The MSM Neutrino masses, Dark Matter, and Baryon Asymmetry Takehiko Asaka (Niigata Univ.) @Toyama Univ. (2014/01/12)
Introduction 2 Higgs had been discovered !! 2012/07/04 All elementary particles in the Standard Model had been confirmed by experiments !! Takehiko Asaka (Niigata Univ.) 12/01/2014
3 Whatʼs next after Higgs discovery? Takehiko Asaka (Niigata Univ.) 12/01/2014
Prologue: Physics beyond the SM 4 About 20 years ago …, There was no “convincing” evidence for physics beyond the minimal standard model (SM) People looked for physics beyond the SM “mainly” based on theoretical arguments and curiosities: Hierarchy problem Gravity, String, … Strong CP problem Why 3 generations? Why anomalies cancel? … Takehiko Asaka (Niigata Univ.) 12/01/2014
News from the sky 5 Neutrino Oscillations Cosmic Microwave Background (CMB [SuperK] [WMAP] Takehiko Asaka (Niigata Univ.) 12/01/2014
Physics beyond the MSM 6 In the last decade(s), we have collected quite “convincing” evidences for physics beyond the MSM Neutrino oscillations Baryon asymmetry Dark matter Dark energy Primordial density perturbations Takehiko Asaka (Niigata Univ.) 12/01/2014
Physics beyond the MSM 7 In the last decade(s), we have collected quite “convincing” evidences for physics beyond the MSM Neutrino oscillations Baryon asymmetry Dark matter Dark energy ?? ?? Primordial density perturbations Today, I would like to explain the MSM, which can solve first three problems! Takehiko Asaka (Niigata Univ.) 12/01/2014
Origin of neutrino masses 8 Neutrino mass scales � Atmospheric: �� ��� ≃ 2.4 � 10 �� eV � � Solar: �� ��� ≃ 7.5 � 10 �� eV � ⇒ Need for physics beyond the SM ! Important questions: “What is the origin of neutrino masses?” “How do we test it experimentally?” Takehiko Asaka (Niigata Univ.) 12/01/2014
Standard Model 9 Higgs Quarks and Leptons Gauge Bosons Bosons (left-handed) (right-handed) u c t u c t R R R � d s b d s b R R R L L L � e e R R R e L L L Takehiko Asaka (Niigata Univ.) 12/01/2014
Standard Model 10 Higgs Quarks and Leptons Gauge Bosons Bosons (left-handed) (right-handed) u c t u c t R R R � d s b d s b R R R L L L � e e R R R e L L L Takehiko Asaka (Niigata Univ.) 12/01/2014
Neutrino Minimal SM ( MSM) 11 TA, Blanchet, Shappshnikov (ʻ05), TA, Shaposhnikov (ʻ05) Higgs Quarks and Leptons Gauge Bosons Bosons (left-handed) (right-handed) u c t u c t R R R � d s b d s b R R R L L L � e e R R R �� �� �� e L L L Takehiko Asaka (Niigata Univ.) 12/01/2014
Extension by RH neutrinos 12 Minkowski ʼ77 M c M L i F L + h.c. Yanagida ʼ79 R R R R R 2 Gell-Mann, Ramond, Slansky ʻ79 Glashow ʻ79 Seesaw mechanism ( � � � � Φ ≪ � � ) c c 0 M M 0 1 1 D c L c L ( , ) h c . ( , N ) h c . . 1 L R T M M 0 M T 2 2 N M M M D M M R D D M M T U M U diag m m m ( , , ) 1 2 3 Light, active neutrinos → explain neutrino oscillations Where is Heavy, neutral leptons �� ≃ � � � the scale Mass � � of mass? Mixing Θ � � � /� � mixing in CC current � Takehiko Asaka (Niigata Univ.) 12/01/2014
Scale of Majorana mass 13 The simplest case: one pair of � � and � � 1 2 T 2 M M M F M M / D D M M M 2 F F Neutrino Yukawa Coupling t 0 2 -2 M m atm -4 log 10 (F) F F e -6 -8 -10 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 log 10 (M M /GeV) Majorana Mass Takehiko Asaka (Niigata Univ.) 12/01/2014
Convenstional seesaw scenario: 14 Neutrino Yukawa couplings are comparable to those of quarks and charged leptons M R >> 100GeV Explain smallness of neutrino masses via seesaw [Yanagida; Gell-Mann, Ramond, Slansky] Decays of RH neutrino(s) can account for baryon asymmetry through leptogenesis [Fukugita, Yanagida] Physics of RH neutrino cannot be tested directly by experiments Takehiko Asaka (Niigata Univ.) 12/01/2014
