DARK MATTERDARK MATTER DIRECT DETECTION DIRECT DETECTION

IN IN ELECTRON ACCELERATORSELECTRON ACCELERATORS

J. Hisano (ICRR, Univ. of Tokyo)

This talk is based on collaboration with M.M.Nojiri, M.Nagai, and M.Senami (hep-ph/0504068).

東北大学 21 世紀 COE 「物質階層融合科学の構築」素粒子・天文合同研究会「初期宇宙の解明と新たな自然像」

2005 年 9 月 20 日 ( 火 ) ～ 21 日 ( 水 )  東北大学理学部キャンパス 理学総合棟 ７４５号室

Contents of my talk

• Introduction 　　 DM in universe,

SUSY DM,

conventional DM direct detection

• Dark matter detection in electron accelerator

• Conclusion

I I IntroductionIntroduction

Non-baryonic Cold Dark Matter (CDM)Cold Dark Matter (CDM) in the Universe

• Rotation curve • CMB anisotropy (WMAP)• Structure formation

New stable particle beyond the standard model

Structure formation in CDM modelStructure formation in CDM model • Primordial fluctuation grows by

gravitational instability. CDM assists the efficient formation.

• The N-body simulation is consistent for L>~1Mpc.

• DM spatial distribution inside galaxies Clumpy structure Cuspy in Galactic center• DM velocity distribution Maxellian? Non-thermal component?

Unresolved problems Unresolved problems :

If DM particles can be detected,If DM particles can be detected,the Dark Side in the universe can be the Dark Side in the universe can be probed more directly.probed more directly.

Galaxy

History of galaxy formation

Neutralino DM in the SUSY Standard ModelNeutralino DM in the SUSY Standard Model• Lightest SUSY particle (LSP) is stable due to the R parity • Lighest neutralinoLighest neutralino (Majorana fermion)

• Neutralino is a “good” DM candidate.

1 2

0 0 0 0 01 2B W H H

N B N W N H N H

• Predictable thermal relic abundance We can study the thermal history of the Universe. • Detectablities 1) (Conventional) direct detection on the ground 2) Indirect detection using anomalous cosmic rays

0 0 , , ,p e

0 0N N

Conventional direct detectionConventional direct detection• neutralino-nuclei elastic scattering measurement of phonon, ionization, and/or scintillation typical recoil energy is E<~100KeV.

0 0 0 0

5 5

,eff SI SD

N p n

H f NN f N N

Spin-independent (SI) interaction.Coherent process Heavy atomsMore important in neutralino search

2 .A Spin-dependent interaction.Non-zero spin terget.

73 133, .Ge Xe

• counting rate of SI ( )

0

2

42 2

event( )

100 1 10 cm day kgp

T

AR m m

30.3GeV/cm , 220km/ sDM DMv

• CDMS II. 73Ge Target and the exposure 19.4kg days (52.6 live days) leads

0

43 24 10 ( 60 ).p cm m GeV

• effective Hamitonian (neutralino is Majonara fermion.)

• spin-independent cross section for neutralino

0 0h H

q

•. Neutral Higgs exchange is dominant, but, it is highly model dependent due to neutralino mixing and heavier Higgs mass.

Bino-like LSP SI cross section (cm2) from light Higgs contribution

0 0

• O(10)% hadronic uncertainties come from mass fractions of strange quark and gluon to baryon mass.

/ , 9 /(8 ) /Ts s N TG s Nf N m ss N m f N GG N m

Experimental status • high target mass (R<1event/day/Kg) and large atomic number target (A~100).• low energy threshold (Q<100KeV)• low background (Neutron and electron recoil) underground, hybrid-type detector, pulse shape analysis…..

Summary of IntroductionSummary of IntroductionDark matter in the universe is established quantitatively. However,

• constituent of the DM• DM spatial and velocity distributions inside galaxy.

are still unresolved problems.

• Collider experiments, LHC(2007~) and GLC (201?~), study properties of the DM particle (such as neutralino), mass and interaction.

• (Conventional) direct DM detection on the ground may probe before LHC starts, and the proposed reaches also cover

(43 44) 2~10 cmp (46 47) 2~10 cmp

What can we do after that (>~2020 -2030) ?

II, Dark matter detection in electron acceleratorII, Dark matter detection in electron accelerator“Fixed” target experiment. Target is neutralino DM in space.

: electron: neutralino (DM)

Electron beam pipedetector

Scattering is induced by s-channel selectron exchange.Selectron on-pole production is possible if we cantune beam energy to

0 0

2 2( ) /(2 )e eE m m m m

Cross section is enhanced assince DM neutralinos are highly NR.

2

2 22

2

2 2( ) ( )e e

e e e

m

s m mm

0/ 1m m

when

selectronexchange

Necessary conditons for experimentNecessary conditons for experiment• Expected # of event

0

12events

73(150)10GeV 100GeV 100 1Km 1year

em jm L

NA

3( 0.3GeV/cm )DM

• Decay width of (right-handed) selectron to Bino-like LSP.12

20MeV10GeV 100GeV

ee

mm

a) small mass difference at most (10~30)GeV, and it must be measured with precision O(10)MeV. b) high current electron beam, such as O(100) A.c) long detector, such as O(100) m.

