Searching for dark matter in the mono-Z channel at high ...yzhxxzxy.github.io/slides/1312_DM_monoZ_eecld.pdf · Searching for dark matter in the mono-Z channel at high energy e+e

. . . .DM searches at colliders

. .Mono-Z signature

. . . . . . . .Sensitivity

. .Beam polarization

.Conclusions

. . .Backups

Searching for dark matter in the mono-Zchannel at high energy e+e− colliders

Zhao-Huan YU (余钊焕)Institute of High Energy Physics, CAS

with Xiao-Jun BI, Qi-Shu YAN, and Peng-Fei YIN

Work in progress

December 21, 2013

Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 1 / 21


. .Mono-Z signature



.Conclusions

. . .Backups

Dark matter (DM) searches at colliders.

......

g

g

bχ02

ℓ−

g qχ+

1 νℓ′

g

g

bb

qq′

ℓ+

ℓ−

χ01

χ01

νℓ′

ℓ′+

.

......

q

q

g

χ

χ

q

Social dark matterAccompanied by other new particles

Complicated decay chainsDecay products of other particles

Various final states(jets+ leptons+ /ET, ...)

Maverick dark matterDM particle is the only new particle

reachable at the collision energyDirect production

Mono-X+ /E final states(monojet, mono-γ, mono-W/Z , ...)

(From Rocky Kolb’s talk)Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 2 / 21


. .Mono-Z signature



.Conclusions

. . .Backups

Studies on DM direct productions at collidersBirkedal, Matchev and Perelstein, arXiv:hep-ph/0403004 (monophoton, e+e− colliders).Q. -H. Cao, C. -R. Chen, C. S. Li and H. Zhang, arXiv:0912.4511 (monojet, monophoton, mono-Higgs, hadron colliders).Beltran, Hooper, Kolb, Krusberg and Tait, arXiv:1002.4137 (monojet, hadron colliders).Goodman, Ibe, Rajaraman, Shepherd, Tait and H. -B. Yu, arXiv:1005.1286 (monojet, hadron colliders).Y. Bai, Fox and Harnik, arXiv:1005.3797 (monojet, hadron colliders).Fox, Harnik, Kopp and Y. Tsai, arXiv:1103.0240 (monophoton, e+e− colliders).Kamenik and Zupan, arXiv:1107.0623 (mono-t, hadron colliders).J. Wang, C. S. Li, D. Y. Shao and H. Zhang, arXiv:1107.2048 (monophoton, hadron colliders).Rajaraman, Shepherd, Tait and Wijangco, arXiv:1108.1196 (monojet, hadron colliders).Fox, Harnik, Kopp and Y. Tsai, arXiv:1109.4398 (monojet, monophoton, hadron colliders).K. Cheung, P. -Y. Tseng, Y. -L. S. Tsai and T. -C. Yuan, arXiv:1201.3402 (monojet, hadron colliders).H. An, X. Ji and L. -T. Wang, arXiv:1202.2894 (monojet, hadron colliders).Bartels, Berggren and List, arXiv:1206.6639 (monophoton, e+e− colliders).Y. Bai and Tait, arXiv:1208.4361 [hep-ph] (mono-W , hadron colliders).Bell, Dent, Galea, Jacques, Krauss and Weiler, arXiv:1209.0231 (mono-Z, hadron colliders).F. P. Huang, C. S. Li, J. Wang and D. Y. Shao, arXiv:1210.0195 (monophoton, hadron colliders).Dreiner, Huck, Kramer, Schmeier and Tattersall, arXiv:1211.2254 (monophoton, e+e− colliders).Chae and Perelstein, arXiv:1211.4008 (monophoton, e+e− colliders).Fox and Williams, arXiv:1211.6390 (monojet, hadron colliders).Carpenter, Nelson, Shimmin, Tait and Whiteson, arXiv:1212.3352 (mono-Z , hadron colliders).R. Ding, Y. Liao, J. -Y. Liu and K. Wang, arXiv:1302.4034 (monojet, hadron colliders).T. Lin, E. W. Kolb and L. -T. Wang, arXiv:1303.6638 (mono-bjet, bb/t t + /ET, hadron colliders).Nelson, Carpenter, Cotta, Johnstone and Whiteson, arXiv:1307.5064 [hep-ph] (monophoton, hadron colliders).N. Zhou, Berge, L. Wang, Whiteson and Tait, arXiv:1307.5327 (monojet, hadron colliders).Z. -H. Yu, Q. -S. Yan and P. -F. Yin, arXiv:1307.5740 (monophoton, e+e− colliders).Artoni, T. Lin, Penning, Sciolla and Venturini, arXiv:1307.7834 (mono-bjet, bb/t t + /ET, hadron colliders).H. An, L. -T. Wang and H. Zhang, arXiv:1308.0592 (monojet, j j + /ET, hadron colliders).Petrov and Shepherd, arXiv:1311.1511 (mono-Higgs, hadron colliders).Bell, Y. Cai and Medina, arXiv:1311.6169 ( j j/ℓℓ+ /ET, hadron colliders).Carpenter, DiFranzo, Mulhearn, Shimmin, Tulin and Whiteson, arXiv:1312.2592 (mono-Higgs, hadron colliders).... ... ... ...



