High-Energy Neutrinos
from Cosmic Explosions

Kohta Murase
Institute for Advanced Study, USA
	
SN-GRB Conference
November 2013

IceCube

Dawn of High-Energy Neutrino Astrophysics
Neutrino sky map⇤ at very high energies

IceCube Lab

I 5160 PMTs

Until
86 strings
June
2012
17 m PMT-PMT

50 m

I 1 km3 volume
II

spacing per string
1450 m

I 120 m string

spacing
I Angular resolutiono2450 mSkymap:⇠ No
1 Significant Clustering
I Completed 2010

* CR background removed

June 2012
2 events at PeV
May 2013
28 events > 30 TeVMarkus Ahlers (UW-Madison)

GRBs at Neutrino Telescopes

May 11, 2012

N. Whitehorn, UW Madison

Deep Core

2820 mEiffel Tower
324 m

Outline
GRBs & SNe = violent cosmic explosionsat deaths of massive stars- GRB-SN connection?, jet properties?
- CR origin?, CR acceleration?
Overview of GRBs/SNe as HE ν sources
1. GRBs as UHECR origin?
2. HE neutrinos from subphotospheres?
3. Origin of sub-PeV neutrinos in IceCube?

GRB

SN

Motivation: Cosmic Rays – A Century Old Puzzle
UHECR budget (from obs.):
QHECR ~ 1044 erg/Mpc3/yr
UHECR energy output~ GRB radiation energy
EHECRiso ~ Eγiso ~ 1053 erg

E-2.7
Galactic

local GRB rate density:
extragalactic?
~ 1 Gpc-3 yr-1
E-3.0
E-3.3

PeV

E-2.6

(ex. Wanderman & Piran 10, Dermer 12)

	
UHECR acc. is allowed
εp < erB ~ 3x1020 eV r14B4(Waxman 1995, Vietri 1995)※ many theoretical issues I do not discuss

HE Neutrinos as a Smoking Gun
p + γ → Nπ + X
σpγ ~ a few x 10-28 cm2

GRB γ	

baryonic resonances,direct production,
multi-pion production etc.

e+	

µ+	

π+	

p
n

e+	

νe	

νµ	

νe	

νµ	

p

at Δ-resonance (εpεγ ~ 0.2Γ2 GeV2)ενb ~ 0.05εpb ~ 0.01 GeV2 Γ2/εγ,pk ~ 1 PeV (if εγ,pk ~ 1 MeV)
Meson production efficiency (large astrophysical uncertainty)
fpγ ~ 0.2nγσpγ(r/Γ) ∝ r-1Γ-2 ∝ Γ-4δt-1 (if IS scenario r ~ Γ2δt)	

parameters for fpγ (Lγ, photon spectrum, Γ, r (or δt)) + ECR (ex. ~10 Eγ)

Neutrino Spectra
CR Spectrum (Fermi mechanism)

N(εp) ∝ εp-s (s~2 assumed)

EHECR ≡ εp2N(εp) ~ Eγ (GRB-UHECR)
ECR = ∫dεp εp N(εp) ~ 20 EHECR

Photon Spectrum (observed)

Neutrino Spectrum

εγ2N(εγ)

Waxman & Bahcall 97 PRL

εν2N(εν)

α-1+2-s~02-β~-02-α~1.0

meson
coolingβ-1+2-s~1

α-3+2-s~-2.0ενεγ
εγ,pk~ MeV

εmax

more detailed microphysics- higher resonances & multi-pion production- CR cooling (photomeson, photopair, syn., IC)- muon, pion, kaon w. their cooling- neutrino mixing
ex. KM & Nagataki 06 PRD, Baerwald+ 11 PRD

ενb ~ PeV

numerical

ενπsynPossible Neutrino Production Sites
Meszaros (2001)

Inner jet (prompt/flare)r ~ 1012-1016 cm B ~ 102-6 G
PeV ν, GeV-TeV γ
Waxman & Bahcall 97 PRL	

Dermer & Atoyan 03 PRL
KM & Nagataki 06 PRL	Afterglow
B ~ 0.1-100 G
EeV ν, GeV-TeV γe.g., Waxman & Bahcall 00 ApJ
Dermer 02 ApJ
KM 07 PRD	r ~ 1014-1017 cm

Recent
IceCube Limits on Prompt ν Emission
RESEARCH
LETTER

10–9

10–1

IC40+59 Allowed (90% C
IC40+59 Allowed (95% C
10–7
4
Theor. predictionWaxman(but 8see below)
RachenAhlers10Eν2Φν (GeV cm–2 s–1 sr–1)

100

Waxman and Bahcall
IC-40
IC40 Guetta et al.
IC40+59 Combined
limit
IC40+59 Guetta
et al.

