Production of High-Energy and Ultrahigh-Energy Neutrinos Kohta Murase (Penn State) November 30 Snowmass 2021 All-Sky Neutrino Spectrum & Flavors 2 -8 -2 -1 -1 All-sky n flux per flavor En Fn ~ 10 GeV cm s sr at En ~200 TeV Flavor ratio consistent with ne:nµ:nt ~ 1:1:1 possible structure? cutoff? - 9.5-yr upgoing nµ “track” s=2.28+0.08-0.09 - 6-yr “shower/cascade” s=2.53+-0.07 IceCube Collaboration @ Neutrino 2020 IceCube Collaboration 20 PRL arXiv:2008.04323 Multi-Messenger Astro-Particle “Backgrounds” gamma neutrino UHECR unresolved Energy generation rate densities of 3 messengers are all comparable (e.g., KM & Fukugita 19 PRD) High-Energy Neutrino Sky upgoing tracks starting events consistent w. isotropic distribution/extragalactic origins IceCube Point Source Searches IceCube Collaboration 20 PRL starburst galaxy/AGN NGC 1068 TXS 0506+056 PKS 1414+240 GB6 J1542+6129 Jetted AGN (blazar) “Catches” (~3s) exist but none have reached the discovery level Key questions What we know: 2 -8 -2 -1 -1 - En Fn ~ 10 GeV cm s sr , Flavor ratio is consistent w. 1:1:1 - Energy budget: comparable to those of g rays & UHECRs - A few sources w. ~3s (NGC 1068 & TXS 0506+056) Key (astrophysical) questions we would like to reveal: • What is the main sources of IceCube neutrinos? • What is the connection to the sources of g rays and UHECRs? • How does the n spectrum extend & Is there a structure? • What is the mechanism of n production (pp or pg or…)? • Can we expect neutrinos coinciding with gravitational waves? • How can we use ns to probe astrophysical phenomena? • How much is the Galactic contribution? 8 1 2 2 1 2 3 2 2 ∆φ = ⌦ BpR ✓0/c ⌦ BpR ✓0/c (67) 2 ⇤ ⇤ ⇠ 2 ⇤ ⇤ 6.6 1012 V (68) ⇥ E<Ze∆φ (69) 2 1 E0 0.05E0 0.8 PeV Γ (E0 /1 keV)− (70) ⌫ ⇡ p ' 1 s ' (71) 2 ↵ 1 (72) − ⇠ 2 β (0 1) (73) − ⇠ − High-Energy 2Neutrino↵ 2.3 Production (74) − ⇠ Cosmic-ray Accelerators Cosmic-ray Reservoirs Starburst galaxy Galaxy cluster Active galaxy g-ray burst 2 β 2 (75) accretion to core-collapse of − ⇠high star-formation gigantic reservoirs w. massive black hole massive stars → many supernovae AGN, galaxy mergers s resonance spp pg + spg~aspp~0.5 mbp + γ n + ⇡ (76) ! weak energy dependence ε'pε’γ ~ (0.34 GeV)(mp/2) ~ 0.16 GeV2 spp~30 mb p + γ N⇡ + X (77) ! p +γ → Nπ + X p + p → Nπ + X ⇡± ⌫ +¯⌫ + ⌫ (or⌫ ¯ )+e± (78) ! µ µ e e 2 c dz dH E⌫ Φ⌫ = [ns"⌫ L"⌫ ] n0L⌫ (79) 4⇡ (1 + z)2H(z) / 4⇡ Z (0.4 0.6) (80) p ⇠ − 0.2 (81) p ⇠ L Lγlw (82) ⌫ / γ High-Energy Neutrino Production Cosmic-ray Accelerators Cosmic-ray Reservoirs Starburst galaxy Galaxy cluster Active galaxy g-ray burst accretion to core-collapse of high star-formation gigantic reservoirs w. massive black hole massive stars → many supernovae AGN, galaxy mergers relativistic outflow ex. shocks in outflow → electron acceleration e+ µ → synchrotron emission + target gas nµ p+ nµ ne CR p e+ n p ne CR e e+ + CR accelerator target g µ n CR confinement + µ p n n CR p e+ µ e magnetized “environments” n p ne High-Energy Neutrino Production Cosmic-ray Accelerators Cosmic-ray Reservoirs Starburst galaxy Galaxy cluster Active galaxy g-ray burst accretion to core-collapse of high star-formation gigantic reservoirs w. massive black hole massive stars → many supernovae AGN, galaxy mergers relativistic outflow ex. shocks in outflow → electron acceleration e+ µ → synchrotron emission + target gas nµ p+ nµ ne CR p e+ n p ne CR e e+ + CR accelerator target g µ n CR confinement + µ p n n CR p e+ µ e magnetized “environments” n p ne 3 2 2−p olate the local 1.4 GHz energy production rate per unit neutrino spectrum would be, Eν Φνµ ∝ Eν .Theenergy volume (of which a dominant fraction is produced in qui- distribution of cosmic-ray protons measured on Earth fol- −2.75 No. 2, 2008 COSMICescent spiral RAYS galaxies) AND NEUTRINOSto the redshifts FROM where most CLUSTERS of the OFlows GALAXIES a power-law dN/dE ∝ E up L107 to the ”knee” in stars had formed through the starburst mode, based on the cosmic-ray spectrum at a few times 1015 eV [23, 25]. the observed redshift evolution of the cosmic star forma- (The proton spectrum becomes steeper, i.e. softer, at tion rate [24], and calculate the resulting neutrino back- higher energies [2].) Given the energy dependence of the ground. The cumulative GeV neutrino background from confinement time, ∝ E−s [22], this implies a produc- starburst galaxies is then tion spectrum dN/dE ∝ E−p with p =2.75 − s ≈ 2.15. This power-law index is close to, but somewhat higher IceCube c E2Φ (E =1GeV)≈ ζt [4ν(dL /dV )] than, the theoretical value p =2,whichimpliesequal ν ν ν 4π H ν ν=1.4GHz IceCube −7 −2 −1 −1 energy per logarithmic particle energy bin, obtained for =10 ζ0.5 GeV cm s sr . (2) Fermi acceleration in strong shocks under the test par- ticle approximation [26]. We note that the cosmic-ray Here, t is the age of the Universe, and the factor H spectrum observed on Earth may not be representative ζ =100.5ζ incorporates a correction due to redshift 0.5 of the cosmic-ray distribution in the Galaxy in general. evolution of the star formation rate relative to its present- galaxy group/clusterThe inferred excess relative to model predictions of the day value. The value of ζ ∼ 1appliestoactivitythat 0.5 > 1GeVphotonfluxfromtheinnerGalaxy,impliesthat traces the cosmic star formation history [6]. Note that the cosmic-rays are generated with a spectral index p Koteraflavor, Allard, oscillationsKM, Aoi, wouldDubois, convert the pion decay flavor ra- smaller than the value p =2.15 inferred from the local Pierogtio, &ν Nagataki: ν : ν 09=1:2:0to1:1:1[11],sothat ApJ KM, Inoue & Nagataki 08 ApJ e µ τ cosmic-ray distribution, and possibly that the spectral Φ = Φ = Φ = Φ /2. νe νµ ντ ν index of cosmic-rays in the inner Galaxy is smaller than the local one [27]. The spectrum of electrons accelerated −5 10 in SNe is inferred to be a power law with spectral index Fig. 1.—Expected event rates for muon neutrinos (nmmϩ n¯ ) in IceCube-like p =2.1 ± 0.1overawiderangeenergies,∼ 1GeVto starburst galaxyFig. 2.—Cumulative neutrino (neeϩ n¯¯¯ϩ nmmttϩ n ϩ n ϩ n ) background from detectors from five nearby CGs: Virgo, Centaurus, Perseus, Coma, and Oph- ∼ 10 TeV, based on radio, X-ray and TeV observations CGs for broken power-law>0.1 CR spectra PeV withpIceCube12p 2.0 andp p 2.4data: . The break −6 p p p 17.5 16.5 iuchus. Broken power-law CR spectra with10 p122.0 ,p 2.4 , and ␧b p (e.g. [28]). p 17.5 energies are␧bb10 eV (thick lines) and␧ 10 eV (thin lines), re- AMANDA(νp); Baikal(ν ) 245Ϫ3 10 eV is assumed, and the isobaric model withXCR µ 0.029 ise used. Note spectively. The CR powerconsistent isFor normalized a steeply to falling␧ ( dnw.˙/d␧ proton) earlierp 2 # spectrum10 erg Mpc such as dN/dE ∼ s sr] 1 18 that IceCube and KM3NeT mainly cover2 the northern and southern celestial Ϫ −2 yr at␧ p 10 eV, as requiredE ,theproductionofneutrinosofenergy to account for CRs above the second knee. Eν is domi- hemispheres, respectively. Neutrino oscillation is taken into account. [See the For the isobaric model,theoretical the correspondingX predictions is 0.029 and 0.067. For the −7 nated by protonsCR of energy E ≈ 20Eν [18], so that the electronic edition of the Journal for a color10 version of this figure.] central-AGN model, Kolmogorov-like turbulence is assumed with k p WB Bound cosmic-ray ”knee” corresponds to E ∼CG0.1PeV.Inanal- IceCube 30 2 Ϫ1 p p p ν [GeV/cm 10 cm s . We taketdynDt 1 Gyr andz max 2 . WB represents the ν Star Bursts ogy with the Galactic injection parameters of cosmic- Φ Waxman-Bahcall bounds (Waxman & Bahcall 1998). culations of the neutrino spectra using formulae based on the 2 2 ν 0.1 km rays, we expect the neutrino background to scale as E −8 SIBYLL code at high energies (Kelner10 et al. 2006). 2 SB −7 −0.15±0.1 −2 −1 −1 The neutrino and gamma-ray fluxes can be estimated via the where CGs are assumedEν Φν to≈ be10 the( mainEν /1GeV) sources of CRsGeV from cm s sr (3) Atmospheric→ 2 the second knee to the ankle. Here,n (0) is the local density effective optical depth for the pp reaction as fpp1 km ← GZK up to ∼ 0.1PeV.Infact,the”knee”intheprotonspec-CG −9 Loeb & Waxman 06 JCAP≈ 0.8jppnct N int, where nN is the target10 nucleon density in the ICM, of massive CGs andfz is a correction factor for the source 3 5 7 9 11 trum for starburst galaxies may occur at an energy higher 10 10 10 evolution10 (Murase10 2007; Waxman & Bahcall 1998). For de- jpp is the pp cross section, and tint tdyn or max(r/c , tdiff)E is [GeV] the than in the Galaxy. The steepening (softening) of the ∼ Ϫ4.5 Ϫ3 ν pp interaction time. BecausenN 10 cm atr 1.5 Mpc tailed numerical calculationsproton spectrum of the background, at the knee we may treat be more either due to a ∼ ∼ distant CGs following Colafrancesco & Blasi (1998) adopting (Colafrancesco & Blasi 1998;FIG.