Support to the event location in

CS Scanning Station

Fabio Pupilli

LNGS Scanning Team

OPERA Collaboration Meeting 20/01/2009

MIZUNAMI

Analysis types in CS Scanning Station

1. Two basetrack search (STANDARD)

2. In case the event is not located: (MICRO)– Compton alignment– ¾ search

3. Support to labs when the event is not localized in ECC (ON_REQUEST)– Compton alignment (useful also to “confirm” already validated tracks)– ¾ search

If nothing new found:• ReScan• ¾ search on ReScan

This talk’s subject

Report on about 1 month of activity on this topic

The Compton alignment: maps

The software (developed by Valeri) compute the x-y offsets between the 2 CSd sheets in order to maximise the number of Compton electron track coincidence. The alignment is performed locally, sampling the scanned area with small zones:

• 2 different set of parameters:

old CSd (brick number <100000) zone dimension ~ 1 cm2

new CSd (brick number >100000) zone dimension ~ 2.6 cm2

The offset of the “wrong” zone is corrected a posteriori averaging the nearest zone offsets.

No good map: it is impossible to identify a continuity map. - To be re-processed with different parameter set- Software improvements

The Compton alignment: maps

Analysis procedure

i) Compton map ii) new link between CS1 and CS2

PositionTolerance = 8 μm (both for double base-tracks and 3 out of 4) [in STANDARD analysis 40 μm, bg reduction by a factor 25]SlopeTolerance = 10 mrad (double base-track )SlopeTolerance = 50 mrad (3 out of 4) MinGrainSum = 36 (double base-track ) MinGrainSum = 30 (3 out of 4)

iii) manual check iv) analysis of the result

LAB requests arrived (last month)

30 support requests from European Labs arrived at LNGS

• None of the CS tracks connected in brick: 9

• At least one CS track connected, but event not localized: 18

• Check on Scan Forth (SF) tracks to validate the event: 3

Results

• Problematic Compton Maps (waiting for sw improvements): 3

I. high fog doublets: 2

II. crash during processing: 1

• Still under analysis: 10

• Completed: 17

I. New tracks published or SF track confirmed: 14

Feedback (3 events localized, 3 SF mu confirmed, 1 event with new tracks connected)

II. Second brick extraction request: 2

III. No new tracks: 1

Problematic Compton Maps (High Fog doublets)

Completed – 2° brick extractionEvent 228342297 (NC) - Brick 124811

STANDARD analysis:

2 CS candidates not connected in the brick

Completed – 2° brick extractionEvent 228342297 (NC) - Brick 124811

ON_REQUEST analysis:

1. ComptonMap confirms only one of the candidates previously validated (but marginal in X, projection on pl57 @ ~ 800 μm from the edge)

2. No new tracks found

Requested extraction of adjacent brick in X

(124810)

Completed – 2° brick extractionEvent 234365353 (NC) - Brick 45758

STANDARD analysis:

1 CS candidate not connected in the brick

ON_REQUEST analysis:

1. ComptonMap confirms the already validated candidate

2. No new tracks found

Requested extraction of second brick (40288)

Completed – Event locatedEvent 237894293 (CC) - Brick 133398

STANDARD analysis:

4 CS candidates connected in the brick:

• Track 2 was a passing-through track (rock μ);

• The other tracks stop after few plates

Completed – Event locatedEvent 237894293 (CC) - Brick 133398

ON_REQUEST analysis:

1. ComptonMap confirms all candidates previously validated

2. A mu candidate (ID 11) recovered with ¾ analysis

Event located, track 11 is the muon

Completed – Event locatedEvent 227165825 (CC) - Brick 119237

STANDARD analysis:

No double bt found in CSd

MICRO analysis:

one CS candidate found but not connected in the brick

Completed – Event locatedEvent 227165825 (CC) - Brick 119237

Since the only track validated on CS came from a ¾ analysis, the first step of ON_REQUEST analysis was a ReScan and… Surprise!

Found 6 confirmed double bt (including a mu candidate, ID 2) from ReScan

Completed – Event locatedEvent 227165825 (CC) - Brick 119237

It’s difficult to explain a null result on first scanning, when the second scanning has measured 6 double bt (5 in the previously scanned area), only by scanning inefficiency.

But take a look at first scanning’s Compton Map:

Large offsets, in most zones more than 40 μm

Marks measurement error?

Why after Compton alignment we cannot recover tracks?

……

Under careful investigation

Completed – Event locatedEvent 227165825 (CC) - Brick 119237

All tracks have been connected in the brick

Event located, track 2 is the muon

Conclusions

• Support activity to Lab requests in LNGS Scanning Station is on going intensively

• The time dedicated to each request is affected by the heavy load of manual checks required especially for ¾ analysis, to be performed in parallel to the ones needed for STANDARD analysis

• Waiting for other feedbacks from Labs