Charm Analysis in the OPERA Experiment Oscillation Project with Emulsion Tracking Apparatus

Charm Analysis in the OPERA Experiment Oscillation Project with Emulsion tRacking Apparatus

PhD student seminar 2009 in Zurich 04.06.2009 Thomas Strauss, ETH Zürich, Group A. Rubbia

Direct search for the νμ→ντ oscillation by looking for the appearance of ντ in a pure νμ beam

Collaboration: Belgium (IIHE(ULB-VUB) Brussels), Bulgaria (Sofia University), China (IHEP Beijing Shandong University), Croatia (Zagreb University), France (LAPP Annecy, IPNL Lyon, LAL Orsay, IPHC Strasbourg), Germany (Berlin Humboldt University, Hagen, Hamburg University, Münster University, Rostock University), Israel (Technion Haifa), Italy (Bari, Bologna, LNF Frascati, L’Aquila, LNGS, Naples, Padova, Rome, Salerno), Japan (Aichi, Toho, Kobe, Nagoya, Utsunomiya), Russia (INR Moscow, ITEP Moscow, JINR Dubna, Obninsk), Switzerland (Bern, Neuchâtel, Zürich), Tunisia (Tunis University), Turkey (METU Ankara) Outline

– Physics Introduction – The Cern Neutrino to Gran Sasso beamline (CNGS) – The OPERA detector – ECC Analysis – Charm Analysis – Summary Physics Introduction

• Neutrino was postulated in 1930 by Pauli to „save“ the energy conservation law and angular momentum in β-decay, and was finally found by Cowan and Reines (1956) • Puzzling results 2-flavour Oscillation Mechanism introduced – Homestake Mine Solar neutrinos

Observed deficit νe −> νx – Superkamiokande Atmospheric neutrinos ⎛ υ ⎞ ⎛υ ⎞ ⎜ e ⎟ ⎜ 1 ⎟ Observed deficit νμ −> νx ⎜υ μ ⎟ = U ⎜υ 2 ⎟ ⎜ ⎟ ⎜ ⎟ ⎝υ τ ⎠ ⎝υ 3 ⎠ iδ iα1 2/ ⎡ 12 coscos θθ13 12 cossin θθ13 sinθ13e ⎤ ⎡e 00 ⎤

⎢ iδ iδ ⎥ ⎢ iα2 2/ ⎥ U ⎢−= 12 23 − 12 23 sinsincoscossin θθθθθ13e 12 23 − 12 23 sinsinsincoscos θθθθθ13e 23 cossin θθ13 ⎥ × ⎢ 0 e 0⎥ ⎢ iδ iδ ⎥ ⎢ ⎥ ⎣ 12 23 − 12 23 sincoscossinsin θθθθθ13e − 12 23 − 12 23 sincossinsincos 13e 23 coscos θθθθθθθ13 ⎦ ⎣ 100 ⎦

– phase α1 and α2 areonlynon-zeroincaseofmajorana particles Neutrinos have a mass !! – phase δ is non-zero only in case of CP violation – If U is not an unitary matrix new physics needed – L, E can be choosen that one transition dominates The Cern Neutrino to Gran Sasso beamline (CNGS)

• 400 GeV/c protons from SPS are directed on a carbon target • From SPS supercycle 6 spills with 2x1013 p.o.t. each are extracted to CNGS beamline • CNGS beamline with target and decay tunnel is directed ~3° downwards in direction of Gran Sasso (in Italy) • Optimized for τ appearance Δp~2% 2 (σ~E, Δposci~sin (1/E) ) The OPERA detector ν SM1 SM2