. .Mono-Z signature



.Conclusions

. . .Backups

DM direct productions at colliders.

......

q

q

g

χ

χ

q

g

g

q

χ

χ

q

Monojet+ /ET

.

......

t

t

g

g

t

χ

χ

t

t t + /ET

.

......

q

q

q′

χ

χ

W

W

q

q′

χ

χ

W

Mono-W + /ET



. .Mono-Z signature



.Conclusions

. . .Backups

DM direct productions at colliders.

......

q/e

q/e−

q/e+

χ

χ

γ/Z

γ/Z

q/e−

q/e+

χ

χ

γ/Z

Monophoton/mono-Z + /E

.

......

γ/Z/W

γ/Z/W

q

q

q

χ

χ

q

j j + /ET

.

......

h/Z/γ

q/g/e−

q/g/e+

χ

χ

h

Mono-Higgs+ /E



. .Mono-Z signature



.Conclusions

. . .Backups

Mono-Z signature: DM couplings to Z Z/Zγ

.

......

Z/γ

e−

e+

χ

χ

ZAssuming the DM particle χ is a Dirac fermion,we consider the following effective operators:

OF1 =1

Λ31

χχBµνBµν +

1

Λ32

χχW aµνW

aµν

⊃ χχ(GZZZµνZµν + GAZAµνZµν)

OF2 =1

Λ31

χ iγ5χBµν Bµν +

1

Λ32

χ iγ5χW aµνW

aµν

⊃ χ iγ5χ(GZZZµν Zµν + GAZAµν Zµν)

OFH =1

Λ3 χχ(DµH)†DµH → m2Z

2Λ3 χχZµZµ

GZZ ≡ sin2 θW

Λ31

+cos2 θW

Λ32

GAZ ≡ 2sinθW cosθW

�1

Λ32

− 1

Λ31

�

The mono-Z channel at high energy e+e− collider can be sensitive tothe DM coupling to Z Z/Zγ.



. .Mono-Z signature



.Conclusions

. . .Backups

Mono-Z signature: DM couplings to e+e−

.

......

e

e−

e+

Z

χ

χ

e

e−

e+

χ

χ

Z

This channel can also be sensitive to the DM coupling to e+e−.

We consider the following effective operators:

OFP =1

Λ2 χγ5χ eγ5e, OFA =1

Λ2 χγµγ5χ eγµγ5e



. .Mono-Z signature



.Conclusions

. . .Backups

MC simulation

Simulation tools: FeynRules → MadGraph → PYTHIA → PGS

SiD/ILD-like detector:

ECAL energy resolution∆E

E=

17%pE/GeV

⊕ 1%

HCAL energy resolution∆E

E=

30%pE/GeV

Collision energies of future e+e− colliders:ps = 250 GeV: “Higgs factory” (CEPC/TLEP, ILC)ps = 500 GeV: typical ILCps = 1 TeV: upgraded ILC



. .Mono-Z signature



.Conclusions

. . .Backups

Lepton channel: Z → ℓ+ℓ− (ℓ= e,µ)

SM backgrounds: e+e−→ ℓ+ℓ−νν , e+e−→ τ+τ−, e+e−→ τ+τ−νν

Reconstructing the Z boson: require only 2 leptons (e’s or µ’s) withpT > 10 GeV and |η|< 3, and they are opposite sign and same flavor;no any other particle; require the invariant mass of the 2 leptons satisfying|mℓℓ −mZ |< 5 GeV.Reconstructing the recoil mass: mrecoil =

p(pe+ + pe− − pℓ1 − pℓ2)

2;veto events with mrecoil < 140 GeV.



