Observing the dark sector with supernovae W. DeRocco, 1 P. Graham, 1 - - PowerPoint PPT Presentation

Observing the dark sector with supernovae

• W. DeRocco,1 P. Graham,1 D. Kasen,2 G. Marques-Tavares,3 S. Rajendran2

1Stanford University 2University of California, Berkeley 3University of Maryland 1

(hep-ph: 1901.08596) (hep-ph: 1905.09284)

September 2019 TAUP ‘19

Outline

• Part I: Supernova (SN) production of MeV-scale particles is large well

below cooling bound.

• Part II: Decay products of SN-produced dark photons can be
• bserved. (hep-ph: 1901.08596)
• Part III: SN-produced light dark matter is detectable in existing WIMP
• detectors. (hep-ph: 1905.09284)

2

Outline

• Part I: Supernova (SN) production of MeV-scale particles is large well

below cooling bound.

• Part II: Decay products of SN-produced dark photons can be
• bserved. (hep-ph: 1901.08596)
• Part III: SN-produced light dark matter is detectable in existing WIMP
• detectors. (hep-ph: 1905.09284)

3

Supernovae

4

PNS

Neutrino sphere

Overburden

• Core-collapse of massive

star releases >1053 erg

• Protoneutron star (PNS)

has temperature ~30 MeV

• Neutrinos diffuse inside

“neutrino sphere” then free- stream, cooling PNS

Supernova cooling constraint

• Core-collapse of massive

star releases >1053 erg

• Protoneutron star (PNS)

has temperature ~30 MeV

• Neutrinos diffuse inside

“neutrino sphere” then free- stream, cooling PNS

• 10-second cooling

timescale observed during SN1987a

• Cooling constraint: new

particle cannot transfer more energy than neutrinos

5

PNS

Neutrino sphere

Overburden

Motivation for our work

• Even below cooling limit,

flux of MeV-scale particles can still be very large

• Direct observation can

constrain where cooling bound fails!

6 Previous bounds on dark photon. Chang, Essig, McDermott (2016)

flux still large...

Coupling to Standard Model

Outline

• Part I: Supernova (SN) production of MeV-scale particles is large well

below cooling bound.

• Part II: Decay products of SN-produced dark photons can be
• bserved. (hep-ph: 1901.08596)
• Part III: SN-produced light dark matter is detectable in existing WIMP
• detectors. (hep-ph: 1905.09284)

7

Dark photon

• Kinetic mixing 𝜗 with SM

photon

• Decay modes:
• 𝒇#𝒇$
• 𝒇#𝒇$ 𝜹 (~1%)

8

Decays

𝑓$ 𝑓# 𝛿 𝐵*

Observable signatures

• Below cooling bound,

supernovae still produce many dark photons

• Dark photons escape

from SN and decay

• Decay products leave
• bservable signatures

9

PNS Radius of progenitor star

𝑓$ 𝑓# 𝛿 𝐵*

Shock 3) 511 keV line 1) Prompt gamma ray burst 2) Diffuse extragalactic flux

Signature #1: Positron annihilation

• Positrons slow and

annihilate in galaxy

• Constrained by

INTEGRAL measurement of 511 keV line

10

Late decays Cooling Positrons BBN

1 5 10 50 100

• 13
• 12
• 11
• 10
• 9
• 8
• 7

m' (MeV) log ϵ

More production, shorter decay length More Boltzmann suppressed

Signature #2: Diffuse extragalactic gamma rays

• Decay products can

form 𝑓#𝑓$ plasma (“fireball”)

• Diffuse extragalactic

flux of gamma rays measured by SMM

11

Late decays Cooling Positrons Diffuse γ BBN

1 5 10 50 100

• 13
• 12
• 11
• 10
• 9
• 8
• 7

m' (MeV) log ϵ

More production, shorter decay length More Boltzmann suppressed

Signature #3: Prompt gamma rays

• SN1987a gamma

ray emission constrained by GRS

• Discovery potential

(next galactic supernova)

12

Late decays Cooling Positrons Diffuse γ SN1987a BBN

1 5 10 50 100

• 13
• 12
• 11
• 10
• 9
• 8
• 7

m' (MeV) log ϵ

More production, shorter decay length More Boltzmann suppressed

Outline

• Part I: Supernova (SN) production of MeV-scale particles is large well

below cooling bound.

