The Surprising Solar Gamma-ray Emission from
Cosmic-Ray Interactions

Kenny, Chun Yu Ng ()Weizmann Institute of Science
11/8/18

Kenny C.Y. NG, ICRR 2018

1

Observations of the Sun
GeV ???

The Sun is not hot enough!

Fundamental Physics
from the Sun

MeV Neutrinos
Neutrino Mass

Helium Discovery

11/8/18

Kenny C.Y. NG, ICRR 20182

Sun – Cosmic-Ray Beam Dump
p + p ! ⇡ 0 /⇡ ± + X
0⇡ !

CR electrons
Inverse-Compton+⇡ ± ! µ± + ⌫µ /¯⌫µµ± ! e± + ⌫¯µ /⌫µ + ⌫e /¯⌫e!

Seckel, Stanev, Gaisser (1991)
Zhou, KCYN, Beacom, Peter[1612.06420]

CR protons
Hadronic
11/8/18!
Kenny C.Y. NG, ICRR 2018"3

Dark Matter/Gravity problem• Big Bang Nucleosynthesis\CMB• Clusters• Galaxies/Local
11/8/18

Kenny C.Y. NG, ICRR 2018

4

Weakly interacting massive particles• Direct Detection• Collider Search• Indirect Detection

11/8/18

Kenny C.Y. NG, ICRR 20185

Ignoring self-interactions [66], the number owhere cap is the capture rate, and Cann
157
particles
N for
in theSun, at a timet, canbe161
counting
the annihilationcross
section158
functionthe capture
and annihilationra162
matter ofnumber
density.
Initially, when
156

"

160

Sun – Dark Matter detector

formed, the capture rate far exceeded the164
nihilation events
dNper unit time, ann2. Eve
159
= cap
N ,
165
capture and annihilation
reachCannequilibriumdt
166
the annihilation rate becomes,
160
where cap is the capture rate, and Cann i11161
counting for the annihilationcross
section
2
167
=
C
N
=
ann
ann
cap .
162
matter number density.2 Initially, 2when163
formed, the capture rate far exceeded the n168
The factor of 1/2 accounts for two dark m164nihilation events per unit time, ann . Even
169
being depleted in each annihilation event.
165
capture and annihilation reach equilibriumχ
rate in equilibrium is independent of thχ χ 166 170thetionannihilation
171
cross section h ratevi, becomes,
and is set by
, whi
163

χχ

cap

A

the scattering cross section
and
the
1
1 local h2=CN=
ann things ann
cap .
sity, among other2 [35, 67]. Observed
2174
nihilation would be a direct probe of the W
168 175The
factorof 1/2 accounts
for two dark cromarate
and therefore,
the spin-dependent
169 176being
each annihilation[13, depleted
32, 68]. Ininaddition,
it may be event.
possiblT
170 177tion
in equilibrium
independentof thetherate
WIMPmass m isthrougha cutoﬀ
in
171 178crosssectionh A vi, andis set by, whicof itsannihilation
products.
Thecapangularregionwherecrossannihilationis concentrated
172 179thescattering
section andthe local ha
Press, Spergel (1985)
embedded
deep things
within [35,the Sun173 180sity,
among other67]. [35].
Observed
Krauss, Freese, Press, Spergel (1985)
Detectinga darksignal ofin thegamm
174 181nihilation
would
be a matterdirect probeW
Silk, Olive, Srednicki (1985)
fore,
only possiblemodels in whichth
175 182rate
andis therefore,
the inspin-dependentcros
proceeds
as show
176 183[13,32, 68].via
In long-lived
addition, mediators,
it may be possible
Kenny C.Y. NG,177
ICRR 2018
the WIMP mass m through a cutoﬀ in6
11/8/18172

167 173!