Merits for experimentMerits for experiment

10MeV10GeV 220km/s

DMe

vms m

We may measure DM velocity distribution under well control.

a) Small mass differencea) Small mass difference

100 400

0

0.2

200 300

0.1One of favored regions by WMAPis .Small mass difference may be expected.

2 2 20e B

m m M

In MSUGRA Bino and right-handed selectron masses are

Bino-stau coannihilation

Mass difference measurement

LC: ~ 50MeV (absolute value from threshold scan) ~ (Mass diff. from end point.)

• DM detection in electron accelerator measurement of daily modulation of event rate if enough statistics (Later we will come back).

• Collider experiments

310 m

b) high current electron beamb) high current electron beam• KEKB(SuperKEKB): positron (3.5 GeV) 1.861A (9.4A) electron (8.0 GeV) 1.275A (4.1A)

beam energy is

lowered at the arc sections

The beam is

accelerated

energy

accelerator

accelerator

decelerator

decelerator

energy

detector

• Synchrotron radiation (SR) at arc sections the beam pipe damage and the beam power loss.→ 　 Energy Recovery Storage RingEnergy Recovery Storage Ring 　　(noticed by Oide-san in KEK.)

(GEV-scale Energy recovery linac (ERL) is still under debate.)

c) Long detectorc) Long detector• Signal: almost monochromatic and transverse electron

/ 1 2 sin( / 2), 1 4 sin( / 2)cosrecoil e

m d mE E

m d m

• Electron scattering with the beam gas low Pt• pion production from photo-nucleon interactions also low Pt, but number may be huge.

• Possible BGs: expected to be highly suppressed by Pt cut.

(Of course, more serious BG studies is needed in the realistic set up)

→ 　 measurement of Pt for recoiled electron is required.

Beam pipe

Tracking chambers with solenoid magnets

Mask for pile up from upper reaches

Cost reduction is needed. Solenoid magnet : ~1M$/m.

TRD (particle ID)

III, what can we measure ?III, what can we measure ???Dark matter local density and velocity distribution

• Spherically-symmetric isothermal distribution (at halo flame)2

2

3/ 2 3

23 32

3( )

2h

h

v

f v d v e d v

( 270km/ s)

h

← 　 Flat rotation curve is well explained.

• Earth motion at halo flame generates DM wind at earth flame from the Constellation Cygnus.

rotation of Earth⇒ daily modulation

We may measure and velocity and direction of the DM wind.

42°DM wind

1 sidereal day = 23h56m4.09s

Daily modulation of the event rateDaily modulation of the event rate

0(Here, 100GeV, 10GeV)m m

DM

2 24

1 4 ( )3 beam wind

e epole

e e e

h eE Ev

En

What else can be measuredWhat else can be measured.

dispersion beam energy deviation

dark matter wind

cross section (microbern) Energy dependence at peak

• modulation phases are reverse in the positive and negative energy deviation.• energy dependence may resolve degeneracy of and DM .h

→ 　 But, total event # should be O(102-3). (under discussing).

Enything else?Enything else?• Spherically-symmetric isothermal distribution is right?

• Sagittarius dwarf tidal stream Sagittarius dwarf satellite galaxy being tidally disrupted. High velocity particle stream (v~300km/s) , whose mass density is (0.3-25)% of the local density.

• spherical velocity dispersion ?• Maxellian ? Or non-thermal components ? N-bodies’ results are contradictory.

(from Newton)

(Freese et al)

IV, ConclusionIV, ConclusionDM physics after LHC and LC experiments (20~30 years latter! ) is discussed. That is, DM direct detection in electron accelerator. Selectron on-pole production is used. In order to realize it,

a) small mass difference at most (10~30)GeVb) high current electron beam, such as O(100) A.c) long detector, such as O(100) m.

Requirements are severe, but, the experiment may be controlled well and, a) DM local density

b) DM velocity distribution

may be measured. They are important for galaxy formation.

Neutralino astronomy will probe the Dark side of the universe.Neutralino astronomy will probe the Dark side of the universe.

Let us hope that the time is Let us hope that the time is more ripe for this realizationmore ripe for this realization..

Back up slide

Neutralino relic densityNeutralino relic density

b s

Stau LSP

02Am m

1, Stau coannihilation region:2, Funnel region: 3, Focus point region: large Higgsino-Bino mixing

01

0( 2 )Am m

0( )m m

0 0 0 01 1 , , ,A tt bb hZ

• Neutralino annihilation freezes out at and neutralino is decoupled from thermal bath.

01/(20 30)T m

• Minimal supergravity (MSUGRA) predicts Bino-like neutralino LSP.

(Ellis et al)

The ratio of the cross sectionsBeam axis is Perpendicular / Parallel to the DM wind