Axino Phenomenology in the Kim-Nilles mechanism

Transcription

1 CP3, SDU, Odense, 11 Aug Axino Phenomenology in the Kim-Nilles mechanism Eung Jin Chun

2 Outline Introduction to strong CP problem & axion. KSVZ & DFSZ axion models. Supersymmetric axion models and axino cosmology. Natural SUSY ala Kim-Nilles: CDM mixed Higgsino & axion. LHC phenomenology of the axino LSP. Conclusion. EJC, Bae, EJC, Im, Bae, Baer, EJC, ; Barenboim, EJC, Jung, Park,

3 U(1) A Problem of QCD In the limit of m f 0 (f=u,d), U(2) V x U(2) A symmetry: U(2) V = SU(2) V x U(1) B : S(2) A = SU(2) A x U(1) A broken by QCD condensate Goldstone bosons : 3

4 Chiral Anomaly & QCD Vacuum U(1) A is not a symmetry: ABJ anomaly Under U(1) A rotation: µ vacuum: 4

5 Strong CP problem Gauge-invariance allows QCD µ term: It is a CP-odd E B term inducing nucleon EDM. Why is µ so small? (cf. weak CP ~1.) Hierarchies of fundamental parametrs in SM: y t ~ 1 ; y e ~ 10-6 ; y D º ~10-12 ; µ ~

6 Axion A (pseudo) Goldstone boson of a spontaneously borken QCD-anomalous global U(1) (Peccei-Quinn) symmetry. 6

7 Axion models Kim-Shifman-Vainshtein-Zakharov: Dine-Fischler-Srednicki-Zhitinitski: After the PQ symmetry breaking: 7

8 Dynamical relaxation of µ Rotting away a from PQ-charged quark mass terms; QCD phase transition generates axion potential: Axion is super-light: 8

9 Constraints on F a Lower bound from star cooling: low F a efficient axion emission fast star cooling. Upper bound from axion dark matter density: axion potential after QCD drives a coherent axion oscillation Ω a ~ F a 7/6. 9

10 Domain Wall problem If A 3 =N DW >1, there exits N DW -1 distinguishable vacua and thus domain walls connecting them can be formed to overclose the universe. Note: N DW =1 (6) for KSVZ (DFSZ). If the PQ symmetry is broken during inflation, this problem can be evaded as domain walls are washed away by inflation. If the PQ symmetry is broken after inflation, N DW =1 is required. 10

11 Axion Cold Dark Matter Axion relic abundance: Includes axions produced from the axionic string and domain walls. Quantum fluctuation of the initial mis-alignment during inflation. PQ symmetry breaking during inflation: PQ symmetry breaking after inflation: 11

12 Supersymmetric axion models Two ways to realize PQ symmetry (QCD-anomaly). KSVZ introduce extra heavy vector-like quarks: DFSZ extend the Higgs bilinear term: Simultaneous resolution of the strong CP and ¹ problems Kim-Nilles, 84 12

13 Supersymmetric axion multiplet Axion accompanied by its superpartners -- saxion & axino: Effective theory below F a : A+MSSM. Saxion & axino play important roles in cosmology including dark matter physics. Characteristically different saxion/axino couplings: 13

14 Axino/saxion mass SUSY breaking induces axino/saxion mass. Model-dependent SUSY and PQ symmetry breaking: EJC, Kim, Nilles, 92 EJC, Lukas, 95 Axino mass is typically at TeV but can be much lighter. Saxion mass is around m 3/2. 14

15 Cosmic axino/saxion production Axino/saxion are too weakly interacting to be in thermal equilibrium. Still, copious axino/saxion are generated by their couplings to gluon(ino)s, (s)quarks and Higgs(ino)s in thermal equilibrium. 15

16 KSVZ axino abundance For T R <Fa=M Q : Covi, Kim, Kim, Roszkovski, Brandenburg, Steffen, Strumia, if stable 16

17 DFSZ axino abundance For T R > m H, stop : EJC, Bae, KChoi, Im, Bae, EJC, Im, if stable For T R < m H, stop : Boltzmann suppressed larger mass allowed. 17

18 DFSZ axino abundance Decay/inverse-decay & scattering: Resonant scattering 18

19 Cosmic saxion production Production from thermal scattering: same as for the axino. Coherent oscillation with initial amplitude s 0 = F a : 19

20 Saxion/axino decays Saxion has generically order-one couplings to axions/axinos: EJC, Lukas, 95 Saxion to Higgs/Higgsinos: Axino to Higgs and Higgsino: 20

21 Implication of saxion/axino decays Late decay of overabundant axino/saxion may (over)produce neutralino (dark matter), axion (dark radiation), entropy (SM particles): Decay temperature: 21

22 Impact on neutralino relic density Decay of abundant heavy saxion/axino will overproduce the neutralinos (Y WIMP ~ ): T D > T f : standard freeze-out relic density. T D < T f : strong annihilation can deplete the over-produced DM abundance Reannhilation of neutralino LSP Higgsino/wino DM. KYChoi, Kim, Lee, Seto, Baer, et.al.,

23 EWSB and Higgs mass in SUSY Higgs potential in SUSY: Minimization conditions: Higgs mass at 1-loop: =

24 Natural SUSY? LHC pushes up gluino/squark masses above 1000 GeV. 125 GeV Higgs requires stop mass above ~ 1000 GeV. Hall, et.al., 2012 Still EWSB can be made natural with both radiatively driven m Hu and tree ¹ at around 100 GeV. 24 Baer, et.al., 2012

25 Benchmark for radiative natural SUSY Higgsino LSP underabundant 25

26 DM candidates Higgsino standard under-abundant, strong direct detection constraint. *Re-annihilation due to saxion/axino decay may enhance the abundance. Axion CDM from standard coherent oscillation with initial misalignment µ 1 : Axino if very light (<MeV). 26

27 Saxion decays 27

28 Axino decays 28

29 Dark Matter composition axino saxion 29

30 Dark radiation from s aa (entropy dumping) 30

31 Characteristics depending on F a Low F a region: GeV. Saxion/axino decay before neutralino freeze-out Standard neutralino density (10%)+axion density (90%) Intermediate F a region: GeV. Saxion/axino decay after neutralino freeze-out Augmented neutralino (10-100%) + axion (90-0%) High F a region: GeV. Overclosing neutralinos even after re-annihilation Saxion oscillation produces sizable dark radiation (axion) 31

32 Neutralino detection 32

33 Axion detection CAPP in Korea 33

34 Barenboim, EJC, Jung, Park, LHC signatures of the axino LSP Natural SUSY light Higgsino LSP (¹ < ~200 GeV): hard to probe. Higgsino NLSP - Bino LSP: 34

35 Higgsino NLSP-Axino LSP Higgsino decays to h/z+axino leave displaced vertices. The current & future (dijet) DV searches probe ¹ & F a. 35

36 Current limits from the prompt/displaced 36

37 LHC14 projection Assuming ² DV = 0.1: 37

38 Conclusion Resolution of the mu, strong CP and the Higgs fine-tuning problems leads to Natural SUSY+DFSZ axion. Long-lived axinos/saxions can be produced copiously thru thermal generation/coherent oscillation Heavy unstable axino: late decays may produce significant amounts of neutralino, dark radiation, & entropy to change DM cosmology. Mixed neutralino/axion DM realized for F a = GeV Signals in LUX/Zenon+ADMX/CAPP? Axino LSP: Higgsino NLSP decay to h/z+axino leaves displaced vertices the current/future dijet DV searches probe F a up to 10 11/12 GeV. 38