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Introduction

This note describes how to read the BABAR mini using the Beta interface. Analysis modules developed for a micro based analysis can be incorporated into a mini-based analysis with essentially no change.

When the mini is read, different levels of data processing may be performed. These ``levels of detail'' are described in Table 1 and are referred to as ``micro'', ``cache'', ``extend'',``refit'' and ``rebuild''. These levels of detail are a tradeoff between speed and accuracy. Lower levels of detail will provide more approximate quantities but the job will run faster, while higher levels of detail will provide more exact quantities, but the job will run slower. Two other modes, ``oldmicro'' and ``repair'', are special-use modes not generally relevant for those doing standard data analysis.

Table 1: Levels of detail.

Level of detail	Meaning	Follow changes in alignment and calibration constants	Range of validity
micro	Returns the Kalman track fit estimate of the helical track parameters at the point of closest approach (POCA) to the z-axis for the default mass hypothesis only	No	Inside the beam pipe only.
cache	Returns the Kalman track fit estimate of the helical track parameters for $e$, $\mu$, $\pi$, $K$, or proton mass hypotheses at POCA.	No	Inside the vacuum chamber for all mass hypotheses and at the outer radius/endplate of the DCH for the most likely mass hypothesis as determined by PID
extend	Extend cached results away from the POCA, accounting for material, magnetic field inhomogeneity, etc. Currently, this mode is implemented only for tracking	No	Everywhere in the detector except between the first and last hit
refit	Returns the result of a full Kalman track refit using low-level detector information (hits).	Yes	Everywhere inside the tracking volume.
rebuild	Redoes the pattern recognition from the (subset) of digi/hit level data stored on the Mini.	Yes	Everywhere inside the tracking volume.

micro mode on the mini essentially emulates the level of detail present on the micro itself. In this mode, the fitted track parameters at the point of closest approach (POCA) to the z-axis are available for the pion mass hypothesis only. This mode is mainly used for comparisons between the mini and the micro. In cache mode, the BtaCandidate has access to up to 5 different Kalman track fit mass hypotheses rather than just the pion mass hypothesis. Thus, when the BtaCandidate particle type is changed from a pion to a kaon using one of the methods

 
  BtaCandidate::setType(const PdtEntry* pdt)
  BtaCandidate::setType(const char* name)

the underlying Kalman track fit is changed from ``default'' (the inital setting) to kaon, in addition to changing the mass in the BtaCandidate. Compared with the micro, cache mode will provide an improved estimate of the invariant mass of systems decaying into kaons inside the beampipe, such as neutral D's.

In extend mode, the Kalman fit results are extended away from the POCA accounting for the effect of material and magnetic field inhomogeneity. This mode is used in studies where tracks are expected to originate outside the beampipe, such as those from K-shorts.

In refit mode, the full Kalman fit will be redone, using the cached hit information and the calibration and alignment constants from the conditions database. This mode could be used to see what effect a new SVT alignment might have on a particular analysis.