A Flavor and Spectral Analysis of the Ultra-High Energy Neutrino - PowerPoint PPT Presentation

A Flavor and Spectral Analysis of the Ultra-High Energy Neutrino Events at IceCube P . S. Bhupal Dev Consortium for Fundamental Physics, The University of Manchester, United Kingdom C.-Y. Chen, PSBD and A. Soni, Phys. Rev. D 89 , 033012 (2014) [arXiv:1309.1764 [hep-ph]]; arXiv:1411.5658 [hep-ph]. Institute of Physics Bhubaneswar, India December 15, 2014

Outline UHE Events at IceCube Sources and Interactions SM Predictions Implications for New Physics A New Astrophysical Flux Conclusion

Neutrinos: Friends across 20 orders of Magnitude [J. A. Formaggio and G. P . Zeller, Rev. Mod. Phys. 84 , 1307 (2012)] + 2

Neutrino Flux Neutrinos as probes of the HE Universe S.Klein, F. Halzen, Phys. Today, May 2008 B !

High-energy Neutrinos: Astrophysical Messengers

(Ultra) High-energy Neutrino Detectors (Telescopes) Super-Kamiokande, Baksan, Lake Baikal, ANTARES, AMANDA, IceCube , KM3Net,...

Neutrino Detection at IceCube μ Cherenkov cone ν μ Cherenkov radiation from secondary particles (muons, electrons, hadrons). Within the SM, neutrino interacts with matter only via weak ( W and Z ) gauge bosons. � ℓ + X ( CC ) ν ℓ + N → ν ℓ + X ( NC ) CC electromagnetic/NC hadronic CC tau ‘double bang’ CC Muon track (data) cascade shower (data) (simulation only)

First Observation of UHE Neutrinos p ~1.1PeV ~1.2PeV “Ernie” “Bert” 3 10 data sum of atmospheric background -8 -1 E 2 = 3.6x10 GeV sr cm -2 s -1 atmospheric µ φ 2 10 cosmogenic ν Yoshida atmospheric ν conventional cosmogenic ν Ahlers atmospheric ν prompt 10 Number of events 1 -1 10 -2 10 -3 10 -4 10 -5 10 4.5 5 5.5 6 6.5 7 7.5 log NPE 10

Follow-Up Analysis “St 26 more events between 20-300 TeV. Total 28 events in 662 days of data with 4 . 1 σ excess over expected atmospheric background (10 . 6 + 5 . 0 − 3 . 6 events). 21 cascade events and 7 muon tracks.

With 3-year Dataset [Phys. Rev. Lett. 113 , 101101(2014)] E = 1.0 PeV ! θ = 62 o ! E = 2.0 PeV ! θ = 34 o E = 1.1 PeV ! θ = 23 o ! 9 more events, including one at 2 PeV (“Big Bird"). Total 37 events in 988 days of data with 5 . 7 σ excess over expected atmospheric background of 6 . 6 + 5 . 9 − 1 . 6 atmospheric neutrinos and 8 . 4 ± 4 . 2 cosmic ray muons. 28 cascade events and 9 muon tracks.

� � Understanding the Events Two main theoretical aspects: Source (astrophysics): flux and flavor composition Interaction (particle physics): showers and tracks Most plausible source: Astrophysical with a power-law flux Φ( E ν ) = CE − s . ν A t A m E 2 d � /dE [GeV cm -2 s -1 sr -1 ] t 10 -7 m . C . o C n o v n Possible Source N(1 − 2 PeV) N(2 − 10 PeV) . v � e . � µ IC40 U.L. EHE search Atm. Conv. [45, 46] 0.0004 0.0003 10 -8 IC40 � µ U.L. Cosmogenic–Takami [48] 0.01 0.2 E -2 Cosmogenic–Ahlers [49] 0.002 0.06 Takami Ahlers Atm. Prompt [47] 0.02 0.03 10 -9 Astrophysical E − 2 0.2 1 Astrophysical E − 2 . 5 0.08 0.3 Astrophysical E − 3 0.03 0.06 Atm. Prompt � µ 10 -10 10 4 10 5 10 6 10 7 10 8 10 9 10 10 E [GeV] [R. Laha, J. F. Beacom, B. Dasgupta, S. Horiuchi and K. Murase, Phys. Rev. D 88 , 043009 (2013)]

