Unexplored regions of WIMP
Shigeki Matsumoto (Kavli IPMU)
Collaborators: Members in IPMU WIMP PROJECT
S. M., S. Mukhopadhyay, Y. L. Sming Tsai, [JHEP 1410 (2014) 155]
S. Banerjee, S. M., K. Mukaida, Y. L. Sming Tsai, [JHEP 1611 (2016) 070]
S. M., S. Mukhopadhyay, Y. L. Sming Tsai, [PRD94 (2016) 065034 ]Purpose of these studies is
to figure out regions of thermal WIMP which are not exploredefficiently so far, by analyzing all WIMP-related data.

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WIMP hypothesis
WIMP hypothesis
Dark matter is an electromagnetically neutral and stable particle, whoseabundance at the present universe is from the freeze-out mechanism.

Solving the Boltzmann equation gives
the following behavior of nWIMP/s →Boltzmann eq. tells

WTH h2 ～ 0.1 (1pb/<sv>)
WOB h2 ～ 0.12 ± 0.0015
Freeze-out (reaction vs. expansion)often plays an important role in U.
Particle Physicists: The mass of WIMP may have the same origin of the EWSB!
Experimenters: WIMP must have some interactions with SM particles, sothat there exists a lot of opportunities to detect WIMP!
Which SM particle(s) does the WIMP interact with?

Studying WIMP without prejudice
Which interaction exists
between WIMP and SM?

=? GeV/c20?

DM2/10Interaction

WIMP

Discussing WIMP candidates w/o relying
on any specific new physics models!
↓Classifying WIMPs based on its quantum
number is more useful for our purpose.
Weak charge plays an important role!!!

WIMPs can be classified into the following three categories.
 WIMP has a weak charge of (almost) zero. … Singlet(-like) WIMP WIMP has a weak charge close of (half) integer. … EWIMP
 WIMP has a mixed weak charge due to EWSB. … Well-tempered WIMP↓Let us discuss each WIMP using the simplest example to see what kindof strategy is (expected to be) taken to detect it at present (future)!

WIMP searches

3/10@ Colliders
WIMP is expected to be directly produced
at colliders, if its energy is high enough.
Hadron Collider： Interaction with quarks.
Lepton Collider： Interaction with leptons.
@ Direct detection
WIMP can be detected by observing releaseenergy by the scattering off a nucleus.
SI scattering： Int. with quarks & Higgs.
SD scattering： Int. with quarks & Z boson.
@ Indirect detection
WIMP could be searched for by observing
annihilation products produced at DM halo.
Gamma ray： Int. with all the SM particles
Cosmic ray： Int. with all the SM particles

Well-tempered WIMP

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

The simplest example = Fermionic singlet-doublet WIMP model.
Such a WIMP is predicted by some natural SUSY scenarios.

Minimal contents are 10, 2½, 2–½ due to anomaly cancelation.
↓3 neutral Majorana and 1 charged Dirac fermion introduced.
Lagrangian assuming Z2 symmetry making the WIMP stable isParameter space are defined by [MS, MD, y1 = ycosq, y2 = ysin q].
[DM interactions are assumed to preserve the CP symmetry.]↓Scanning parameter space by Likelihood analysis to clarify
the current status & future prospects, assuming |yi | ≦ 1.

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Well-tempered WIMP
@ Present@ Near future

After LZ/PICO250

Direct detection is very powerful to explore the well-tempered WIMP!

Well-tempered WIMP ← Yukawa interactions → DM-DM-h(Z) couplings
The same conclusion is obtained for the most of well-tempered WIMPs,
for the origin of the mixing and DM-DM-h(Z) couplings are the same.

What we learn: Just waiting future big direct detection experiments!

EW charged WIMP (EWIMP)The simplest example = Fermionic triplet-like WIMP model.
Such a WIMP is predated by the split-type SUSY (AMSB).

Minimal content is 30 , namely just one representation.

6/10↓1 neutral Majorana and 1 charged Dirac fermion introduced.
Lagrangian assuming Z2 symmetry making the WIMP stable isParameter space is simply defined by only one parameter MT.
↓Scanning parameter space is simple because of one parameter.
[Small mixing effect can be introduced, but it’s less significant.]

