BIG BANG NUCLEOSYNTHESIS OF NUCLEAR DM (AND OTHER NON-STANDARD DM) STEPHEN WEST U NIVERSITY O F B IRMINGHAM F EBRUARY 24 TH 2016
OUTLINE PARTIAL OVERVIEW OF NON-STANDARD DM FREEZE-OUT ASYMMETRIC FREEZE-OUT FREEZE-IN NUCLEAR DARK MATTER
STANDARD FREEZE-OUT STANDARD SCENARIO FOR WIMP DM… X SM σ A X SM SINGLE SPECIES OF DARK MATTER RADIATION DOMINATED UNIVERSE INITIALLY IN THERMAL EQUILIBRIUM T > m X AS THE TEMP DECREASES T < m X CREATION OF BECOMES X KOLB AND TURNER EXPONENTIALLY SUPPRESSED ANNIHILATION OF STILL PROCEEDS, NUMBER DENSITY OF GIVEN BY X X ◆ 3 / 2 ✓ m X T n X,eq → 0 e − m X /T N EQ ≈ g X 2 π as T → 0
STANDARD FREEZE-OUT DUE TO EXPANSION, DARK MATTER NUMBER DENSITY FREEZES-OUT WHEN: Γ = n X h σ A v i < H X SM σ A X SM KOLB AND TURNER YIELD SET AT FREEZE-OUT GIVES FINAL DARK MATTER ABUNDANCE. Ω h 2 ⇠ 0 . 13 ⇥ 10 − 26 cm 3 s − 1 h σ A v i
MODIFYING FREEZE-OUT - ASYMMETRIC DM ( COMPLEX SCALAR OR ONE VERY POPULAR OPTION - ASYMMETRIC DM χ D IRAC FERMION ) N USSINOV ’85; G ELMINI , H ALL , L IN ’87; B ARR ’91; VISIBLE SECTOR K APLAN ‘92;T HOMAS ’95; H OOPER , M ARCH -R USSELL , SW ’04; K ITANO AND L OW ‘04, K APLAN , L UTY Z UREK ’09 ; F OADI , F RANDSEN , S ANNINO ‘09+… q, e, W, Z, H, ˜ q, ... DYNAMICS GENERATE DARK MATTER χ , χ POSSESSING A MATTER - ANTIMATTER ASYMMETRY n χ � n χ 6 = 0 FOR SUFFICIENTLY LARGE DM ANNIHILATION - DM ABUNDANCE IS DETERMINE BY ASYMMETRY
ASYMMETRIC DM MOTIVATION Ω dm ∼ 5 Ω B STANDARD PICTURE: WIMP FREEZE - OUT - Γ ann < Ω dm ∼ H SET WHEN S ET BY CP- VIOLATING , BARYON NUMBER Ω B VIOLATING OUT OF EQUILIBRIUM PROCESSES GIVEN THE PHYSICS GENERATING EACH QUANTITY , RATIO IS A SURPRISE I F NOT A COINCIDENCE - NEED TO EXPLAIN THE CLOSENESS A SYMMETRIC D ARK S HARED DYNAMICS ⇒ ⇒ M ATTER
MODELS OF ADM η dm = n dm � n dm 6 = 0 η B = n B � n B 6 = 0 OR OR BOTH R ELATE THIS DM ASYMMETRY TO THE BARYON ASYMMETRY L EADING TO : η dm = C η B n dm − n dm ∝ n B − n B ⇒ n dm � n dm ∼ ( n dm − n dm ) m dm ∼ ( n dm + n dm ) m dm Ω dm ( n B − n B ) m B ( n B + n B ) m B Ω B
MODELS OF ADM η dm = n dm � n dm 6 = 0 η B = n B � n B 6 = 0 OR OR BOTH R ELATE THIS DM ASYMMETRY TO THE BARYON ASYMMETRY L EADING TO : η dm = C η B n dm − n dm ∝ n B − n B ⇒ ∼ ( n dm − n dm ) m dm Ω dm ∼ η dm m dm ( n B − n B ) m B Ω B η B m B
MODELS OF ADM η dm = n dm � n dm 6 = 0 η B = n B � n B 6 = 0 OR OR BOTH R ELATE THIS DM ASYMMETRY TO THE BARYON ASYMMETRY L EADING TO : η dm = C η B n dm − n dm ∝ n B − n B ⇒ ∼ C m dm Ω dm ∼ η dm m dm m B Ω B η B m B
MODELS OF ADM η dm = n dm � n dm 6 = 0 η B = n B � n B 6 = 0 OR OR BOTH R ELATE THIS DM ASYMMETRY TO THE BARYON ASYMMETRY L EADING TO : η dm = C η B n dm − n dm ∝ n B − n B ⇒ ∼ C m dm Ω dm ∼ η dm m dm m B Ω B η B m B V ALUE OF IS DETERMINED BY HOW THE ASYMMETRIES ARE SHARED C BETWEEN THE TWO SECTORS
ADM BASICS I F ASYMMETRY SHARING Ω dm ∼ η dm m dm PROCESS DROPS OUT OF η dm ∼ η B THERMAL EQUILIBRIUM WHEN Ω B η B m B DM IS STILL RELATIVISTIC T HEN WE GET A PREDICTION FOR THE MASS OF THE DARK MATTER m dm ∼ 5 m B ∼ 5 GeV T HIS IS THE “ NATURAL ” DARK MATTER MASS FOR ADM MODELS . N OT THE ONLY POSSIBLE MASS , MORE SOPHISTICATED MODELS CAN ALLOW FOR A LARGE RANGE OF ADM MASSES ⇒ D EPENDS ON THE WAY IN WHICH THE ASYMMETRY IS SHARED ( OR GENERATED )
