Searching eV-scale sterile neutrino in Atmospheric Neutrino - PowerPoint PPT Presentation

Searching eV-scale sterile neutrino in Atmospheric Neutrino Experiments Jordi Salvado Advanced Workshop on Physics of Atmospheric Neutrinos - PANE 0

Atmospheric neutrinos where crucial (announced 1998) ◮ Proton decay experiments see neutrinos missing in some zenith directions: Takaaki Kajita ◮ Oscillation with small matter effect was the answer! atm | = 2 . 534 × 10 − 3 eV 2 | ∆ m 2 1

Neutrinos are massive! NuFIT 3.2 (2018) 2.8 31 2 2.6 2 ] D m H H 2.4 -3 eV 2.2 32 [10 -2.2 -2.4 2 D m -2.6 -2.8 0.3 0.4 0.5 0.6 0.7 360 2 q 23 sin 0.03 270 H ∆ m 2 sol = 7 . 50 × 10 − 5 eV 2 0.025 180 2 q 13 H sin d CP 0.02 | ∆ m 2 atm | = 2 . 534 × 10 − 3 eV 2 90 0.015 0 8.5 NuFIT 3.2 (2018) 8 2 ] -5 eV   0 . 799 → 0 . 844 0 . 516 → 0 . 582 0 . 141 → 0 . 156 7.5 21 [10 H H | U | 3 σ = 0 . 242 → 0 . 494 0 . 467 → 0 . 678 0 . 639 → 0 . 774   2 D m   7 0 . 284 → 0 . 521 0 . 490 → 0 . 695 0 . 615 → 0 . 754 6.5 0.2 0.25 0.3 0.35 0.4 0.015 0.02 0.025 0.03 2 q 12 2 q 13 [B. Kayser, hep-ph/0506165 (2004)] sin sin [Fig. from: Ivan Esteban et. al. JHEP 01 (2017) 087 www.nu-fit.org] [F.Capozzi et al. Arxiv:1804.09678] 2

Neutrino Oscillations H = 1 2 E UM 2 U † + V m M , V and U are 3 × 3 matrices. In two generations the oscillation probability at a given distance L and energy E in vacuum � L � � ∆ m 2 L � = 1 − sin 2 2 θ sin 2 P ν α → ν α E 4 E 1.0 ◮ sin 2 2 θ : oscillation amplitude 0.8 ◮ ∆ m 2 : oscillation frequency P ( ν µ → ν µ ) 0.6 ◮ L / E ≪ 1 / ∆ m 2 → no oscillations 0.4 ◮ L / E ∼ 1 / ∆ m 2 → ∆ m 2 =2 . 47 × 10 − 3 eV 2 oscillations 0.2 sin 2 2 θ =1 ◮ L / E ≫ 1 / ∆ m 2 → fast 0.0 oscillations ("averaged") 10 1 10 2 10 3 10 4 L/E [eV − 2 ] 3

E ∆ m 2 | ∆ m 2 LSND = 1 eV 2 Experiments: L osc = 2 π 10 23 10 7 Solar Potential L ⊙ Super-Kamiokande L atm IceCube 10 22 DeepCore LBNE 10 6 NO ν A T2K MINOS/OPERA/ICARUS 10 21 KamLAND K2K 10 5 L sterile L sterile L [GeV − 1 ] 10 20 10 4 L [m] DAE δ ALUS 10 19 Daya Bay 10 3 CCFR/NuTeV BNL-E776 Double Chooz MiniBooNE Palo Verde NOMAD/CHORUS 10 18 RENO MINER ν A 10 2 CDHS OscSNS LSND 10 17 Bugey 10 1 KARMEN 10 16 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 E ν [GeV] [modified from J.S. Diaz and V.A. Kostelecky, Phys.Lett. B700, 25 (2011)] 4

Why eV? The LSND experiment (90’s) ◮ The LSND experiment saw an excess of ¯ ν e over background. ◮ 3 . 8 σ signal. 5