. .Mono-Z signature



.Conclusions

. . .Backups

Lepton channel: Z → ℓ+ℓ− (ℓ= e,µ)D

iffe

ren

tia

l cro

ss s

ectio

n (

fb /

Ge

V)

mll (GeV)

e+e

− collider, √s = 500 GeV, ll + E ⁄

llνν

ττ

ττνν

F1

F2

FH

FP

FA

10-5

10-4

10-3

10-2

10-1

100

101

0 100 200 300 400 500 600

SM backgrounds: e+e−→ ℓ+ℓ−νν , e+e−→ τ+τ−, e+e−→ τ+τ−ννReconstructing the Z boson: require only 2 leptons (e’s or µ’s) withpT > 10 GeV and |η|< 3, and they are opposite sign and same flavor;no any other particle;

require the invariant mass of the 2 leptons satisfying|mℓℓ −mZ |< 5 GeV.Reconstructing the recoil mass: mrecoil =

p(pe+ + pe− − pℓ1 − pℓ2)




. .Mono-Z signature



.Conclusions

. . .Backups


iffe

ren

tia

l cro

ss s

ectio

n (

fb /

Ge

V)

mll (GeV)

e+e


llνν

ττ

ττνν

F1

F2

FH

FP

FA

10-5

10-4

10-3

10-2

10-1

100

101

0 100 200 300 400 500 600

SM backgrounds: e+e−→ ℓ+ℓ−νν , e+e−→ τ+τ−, e+e−→ τ+τ−ννReconstructing the Z boson: require only 2 leptons (e’s or µ’s) withpT > 10 GeV and |η|< 3, and they are opposite sign and same flavor;no any other particle; require the invariant mass of the 2 leptons satisfying|mℓℓ −mZ |< 5 GeV.

Reconstructing the recoil mass: mrecoil =p(pe+ + pe− − pℓ1 − pℓ2)




. .Mono-Z signature



.Conclusions

. . .Backups


iffe

ren

tia

l cro

ss s

ectio

n (

fb /

Ge

V)

mll (GeV)

e+e


llνν

ττ

ττνν

F1

F2

FH

FP

FA

10-5

10-4

10-3

10-2

10-1

100

101

0 100 200 300 400 500 600

Diffe

ren

tia

l cro

ss s

ectio

n (

fb /

Ge

V)

mrecoil (GeV)

e+e


llνν

ττ

ττνν

F1

F2

FH

FP

FA

10-5

10-4

10-3

10-2

10-1

100

0 100 200 300 400 500

SM backgrounds: e+e−→ ℓ+ℓ−νν , e+e−→ τ+τ−, e+e−→ τ+τ−ννReconstructing the Z boson: require only 2 leptons (e’s or µ’s) withpT > 10 GeV and |η|< 3, and they are opposite sign and same flavor;no any other particle; require the invariant mass of the 2 leptons satisfying|mℓℓ −mZ |< 5 GeV.Reconstructing the recoil mass: mrecoil =

p(pe+ + pe− − pℓ1 − pℓ2)

2;

veto events with mrecoil < 140 GeV.



. .Mono-Z signature



.Conclusions

. . .Backups


iffe

ren

tia

l cro

ss s

ectio

n (

fb /

Ge

V)

mll (GeV)

e+e


llνν

ττ

ττνν

F1

F2

FH

FP

FA

10-5

10-4

10-3

10-2

10-1

100

101

0 100 200 300 400 500 600

Diffe

ren

tia

l cro

ss s

ectio

n (

fb /

Ge

V)

mrecoil (GeV)

e+e


llνν

ττ

ττνν

F1

F2

FH

FP

FA

10-5

10-4

10-3

10-2

10-1

100

0 100 200 300 400 500

SM backgrounds: e+e−→ ℓ+ℓ−νν , e+e−→ τ+τ−, e+e−→ τ+τ−ννReconstructing the Z boson: require only 2 leptons (e’s or µ’s) withpT > 10 GeV and |η|< 3, and they are opposite sign and same flavor;no any other particle; require the invariant mass of the 2 leptons satisfying|mℓℓ −mZ |< 5 GeV.Reconstructing the recoil mass: mrecoil =

p(pe+ + pe− − pℓ1 − pℓ2)




. .Mono-Z signature



.Conclusions

. . .Backups

Lepton channel: Z → ℓ+ℓ− (ℓ= e,µ)

