A search for disappearance with: SciBooNE MiniBooNE and Kendall - PowerPoint PPT Presentation

A search for ν µ disappearance with: SciBooNE MiniBooNE and Kendall Mahn TRIUMF For the SciBooNE and MiniBooNE collabora>ons 5/1/2011 0

Neutrino oscillations in 2011 Neutrino oscillations thus far are consistent with three flavors of neutrinos which mix with the mass states according to a unitary matrix → → Lack of ν µ ν e appearance but observation of ν µ ν e appearance at Δ m 2 ~1 eV 2 by the MiniBooNE Phys.Rev.LeJ.105:181801,2010 Phys.Rev.LeJ.98:231801,2007 numubar -> nuebar oscillations ν e ν e 5/1/2011 1

ν µ disappearance at Δ m 2 ~1 eV 2 Exotic physics is required to explain a difference between neutrinos and antineutrinos and the presence of an additional, large, mass splitting Sterile neutrinos (with or without CPT violation) G. Karagiorgi et al, Phys.Rev.D75:013011,2007. hep-ph/0609177 Barger, Marfatia, & Whisnant, Phys. Lett. B576 (2003) 303 Neutrino decay: Palomares-Ruiz, Pascoli, Schwetz, JHEP 0509:048,2005. hep-ph/0505216 Extra dimensions: Pas, Pakvasa, Weiler, Phys.Rev.D72:095017,2005. hep-ph/0504096 New, light gauge boson: Nelson, Walsh Phys .Rev. D77 033001 (2008) hep-ph/0711.1363 → Searches for ν µ ν s disappearance test the same physics as → → ν µ ν s ν e appearance An observation of ν µ disappearance at 0.1< Δ m 2 < 100 eV 2 would clarify the nature of any new physics A lack of disappearance in the region would constrain new physics models 5/1/2011 2

Existing measurements of ν µ disappearance 2 2 2 2 10 10 10 10 MiniBooNE, CDHS, CCFR experiments observe no ν µ disappearance (90%CL) 10 10 10 10 eV 2 m MiniBooNE, CCFR experiments 2 # observe no ν µ disappearance 1 1 1 1 MiniBooNE 90% CL sensitivity ! ! MiniBooNE ! 90% CL limit ! (90%CL) best fit: (17.50, 0.16) with of 12.72, (null) of 17.78 " 2 " 2 90%CL excluded, CDHS 90%CL excluded, CDHS 90%CL excluded, CDHS 90%CL excluded, CDHS 90%CL excluded, CCFR 90%CL excluded, CCFR 90%CL excluded, CCFR 90%CL excluded, CCFR -1 -1 -1 -1 10 10 10 10 MiniBooNE-only results limited by neutrino flux and neutrino interaction uncertainties 10 10 10 10 eV eV eV eV 2 2 2 2 Constrain these with a set of near m m m m 2 2 2 2 # # # # detectors: SciBooNE 1 1 1 1 __ __ __ __ Same beamline, same neutrino target MiniBooNE 90% CL sensitivity ! __ __ __ __ ! MiniBooNE 90% CL limit ! ! best fit: (31.30, 0.96) with of 5.43, (null) of 10.29 " 2 " 2 90%CL excluded, CCFR 90%CL excluded, CCFR 90%CL excluded, CCFR 90%CL excluded, CCFR -1 -1 -1 -1 10 10 10 10 -2 -2 -2 -2 -1 -1 -1 -1 10 10 10 10 10 10 10 10 1 1 1 1 sin sin sin sin (2 (2 (2 (2 ) ) ) ) 2 2 2 2 $ $ $ $ Phys.Rev.LeJ.103:061802,2009 5/1/2011 3

