BARYOGENESIS FROM WIMPS Y. Cui, L. Randall, and BS, arXiv:1112.2704 (JHEP) Y. Cui and BS, arXiv:1409.6729 (PRD) Brian Shuve SLAC Probing the Electroweak Phase Transition with a Next-Generation pp Collider 19 September 2015
Cosmology at the Weak Scale We have a new scale in particle physics Electroweak baryogenesis links the baryon asymmetry to this new scale (but need new dynamics!) 2
Cosmology at the Weak Scale Coincidentally, we also see this scale imprinted in cosmology DM SM ✓ α W ◆ 2 ✓ M DM ◆ 2 1 Ω DM ⇠ h σ v DM i ⇠ 0 . 27 TeV α DM perturbative unitarity: M DM . 100 TeV Griest, Kamionkowski 1990 DM SM What does this have to do with baryogenesis? Some hints.... 1) Comparable energy densities of baryons and DM Ω DM ≈ 5 Ω ∆ B see also Asymmetric Dark Matter models (recent renewal of interest: ex. Kaplan, Luty, Zurek 2009) 2) Common features in DM/baryogenesis dynamics • Out-of-equilibrium dynamics, CPV, self-conjugate particles 3
Baryogenesis-WIMP connections I will briefly review two possible WIMP baryogenesis mechanisms, focusing on connections between cosmology and weak-scale probes Baryogenesis from WIMP Annihilation (“WIMPy Baryogenesis”): DM SM B − L > 0 Typically predict new gauge-charged states 0 • = Collider and DM probes • L − B Cui, Randall, BS 2011 DM SM Baryogenesis from Meta-Stable WIMP Decay: u i χ • Colliders SM (long-lived decays) d j χ SM Cui, Sundrum 2012 χ Cui 2013 d k Cui, BS 2014 4
WIMPy Baryogenesis DM SM B − L > 0 0 = L − B DM SM 5
WIMPy Baryogenesis Sakharov conditions: 1. Violation of B-L X DM SM If DM is a colour singlet, no B-L violation allowed • B − L > 0 0 exotic = for pair of SM final states L − Need to couple to an exotic B/L charged state B • DM SM • Equal and opposite asymmetries in regular baryons & exotic baryons • Need asymmetries to be sequestered or for the exotic baryon to have additional couplings to quarks that change its effective baryon number sterile antibaryons B B exotic violating conserving DM antibaryon exotic decay decay DM antibaryon DM SM baryons DM SM baryons 6
WIMPy Baryogenesis 2. Violation of CP X DM SM • Generally have phases in new couplings B − L > 0 0 exotic = L • Might provide phenomenological handle! − B DM SM new CP phases • Physical CP violation comes from interference with on-shell states in loop: ψ X ψ X u ¯ λ ∗ 2 λ 2 λ ∗ 2 1 9 u ) − Γ ( X † X † → † ¯ u † ) 3 ✏ ≡ Γ ( XX → ¯ u ) + Γ ( X † X † → † ¯ Γ ( XX → ¯ u † ) ψ u ¯ X X u ¯ EFT diagrams from Bernal et al., 2012 7
WIMPy Baryogenesis 3. Departure from Thermal Equilibrium Opening the loop gives rise to washout processes • We want these to be inactive at some point during DM annihilation • ψ X X † X ψ † ψ λ 2 λ 2 λ 2 s 1 ,s 2 ,t s 1 ,s 2 ,t WO ψ † u X u u † ¯ ¯ u ¯ ¯ Γ DM ann . ⇠ h σ v XX → ψ ¯ u i Y X Γ washout ⇠ h σ v ψ ¯ u † i Y ψ Y u + . . . u → ψ † ¯ Annihilation, asymmetry production and washout depend on same couplings • Generally, washout only freezes out before DM annihilation for • M X . M ψ . 2 M X and ѱ in equilbrium Can be somewhat relaxed in EFT (Bernal et al., 2012) 8
WIMPy Baryogenesis: Asymmetry Example simplified model: u + 1 L ⊃ λ i S i X 2 + y i S i ψ ¯ u † ¯ d † ) + h . c . Λ 2 ( ψ n )(¯ • S is real scalar mediator n is a Majorana singlet (can be dark radiation), keeps ѱ in equilibrium • Avoid ѱ - quark mixing due to some discrete (or global) symmetry • Can have leptogenesis if ѱ instead couples to leptons • M S = 5 TeV , M X = 3 TeV m S � 1.5 TeV 1.5 ( M ψ = 4 TeV) 2 m X � m Ψ Viable parameters ! "# $%&'()$&(*+,-./ 1.0 m Ψ � m S Washout $$! 2 too strong ! "# $%*.3,45$&(*+,-./$ 0.5 ( M ψ = 2 TeV) LHC EXCLUDED '6 ! 2 LHC gluino constraint 01 0.0 0.0 0.2 0.4 0.6 0.8 1.0 m X � m S 9
WIMPy Baryogenesis: Pheno Colliders are the best way of probing WIMPy baryogenesis! Direct Baryogenesis Leptogenesis ( XX → ¯ u ψ ) ( XX → L ψ ) ∆ L = 1 u † ¯ d † ) Λ 2 ( ψ n )(¯ ∆ L = LH ∗ n n wino-like ¯ d ψ ¯ u ψ ± W ± gluino-like ψ 0 n † ψ † d † ¯ u † M ψ bound M ψ bound ¯ 8 TeV, 20/fb: 8 TeV, 20/fb: 1.35 TeV 720 GeV 14 TeV, 3/ab: 14 TeV, 3/ab: 1 TeV 2.5 TeV 11.5 TeV 100 TeV, 3/ab: 100 TeV, 3/ab: 3.3 TeV 10 Recast from Cohen et al. , 2013 (Snowmass) Gori, Jung, Wang, Wells 2014
