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. Rajendran 2 1 Stanford University 2 University of California, Berkeley 3 University of Maryland (hep-ph: 1901.08596) (hep-ph: 1905.09284) September 2019 TAUP ‘19 1

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 observed. (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 observed. (hep-ph: 1901.08596) • Part III: SN-produced light dark matter is detectable in existing WIMP detectors. (hep-ph: 1905.09284) 3

Supernovae • Core-collapse of massive star releases >10 53 erg Overburden • Protoneutron star (PNS) has temperature ~ 30 MeV • Neutrinos diffuse inside “neutrino sphere” then free- stream, cooling PNS PNS Neutrino sphere 4

Supernova cooling constraint • Core-collapse of massive star releases >10 53 erg Overburden • Protoneutron star (PNS) has temperature ~ 30 MeV • Neutrinos diffuse inside “neutrino sphere” then free- stream, cooling PNS PNS • 10-second cooling timescale observed during SN1987a Neutrino • Cooling constraint: new sphere particle cannot transfer more energy than neutrinos 5

Motivation for our work • Even below cooling limit, flux of MeV-scale Coupling to Standard Model particles can still be very large • Direct observation can constrain where cooling bound fails! flux still large... Previous bounds on dark photon. Chang, Essig, McDermott (2016) 6

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 observed. (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 𝑓 $ • Decay modes: Decays • 𝒇 # 𝒇 $ • 𝒇 # 𝒇 $ 𝜹 (~1%) 𝐵 * 𝛿 𝑓 # 8

Observable signatures • Below cooling bound, supernovae still 𝑓 $ produce many dark photons 1) Prompt gamma 𝐵 * ray burst 𝛿 • Dark photons escape from SN and decay 2) Diffuse extragalactic flux PNS • Decay products leave observable signatures Shock 𝑓 # 3) 511 keV line Radius of progenitor star 9

Signature #1: Positron annihilation - 7 • Positrons slow and More production, annihilate in galaxy shorter decay length Cooling - 8 • Constrained by INTEGRAL - 9 measurement of 511 keV line Late decays log ϵ - 10 Positrons - 11 - 12 BBN - 13 1 5 10 50 100 More Boltzmann suppressed m' ( MeV ) 10

Signature #2: Diffuse extragalactic gamma rays - 7 • Decay products can More production, form 𝑓 # 𝑓 $ plasma shorter decay length Cooling - 8 (“fireball”) • Diffuse extragalactic - 9 flux of gamma rays measured by SMM Diffuse γ Late decays log ϵ - 10 Positrons - 11 - 12 BBN - 13 1 5 10 50 100 More Boltzmann suppressed m' ( MeV ) 11

Signature #3: Prompt gamma rays - 7 • SN1987a gamma More production, ray emission shorter decay length Cooling - 8 constrained by GRS • Discovery potential - 9 (next galactic supernova) Diffuse γ Late decays log ϵ - 10 Positrons - 11 SN1987a - 12 BBN - 13 1 5 10 50 100 More Boltzmann suppressed m' ( MeV ) 12

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 observed. (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 ** 𝜓 SM • Dark sector with stable fermion ( 𝜓 ) • DM-SM coupling through heavy dark photon ( 𝐵′ ) Scattering 𝜓 SM Production 14

Diffusive trapping • Above cooling bound, particles diffusively trapped by SM scattering • Spectrum set by radii at which interactions decouple Number Pr Produc uction/ n/anni nnihi hilation sphere Annihilation stops: → e + e − number flux set χ ¯ χ ← Energy sphere Ener En ergy tr tran ansfer er DM thermally Scattering decouples: energy χ e − → χ e sphere spectrum set Diffusive Di e scatter cattering DM free streams χ p − → χ p 15

Diffusive trapping • Above cooling bound, particles diffusively trapped by SM scattering • Spectrum set by radii at which interactions decouple Number Pr Produc uction/ n/anni nnihi hilation sphere Annihilation stops: → e + e − number flux set χ ¯ χ ← Energy sphere Ener En ergy tr tran ansfer er DM thermally Scattering decouples: energy χ e − → χ e sphere spectrum set Diffusive Di e scatter cattering DM free streams χ p − → χ p 16

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 Supernova Detector ~3000 ly ~3000 years ~10 seconds 17

Direct detection • Diffuse flux has - 10 high momentum Relic Density - 12 Stronger • WIMP detectors coupling, DARWIN ( 200 ton - yrs ) diffusively sensitive to diffuse - 14 trapped LZ ( 15 ton - yr ) flux of MeV-scale Xenon1T ( 1 ton - yr ) BBN - 16 dark sector log y - 18 - 20 𝑧 = 𝛽 0 𝜗 1 𝑛 3 5 g n i l o o 𝑛 4* C - 22 Threshold: 2.5 keV Emission Δ t: log ( 10 ) s Weaker coupling, Source: diffuse galactic flux - 24 free-streaming 5 10 50 100 More Boltzmann suppressed mX ( MeV ) 18

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 observed. (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 2. × 10 - 10 in cosmologically- Horizontal branch stars excluded region 1. × 10 - 10 EGRB SN1987a gamma rays g a γγ ( GeV - 1 ) 5. × 10 - 11 2. × 10 - 11 EGRB ( g aNN = g a γγ ) Cooler profile 1. × 10 - 11 Hotter profile 0.001 0.005 0.010 0.050 0.100 0.500 1 m A ( MeV ) 21

Discrimination • Recoil spectra of Recoil spectra in liquid xenon for different DM mass cold WIMPs and hot MeV-scale DM very similar • How can we discriminate these two populations? 22

Direct detection - 13 • Low-threshold directional detectors (e.g. - 14 Stronger coupling, 5 ton - yr CYGNUS) sensitive diffusively trapped to diffuse flux - 15 log y BBN 1 ton - yr SN cooling - 16 𝑧 = 𝛽 0 𝜗 1 𝑛 3 5 𝑛 4* - 17 He / CF4 ( 70:30 ) He: 1 keV Emission Δ t: 10 s C: 2 keV Weaker diffuse galactic flux F: 3 kev coupling, less production - 18 5 10 50 100 mX ( MeV ) More Boltzmann suppressed 23

Direct detection - 13 • Low-threshold directional detectors (e.g. - 14 Stronger coupling, 5 ton - yr CYGNUS) sensitive diffusively trapped to diffuse flux - 15 log y BBN 1 ton - yr SN cooling - 16 𝑧 = 𝛽 0 𝜗 1 𝑛 3 5 𝑛 4* - 17 He / CF4 ( 70:30 ) He: 1 keV Emission Δ t: 10 s C: 2 keV Weaker diffuse galactic flux F: 3 kev coupling, less production - 18 5 10 50 100 mX ( MeV ) More Boltzmann suppressed 24

SN production • Diffuse flux strongly m X = 11 MeV 1.5 y = 1e-16 peaked towards Galactic center All-sky flux: 1.0 ~10 4 cm -2 s -1 • Isotropic intergalactic log 9: Φ (cm -2 s -1 sr -1 ) 0.5 contribution highly ���� subdominant ψ ( rad ) ���� 0.0 ���� ���� ���� - 0.5 ���� ���� ���� - 1.0 ���� ���� ���� - 1.5 Note: 100 GeV WIMP - 3 - 2 - 1 0 1 2 3 ~ 10 5 cm -2 s -1 ϕ ( rad ) 25

Discrimination • Diffuse flux strongly peaked towards Galactic center Cygnus • SN signal is Galactic center perpendicular to WIMPs! SN signal • Directional detectors are WIMP signal necessary for discrimination of any future signal 26