20 m Veto Target tracker Spectrometer: BMS XPC, HPT, RPC, magnet The OPERA detector - ECC • The τ detection requires high resolution detector (μm) → nuclear emulsions • To get sufficent number of interactions one needs large target mass → lead • The Solution: The Emulsion Cloud Chamber or the OPERA BRICK • alternating emulsion films with lead layer (56 Pb sheets (1mm) + 57 emulsion layers (2x44 μm emulsion coated on a 205 μm plastic base) • 2 additional emulsion layers (Changeable Sheet CS) are attatched on downstream side of each brick to confirm tracks predicted by the TT without the need to open the ECC • weight 8.3kg per brick, in TOTAL ~150’000 bricks → target mass: ~1.3 ktons 10.3 cm Electronic detector to find candidate brick 7.5 cm

=10 X0 Brick wall

12.8 cm Track reconstruction in emulsion

Reconstruction of tracks by scanning of emulsions with microscopes

A microtrack is sequence of aligned grains in a single emulsion layer (average residuals of grains from microtrack fit: 0.066 μm) Plate-to-plate alignment by high- energetic passing-through tracks

A basetrack is the result of the connection of two microtracks on opposite sides of a plate l Precisision of 0.3±0.7 μm for reconstructed tracks

Topological analysis of interactions is possible to Top view Side view search for nonambiguous ντ appearance signature and charm decays δt, δl Automated emulsion analysis

Swiss Scanning Station (Bern)

Emulsion scanning is performed in an automatized way. About 40 microscopes are operational in the various OPERA scanning laboratories around Europe and Japan. The LHEP institute of Bern University hosts the Swiss Scanning Station equipped with 5 microscopes and automatic plate changing robots. About 10 physicists from Bern and Zurich are involved in the operations of the station including scanning, reconstruction and analysis. About 20% of the bricks extracted from the OPERA detector will be analyzed in Bern

2 cm Strategy for event analysis

2.5 m

hadron Predictions from electronic detectors (precision ~cm) are located in the CS (precision ~ µm) and followed back inside the brick 2 mm until tracks stop (scanback). Then muon a full scanning around neutrino interaction vertex is performed and the event topology and 2 cm kinematics reconstructed. τ decay signature (c ττ= 87 μm)

τ decay modes − Detection of the ν appearance signal μ ντ νμ B. R. ~ 17% τ

h- ν n(πο) B. R. ~ 50% τ μ- - e ν ν B. R. ~ 18% τ e νμ + - - ο π π π ντ n(π ) B. R. ~ 14% νμ

Decay “kink” ν μ- νμ τ- 10.2cm oscillation ντ 12.5cm ~1 mm Emulsion analysis topics include: Total emulsion area 130 000 m² Vertex, decay kink, e/γ ID, multiple scattering, kinematics Backgound processes in the OPERA- experiment ν μ ν μ,e- Primary lepton not identified, μ μ,e wrong charge for secondary Coulomb large angle μ+ Charm production in CC, scattering of muons in lead D+ e+ common to the 3 channels Background to τ → μ Same decay h+ (similar lifetime and mass) topology as τ Good μ charge and momentum identification is fundamental to reduce background Hadronic interactions νμ in Pb: Bck. to τ → h Expected number of νμ or to τ → μ background events h (if hadron mis-c after 5 years running h identified as muon) with nominal beam:

Will be recalculated τ→e τ→μτ→h τ→3h Total Charm background .173 .008 .134 .181 .496 Large angle μ scattering .096 .096 Hadronic background .077 .095 . .172 Total per channel .173 .181 .229 .181 .764 Expected event rates

19 target mass 1.25 kton, 5 CNGS-years of 4.5 x10 pot, ~17 GeV

# of Events in target event category

24‘000 νμ-events NC+CC

18‘460 CC events only σNC/σCC = 0.3 H.Shibuya et al, Letter of Intent: The OPERA emulsion detector for a long-baseline neutrino-oscillation experiment " (‘97)

808 ± 55 Charm events: σc/σCC = (4.38 ± 0.3)% Newest Chorus Result, not published yet

0 0 + + + 365 ± 24 D Ratios of D , D , DS , ΛC 443 ± 30 C+ Newest Chorus Result, not published yet

