Asymmetric Dark Matter Revealing the history of the universe with - PowerPoint PPT Presentation

Asymmetric Dark Matter Revealing the history of the universe with underground particle and nuclear research 2019 (3/8/2019) Masahiro Ibe (ICRR)

Baryon-DM coincidence Problem DM and Baryon make up 27% and 4% of total energy density of the Universe. Ω DM h 2 ~ 0.14 Ω B h 2 ~ 0.022 ( Planck 2018 : Ω X = ρ X / 3 M PL2 H 02 , H 0 = 100h km/s/Mpc, h ~ 0.7 ) Baryon-DM coincidence ? Ω DM : Ω b ~ 5 : 1 close with each other… ex) neutrino-DM : Ω DM : Ω ν ( Σ m ν =0.06eV ) = 200 : 1 Is this a serious problem ?

<latexit sha1_base64="(nul)">(nul)</latexit> <latexit sha1_base64="(nul)">(nul)</latexit> <latexit sha1_base64="(nul)">(nul)</latexit> <latexit sha1_base64="(nul)">(nul)</latexit> Baryon-DM coincidence Problem If it were not for Baryogenesis… DM mass density can be explained by the WIMP mechanism : Ω DM ∝ m DM n DM � 10 − 9 GeV − 2 � 2 ≃ 0 . 1 × ⟨ σ v ⟩ → the observed density is explained by choosing appropriate mass & couplings The baryon density is too low due to its large annihilation cross section : x σ v y „ 4 π „ 10 GeV ´ 2 m 2 n → Ω DM : Ω b ( no-asymmetry ) = 1 : 10 -10 The observed baryon density is provided by the baryon asymmetry. Ω b ( with asymmetry ) = 0.02 ( η B / 10 -9 ) η B = ( n B - n B ̅ ) / n γ Baryon-DM coincidence = conspiracy between n DM and Baryogenesis ?

Baryon-DM coincidence Problem Answers ? Just a coincidence , Ω DM / Ω B ~ 5 is not a big deal. → Keep looking for conventional WIMPs ! Anthropic requirement ? For Ω B / Ω DM < 10 -(2-4) , no disk fragmentation in the galaxies, which makes the star formation rate very low… [’06 Tegmark, Aguirre, Rees, Wilczek] ( These arguments depend on which parameters we fj x. ) Some mechanism behind the coincidence ? → The asymmetric dark matter ( ADM ) provides an interesting insight !

Asymmetric Dark Matter (ADM) [1990 Barr Chivukula, Farhi , 1992 D. B. Kaplan, 2009 D. E. Kaplan, Luty and Zurek] Basic Idea Matter-anti-matter asymmetries in the SM/DM sectors η DM = ( n DM - n DM ) / n γ η B = ( n B - n B ̅ ) / n γ are generated from the common origin so that η DM / η B = O(1) . The mass densities of the baryon and dark matter are proportional to the asymmetries Ω b ( with asymmetry ) m N η B ∝ Ω DM ( with asymmetry ) m DM η DM ∝ → Ω DM / Ω B = ( m DM / m B ) ( η DM / η B ) The baryon-DM ratio Ω DM / Ω B ~ 5 can be achieved for m DM ~ 5 m B x ( η B / η DM ) ~ O(1) GeV

Asymmetric Dark Matter (ADM) Two main mechanisms Sharing mechanism SM and DM sectors share a primordial asymmetry produced in an arbitrary sector. Asymmetry is thermally distributed in the two sectors dark matter SM η DM / η B is related to the degrees of the freedom in two sectors Cogenesis The asymmetries in the two sectors are produced by the same process. Asymmetry Genesis dark matter SM η DM / η B depends on the branching ratio of the asymmetry [ Petraki & Volkas 1305.4939 Zurek 1308.0338 for review]

Asymmetric Dark Matter (ADM) Two main mechanisms Sharing mechanism SM and DM sectors share a primordial asymmetry produced in an arbitrary sector. Asymmetry is thermally distributed in the two sectors dark matter SM η DM / η B is related to the degrees of the freedom in two sectors In the following, we consider the sharing mechanism. In the sharing mechanism : What is the origin of the asymmetry ? How the asymmetries are shared ? → there are lots of possibilities…

Asymmetric Dark Matter via Leptogenesis Thermal Leptogenesis (at the decay of the right-handed neutrino N R ) L N - SM = 1 2 M R ¯ N R ¯ N R + y N HL ¯ N R + h . c . , ( N R : right-handed neutrino, M R > 10 10 GeV ) Asymmetry in the SM sector = the asymmetry of the B-L symmetry ( if it is generated T > O ( 100 ) GeV ) Dark Sector shares the B-L symmetry with the SM through 1 L B � L portal = O D O SM + h . c . , M n ⇤ O SM : Neutral ( other than B-L ) consisting of SM fj elds. O DM : Neutral ( other than B-L ) consisting of DM fj elds. The SM and the DM sectors are thermally connected at the high temperature T > T D ~ M * ( M * /M PL ) 1/(2n-1) ADM scenario is achieved by Thermal Leptogenesis for M R > T D .