Scale of Majorana mass 15 The simplest case: one pair of � � and � � 1 2 T 2 M M M F M M / D D M M Baryogenesis M 2 via leptogenesis F F Neutrino Yukawa Coupling t Fukugita, Yanagida ʻ86 0 -2 -4 log 10 (F) F F e -6 -8 -10 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 log 10 (M M /GeV) Majorana Mass Takehiko Asaka (Niigata Univ.) 12/01/2014
The MSM: [TA, Blanchet, Shaposhnikov; 16 TA, Shposhnikov] No new mass scale is introduced M R ~<100GeV Lightest RH neutrino (~keV) can be DM (?) [Dodelson, Widrow,…] Oscillation of RH neutrinos can account for baryon asymmetry of the universe [Akhmedov, Rubakov, Smirnov/ TA, Shaposhnikov] Physics of RH neutrinos can potentially tested by experiments Takehiko Asaka (Niigata Univ.) 12/01/2014
Scale of Majorana mass 17 The simplest case: one pair of � � and � � 1 2 T 2 M M M F M M / D D M M Baryogenesis M 2 via leptogenesis F F Neutrino Yukawa Coupling t Fukugita, Yanagida ʻ86 0 -2 -4 log 10 (F) F F e -6 Baryogenesis -8 via neutrino osc. -10 Akhmedov, Rubakov, Smirnov ʻ98 -12 TA, Shaposhnikov ʻ05 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 log 10 (M M /GeV) Majorana Mass Takehiko Asaka (Niigata Univ.) 12/01/2014
Roles of three HNL 18 (“Dark” sterile neutrino) N 1 Dark Matter Candidate (Here, we do not specify its detail.) To avoid constraints, Yukawaʼs should be suppressed essentially, F 0 1 N and N (“Bright” and “Clear” sterile neutrinos) 2 3 Neutrino Oscillation data LINK Masses and mixings Baryon Asymmetry of the Universe (BAU) Mechanism via sterile neutrino oscillation Takehiko Asaka (Niigata Univ.) 12/01/2014
19 §2 Dark matter in the MSM Dark Matter Candidate: lightest heavy neutral lepton N1 with ~keV mass Dodelson, Widrow / Shi, Fuller / Dolgov, Hansen / Abazajian, Fuller, Patel /… (Incomplete list) Takehiko Asaka (Niigata Univ.) 12/01/2014
Decays of DM 20 N1 is not completely stable particle ! Dominant decay: for � � ~ keV � Lifetime can be very long � 10 �� � � � � 5 � 10 �� sec keV + … Θ � � � N1 is not completely dark ! Subdominant decay: � + … Branching ratio is small �� � 27� �� /8� But, severely restricted from X-ray observations Takehiko Asaka (Niigata Univ.) 12/01/2014
Production of DM 21 Due to smallness of Yukawa couplings, N1 is not thermalized in the early universe Production scenarios: Dodelson-Widrow scenario Production via active-sterile neutrino mixing W,Z N1 �/� � � Dominant production at � � 100MeV ��� Shi-Fuller scenario Production is boosted in the presence of lepton asymmetry due to the MSW effect Takehiko Asaka (Niigata Univ.) 12/01/2014
Cosmological Constraints 22 Radiative decays of DM No signal Upper bound on mixing angle ! Light heavy neutral lepton = WDM � �� ~Mpc keV � � Erase structures on smaller scales! � � � � Lower bound on mass (Ly- forest observations) � � ≳ 8 keV (DW scenario) Boyarsky, Lesgourgues, Ruchayskiy, Viel ʼ09,ʼ09 Phase-space analysis (Tremaine-Gunn bound) � � ≳ 1 � 2 keV Tremaine, Gunn ʻ79 Boyarsky, Ruchayskiy, Iakubovskyi ʻ08 Gorbunov, Khmelnitsky, Ruvakov ʻ08 Takehiko Asaka (Niigata Univ.) 12/01/2014
Dark Matter 23 Laine, Shaposhnikov ʻ08 Takehiko Asaka (Niigata Univ.) 12/01/2014
Dark Matter 24 Dodelson-Widrow mechanism does not work by Ly- constraint Shi-Fuller mechanism ?? Entropy production?? Yukawa couplings of N1 are very suppressed N1 decouples from the seesaw mechanism -> Lightest active neutrino � � � � 10 �� eV N1 contribution is negligible for baryogenesis N2 and N3 are responsible for Seesaw mass matrix for neutrino masses Baryon asymmetry of the universe Takehiko Asaka (Niigata Univ.) 12/01/2014
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