115 ντ - CC events Δm = 2.5 x 10-3 eV2 10.4 reconstructed τ events (efficency ~ 9.1%) Charm in Opera The Opera experiment will observe ~20’000 CC events after 5 years running, with ~1000 produced charm events (not reconstructed). Thus it cannot compete with results from the CHORUS experiment (200’000 CC events, ~2000 found and analysed charm events). But With the prediction from CHORUS data, we can prove that we understand the detector and its efficiencies for charm events. Thus we show that the detection strategy for τ events in OPERA is correct and that we understand the background. ν−induced charm production

Charmed hadron fractions have to be known to reweight the MC Data sample and to confirm the detection efficency estimation Branching ratios are extrapolated to CNGS mean energy of 17GeV from CHORUS data, thus large uncertanties.

Additional physical questions (after experiment) • Measuring effective charm mass from energy spectra fD+ = (21.7±3.4)% of events and CKM matrix elements |Vcd| (cabibbo supressed) and |Vcs| (cabibbo allowed) fD0 = (43.8±3.0)% • Measure the strangeness content of the nucleon f = (25.3±4.9)% • Constrain/study charm production models Λc+ – Branching fractions poorly known, changed a lot this f = (9.2±3.8)% year Ds+ – MC fragmentation models can be improved Charm Single-Basetrack-Search Strategy: Motivation: 10% of all charged charm events, check can be done online from real data or with data from OPERA DataBase • Search primary muon to find the primary vertex • Search all Single-Basetracks within a volume of interest around the primary interaction (500x500x2500μm) • Probe if this Single-Basetrack can be attatched to the vertex with an Impactparameter smaller than 25 micron • Search for decay vertex/track to be attatched to THIS single basetrack (IP 200μm, 0.005mrad) • If candidate found, check if charm candidate Charm Single-Basetrack-Search Strategy: •To distinguish τ, charm or BG events one need cuts on kink angle, momentum, angle in transverse plane and transverse momentum etc…

μ-

neutrino direction

Charm

Angle c/μ in transverse plane (CHORUS)

OPERA MC charm data red, BG blue Other MC studies to optimize analysis for upcomming run Decay length

Decay will be mostly within 5 plates of primary vertex (red line)

D+ D0

µm µm

+ Λ + DS c

µm µm

17 Spatial angle to z-axis of the primary muon

Spatial angle of the muon ~0.2 rad, within scanning acceptance (0.6mrad)

D+ D0

+ Λ + DS c

18 Impact parameter wrt primary interaction Approach for secondary decay search

µm µm

GeV GeV • D0 charm sample • numu-CC sample

For particles with momentum LARGER than 1 GeV an impact paramter of more than 10 μm gives a strong hint for secondary interaction → re-check of “old” Events, 3 new charm candidates found

19 Strategy for 2009 • From energy spectra mostly bricks with muon energy below 25 Gev are likely to contain charm candidates (keep 95% of all charm, but reduce scanning load) • For charged charm spatial angle of muon mostly below 0.4 rad (keep 95% of all charm, but reduce scanning load) • Improve the detailed analysis of primary vertex by scanning lab – Tracks with a large impact parameter (>10) are a hint for secondary interactions, re-calculate IP without track and matching of larger IP tracks to crosscheck for a secondary vertex, momentum measurement, also check for shower (Π0decay) • Scanning area 7 plates downstream primary vertex is needed to detect most of all charm events, more plates required to reconstruct kinematics of charm decay, additional plates scanned for shower search. Scan-Forth of all tracks is done to search for secondary interactions in order to estimate BG from nucluon scattering