Cross sections σ and signal significances S after each cut(ps = 500 GeV, with an integrated luminosity of 100 fb−1)ℓ+ℓ−νν τ+τ− τ+τ−νν OF1 OF2 OFH OFP OFA

σ σ σ σ S σ S σ S σ S σ SCut 1 306 20.4 2.85 2.65 1.46 2.94 1.61 2.47 1.36 3.24 1.78 2.86 1.57Cut 2 235 11.8 1.29 2.52 1.60 2.82 1.78 2.39 1.51 3.19 2.01 2.19 1.38Cut 3 23.9 0.410 0.0495 2.41 4.67 2.70 5.18 2.29 4.44 3.06 5.84 2.09 4.07Cut 4 16.0 0.410 0.0495 2.39 5.51 2.70 6.16 2.19 5.08 3.06 6.92 2.09 4.86Cut 5 12.1 0.410 0.0471 2.19 5.69 2.42 6.24 2.11 5.50 2.95 7.47 2.01 5.25

(σ in fb, S = S/p

S + B)



. .Mono-Z signature



.Conclusions

. . .Backups

Hadron channel: Z → j j

SM backgrounds: e+e−→ j jνν , e+e−→ j jℓν , e+e−→ t t

Reconstructing the Z boson: require only 2 jets with pT > 10 GeV and|η|< 3; no any other particle; require the invariant mass of the 2 jetssatisfying 40 GeV< m j j < 95 GeV.Reconstructing the recoil mass: mrecoil =

p(pe+ + pe− − p j1 − p j2)




. .Mono-Z signature



.Conclusions

. . .Backups

Hadron channel: Z → j jD

iffe

ren

tia

l cro

ss s

ectio

n (

fb /

Ge

V)

mjj (GeV)

e+e

− collider, √s = 500 GeV, jj + E ⁄

jjνν

jjlν

tt

F1

F2

FH

FP

FA

10-4

10-3

10-2

10-1

100

101

0 100 200 300 400 500 600


Reconstructing the Z boson: require only 2 jets with pT > 10 GeV and|η|< 3; no any other particle;

require the invariant mass of the 2 jetssatisfying 40 GeV< m j j < 95 GeV.Reconstructing the recoil mass: mrecoil =

p(pe+ + pe− − p j1 − p j2)




. .Mono-Z signature



.Conclusions

. . .Backups


iffe

ren

tia

l cro

ss s

ectio

n (

fb /

Ge

V)

mjj (GeV)

e+e


jjνν

jjlν

tt

F1

F2

FH

FP

FA

10-4

10-3

10-2

10-1

100

101

0 100 200 300 400 500 600


Reconstructing the Z boson: require only 2 jets with pT > 10 GeV and|η|< 3; no any other particle; require the invariant mass of the 2 jetssatisfying 40 GeV< m j j < 95 GeV.

Reconstructing the recoil mass: mrecoil =p(pe+ + pe− − p j1 − p j2)




. .Mono-Z signature



.Conclusions

. . .Backups


iffe

ren

tia

l cro

ss s

ectio

n (

fb /

Ge

V)

mjj (GeV)

e+e


jjνν

jjlν

tt

F1

F2

FH

FP

FA

10-4

10-3

10-2

10-1

100

101

0 100 200 300 400 500 600

Fra

ctio

n o

f e

ve

nts

mrecoil (GeV)

e+e


jjνν

jjlν

tt

F1

F2

FH

FP

FA

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.080

0.090

0.100

0 100 200 300 400 500



p(pe+ + pe− − p j1 − p j2)

2;

veto events with mrecoil < 200 GeV.



. .Mono-Z signature



.Conclusions

. . .Backups


iffe

ren

tia

l cro

ss s

ectio

n (

fb /

Ge

V)

mjj (GeV)

e+e


jjνν

jjlν

tt

F1

F2

FH

FP

FA

10-4

10-3

10-2

10-1

100

101

0 100 200 300 400 500 600

Fra

ctio

n o

f e

ve

nts

mrecoil (GeV)

e+e


jjνν

jjlν

tt

F1

F2

FH

FP

FA

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.080

0.090

0.100

0 100 200 300 400 500



p(pe+ + pe− − p j1 − p j2)




