Results from the MINOS Experiment Gregory Pawloski Stanford - PowerPoint PPT Presentation

Results from the MINOS Experiment Gregory Pawloski Stanford University On behalf of the MINOS Collaboration FNAL Users' Meeting 2009-6-3

MINOS Collaboration 140 Physicists from 28 institutions Argonne • Athens • Benedictine • Brookhaven • Caltech • Cambridge • Campinas • Fermilab • Harvard • Holy Cross • IIT • Indiana • Minnesota- Twin Cities • Minnesota-Duluth • Otterbein • Oxford • Pittsburgh • Rutherford • Sao Paulo • South Carolina • Stanford • Sussex • Texas A&M • Texas-Austin • Tufts • UCL • Warsaw • William & Mary 2 Results from the MINOS Experiment —― Gregory Pawloski

Physics Goals of MINOS Main Injector Neutrino Oscillation Search The primary function of the MINOS experiment is to study neutrino oscillations at the atmospheric mass-squared splitting Weak Eigenstates Mass Eigenstates ν 3 ν τ |Δm 2 atm | ~ 2.43 x 10 -3 eV 2 ν μ ν 2 Δm 2 sol ~ 8.0 x 10 -5 eV 2 ν e ν 1 Mass eigenstates are a linear combination of weak states 3 Results from the MINOS Experiment —― Gregory Pawloski

Oscillations at the Atmospheric Splitting A ν of one flavor will become a superposition of other flavors as it propagates P(ν α →ν β ) = δ αβ −4 ∑ R (U * αi U βi U αj U * βj )sin 2 [1.27Δm 2 ij (L/E)] i > j +2 ∑ I (U * ij (L/E)] αi U βi U αj U * βj )sin[2.54Δm 2 i > j Mass Eigenstates ● Δ m 2 atm >> Δ m 2 ν 3 sol ● For E/L ~ Δ m 2 atm terms with that |Δm 2 atm | ~ 2.43 x 10 -3 eV 2 mass term dominate the probability ν 2 ● MINOS L/E is tuned to this scale Δm 2 sol ~ 8.0 x 10 -5 eV 2 ν 1 For one mass scale dominance P(ν α →ν β ) ≈ S α β sin 2 [1.27Δm 2 (L/E)], for α ≠ β S αβ term is related to components of the mixing matrix 4 Results from the MINOS Experiment —― Gregory Pawloski

Oscillations Studied at MINOS The following analyses will be covered in this presentation 5 Results from the MINOS Experiment —― Gregory Pawloski

Oscillations Studied at MINOS The following analyses will be covered in this presentation ν μ →ν τ oscillations Study oscillations through the disappearance of ν μ CC events Identify ν flavor by finding muons from CC interactions Measure: |Δm 2 32 | sin 2 (2θ 23 ) Rule out exotic models: Decoherence Decay Neutrino Survival Probability P(ν μ →ν μ ) ≈ 1 - sin 2 (2θ 23 )sin 2 (1.27Δm 2 L/E) 6 Results from the MINOS Experiment —― Gregory Pawloski

Oscillations Studied at MINOS The following analyses will be covered in this presentation ν μ →ν τ oscillations Study oscillations through the disappearance of ν μ CC events Identify ν flavor by finding antimuons from CC interactions Measure: |Δm 2 32 | sin 2 (2θ 23 ) Test of CPT conservation and/or nonstandard interactions Matter States Matter States Antimatter States ν 3 ν 3 Δm 2 Δm 2 atm atm ν 2 ν 2 Δm 2 Δm 2 ν 1 ν 1 sol sol P(ν μ →ν μ ) ≈ 1 - sin 2 (2θ 23 )sin 2 (1.27Δm 2 L/E) 7 Results from the MINOS Experiment —― Gregory Pawloski

Oscillations Studied at MINOS The following analyses will be covered in this presentation Sterile neutrinos: ν μ →ν s oscillations Identify active ν by identifying NC interactions Study oscillations through the disappearance of NC events Sensitive to: f s , θ 24 , θ 34 3 Eigenstates 4 Eigenstates m 1 ≈ m 4 m 4 » m 3 ν 4 ν s ν 3 ν 3 Δm 2 43 ν τ Δm 2 atm Δm 2 ν 3 ν 2 atm ν 2 Δm 2 ν μ ν 1 Δm 2 sol ν 1 Δm 2 atm sol ν 2 ν 4 ν 1 Δm 2 ν e sol P(ν μ →ν s ) = 0 P(ν μ →ν s ) ≈ C a sin 2 (1.27Δm 2 L/E) P(ν μ →ν s ) ≈ C b sin 2 (1.27Δm 2 L/E) + C c C a , C b , C c are my own shorthand for terms involving the mixing matrix 8 Results from the MINOS Experiment —― Gregory Pawloski

Oscillations Studied at MINOS The following analyses will be covered in this presentation ν μ →ν e oscillations Study oscillations through the appearance of ν e CC events Identify ν flavor by finding electrons from CC interactions Sensitive to: sin 2 (2θ 13 ) δ CP θ 13 is the only unmeasured mixing angle in 3 flavored lepton sector CP violating effects involve θ 13 terms ν 3 Δm 2 Want to measure this component atm ν 2 Δm 2 sol ν 1 P(ν μ →ν e ) ≈ sin 2 (θ 23 )sin 2 (2θ 13 )sin 2 (1.27Δm 2 L/E)+“δ CP -terms”+“mass hierarchy sensitive terms”+... All these terms are significant. Matters effects will alter the probability 9 Results from the MINOS Experiment —― Gregory Pawloski

How do we study these oscillations?