• Part II: Decay products of SN-produced dark photons can be
• bserved. (hep-ph: 1901.08596)
• Part III: SN-produced light dark matter is detectable in existing WIMP
• detectors. (hep-ph: 1905.09284)

13

Dark fermion

• ** Different model than

previous section **

• Dark sector with stable

fermion (𝜓)

• DM-SM coupling through

heavy dark photon (𝐵′)

14

𝜓 𝜓

SM SM Production Scattering

Diffusive trapping

• Above cooling bound,

particles diffusively trapped by SM scattering

• Spectrum set by radii at

which interactions decouple

15

Number sphere Energy sphere Scattering sphere Annihilation stops: number flux set DM thermally decouples: energy spectrum set DM free streams

Pr Produc uction/ n/anni nnihi hilation En Ener ergy tr tran ansfer er Di Diffusive e scatter cattering

χ ¯ χ ← → e+ e− χ e − → χ e χ p − → χ p

Diffusive trapping

• Above cooling bound,

particles diffusively trapped by SM scattering

• Spectrum set by radii at

which interactions decouple

16

Number sphere Energy sphere Scattering sphere Annihilation stops: number flux set DM thermally decouples: energy spectrum set DM free streams

Pr Produc uction/ n/anni nnihi hilation En Ener ergy tr tran ansfer er Di Diffusive e scatter cattering

χ ¯ χ ← → e+ e− χ e − → χ e χ p − → χ p

Diffuse galactic flux

• Dark fermions are produced at semirelativistic velocities
• Emissions from several SN overlap to form diffuse flux
• High-momentum population detectable in liquid xenon

17

~3000 ly

Detector Supernova ~10 seconds ~3000 years

Direct detection

• Diffuse flux has

high momentum

• WIMP detectors

sensitive to diffuse flux of MeV-scale dark sector

18

Stronger coupling, diffusively trapped Weaker coupling, free-streaming More Boltzmann suppressed

Relic Density BBN DARWIN (200 ton-yrs) LZ (15 ton-yr) Xenon1T (1 ton-yr) C

• l

i n g Threshold: 2.5 keV Emission Δt: log(10) s Source: diffuse galactic flux 5 10 50 100

• 24
• 22
• 20
• 18
• 16
• 14
• 12
• 10

mX (MeV) log y

𝑧 = 𝛽0𝜗1 𝑛3 𝑛4*

5

Conclusions

• Part I: Supernova (SN) production of MeV-scale particles is large well

below cooling bound.

• Part II: Decay products of SN-produced dark photons can be
• bserved. (hep-ph: 1901.08596)
• Part III: SN-produced light dark matter is detectable in existing WIMP
• detectors. (hep-ph: 1905.09284)

19

Thank you!

20

Discrimination

• Very weak bounds

in cosmologically- excluded region

21

Horizontal branch stars SN1987a gamma rays EGRB EGRB (gaNN = gaγγ) Cooler profile Hotter profile 0.001 0.005 0.010 0.050 0.100 0.500 1

• 1. ×10-11
• 2. ×10-11
• 5. ×10-11
• 1. ×10-10
• 2. ×10-10

mA (MeV) gaγγ (GeV-1)

Discrimination

• Recoil spectra of

cold WIMPs and hot MeV-scale DM very similar

• How can we

discriminate these two populations?

22

Recoil spectra in liquid xenon for different DM mass

BBN

5 ton-yr 1 ton-yr

SN cooling He/CF4 (70:30) Emission Δt: 10 s diffuse galactic flux He: 1 keV C: 2 keV F: 3 kev 5 10 50 100

• 18
• 17
• 16
• 15
• 14
• 13

mX (MeV) log y

Direct detection

• Low-threshold

directional detectors (e.g. CYGNUS) sensitive to diffuse flux

23

Stronger coupling, diffusively trapped Weaker coupling, less production More Boltzmann suppressed

𝑧 = 𝛽0𝜗1 𝑛3 𝑛4*

5

BBN

5 ton-yr 1 ton-yr

SN cooling He/CF4 (70:30) Emission Δt: 10 s diffuse galactic flux He: 1 keV C: 2 keV F: 3 kev 5 10 50 100

• 18
• 17
• 16
• 15
• 14
• 13

mX (MeV) log y

Direct detection

• Low-threshold

directional detectors (e.g. CYGNUS) sensitive to diffuse flux

24

Stronger coupling, diffusively trapped Weaker coupling, less production More Boltzmann suppressed

𝑧 = 𝛽0𝜗1 𝑛3 𝑛4*

5

SN production

• Diffuse flux strongly

peaked towards Galactic center

• Isotropic intergalactic

contribution highly subdominant

25

• 3
• 2
• 1

1 2 3

• 1.5
• 1.0
• 0.5

0.0 0.5 1.0 1.5 ϕ (rad) ψ (rad)

• mX = 11 MeV

y = 1e-16 All-sky flux: ~104 cm-2 s-1 Note: 100 GeV WIMP ~ 105 cm-2 s-1 log9: Φ (cm-2 s-1 sr -1)

Discrimination

• Diffuse flux strongly

peaked towards Galactic center

• SN signal is

perpendicular to WIMPs!

• Directional

detectors are necessary for discrimination of any future signal

26

Cygnus Galactic center SN signal WIMP signal