Solar WIMP Search• Best limit on SD crosssections– Hard Channels• Both scattering andAnnihilation !
• How far can neutrino
telescopes reach?
11/8/18

Kenny C.Y. NG, ICRR 2018

C3F8 Direct Detection
Neutrino floor
Ruppin et al. 20147

Sun – Cosmic-Ray Beam Dump
DM Detector

Seckel, Stanev, Gaisser (1991)
Zhou, KCYN, Beacom, Peter[1612.06420]

CR protons
Hadronic
11/8/18

χχ χ
χχ

"
!
Kenny C.Y. NG, ICRR 2018"8

Solar atmospheric gamma raysZhou, KCYN, Beacom, Peter [1612.06420]

Limb contribution(Theoretical Min)
Theoretical Max from CRγγ

Reality- Solar B-field- Solar Modulation

11/8/18!
Kenny C.Y. NG, ICRR 20189

Solar ATM gamma-ray production
Limb contribution

Boost gamma-ray
production

Theoretical Max from CRγγ
Reality!

Seckel, Stanev, Gaisser (1991)
11/8/18

Kenny C.Y. NG, ICRR 201810

The overall picture 2011
• Model prediction too small• Limb too small• Satisfy cosmic-ray bound à CR model with large B-fieldenhancement(1104.2093)

Limb: about 10^-3 of the CR
upper bound

11/8/18

Kenny C.Y. NG, ICRR 201811

Solar gamma analysis• Fermi data (e.g., 6 years, 10-100 GeV)

FIG. 1. Left: Stacked photon counts map of the Sun ROI in 10–100 GeV. Right: Same, but for a fake-Sun ROI (in th
example, trailing the Sun in its path by +180 days),which
is usedto measure the di↵use background. The exposures 12
of t
Kenny
C.Y. NG,ICRR 2018
11/8/18
two ROIs di↵er by . 2%. (Maps for > 0.1 GeV are shown in Fermi2011.) Visually, the solar-disk component (comparable

Observation: 9-year averaged spectrum
Tang + 1804.06846
PRD 98 no.6, 063019• 2008 - 2017

SSG Model
Extended

11/8/18

Kenny C.Y. NG, ICRR 201813

CR Solar Modulation / solar activity

11/8/18

Kenny C.Y. NG, ICRR 201814

Please use the Explanatory Notes when completing this form

CR Solar Modulation / solar activity

Step 1: Diffusion
CR

2: Coronal Fields

3: Photosphericflux tubes

γ

NASA

Fig. 2 The 3 steps of how cosmic rays are affected by the Sun. The 1st i
propagation from interstellar space to the Sun (solar modulation). The 2nd
propagation affected by the coronal magnetic fields. The 3rd is cosmic-ray p
magnetic flux tubes in the photosphere, where interactions occur. The 4th pexample of charged particles entering a flux tube (along the z-axis at r=0). D
the incident angle, cosmic-ray can be reflected.
These trajectories aimportant for producing gamma rays that can escape the Sun and be detecta
Compared to the previous calculation [3], which used a simple part
Adriani+ 2013
treatment and an unrealistic particle motion model in the photosphere (theKenny C.Y. NG, ICRR
201815
11/8/18
not modeled), my proposed calculation
significantly
improves in every aspec

Time variation

Tang + 1804.06846
PRD 98 no.6, 063019• Clear anticorrelation with solar activity from 1-10 GeV• Less clear in 10-100 GeV (less variation or insufficient statistics)

11/8/18

Kenny C.Y. NG, ICRR 201816

Amplitude Problem• 1 GeV gamma <-> 10GeV proton.
• Amplitude observed on Earth too small!
Small
amplitude

Additional modulation towards the Sun/ at
the solar atmosphere!
11/8/18

Kenny C.Y. NG, ICRR 201817

Observation: 9-year averaged spectrum
Tang + 1804.06846
PRD 98 no.6, 063019• 2008 - 2017

SSG Model
Extended

11/8/18

Kenny C.Y. NG, ICRR 201818

High energy photon/Time variation,
Surprise (1)!
•••>100 GeV events
6 events from AUG 2008 to Jan 2010 (quiet Sun)0 events for the next 7.8 years (active Sun)

