3 2 neutrino phenomenology and studies at miniboone n.
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3+2 Neutrino Phenomenology and Studies at MiniBooNE

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3+2 Neutrino Phenomenology and Studies at MiniBooNE

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  1. 3+2 Neutrino Phenomenology and Studies at MiniBooNE Georgia Karagiorgi, Columbia University PHENO 2007 Symposium May 7-9, 2007 U. Wisconsin, Madison

  2. Outline • Motivation for 3+2 models • 3+2 phenomenology and oscillation formalism • The MiniBooNE result and experimental constraints for 3+2 models • CP violation studies in 3+2 models and prospects for CPV measurement at MiniBooNE • Current status of 3+2 analysis and future plans • Conclusions G. Karagiorgi et al., “Leptonic CP violation studies at MiniBooNE in a (3+2) sterile neutrino oscillation hypothesis,” Phys. Rev. D. 75, 013011 (2007) [hep-ph/0609177]. Georgia Karagiorgi, Columbia U.

  3. The LSND Signal Δm2LSND ~ 0.1- 10 eV2 + small mixing Δm2LSND >> Δm2atm>> Δm2sol one option:3 active + n “sterile” neutrinosother options: neutrino decay, extra-D, etc. Georgia Karagiorgi, Columbia U.

  4. 3+2 Model Phenomenology 3 active + 2 sterile neutrinos • lightsterile neutrinos • they can interact thru non-standard weak couplings • they have very small active flavor content (Ue4,…, Ue5,…) •  can participate in neutrino oscillations νe νμ ντ νs increasing m2(not to scale) Why n=2? 3+1 models: SBL and LSND marginally consistent with each other 3+2: next natural step… [M. Sorel, et al. hep-ph/0305255] Georgia Karagiorgi, Columbia U.

  5. 3+2 Model Phenomenology GUT’s Mohapatra, Nasri, & Yu [hep-ph/0505021] De Gouvea, Jenkins, & Vasudevan [hep-ph/0608147] Extra-D Pas, Pakvasa, & Weiler [hep-ph/0504096] Ma, Rajasekaran, & Sarkar [hep-ph/0006340] SUSY Kang, & Li [hep-ph/0501101] Dvali, & Nirb [hep-ph/9810257] Georgia Karagiorgi, Columbia U.

  6. 3+2 Neutrino Oscillation Formalism General neutrino oscillation formula: P(νανβ) = δαβ – 4ΣRe (U*αiUβiUαjU*βj)sin2xij + 2 ΣIm (U*αiUβiUαjU*βj) sin2xij P(νμνe) = 4|Uμ4|2|Ue4|2sin2x41 + 4|Uμ5|2|Ue5|2sin2x51 + + 8 |Uμ5||Ue5||Uμ4||Ue4|sinx41sinx51cos(x54+φ45) xij = 1.27Δm2ij L/E Assumptions for 3+2 model analysis: approximatem1 = m2 = m3 = 0 * two independent mass splittings:Δm241,Δm251 four moduli:|Ue4|,|Uμ4|,|Ue5|,|Uμ5| one CPV phase:φ54 = arg(U*μ5 Ue5 Uμ4 U*e4) * This allows for 6  1 CPV phase in a (3+2) hypothesis (3  0 CPV phases in a (3+1) hypothesis) (1  0 CPV phases in a (3+0) hypothesis) 3+2 model = most minimal model for CPV studies! Georgia Karagiorgi, Columbia U.

  7. First Results from MiniBooNE MiniBooNE result excludes the LSND 90%CL allowed regionat > 90% CL… “A Search for Electron Neutrino Appearance at the Δm2 ~ 1eV2 Scale,” The MiniBooNE Collaboration [hep-ex/0704.1500]. Georgia Karagiorgi, Columbia U.

  8. First Results from MiniBooNE …MiniBooNE result assumes: CP-conserving, 2-neutrino oscillation scenario E > 475 MeV Excess of νe events at low energies: Currently investigating if this is a detector effect, or SM background… Could be a manifestation of beyond the SM physics… For more information on this, see talk by Chris Polly Georgia Karagiorgi, Columbia U.

  9. Experimental Constraints We are interested in: • studying the compatibility of null SBL results with LSND and MiniBooNE results in a 3 active + 2 sterile neutrino hypothesis • constraining the3+2 model parameters sin2θ constraint (90%CL) Georgia Karagiorgi, Columbia U.