E 2Fν (GeV cm–2)

E 2Φ ν (GeV cm–2 s–1 sr–1)

10–8

10–8 limit (based on stacking)
Obs.

10–9

IceCube collaboration 12 Nature
104

105

106

107

Neutrino energy (GeV)

Observational
to bebased
powerful
10–10 4
Figure 1 | Comparison limitsof results start
to predictions
on observedbut
c-raybe careful
10105
6,9,19spectra.
Theenergy-dependent,
summed flux predictions normalized
to c-ray spectra1.
fpγ isπ-cooling→ ~ 4 ↓are(Li 11, Hummer etNeutrino
al. 12)break ener
shown as a function of neutrino energy (E) in dashed lines, with the dark grey2.
(εγ2lineφγlabelledat εγ,pk) ≠Guetta(∫dεetγ al.’εγ showingφγ) → the~3-6↓dashed‘IC40
flux prediction
for the 40-(Hummer et al. 12, He+ KM 12)
Figure 3 | Compatibility of some neutrino
string portion of the analysis, and the black dashed line labelled ‘IC40159
ray production in GRBs with observations
3.
details(multi-π,
ν mixingetc.)→ dataset.
ex., multi-π
Guettaet al.’ showing
the prediction
for the full
two-year
The cosmic~2-3 ↑ (KM & Nagataki 06)(‘IC40159 Allowed 90% CL’) shows the 90%
4,20
is
also
shown
for
reference
as
the
pale
ray
normalized
Waxman-Bahcall
flux※ totally different from “astrophysical” model-uncertainty
calculating
neutrinoin
flux(vertical axes, asfinpγ	

Fig. 1) versu
grey dashed line. 90% confidence upper limits on these spectra are shown ascomparison to model predictions with estim(ex. Asano, KM+, Baerwald+)solidtheselines, withthe grey line labelled‘IC40
limit’ showing
the previous
IceCube※problems
do
not
exist
in
many
earlier
calculations
solid line labelled ‘IC50159 Allowed 95% C
6result and the black ‘IC401IC59 Combined’ line showing the result from theImplications of IceCube “Stacking” Searches

The Astrophysical Journal, 752:29 (10pp), 2012 June 10~ 6-10E2 φν(ν)[GeV cm-2s-1sr-1]

E2 φν(ν)[GeV cm-2s-1sr-1]
E2 φν(ν)[GeV cm-2]

10

10-8

The IceCube Collaboration
Modified Guetta et al. (2004)
Modified analytic result
Numerical result
Spectra for indivadual GRB

The IceCube Collaboration
Modified Guetta et al. 2004
Modified analytic result
Numerical result

10-8
10-3

He et al.

He et al.