20 EFFICIENCY

Trigger 99.9%Review of Charm Production 2008 Brick Finding 70-80% Geometry 96.5% •VertexNumber localisation of events 85-90% in bricks 1690, i.e. 1190 CC Muon– requestedBased on work80-90% of Beam Working Group Decay category Longσ(D ~50%,0)/σ(CC)=(1.91±0.13)% short ~50% neutral charm σ(C+)/σ(CC)=(2.47±0.22)% charged charm Charm candidate selection InclusiveMuon energy charm > 1production Gev, primary at vertexOPERA in plateenergy 56 or lower 88% of all charm events (from MC) σReconstruction(Charm)/σ(CC)=(4.38±0.26)% efficency Not included ~ 52.1±3.6yet, O(75%) Events

Overall ~44% ->0 22.9±1.6 Charm Events are expected+ to be found in 2008 data. So far ~500 events areND localozed=22.7±1.5 and 7 candidate events areNC found=29.4±2.0 in the whole collaboration.

Bern Data Ncontainsfully neutrals 25%3±1 of European events, i.e. 12.5% of whole collaboration, so expected to find in data set are roughly one neutral and one charged charm… N1p=19±2 N2p 16±2 2 Candidates found, neutral already confirmed and accepted asN charm,3p=10±1 the other one is expected to be confirmedN4p soon, right now3.3±0.3 measurement of downstream bricks for momentum estimation going on. 0 + ND =10.0±0.6 NC =12.9±0.9

Nfully neutrals 1.3±0.4 N1p=8.4±0.9 N2p 7±0.9 N3p=4.4±0.4 N4p 1.5±0.1 Neutral charm candidate Brick 72853 Track 145 muon – Energy 17.1 GeV (eldet)/13.9 GeV – TX,TY (-.000,0.030) Track 145 – Energy 1.68-0.44+0.95 GeV – TX,TY (0.356,0.156) Track 206 – Energy 1.32-0.35+0.74 GeV – TX,TY (-0.281,-0.242) Energy of D0 for – Pion Kaon 1.26+0.52-0.23 GeV – Kaon Pion 1.30+0.52-0.22 GeV – Pion Pion 1.09+0.58-0.27 GeV – Below D0 (1.864GeV), but from topology obviously neutrals missing minimum distance w.r.t. mu id 1 * id10 dmin = 2.4 um at 888.1 um upstream from pl 33 id 1 * id 2 dmin = 2.5 um at 1058.3 um upstream from pl 33 Chargedid 1 * id 3 dmin = 31.9 um atcharm 407.0 um upstream fromcandidate pl 33 Brick 79117 id 1 * id 8 dmin = 6.1 um at 894.2 um upstream from pl 33 id 1 * id 5 dmin = 9.0 um at 878.6 um upstream from pl 33 ------(id 1,10,2,3 used for IP analysis because id 8,5 not reconstructed due to large scattering.) hypothesis(1) 1ry vertex + short vee (daughters: id 3 and id 2) 1ry (103979.1 45758.9 -32325.8) dz= 888-150 id 1 103951.0 45839.7 -31437.7 -0.0318 0.0911 IP wrt 1ry = 0.2 id10 104155.2 46009.8 -31437.7 0.1998 0.2805 IP wrt 1ry = 2.2 (id 8 104287.8 45697.6 -31437.7 0.3420 -0.0740 IP wrt 1ry = 6.5 not used to calc 1ry position) (id 5 103832.5 45776.8 -31437.7 -0.1709 0.0289 IP wrt 1ry = 9.3 not used to calc 1ry position) short vee (103933.6 45782.1 -31727.2) dz= 290-150 parent (-0.0760, 0.0388) id 2 103914.0 45797.6 -31437.7 -0.0685 0.0530 IP wrt vee = 0.3 IP wrt 1ry = 9.5 id 3 103934.5 45744.0 -31437.7 0.0050 -0.1310 IP wrt vee = 0.6 IP wrt 1ry =111.9 hypothesis(2) 1ry vertex + short kink (daughter: id 3) 1ry (103978.4 45751.5 -32363.2) id 1 103951.0 45839.7 -31437.7 -0.0318 0.0911 IP wrt 1ry = 4.3 id10 104155.2 46009.8 -31437.7 0.1998 0.2805 IP wrt 1ry = 8.0 id 2 103914.0 45797.6 -31437.7 -0.0685 0.0530 IP wrt 1ry = 3.2 (id 8 104287.8 45697.6 -31437.7 0.3420 -0.0740 IP wrt 1ry = 15.8 not used to calc 1ry position) (id 5 103832.5 45776.8 -31437.7 -0.1709 0.0289 IP wrt 1ry = 12.3 not used to calc 1ry position) short kink daughter id 3 103934.5 45744.0 -31437.7 0.0050 -0.1310 IP wrt 1ry =122.7 Minimum kink angle = 0.158 ------momentum measurement (preliminary) id 1 -0.0318 0.0911 p pmin pmax = 38.26 28.46 1000000.00 GeV/c (90%CL) (run300,p33-56) id10 0.1999 0.2805 p pmin pmax = 4.00 2.33 14.38 GeV/c (90%CL) (run300,p33-56) id 2 -0.0685 0.0529 p pmin pmax = 8.77 5.52 21.42 GeV/c (90%CL) (run300,p33-53) id 3 0.0050 -0.1310 p pmin pmax = 5.52 3.78 10.20 GeV/c (90%CL) (run300,p33-56) id 5 -0.1709 0.0289 p pmin pmax = 0.41 0.25 1.25 GeV/c (90%CL) (p33,36,38,39) id 8 0.3420 -0.0740 gray, not reconstructed ------mass K -K : 1.7 (+1.4 -0.4) GeV pi-K : 1.6 (+1.5 -0.4) GeV pi-pi : 1.4 (+1.5 -0.5) GeV K -pi : 1.5 (+1.5 -0.4) GeV Summary