Linden + 1803.05436
PRL 121 no.13, 131103
2

Morphology.—The large -ray flux suggests that a large fraction of the solar surface participates in the -ray emission process. To further elucidate the -ray generation mechanism(s),we resolve the -ray morphology across the solar surface.
This reconstruction is possible at high (&10 GeV) energies
due to the excellent (⇠0.1 ) Fermi angular resolution.
In Figure 2, we show the observed position of -rays in our
analysis, dividing the data into two temporal bins (before andafter January 1, 2010; corresponding to the end of the solar
minimum), and two energy bins (below and above 50 GeV;
corresponding to the spectral dip discussed in Ref. [17]). Surprisingly, we find that, contrary to the SSG model, the emission is neither isotropic nor time-invariant. Instead, it includes
distinct polar and equatorial components, with separate timeand energy dependences. In particular, it is visually apparent
that -rays above 50 GeV are predominantly emitted near thesolar equatorial plane during solar minimum, but are emitted
from polar regions during the remaining solar cycle.
We utilize two separate methods to quantify the significanceof this morphological shift. The first employs a KolmogorovSmirnov test to differentiate the distribution of -rays in obFIG. 1. (Top) The solar disk -ray spectrum during solar minimum
served helioprojective latitude (|Ty |) during and after solar(before January 1, 2010, blue circles) and after (red squares). Small
minimum. This provides a model independent method ofshiftsalong
the x-axis improvephoton
readability. The
gray lines show are
the veryThehigh-energy
production
sensitive
solar condition
comparingthe data, to
but theloses sensitivity
to convolving facSSG model renormalized by a factor of six to fit the lowest-energy
tors such as the instrumental PSF. Below 50 GeV, we find that
datapoint (solid), and the maximum -ray flux that could be prothe event morphology is consistent to within 1.1 . However,duced by hadronic cosmic rays (dashed). (Bottom) The ratio ofKenny
the C.Y.
NG, ICRR 2018
11/8/18-ray flux observed in periods during and after solar minimum.
above 50 GeV, we reject the hypothesis that the event mor-

19

Sun shadow observations

North

2

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

1
0

South

GSE latitude (deg.)• Perhaps not too surprising actually.
• TeV cosmic-ray sun shadows (near Sun-trajectory)

−1

−2
2

1

East

0

−1

−2

West

GSE longitude (deg.)−6.0 −5.0 −4.0 −3.0 −2.0 −1.00

Dobs (%)

Tibet Asgamma
FIG.
Year-to-year variation of the observed Sun’s shadow between 1996 and 2009. Each panel
PRL1.2013displays a two-dimensional contour map of the observed flux deficit (Dobs ). The map in 2006 is
C.Y. NG, ICRR
11/8/18
omitted because of insuﬃcient statistics Kennyfor drawing
a 2018map.

20

Spectrum, surprise (2)Tang + 1804.06846
PRD 98 no.6, 063019• Hard spectrum till ~100 GeV– Magnetic enhancement works for protons ~ TeV– Enhancement increasingly efficient! Close to upper bound at HE

SSG Model
Extended

11/8/18

Kenny C.Y. NG, ICRR 201821

Spectrum, surprise (3)• Strange “dip” between 30-50 GeV

Tang + 1804.06846
PRD 98 no.6, 063019– Naively, two components, but not easy
– No obvious instrumental explanation– Seems shallower outside solar minimum– Statistical fluke? Time-dependent feature/systematics? Will know soon

SSG Model
Extended

11/8/18

Kenny C.Y. NG, ICRR 201822

Morphology, surprise(4)• Low Energy Bin

Linden + 1803.05436
PRL 121 no.13, 131103– 10-50GeV

11/8/18

Kenny C.Y. NG, ICRR 201823

Morphology, surprise(4)• High Energy BIN

Linden + 1803.05436
PRL 121 no.13, 131103– (> 50 GeV)

11/8/18

Kenny C.Y. NG, ICRR 201824

Morphology, surprise(4)Linden + 1803.05436
PRL 121 no.13, 131103• Two spatial components• Polar– Relatively stable vs time

• Equatorial– Extreme time variation

11/8/18

Kenny C.Y. NG, ICRR 2018

25

HAWC

Hao Zhou TeVPA2018• F

11/8/18

Kenny C.Y. NG, ICRR 201826

Gamma Hadron Separation• F• Large FOV, all weather instrument
11/8/18

Kenny C.Y. NG, ICRR 2018

27

10

10

HAWC analysis
[]

0

5

0

0

[]

