Stefano Stefano Ga Gariazzo riazzo IFIC, Valencia (ES) CSIC - PowerPoint PPT Presentation

Stefano Stefano Ga Gariazzo riazzo IFIC, Valencia (ES) CSIC – Universitat de Valencia gariazzo@ific.uv.es http://ific.uv.es/~gariazzo/ Neutrino clustering Neutrino clustering in in the the Milky Milky Way Based on arxiv:170(6|7).[0-9]{5} In collaboration with P. F. de Salas, J. Lesgourgues, S. Pastor 20/06/2017 - WIN2017 - UCI Irvine

Cosmic neutrino background and neutrino clustering 1 Neutrinos in the early universe PTOLEMY Neutrino clustering Matter distributions in the Milky Way 2 Dark Matter Baryons 3 The local neutrino overdensity Results for (nearly) minimal neutrino masses Results for non-minimal neutrino masses: 150 meV Conclusions 4

Cosmic neutrino background and neutrino clustering 1 Neutrinos in the early universe PTOLEMY Neutrino clustering Matter distributions in the Milky Way 2 Dark Matter Baryons 3 The local neutrino overdensity Results for (nearly) minimal neutrino masses Results for non-minimal neutrino masses: 150 meV Conclusions 4

History of the universe neutrino decoupling C ν B at T ∼ O (MeV) due to insufficient ν e ↔ ν e & e − e + ↔ ν ¯ ν T ν ≃ (4 / 11) 1 / 3 T γ after e − e + annihilation T ν, 0 = 1 . 945 K ≃ 1 . 676 × 10 − 4 eV � E ν � ≃ 3 . 1 T ν, 0 ≃ 5 × 10 − 4 eV ν, 0 ≃ n 0 = n ν, 0 = n ¯ 56 cm − 3 per family BBN CMB S. Gariazzo “ Neutrino clustering in the Milky Way ” WIN2017 - 20/6/17 1/14

History of the universe neutrino decoupling C ν B at T ∼ O (MeV) ∃ at least 2 mass eigenstates with due to insufficient � � � ∆ m 2 m i � 8 meV = > � E ν � ν e ↔ ν e & e − e + ↔ ν ¯ ν sol T ν ≃ (4 / 11) 1 / 3 T γ after e − e + annihilation many relic neutrinos are T ν, 0 = 1 . 945 K ≃ non-relativistic today! 1 . 676 × 10 − 4 eV � E ν � ≃ 3 . 1 T ν, 0 ≃ 5 × 10 − 4 eV ν, 0 ≃ n 0 = n ν, 0 = n ¯ 56 cm − 3 per family BBN CMB S. Gariazzo “ Neutrino clustering in the Milky Way ” WIN2017 - 20/6/17 1/14

[Long et al., JCAP 08 (2014) 038] C ν B: Dirac vs Majorana Majorana neutrinos Dirac neutrinos active: sterile: active: sterile: ν R , n ( ν R ) ≃ 0 ν L , n ( ν L ) = n 0 ν L , n ( ν L ) = n 0 N L , n ( N L ) = 0 ν R , n (¯ ¯ ν R ) = n 0 ν L , n (¯ ¯ ν L ) ≃ 0 ν R , n ( ν R ) = n 0 N R , n ( N R ) = 0 total: n C ν B ≃ 6 n 0 total: n C ν B ≃ 6 n 0 NOTE: free-streaming conserves helicity, not chirality! because neutrinos are massive and become non-relativistic during expansion n ( ν h L ) = n 0 n ( ν h R ) ≃ 0 n ( ν h L ) = n 0 n ( N h L ) = 0 ν h L ) ≃ 0 n (¯ ν h R ) = n 0 n (¯ n ( ν h R ) = n 0 n ( N h R ) = 0 only left-helical! both left and right-helical if not completely free-streaming, helicities can be flipped ⇒ mix of helicities: n ( ν h L ) = no change for Majorana n (¯ ν h R ) = n ( ν h R ) = n (¯ ν h L ) = n 0 / 2 S. Gariazzo “ Neutrino clustering in the Milky Way ” WIN2017 - 20/6/17 2/14

Relic neutrinos in cosmology: N eff Radiation energy density ρ r in the early Universe: � 4 � � 4 / 3 � 1 + 7 ρ r = N eff ρ γ = [1 + 0 . 2271 N eff ] ρ γ 8 11 ρ γ photon energy density, 7 / 8 is for fermions, (4 / 11) 4 / 3 due to photon reheating after neutrino decoupling N eff → all the radiation contribution not given by photons N eff ≃ 1 correspond to a single family of active neutrino, in equilibrium in the early Universe Active neutrinos: N eff = 3 . 046 [Mangano et al., 2005] (damping factors approximations) ∼ N eff = 3 . 045 [de Salas et al., 2016] (full collision terms) due to not instantaneous decoupling for the neutrinos + Non Standard Interactions: 3 . 040 < N eff < 3 . 059 [de Salas et al., 2016] Observations: N eff ≃ 3 . 04 ± 0 . 2 [Planck 2015] Indirect probe of cosmic neutrino background! S. Gariazzo “ Neutrino clustering in the Milky Way ” WIN2017 - 20/6/17 3/14