More motivation: short baseline anomalies ν e oscillation with ∆ m 2 ∼ 1 eV 2 and ◮ LSND found ¯ ν µ → ¯ sin 2 2 θ ∼ 0 . 003 ◮ MiniBoone ν µ → ν e and ¯ ν µ → ¯ ν e appearance ◮ No significant excess at high energies (E > 475 MeV) ◮ Unexplained events at low energies, interpretation as oscillations similar to LSND: ∆ m 2 ∼ 1 eV 2 ◮ New result today! arxiv:1805.12028 4.5 σ 6.1 σ with LSND ◮ Gallium Anomaly, SAGE and GALLEX event rates lower than expected, can be explained by ν e disappearance with ∆ m 2 ≥ 1 eV 2 For a current global status: Mona Dentler et al. arXiv:1803.10661 S. Gariazzo, et.al., JHEP 06 (2017) 135 G. H. Collin, et al., Phys. Rev. Lett. 117, 221801 (2016) 6

More motivation: New data in reactors ◮ New reactor flux calculation (Mueller et al., 1101.2663, P. Huber, 1106.0687) 3% higher, tension in short-baseline ( L ≤ 100 m ) experiments. ◮ After the 5MeV bump we have new DANSS and NEOS results more independent of the flux calculation! Y. Ko et al., Phys. Rev. Lett. 118 (2017) M. Danilov, Moriond EW 2017 Mona Dentler et al. JHEP 1711 (2017) 099 7 C.Giunti, et al. JHEP 10 (2017) 143.

E ∆ m 2 | ∆ m 2 LSND = 1 eV 2 Experiments: L osc = 2 π 10 23 10 7 Solar Potential L ⊙ Super-Kamiokande L atm IceCube 10 22 DeepCore LBNE 10 6 NO ν A T2K MINOS/OPERA/ICARUS 10 21 KamLAND K2K 10 5 L sterile L sterile L [GeV − 1 ] 10 20 10 4 L [m] DAE δ ALUS 10 19 Daya Bay 10 3 CCFR/NuTeV BNL-E776 Double Chooz MiniBooNE Palo Verde NOMAD/CHORUS 10 18 RENO MINER ν A 10 2 CDHS OscSNS LSND 10 17 Bugey 10 1 KARMEN 10 16 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 E ν [GeV] [modified from J.S. Diaz and V.A. Kostelecky, Phys.Lett. B700, 25 (2011)] 8

Averaged ATM neutrinos � U ∗ | ν α � = α i | ν i � i The mixing matrix for n neutrino flavours can be decomposed as the product of n ( n − 1) / 2 rotations. U = V 3 n V 2 n V 1 n V 3( n − 1) V 2( n − 1) V 1( n − 1) · · · V 34 V 24 V 14 V 23 V 13 V 12 � �� � = U 0 with  cos( θ ij ) , a = b ∈ { i , j }     sin( θ ij ) e i δ ij ,  a = i , b = j    − sin( θ ij ) e − i δ ij , ( V ij ) ab = a = j , b = i    1 , a = b / ∈ { i , j }      0 , otherwise 9 Similar framework in Hisakazu Minakata talk

Averaged ATM neutrinos � � � � � � 1 − α Θ U ν 0 (1 − α ) U ν Θ U = U U 0 = = X Y 0 1 XU ν Y   α ee 0 0 α =  α µ e α µµ 0    α τ e α τµ α ττ whose components to leading order in the active-heavy mixing elements are given by  � n 1 i =4 | U β i | 2 , β = γ   2  � n α βγ ≃ i =4 U β i U ∗ γ i , β > γ    0 , γ > β 10

Averaged ATM neutrinos � � � � H 0 0 1 0 ˜ + V NC U † H = U 0 H 1 0 0 ˜ H 0 = H 0 + V NC (1 − α † )(1 − α ) ≃ H 0 − V NC ( α + α † ) � � � � H 0 = ∆ m 2 α ∗ − cos(2 θ 23 ) sin(2 θ 23 ) 2 α µµ ˜ 31 τµ − V NC 4 E sin(2 θ 23 ) cos(2 θ 23 ) α τµ 2 α ττ ◮ The averaged effect of sterile neutrinos is esencially a modification of the matter potential (NSI Arman Esmaili Talk) 11

eV steriles by SuperKamiokande and deepcore ◮ SuperKamikande and DC they both measure atmospheric neutrino oscillations and give a bound due to matter effects. ◮ eV is too heavy for this data samples to see oscillaitons, esencially a reparameterizaiton of the NSI result. K. Abe et al. (Super-Kamiokande Collaboration), Phys. Rev. D91, 052019 (2015). IceCube Collaboration, Phys. Rev. Lett.117 no. 7, (2016) 071801 12

