Neutrinos secretly converting to lighter particles to please both KATRIN and Cosmos. Yasaman Farzan IPM, Tehran

Transcription

1 Neutrinos secretly converting to lighter particles to please both KATRIN and Cosmos Yasaman Farzan IPM, Tehran

2 Outline Motivation for the KATRIN experiment Effect of neutrinos on cosmological scales and the cosmological bound on neutrino mass Our scenario to reconcile cosmological bounds with sizable [O(0.1 ev)] neutrino mass Embedding scenario in electroweak invariant models Results Summary

3 Neutrino oscillation i!e i R H dt i H = H vac + H mat H vac = U Diag( m2 1 2p, m2 2 2p, m2 3 2p ) U PMNS unitary matrix H mat = Diag( p 2G F (N e N n /2), p 2GF N n /2, p 2GF N n /2)

4 No sensitivity to neutrino mass scale Neutrino oscillation pattern depends only on neutrino mass splitting m 2 ij

5 Neutrinoless double beta decay m ee = m 1 U 2 e1 + m 2 U 2 e2 + m 3 U 2 e3 = m 1 U e1 2 e i 1 + m 2 U e2 2 e i 2 + m 3 U e3 2 e i 3+2

6 Beta decay experiments 3 H! 3 He + e + e

7 Which mass? m e = s X i m 2 i U ei 2 m e = X i m i U ei 2 Equal up to m 2 m 2 2 Y.F. and Smirnov, PLB557 (2003)

8 Previous experiments Mainz J Bonn et al, Nuc Phys Supp 91 (2001) 273 m < 2.2 ev 95 % C.L. Troitsk Troistk collaboration, PRD (2011)

9 KArlsruhe TRItium decay Neutrino experiment (KATRIN)

10 Reach of KATRIN Bound in case of null result 0.2 ev 90 % C.L. Detection limit 0.35 ev at 5

11 KATRIN spectrometer

12 OLD happy days before WMAP m ee m 1 from neutrino less double beta decay from KATRIN Information on Majorana phases

13 PLANCK

14 J. Lesgourgues and S. Pastor, Neutrino mass from cosmology, Adv High Energy Phys 2012 (2012) ; arxiv:

15 Neutrino effect on structure formation free streaming wavelength and wavenumber Neutrinos starting to become non-relativistic m = hpi T 1+z = m 1 ev

16 effects of neutrino mass on matter power spectrum Back reaction gravitational potential

17 Effects of neutrino mass on CMB At the time of recombination neutrinos were relativistic. Thus, their effect on CMB will be secondary and indirect through three main effects. Let us fix. The will then depend on m z eq neutrino mass and this affects position and amplitude of CMB power spectrum peaks.

18 Fixing m, the angular diameter distance to the last scattering surface d A (z dec) varies with neutrino mass which in turn will affect the CMB spectrum feature in multipole space. Neutrino mass affects time evolution of matter fluctuation at late time and therefore affects Integrated Sachs-Wolfe effect, changing the slope of low-l part of CMB power spectrum.

19

20 Planck alone X m i < 0.71 ev i Planck + BAO X m i < 0.23 ev i Ade et al (Planck collaboration), arxiv:

21 Is there any hope for KATRIN? Altering cosmology Non-standard physics for neutrinos

22 Y.F and Steen Hannestad, Neutrinos secretly converting to lighter particles to please both KATRIN and the cosmos, JCAP 1602 (2016) no.02, 058

23 Conditions Conversion has to be after neutrino decoupling: Below T 1 MeV. During recombination neutrinos and the new particles have to freely stream. Hannestad and Raffelt, PRD 72 (2005)

24 Conversion should take place when

25 Mechanisms for conversion Neutrino-Neutrino coannihilation Neutrino scattering off dark matter background

26 Neutrino mass coannihilation Mass of intermediate state is much higher than the temperature ann T 5 m 4 X H T 2 M Pl Mass of the intermediate state is much smaller than the temperature ann T H T 2 M Pl

27 Resonant conversion ev <m X < 1 MeV

28 Conversion rate depends on properties of intermediate state

29 Scalar vs Vector Scalar intermediate state Vector intermediate state

30 Narrow width approximation

31

32 Condition for efficient conversion No dependence on the coupling of the new light particles to X as long as Z 0 m Z 0 g a,g 0 e 0 a <g s,g 0 e 0 s < 0.1 p 2

33

34 The maximum of R/H is reached at T p 2 m X Maximum R H / M Pl m X

35 Back reaction Reaction and back-reaction rate equal similar energy distribution number of degrees of freedom that come to equilibrium with neutrinos below 1MeV

36 Differently possibility X directly decays to more than one species. Secondary particles decay to new particles. Secondary particles oscillate to new particles.

37 Effective number of neutrinos Effective number of relativistic degrees of freedom at BBN Effective number of relativistic degrees of freedom at recombination Effective number of massive neutrinos after conversion

38 Gauge boson as X Star cooling sets a bound on coupling to electron of order of

39 Arias et al., JCAP 1206 (2012) Horizontal branch

40 Gauge boson as X Gauging L µ L Stueckelberg or

41 Majoron model

42 Mixing between triplet and singlet Is hierarchy between masses of Majoron and the triplet stable?

43 Other bounds Supernova cooling YF, Phys.Rev. D67 (2003) Free streaming at recombination

44 Parameters relevant for cosmology Neutrino mass Effective number of massive neutrinos

45 68% and 95%

46 If for each active neutrino there are 1 (4)lighter ones, m =0.35 ev

47 Summary Scenarios that resonantly convert neutrinos to lighter particles during T m X kev Intermediate state can be scalar or vector boson Gauging L µ L or mixing singlet-triplet scalar Masses resolvable by KATRIN can be made compatible within this scenario with cosmological bounds.

48 Backup

49

50 Normal hierarchical scheme X m i Min ' q m 2 atm ' 0.06 ev i Suppression of small scale fluctuations of order of few percent to be resolved by EUCLID