Superheavy Thermal Dark Matter

Transcription

1 Superheavy Thermal Dark Matter 13th April 2018 University of Illinois at Chicago Work /w Joe Bramante [ ] & Saleh Hamdan [ ]

2 1/18 Introduction Xenon1T Unitarity

3 2/18 Superheavy Dark Matter Superheavy implies well above the unitarity limit in range PeV Mpl aka WIMPZillas Gravitational production Inflationary preheating Thermal inflation Chung, Crotty, Kolb, & Riotto [hep-ph/ ] e.g. Kofman, Linde, & Starobinsky [hep-ph/ ] Hui & Stewart[hep-ph/ ] Freeze-in production e.g. Higgs Portal: Kolb & Long [ ] Clean mechanism for Superheavy Dark Matter is thermal freeze-out followed by dilution

4 3/18 Cosmological Impact After dark matter is frozen out its number does not change from interactions. However, decaying particles can heat SM bath, & dilute YDM since s T 3. Randall, Scholtz & JU [ ] Berlin, Hooper & Krnjaic [ ] Bramante & JU [ ] Dilution factor from temperature after decays Tafter compared to without decays: Because of dilution, correct relic density for weaker interactions with SM. Changes expectation for mdm and and reduces tension with experiments.

5 4/18 Cosmological Impact Earliest cosmological evidence (know to be radiation dominated) Non-Standard Model cosmological events? End of Inflation (start of radiation domination?) {

6 Dilution of Dark Matter

7 5/18 Dilution from a Decaying State Add a state χ which becomes matter-like at Tcrit typically Tcrit=mχ Friedman equation for gives evolution of energy for with The relative energy density in χ grows until it decays at: If χ is long lived, it may evolves to dominate the energy density of Universe. χ decay heats the bath to and dilutes any frozen-out species for

8 6/18 Relic Density after Dilution Consider standard dark matter freeze-out followed by dilution For mediator and DM of similar mass, assuming s-wave annihilation, then and parametrically Entropy injections permit correct relic density for smaller couplings. Superheavy Dark Matter arises readily for modest entropy injections.

9 7/18 Relic Density after Dilution The dilution ζ needed to match the relic density for given s-wave p-wave Unitarity bound relaxed perturbative unitarity However, entropy injection also dilutes particle asymmetries 10-5 αdm = 10-2 αdm = 4π ζ αdm = baryon asymmetry Bramante & JU [ ] mdm (GeV) Maximum dilution assuming high scale baryogenesis Unitarity limit relaxed to GeV

10 8/18 Parameter Space To dilute dark matter via χ decay and avoid cosmological constraints: a). Assume: Universe radiation dominated during freeze-out b). Decay of χ prior to BBN c). Decay of χ after dark matter freeze-out The requirement can be expressed Tcrit = mχ < TFO which bounds χ Freeze-out during matter domination possible, but changes calculation.

11 8/18 Parameter Space To dilute dark matter via χ decay and avoid cosmological constraints: a). Assume: Universe radiation dominated during freeze-out b). Decay of χ prior to BBN c). Decay of χ after dark matter freeze-out The BBN constraint implies > 10 MeV. Assuming and BBN constraints imply

12 8/18 Parameter Space To dilute dark matter via χ decay and avoid cosmological constraints: a). Assume: Universe radiation dominated during freeze-out b). Decay of χ prior to BBN c). Decay of χ after dark matter freeze-out For dark matter to be diluted rather than repopulated require that energy injection occurs after dark matter freeze-out This implies which constrains or equivalently

13 9/18 Parameter Space Putting this together, the parameter space for and 8 Log[mχ/GeV] TFO<TRH TRH = 10 TeV Freeze-out matter dominated TRH = 100 GeV TRH = 1 GeV TRH < TBBN = 10 MeV Bramante & JU [ ] Log[mDM/GeV]

14 Matter Dominated Freeze-out

15 10/18 Changes to the Expansion Rate Notable, expansion rate H depends critically on cosmology: During radiation domination During particle decays (heating) Giudice, Kolb, and Riotto, PRD 64 (2001) During matter domination Hamdan & JU [ ] Also: Kamionkowski & Turner PRD 42 (1990) 3310 Recall TFO is defined, changing TFO impacts final YDM.