5

0

[]

5

0

10

0

• Nov 2014 - December 2017 (829 days)
5

5

10
10

5

0
↵ []

5

5

10
10

10

5

0

• Significance map
18

15

12
9
6
3
significance [ ]03

4.2 TeV

10
10

10

1
2
1 0
significance [ ]32

4.2 TeV518

11/8/185
15

0↵0 [ ]

5129
6
3
significance [ ]

10
0

0

2
4
6
significance [ ]

5

10
8

4.2 TeV

[]

5

0

5

10
10

0
↵0 [ ]

10

0

[]

0

5

Expected (max. CR)

5

0

[]

2

10

5

0

5

Gamma-hadron cut

Sun Shadow (all data)
10

0
↵ []
0

0

5

10
10
3

5

0
↵0 [ ]

2

1
2
1 0
significance [ ]5Kenny C.Y. NG, ICRR 2018

10
3

10
10
2

5

0
↵0 [ ]

02
4
6
significance [ ]

5

10
8

28

First HAWC analysis of the Sun (2014-2017)• Constrain ~10% of CR upper bound (active phase)• Exciting prospect for current solar min (2018 -)1.36 TeV

10

[]

5

0

0

0

[]

5

5

18

5
15

0
↵0 [ ]

5129
6
3
significance [ ]100

HAWC 1808.05620
To PRD
10
10

3

4.2 TeV

10

[]
0

[]
0

0

2

1
2
1 0
significance [ ]

5

10

3

4.2 TeV

0

5

10
10
18

5
15

0
↵0 [ ]

5129
6
3
significance [ ]

10
10

10
0

3

17.2 TeV

1050↵0 [ ]

2

1
2
1 0
significance [ ]

5

10
3

17.2 TeV

10

5

[]

5

0

0

[]

0
↵0 [ ]

5

5

0

5

10

5

5

0

5

10
10
18

Kenny C.Y. NG, ICRR 2018

0

5

10
10

11/8/18

1.36 TeV

10

5
15

0
↵0 [ ]

5129
6
3
significance [ ]

10
0

10
10
3

5

0
↵0 [ ]

2

1
2
1 0
significance [ ]

5

10
3

29

FIG. 2. Left: Observed Sun shadow, described by Eq. (6), at median energies of 1.3
the shadow is 1.3 , 0.9 and 0.7 at the respective energies. Center: Same maps with

Solar Atmospheric Gamma rays

Complicated……

But could be a new probe for solar physics!
11/8/18

Kenny C.Y. NG, ICRR 201830

Solar Atmospheric Neutrinos
KCYN, Beacom, Peter, Rott 2017

• Dilute atmosphere, larger neutrino flux
Seckel+ 1991, Moskalenko+, 1993, Ingelman+ 1996,
Hettlage+ 2000, Fogli+ 2003

11/8/18

Kenny C.Y. NG, ICRR 2018

C.A. Argüelles+ 1703.07798
Joakim Edsjo+ 1704.02892
31

events),or outside and then enter the detector after propbine neutrinos and antineutrinos. The muon energy at
agation(entering
events). For starting events, the muon
birth, Eµ , is related to the neutrino energy, E⌫ , byspectrumEµ = E⌫is(1 y), where y is the inelasticity parameter [48, 49]. For simplicity, we assume a fixed value of
sta0.4 throughout our energy range of interest. We
y =
dN
1
d
NA ⇢Vabsorption
T(E⌫which) (Ebecomes, (1)⌫)
neglect 'neutrino
in Earth,
imEµ
dE
1
y
dE
µ
⌫
E⌫ = theportant only above ⇠ 40 TeV for neutrinos that crossNeutrino point source detection(1y)

diameter (and ⇠ 1 PeV for neutrinos that travel from the
Sun tod IceCube
where/dE⌫ [49]).
is the neutrino flux ,is the interacMuons
canbeproduced
insidethedetector(startingtion cross section [48, 49], NA = 6.02 ⇥ 1023 g 1 is theevents), or outside and then enter the
3 detector after propAvogadro
number,⇢'1g
cm
the density,
agation (entering events). For startingisevents,
the muonV is thefiducial
volumeof the detector, and T is the e↵ective exspectrum
isposure.staThe muon energy is taken to be its birth energy.
dN
1dTo reduce'backgrounds
fromatmosphericmuons,NA ⇢V T(E
, (1) we con⌫ ) (E⌫ )
Eµ
dE
1
y
dE
µ
⌫
E⌫ =exposure for thesider only upgoing events. The e↵ective• Numu_CC events– Starting events(1y)