• The Opera Detector is the first νμ → ντ appearance experiment. • Charm production and decays in deep inelastic neutrino scattering is a background to the tau search. However, it can be used to evaluate experimentally the efficiency to find and reconstruct decays of short-lived particle in OPERA. • The charm neutrino-events of this year are partly found (due to different strategies in Europe and Japan) and ongoing scanning and analysis, after reporting the missing events in march. • So far the main effort was in scanning and data production,, now we begin to focus on analysis. • 2009 run started on this week on Tuesday. Backup Slides… • Emulsion efficency • Physic motivation Opera • LNGS • CNGS • Detector • Last October Run Emulsion Resolution

momentum resolution vs track span (MC at 0°) track finding efficency (by angle)

scattering angle evolution vs lead thickness in mm (ncell)reconstructed momentum vs MC or beam momentum for data and MC Pions, Kaons, Electrons and Mu+

Signal hidden in bg… Pions, Electrons, Kaons and Protons Status of the experiment

May 2006: completion of electronic detectors commissioning Aug 2006: technical run, 0.76*1018 pot collected 319 interactions in the rock, mechanical structure and iron of the spectrometer Oct 2006: start of brick production 1 year CNGS nominal 4.5*1019 pot

Oct 2007: short physics run (~40% target) 0.82*1018 pot collected first 38 neutrino events collected in the target

Jun 2008: End of brick filling, OPERA detector fully commissioned, 146000 bricks inserted Jun 2008: Start of the first OPERA physics run Sep 2008: 5.6*1018 pot and ~500 neutrino events collected Physics Introduction

• Neutrino was postulated in 1930 by Pauli to „save“ the energy conservation law and angular momentum in β- decay, and was finally found by Cowan and Reines (1956) • Puzzling results – Homestake Mine Solar neutrinos

