Minimal Dark Matter and Direct Detection as a Probe of Reheating - PowerPoint PPT Presentation

Minimal Dark Matter and Direct Detection as a Probe of Reheating Masahiro Ibe [ ICRR & IPMU ] 2/14/2014 @ Toyama Mini-Workshop 2014 Based on arXiv:1310.7495 (B.Feldstein, MI, T.T.Yanagida) to appear in PRL

Introduction What do we learn from the discovery of the Higgs? 1. Higgsless models are almost excluded ! 2. Higgs is more like an elementary scalar ! In the simplest implementation... V V = - m higgs2 /2 h † h + λ /4 (h † h) 2 m higgs = λ 1/2 v [ v=174.1GeV] λ ~ 0.5 m higgs ~ 125GeV h m h2 The quartic coupling λ is small and this simple elementary scalar Higgs description works consistently ! The Minimal Standard Model works !

Introduction How about Naturalness ? The mass of the elementary Higgs boson is not protected by any symmetries... Why m higgs2 ≪ M GUT 2 , M PLANCK 2 ? It is quite reasonable to expect new physics behind the Standard Model at around O(100)GeV - O(1)TeV ! Supersymmetric Standard Models ? Extra Dimensional Models ? Composite Higgs Models ? These are very exciting possibilities to be tested at the 14TeV run of the LHC, at the ILC.

Introduction So far, we have no direct observational data which support these possibilities from collider experiments... cf.) No supersymmetric particles have been discovered at the LHC ; squark/gluino mass > 1.8 TeV gluino mass > 1.4 TeV for squark >> TeV Negative pressure on Supersymmetry as a solution to the Naturalness problem ... We have no imminent need to give up the Naturalness problem as a guiding strategy at all. However, we might need to start thinking di ff erently... The success of the simplest Higgs mechanism might suggest that Simplicity is a more important guiding strategy in constructing models of new physics... What can we think of if we impose Simplicity on dark matter ?

Putting Simplicity on Dark Matter How to impose Simplicity on the dark matter sector ? No unique de fi nition of simplicity... There are tons of ways..., Let us explore the extreme cases : The dark sector consists of just a single massive particle with the charges under the Standard Model gauge groups and introduce no new interactions. [cf. neutral single dark matter with new higgs interactions (’04 Davoudiasl, Kitano, Li, Murayama )] (Integer) Charged dark matter Neutron star lifetime [’90 Gloud et.al.], → M DM > O(10 17 ) GeV [e.g. `01 Perl et.al.] Colored dark matter (SIMP) constrained by direct detection experiments, Earth heating → M DM > O(10 16 ) GeV [e.g. `07 Mack et.al.]

Putting Simplicity on Dark Matter How about SU(2) L charged dark matter ? The dark matter particle is the neutral component in k- tuplet of SU(2) L with U(1) Y hypercharge Y. Q = T 3 + Y = 0 ex) triplet ( k = 3 ) : | Y| = 0,1 doublet ( k = 2 ) : |Y| = 1/2 quintet ( k = 5 ) : |Y| = 0,1,2 quartet ( k = 4 ) : |Y| = 1/2, 3/2 Y = 0 : minimal dark matter SU(2) L charged [’05 Cirelli, Fornengo, Strumia ] Shigeki’s talk ! dark matter Y ≠ 0 : hypercharged minimal dark matter [ Stability : We simply assume there is a Z 2 symmetry. ] For k > 5 (7) , fermionic (scalar) dark matter is automatically stable due to an accidental symmetry [’05 Cirelli, Fornengo, Strumia ]...

Putting Simplicity on Dark Matter Is hyper-charged and SU(2) L charged dark matter can be a good candidate of weakly interacting massive particle (WIMP) ? • DM is in thermal equilibrium for T > M DM . DM number in comoving volume DM SM • For M DM < T , DM is no more created Thermal equilibrium ... • DM is still annihilating for M DM < T for a while... SM DM DM SM DM SM • DM is also diluted by the cosmic expansion Freeze out • DM cannot fi nd each other and stop DM SM annihilating at some point Increasing � σ v � • DM number in comoving volume is frozen M/T The WIMPs works for the annihilation cross section : � σ v � ∼ 10 − 9 GeV − 2 � 10 − 9 GeV − 2 � Ω DM h 2 ≃ 0 . 1 × � σ v � Minimal dark matter annihilate into the vector bosons and the fermions! 2 (2 + 17 k 2 − 19) + 4 Y 4 g 4 Y ( k 2 − 1)) � σ v � ≃ ( g 4 Y (41 + 8 Y 2 ) + 16 g 2 2 g 2 256 k π kM 2 DM → good candidate for the WIMP for M DM = O(1)TeV !

