvents>

• Extending the LHE format in order to store partons, hadrons and jets (reco objects) in a same file. The generation step (hard-process, shower, reco) will be specified by the status-code. Some details:

• parton level: same conventions than the existing LHE. Example:

6    2    1    2  501    0 -0.14952840473E+03  0.23999735524E+02 -0.25720865153E+03  0.34516945021E+03  0.17335203433E+03 0.  0.

• hadron level: the conventions can be applied without too much change (maybe the meaning of the two ICOLUP variables could be discussed).

2212    2    1    2  501    0 -0.14952840473E+03  0.23999735524E+02 -0.25720865153E+03  0.34516945021E+03  0.17335203433E+03 0.  0.

• reco level: the conventions have to be adapted. We can keep:
  • one line per physics object.
  • ISTUP variable with specific PDG-id for reco objects. Example: 11/-11 for electrons, 13/-13 for muons, 15/-15 for hadronically-decaying taus, 22 for photons, 21 for jets, 12 for MET, -12 for MHT
  • MOTHUP variables linked the reconstructed object to the originated partons (only for some objects). Example: a electron coming from hard-process.
  • PUP variables without change.

Other relevant variables, specific to the nature of the reconstructed objects, must be added.

• Optional substructure in <event> block: defining a XML tag for each collection of reconstructed objects. When detector fast-simulation is applied, several configurations can be applied (for instance for lepton isolation) and several collection of the same object kind can be produced. The <event>-block substructure is designed to handle several collections of a same object kind. Example:

<event>
...

<jets>
...
</jets>
<jets name="substructure John Hopkins algo">
...
</jets>
<electrons>
...
</electrons>
<muons>
...
</muons>
</event>

Warning: If the LHE file supplies several collections of jets, people must obviously use only collection of jets in their analysis.