Search for Charged Current Coherent Pion Production by Neutrinos - PowerPoint PPT Presentation

Search for Charged Current Coherent Pion Production by Neutrinos at SciBooNE Morgan Wascko Imperial College London Birmingham Particle Physics Seminar 3 December, 2008

Contents • Introduction • SciBooNE Experiment • Search for Charged Current Coherent Pion Production • Conclusion

Introduction

Motivation if neutrinos have mass... a neutrino that is produced as a ν μ (e.g. π + → μ + ν μ ) • might some time later be observed as a ν e (e.g. ν e n → e - p) • ν μ ν e π + e - X μ + ν detector ν source 4

Neutrino Oscillation • Consider only two types � ν µ � � ν 1 � � � cos θ sin θ of neutrinos = ν e − sin θ cos θ ν 2 • If weak states differ from ν µ ν 1 mass states ν 2 • i.e. ( ν µ ν e ) ≠ ( ν 1 ν 2 ) ϴ ν e • Then weak states are mixtures of mass states | ν µ ( t ) � = − sin θ | ν 1 � e − iE 1 t + cos θ | ν 2 � e − iE 2 t • Probability to find ν e P osc ( ν µ → ν e ) = | � ν e | ν µ ( t ) � | 2 when you started with ν µ 5

Neutrino Oscillation • In units that experimentalists like: � 1 . 27 ∆ m 2 (eV 2 ) L (km) � P osc ( ν µ → ν e ) = sin 2 2 θ sin 2 E ν (GeV) • Fundamental Parameters • mass squared differences • mixing angle • Experimental Parameters • L = distance from source to detector • E = neutrino energy 6

Neutrino Oscillation Observations Super-K K2K 41.4m ν 1 ν 2 ν 3 Neutrino masses ( Δ m 122 , Δ m 232 ) ν e ν µ ν τ Mixing Angles ( θ 12 , θ 23 ) 39m Δ m 2 23 Δ m 2 12 θ 13 → δ KamLAND SNO MINOS 7

T2K Next Steps | ν α � = ∑ U α i | ν i � ν e ν 1 ν µ ν 2 i ν 3 ν τ NO ν A     0 s 13 e − i δ    1 0 0 c 13 c 12 s 12 0 U 0 c 23 s 23 0 1 0 − s 12 c 12 0 =        − s 13 e − i δ 0 0 − s 23 c 23 0 0 1 c 13 Cross Mixing atmospheric solar Discover the last oscillation channel → θ 13 CP violation in the lepton sector ( ν ,  ν ) → δ non-zero? Test of the standard ν oscillation scenario (U MNS ) → Precise measurements of ν oscillations (± Δ m 23 2 , θ 23 ) 8

accelerator Oscillation Experiments Gigantic detector Intense beam oscillation π , π , π , π , Κ ν , ν , ν , ν protons Φ ν (E) σ σ HARP MIPP SHINE σ (E) ⋅ Φ ν near (E) ⇔ σ (E) ⋅ Φ ν far (E) µ MiniBooNE K2K-ND ν MINER ν A SciBooNE proton 9

Background Processes ν μ disappearance ( ν μ → ν x ) ν e appearance ( ν μ → ν e ) ν μ CC-QE ν e CC-QE Signal Signal µ e ν µ ν e W W n p n p ν μ CC-1 π + Background Background NC-1 π 0 µ ν ν µ ν π 0  γ + γ π + W Z N N N N Need to understand these processes as well 10

Background Processes ν μ disappearance ( ν μ → ν x ) T2K (MC) ν μ events “Non-QE” mainly CC-1 π + sin 2 2 θ 23 Uncertainty in the non-QE background affects the measurement of oscillation Δ m 2 parameters 11

ν -nucleus cross sections Future neutrino oscillation experiments need precise knowledge of neutrino cross sections near 1GeV Data from old experiments ( 1970~1980 ) QE Low statistics Systematic Uncertainties DIS New data from 1 π K2K & MiniBooNE revealing surprises MINOS K2K, NOvA MiniBooNE, T2K, SciBooNE Super-K atmospheric ν 12

SciBooNE Description

SciBooNE Experiment (FNAL E954) Booster Neutrino Beam • Precise measurements of neutrino- and antineutrino-nucleus cross sections near 1 GeV • Essential for future neutrino oscillation experiments • Neutrino energy spectrum measurements • MiniBooNE/SciBooNE joint ν μ disappearance • ν e constraint for MiniBooNE 14

SciBooNE Collaboration Universitat Autonoma de Barcelona Mar 18, 2008 University of Cincinnati University of Colorado, Boulder Columbia University Fermi National Accelerator Laboratory High Energy Accelerator Research Organization (KEK) Imperial College London Indiana University Institute for Cosmic Ray Research (ICRR) Kyoto University Los Alamos National Laboratory Louisiana State University Purdue University Calumet Universita degli Studi di Roma "La Sapienza“ and INFN Saint Mary's University of Minnesota Tokyo Institute of Technology Unversidad de Valencia ~60 physicists Spokespeople: 5 countries 17 institutions M.O. Wascko (Imperial), T. Nakaya (Kyoto) 15