. .Mono-Z signature



.Conclusions

. . .Backups

Hadron channel: Z → j j

Cross sections σ and signal significances S after each cut(ps = 500 GeV, with an integrated luminosity of 100 fb−1)

j jνν j jℓν t t OF1 OF2 OFH OFP OFA

σ σ σ σ S σ S σ S σ S σ SCut 1 245 131 1.74 18.9 9.47 20.9 10.4 17.8 8.94 22.1 11.1 18.4 9.24Cut 2 207 93.2 1.56 18.0 10.0 20.0 11.2 17.2 9.64 21.8 12.1 13.9 7.84Cut 3 160 56.6 0.270 17.2 11.2 19.2 12.5 16.6 10.8 20.7 13.5 13.3 8.76Cut 4 115 14.9 0.264 16.3 13.4 18.7 15.3 14.6 12.1 20.7 16.9 13.3 11.1Cut 5 92.6 2.91 0.253 15.1 14.3 17.1 16.1 14.1 13.5 20.1 18.7 12.9 12.3

(σ in fb, S = S/p

S + B)



. .Mono-Z signature



.Conclusions

. . .Backups

3σ sensitivity: DM couplings to Z Z/ZγΛ

(G

eV

)

mχ (GeV)

e+e

− collider, Operator F1

√s = 250 GeV

√s = 500 GeV

√s = 1 TeV

ll + E ⁄jj + E ⁄

0

100

200

300

400

500

600

700

800

5 50 500 1 10 100 1000

Λ

(Ge

V)

mχ (GeV)

e+e

− collider, Operator FH

√s =

250 G

eV

√s =

500 G

eV

√s =

1 T

eV

ll + E ⁄jj + E ⁄

0

20

40

60

80

100

120

140

160

180

200

5 50 500 1 10 100 1000

Λ

(Ge

V)

mχ (GeV)

e+e


√s = 250 GeV

√s = 500 GeV

√s = 1 TeV

ll + E ⁄jj + E ⁄

0

100

200

300

400

500

600

700

800

5 50 500 1 10 100 1000

< σ

an

nv >

(c

m3 s

-1)

mχ (GeV)

χχ− → ZZ, Operator F2

√s =

500

GeV

√s = 1 TeV

Fermi upper limit

ll + E ⁄jj + E ⁄

10-29

10-28

10-27

10-26

10-25

10-24

10-23

10-22

10-21

10-20

500 100 1000

(with an integrated luminosity of 1000 fb−1, assuming Λ = Λ1 = Λ2 for OF1 and OF2)Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 13 / 21


. .Mono-Z signature



.Conclusions

. . .Backups

3σ sensitivity affected by the Λ1-Λ2 relation

Λ

(Ge

V)

mχ (GeV)

e+e

− collider, √s = 500 GeV, jj + E ⁄ , Operator F1

Λ = Λ1 = Λ2

Λ = Λ1 = − Λ2

Λ = Λ1, Λ2 → ∞Λ = Λ2, Λ1 → ∞

0

100

200

300

400

500

600

0 50 100 150 200

1000 fb−1

χχZ Z coupling:

GZZ =sin2 θW

Λ31

+cos2 θW

Λ32

χχγZ coupling:

GAZ = 2 sinθW cosθW

�1

Λ32

− 1

Λ31

�

Λ = Λ1 = Λ2: only the χχZ Z coupling contributes.Λ = Λ1 =−Λ2: the χχγZ coupling is dominant.Λ = Λ1, Λ2→∞: the χχγZ coupling is dominant.Λ = Λ2, Λ1→∞: the χχZ Z and the χχγZ couplings are comparable.



. .Mono-Z signature



.Conclusions

. . .Backups

3σ sensitivity: DM couplings to e+e−Λ

(G

eV

)

mχ (GeV)

e+e

− collider, Operator FP

√s = 250 GeV

√s = 500 GeV

√s = 1 TeV

ll + E ⁄jj + E ⁄

0

500

1000

1500

2000

2500

5 50 500 1 10 100 1000

< σ

an

nv >

(c

m3 s

-1)

mχ (GeV)

χχ− → e+e

−, Operator FP

√s = 250 GeV

√s = 500 GeV

√s = 1 TeV

Fermi upper limit

ll + E ⁄jj + E ⁄

10-31

10-30

10-29

10-28

10-27

10-26

10-25

10-24

10-23

10-22

5 50 500 1 10 100 1000

Λ

(Ge

V)

mχ (GeV)

e+e

− collider, Operator FA

√s = 250 GeV

√s = 500 GeV

√s = 1 TeVll + E ⁄jj + E ⁄

0

200

400

600

800

1000

1200

1400

1600

5 50 500 1 10 100 1000

(with an integrated luminosity of 1000 fb−1; Fermi upper limits come from arXiv:1310.0828)Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 15 / 21


