Detector Files

DETECTOR FILES

They should exist on the current working directory. Their names should correspond to those used in the -det[i] options. Their format depends on the form of their geometrical outline. We support 4 detector outlines: circular, rectangular, slice and ring.

Circular outline accepts all particles within a cone around the central angle, see the example below.
Rectangular detectors have an inplane- and an out-of-plane dimension, and a distance from the target. The inplane direction is taken along the (polar) angle theta, the out-of-plane direction is along the (azimuthal) phi.
Slice is an 'Orange-slice' segment, defined by an interval in polar angle and an interval in azimuthal angle.
Ring is an outine, extending a given (out-of-plane/2) angle above and below the plane specified by the beam and (theta,phi). It also extends a given (inplane/2) angle on both sides of the polar angle theta.
We also support special outlines: blast and piabsbar (for the MIT-Blast detector and the Nikhef-Piabs detector respectively). They are not intended for general use, but if you are interested, send an email.

The angles are defined as in standard polar coordinates, theta is the polar angle between a scatter direction and the beam axis (0<=theta<=180 degrees) and fi is the azimuthal angle of the scatterplane, defined as a positive rotation around the z-axis, starting at the x-axis direction. Although the choice is in principle free, we propagate the convention to choose the x-axis upwards. This places the reaction plane at fi=90 and phi=270 degrees (right and left of the beam resp.) This has the advantage that the theta-fi scatterplots look nicer..

If a particle is exceeding the limits on energy, mass or charge, it will not be detected in this detector. It can then still be detected in another overlapping detector if the number x in the -detx (detname) is higher than the present one.

The triggermode can be +1, then this detector is required to be hit, before either histogram increment or eventmode output takes place. When it is -1, hitting this detector will veto the incrementing and the event-output. If zero, the detector will be included in the outputs, but is not required. With the options trigmulmin and trigmulmax, one can choose to trigger on a (an interval of) smaller number of trigger detectors all with their triggermode=+1, e.g on every double hit for a 3-detector setup, or 3 and 4-folds in a 16-detector setup (yes, this actually occurs for the Nikhef Pion-absorption experiments 1984-1988).

Missing energy versus missing momentum plot is made by subtracting from the beam energy and momentum, the energies and momenta of all detectors that have triggermode=1 (and were hit). Missing Energy versus momentum is only histogrammed when at least one detector is in histogram mode.

The Eres parameter folds the measured kinetic energy with a gaussian with variance (Eres). It only works for histograms now.

We give some detector-file formats in full:

circular
(theta)       central theta in degrees   [0<=theta<=180]
(fi)          central fi in degrees      [0<=fi(360]
(solan)       solid angle  in sterradian [0<=omega<=12.7]
(eta)         efficiency                 [0<=eta<=1]
(Emin)        lower kinetic energy threshold   [MeV]
(Emax)        higher kinetic energy threshold  [MeV]
(Eres)        energy resolution only for histograms  [sigma, MeV]
(mmin) (mmax) min and max mass thresholds for  [MeV/c^2]
(qmin) (qmax) min and max charge thresholds [-1 = electron charge]
(trig)        [-1: veto, 0: out-of-trigger, 1: in trigger]
(mode)        [0: no output, 1: histo, 2: events, 3:histo+events]

rectangular
(theta)             central theta in degrees   [0<=theta<=180]
(fi)                central fi in degrees      [0<=fi(360]
(hor) (ver) (dist)  out- and inplane dimensions and distance from target
(eta)               efficiency                 [0<=eta<=1]
(Emin)              lower kinetic energy threshold   [MeV]
(Emax)              higher kinetic energy threshold  [MeV]
(Eres)              energy resolution only for histograms  [sigma, MeV]
(mmin) (mmax)       min and max mass thresholds for  [MeV/c^2]
(qmin) (qmax)       minimal and maximal charge thresholds
(trig)              [-1: veto, 0: out-of-trigger, 1: in trigger]
(mode)              [0: no output, 1: histo, 2: events, 3:histo+events]

slice
(theta)       central polar angle theta in degrees  [0<=theta<=180]
(fi)          central azimuthal anglefi in degrees  [0<=fi(360]
(inp) (outp)  in- and outplane acceptance angle     [0(inp(180] [0(outp(360]
(eta)         efficiency                            [0<=eta<=1]
(Emin)        lower kinetic energy threshold   [MeV]
(Emax)        higher kinetic energy threshold  [MeV]
(Eres)        energy resolution only for histograms  [sigma, MeV]
(mmin) (mmax) minimal and maximal mass thresholds [MeV/c^2]
(qmin) (qmax) minimal and maximal charge thresholds  [-1 = electron charge]
(trig)        [-1: veto, 0: out-of-trigger, 1: in trigger]
(mode)        [0: no output, 1: histo, 2: events, 3:histo+events]

After this obligatory part, the optional lines may follow specifying non-default lower and upper limits and stepsizes on histograms. The the format for such lines is:

(option) (value)

where the following options are supported:

Tmin       lower limit of kinetic energy   [MeV]
Tmax       upper limit of kinetic energy   [MeV]
Tstep      stepsize of kinetic energy   [MeV]
pmin       lower limit of momentum   [MeV/c]
pmax       upper limit of momentum   [MeV/c]
pstep      stepsize of momentum    [MeV/c]
thmin      lower limit of polar angle theta [degr]
thmax      upper limit of polar angle theta [degr]
thstep     stepsize of polar angle theta   [degr]
phimin     lower limit of azimuthal angle phi [degr]
phimax     upper limit of azimuthal angle phi  [degr]
phistep    stepsize of azimuthal angle pni   [degr]

Defaults for these are generally (too) large.

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JV / 6 Jan 1994