On neutrinoless double beta decay in the nMSM Hiroyuki Ishida (NCTS) @Nufact2016, Quy Nhon, Vietnam 2016/08/25 Collaborators : T. Asaka (Niigata), S. Eijima (EPFL) Ref : arXiv:1606.06686

The standard model is excellent! Introduction ・Conclusion of recent ICHEP conference is… The standard model is excellent! in spite of Almost of all suspicious excesses have gone There is no new significant signal for new physics so far

Introduction ・Unsatisfactory points in the SM of particle physics Neutrino masses Experimentally confirmed Baryon asymmetry of the universe Dark matter candidate want to explain these phenomena at the same time! The nMSM

The nMSM ・The most economical extension of the SM : SM + 3RHns [Asaka, Blanchet, and Shaposhnikov (2005)] ・The most economical extension of the SM : SM + 3RHns Key assumption Dirac masses ; Majorana masses ; *Neutrino mass matrix *Seesaw mechanism Tiny neutrino masses can explain by the seesaw mechanism

The nMSM ・Generic form of Yukawa coupling [Asaka, Blanchet, and Shaposhnikov (2005)] ・Generic form of Yukawa coupling [Casas, Ibarra(2001)] When 2RHn explain the tiny n masses by seesaw mechanism * * * * for N.H. for I.H. is arbitrary complex, Hereafter,

The nMSM Dark matter in the nMSM [Asaka, Blanchet, and Shaposhnikov (2005)] Dark matter in the nMSM The lightest right-handed neutrino in keV scale Highly constrained from X-ray observations and structure formation [Laine and Shaposhnikov (2008)] Phase space density X-ray observations Upper bounds on mixing angle between ordinary neutrinos DM production [Dodelson and Widrow (1993)] To avoid over abundant DM by DW mechanism

The nMSM Baryogenesis in the nMSM [Asaka, Blanchet, and Shaposhnikov (2005)] Baryogenesis in the nMSM Baryogenesis via neutrino oscillation [Akhemedov, Rubakov, and Smirnov (‘98)] [Asaka and Shaposhnikov (2005)] Initial condition : No RHn Produced by scattering processes Depart from thermal equilibrium RHns start to oscillate at TL Typical temperature to oscillate

The nMSM Baryogenesis in the nMSM [Asaka, Blanchet, and Shaposhnikov (2005)] Baryogenesis in the nMSM Baryogenesis via neutrino oscillation [Akhemedov, Rubakov, and Smirnov (‘98)] [Asaka and Shaposhnikov (2005)] Through RHns oscillation, CPV occurs via Yukawa couplings however, No asymmetry in the end @F4 order Asymmetry is produced @F6 order effects

The nMSM Baryogenesis in the nMSM [Asaka, Blanchet, and Shaposhnikov (2005)] Baryogenesis in the nMSM Baryogenesis via neutrino oscillation [Akhemedov, Rubakov, and Smirnov (‘98)] [Asaka and Shaposhnikov (2005)] Important thing : total lepton number is conserved Lepton number separation Baryon number is produced through sphaleron [Khlebnikov; Shaposhnikov(1988)] [Harvey; Turner(1990)]

The nMSM Baryogenesis in the nMSM [Asaka, Blanchet, and Shaposhnikov (2005)] Baryogenesis in the nMSM Baryogenesis via neutrino oscillation [Akhemedov, Rubakov, and Smirnov (‘98)] [Asaka and Shaposhnikov (2005)] Evolution of asymmetries(Total) Evolution of asymmetries(Each flavor)

The nMSM Baryogenesis in the nMSM [Asaka, Blanchet, and Shaposhnikov (2005)] Baryogenesis in the nMSM Baryogenesis via neutrino oscillation [Akhemedov, Rubakov, and Smirnov (‘98)] [Asaka and Shaposhnikov (2005)] Important parameters ・Mass degeneracy Asymmetry is enhanced because oscillation starts faster [Asaka, Eijima, and H.I in progress] ・Phase in the high sector Production of RHns is enhanced

Neutrinoless double beta decay Evidence of Majorana particles Diagram Maximal value of SM prediction (2 massive active neutrinos) : NH : IH

Neutrinoless double beta decay in the nMSM Diagram where <p2> : nucleon Fermi momentum in the nucleus [Faessler, Gonzalez, Kovalenko, and Simkovic (2014)] If all of Rhns are enough lighter than 　　　, However, such RHns cannot have enough short lifetime In this analysis, we consider

Neutrinoless double beta decay in the nMSM In the nMSM, only DM is enough light SM part DM contribution Heavy 2RHns contributions How large are the extra contributions in the whole parameter space? We take best fit values for neutrino oscillation parameters [Bergstoerm, Gonzalez-Garcia, Maltoni, and Shiwetz, (2015)] three phases d, h, and Rew are just free parameters

Neutrinoless double beta decay in the nMSM ・Contribution from DM Phase space density Contribution from DM is negligibly small [Asaka, Eijima, and H.I. JHEP 1104 (2011)] Two of 3RHns contribute to the effective mass of neutrinoless double beta decay in this model

Neutrinoless double beta decay in the nMSM ・Contribution from rest 2RHns In our previous result, [Asaka, Eijima, and H.I. (2011)] was negligibly small, since Only destructive contribution from RHns

Neutrinoless double beta decay in the nMSM ・Take a look term where, is expressed by active neutrino parameters : NH : IH ・If the combination can be much larger than 1 and This contribution can be significantly large!!

Neutrinoless double beta decay in the nMSM ・Recall the parameter space from BAU and can be large at the same time! Need to reevaluate the effective mass We will show the ratio

Neutrinoless double beta decay in the nMSM ・Results of NH IH BAU BAU In almost of all region, the effective mass is as large as the SM prediction at most

Neutrinoless double beta decay in the nMSM ・Results of NH IH BAU BAU In the IH case, the effective mass becomes close to be twice (Magenta) as much as the SM

Neutrinoless double beta decay in the nMSM ・Results of NH IH BAU BAU In the IH case, the effective mass becomes three times larger (Blue) as the SM prediction

Conclusions ・The nMSM The most economical extension of the SM n masses, BAU, and DM can be explained at the same time ・Neutrinoless double beta decay in the nMSM Mild mass degeneracy is available for BAU Analytical expression of the effective mass in the model There is no significant enhancement in the NH case However, Effective mass can be enhanced in the IH case! Predicted region in the IH case is going to be constrained!

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