-910-1010-4

10-11

10-9

R=1012cm
R=1013cm
R=1014cm
R=1015cm
R=1016cm

10-10

10-11
10-5

10-12
3

10

10 10

4

5

6

7

6

10 7

8

10-12
104

10 10
10
10
105
106
107
108
109
1010
10
Eν [GeV]Eν [GeV]Eν [GeV]Figure 1. Neutrino spectrum for a typical GRB, using the method adopted
Figure 3. Spectra of the total neutrino emission produced by 215 GRBs,
Figure 2. Neutrino spectra numerically calculated by adopting the internal shock He+
KM 12 ApJ (see also Hummer et al. 12 PRL)
by the ICC2 (Abbasi
et al. 2010, 2011a; ICC 2011) (dark gray solid line),obassuming the same dissipation radius for every GRB at R = 1012 cm (theadius R = 2Γ ctv /(1 + z) for 215 GRBs (light red lines) observed during
the modified Guetta et al. (2004) method (blue solid line), our modified
black solid line), R = 1013 cm (the blue solid line), R = 1014 cm (the green
he IceCube
in the 40-string
and 59-string
configurations.
We (reduse theanalyticaloperations
method (purple
solid line),and our numericalmethodsolid
solid line), R = 1015 cm (the yellow solid line), and R = 1016 cm (the redameline).
GRBThesamples,the same
assumptions
for theparameters,
parameters
used inthe calculation
for GRB
this GRB
are α = and1, βthe= 2,solid line). The corresponding upper limits are shown by the dashed lines.
amefluenceeffectiveas −5
a function
the10zenith
angle
as those
bypeakthe ICC.
Fγobarea= 10
erg cm−2of(inkeV to1 MeV),z =used2.15,
energyOther parameters are the same as those used in Figure 2. Note that the red,
The thickred solid line represents the sum of the52neutrino
spectra of the 215
ob−1 , bulk Lorentz factor
=
200
keV,
peak
luminosity
L
=
10
erg
s
"
green,and yellow dashed lines overlap with each other because the spectrumγγ,b
GRBs and the thick red dashed line is the corresponding 90% CL upper limit
2.5
ob
shape
of
the red, green, and yellow solid lines is similar in the energy range ofΓ = 10 The, theobservedvariability
timescale
tv =line
0.01
andpredicted
the baryon
of IceCube.
thickdark graysolid line
and dashedares, the5 GeV–3 × 106 GeV.
10
ηp = spectrum
10.
otalratio
neutrino
and the corresponding 90% CL upper limit given by(A color version of this figure is available in the online journal.)
he ICCfor thecombinedof IC40
IC59,
respectively. The(A color
versionof this data
figureanalysis
is available
in theandonlinejournal.)5+ Not ruled out yet+ ~10 yr observations by IceCube can cover most of relevant
parameter space for the GRB-UHECRp hypothesis

Optimistic Cases: Neutron Escape Model

Both neutrons and neutrinos should be produced
escaping UHE neutrons → UHE protons via neutron decay
n emission
A’) 2
2
-8
-2 -1
-1
εν2Φ(εν) ~ ε(modeln Φ(εn) ~ εCR Φ(εCR) ~ a fewx10 GeV cm s sr sr-1
E 2 J [GeV cm−2 s−1 sr−1 ]10−6

SFR evolution

cosmogenic

Γi = 103 , 10−3 s < tv < 0.1 s

tdyn < tsyn

10−7IC-40 (HE, prelim.)

IC-40 (EHE, prelim.)

10−8
IC-86 (EHE, 3yr)

10−9

Ahlers+ 11 APh
103

104

105

106

107

108

E [GeV]109

1010 1011

Excludedby IceCube

Fall of Classical GRB Picture
Wolf-Rayet star
R~1011-1012 cm

External shockr~1016-1017 cm

Problems!
- spectrum- empirical relations- rad. efficiency“Classical” internal shockr~1013-1015.5 cm
Photosphere(τT=nσT(r/Γ)=1)
r~1011-1013 cm

talk by Daigne

modified-thermal emission
dissipation: shock/mag./n-p collision
talks by Pe’er, Beloborodov, RydeMag. dissipation
ex. r~1015-1016 cm(model-dependent)
talk by Zhang

22

Fe: maximum energylog(Emax [eV])21

p: maximum energy

20
19
18

Fe survival	

p depleted	

17
4 12

12.5

13

13.5

3

14 14.5log(r [cm])

15

15.5

16

16.5

log(fA !)

2
1

fAγ=1

0
-1

fAγ: disintegration efficiency-2

internal shock	-3

fpγ: meson production efficiency

-4
12

12.5

13

13.5

photospheric	

14 14.5log(r [cm])

15

15.5

16

16.5

mag. dissipation	

Lγb = 1051.5 erg/s
Γ=300, Ue=UB

sults are shown in Fig. 8. In fact, the above analytic estimations agree with numerical results. For example, let us
consider parameter sets demonstrated in Fig. 1 for HL
GRBs and Fig. 3 for LL GRBs. For the former set with
53 ergs and $the source redshift z ¼ 0:1 (Eiso
acc ¼! ¼ 1022
iso20), we have E% &% ( ð1=4Þfp! Ep ðdNp =dEp Þ=ð4'D2 Þ (3 " 10#4 erg cm#2 , which agrees with the thick solidline shown in Fig. 8. For the latter set with the source
50 ergs and $redshift z ¼ 0:005 (Eisoacc ¼ 10),! ¼ 102
2
iso
we have E% &% ( ð1=4Þfp! Ep ðdNp =dEp Þ=ð4'D2 Þ ( 7 "10#7 erg cm#2 , which also agrees with the thin dashedline shown in Fig. 8. Note that such low redshift bursts