Matter effects with the Sterile Neutrino at Earth � � ∆ m M 2 L P ν α → ν α = 1 − sin 2 2 θ M sin 2 4 E ν where θ M and ∆ m 2 M satisfy � ∆ m M 2 = (∆ m 2 cos 2 θ − A ) 2 + (∆ m 2 sin 2 θ ) 2 tan 2 θ tan 2 θ M = A 1 − ∆ m 2 cos 2 θ √ and A = ± 2 2 EG F N , N number density. Resonant flavor transition can happen if = ∓ cos 2 θ ∆ m 2 1 E res √ ν 2 N 2 G F this resonance can enhance the transition between active and sterile neutrinos. Talk by Alexei Smirnov 13

Matter effects with the Sterile Neutrino at Earth In the Earth , sterile neutrino with small mixing and ∆ m 2 = O (1 eV 2 ) the resonance happens when = ∆ m 2 cos 2 θ E res √ ∼ O ( TeV ) ν 2 2 G F N 1.0 ∆ m 2 41 =1 . 0eV 2 Oscillation Probability sin(2 θ 24 ) 2 =0 . 01 0.8 solid : ¯ ν dashed : ν 0.6 0.4 P(¯ ν µ → ¯ ν µ ) 0.2 P(¯ ν µ → ¯ ν τ ) P(¯ ν µ → ¯ ν s ) 0.0 10 2 10 3 10 4 10 5 10 6 E ν [GeV] M.V. Chizhov, S.T. Petcov. Phys.Rev. D63 (2001) 073003 H. Nunokawa et al. Phys.Lett. B562 (2003) 279-290 Sandhya Choubey JHEP 0712 (2007) 014 Barger et al.,Phys.Rev.D85:011302,(2012) Arman Esmaili et al. JCAP 1211 (2012) 041 14

Matter effects with the Sterile Neutrino at Earth ◮ TeV is in the center of the atmospheric data in IceCube. ◮ Other experiments are not sensitive at this energies. 15

The initial atmospheric neutrino flux The conventional atmospheric neutrino (muon) flux originates from the decay of π ± and K ± in the atmosphere. 10 -1 φ π 10 -2 φ K φ atm 10 -3 [a . u . ] cos( θ ) =0 . 1 10 -4 φ ν E 2 . 7 ν 10 -5 cos( θ ) = − 1 10 -6 10 -7 10 3 10 4 10 5 10 6 E ν [GeV] [Honda et al., Phys.Rev.D75:043006 (2007)] [Louis et al., Los Alamos Science Number 25 (1997)] we are improving, talks by Thomas K. Gaisser, Anatoli Fedynitch, Morihiro Honda 16

Neutrinos through the Earth The muon neutrinos come from different zenith angles ( θ z ) crossing different Earth layers core : cos θ z ∼ [ − 1 , − 0 . 8] mantle : cos θ z ∼ [ − 0 . 8 , − 0 . 1] crust : cos θ z > − 0 . 1 17

3+1 Oscillogram [Carlos Argüelles, J.S., C. Weaver. SQuIDS , CPC 2015.06.022.] https://github.com/jsalvado/SQuIDS https://github.com/arguelles/nuSQuIDS 18

Systematic errors Systematics are very important; some more than others . This are the systematics we considered: ◮ DOM efficiency ◮ Flux continuous parameters ◮ spectral index ◮ π /K ratio ◮ ν / ¯ ν ratio ◮ Air shower hadronic models ◮ Primary cosmic ray fluxes ◮ Hole Ice ◮ Neutrino cross sections ◮ Bulk ice scattering/absorption ◮ Earth model continuous systematics discrete systematic 19

How the fit looks ◮ We fitted the null hypothesis (no steriles) using the central sets (no variants) on the full 2D sample space. ◮ We recover a good fit and sensible nuisance parameters. Parameter Value Prior Normalization 1.02 No Prior ∆ γ 0.05 G(0.,0.05) DOMeff 0.985 No Prior π /K 1.10 G(1.,0.1) ν/ ¯ ν 1.0 G(1.,0.05) δ 0.001 G(0.,0.05) 20