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Favored@ Present@ Near future

FavoredLHC

EW charged WIMP (EWIMP)The WIMP seems difficult to be detected at DD searches in near future.
LHC will explore the WIMP mass region below 500GeV.
IDD searches are promising, for the WIMP’s annihilation is enhanced!!!
[The enhancement is from Sommerfeld effect. (Hisano, S.M., Nojiri, 2014.)]g-ray obs. (Fermi. CTA) → IDD (g from dSphs) ← DM dist. (PSC, PFS)Singlet-like WIMP

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

Such a WIMP is predated in many BSM scenarios of EWSB, etc.
However, it cannot interact with SM particles, if it is a fermionSome additional new particle（s） must be introduced connecting
WIMP and SM particle. It is called the mediator (portal scenario).
Phenomenology of the WIMP depends strongly on the mediator.

When the mediator is heavier enough than the WIMP and the EWscale, the phenomenology is effectively described by the EFT,

where L represents the typical mass scale of the mediator.
Some simplified models reproducing the EFT are also utilized.
Parameter space is very complicated, ∃around 10 parameters.
↓Scanning parameter space using MCMC, assuming CP invarianceand the flavor blindness of the WIMP interaction with |c i | ≦ 1.

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Singlet-like WIMP
@ Present

Light mediator region

After
LZ/PICO250@ Near futureLight mediator region

Direct detection is powerful to explore the H- & Z-resonance regions.
The four Fermi interactions governs the other region with L < 10mDM,[This region is not so much searched for at DD and LHC exps in near future!]
LHC results → The four Fermi region ← DD (LZ, PICO250) results↓
Leptophilic WIMP!
[It is governed mainly by the interactions with leptons.]

Summary

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 We discussed (fermionic) WIMPs w/o relying on specific BSMs.

 Well-tempered WIMP:
Direct detection searches are (and will be) playing a very
important role to explore the WIMP. What we should do isto wait for their results in the near future.
 Electroweakly charged WIMP (EWIMP):It seems to be the most motivated WIMP from the particle
physics viewpoint. Indirect detection searches will be theonly way to explore the WIMP in near future, requiring aprecision determination of WIMP distribution near by us.
 Singlet-like WIMP with heavy Mediator:
Because of LHC and direct detection searches, leptophilic
region will remain unexplored. Experiments sensitive toWIMP-lepton interactions will be very welcome.
 Singlet-like WIMP with light Mediator:
Studies are now on-going by many DM people in the world,
via simplified models. Among those, interesting regions are
now being reported; Light WIMP in a dark sector, etc.

Studying WIMP without prejudice

App 1

Is there a framework to study WIMP w/o relying on any specific BSM?
After fixing its spin, the WIMP field is written by a linear combinationof colorless rep. of SU(2)L×U(1)Y involving a EM neutral component:

Singlet-like Patche.g.
Bino-like in SUSYKK photon in UED

Higgsino-like in SUSY
Inert Higgs in 2HDM

4½,3

S-D Mixed Patche.g.
Bino-Higgsino WIMP

27…

D-T mixed Patche.g.
Higgsino-wino WIMP

Doublet-like Patche.g.

10Triplet-like Patche.g.
Wino-like in SUSY
Quintet-like Patche.g.
Minimal dark matter

App 2Singlet-Doublet mixed WIMP
SMSM

WIMP
Or
WIMP

SMZ

WIMP

SM

D
Coannihilation region

hResonance regions

WIMP⊂Degenerate
SMγ, ZDSM

WIMP
hH-blind spot region

WIMP

Present status(The likelihood function is now projected onto the (MDM, MD)-plane.)App 3

WIMP hypothesis
Particle dark matter

GeV
10 20

10 –28WIMP hypothesisDark matter is a electromagnetically neutral and stable particle with themass of roughly 100GeV, and it has a usual coupling to SM particles.

WIMP dark matter
GeV
10 5

10 –3

Well-motivated region!
(close to EWSB scale)WIMP in the S-D mixed patch

App 4

Minimal contents: 10, 2½, 2–½ (Anomaly cancel.)Patch coverage: |zS|2 < 0.95 & |zD|2 < 0.95
✔ Effective lagrangian for the contents is(Z2 symmetry is assumed to make WIMP stable.)✔ Model parameters are(3 neutral Majorana + 1 charged Dirac)

MS : Singlet mass parameter (Corresponding to M1in MSSM)
MD : Doublet mass parameter (〃to min 〃 )y1=ycosq : U-type Yukawa coupling (〃to ycosb in 〃 )y2 =ysin q : D-type Yukawa coupling (〃to ysin b in 〃 )with y being y = g’/2½✔ Model parameter space is

CP invariance is assumed. y ≦ 1 is also assumed in our analysis!