Hypercharged Minimal Dark Matter Direct dark matter detection experiments have put severe constraints on hypercharged minimal dark matter! -39 -39 -39 10 10 10 Nucleus scattering rate via Z -boson exchange XENON100 (2012) DAMA/Na ] ] ] observed limit (90% CL) 2 2 2 WIMP-Nucleon Cross Section [cm WIMP-Nucleon Cross Section [cm WIMP-Nucleon Cross Section [cm -40 -40 -40 10 10 10 Expected limit of this run: CoGeNT ± 1 σ expected DAMA/I σ χ N = G 2 F µ 2 ± 2 σ expected -41 -41 -41 10 10 10 N Y 2 ( N � (1 � 4 sin θ W ) Z ) 2 SIMPLE (2012) XENON10 (2011) 2 π COUPP (2012) CRESST-II (2012) -42 -42 -42 10 10 10 ZEPLIN-III (2012) ( x 4 for scalar DM) -43 -43 -43 XENON100 (2011) EDELWEISS (2011/12) 10 10 10 CDMS (2010/11) G F : Fermi constant, ( N,Z ) # of ( n,p ) -44 -44 -44 10 10 10 -45 -45 -45 10 10 10 6 7 8 910 6 7 8 910 6 7 8 910 20 20 20 30 30 30 40 50 40 50 40 50 100 100 100 200 200 200 300 400 300 400 300 400 1000 1000 1000 2 2 2 WIMP Mass [GeV/c WIMP Mass [GeV/c WIMP Mass [GeV/c ] ] ] The strongest limit from the XENON100 experiment : ✓ M DM ◆ σ χ Xe . 6 × 10 − 36 cm 2 → M DM > 30 PeV x (2Y) 2 , 1 TeV Hypercharged minimal dark matter cannot be a WIMP candidate...

Hypercharged Minimal Dark Matter For comparison... Direct dark matter detection experiments of minimal dark matter ( Y=0 ) The scattering is highly suppressed at the tree-level, due to the absence of tree-level interactions with Z nor Higgs. At the higher loop level, the cross section on a nucleon is estimated to be O(10 -47 )cm 2 , which is two-orders of magnitude smaller than the current limit... q q’ q q q One-loop diagrams which contribute h 0 to the triplet DM-nucleon scatterings. W- W- W- [’10 Hisano, Ishiwata, Nagata] ∼ 0 ∼ 0 ∼ − χ χ χ ∼ − ∼ 0 ∼ 0 χ χ χ Minimal dark matter ( Y=0 ) is a viable candidate of the WIMP !

Hypercharged Minimal Dark Matter Y = 0 : minimal dark matter → a viable WIMP candidate ! SU(2) L charged dark matter Y ≠ 0 : hypercharged minimal dark matter → excluded as a WIMP candidate ! Are hypercharged minimal dark matter scenarios excluded ? Let us simply discard the assumption that dark matter has attained thermal equilibrium after in fl ation... Instead, let us assume that the dark matter density is determined by a delicate choice of the dark matter mass and the temperature after in fl ation assuming M DM > T R . DM number in comoving volume Thermal equilibrium DM SM DM SM Freeze out DM SM WIMP Non-Thermal production WIMPZILLA M/T

Hypercharged Minimal Dark Matter Y = 0 : minimal dark matter → a viable WIMP candidate ! SU(2) L charged dark matter Y ≠ 0 : hypercharged minimal dark matter → excluded as a WIMP candidate ! Are hypercharged minimal dark matter scenarios excluded ? Let us simply discard the assumption that dark matter has attained thermal equilibrium after in fl ation... Instead, let us assume that the dark matter density is determined by a delicate choice of the dark matter mass and the temperature after in fl ation assuming M DM > T R . Hypercharged minimal dark matter is revived as the so-called WIMPZILLA without extending the dark matter sector at all! [ WIMPZILLA [’98 Kolb,Chung, Riotto]: weakly interacting very heavy dark matter ] Hyercharged minimal dark matter can be also revived by introducing mass splitting between Dirac neutral components to avoid the constraint from direct detection experiments... no more Simple though.

Hypercharged Minimal Dark Matter Dark Matter production during reheating between T MAX and T R During reheating After reheating H = H R (a/a R ) -3/2 H = H R (a/a R ) -2 log ρ a -3 a -3/2 In fl aton T = T R (a/a R ) -1 T = T R (a/a R ) -3/8 T MAX = T R (H inf /H R ) 1/4 [ When the in fl aton feels signi fi cant back-reaction a -4 radiation from the thermal bath, the evolutions of ρ in fl aton Reheating In fl aton and ρ R get more complicated... log a at H ≃ Γ in fl aton End of In fl ation (e.g. ’12 Mukaida & Nakayama) ] → we take T R and T MAX as free parameters Boltzmann Equation : d dtn + 3 Hn = � h � v i ( n 2 � n 2 EQ ) ( n EQ = 2 (M DM T/2 π ) 3/2 Exp[-M DM /T] ) with boundary condition : n = 0 at the end of in fl ation.

Hypercharged Minimal Dark Matter Dark Matter has attained thermal equilibrium? Production e ffi ciency Thermalized region 10 7 2.0 M DM = 10 8 GeV Thermalized T MAX < T R 10 4 DM has never attained <s v > n EQ ê H Log 10 @ M ê T max D 1.5 equilibrium x R = 10 10 10 2 1.0 M DM = 0.01 M DM = 10 8 GeV 10 3 10 10 GeV M DM = 0.5 10 - 5 10 12 GeV Thermalized 10 4 Lower T R in this region 10 - 8 0.0 0.01 0.1 1 10 100 0 1 2 3 4 5 = M DM / T x Log 10 @ M ê T R D The e ffi ciency has a peak at around M ~ T . [ Even if we take T MAX ≫ M DM , DM has not necessarily attained equilibrium! ] The e ffi ciency decreases for a lower T R for a given x ( e ffi ciency � T R2 ) The e ffi ciency decreases for a larger M DM for a given x ( e ffi ciency � M DM-1 ) In most parameter space, DM has never attained thermal equilibrium after in fl ation ! → Non-thermal Minimal Dark Matter !