HEAVY ADM SEE E.G. BARR 91, BUCKELY, RANDALL ‘11 C AN HAVE ADM WITH HEAVY MASSES X NUMBER VIOLATING PROCESSES ONLY DECOUPLE AFTER DM HAS BECOME NON - RELATIVISTIC D ARK MATTER ASYMMETRY GETS B OLTZMANN SUPPRESSED ⇒ Ω dm ≈ m dm x 3 / 2 e − x Ω B m B x = m dm WITH T d DECOUPLING TEMP OF X-NUMBER T d VIOLATING INTERACTIONS A CTUAL SUPPRESSION IS MORE COMPLICATED - SEE B ARR ‘91
HEAVY ADM B UCKLEY , R ANDALL ; (2010) L ARGE RANGE OF POSSIBLE MASSES
HIDDEN SECTOR DM VISIBLE SECTOR HIDDEN SECTOR PORTAL q, e, W, Z, H, ˜ q, ... φ i , χ i , X µ ... H IDDEN SECTOR STATES HAVE NO S M GAUGE INTERACTIONS HIDDEN SECTOR MAY BE LINKED , BEYOND GRAVITY , TO THE VISIBLE SECTOR | H | 2 | φ i | 2 P ORTALS : HIGGS - NEUTRINO - LH χ i U (1) 0 G AUGE BOSON ( ∂ µ X ν − ∂ ν X µ ) F µ ν KINETIC MIXING - IF IS A X ν Y 1 PLUS D>4 OPERATORS M n − 4 O sm O hs THE FORM OF THIS PORTAL CAN PLAY A MAJOR ROLE IN D M GENESIS
SINGLE SPECIES DM VISIBLE SECTOR HIDDEN SECTOR PORTAL q, e, W, Z, H, ˜ q, ... χ MUCH DEPENDS ON PORTAL - IF PORTAL INTERACTION IS STRONG ENOUGH FOR HIDDEN AND VISIBLE SECTORS TO BE IN THERMAL EQUILIBRIUM - USUAL FREEZE - OUT PICTURE I F PORTAL INTERACTION IS FEEBLE AND NOT IN THERMAL χ EQUILIBRIUM - CAN LOOK TO FREEZE - IN HALL , JEDAMZIK , MARCH - RUSSELL , SW ’09 SEE EARLIER IMPLEMENTATION : M CDONALD ’01, T. A SAKA , K. I SHIWATA , T. M OROI ’05, ‘06 FREEZE - IN - BATH PARTICLE SCATTERINGS OR DECAYS PRODUCE F IMPS THROUGH FEEBLE PORTAL INTERACTIONS
Freeze-in overview • Freeze-in is relevant for particles that are feebly coupled ! (Via renormalisable couplings) - ! λ Feebly Interacting Massive Particles (FIMPs) X λ X Thermal Bath ! Temp T > M X is thermally decoupled and we ! X assume initial abundance negligible • Although interactions are feeble they lead to some production X
Freeze-in overview • Freeze-in is relevant for particles that are feebly coupled ! (Via renormalisable couplings) - ! λ Feebly Interacting Massive Particles (FIMPs) X λ X Thermal Bath ! Temp T > M X is thermally decoupled and we ! X assume initial abundance negligible • Although interactions are feeble they lead to some production X
Freeze-in overview • Freeze-in is relevant for particles that are feebly coupled ! (Via renormalisable couplings) - ! λ Feebly Interacting Massive Particles (FIMPs) X λ X Thermal Bath ! Temp T > M X is thermally decoupled and we ! X assume initial abundance negligible • Although interactions are feeble they lead to some production X
Freeze-in overview • Freeze-in is relevant for particles that are feebly coupled ! (Via renormalisable couplings) - ! λ Feebly Interacting Massive Particles (FIMPs) X λ X Thermal Bath ! Temp T > M X is thermally decoupled and we ! X assume initial abundance negligible • Although interactions are feeble they lead to some production X • Dominant production of occurs at IR dominant T ∼ M X X • Increasing the interaction strength increases the yield opposite to Freeze-out...
