I. Kreslo, LHEP, Bern

Bern Scanning Laboratory

Hunting muonless interactions...

I. Kreslo, LHEP, Bern

I. Kreslo, LHEP, Bern

NC event 179312944

I. Kreslo, LHEP, Bern

muonless event 179312944 179312944;391;neut;2007-10-06 11:46:34;1;1;W25;R13;C25; 01011847 179312944;391;neut;2007-10-06 11:46:34;1;1;W25;R13;C24; 01011845 179312944;391;neut;2007-10-06 11:46:34;1;1;W25;R13;C26; 01011669 179312944;391;neut;2007-10-06 11:46:34;1;1;W25;R14;C25; 01012865 179312944;391;neut;2007-10-06 11:46:34;1;1;W25;R12;C25; 01008954

3 Bricks are developed

179312944 11847 09/10/07 1 0.22

179312944 11845 09/10/07 1 0.15

179312944 11669 09/10/07 1 0.14

I. Kreslo, LHEP, Bern

CS predictions

First step – standart: 6 prediction are found in CSD, - not found in any of three bricks.

Need for more sophisticated approach…

I. Kreslo, LHEP, Bern

Veto alignment (pl 57 – veto 58)

500 microns

Two alignments !! Veto was moved during exposure.

Is the situation with CSD the same?If yes => Search area=1x1mm

I. Kreslo, LHEP, Bern

Veto dublet deformations

Is the situation with CSD the same?If yes => Angular tolerance ~30 mrad.

I. Kreslo, LHEP, Bern

Pl 57 deformations

Z Distance CSD – P57Error up to 300 microns

I. Kreslo, LHEP, Bern

Full area scan

IP=300 microns, >3-fold-pre-vertexing

“Pre-vertexing” allows to limit number of SB pathes to 75 (~5%)

Emulsions 57,56,55 + CS0,CS1Full area scan

Total number of tracks not found in CSD: about 1300!

(No angular constraints)

I. Kreslo, LHEP, Bern

Scanback of pre-vertexed tracks

Initially 75 tracks, 32 stops, 28 stops to analyse (pl 3-53), 43 passing

No converging stopping tracks…..

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Totalscan around stops

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Visual check : SB path 4248

SB track

Smth. interesting

I. Kreslo, LHEP, Bern

Vertex found

Good vertex ! But there is a sign of incoming track (see prev. slide)

I. Kreslo, LHEP, Bern

Volume scan around vertex

Tracks are visible in veto => This is NOT a neutrino event, but HE cosmics reaction

577748

2938 1211450

I. Kreslo, LHEP, Bern

After scanback of ~1300 tracks two interesting vertices found

I. Kreslo, LHEP, Bern

After scanback of ~1300 tracks two interesting vertices found

I. Kreslo, LHEP, Bern

NC candidate : volume scanNo additional tracks related to vertex are found

2x2cm x 9 plates

I. Kreslo, LHEP, Bern

Check presence of tracks in VD (Veto Dublet)

1st alignment 2nd alignment

Pl 57 Pl 58 Pl 59 Pl 58 Pl 59

662 BT MT(8) - - -

762 BT - - MT(8) -

101 BT BT BT BT -

102 BT BT BT - BT

103 BT MT BT - -

104 BT BT BT - -

201 BT - - BT BT

202 BT BT - BT MT

Confirmed: NOT in VETO !

I. Kreslo, LHEP, Bern

NC candidate 1 : detector view

Hadronic shower CG fit

I. Kreslo, LHEP, Bern

NC candidate 1

Hits in TT correspond to possible interaction=> Likely NC event

I. Kreslo, LHEP, Bern

NC candidate 2 : detector view

I. Kreslo, LHEP, Bern

NC candidate 2

No hits, high IP => unlikely.

I. Kreslo, LHEP, Bern

NC candidates 1,2

Checked presence in the CSD – not found…. .

I. Kreslo, LHEP, Bern

Effect on CR density discussion...

If no CSD predictions found for one of reasons, then:

1300 tracks to follow => Not possible in 24h/brickStrong selection (maybe few% of total) still leads to fake events (3)Reduction of CR density by factor 5 would be very desirable…

I. Kreslo, LHEP, Bern

Predictions from LNGS => Low momentum shower?

• Volume scan 2x2cm 57 plates• VTX reconstruction with IP<50 microns, min Nseg=2:• 5189 2-prong vertices (!)• 86 3-prong (too many to check) (left as the last chance)• 7 4-prong (incoming tracks -> rejected)• 1 5-prong (all 2 seg tracks, high IP – rejected)

• VTX reconstruction with IP<50 microns, min Nseg=5:• 13 2-prong vertices, 2 correlated with prediction: #1 incoming track reconstructed with the gap of 4 plates, #2 incoming track out of volume (re-scanned bigger volume)

I. Kreslo, LHEP, Bern

Summary on the event search

1. Standart prediction search gave no consistent tracks in pl 57,56.2. Volume scan around predicted tracks => Some candidates, rejected for various

reasons.3. Fullarea scan with Veto-in cosmics: 1300 tracks to consider4. Pre-vertexing procedure applied, no converging tracks, however 28 stops. TotalScan

is done visual checks – done. 7-prong CR interaction found, rehearsal of vertex analisys is done on this interaction, all scanning tasks in fully automatic mode.

5. Scanback of all ~1300 tracks from pl57-55, not found in Veto is complete

6. One vertex from external interaction is found and confirmed : - NOT in VETO - YES in TT - NOT in CSD

Extract upstream brick?! Reasonable to say Yes.

Event is not found, but the strategy starts to develop.

I. Kreslo, LHEP, Bern

Prediction location

Location in pl 57DX=1mm

NO FOUND ? YES

Scanback withIC at CG of cluster

NO STOPS ? YES

Totalscan 5x5mmx10pl

1 PRONGS ? >1

Visual check

NO CONFIRMED ? YES

Scanforth to VETO

YES FOUND IN VD ? NO

I. Kreslo, LHEP, Bern

Scenario for muonless event location

NO CS TRACKS ? YES

NO Located ? YES

Prediction location

Volume scan 2x2cm57pl + VETO

around first TT cluster CG

Find all alignmentsErase tracks, present in VD

Pre-vertexing3 prong, IP<300microns

NO Located ? YES

Prediction location

e- Shower searchIn a volume (+VD!)

I. Kreslo, LHEP, Bern

Shower confirmation

Check BT in VETO

YES FOUND IN VD ? NO

Check BT in CSD ?

NO FOUND IN VD ? YES

I. Kreslo, LHEP, Bern

Muonless event location strategy

First picture of the algorithm becomes clear

Worked well for two events so far :

One CR and one neutrino (see next talk by C.Pistillo)

Very time consuming, but very precious (νμCC events,Tau-> e, Tau-h

channels) => firther optimisation (minimisation) is crucial.