Long Baseline Accelerator Neutrinos Use a neutrino beam derived from 120 GeV protons from Fermilab's Main Injector Use 2 functionally identical detectors: A Near Detector at Fermilab to measure the unoscillated beam composition and the energy spectrum A Far Detector deep underground in the Soudan Mine in Minnesota to search for evidence of oscillations Extrapolate Near Spectrum to the Far Detector to minimize uncertainties due to: Cross section, flux, event detection and selection 11 Results from the MINOS Experiment —― Gregory Pawloski

NuMI (Neutrinos at the Main Injector) Beam Protons are guided towards a graphite target producing a stream of mesons 2 magnetic horns are optimized to focus positively charged particles whose subsequent decays produce neutrinos 12 Results from the MINOS Experiment —― Gregory Pawloski

NuMI Beam Composition The resulting neutrino energy spectrum can be modified by adjusting the relative position of the target and the horns The default configuration is “Low Energy” which optimizes our L/E for the atmospheric mass-squared splitting CC interactions in the Near Detector are: 92% ν μ 7% ν μ 1% ν e + ν e 13 Results from the MINOS Experiment —― Gregory Pawloski

2 Detector Experiment UVUVUVUV Functionally identical tracking calorimeters with Steel alternating layers of steel and scintillator Scintillator 2.54cm thick magnetized steel planes: <B> = 1.2 T Neutrino beam Muon Charge & Momentum Measurements Orthogonal strips 1cm thick scintillator planes Segmented into 4.1cm wide strips Alternating planes rotated by 90 o Reconstruct 3D position Sample Frequency: 1.4 radiation lengths 1 GeV/c muon travels ~20 planes Light transported through wavelength shifting and clear fibers Signal read out through mutil-anode Hamamatsu PMTs Some differences due to flux considerations Number of interactions per beam spill Detector Size: 1kton (Near) vs 5.4kton (Far) M64 (Near) vs M16 (Far) PMT Multiplexing (Far) Single Ended readout in Near 14 Results from the MINOS Experiment —― Gregory Pawloski

Event Topologies ν μ CC Event NC Event ν e CC Event ν ν ν e e − ν µ µ − Z W W Hadrons Hadrons Hadrons N N N UZ Monte Monte Monte Carlo Carlo Carlo VZ 1.8m 3.5m 2.3m Long muon track & Short event Compact event hadronic activity at Often diffuse EM shower profile vertex 15 Results from the MINOS Experiment —― Gregory Pawloski

Data Samples Total Protons on NuMI Target 2008 CC publication (3.36e20) 2009 anti- ν analysis (3.2e20) 2009 NC publication (3.18e20) 2009 ν e analysis (3.14e20) Run I Higher Energy Run II Run III Configuration 1.27x10 20 POT 1.87x10 20 POT ~4x10 20 POT 0.15x10 20 POT 16 Results from the MINOS Experiment —― Gregory Pawloski

ν μ Charged Current Disappearance with 3.36 x 10 20 POT Measurements of sin 2 (2θ 23 ), |Δm 2 32 | Published: Phys. Rev. Lett. 101 131802 (2008)

ν μ CC Disappearance – The Purpose Looking for a deficit of ν μ events in the Far Detector Precision measurements of atmospheric ∆ m 2 and sin 2 (2 θ ) Test the neutrino oscillation hypothesis   ∆ 2 1 . 27 m L   → ν = − θ 2 2 P ( v ) 1 sin 2 sin , L=735 km   µ µ E   ν µ spectrum spectrum ratio ν µ Spectrum Spectrum Ratio Monte Carlo Monte Carlo Unoscillated Oscillated sin 2 (2 θ ) ∆ m 2 18 Results from the MINOS Experiment —― Gregory Pawloski

ν μ CC Disappearance – The Selection ν μ CC-like events are selected with a nearest neighbors (kNN) based algorithm with four inputs based on hits belonging to the track: Track length (planes) Mean pulse height/plane Fluctuation in pulse height Transverse track profile 19 Results from the MINOS Experiment —― Gregory Pawloski

ν μ CC Disappearance – Near to Far Extrapolation π + Target FD p Decay Pipe ND The observed Near spectrum is extrapolated to the Far Detector Use Monte Carlo to provide corrections due to energy smearing and acceptance Encode pion decay kinematics & angular acceptance into a matrix used to transform the ND spectrum into the FD energy spectrum MC MC Uncertainties on flux and cross section largely cancel Uncertainties on flux and cross section largely cancel 20 Results from the MINOS Experiment —― Gregory Pawloski

ν μ CC Disappearance – Systematic Uncertainties The impact of different sources of systematic uncertainty are evaluated by fitting modified MC in place of the data The 3 largest sources of uncertainty are included as nuisance parameters in the oscillation fit Far/Near Normalization (4%) Absolute Hadronic Energy Scale (10.3%) NC Contamination (50%) 21 Results from the MINOS Experiment —― Gregory Pawloski