Freeze-out vs Freeze-in 1 Freeze-in via, decays, inverse Y F O ⇠ decays or 2-2 scattering h σ v i M P l m 0 Coupling strength λ Using h σ v i ⇠ λ 0 2 /m 0 2 mass of heaviest particle in m interaction ✓ m 0 ◆ ✓ M P l ◆ Y F O ∼ 1 Y F I ∼ λ 2 λ 0 2 M P l m
Freeze-in vs Freeze-out • As drops below mass of relevant particle, DM abundance is T heading towards (freeze-in) or away from (freeze-out) thermal equilibrium Equilibrium yield Y Increasing ! λ Increasing ! λ for freeze-out for freeze-in 10 � 9 10 � 12 10 � 15 1 10 100 x = m/T
Freeze-in vs Freeze-out • For a TeV scale mass particle we have the following picture. Ω X h 2 ! x f freeze-in r freeze-out n e i e - z e e z - e o e u r 0.1 f t " !" " ’ 10 -12 λ , λ � 1
FIMP miracle vs WIMP miracle • WIMP miracle is that for m � ∼ v λ � ∼ 1 ✓ m 0 ◆ v Y F O ∼ 1 ∼ λ 0 2 M P l M P l • FIMP miracle is that for m ∼ v λ ∼ v/M P l ✓ M P l ◆ v Y F I ∼ λ 2 ∼ M P l m
Example Toy Model I • FIMPs can be DM or can lead to an abundance of the ! Lightest Ordinary Supersymmetric Particle (LOSP) • Consider FIMP coupled to two bath fermions and ψ 1 ψ 2 X • Let be the LOSP ψ 1 L Y = λ ψ 1 ψ 2 X • First case FIMP DM: m ψ 1 > m X + m ψ 2 ψ 2 Ω X h 2 ∼ 10 24 m X Γ ψ 1 ψ 1 λ m 2 ψ 1 X Ω X h 2 ∼ 10 23 λ 2 m X Γ ψ 1 ∼ λ 2 m ψ 1 Using ⇒ m ψ 1 8 π for correct DM abundance For need m X λ ∼ 10 − 12 ∼ 1 m ψ 1 • Lifetime of LOSP is long - signals at LHC, BBN...
Toy Model continued... • Second case LOSP (=LSP) DM: m X > m ψ 1 + m ψ 2 ψ 1 Ω X h 2 ∼ 10 24 Γ X ∼ 10 23 λ 2 X λ m X ψ 2 Γ X ∼ λ 2 m X Using 8 π • BUT is unstable... X ψ 1 Ω ψ 1 h 2 = m ψ 1 Ω X h 2 ∼ 10 23 λ 2 m ψ 1 giving λ X m X m X ψ 2 for correct DM abundance Again for need m X λ ∼ 10 − 12 ∼ 1 m ψ 1 • lifetime can be long - implications for BBN, indirect DM detection X Another source of boost factors
Example Model II • Many applications and variations of the Freeze-in mechanism • Assume FIMP is lightest particle carrying some stabilising symmetry - FIMP is the DM • Consider quartic coupling of FIMP with two bath scalars Assuming L Q = λ X 2 B 1 B 2 m X � m B 1 , m B 2 B 1 X Ω h 2 X ≈ 10 21 λ 2 λ B 3 For correct DM ! X ⇒ λ ∼ 10 − 11 abundance • NOTE: Abundance in this case is independent of the FIMP mass
Summary of Scenarios Long-lived LHC BBN m 1 Y Freeze-in LOSP LOSP of FIMP DM X X t BBN m 2 Y LOSP LOSP Freeze-out LOSP and decay to X FIMP DM X t Enhanced DM BBN m 3 Y FIMP Freeze-in X LOSP and decay to LOSP DM X LOSP t m BBN 4 Freeze-out Y X of LOSP LOSP DM X LOSP t
NUCLEAR DARK MATTER
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