Sun is thus taken to be half the detector live time.
where d /dE⌫ is the neutrino flux ,is the interacFor
entering
muons,
takingintoaccount
loss,
tion cross section [48, 49], NA = 6.02 ⇥ 1023 g 1 isenergy
thetheAvogadro
spectrumis [46,
number,⇢ '50]
1 g cm 3 is the density, V is thefiducial volume of the detector,
and T is the e↵ective ex1
ent The muon energy isZtaken
posure.
to be dits birth energy.
dN
NA ⇢AT'dE(E⌫ we) (E(2)⌫ muons,⌫) ,To reduce backgrounds from atmospheric
conEµ
dE
⇢
(↵
+
E
)
dE
µ
µ The
⌫
1 e↵ectiveysider only
upgoing events.
exposure
for the– Entering events

Sun is thus Muon
taken torange
be half the detector live time.
whereis themuons,geometric
detector= 2.0 ⇥For A
entering
taking into
accountarea,
energy↵loss,
6 spectrum2 is [46,
1 50]
6
2
1
the
10 TeV cm g , and = 4.2 ⇥ 10 cm g [51, 52].
Z 1when the muon enters the deThe muonenergyis thatdN entNA ⇢ATdtector.dE ' ⇢ (↵ + E ) Eµ dE⌫ dE (E⌫ ) (E⌫ ) , (2)
µ
µ
⌫
1 y

• Muon range limited by energy loss. Starting Events
We consider two idealized experimental setups thateventuallywins (for(Super-K)
Gen2
horizontal events?)roughlyto Super-Kamiokande
andwhere correspond
A is the geometricdetector area, ↵ =
2.0 ⇥

1
2
10 6 TeVThey
cm2 g cover, and the= range
4.2 ⇥ 10of 6acm
g 1 [51,
52].
IceCube.
small,
low-threshold

The muon energy is that when the muon enters thedeKenny C.Y. NG, ICRR 2018tector.

11/8/1832

Background or Signal? (Both!)
Theorist Expectation

BAD energy-resolution
Difficult to distinguish from DM signal
Background!
11/8/18

Kenny C.Y. NG, ICRR 2018

Some energy-resolution
No DM signal*
Astrophysical signal!
33

IceCube Search
Theorist Expectation

Upper

C. Rott, KIAS workshop 2018

Signal
11/8/18

Feldman-Cousins Upper limit at 90% C.L.
- preliminary systematic uncertainties are included by worsening the limit by
Carsten RottSeems difficult……

Kenny C.Y. NG, ICRR 2018

53

KIAS Workshop Oct 29

34

Gamma connection

200 totalStatistics
evts/7 years
Test

theoretically flux prediction
J. Edsjö et al. JCAP 06(2017)033)

C. Rott, KIAS workshop 2018

• Test statistics (TS) is defined as a ratio of likelihood function
From gamma rays: mininumis 1 event/ 1.5
̂ years
TS =event− 2rateln(L(0)/L(μ))
Difficult…….

d

11/8/18= − ( KennyL(μ)
C.Y. NG,|ICRR 20180 ) / (2
2

d2
2

L(μ))