[Long et al., JCAP 08 (2014) 038] Direct detection of C ν B neutrinos At least two C ν B neutrinos over three are non-relativistic now! How to detect non- a process without energy relativistic neutrinos? threshold is necessary [Weinberg, 1962] : neutrino capture in β –decaying nuclei ν + n → p + e − signal is a peak at 2 m ν � m 4 Electron Spectrum � d � � dE e � above β –decay endpoint � m Ν � m Ν C Ν B Β� decay endpoint � K end � only with a lot of material K end 0 � 18.6 keV Sterile Ν need a very good energy resolution Good candidate: tritium Electron Kinetic Energy � K e � (high cross section of (good availability of 3 H ) (low Q − value) + + ν + 3 H → 3 He + e − ) S. Gariazzo “ Neutrino clustering in the Milky Way ” WIN2017 - 20/6/17 4/14

[Long et al., JCAP 08 (2014) 038] PTOLEMY [Betts et al., arxiv:1307.4738] Princeton Tritium Observatory for Light, Early- universe, Massive-neutrino Yield (PTOLEMY) expected resolution ∆ ≃ 0 . 1 eV built only for C ν B M T = 100 g atomic tritium can probe m ν ≃ 1 . 4∆ ≃ 0 . 14 eV (must distinguish C ν B events from β -decay ones) 3 � | U ei | 2 [ n i ( ν h R ) + n i ( ν h L )] N T ¯ Γ C ν B = σ i =1 σ = ≃ 3 . 834 × 10 − 45 cm 2 number of 3 H nuclei in a sample of mass M T N T ¯ n i number density of neutrino i Majorana: Dirac: (without clustering) 3 3 | U ei | 2 � � n 0 �� | U ei | 2 [2 ( n 0 )] N T ¯ � � Γ D σ ≃ 4 yr − 1 Γ M σ ≃ 8 yr − 1 C ν B = 2 N T ¯ C ν B = 2 i =1 i =1 Γ M C ν B = 2Γ D C ν B S. Gariazzo “ Neutrino clustering in the Milky Way ” WIN2017 - 20/6/17 5/14

[Long et al., JCAP 08 (2014) 038] PTOLEMY [Betts et al., arxiv:1307.4738] Princeton Tritium Observatory for Light, Early- universe, Massive-neutrino Yield (PTOLEMY) expected resolution ∆ ≃ 0 . 1 eV built only for C ν B M T = 100 g atomic tritium can probe m ν ≃ 1 . 4∆ ≃ 0 . 14 eV ehnancement from ν clustering in the galaxy? (must distinguish C ν B events from β -decay ones) 3 � | U ei | 2 [ n i ( ν h R ) + n i ( ν h L )] N T ¯ Γ C ν B = σ i =1 σ = ≃ 3 . 834 × 10 − 45 cm 2 number of 3 H nuclei in a sample of mass M T N T ¯ n i number density of neutrino i Majorana: Dirac: (without clustering) 3 3 | U ei | 2 � � n 0 �� | U ei | 2 [2 ( n 0 )] N T ¯ � � Γ D σ ≃ 4 yr − 1 Γ M σ ≃ 8 yr − 1 C ν B = 2 N T ¯ C ν B = 2 i =1 i =1 Γ M C ν B = 2Γ D C ν B S. Gariazzo “ Neutrino clustering in the Milky Way ” WIN2017 - 20/6/17 5/14

[arxiv:170(6|7).[0-9]{5}] ν clustering with N-one-body simulations Milky Way (MW) matter attracts neutrinos! 3 | U ei | 2 f c ( m i ) [ n i , 0 ( ν h R ) + n i , 0 ( ν h L )] N T ¯ � clustering Γ C ν B = σ i =1 f c ( m i ) clustering factor How to compute it? Idea from [Ringwald & Wong, 2004] N-one-body= N × single ν simulations → each ν evolved from initial conditions at z = 3 Assumptions: → spherical symmetry, coordinates ( r , θ , p r , l ) → need ρ matter ( z ) = ρ DM ( z ) + ρ baryon ( z ) ν s are independent only gravitational interactions how many ν s is “N”? ν s do not influence matter evolution ( ρ ν ≪ ρ DM ) → must sample all possible r , p r , l → must include all possible ν s that reach the MW (fastest ones may come from given N ν : several (up to O (100)) Mpc!) → weigh each neutrinos → reconstruct final density profile with kernel method from [Merritt&Tremblay, 1994] S. Gariazzo “ Neutrino clustering in the Milky Way ” WIN2017 - 20/6/17 6/14

Cosmic neutrino background and neutrino clustering 1 Neutrinos in the early universe PTOLEMY Neutrino clustering Matter distributions in the Milky Way 2 Dark Matter Baryons 3 The local neutrino overdensity Results for (nearly) minimal neutrino masses Results for non-minimal neutrino masses: 150 meV Conclusions 4

[arxiv:170(6|7).[0-9]{5}] Dark matter: profiles today NFW profile: Einasto (EIN) profile: � α − 1 � − 3+ γ = � − γ � � �� �� � − 2 r r 1 + r = N Ein exp ρ DM ( r ) N NFW α r s r s r s N Ein = ρ Ein ( r s ) N NFW = 2 3 − γ ρ NFW ( r s ) normalization N Ein , r s , α parameters N NFW , r s , γ 4.0 4.0 NFW EIN Earth position Earth position 3.5 3.5 best-fit best-fit ρ dm [GeV/cm 3 ] ρ dm [GeV/cm 3 ] 3.0 3.0 optimistic optimistic 2.5 2.5 2.0 2.0 1.5 1.5 1.0 1.0 0.5 0.5 0.0 0.0 5 10 15 20 25 5 10 15 20 25 r [kpc] r [kpc] Best-fit profiles optimistic: close to 2 σ upper limits fit of data points from [Pato & Iocco, 2015] S. Gariazzo “ Neutrino clustering in the Milky Way ” WIN2017 - 20/6/17 7/14