Flavor Composition Primary production mechanisms for astrophysical neutrinos: × • pγ process: pγ → ∆ + → nπ + → ne + ν e ¯ ν µ ν µ ; • pp process: pp → π ± /K ± + 2 p/n → µν µ + 2 p/n → eν e ¯ ν µ ν µ + 2 p/n ; • pn process: pn → π ± /K ± + 2 p/n → µν µ + 2 p/n → eν e ¯ ν µ ν µ + 2 p/n . Predict a flavor ratio of ( ν e : ν µ : ν τ ) = (1:2:0) at source. Given a flavor ratio ( f 0 e : f 0 µ : f 0 τ ) S , the corresponding value ( f e : f µ : f τ ) E on Earth is given by 3 � � | U ℓ i | 2 | U ℓ ′ i | 2 f 0 � P ℓℓ ′ f 0 f ℓ = ℓ ′ ≡ ℓ ′ . ℓ ′ = e ,µ,τ i = 1 ℓ ′ For the current values of the 3-neutrino oscillation parameters, we get (1:1:1) E at Earth.

Possible (New Physics) Interactions Several exotic phenomena have been invoked to explain the IceCube events, e.g. Decaying (PeV-scale) Dark Matter. [B. Feldstein, A. Kusenko, S. Matsumoto and T. T. Yanagida, Phys. Rev. D 88 , 015004 (2013); A. Esmaili and P . D. Serpico, JCAP 1311 , 054 (2013)] Secret neutrino interactions involving a light mediator [K. Ioka and K. Murase, PTEP 2014 , 061E01 (2014); K. C. Y. Ng and J. F. Beacom, Phys. Rev. D 90 , 065035 (2014)] Resonant production of TeV-scale leptoquarks. [V. Barger and W.-Y. Keung, Phys. Lett. B 727 , 190 (2013)] Decay of massive neutrinos to lighter ones over cosmological distance scales [ P . Baerwald, M. Bustamante and W. Winter, JCAP 1210 , 020 (2012); S. Pakvasa, A. Joshipura and S. Mohanty, Phys. Rev. Lett. 110 , 171802 (2013)] Pseudo-Dirac neutrinos oscillating to sterile ones in a mirror world [A. S. Joshipura, S. Mohanty and S. Pakvasa, Phys. Rev. D 89 , 033003 (2014)] Superluminal neutrinos and Lorentz invariance violation [F. W. Stecker and S. T. Scully, Phys. Rev. D 90 , 043012 (2014); L. A. Anchordoqui, V. Barger, H. Goldberg, J. G. Learned, D. Marfatia, S. Pakvasa, T. C. Paul and T. J. Weiler, Phys. Lett. B 739 , 99 (2014)]

This Talk Before embarking on BSM explanations, desirable to know the SM expectation with better accuracy. Include known sources of theoretical uncertainty (mainly from PDFs). Include realistic detector effects (e.g., effective number of target nucleons, attenuation effects, energy loss). Find the event rate for SM interactions, assuming an isotropic astrophysical, power-law flux. Compare the SM predictions with the IceCube data. Any statistically significant deviations from the SM prediction might call for BSM! In the absence of significant deviations, could use the data to constrain various BSM scenarios.