μ̂ > 0μ̂ = 035

Are they (gamma) flares?
• Could have corresponding neutrinos flares– If the emission is associated with certain solar structures(coronal holes, etc)
4Time (UTC)
EnergyR.A.
Dec Solar Distance Event Class PSF Class Edisp Class P6 P7 BG Contribution
2008-11-09 03:47:51 212.8 GeV 224.497 -16.851
0.068
UltraCleanVeto PSF0
EDISP3 X X
0.00050
2008-12-13 03:25:55 139.3 GeV 260.707 -23.243
0.126
UltraCleanVeto PSF2
EDISP1 X X
0.00038
2008-12-13 07:04:07 103.3 GeV 260.346 -23.102
0.399
UltraCleanVeto PSF0
EDISP2 X X
0.00052
2009-03-22 08:43:13 117.2 GeV 1.337 0.703
0.255
UltraCleanVeto PSF1
EDISP3 X X
0.00027
2009-08-15 01:14:17 138.5 GeV 144.416 14.300
0.261
UltraCleanVeto PSF2
EDISP3 X X
0.000212009-11-20 07:55:20 112.6 GeV 235.905 -19.473
0.288
UltraCleanVeto PSF1
EDISP1 X X
0.00020
2008-12-24 05:41:53 226.9 GeV 272.899 -23.343
2009-12-20 08:06:31 467.7 GeV 268.046 -23.177

0.069
0.338

UltraClean
UltraCleanVeto

PSF1
PSF1

EDISP3
EDISP0X X
X X

0.00128
0.00208

TABLE I. Event Information for P8R2 SOURCE V2 events with recorded energies exceeding 100 GeV observed within 0.5 of the solar
center. Checkmarks indicate events that were recorded as photons in previous Pass 6 and Pass 7 analyses, while the Background contribution
indicates the probability that diffuse emission produced the event. Events below the double-line did not pass our default selection criteria, as
they were observed when the Sun was located within 5 of the Galactic plane.

• Will continue monitor the incoming solar minimum
Flux
100 GeV.— In
Figure 1,correlate
we discovered a brightInterpretation.—We
have shown several lines of evidence that•-rayAbove
Perhaps
also
with
HAWC
search.
flux above 100 GeV during solar minimum, but foundreveal two distinct high-energy -ray emission components on
no events in the remaining solar cycle. In Table I, we prothe solar disk. The first emits primarily from the Sun’s polar
Kenny
C.Y.
NG,
ICRR
2018 has a constant amplitude over the solar cycle, andvide
detailed information concerning each >100 GeV event
regions,
36
11/8/18

Solar ATM neutrino – indirect detection Neutrino Floor

Bkg
No B-field effect are considered
IceCube Search ongoing [S. In & C. Rott ICRC17 (965)]
11/8/18

Kenny C.Y. NG, ICRR 2018

KCYN, Beacom, Peter, Rott, 1703.10280
See also
Arguelles+ 1703.07798
Edsjo+ 1704.02892

37

be as strong as ⇠ 10 45 cm 2 , which is more than four orders of magnitude stronger thanent direct-detection experiments for 1 TeV dark matter mass. The cross-section constraints at
er masses are even better, nearly 7 orders of magnitude better than the current direct-detection
traints for 100 TeV dark matter mass. This demonstration of sensitivity encourages detailed
lopment of theoretical models in light of these powerful new constraints.

.

Dark Matter with long-lived mediators
Leane, KCYN, Beacom 1703.04629• INTRODUCTION
Unlockastrophysical observations, including
Gammarays and cosmic
curves, –large
scale structureround (CMB) measurements, point toElectrons,
nce of –non-baryonicdark muon,
matter in etc
theTesting the particle nature of dark mathrough their interactions with baryonicspect of research in physics beyond the(SM).
cross section of weakly interacting masMP) dark
matter can be studied in as– Neutrinos!
onments of high matter density, such as
from the galactic dark matter halo cany trapped by the Sun through scatteringnd settle into thermal equilibrium at theoverdensity of dark matter in the coree annihilation of dark matter into SM
Once equilibrium has been reached,nihilation products only depends on the
d therefore, the scattering cross section! mediators• Unsuppressed

11/8/18109⌫

e ± , µ± , . . .