Model-Dependent Predictions
Dissipative photosphere Large r models- GeV-TeV due to pp- (UHE)CRs depleted

0

pγ	

-4
-5

KM+ 08 PRD

z=0.1

pp,pn

-6

2

log(E!2 "! [erg cm-2])

KM 08 PRDR

pp (#T=1)
p$ (#T=1)
pp (#T=10)
p$ (#T=10)

log(Eν φν [erg cm-2])-2-3- PeV-EeV (undetectable)- UHE “nuclei” possible

-7
-8
-9
-10

-2

r=1014 cm

-4
-6
-8

ECR=Eγ	

3

4

-10

5

6
7
log(E! [GeV])

8

9

10

see also Wang & Dai 09 ApJL
Gao, Asano & Meszaros 13 JCAPHL GRB (z=0.1)
LL GRB (z=0.005)

ECR=10Eγ	345r=1015 cm
67log(Eν [GeV])

8

9

10

FIG. 8 (color see
online).
neutrinos from one
alsoEnergy
He etfluencesal. 12ofApJ
nearby GRB event. Solid lines and dashed lines show HL GRB
Zhang & Kumar 13 PRLiso
53 ergs at z
¼ 0:1 and LL GRB with E! ¼
with Eiso! ¼ 1050
10 ergs at z ¼ 0:005, respectively. A thick solid line shows

The Role of Neutrons at Subphotospheres: GeV Neutrinos	 Collision w. compound flow (ex. Meszaros & Rees 00)
nucleons(protons+neutrons)

nucleons(protons+neutrons)

Dissipation
ǁ‖Internal shock
Inelastic collision
N+n→π→γ,ν,eCollision w. decoupled neutrons (ex. Bahcall & Meszaros 00, Beloborodov 10)

proton flow

neutron flow
after rdec

Dissipation
ǁ‖
Inelastic collision
N+n→π→γ,ν,e• Quasi-thermal emission explain observed GRB spectra(via EM cascades, Coulomb heating & synchrotron)(see talks by Meszaros, Pe’er, Beloborodov, Ryde)Quasi-thermal Neutrinos are Detectable	 -2εν ~ 0.1 Γ Γrel mp c2
inevitable, CRs not required
If dissipation comes from neutronsεν2 φν ~ εγ2 φγ

Quasithermal-3εν ~ 30-300 GeV

-3.5
-4
-4.5

Atm. ν	

-5
-5.5
-6
0

1

2

1.5

Eγiso=1053.5 erg
Γ=600, z=0.134log(E [GeV])

56• DeepCore is crucial
in the 10-100 GeV range• Stacking ~1000-2000 GRBs(~10 yr w. current satellites)
KM, Kashiyama & Meszaros 13 PRL
see also Bartos, Beloborodov+ 13 PRL

Quasithermal
Quasithermal+PL

17log(N (>E))

log(E2 q [erg cm-2])-2.5

stacking for GRBs
w. >10-6 erg cm-2

0.5
0
-0.5

Atm. ν	

-1
-1.5

1

2

3
4
log(E [GeV])

56

Novel Acceleration Mechanism in Neutron-Loaded Flows	“Neutron-Proton-Converter Acceleration” (Derishev+ 03 PRD)
another Fermi acceleration mechanism without diffusion         




 

  



Points- naturally injected(neutron mean free path
> internal shock length)  - guaranteed for n-loaded flows(weak B is enough)- crucial if shock acc. is inefficientex. radiation-mediated (σnp < σT)
 
 

 

Kashiyama, KM & Meszaros 13 PRL- slow process → TeV νNPC Acceleration: Spectra & Effects

Monte Carlo simulations for test particles• spectra consisting of bumps rather than a power law• >10% of incoming neutron energy can be used for NPC acc.
V I•E W
L E T T E R S the detectability of GeV-TeV neutrinos
enhancing-2Γrel=50.01

2

E dN/dE

0.1

Ncyc = 0=1=2=3log(E2 q [erg cm-2])

1

0.001

0.0001

0

0.5

1

1.5

2
2.5
3
3.5
4
log(E [GeV]) comoving

nucleon spectra w.o. cooling

4.5

Quasithermal
Quasithermal+NPC-3

Atm. ν	

-4

-5

-6

LL GRB w. Γ=30, Γrel=5
w./w.o. 1st NPC bump0

wnstream for !rel ¼ 3 (left) and 5 (right). We set "d;o ¼ !rel , !pn ¼

1

2

3
4
log(E [GeV])

neutrino spectra

5

6

7

Possible Neutrino Production Sites
Meszaros (2001)

