NUCLEAR FRAGMENT SEARCH IN HADRON INTERACTIONS JIRO KAWADA(LHEP, BERN) ANIS BEN DHAHBI (F.S.T *, LHEP) JONAS KNUESEL (LHEP) * Faculty Science of Tunis

 Nuclear fragments are a clear proof of hadron interaction  Quantifying the fragment finding rate from hadron interaction is important. 2

 The knowledge of the nuclear fragment from hadron interaction with lead is “poor”. Nuclear fragment: proton and alpha particle is dominant energy range ～ 100MeV 3

IMAGE ANALYSIS TOOL -Offline analysis ( search tracks, measure track angles…… ) - Connect several views into one view ( for large angle track search ) 4

5 Fogger.exe, Salerno developed and used in GS scanning lab Added some functions: - Multi view data taking - Coordinations transfer (stage -> OPERA film) Image Data taking tool Fogger.exe 1 view Viewer Data taking separately Analysis

6 Angle Measurement of Image Analysis Tool 6 Difference of measurements between image analysis and European scanning system

FRAGMENT SEARCH FOR OPERA EVENTS HADRON INTERACTION 7 Brick IDHadron int. plate Depth [um] sideviewsNumber off ragments and the slopes(tan.) Up251 (0.55, 0.77) Down252 (0.92, 0.56),(0.75,-0.92) Up250 Down (1) UpNot yet0 Down251(-2.5, -1.8) 22777(1) Up255 Down250 Depth from down surface of lead plate

8 Example(hadron interaction in OPERA Event) -5 fragment tracks have been found in the view microns from emulsion surface 1.8mm 1.3mm

HADRON INTERACTION TEST BRICK (BERN) 8GeV/c Pion θ = (0.041, ) density 10 pions / cm 2  90 events Number of prongs 1 example 9

21 ev: both sides have been analysed 12 ev: Skipped (int. in base, bad surface, single stop) 19 ev: only one side has been analysed 38 ev: Not yet Data taking is on going Statistics of Test Brick 10

ACCEPTANCE [micron] depth 49views 25views 9views 1.0 = 4π[sr] mm x 2.1mm

RESULTS (1) - THE NUMBER OF FOUND FRAGMENTS- Both sides events : 21 Single side events : 19 Number of fragments Both side events : 21 ev No fragments : 5 ev Finding rate  76 % 12

1 Example 726 microns 6 fragments at up, 3 fragment at down 13

I.P. VS RANGE IN LEAD range I.P. Range in Lead [μm] I.P. [μm] 14

RESULTS (2) - ANGLE DISTRIBUTION- Backward : 59 fragments Forward : 40 fragments With taking into account the acceptance backward / forward ratio = 1.32 ± 0.35(stat.) 15

RESULTS (3) -FRAGMENT FOUND RATE- Acceptance(1.0=4πsr) Depth in Lead[microns] Event basePlate base Single side event 16 The rate, at least 1 fragment attached to the VTX found

Summary Systematic fragments search is needed for decay search. Fragment search by image analysis has been done for 40 hadron interactions. The finding rate is high as expected. (around 80%) Increasing the statistics will be done soon and reported. 17

Proposal This analysis for a previous tau candidate. Another test brick, 2GeV, 4GeV, 10GeV should be done. 18

FOUND RATE FOR PRONGS 19 prongsFoundNot found >=360