Welcome to the E687 event display directory page

This directory contains a list of event display pictures of interesting E687 events. These pictures where produced by PRAVDA (Pattern Recongition Analysis Via Display Aid) the official interactive E687 event display.

For each picture there are both a POSTSCRIPT and a GIF version: to get a quick snapshot (with XV for e.g.) click on GIF version. To get instead the best results fetch the POSTCRIPT version and print it on a color printer.

In addition to that, each POSTSCRIPT picture comes in two flavors:

Choose one according to where you are

1) Charm-charmbar event (2970_45_2636) (microvertex)

(POSTSCRIPT version, A4)

(POSTSCRIPT version, US letter)

(GIF version)

A (D0bar -> K+pi-) + (D0 -> K-pi-pi+pi+) event fully reconstructed; the microvertex detector is displayed along with the reconstructed tracks and vertices.

The green box represents the Beryllium target; for the twelve Silicon strip detectors only the active region profile is displayed. The photon beam (for this event the measured photon energy was 246.4 GeV/c^2) enters from the left; the first vertex on the left is therefore assumed to be the primary vertex, the vertex in the middle is the D0bar candidate and the rightmost vertex is the D0 candidate.

The reconstructed decay path (L) divided by its error (sigma) is shown for each candidate. The D/sigma is the reconstructed impact parameter, divided by its error, of the D meson tri-momentum computed at the primary vertex location on a plane transverse to the incoming photon direction; it indicates how well the reconstructed flight direction of the D meson points back to the production vertex.

The rules at the bottom of the picture are expressed in cm

2) Charm-charmbar event (2970_45_2636) (microvertex detail, real cool)

(POSTSCRIPT version, A4)

(POSTSCRIPT version, US letter)

(GIF version)

This is an enlarged detail of the same event in the microvertex region: the yellow ellipses around each vertex indicate the 68% confidence level of the fit (corresponding to one sigma)

3) Charm-charmbar event (2970_45_2636) (spectrometer, non-bend projection)

(POSTSCRIPT version, A4)

(POSTSCRIPT version, US Letter)

(GIF version)

Same event but shown trough the entire E687 spectrometer in the non-bend projection.

The two analysis magnets (M1 and M2) are shown with the five multiwire chambers (P1 to P6), the three threshold Cerenkov counters (C1, C2 and C3), the outer and inner electromagnetic calorimeters (OE and IE), the hadron calorimeter (HC) and the inner/outer muon counters (Om and Im).

4) Charm-charmbar event (2970_45_2636) (spectrometer, bend projection)

(POSTSCRIPT version, A4)

(POSTSCRIPT version, US letter)

(GIF version)

Same event but shown trough the entire E687 spectrometer in the bend projection. Opposite charged particles are bent in opposite directions at the middle of the two analysis magnets.

5) Charm-charmbar event (2970_45_2636) (detail of the microvertex-spectrometer matching region)

(POSTSCRIPT version, A4)

(POSTSCRIPT version, US letter)

(GIF version)

This picture shows a detail of the matching between microvertex reconstructed tracks and spectrometer reconstructed tracks; tracks marked in red are non-matched ones (tracks 10 and 11).

6) Charm-charmbar event (2961_82_324) (microvertex)

(POSTSCRIPT version, A4)

(POSTSCRIPT version, US letter)

(GIF version)

A (D0 -> K-pi+) + (D0bar -> K+pi+pi-pi-) event fully reconstructed (see comments of picture 1).

7) Charm-charmbar event (2961_82_324) (microvertex detail)

(POSTSCRIPT version, A4)

(POSTSCRIPT version, US letter)

(GIF version)

An enlarged detail of the decay region is shown.

There is a track (9) which is not matched by the spectrometer and is not associated to any vertex.

The horizontal black line at the middle of the green region (the Beryllium target) simply indicates the lateral edge of the target as seen from the current projection. The decay of the D0bar candidate occurs in vacuum outside the target.

8) Charm-charmbar event (2961_82_324) (spectrometer, bend-projection)

(POSTSCRIPT version, A4)

(POSTSCRIPT version, US letter)

(GIF version)

See comments of picture 3 and 4

9) Charm-charmbar event (2961_82_324) (detail of microvertex-spectrometer matching region)

(POSTSCRIPT version, A4)

(POSTSCRIPT version, US letter)

(GIF version)

See comments of picture 5