The Booster Neutrino Experiments (BooNEs) 8 GeV/c protons from the Fermilab Booster strike a Be target Pions and kaons are produced which decay to produce a neutrino beam 100m from the target are the SciBooNE detectors:  14,336 scintillator bar detector read out with WLS fibers attached to 64 channel MA-PMTs (SciBar)  Lead and scintillator fiber electromagnetic calorimeter (EC)  Iron and scintillator counter muon range detector (MRD) 541m from the target is the MiniBooNE detector  1kton mineral oil Cherenkov detector  1240 inner PMTs, 240 veto PMTs MiniBooNE target decay SciBooNE 541m Booster horn volume 100m 5/1/2011 4 4

Selecting CC ν µ interactions in SciBooNE SciBar EC MRD  Select events with the highest momentum track with a vertex in e - SciBar fiducial volume which pass µ data quality, beam timing cuts µ ‐ ν µ ν µ  Events which also end in SciBar: µ ‐ ν µ “SciBar contained” Use energy loss in scintilator to select CC ν µ muon-like tracks µ ‐ ν µ p µ >250 MeV/c reduces NC events W +  Events which stop in the MRD: Real neutrino candidates “MRD Stopped” SciBar SciBar µ  Events which exit the end of the MRD: MRD p “MRD Penetrated” ν µ ν µ Angular information only EC p µ 10/31/08 W&C 5/1/2011 5

Selecting CCQE ν µ interactions in MiniBooNE Tag single muon events and their decay electron  Events produce Cherenkov light recorded by PMTs as hits (charge, time)  Two sets of hits separated in time ( µ , e) µ 12 C e  Minimal hits in the veto ν µ n p  Require 1 st set of hits above decay electron energy endpoint, 2 nd set of hits below  Endpoint of 1 st track consistent with vertex of 2 nd track  Also require events within fiducial volume, beam timing and data quality selections μ‐ ν µ muon candidate electron candidate 5/1/2011 6

Disappearance analysis strategy Use the CC ν µ rate measured at SciBooNE to constrain the MiniBooNE ν µ rate and test for disappearance Two analysis methods: Simultaneous fit 1) Fit SciBooNE and MiniBooNE data simultaneously for oscillation 2) Constraint applied within fit, effectively removes systematic uncertainties shared by both detectors Spectrum fit 1) Extract neutrino energy spectrum from SciBooNE data Phys.Rev.D83:012005,2011 2) Apply correction to MiniBooNE energy spectrum 3) Fit for oscillation at MiniBooNE 4) Systematics reduced by extraction process 5/1/2011 7

SciBooNE CC ν µ data set SciBar stopped MRD stopped Events Events 4500 3000 Data Data 4000 2500 Null oscillation Null oscillation 3500 Non-CCQE events Non-CCQE events 3000 2000 2500 1500 2000 1500 1000 1000 500 500 1.5 0 1.5 0 Ratio Ratio 1.4 Best fit 1.4 Best fit 2 2 2 2 2 m = 1.0 eV , sin 2 = 0.5 2 # " m = 1.0 eV , sin 2 = 0.5 # " 1.3 1.3 2 2 2 2 2 m = 10 eV , sin 2 = 0.5 2 # " m = 10 eV , sin 2 = 0.5 # " 1.2 1.2 1.1 1.1 1 1 0.9 0.9 0.8 0.8 0.7 0.7 0.6 0.6 0.5 0.5 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Reconstructed E (GeV) Reconstructed E (GeV) ! ! First, test agreement of SciBooNE datasets Above Δ m 2 > 2 eV 2 , oscillation is possible at SciBooNE No evidence for oscillation at SciBooNE Uncertainties include neutrino flux, cross section and detector uncertainties 5/1/2011 8