Batell, Pospelov, Ritz, Shang, 0910.1567
FIG. 1. Illustrationof dark
matter annihilation into longBell, Petraki,
1102.2958
lived mediatorsFeng,
thatSmolinsky,
decay to SM
particles
outside the solar
Tanedo,1602.01465
surface (adapted from Ref. [32]).
Arina, Backovic, Heisig, Lucente, 1703.08087
etc
Kenny C.Y. NG, ICRR 2018

gamma-ray flux that could be probed with ground or38

Mediator Escape and Decay• Viable for a large range of lifetime, actually
a-ray spectra E dN/dE for various final states, per DM annihilation, with mediator m“Highly
boosted”=• 200GeV (dashed),
and m = 20 GeV (dotted). Right: Neutrino spectra.
2

Y

IV.

inos made through pions. In theriable numbers of pions, with difgy going to gamma rays, etc., soance. This is observed in particudiator mass and the 4b final state,c cascade decays being available
mass and consequently softening
ior for gamma-ray spectra is conFor direct decays to gamma rays
energy bound of the box spectra
or mass [62], but this is only sigis not sufficiently boosted. Also
decay to gamma rays, some lower
n be produced from radiated elec11/8/18

HIGH-ENERGY SOLAR GAMMA RAY

this section
we discuss our procedure and result
are allowed byIncurrent
constraints.
long-lived dark mediators using solar gamma rays
The probabilityof HAWC,the signal
surviving to reac
Fermi-LAT,
and LHAASO.
detector, Psurv , provided the decay products escap
Sun, isA.

ProcedureR / c⌧c⌧
PFermi-LAT
e Dthe/ best
. measurem
surv = e analyses provide

of solar gamma rays.
In 2011, Fermi dete
0.1–10 GeV solarrays,measuring an forenergyFigure 3 illustrates
the 2gamma
survival
probabilityva8
1⇠ 10 GeV cm s [38]. Since then, Fermi hasc⌧ . In thislectedwork,
we take c⌧ = R . The proba
more data and improved the data quality.
is relatively updated
insensitivec⌧ ,analyzed
as survival
Fermi todata arein Ref. probabi[39], wherresults
extended⇠
to 2.
100 ForGeV solar
gamma
rays,
changing only
by area factor
gamma
rays,
8
2
energy fluxes of ⇠ 10
GeV cms 1.
production issuring
only
possibleifthemediator
decaysogether, these analyses provide much improved obs
the Sun. Fortional
neutrinos,
however,decay
studies of solar
gamma mediatorrays, which havenotfully exploredin the context
of long-lived
mediators
the Sun provides
a non-zero
flux, butthesignalis a2
5
Kenny C.Y. NG, ICRR 2018higher energy gamma rays (⇠ 10
10 GeV),39HA

ated due to parent-particle and neutrino absorption

Mediator Escape and Decay• Viable for a large range of lifetime, actually• “Highly boosted”• Box spectrum cutoff at low E
More diffuse

Point likeblocked11/8/18

Kenny C.Y. NG, ICRR 201840

Secluded dark matter Gamma Rays

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Kenny C.Y. NG, ICRR 201841

Secluded dark matter Neutrinos• Expected Neutrinos and Muons– No Cooling and Absorption

FIG. 6.
11/8/18

Kenny
Neutrino flux from DM annihilating in the
SunC.Y.
toNG, ICRR
FIG.2018
7.

9

The muon spectrum (entering + starting) for a 42

Dark Matter with long-lived mediators

HAWC 1808.05624
Also Leane, KCYN, Beacom 1703.04629• Optimal mediator life time + capture equilibrium• Complementary to direct detection (SD cross section)SDn 11/8/18
for annihilation into pairs of b̄b, e+ e, ⌧ + ⌧ , and , assuming
Kenny C.Y. NG, ICRR 2018
in less favorable models, which remain to be explored, the limits

Energy info

ind
dir
cau
var
de
lar
atm
im
ab
mu
als
ne
og
key
mu
atm

lon
the
Fe
43

HE Solar Messengers
Gamma Rays

Neutrinos (< TeV)

Neutrinos (> TeV)

Cosmic rays +Solar Atmosphere
WIMP Dark Matter
Dark Matter +Mediators

Maybe electrons/positrons or neutrons can also been seen from space?

11/8/18

Kenny C.Y. NG, ICRR 201844

Summary• Solar gamma rays
– Complicated– TeV– More time (solar minimum starting this year)• Solar atmospheric neutrinos– Not yet detected• Looking for anomalous signal/new physics
Thanks!
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Kenny C.Y. NG, ICRR 201845

Backup slides

11/8/18

Kenny C.Y. NG, ICRR 201846