16 11/18 Matter Dominated Freeze-out One can emulate the standard Boltzmann treatment but with different form for H for 1 RD 0 MD Where is temperature χ becomes matter-like and Radiation dominated freeze-out Matter dominated freeze-out Scherrer and Turner, PRD 33 (1986) 1585 Hamdan & JU [ ]

17 12/18 Matter Dominated Freeze-out YDM in matter dominated FO different to radiation dominated case. Radiation domination restored after freeze-out as matter decays to SM. Required because observations imply radiation domination prior to current epoch. 0.0 This leads to dilution ζ of the dark matter abundance: Contours of Ω X h 2 = 0.1 ζ=10-2 ζ=10-3 More dilution implies smaller couplings Again, weakening search limits compared to radiation dominated FO. Log 10 α ζ= Radiation Domination -2.5 Matter Domination with T * = 10 6 GeV Log10[mDM/GeV] X Hamdan & JU [ ]

18 13/18 Matter Dominated Freeze-out For DM freeze-out during matter domination, whilst avoiding cosmological constraints: a). Universe matter dominated during freeze-out b). Decay of χ prior to BBN c). Decay of χ after dark matter freeze-out d). χ decays negligible during dark matter freeze-out o.w./ similar to Giudice, Kolb, and Riotto, PRD 64 (2001) e). Decays of χ prior to EWPT (optional - model dependent)

19 14/18 MDFO Parameter space Putting this together, the parameter space for, and 15 T Γ > T MD FO ϕ decays before freeze-out T RH > TMD FO T RH = 10 4 GeV 10 2 GeV Log 10 [mϕ/gev] GeV BBN 0 TRD FO > TMD Freeze-out before matter domination Log10[mDM/GeV] X Hamdan & JU [ ]

20 Superheavy Asymmetric DM

21 15/18 Asymmetric Dark Matter Suppose dark matter carries a conserved quantum number analogous to B or L. Dark matter could have particle-antiparticle asymmetry, similar to baryons. ADM: dark matter asymmetry can be responsible for DM relic density Requires the abundance of particle anti-particle pairs ADM implies the relationship Classic models favour mdm ~ 5 GeV

22 Superheavy Asymmetric Dark Matter Superheavy ADM needs a much smaller asymmetry 16/18 For DM to be asymmetric the symmetric component must annihilate. Thus a form of the unitarity bound remains for ADM. Baldes & Petraki [ ] Heavy ADM possible via entropy injection: Now entropy injection dilutes both asymmetries and frozen out species For appropriate parameters relic abundance is correct and

23 17/18 Dilution of DM Asymmetry The dilution ζ needed to match the relic density for given -4-6 ζ = 10-8 ζ = αdm = 0.3 αdm = 0.05 initial Log[ηDM ] ζ = 10-6 ζ = 10-4 ζ = 10-2 ζ = Log[mDM/GeV] Transition to vertical implies symmetric component becomes dominant. Bramante & JU [ ]

24 Conclusion 18/18 Entropy injection is simple extension and can drastically alter expectations. Dilution permit correct relic density for heavier DM or smaller couplings. High scale baryogenesis implies maximum dilution & unitarity limit of GeV Superheavy dark matter can potentially give (spectacular) signals. Superheavy ADM impacts neutron stars & perhaps solve missing pulsar problem. Early periods of matter domination may also have observable implications. Thank you. e.g. Blasi, Dick, Kolb [astro-ph/ ] See talk of Tim Linden. See talk of Adrienne Erickcek.