. . . .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
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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).... ... ... ...
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 3 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 4 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 5 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 6 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 7 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 8 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 9 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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)
2;veto events with mrecoil < 140 GeV.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 9 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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)
2;veto events with mrecoil < 140 GeV.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 9 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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
Diffe
ren
tia
l cro
ss s
ectio
n (
fb /
Ge
V)
mrecoil (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
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.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 9 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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
Diffe
ren
tia
l cro
ss s
ectio
n (
fb /
Ge
V)
mrecoil (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
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.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 9 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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)
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 10 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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)
2;veto events with mrecoil < 200 GeV.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 11 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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
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)
2;veto events with mrecoil < 200 GeV.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 11 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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
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)
2;veto events with mrecoil < 200 GeV.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 11 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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
Fra
ctio
n o
f e
ve
nts
mrecoil (GeV)
e+e
− collider, √s = 500 GeV, jj + 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
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)
2;
veto events with mrecoil < 200 GeV.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 11 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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
Fra
ctio
n o
f e
ve
nts
mrecoil (GeV)
e+e
− collider, √s = 500 GeV, jj + 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
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)
2;veto events with mrecoil < 200 GeV.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 11 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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)
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 12 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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
− collider, Operator F2
√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
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 14 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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+
Electron polarization Pe−
√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+
Electron polarization Pe−
√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.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 16 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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+
Electron polarization Pe−
√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+
Electron polarization Pe−
√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)
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.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 16 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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+
Electron polarization Pe−
√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+
Electron polarization Pe−
√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)
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.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 16 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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+
Electron polarization Pe−
√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+
Electron polarization Pe−
√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
)
▲ ▲
Æ Æ
(ℓℓνν, j jνν, j jℓν are similar) (OF1, OF2, OFH, OFA are similar) (OFP)
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.
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 16 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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):
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 17 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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!
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 18 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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!
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 18 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.Conclusions
. . .Backups
Backup slides
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 19 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.Conclusions
. . .Backups
Mono-Z: e+e− colliders vs. LHCΛ
(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
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]
Zhao-Huan YU (IHEP) Searching for dark matter in the mono-Z channel at e+e− colliders Dec 2013 20 / 21
. . . .DM searches at colliders
. .Mono-Z signature
. . . . . . . .Sensitivity
. .Beam polarization
.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