  10. Combined NSBL+LSND+MiniBooNE • 3+2 analysis (including MB νebackground disappearance) • and compatibility tests are currently in progress… • Recent studies: • Leptonic CP violation studies at MiniBooNE in a 3+2 sterile neutrino oscillation hypothesis • Expected oscillation probability at MiniBooNE • Potential of CP-violation measurement at MiniBooNE [hep-ph/0609177] Dataset: NSBL + LSND only (no atmospheric or solar experiment data) + Super-K atm. constraint Georgia Karagiorgi, Columbia U.

  11. Oscillation Analysis for CPV Studies at MiniBooNE P(νμνe) = 4|Uμ4|2|Ue4|2sin2x41 + 4|Uμ5|2|Ue5|2sin2x51 + + 8 |Uμ5||Ue5||Uμ4||Ue4|sinx41sinx51cos(x54+φ45) • Generate masses and mixing parameters (models): • 0.1eV2≤Δm241, Δm251≤ 100eV2 Δm251 ≥Δm241 • |Ue4|, |Uμ4|,|Ue5|,|Uμ5| Uei2 + Uμi2≤ 0.5, Uα42 + Uα52≤ 0.5 • atmospheric constraint: dμ = ½ - √(1-4A)/2 where A = (1 - |Uμ4|2- |Uμ5|2)(|Uμ4|2+ |Uμ5|2) + |Uμ4|2|Uμ5|2 CP violation option: Fix φ54=0,π, or allow to vary within (0,2π) • Calculate expected oscillation probabilities at MiniBooNE (using expected full νμ νetransmutation rates) • Determine allowed regions by Gaussian approximation Importance sampling via Markov chain: P(xi xi+1) = min{1,exp[-(χ2i+1-χ2ι)/Τ]} xi+1 = xi + e Georgia Karagiorgi, Columbia U.

  12. Oscillation probability expected at MiniBooNE CP-conserving 3+2 models CP-violating 3+2 models 90%CL 99%CL Best fit models:CPC: χ2/dof = 141.4/145CPV: χ2/dof = 140.8/144 Georgia Karagiorgi, Columbia U.

  13. Potential observation of CP-violation at MiniBooNE All CP-violating phase values allowed at 99%CL by the NSBL+LSND data are measurable at MiniBooNE Small degrees of CPV preferred Large asymmetries allowed, but not required Georgia Karagiorgi, Columbia U.

  14. First global fit results χ2PG = 17.5 , PG = 1.5x10−3 (no MB) χ2PG = 25.1 , PG = 4.8x10−5 (MB300) Best fit parameters for global fit with full MiniBooNE E range: Δm241 = 0.87eV2 x2min /dof = 104.4/(109-7) Δm251 = 1.91eV2 gof = 41% cpv-phase = 1.44π Analysis by Maltoni & SchwetzFig. 7 [hep-ph/0705.0107] Georgia Karagiorgi, Columbia U.

  15. Potential observation of CP-violation at MiniBooNE MiniBooNE expected oscillation probability asymmetry based on calculated best fit model parameters from hep-ph/0705.0107 global 3+2 analysis (MB300 and MB475) MB475 Ap/p = -0.315 MB300 Ap/p = -0.448 φ45 = 1.44π Georgia Karagiorgi, Columbia U.

  16. First global fit results • 3+2 neutrino models: • provide a good fit to LSND and the recent MB data • can account for the low energyevent excess in MB • However: • there is significant tensionbetween appearance and disappearance data (according to the PG test at the level of 3σ for MB475 and 4σ for MB300). Note: analysis done without full MiniBooNE error matrix MB signal prediction from best fit points from SBL appearance data (LSND, KARMEN, NOMAD, MB) in a 3+2 oscillation analysis Maltoni & SchwetzFig. 3 [hep-ph/0705.0107] Georgia Karagiorgi, Columbia U.

  17. Our next 3+2 steps… More detailed combined NSBL + LSND + MiniBooNE 3+2 oscillation analysis and compatibility tests, that take into consideration: • Full MiniBooNE error matrix • Disappearance of MiniBooNE νe background Georgia Karagiorgi, Columbia U.

  18. Conclusions • Original motivation: accommodate null SBL and LSND results within the framework of neutrino oscillations • MiniBooNE data: key in addressing the viability of 3+2 models with sterile neutrinos • Leptonic CP-violation possibility opened up in the 3+2 sterile neutrino hypothesis could have large measurable effects at MiniBooNE Georgia Karagiorgi, Columbia U.