Inner jet inside a starr < 1012 cm, B > 106 G
TeV-PeV ν, no γ
Meszaros & Waxman 01 PRL	Razzaque et al. 03 PRL	KM & Ioka 13 PRL	Inner jet (prompt/flare)r ~ 1012-1016 cm B ~ 102-6 G
PeV ν, GeV-TeV γ
Waxman & Bahcall 97 PRL	

Dermer & Atoyan 03 PRL
KM & Nagataki 06 PRL	Afterglow
B ~ 0.1-100 G
EeV ν, GeV-TeV γe.g., Waxman & Bahcall 00 ApJ
Dermer 02 ApJ
KM 07 PRD	r ~ 1014-1017 cm

TeV-PeV Neutrinos as a Probe of Jets inside Stars
Motivations- Jet acceleration & composition (radiation or magnetic)- GRB-SN connection, progenitor: clues to GRBs & jet-driven SNe- Neutrino mixing including matter effects etc.
“Hidden” neutrino sources• Jets before GRB emission“precursor neutrinos”• Choked jets (failed GRBs)“orphan neutrinos”

Meszaros & Waxman 01 PRL
Razzaque, Meszaros & Waxman 04 PRL
Ando & Beacom 05 PRLhigh density → fpγ >> 1
“calorimetric”
CRs damped (no UHECRs)

More Realistic Picture
Two pieces of important physics were overlooked

1. Ballistic jets inside stars ❌
→ collimation shock & collimated jet
2. CR acceleration at collisionless shocks ◯❌
→ inefficient when mediated by radiation

“Radiation Constraints” on Non-thermal Neutrino Production


KM & Ioka 13 PRL



Wolf-Rayet star

UL GRB: ultra-long GRB
T ~ 104 s >> ~ 30 s
→ blue-super giants?
ex. GRB 111209A











blue-super giant 










suppression region(τT>1 at unshocked flow)(but see Zhang, Zhang, KM+ 13)

    • Lower-power is better• Bigger progenitor is better• favoring choked jets
(difficulty of penetration)• inefficient for HL GRBs

Non-Jet Case: TeV-PeV Neutrinos around Shock Breakout	 • Trans-relativistic SNe• Interaction-powered SNe(w. optically-thick wind)	
(w. massive CSM)	
(ex. Waxman+ 07, Nakar & Sari
12)
Kashiyama et al.

MURASE et al.

-3

Total
pγ
pp
ANB

1
log(Eν2 φν [GeV cm-2])-5

TeV-PeV

-6
-7
-8

ay

0

1

2

3

4
5
6
log(Eν [GeV])

Δt=107.8 s0Δt=107 s-1Model A
Model B (RS)Model B (FS)TeV-PeV

-2
-3
-4
-5
-6

c

se

-9

1d

00

30

2
-2
log(Eν φν [erg cm ])

-4

-10

(ex. Smith & McCray 07, Chevalier & Irwin 12)

7

8

9

12
Figure 2. Energy fluences Kashiyama+of neutrinos from a trans-relativistic
shock breakout
using the same parameters as in Figure 1. We set !CR = 0.2 and DL = 10 Mpc.
Lines represent a contribution from the photomeson production (dashed), theinelastic pp reaction (dotted), and the total (solid). The dotted-dashed lines show
the zenith-angle averaged atmospheric neutrino background (ANB) within acircle of deg for ∆t = 3.0 × 103 s (thick) and ∆t = 1 day (thin).

2

3

4

5
log(Eν [GeV])

6

7

KM+ 11, Katz+ 11

8

FIG. 1 (color online). Energy fluences of muon neutrinos froma SN crashing into dense CSM, where "B ¼ 10!2:5 , &cr ¼ 0:1,
and d ¼ 10 Mpc are assumed. Thick and thin curves represent
Model A and Model B, respectively, (see text). The dotteddashed curves show the zenith-angle-averaged ANB within acircle of radius 1* [39]; we use !t ¼ 107 s for Model A (thick

The signal is detectable for nearby SNe at D < 10 Mpc
stacking analyses & gamma-ray obs. are also relevant

F
c
o
th
d

Origin of PeV Neutrinos
Observed by IceCube?	