Observed deficit νe −> νx – Superkamiokande Atmospheric neutrinos E = 1 GeV

Observed deficit νμ −> νx 2-flavour Oscillation Mechanism introduced

Neutrinos have a mass !! km Physics Introduction

• Oscillation is the first proof for physics beyond the Standard Model – Neutrinos have a mass, thus they interact with the Higgs field – Either right handed neutrinos exists (Dirac mass) – Or lepton number violation occurs (Majorana mass) and more than 1 phase possible • Introduction of Oscillation Mechanism ⎛ υ ⎞ ⎛υ ⎞ ⎜ e ⎟ ⎜ 1 ⎟ ⎜υ μ ⎟ = U ⎜υ 2 ⎟ ⎜ ⎟ ⎜ ⎟ ⎝υ τ ⎠ ⎝υ 3 ⎠ iδ iα1 2/ ⎡ 12 coscos θθ13 12 cossin θθ13 sinθ13e ⎤ ⎡e 00 ⎤

– phase α1 and α2 are only non-zero in case of majorana particles – phase δ is non-zero only in case of CP violation – If U is not an unitary matrix new physics needed • Solar neutrino deficit solved by the mechanism of oscillation between mass and flavour eigenstates (PMNS Matrix) AND matter density effects (MSW)

Δm2 θ = 22cos NG 2E F electron Physics Introduction

• present experimental values for oscillation parameters for νμ→ νe/ντ

νe disapperance CHOOZ No observation of

νμ −> νe SuperK No hint for

νμ −> νsteril

νμ disapperance

SNO collab Minos, SK collab

2 + 03.0 2 θ12 = 86.0)2(sin − 04.0 θ23,Δm 23 Atmospheric Neutrinos 2 θ23 > 92.0)2(sin SK, K2K, Minos 2 2 θ13 < 19.0)2(sin θ12, Δm 12 Solar Neutrinos 2 + 4.0 − 25 m21 − 3.0 ×=Δ 10)0.8( eV SNO, SK, KamLand m2 =Δ to9.1( ×10)0.3 − eV 23 32 Limit on θ13 CHOOZ, Global fit Physics Introduction

• Other running experiments (not complete) – Borexino (Italy, solar neutrinos) – Amanda/ Ice Cube, Antarctis, high energy astrophysical neutrinos) 2 – MINOS (USA, Δm 23, νe appearance, i.e. θ13) – Homestake (USA, solar neutrinos, θ12) 2 – Icarus (Italy, was inteded for ντ appearance i.e. θ23, Δm 23) • Experiments in preparation 2 – T2K (beam neutrinos, off-axis, θ23, Δm 23, νe appearance, i.e. θ13) ~2009 2 – Daya Bay (China, reactor neutrinos, sin 2θ13~0.01) ~2009 2 – Double CHOOZ (France, reactor neutrinos, sin 2θ13~0.02-0.03) ~2009 – Noνa (NuMi beam, off-axis νe appearance, i.e. θ13, phase δ, mass hierarchy) ~2010 (?! Budget was set to 0 by US in December) ⎛ Δ 2Lm ⎞ P =→ 2 2 θθνν2 27.1sin2sinsin)( ⎜ 23 ⎟ μ e 23 13 ⎜ ⎟ ⎝ E ⎠ Flavour Change Mixing of the neutrino mass eigenstates → Periodic change of neutrino flavour

„Interference of two frequencies“, neutrino

appears in the weak state as νe or νμ Quasi-elastic charm production

• CHORUS analysis + – For example: ΛC production 15% QE Associated charm production

σ(cc) 3 events observed in CHORUS =(3.6+2.9-2.4)x10-3 σ(NC)

Opera NC events 5540 Expected double charm in the detector 20±15 Discovery Potential

3 σ sensitivity

4 σ sensitivity Discovery probability Discovery probability %

SK 90% CL (L/E analysis) Last MINOS measurement Physics prospect

• Official mass reduction is 25%

• Target mass is around 1.35kton • Approximate number of bricks: 154750 (instead of 206336)

