Lepton Number Violation and the Baryon Asymmetry of the Universe

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1 Lepton Number Violation and the Baryon Asymmetry of the Universe ILP / LPTHE Paris ACFI Workshop, F. Deppisch, L. Graf, JH, W. Huang, arxiv: F. Deppisch, JH, W. Huang, M. Hirsch, H. Päs, Phys. Rev. D92 (2015) F. Deppisch, JH, M. Hirsch, PRL 112 (2014)

2 How can we probe Baryogenesis models? 2

3 Baryogenesis via Leptogenesis generation of lepton asymmetry via heavy neutrino decays competition with lepton number violating (LNV) washout processes conversion to baryon asymmetry via sphaleron processes at source of CP violation L N N N H H N H L N Q N L u L L N Q H sphaleron processes H L H u L N L scattering processes H H L H L N H H L washoutn L L processes H H washout processes 3

4 How can we test what generates the BAU? baryon asymmetry SM processes lepton asymmetry Mechanism of CP violation washout processes LHC neutrinoless double beta decay experiments 4

5 LNV at 0vbb decay experiments 5

6 Neutrinoless double beta decay (0vbb) Most stringent limits are currently from GERDA and Kamland-Zen: 6

7 Neutrinoless double beta decay (0vbb) standard mass mechanism long range contribution short range contribution? = Most stringent limits are currently from GERDA and Kamland-Zen: The inverse half life can be expressed in terms of effective couplings: 7

8 Neutrinoless double beta decay (0vbb) long range contribution Long range contribution:? = Leptonic and hadronic current with different chirality structure: with 8

9 Possible underlying LNV operators standard mass mechanism long range contribution short range contribution? = possibilities at tree level: possibilities at loop level: 9

10 Constraining the effective operator scale If 0vββ is observed, the scale of the underlying operator can be determined 10

11 Lepton Asymmetry Washout LNV operator would cause washout of pre-existing net lepton asymmetry in the early Universe operator specific factor washout efficient if lepton density If 0vßß is observed, washout efficient in the temperature interval 11

12 Impact on Baryogenesis models scale of operator scale above which a maximal lepton asymmetry of 1 is washout out to the observed baryon asymmetry (or less) scale above which washout is highly effective If was observed via non-standard mechanism, resulting washout would rule out baryogenesis mechanisms above However: 0vßß decay probes only electron component of LNV operators: 12

13 Extending the impact with LFV Most stringent limits on LFV set by 6-dim operators Determine interval in which LFV process equilibrate pre-existing flavour asymmetry IF LFV processes are observed as well, loophole of asymmetry being stored in another flavour sector is ruled out 13

14 Distinguishing between different operators SuperNEMO will be able to discriminate O7 from others, due to e-r and e+l in the final state potential discrepancy between neutrino mass (cosmology) and 0vbb half live measurement could be an indication for 0vbb triggered by non-standard mechanism distinguishing between different mechanisms via measurements in different isotopes observation of 0vββ via O9 and O11 will imply observation of LNV at LHC 14

15 The full picture BUT: There are 129 LNV operators... 7-dim 9-dim 11-dim 15

16 The full picture 7-dim 9-dim 11-dim 16

17 Impact of sensitivity on effective couplings 17

18 The full picture 7-dim 9-dim 11-dim 18

19 Competition between long- and short-range Short-range contribution: Long-range contribution: long range only short range only only first generation Yukawa couplings 19

20 Competition between long- and short-range Short-range contribution: Long-range contribution: long range only short range only allow third generation Yukawa couplings 20

21 The full picture 7-dim 9-dim 11-dim first generation only 21

22 The full picture 7-dim 9-dim 11-dim incl. third generation 22

23 Comparison with mass mechanism first generation only 23

24 Comparison with mass mechanism 7-dim 9-dim 11-dim incl. third generation 24

25 Validity of the effective operator approach with 25

26 LNV at the LHC 26

27 LNV at the LHC signature: cross section in early universe determines washout strength cross section possibly measured at LHC Observable LNV signal at LHC and corresponding resonant mass can be directly related to baryon asymmetry washout 27

28 LNV at the LHC Assuming pre-existing lepton asymmetry generated at high scale Observation of LNV process at the LHC implies a strong washout that it excludes leptogenesis models that generate an asymmetry above Mx 28

29 LNV at the LHC NOW: assumption that CP-asymmetry є is created at scale MN scale of CP-asymmetry generation scale of LNV observation observation of LNV process at the LHC excludes high-scale baryogenesis models sets lower limit on the baryon asymmetry of a low-scale leptogenesis model 29

30 LNV at the LHC NOW: assumption that CP-asymmetry є is created at scale MN not possible to generate large enough baryon asymmetry at all lower limit on CP-asymmetry observation of LNV process at the LHC excludes high-scale baryogenesis models sets lower limit on the baryon asymmetry of a low-scale leptogenesis model 30

31 Conclusions LNV processes are of high interest with respect to baryogenesis tight connection of high intensity and energy frontier possibility to falsify / probe BG models! 31