Booster Proton accelerator 8 GeV protons sent to target Target Hall Beryllium target: 71cm long 1cm diameter Resultant mesons focused with magnetic horn Reversible horn polarity To MiniBooNE 50m decay volume SciBooNE Mesons decay to μ & ν μ Short decay pipe minimizes μ → ν e decay SciBooNE located 100m from the beryllium target SciBooNE

Booster Neutrino Beam Expected neutrino flux at SciBooNE (neutrino mode) • mean neutrino energy ~0.7 GeV • 93% pure ν μ beam • anti- ν μ (6.4%) • ν e + anti- ν e (0.6%) • antineutrino beam is obtained by reversing horn polarity 17

Neutrino Event Generator (NEUT) • QE • Llewellyn Smith, Smith-Moniz • M A =1.2GeV/c 2 • P F =217MeV/c, E B =27MeV (for Carbon) • Resonant π • Rein-Sehgal (2007) • M A =1.2 GeV/c 2 CC/NC-1 π • Coherent π • Rein-Sehgal (2006) • M A =1.0 GeV/c 2 • Deep Inelastic Scattering • GRV98 PDF • Bodek-Yang correction • Intra-nucleus interactions 18

SciBooNE detector Muon Range Detector SciBar (MRD) • scintillator tracking • 12 2”-thick steel detector • 14,336 scintillator + scintillator planes • measure muon bars (15 tons) • Neutrino target ν • detect all charged momentum with range up to 1.2 GeV/c particles • p/ π separation Parts recycled from past experiments using dE/dx 4m Electron Catcher (EC) Used in K2K experiment • spaghetti calorimeter 2m • 2 planes (11 X 0 ) • identify π 0 and ν e DOE-wide Pollution Prevention Star (P2 Star) Award Used in CHORUS, HARP and K2K 19

SciBooNE Timeline • 2005, Summer - Collaboration formed • 2005, Dec - Proposal • 2006, Jul - Detectors move to FNAL • 2006, Sep - Groundbreaking • 2006, Nov - Sub-detectors Assembly • 2007, Apr - Detector Installation • 2007, May - Commissioning Only 3 years from • 2007, Jun – Started Data-taking formation to 1 st physics result • 2008, Aug – Completed data-taking • 2008, Nov – 1 st physics result 20

SciBooNE Timeline Groundbreaking ceremony (Sep. 2006) Detector Assembly (Nov. 2006 -Mar.2007) 21

SciBooNE Timeline Detector installation (Apr. 2007) End-of-run party (Aug. 2008) 22

SciBooNE data-taking Number of Protons on target (POT) • Jun. 2007 – Aug. 2008 • 95% data efficiency • 2.52x10 20 POT in total • neutrino : 0.99x10 20 POT • antineutrino: 1.53x10 20 POT Many thanks to FNAL Accelerator Division! Results from full neutrino data set presented today 23

Neutrino event displays Real SciBooNE Data ADC hits (area ∝ charge) vertex resolution TDC hits (32ch “ OR”) ~5 mm SciBar EC MRD anti - ν µ CC-QE candidate ν µ CC-QE candidate ( ν µ + p  µ + n) ( ν µ + n  µ + p) 24

Search for CC Coherent Pion Production

Coherent pion production The signal for today’s search • Neutrino interacts with nucleons coherently, producing a pion • No nuclear breakup occurs ℓ A ν π Charged Current (CC): ν μ +A → μ +A+ π + Neutral Current (NC): ν μ +A → ν μ +A+ π 0 Several measurements (before K2K and MiniBooNE) • both NC and CC • both neutrino and antineutrino • >2 GeV (NC), >7 GeV (CC) up to ~100 GeV 26

Surprises CC coherent π + NC coherent π 0 K2K, MiniBooNE, Phys.Rev.Lett. 95,252301 (2005) Phys.Lett. B664,41 (2008) No evidence of CC coherent pion production is found at <E ν >=1.3 GeV First observation of NC coherent pion production at E ν <2GeV σ (CC coherent π )/ σ (CC)<0.60x10 -2 (90%CL) (corresponds to 23% of the prediction) 65% of the model prediction 27

CC Coherent Pion Production Signal µ Small Q 2 C CC-coherent π production ν π ν +C → μ +C+ π + • 2 MIP-like tracks (a muon and a pion) • ~1% of total ν interaction based on Rein-Sehgal model µ Background ν p,n CC-resonant π production • ν +p → μ +p+ π + often not π • ν +n → μ +n+ π + reconstructed 28

CC-1 π + candidate 29

Charged Current (CC) event selection ν μ CC • Muons identified using MRD µ ν µ • Tracks should start from SciBar fiducial volume W N X SciBar-MRD matched event (~30k events) MRD-stopped MRD-side escaped MRD-penetrated (low-energy sample) (high-energy sample) EC EC EC SciBar SciBar SciBar MRD MRD MRD muon muon muon X X X 93% pure CC-inclusive ( ν +N → μ +X) sample 30

CC event classification Define MC SciBar-MRD matched sample normalization MRD-stopped MRD-penetrated 1track 2track >2track Number of tracks Same selection μ +p μ + π Particle identification Energy deposit w/ activity w/o activity around the vertex MRD-stopped MRD-penetrated CC-coherent π CC-coherent π sample sample 31

Number of tracks MRD-stopped 1track 2track >2track Search for tracks from the vertex (R<10cm) vertex Muon candidate R<10cm 32