General MUON finding in ZEUS using ORANGE

This page was created by Achim Geiser. Last update 2/05/07

Preamble

As illustrated in the high mass dimuon event picture above, muons can be identified in ZEUS from many different subdetectors. The muon momentum is usually measured by the CTD, potentially supplemented by information from the FTD/RTD, and, for post-upgrade data, the MVD and STT. Next, the muon passes the calorimeter, where it leaves a characteristic Minimum Ionizing Particle (MIP) signature. Finally, if its momentum is sufficiently large, the muon traverses the muon spectrometer consisting of inner muon chambers (inner B/RMUON, FMUON for barrel, rear, or forward), the backing calorimeter (BAC), and the outer muon chambers (outer B/R/FMUON). In the very forward region, the FMUON system is extended by an additional spectrometer which allows a standalone muon momentum measurement without the need for a CTD track. For a general introduction, see also the lecture on Muon Finding in ZEUS.

Various different algorithms are available in ZEUS to identify muons. Each of these algorithms typically combines the information from 2 or 3 out of the 4 or more possible subdetectors. In the current orange implementation, the information from all these finders is combined into a single ORANGE ntuple block, GMUON, whose format is essentially independent of the respective finder. The goal was to
• make the results of all muon finders easily available to non-experts.
• increase the muon detection efficiency by allowing an "OR" of all the different finders.
• improve the background rejection by simultaneously providing an "AND" of all possible finder combinations.

  Ideally, at a later stage, the information from all subdetectors might be combined into a single muon finder taking into account all their correlations.

1. The general GMUON implementation

The General MUON finding (GMUON) package in ORANGE is based on a combination of the GLOMU, BREMAT, MAMMA, MPMATCH, MUFO, MIP, MV, and MUBAC muon finders described elsewhere. A rudimentary BAC match and FMUON standalone information based on the MFCTS tables are provided in addition. Further extensions are forseen. It is available from standard release 2003a.2 onwards. The current version is 2005a.1. For potential new test implementations see below.

The algorithm finds prompt muons based on an "OR" of all these packages, and combines the information into a single entry per muon candidate as much as possible. The basic format of this entry is independent of the respective finder. Cross references to more detailed information for each finder and cross-correlations between the different finders are provided. In the case of ambiguities, alternative reconstructions of the same muon are sometimes listed. A muon quality flag is provided which should help the non-expert user to select good quality muon candidates from this list as a starting point for an analysis. Since muon quality is process specific, for critical applications it is recommended that the user redefine his/her own quality criteria based on the information provided.

Feedback on 'features', bugs, missing information and/or possible improvements is greatly appreciated.

2. Description of variables

3. Description of muon-related ORANGE cards

Card          default     description

DOMUON   OFF   enables muon finding in general
DOMUON1   ON   enable old (pre-2003) simple muon finders
DOMUON2   ON   enable new sophisticated muon finders
MUZUFO    OFF   use muons for ZUFO corrections
MUJETA      OFF   calculate Muon association to jet type A
NTMUON    OFF   enable old MUON ntuple block
NTGMUON   OFF    enable new GMUON ntuple block
NTGMUJET   OFF   include muon-jet information into GMUON
NTMUMC     OFF   include muon MC information into GMUON
NTMUQU    2      only store muons with quality flag >= value (not yet implemented)
DOBAC       OFF   enable muon finding based on BAC (J. Sztuk)
NTBAC        OFF   store detailed MUBAC information (J. Sztuk)
NTBREMAT   OFF   store detailed BREMAT information (G. Abbiendi)
NTMPMAT   OFF   store detailed MPMATCH/MFRTZ/MFCTS information (M. Corradi)
NTMV          OFF   store detailed MV information (V. Kuzmin)

In addition there are cards for invidual packages and for GEANE initialization for expert use.
*** For the moment, whenever DOMUON2 is ON, a set of GEANT and BREMAT cards needs to be added. ***
These are needed for the proper functioning of BREMAT, MUFO, and MPMATCH. Solutions to replace this by a default initialization are under study.

Examples for use of cards:

The minimum setting for non-expert users which do not need backwards compatibility with pre-2003 versions of the ntuple is
DOMUON ON
NTGMUON ON
DOBAC ON
add the GEANT and BREMAT cards
set the approriate trigger date for the corresponding year (see GEANT cards)
This will switch on all essential features, and yield a GMUON block containing all the necessary basic information.

If information on muon isolation is wished the card
ORANGE-NTBLOCKS GMU_ISOL
will make this information available in the GMUON block

If information on muon-jet association is wished, and some jet finder is enabled the cards
ORANGE-NTBLOCKS GMU_JET
or NTGMUJET ON
will make this information available in the GMUON block, separately for jet blocks A, B, C, and D.

If simulated true information on muons is wished the card
ORANGE-NTBLOCKS GMU_MC
or NTMUMC ON
will make this information available in the GMUON block

For experts wishing more detailed information, a selection from the cards
NTMUON ON (for GLOMU, MAMMA, MIP)
NTBAC ON
NTBREMAT ON
NTMPMAT ON
NTMV ON
will switch on additional expert blocks from the respective finders

If zufos are enabled, and are to be corrected for the muon mip deposit, the card
MUZUFO ON
should be enabled.

To enable the zufo dead material correction (NOT to be used in conjunction with any other jet corrections), use
ORANGE-ZUFODMCO ON

Be careful with the use of ZUFORMVE ON (electron removal) since this removes all tracks in the vicinity of an electron from the zufo list, even if they belong to a muon! (best solution: DON'T use this flag).

To switch on all (or a selection of) GMUON and related ntuple blocks, you can also use the new NTUPLE BLOCK notation
ORANGE-NTBLOCKS GMUON GMU_ISOL GMU_JET GMU_MC MUON BREMAT FMU_MPM FMUmfrtz MV BAC

For full backwards compatibility with the pre-2003 version of the ntuple (now obsolete!), use
DOMUON ON
DOMUON2 OFF
NTMUON ON
This will switch off all new features, and yield a muon block identical to the old one.

The setting to profit from the new GMUON block, with simultaneous access to the "old" information for backwards compatibility, should be
DOMUON ON
NTMUON ON
NTGMUON ON
DOBAC ON
do not forget to add the GEANT and BREMAT cards

4. How to use the GEANT and BREMAT cards

5. Additional FAQ's

6. Some basic performance numbers and plots

Expected efficiencies and event samples: Numbers do NOT yet include trigger and other selection efficiencies.

Beauty (from small inclusive PYTHIA bbbar sample):
Assume total bbbar cross section of ~10 nb.
-> 10^6 events for 100 pb^-1.
~ 200000 events with >= 1 prompt muon p>1 GeV and pT>0.5 GeV
~ 110000 events with reconstructed muon candidate, muon quality >=4
~ 90000 events with reconstructed prompt muon, muon quality >=4
~ 30000 events with rec. prompt muon qual>=4 ass. to jet pt>4 GeV (ptrel)
~ 2400 events with rec. prompt muon 5dof + 2 jets pt>6,7 GeV +p/pt cut

Beauty -> D*+muon: Selection with muon quality >= 4 doubles event sample (currently from BREMAT 4dof only) while keeping same signal/bg ratio.

W->munu: Either significant increase in efficiency (~30%) for similar purity, or significant increase in purity for same efficiency (=> loosen other cuts?).

7. Acknowledgements