Neutron star as target of Dark Matter

Motoko Fujiwara (Technical University of Munich)Collaboration w/

Koichi Hamaguchi (U. Tokyo)
Natsumi Nagata (U. Tokyo)
Jiaming Zheng (Shanghai Jiao Tong U.)
Maura E. Ramirez-Quezada (U. Tokyo)

Based onPhys. Rev. D 106 (2022) 5 [2204.02238] + on-going work

53rd Summer school on Astronomy & Astrophysics @Hongo, Tokyo August 3rd, 2023

[C. Kovaris (2008)][M. Baryakhtar et al. (2017)] …

Neutron Star as target of Dark Matter (1/2)
Dark Matter (DM)

Energy injection

Neutron star

ThermalizationWeakly interacting massive particle

Surface Temperature (Ts)eg. James Webb Space TelescopevDM ≃ 0.5 × c

10 km
4bmax ≃ 10 km

Erecoil ≃ 1 GeVdN=dt

areavelocity # density

ρloc6222 −1⋅ πbmax ⋅ vloc ⋅≃ 10 s
πmDMvloc ≃ 230 km/s
ρloc ≃ 0.3 GeV/cm3

Ts ≃ 2000 K

WIMP dark matter heating in[C. Kovaris (2008)][M. Baryakhtar et al. (2017)] …

Neutron Star as target of
Dark Matter (2/2)
この効果を古い中性子星で観測できるかもしれDM

Neutron star

Temperature Obs.

cardndSta

Ts ≃ 2000 K w/ DMlingoow/ DM

Plot by N. Nagata••••

Neutron Star can be a good target to search for DM

標準冷却理論において t > 107 年で温度は非常

Gravitational capture of DM → Kinetic energy injection/Annihilation→ Anomalous heating source
暗黒物質加熱効果を考慮すると，十分時間が∞3−452 JWSとなる。
T→∼2×10Kscm )Universal prediction: Ts ≃ 2000 K for wide DM parameters (1 GeV − 1 PeV, σχn ≳ 10If we observe neutron star w/ Ts ≲ 2000 K, we may constrain DM-nucleon cross sectionNScapture,Inelastic(CC)Directdetection,Elastic(SI)NS window
XENONnT

Neutron Star obs. vs Direct detection

Table 1: Reference values of the DM-nucleon scattering cross sections and mass splitting
thresholds that determine the detectability
the TeV-scale DM in DM direct4 detection
NS ofwindow
summary_export
experiments
NS observation.
※ N = n, p
NS andcapture,
Elastic (SD)SD < thSensitivity as targetY•••≃ 300 MeV

Inelastic[N. F. Bell, G. Busoni, S. Robles (2018)][MF, K. Hamaguchi, N. Nagata, J. Zheng (2022)]

DM may be excited0Mq

ΔMEW ≃ α2mW ≃ 𝒪(100) MeVNSIZY���

(c5 = c≃M0 , M± . O(100) keV

SDElastic (SD)NS capture,Large energy injection due to gravitational accelerationeg. Electroweak multiplet DM

n=3, Y=n=2, Y=1/2
�− 12Inelastic DM scattering0(c5 = c5 = 1, cs = 1, cs = 0){(� �� ��� �� �)� {��� ��� ��� ��}}(N ),upper≠452SI‡ƒ
10cm
NS capture, Inelastic
NS window
SI (CC)(N )PandaXXENONnTElastic‡th ƒ 10≠45 cm2(N ),upper(SI) ≠40floor
Direct detection,ElasticSD‡SDƒ 10cm2 ≫2πRNSmn−452σth ≡≃ 2.5 × 10cm
MNS

2GMNSΔMNS ≃ mn 1 −RNS )((d) n =(c)n=2,Y=1/2,m=1TeVDMDirect detection
NS observation

0NS window

Y =0

M0 , M± . O(100) MeV
SD <th(c) n = 2, Y = 1/2, mDM =1 TeV

n=2, Y=1/2

4.1.1

Elastic
scattering
NS capture,
Inelastic (CC){(�� ��� ���� ��� �)� {��� ��� ��� ��}}PandaX

Direct detection, Elastic (SI)

PandaX4(c5 = c5 = 1, cs = 1, cs = 0)

4.1{(�� ��� ���� ��� ��XENONnTKinematically forbidden floor

summary_export

NS win(d) n =n=3, Y=(c5 ={(�� ��� ���� ��� ��PandaX

We first consider the DM-nucleon elastic scattering process for the Y = 0 case. Let us
begin with the SI scattering. The SI scattering cross section of Majorana fermion DMwith a nucleon N is given byNS win

00

NS capture, Inelastic(NC)Elastic (SD)
4(N)‡SI =A

B2
KinematicallyNSm
mN forbidden
DMwindow
2

ﬁ mDM + mN

fN ,NS< windowSDthNS w(36)where mN is the nucleon mass and fN is the effective DM-nucleon SI coupling. There are
two kinds of processes that contribute to this effective coupling. First, the dimension-five7:
The
current
constraints
andfutureof theDMDirect
detection& NeutronStar
operatorFigure(15)
inducesthe DM-nucleon
scattering
viaobservation
theHiggs-boson
exchange, withKinematicallyforbidden prospects
NScapture,
Inelastic(CC)
N effective ments,
coupling
by [136]
aswellas the potential
NS temperature
obser
will begiven
a complimentaryprobe reachfor EWofMultiplet
DMÿshown in terms
ofc5 mthe
cut-off
N(5)(N ) scale 2 for(N ) (a) n = 3, Y = 0,fN =fT + 3 ◊ fT,(37)227c = c = 1; (b) n2 =m5,= 14 TeV with c = ch Y = 0, and mCqG

D

WIMP dark matter heating in
この効果を古い中性子星で観測できるかもしれ
Possible “Contamination”?
Old but Still Warm•• T ≃ 10 − 10 K•

We “assume” there is no late time heating source
Recently, old but warm stars has been observed
w/ s46???

Serious contamination for DM search happens
if neutron stars are dominated by the following heating:w/ DMardnde.g. Vortex Creep Heating

Sta□ Internal heating□ Universal eﬀects□ Quantitative relevance against DM heating

Plot by N. Nagata[Alpar, Pines, Anderson, Shaham (1984)][Shibazaki, Lamb (1989)][Gonzalez, Reisenegger (2010)]

標準冷却理論において t > 107 年で温度は非Can we really probe DM heating eﬀects? Stay tuned for our future collaboration!

暗黒物質加熱効果を考慮すると，十分時間が[MF, K. Hamaguchi, N. Natsumi, M. E. Rarmirez-Quezada (on-going)]∞3••••••

Today’sTalkSummary
We only know few facts about DM (even if we focus on particle dark matter candidates)
In particle physics approach, our final goal is “Identification of DM”(e.g. Determining DM mass, spin, interactions, …)Experimental/Observational/Astrophysical inputs are indispensable to study/probe DM
If DM has interaction with the SM particles, we may probe DM through(1) Collider (2) Indirect detection (3) Direct detection
New direction to probe DM?
→ Neutron star as target of DM (gravitational capture & semi-relativistic recoil)
What is good observable? Neutron star temperature observation?
→ We need to examine internal heating of neutron star (e.g. vortex creep)Let’s work together & explore particle aspect of dark matter w/ your astro-knowledge!