Asymmetric Dark Matter via Leptogenesis Leptogenesis T ~ M R B-L asymmetry in SM + Dark sector η DM = A DM η B-L ( A SM + A DM = 1 ) η SM = A SM η B-L T D ~ M * ( M * /M PL ) 1/ ( 2n-1 ) η DM = A DM η B-L η SM = A SM η B-L T EW ~100GeV η B = A B η B-L η L = A L η B-L η DM = A DM η B-L ( A B / A SM = 30/97 ) n B = η B n γ → n DM = ( A DM / A B ) n B = ( A DM /A SM ) ( A SM /A B ) n B Ω DM = ( m DM /m p ) (A DM /A SM ) ( A SM /A B ) Ω B m DM = 5 m p (30/97 ) (A SM /A DM ) x ( Ω DM /5 Ω B ) determined by the degrees of freedom

Model Building of Asymmetric Dark Matter ADM models require a large annihilation cross section n DM /s n DM /s Large Annihilation Cross Section Small Annihilation Cross Section Thermal equilibrium Thermal equilibrium Symmetric Component Asymmetric Component Asymmetric Component Symmetric Component m DM /T m DM /T Annihilation of the symmetric component of DM should be very e ffi cient ! σ v >> 10 -9 GeV -2 Lots of possibilities… SM fj nal state via heavy mediators ( → similarity with the WIMP models ) fj nal states in the dark sector ( → the entropy in the dark sector should be transferred to the SM sector.)

Model Building of Asymmetric Dark Matter We prefer ADM models in which m DM = O ( 1 ) GeV is achieved without fj ne-tuning. The ADM scenario does not solve the coincidence problem but provides a new interpretation in terms of the mass ratio m DM /m N = O ( 1 ) . The ultimate solution to the problem is obtained when the mass ratio m DM /m N = O ( 1 ) is explained, which requires higher-energy theory. At least, m DM = O ( 1 ) GeV should not be achieved by fj ne-tuning to avoid that Ω DM / Ω B ~ 5 is realized by fj ne-tuning.

Model Building of Asymmetric Dark Matter Composite ADM models are highly motivated ! DM annihilation cross section is large ! DM DM σ v ~ 4 π / m DM 2 DM DM DM Symmetric components annihilates very e ffi ciently ! DM mass can be explained by dynamical transmutation. g The mass scale ~ dynamical scale is determined by the gauge coupling constant at the UV scale. m DM ~ Λ dyn ~ M UV Exp[ - 8 π 2 /b g ( M UV ) 2 ] ln μ [ b = 11/3 Nc - 2/3 N F for SU ( Nc ) N F - fm avor ] Λ dyn M UV

Model Building of Asymmetric Dark Matter Annihilation into SM sector … Elementary Annihilation ADM … into DM sector Thermal Leptogenesis B-L Composite Annihilation … ADM into DM sector Sharing … ADM Cogenesis … Among various possibilities, ADM with the sharing mechanism through B-L connecting operators with thermal Leptogenesis is very well motivated ! B-L symmetry is well-motivated in the SM ( can be gauged, SO ( 10 ) GUT ) Thermal Leptogenesis is very successful for the baryogenesis.

Model Building of Asymmetric Dark Matter Annihilation into SM sector … Elementary Annihilation ADM … into DM sector Thermal Leptogenesis B-L Composite Annihilation … ADM into DM sector Sharing … portals to ADM the SM sector Cogenesis … Compositeness is an interesting addition. large annihilation cross section m DM =O ( 1 ) GeV without fj ne-tuning Models are rather complicated The entropy in the dark sector should be transferred to the SM

<latexit sha1_base64="(nul)">(nul)</latexit> <latexit sha1_base64="(nul)">(nul)</latexit> <latexit sha1_base64="(nul)">(nul)</latexit> <latexit sha1_base64="(nul)">(nul)</latexit> Asymmetric Dark Matter and Dark Radiation What if the fj nal state particle in the dark sector are massless ? At T > T D , the SM and the DM sectors are in the thermal equilibrium ρ R “ π 2 30 p g SM p T q ` g DM p T qq T 4 ( g : the number of the e ff ectively massless degree of freedom g SM ( T ) = 106.75 ) Below T > T D , the thermal baths of the SM and the DM sectors evolve independently. T common temperature T D ~ M * (M * /M PL ) 1/(2n-1) SM DM T EW ~100GeV T dark QCD ~3GeV T QCD ~300MeV The temperatures of the two sectors are di ff erent at a later time.