XMLHEP: proposal for a structure of partonic events files

1. Alexandre Sherstnev (SINP MSU) XMLHEP: proposal for a structure of partonic events files Why and where we need events files. XMLlikeHEP: New standard for partonic events storage CPYTH: CompHEP-PYTHIA interface Proposal: XMLPEV LCG Generator Services meeting

2. Why do we need events files? One can transfer the events through events files. Modern complexity of MC generation has resulted in separation of 2 stages of the events generation: ME (CompHEP, etc.) and SH (PYTHIA, etc.) One needs to organize an interface between generators of these stages. II. Collaborations require reliable samples of MC events with proper simulation at parton and particle level. Since MC generation in many cases is a really hard and resources required task,it is better to store the events to files and make manipulations with the data directly, without re-generation. LCG Generator Services meeting

3. Visualization (special utilities and ROOT scripts) Use of the events files Partonic events files SH: PYTHIA, HERWIG, ISAJET. ME: MagGraph,GRACE, CompHEP,… Data manipulation (mixing, updating, applying extra cuts, etc.) LCG Generator Services meeting

4. New data storage standard Text files is optimal for partonic events storage: platform independent, simple I/O, legible. A some standardization is necessary for these events files. Initial specific points for our standard are: A physical information transferred from ME to SH is highly heterogeneous. Our standard has to transfer different types of the information within some uniform syntax. We assume that SH generator or a manipulation utility will take an information transferred which it can interpret and omit the rest of the information. LCG Generator Services meeting

5. Text file for partonic events Description of common physical information for events: beams, processes, QCD info, etc. Event 1 Event 2 … New data storage standard Header of the file Partonic event records LCG Generator Services meeting

6. The format Syntax: a file header Basic unit of information in the header – command Command syntax:command name = command value Command value can be of numerical type or a string (in the latter case the value encloses in quotes). The commands are grouped undertags. Tag syntax: ##Tag name: command 1,…, command N,; Double # – the beginning of the tag semicolon – the end of the tag The header information are stored as a set of tags. The file header are separated from event records by extra semicolon. LCG Generator Services meeting

7. Example of the tags set ##generator: name=‘CompHEP’, version=‘4.2.0’,; ##beam: energy=1.000E+03, KF=2212, name=‘proton', mass=9.380E-01,; ##strfun: name='CTEQ', version='5m1',PDFid=833, PDFgr=11, PDFfile=‘$PDF/cteq5m1.pdf',; ##process: ID=1, name='u D -> E1 n1 b B ', CrosSec=3.69595E-02, CrosSecErr=4.61224E-03, Nparton=6, master=3,; ##n_event: IDprocess=1, N=1000, multN=1, maxW=2.96610E+00,; ##parton: IDprocess=1, in=1, KF=2, name='u', mass=0.00000E+00,; ##parton: IDprocess=1, out=2, KF=11, name=‘n1', mass=0.00000E+00,; ##total:Nprocess=1,CrosSec=3.69595E-02,CrosSecErr=4.61224E-03,Nevent=1000,; ##QCDprocess: IDprocess=1, NL=2, Qnorm=9.11870E+01, QCDalpha=1.18108E-01, file_name='$GEN/c_source/num/alpha_s.c', func_name='alpha_c(int q)',;; LCG Generator Services meeting

8. Event record: CompHEP The event record is intended to store information specific for event: particles momenta, color chain, etc. 1. In the recent version of the standard the event record occupies one line in a data file. The event record consists of some fields divided by colons. Event record example:1: 2.825664E+02:-1.593711E+02: 8.204448E+01:-1.468924E+00: 6.821391E+01:-1.024018E+01: 3.039867E+01: 2.797844E+01:9.119E+01:(1 2)(6 5) 2. For interpretation of event records we use a special tag format. The tag describes a sense/format of event record fields: ##format: IDprocess=5, ProcNumber='i', p1.3='13.6E', p2.3='13.6E', p3.1='13.6E', p3.2='13.6E', p3.3='13.6E', p4.1='13.6E', p4.2='13.6E', p4.3=‘13.6E',Q='10.3E', color_chain=‘string’,; The structure of the event record is under development now. LCG Generator Services meeting

9. Advantages of the standard • The events file standard allows to transfer any information about partonic MC events. • An author of a SH generator can use some standard routines to read and treat just necessary information for his/her generator. If the file contains some extra data the generator does not notice them. • Other immediate advantages are: • Independence from programming language/structure of ME and SH generators. • Readability by users • Simple realization. LCG Generator Services meeting

10. Relations to LH Agreement-I Les Houches Agreement-I defines all necessary information for proper transferring of a MC event from ME to SH by special FORTRAN common blocks. So LH Agreement-I works directly for “on-fly” events transferring. Storing of events in events files is proper solution if we are forced to launch ME and SH generators separately. Our events file standard allows to transfer any information about events. In particular, one can store all necessary information required byLH Agreement-I. However, the standard allows to save and transfer some extra information about events, which the events author wants to save. A SH generator can omit the data if the program maintains just the LH Agreement-I. LCG Generator Services meeting

11. CPYTH-2.0 In the last version of CompHEP-PYTHIA interface package the developed standard has been used. CPYTH contains the interface program itself, R/W routines for our standard on FORTRAN and C, and some utilities to work with the events files. mix_flows in practice, CompHEP generates several events files. Interface delivers events to PYTHIA from one file. The program mixes properly events from some files. Add_cut this program apply extra kinematical cuts on events flow. Information about all applied cuts is stored in the header of the file (under development). LCG Generator Services meeting

12. Toolkit utilities make_table/view_table utilities for creation/ visualization of kinematic distributions. make_table builds a table – a histogram normalized on cross section of the sample. view_table visualizes the table (system is taken from CompHEP).Also we plan to develop some ROOT scripts to visualize the histograms after make_table. Atpresentcpyth-2.0 is ready for testing. Test version of the toolkit can be downloaded from the CompHEP homepage. LCG Generator Services meeting

13. New proposal: XMLPEV In our standard we tried to separate events data themselves and representation of the data. So the standard is related very closely with original conceptions of XML. But usage of XML for whole stored data is not convenient: sizes of events files in XML will become very large. 1st solution of the problem: our standard – XMLlikePEV However, a header of the events files can be stored in original XML syntax, with some sort of compression for event records. Our new proposal: XMLPEV Storage of general information in file header in XML syntax (new R/W utilities will be based on the expat library). Events records are stored in our format but under gzip compression. LCG Generator Services meeting