WIMPy Baryogenesis: Pheno M S = 5 TeV , M X = 4 TeV , M ψ = 7 TeV • Perturbative direct baryogenesis parameter space 10.0 largely covered @ 100 TeV, 3/ab 7.0 5.0 • Leptogenesis more challenging near perturbativity Λ B � Λ X Y ∆ B = 2 Y obs 3.0 ∆ B limit 2 Y 2 Y X 2 Y x � 3 x 10 � 13 X � 9.5 x 10 � 3 x 2.0 1 0 � 14 � 1 4 • In extended models, other signatures are possible 1.5 � observed � 1.0 (ex: RPV-like decays of charged states) 1 2 3 4 5 Y ∆ B = Y obs Y ∆ B = 0 . 5 Y obs Λ X ∆ B ∆ B Other possible constraints: 1. EDMs Naïve two-loop result cancels, giving suppressed EDMs in minimal model (may be • larger in extended models) 2. Direct detection • Naïve one-loop result cancels, giving velocity-suppressed spin-independent rates 3. Indirect detection Subdominant to collider constraints (but more model-independent) • 11
Baryogenesis from WIMP Decay u i χ SM d j χ SM χ d k 12
Baryogenesis from WIMP Decay • In WIMPy baryogenesis, baryogenesis comes from WIMP dynamics but the asymmetry is not directly related to the WIMP abundance Alternatively, if DM is produced through the decay of a meta-stable WIMP, • the asymmetry is automatically proportional to a DM-like abundance ✏ = Γ ( � → B ) − Γ ( � → ¯ Ω ∆ B ≈ ✏ M nucleon B ) Ω τ χ →∞ Γ ( � → B ) + Γ ( � → ¯ χ B ) M χ Cui, Sundrum 2012 WIMP dynamics can give an overabundance of χ , compensating for the • suppression factors To inherit the freeze-out abundance, • Γ χ . H ( T f . o . ) • Earlier decay can generate some asymmetry, but it is diluted due to rapid χ scattering 13
Baryogenesis from WIMP Decay • How big was the universe around the weak scale? H (100 GeV) ∼ 10 − 14 GeV ∼ (1 . 3 cm) − 1 10 GeV → (1 . 3 m) − 1 1 TeV → (0 . 13 mm) − 1 Recall z f.o. ~ 20 • For WIMP masses ~100 GeV-TeV, the particle is long-lived if we can make it at • a collider! Heavier particles are closer to B lifetime, but mass discrimination is better • 14 see also Barry, Graham, Rajendran 2013
Baryogenesis from WIMP Decay • The method of collider production is similar to DM: cross the diagram j/ ` / MET MET χ χ BG DM vs . p p p p ISR χ BG ( c τ χ & 1 mm) χ DM MET j/ ` / MET Large production + late decay consistent with approximate stability symmetry • Direct link between cosmological condition and collider signature • Look at representative models to see possible production modes, and then • use simplified models approach for collider study 15
SUSY Model • An RPV-SUSY model illustrates the possible long-lived particles Many CP phases (ex. gaugino masses) • B-L violation can come from udd, QdL, LLE-type superpotential terms or RPV terms • in Kähler potential Mini-split spectrum alleviates EDM constraints, makes LSP long-lived • Cui 2013 Bino typically gives overabundance, so it is a natural candidate for χ • Asymmetry is largest when there is some other on-shell Majorana state that can run • " in loop Interference loop: Tree-level RPV decay: Thermal annihilation: Tree-level Decay Loop-level Decay Freeze-out d i ˜ d i B ˜ H B ˜ d ˜ B g ˜ d j ˜ d ∗ d j ˜ H ¯ d ˜ B H ∗ ˜ d ∗ u k u k -split spectrum: Can also have light gauge-charged states with same parametric lifetime • 16
WIMP decay baryogenesis: Pheno Cui, BS 2014 Similar to EWBG, factorize CPV from equilibrium criterion • By analogy with DM, classify pair production modes, such as... • SM gauge interactions: Higgs portal: Majorana = gaugino-like (wino) singlet-like χ χ g/W/Z h S λ S χχ sin α χ χ fix χ mass @ 150 GeV, study coupling reach coupling fixed, can study mass reach HL - LHC ILC - 1 ILC - 3 TLEP LHC 250 Model-independent constraints on • 200 Higgs mixing relatively weak m 2 H GeV L 150 100 Profumo, Ramsey-Musolf, Wainwright, Winslow 2014 0.85 0.90 0.95 1.00 17 cos q
WIMP decay baryogenesis: Pheno Unlike DM, we also have to specify decay modes (also two examples): • Lepton number violating: Baryon number violating: χ → L i Q j ¯ k ) † d k χ → Q i Q j ( d c χ → u i d j d k displaced jets (all-hadronic) displaced muon + hadrons CMS, arXiv:1411.6530 ATLAS-CONF-2013-092 We specifically looked at inner-detector decays (consistent with saturating • cosmological criteria), but decays in other components important too Very low SM backgrounds give good sensitivity even for small cross • sections Later comprehensive analyses in RPV SUSY: Liu, Tweedie 2015; Csaki et al. , 2015; Zwane 2015 In context of naturalness: Craig et al. , 2015; Csaki et al., 2015; 18
Recommend
More recommend