Diffuse Neutrino Flux: Now Observed
2 events with PeV energies are found in UHE neutrino search
26 more events are identified by a later analysis

E2 Φν ~ 10-8 GeV cm-2 s-1 sr-1 per flavor
w. break/cutoff at ~2 PeV (for Γ ~ 2)Skymap: No Significant Clusteringcal flux.

see presentation by C. Kopper

IceCube collaboration 13 PRL, Whitehorn 13 IPA※also supported by Laha+ KM 13 PRD

consistentw. isotropic dist.
The two observed events from August 2011 (leftFIG. 4.

Can GRBs Explain IceCube Events?
Unknown origin (diffuse flux mostly comes from distant sources)
pp: star-forming galaxies, galaxy clusters (KM, Ahlers & Lacki 13 PRDR)
Q. Can pγ scenarios such as GRBs and AGN be the origin?
A. Yes (at present), but difficult for high-luminosity (HL) GRBs
∵ IceCube stacking for GRBs: <~ 10-9 GeV cm-2 s-1 sr-1
(ex. IceCube collaboration 12 Nature, Liu & Wang 13 ApJ)

But we may miss a lot of untriggered, dimmer or failed GRBs
• Low-luminosity GRBs (or trans-relativistic SNe)Eγiso~1050 erg , ρ~102-103 Gpc-3 yr-1
• Ultra-long GRBs
Eγiso~1053 erg, ρ~1 Gpc-3 yr-1??
※ Emission mechanisms may be different

Possible Contributions to Diffuse TeV-PeV Neutrino Flux
Low-power jets could explain IceCube events at PeV energies
without violating IceCube limits from GRB stacking(failed) UL GRB (IS)log(Ei2 \i [GeV cm-2 s-1 sr-1])-5

LL GRB (prompt)

Atm ν	

-6
-7

IceCube 2013-8

predictions by
KM+ 06 ApJL

-9
Γ=5

-10

see also
Gupta & Zhang 07 APh

Γ=10

-11
-12
3

KM & Ioka 13456log(E [GeV])

78large uncertainty
but interestingNow HE Neutrinos as a Powerful Messenger
GRB as the UHECR origin? → allowed at present but…
- Optimistic cases were killed (ex. UHEn-escape scenario)- Most parameter space will be covered in ~10 yr if UHEp
- But hard to exclude UHE heavy-nuclei scenario- Afterglow scenario might be possible (→ Askaryan Radio Array)
HE neutrinos from subphotospheres? → more promising- GeV-TeV neutrinos from neutrons (→ DeepCore, PINGU etc.)- Detectable in ~ 10 yr if dissipation comes from neutrons- NPC acc. can enhance detectability of TeV neutrinos- TeV-PeV neutrinos expected for choked low-power jets and peculiar SNe
Origin of sub-PeV neutrinos in IceCube? → possible- Low-power jet populations (ex. LL GRBs) might contribute- Need further studies on such longer-duration transients

Other Possibilities: pp Sceanrios?
pp: intergalactic shocks, star-forming galaxies etc.- viable    

  






New constraints
1. Γ < 2.2
 
2. >30% to DGB










KM, Ahlers & Lacki 13 PRDR















First strong example of ν-γ connection with “measured” ν & γ fluxes

Implications
Question: pp or pγ?
We can test pp scenarios• Γ can be determined in several years
If Γ > 2.2 → pp scenarios are disfavored• Understanding DGB is important
40%-100% from blazars → Γ ~ 2.0-2.1 or disfavored• Individual sources should show γ-ray spectra (→ CTA)
※pγ scenarios are unbounded due to threshold effectmore studies are needed but quite model-dependentNon-thermal vs Quasi-thermal• TeV-PeV non-thermal neutrinos
produced typically via pγ interactions between CRs and photons
Eν ~ 0.01 Γ2 (GeV/εγ) GeV → TeV-PeV ν- Ep-2 is assumed but may not be true
- inefficient at radiation-mediated shocks- complicated spectra due to meson/muon cooling
But diffusive shock acceleration is not always required• GeV-TeV quasi-thermal neutrinos
produced via pn inelastic collisions with thermal “neutrons”
Eν ~ 0.1 Γ Γrel mp c2 → ~30-300 GeV ν- relativistic nucleons via thermalization of neutrons- neutrons are naturally loaded from GRB engine- universal spectra due to irrelevance of meson/muon cooling