SM Neutrino-Nucleon Interactions Differential cross sections: [R. Gandhi, C. Quigg, M. H. Reno and I. Sarcevic, Astropart. Phys. 5 , 81 (1996)] � 2 � d 2 σ CC 2 G 2 � M 2 F M N E ν q ( x , Q 2 )( 1 − y ) 2 � ν N W xq ( x , Q 2 ) + x ¯ = , Q 2 + M 2 dxdy π W � 2 � � d 2 σ NC G 2 M 2 F M N E ν q 0 ( x , Q 2 )( 1 − y ) 2 � ν N Z xq 0 ( x , Q 2 ) + x ¯ = , Q 2 + M 2 dxdy 2 π Z where x = Q 2 / ( 2 M N yE ν ) (Bjorken variable), and y = ( E ν − E ℓ ) / E ν (inelasticity).

Parton Distribution Functions q ( q 0 , ¯ q 0 ) are respectively the quark and anti-quark density distributions in a proton, q , ¯ summed over valence and sea quarks of all flavors relevant for CC (NC) interactions: u + d q = + s + b , 2 u + ¯ ¯ d ¯ q = + c + t , 2 u + ¯ d ) + ¯ u + d d q 0 ( L 2 u + L 2 ( R 2 u + R 2 d ) + ( s + b )( L 2 d + R 2 d ) + ( c + t )( L 2 u + R 2 = u ) , 2 2 u + ¯ d ) + ¯ u + d d q 0 ( R 2 u + R 2 ( L 2 u + L 2 d ) + ( s + b )( L 2 d + R 2 d ) + ( c + t )( L 2 u + R 2 ¯ = u ) , 2 2 with L u = 1 − ( 4 / 3 ) x W , L d = − 1 + ( 2 / 3 ) x W , R u = − ( 4 / 3 ) x W and R d = ( 2 / 3 ) x W (where x W = sin 2 θ W , and θ W is the weak mixing angle). Higher E ν means probing smaller x -regions (DIS). The PDFs must include the lowest possible x -grids (up to ∼ 10 − 9 extracted so far from HERA data). We used NNPDF2.3 [R. D. Ball et al. , Nucl. Phys. B 867 , 244 (2013)] .

Differential Cross Sections E Ν � 1 PeV 10 � 30 NNPDF2 .3 10 � 31 d Σ � cm 2 �� dx 10 � 32 Ν N CCLO Ν N CCNLO Ν N CCNNLO 10 � 33 Ν� NC LO Ν N NC NLO Ν N NC NNLO 10 � 6 10 � 5 10 � 4 0.001 0.01 0.1 1 x [C.-Y. Chen, PSBD and A. Soni, Phys. Rev. D 89 , 033012 (2014)]

Differential Cross Sections 10 � 32 10 � 33 Ν N CCLO d Σ � cm 2 �� dy Ν N CCNLO Ν N CCNNLO Ν� NC LO Ν N NC NLO 10 � 34 Ν N NC NNLO Ν e CCLO 10 � 35 E Ν � 1 PeV NNPDF2 .3 10 � 36 10 � 8 10 � 6 10 � 4 0.01 1 y [C.-Y. Chen, PSBD and A. Soni, Phys. Rev. D 89 , 033012 (2014)]

Total Cross Sections Ν� CC 10 � 31 Ν� CC Ν� NC Ν� NC 10 � 32 Ν e e Σ � cm 2 � 10 � 33 10 � 34 10 � 35 10 � 36 10 4 10 5 10 6 10 7 10 100 1000 E Ν � TeV �

Glashow Resonance Resonant production of W − in ¯ ν e e − scattering: [S. Glashow, Phys. Rev. 118 , 316 (1960)] ν e + e − → W − → anything ¯ � 1 − 2 meE ν / M 2 �   Le W 1 + G 2 R 2 e + L 2 e ( 1 − y ) 2 1 + 2 meE ν y / M 2 d σ ¯ F m e E ν   ν ee → ¯ ν ee � 2 + 4 ( 1 − y ) 2 Z   = ,  � 2 + Γ 2  dy 2 π � �  1 + 2 m e E ν y / M 2 1 − 2 m e E ν / M 2 W / M 2    Z W W where L e = 2 x W − 1 and R e = 2 x W are the chiral couplings of Z to electron. Peak is at energy E ν = m 2 W / ( 2 m e ) = 6 . 3 PeV.