MiniBooNE CCQE ν µ data set MiniBooNE CCQE ν µ data set + prediction (no oscillation) Events 30000 Fit 16+16+16 bins in total = 48 Data 25000 Null oscillation χ 2 (null) = 45.1/ 48 (DOF) 20000 Non-CCQE events χ 2 (best) = 39.5/ 46 (DOF) 15000 At Δ m 2 = 43.7 eV 2 , sin 2 2θ = 0.60 10000 Δ χ 2 = χ 2 (null) – χ 2 (best) = 5.6 5000 1.5 0 Δ χ 2 (90% CL, null) = 9.3 Ratio 1.4 Best fit 2 2 2 m = 1.0 eV , sin 2 = 0.5 # " 1.3 2 2 2 m = 10.0 eV , sin 2 = 0.5 # " Feldman Cousins frequentist 1.2 1.1 technique used to determine 1 Δχ 2 statistic 0.9 0.8 0.7 0.6 0.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Reconstructed E (GeV) ! 5/1/2011 9

Results of ν µ disappearance fit ] 2 Limits for simultaneous fit (black) [eV and spectrum fit (blue) 2 m " Green hatched region indicates 68% of 90%CL limits to fake 10 90% CL limits from previous exp’s. data with no underlying 90% CL sensitivity (Sim. fit) oscillation 90% CL observed (Sim. fit) 90% CL observed (Spec. fit) Average of these limits is 1 sensitivity, comperable for both analysis methods Largest uncertainty is MiniBooNE detector systematics -1 10 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 2 sin 2 ! No disappearance at 90% CL observed for either method 5/1/2011 10

Conclusion First joint venture of the SciBooNE and MiniBooNE experiments A fit to SciBooNE and MiniBooNE data is consistent with no muon neutrino disappearance at 90%CL  Two complementary methods have consistent results  New exclusion region between 10 < Δ m 2 < 30 eV 2  Provides additional constraints on exotic physics models, such as sterile neutrinos SciBooNE took antineutrino data which will be used for a joint SciBooNE-MiniBooNE ν µ disappearance analysis 5/1/2011 11

Backup slides 5/1/2011 12

Sensitivity Improvement over previous MiniBooNE-only analysis sensitivity Two methods have similar sensitivities Slightly better sensitivity for simultaneous fit 5/1/2011 13

Oscillation probability MiniBooNE CCQE ν µ 1.04 " m 2 =1eV 2 1.04 " m 2 =6eV 2 1.02 1.02 1 SciBooNE MRD stopped 1 0.98 0.98 0.96 0.96 SciBooNE SciBar stopped 0.94 0.94 0.92 0.92 Oscillation at sin 2 2 θ = 0.10 0.9 0.9 0.88 Includes range in L present 0.88 0.86 0.86 at each detector 0.5 1 1.5 0.5 1 1.5 reconstructed E ! (GeV) reconstructed E ! (GeV) 1.04 " m 2 =9eV 2 1.04 " m 2 =3eV 2 1.02 1.02 1 1 0.98 0.98 0.96 0.96 0.94 0.94 0.92 0.92 0.9 0.9 0.88 0.88 0.86 0.86 0.5 1 1.5 0.5 1 1.5 (GeV) reconstructed E ! (GeV) reconstructed E ! (GeV) 5/1/2011 14

Spectrum fit method MiniBooNE CCQE ν µ dataset + prediction corrected from SciBooNE datasets (spectrum fit, reduced errors) Best fit: Δ m 2 =41.5 eV 2 Events 30000 sin 2 2 θ = 0.51 Data 25000 Null oscillation χ 2 (null) = 41.5/ 32 (DOF) Non-CCQE events 20000 χ 2 (best) = 35.6/ 30 (DOF) 15000 Δχ 2 = χ 2 (null) – χ 2 (best) = 5.9 10000 5000 Δχ 2 (90% CL, null) = 8.4 1.5 0 Estimated from frequentist Ratio 1.4 Best fit techniques 2 2 2 m = 1.0 eV , sin 2 = 0.5 # " 1.3 2 2 2 m = 10.0 eV , sin 2 = 0.5 # " 1.2 No significant oscillation observed 1.1 1 0.9 0.8 0.7 0.6 0.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Reconstructed E (GeV) ! 5/1/2011 15