. .Mono-Z signature



.Conclusions

. . .Backups

Cross sections with polarized beamsP

ositro

n p

ola

riza

tio

n P

e+

Electron polarization Pe−

√s = 500 GeV, e+e

− → llνν

-1.0

-0.5

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0 0

200

400

600

800

1000

1200

σ

(fb

)

Po

sitro

n p

ola

riza

tio

n P

e+


√s = 500 GeV, e+e

− → χχ−Z, Operator F1

-1.0

-0.5

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0 0

20

40

60

80

100

120

σ

(fb

)

Po

sitro

n p

ola

riza

tio

n P

e+


√s = 500 GeV, e+e

− → χχ−Z, Operator FP

-1.0

-0.5

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0 0

20

40

60

80

100

120

σ

(fb

)

(ℓℓνν, j jνν, j jℓν are similar) (OF1, OF2, OFH, OFA are similar) (OFP)

W± only couples to left-handed e− (right-handed e+).

e± couples to Z0 viag2

2cosθW(gL eLγ

µeL + gR eRγµeR)Zµ.

gL =−1+2sin2 θW ≃−0.56, gR = 2sin2 θW ≃ 0.44, g2L/g

2R ≃ 1.56.

The left-handed e− (right-handed e+) coupling to Z0 is stronger.



. .Mono-Z signature



.Conclusions

. . .Backups


ositro

n p

ola

riza

tio

n P

e+


√s = 500 GeV, e+e

− → llνν

-1.0

-0.5

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0 0

200

400

600

800

1000

1200

σ

(fb

)

Po

sitro

n p

ola

riza

tio

n P

e+


√s = 500 GeV, e+e


-1.0

-0.5

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0 0

20

40

60

80

100

120

σ

(fb

)

Po

sitro

n p

ola

riza

tio

n P

e+


√s = 500 GeV, e+e


-1.0

-0.5

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0 0

20

40

60

80

100

120

σ

(fb

)


The dashed box indicates the polarization ranges achievable at the ILC:−0.8≤ Pe− ≤+0.8, −0.3≤ Pe+ ≤+0.3.

In order to obtain the maximal signal significance,

▲ (Pe− , Pe+) = (+0.8,−0.3) is optimal for OF1, OF2, OFH, OFA;Æ (Pe− , Pe+) = (+0.8,+0.3) is optimal for OFP.



. .Mono-Z signature



.Conclusions

. . .Backups


ositro

n p

ola

riza

tio

n P

e+


√s = 500 GeV, e+e

− → llνν

-1.0

-0.5

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0 0

200

400

600

800

1000

1200

σ

(fb

)

Po

sitro

n p

ola

riza

tio

n P

e+


√s = 500 GeV, e+e


-1.0

-0.5

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0 0

20

40

60

80

100

120

σ

(fb

)

Po

sitro

n p

ola

riza

tio

n P

e+


√s = 500 GeV, e+e


-1.0

-0.5

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0 0

20

40

60

80

100

120

σ

(fb

)

▲ ▲



In order to obtain the maximal signal significance,▲ (Pe− , Pe+) = (+0.8,−0.3) is optimal for OF1, OF2, OFH, OFA;

Æ (Pe− , Pe+) = (+0.8,+0.3) is optimal for OFP.



. .Mono-Z signature



.Conclusions

. . .Backups


ositro

n p

ola

riza

tio

n P

e+


√s = 500 GeV, e+e

− → llνν

-1.0

-0.5

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0 0

200

400

600

800

1000

1200

σ

(fb

)

Po

sitro

n p

ola

riza

tio

n P

e+


√s = 500 GeV, e+e


-1.0

-0.5

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0 0

20

40

60

80

100

120

σ

(fb

)

Po

sitro

n p

ola

riza

tio

n P

e+


√s = 500 GeV, e+e


-1.0

-0.5

0.0

0.5

1.0

-1.0 -0.5 0.0 0.5 1.0 0

20

40

60

80

100

120

σ

(fb

)

▲ ▲

Æ Æ



In order to obtain the maximal signal significance,▲ (Pe− , Pe+) = (+0.8,−0.3) is optimal for OF1, OF2, OFH, OFA;Æ (Pe− , Pe+) = (+0.8,+0.3) is optimal for OFP.