• Numbers of events after 5 years of nominal beam intensity

Signal ÷ (Δm2)2 – Full mixing Background: τ- Decay Charm channels Hadron interaction Δm2 = 2.5 x 10-3 eV2 Δm2 = 3.0 x 10-3 eV2 Muon scattering

τ- → µ- 2.9 4.2 0.17 τ- → e- 3.5 5.0 0.17 τ- → h- 3.1 4.4 0.24 τ- → 3h 0.9 1.3 0.17 ALL 10.4 15.0 0.76 Event 183545620 located in Bern – first (only) νe candidate

Em. Shower Neutrino vertex E = 4.7±1.3 GeV IP = ~3μm 8 mm

24 mm The Laboratori Nazionali del Gran Sasso (LNGS) • Close to Assergi (120km east of Rome) • In a highway tunnel (1.4 km rock) overburden

Rock shielding reduces cosmic flux to 1/m2 h

Host experiments in the field of neutrino physics: Borexino, LVD or Dark Matter physics: Crest, Gerda, WARP The Cern Neutrino to Gran Sasso beamline (CNGS) • Baseline 730 km

• (νe+νe)/νμ=0.68% • ντ prompt negligible

• Mean μ−neutrino energy 17 GeV

• Expectation of events for a nominal beam year (5x1019 protons on target)

– ~ 2900 νμ CC/kton/year – ~ 16 ντ CC/kton/year Long baseline concept

For more details/beam specification+ + wait for Claudia‘s Talk+ p + C → (interactions) → π , K → (decay in flight) → μ + νμ CNGS Beam Brick production and handling

- Bricks are produced by Brick Assembling Mashine (BAM) and handled with the Brick Manipulating System (BMS)

- Nearly all bricks are inserted, some missing due to burned down production hall of JLGoslar Event 178969961: νμCC interaction

19 m 8 m

43 mm

5 prongs associated to the neutrino interaction = 9 μm

17 mm Electromagnetic shower pointing to the vertex (γ conversion) The OPERA detector – μ−Spectrometer

μ momentum and charge is measured in magnetic spectrometer (See Claudia’s Talk

⇒ Inner tracker (RPC in magnet) and precision tracker (drift tube, 8 m length)

- μmiss charge ~ (0.1 - 0.3)% - Δp/p ~ 25% for p < 50 GeV

- P μid > 95% (with target tracker) The OPERA detector -TT

y x υ ν

• Target Tracker is used to identify the ECC brick, in which the interaction took place within few mm error • The brick is extracted and its CS is scanned to confirm the result Target Tracker

Plastic scintillator + wave length shifting fiber + 64 channel multi-anode Hamamatsu PM Event Analysis

Event 173520769, Brick 1029351

3 track candidates in Changeable Sheet (CS) found

Scanning was performed and 3 stopping points of tracks were found (2 at plate 47 and 1 at plate 51), residuals: 10- 20 µm

TotalScan of Volume: 1 cm² x 16 plates (from 42 to 57)

Vertex found with multiplicity of 4 plus 2 e+e- pairs φe+e-

γ Æ e+e- with φe+e- : 4 ± 2 mrad, Eγ : ~ 510 MeV

γ Æ e+e- with φe+e- : 8 ± 2 mrad, Eγ : ~ 260 MeV

θγγ φe+e- θγγ : 300 ± 20 mrad compatible π0 Æ 2 γ and a π0 mass: 110 ± 30 MeV Results of last October run

• run from October 3rd to October 12th (integrated intensity 0.81×1018 pot) – Only 0.4% of nominal CNGS year – Mainly low intensity beam, high intensity beam caused radiation failure in CNGS control electronics after ~1 day

• ~ 60’000 bricks were already in the detector

• 38 neutrino interactions in the inserted target bricks were recorded and the corresponding bricks were extracted

• First interaction called “Opera Baby” (Event 173520769)

• Brick Finding gave 90% propability for the redmarked brick to contain event

• Analysis of all events is going on in Japan and European Scanning labs