Lepton Number Violation and the Baryon Asymmetry of the Universe - - PowerPoint PPT Presentation

Lepton Number Violation and the Baryon Asymmetry of the Universe

Julia Harz ACFI Workshop, 29.03.2018 ILP / LPTHE Paris

F . Deppisch, L. Graf, JH, W. Huang, arxiv:1711.10432 F . Deppisch, JH, W. Huang, M. Hirsch, H. Päs, Phys. Rev. D92 (2015) 036005 F . Deppisch, JH, M. Hirsch, PRL 112 (2014) 221601

LNV and the Baryon Asymmetry of the Universe 2 Julia Harz

How can we probe Baryogenesis models?

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• generation of lepton asymmetry via heavy neutrino decays
• competition with lepton number violating (LNV) washout processes
• conversion to baryon asymmetry via sphaleron processes at

Baryogenesis via Leptogenesis

H N L Q u H N u L Q N L H L H N N L H N L H N H L

washout processes

N L H L H N L L H H N L H H L

washout processes source of CP violation sphaleron processes scattering processes

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How can we test what generates the BAU?

baryon asymmetry lepton asymmetry SM processes washout processes Mechanism of CP violation

LHC neutrinoless double beta decay experiments

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LNV at 0vbb decay experiments

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Neutrinoless double beta decay (0vbb)

Most stringent limits are currently from GERDA and Kamland-Zen:

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Neutrinoless double beta decay (0vbb)

Most stringent limits are currently from GERDA and Kamland-Zen: The inverse half life can be expressed in terms of efgective couplings:

= ?

standard mass mechanism long range contribution short range contribution

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Neutrinoless double beta decay (0vbb)

Long range contribution:

= ?

long range contribution

with

Leptonic and hadronic current with difgerent chirality structure:

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Possible underlying LNV operators

= ?

standard mass mechanism long range contribution short range contribution

possibilities at tree level: possibilities at loop level:

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Constraining the efgective operator scale

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

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Lepton Asymmetry Washout

• LNV operator would cause washout of pre-existing net

lepton asymmetry in the early Universe

• washout effjcient if

If 0vßß is observed, washout effjcient in the temperature interval

• perator specifjc factor

lepton density

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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 efgective However: 0vßß decay probes only electron component of LNV

• perators:

If was observed via non-standard mechanism, resulting washout would rule out baryogenesis mechanisms above

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Extending the impact with LFV

• Most stringent limits on LFV set by 6-dim
• perators
• Determine interval in which LFV process

equilibrate pre-existing fmavour asymmetry IF LFV processes are observed as well, loophole of asymmetry being stored in another fmavour sector is ruled out

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Distinguishing between difgerent operators

• SuperNEMO will be able to discriminate O7 from others, due to e-

R and e+ L in the fjnal state

• distinguishing between difgerent mechanisms via measurements in

difgerent isotopes

• potential discrepancy between neutrino mass (cosmology) and 0vbb

half live measurement could be an indication for 0vbb triggered by non-standard mechanism

• observation of 0vββ via O9 and O11 will imply observation of LNV at LHC

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The full picture

7-dim 9-dim 11-dim

BUT: There are 129 LNV operators...

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The full picture

7-dim 9-dim 11-dim

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Impact of sensitivity on efgective couplings

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The full picture

7-dim 9-dim 11-dim

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Competition between long- and short-range

long range

• nly

Short-range contribution: Long-range contribution:

short range

• nly
• nly first generation Yukawa couplings

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Competition between long- and short-range

long range

• nly

Short-range contribution: Long-range contribution:

short range

• nly

allow third generation Yukawa couplings

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The full picture

7-dim 9-dim 11-dim

first generation only

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The full picture

7-dim 9-dim 11-dim 7-dim 9-dim 11-dim

• incl. third generation

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Comparison with mass mechanism

first generation only

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7-dim 9-dim 11-dim 7-dim 9-dim 11-dim

• incl. third generation

Comparison with mass mechanism

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Validity of the efgective operator approach

with

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LNV at the LHC

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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

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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

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LNV at the LHC

• NOW: assumption that CP-asymmetry є is created at scale MN

scale of CP-asymmetry generation scale of LNV observation

• bservation of LNV process at the LHC
• excludes high-scale baryogenesis models
• sets lower limit on the baryon asymmetry
• f a low-scale leptogenesis model

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LNV at the LHC

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

not possible to generate large enough baryon asymmetry at all lower limit on CP-asymmetry

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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!