. .Mono-Z signature



.Conclusions

. . .Backups

Sensitivity improvements

Λ (G

eV

)

mχ (GeV)

e+e

− collider, √s = 500 GeV, Operator F1

jj + E ⁄ , Unpolarized

ll + E ⁄ , Unpolarized

jj + E ⁄ , (Pe−, Pe

+) = (+0.8, −0.3)

ll + E ⁄ , (Pe−, Pe

+) = (+0.8, −0.3)

0

100

200

300

400

500

600

0 50 100 150 200

1000 fb−1

Λ (G

eV

)

mχ (GeV)

e+e

− collider, √s = 500 GeV, Operator FP

jj + E ⁄ , Unpolarized

ll + E ⁄ , Unpolarized

jj + E ⁄ , (Pe−, Pe

+) = (+0.8, +0.3)

ll + E ⁄ , (Pe−, Pe

+) = (+0.8, +0.3)

0

200

400

600

800

1000

1200

1400

0 50 100 150 200

1000 fb−1

Lepton channel ℓ+ℓ− + /ESunpol Spol Spol/Sunpol

OF1 5.69 10.1 1.78OF2 6.24 10.9 1.75OFH 5.50 9.70 1.76OFP 7.47 13.4 1.79OFA 5.25 9.29 1.77

Hadron channel j j+ /E

Sunpol Spol Spol/Sunpol

OF1 14.3 26.0 1.82OF2 16.1 28.6 1.78OFH 13.5 24.8 1.84OFP 18.7 34.4 1.84OFA 12.3 23.0 1.87

Signal significances without and withpolarized beams for the benchmark pointsat ps = 500 GeV (100 fb−1):



. .Mono-Z signature



.Conclusions

. . .Backups

Conclusions and discussions

...1 In addition to DM direct and indirect detection, DM searches atcolliders provide an independent and complementary way toexplore the microscopic nature of DM particles.

...2 The mono-Z searching channel at e+e− colliders is sensitive to theDM couplings to Z Z/Zγ and to e+e−.

...3 Polarized beams are helpful to improve the signal significance.

Thanks for your attentions!



. .Mono-Z signature



.Conclusions

. . .Backups

Conclusions and discussions

...1 In addition to DM direct and indirect detection, DM searches atcolliders provide an independent and complementary way toexplore the microscopic nature of DM particles.

...2 The mono-Z searching channel at e+e− colliders is sensitive to theDM couplings to Z Z/Zγ and to e+e−.

...3 Polarized beams are helpful to improve the signal significance.

Thanks for your attentions!



. .Mono-Z signature



.Conclusions

. . .Backups

Backup slides



. .Mono-Z signature



.Conclusions

. . .Backups

Mono-Z: e+e− colliders vs. LHCΛ

(G

eV

)

mχ (GeV)

e+e


√s = 250 GeV

√s = 500 GeV

√s = 1 TeV

ll + E ⁄jj + E ⁄

0

100

200

300

400

500

600

700

800

5 50 500 1 10 100 1000

This work10-1 100 101 102 103

mχ [GeV]

10-3

10-2

10-1

100

101

102

103

104

Λ[G

eV]

ZZχχ, dim−5

ZZχχ, dim−7 (no photons)

ZZχχ, dim−7 (max. photons)

Interaction scale exclusion

ATLAS excluded (90%CL)

LHC, ps = 7 TeV, 4.6 fb−1

[Carpenter, Nelson, Shimmin, Taitand Whiteson, arXiv:1212.3352]



. .Mono-Z signature



.Conclusions

. . .Backups

DM couplings to e+e−: mono-Z vs. monophoton

Λ (G

eV

)

mχ (GeV)

e+e

− collider, Operator FA

√s = 250 GeV

√s = 500 GeV

√s = 1 TeVll + E ⁄jj + E ⁄

0

200

400

600

800

1000

1200

1400

1600

5 50 500 1 10 100 1000

⇐ This work

[Chae and Perelstein, arXiv:1211.4008]Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 21 / 21

Documents

Searching for dark matter in the mono-Z channel at high ...yzhxxzxy.github.io/slides/1312_DM_monoZ_eecld.pdf · Searching for dark matter in the mono-Z channel at high energy e+e