Present status in the S-D mixed patch

App 4

Present status(The likelihood function is now projected onto the (MDM, MD)-plane.)Resonance regions

Coannihilation region

Present status in the S-D mixed patch

App 4

H-blind spot region

Present status(The likelihood function is now projected onto the (MDM, MD)-plane.)Future prospects in the S-D mixed patch

App 4

Present status(The likelihood function is now projected onto the (MDM, MD)-plane.)Future prospects in the S-D mixed patch

App 4

After XENON1T(The likelihood function is now projected onto the (MDM, MD)-plane.)Future prospects in the S-D mixed patch

App 4

After LZ/PICO250(The likelihood function is now projected onto the (MDM, MD)-plane.)Future prospects in the S-D mixed patch

App 4

Only coannihilation regions survives after O(1)ton level experiments.
Indirect DM detections will be very important for RS << 1 region.
Future e+e– colliders will be very important for RS ～ 1 region.
Direct detection are very powerful to study mixed WIMPs in general!

WIMP in the Triplet -like patch

App 5

Minimal content: 30 (1 Majorana + 1 Dirac)
Patch coverage: 1 – O(v2/L2) < |zT|2 ≦ 1(Small mixing effects from high-dim operators.)✔ Effective lagrangian for the content is(Z2 symmetry is assumed to make WIMP stable.)✔ There is only one model parameter MT.
Relic abundance limit  MT ～ 3TeV
[Hisano, Matsumoto, Nagai, Saito, Senami, 2007]

Direct detection  sSI ～ 10–11pb[LUX; Hisano, Ishiwata, Nagata, 2015]

Collider (LHC) limit  MT > 270GeV[ATLAS; CMS; Ibe, Matsumoto and Sato, 2013]

Indirect detection  MT > 410GeV
Wino annihilation is highly boosted!
[Hisano, Matsumoto, Nojiri, Saito, 2004]

Using g-ray from dSphs in future!

WIMP in the Singlet-like patch

App 6

Minimal content: 10 (One Majorana fermion)Singlet WIMP cannot interact with SM particlesby alone because of the Z2 symmetry making theWIMP stable, so that some other new particle（s）
must be introduced. Assuming those are heavy
enough, we introduce higher dim. operators.
Patch coverage: 1 – O(v2/L2) < |zS|2 ≦ 1
Small mixing effects are automatically involved
because of the higher-dimensional operators.

✔ Effective lagrangian for the content is✔ Many model parameters, so that we impose simplifying assumptions:

・ Common suppression scale (Li = L) with L > [3 mDM, 300 GeV].
・ All coupling constants ci are smaller than one.
・ Flavor blindness ([cf]ij = cf) and CP invariance (cP = 0).

App 6WIMP in the Singlet-like patch

The EFT description is of limited applicability to discuss WIMP signals
at energetic colliders, so that we consider a general simplified model
which reproduces the EFT at large intermediate particle mass limits.

Using these simplified models to take collider constraints into account!

Hc

H

Hc

H+

Hc

Vector Vf+
cc+
Hccf

HVector VH+fc

Hfc

H+
fcFermion yH

Scalar fP+cHScaler ff
Vector VfcFermion yS

Scalar fSccc

HFermion yPc

HPresent status in the Singlet-like patch

App 6

Present status(The likelihood function is now projected onto the (MDM, Λ)-plane.)H resonance regions

4-Fermi region

Z resonance regions

H resonance regions

Z resonance regions

Present status in the Singlet-like patch

App 6

4-Fermi region

Present status(The likelihood function is now projected onto the (MDM, Λ)-plane.)Future prospects in the Singlet-like patch

App 6

Present status(The likelihood function is now projected onto the (MDM, Λ)-plane.)Future prospects in the Singlet-like patch

App 6After XENON1T(The likelihood function is now projected onto the (MDM, Λ)-plane.)Future prospects in the Singlet-like patch

App 6After LZ/PICO250(The likelihood function is now projected onto the (MDM, Λ)-plane.)Future prospects in the Singlet-like patch

App 6

O(10)ton level direct detection cover the H resonance region entirely.
The Z resonance region will be widely covered by SD direct detections.
The 4-Fermi region has already been restricted to be below Λ<10mDM.
Remaining parameter region is composed mainly of Leptophilic WIMP!