Dark sector shining through 750 GeV dark Higgs boson at the LHC

0.28 MB·

by  P. Ko

Dark sector shining through 750 GeV dark Higgs boson at the LHC
P. Ko and Takaaki Nomura
∗ †
School of Physics, KIAS, Seoul 02455, Korea
(Dated: May 23, 2016)
We consider a dark sector with SU(3)C ×U(1)Y ×U(1)X and three families of dark fermions
thatarechiralunderdarkU(1)X gaugesymmetry,whereasscalardarkmatterX istheSMsinglet.
U(1)X darksymmetryisspontaneouslybrokenbynonzeroVEVofdarkHiggsfieldhΦi,generating
themassesofdarkfermionsanddarkphotonZ′. TheresultingdarkHiggsbosonφcanbeproduced
attheLHCbydarkquarkloop(involving3generations)andwilldecayintoapairofphotonthrough
chargeddarkfermionloop. Itsdecaywidthcanbeeasily∼45GeVduetoitspossibledecaysintoa
6 pairofdarkphoton,whichisnotstronglyconstrainedbythecurrentLHCsearchespp→φ→Z′Z′
1 followed by Z′ decays into the SM fermion pairs. The scalar DM can achieve thermal relic density
0 without conflict with direct detection bound or theinvisible φ decay intoa pair of DM.
2

y
INTRODUCTION Let us introduce a dark sector with new dark fermions
a
M whichcarryboththeSMSU(3)C U(1)Y quantumnum-
×
Recently both ATLAS and CMS Collaborations an- bers as well as darkU(1)X gauge charges,anda SM sin-

0 nouncedthattherearesomeexcessinthediphotonchan- glet complex scalar field X as summarized in Table I. In
2 nel around mγγ 750 GeV [1, 2]: thismodel,everyright-handedfermionfR intheSMhas
≈ its partner fermion FL with nonzero dark charge in the
ph] σ(pp→φ→γγ) = (6.2+−22..40) fb (ATLAS) (1) udnardkersetchteorS.MThgeanutgheetFraLnfsRforompeartaiotonr. bIetcsomnoenszienrvoardiaarnkt
= (5.6 2.4) fb (CMS) (2)
- ± charge is cancelled by the dark charge of scalar DM X
p Γ (φ) 45GeV(ATLAS) (3)
e tot ∼ in such a way that FLfRX becomes gauge invariant op-
h erator. And F becomes vectorlike under the SM gauge
whereasthe CMSdata prefers a smaller decaywidth [2]. L
[ groupbyintroducingitschiralpartnerF . Themodelis
Furthermore, at Moriond 2016, ATLAS and CMS have R
2 reportedthatthelocal(global)significancesofthedipho- very simple and free from gauge anomalies for arbitrary
v a and b. A novel feature of this model is that the new
ton excess are about 3.9(2.0)σ and 3.4(1.6)σ, respec-
0 fermions F and F are chiral under dark U(1) gauge
tively, where CMS added 0.6 fb 1 new data to the 13 L R X
9 −
symmetry so that they are massless before spontaneous
4 TeV analysis and combined with 8 TeV data [3, 4].
symmetry breaking. And their effects on φ gg,γγ
2 Thisexcessmotivatedalotofphenomenologicalstudy →
0 on possible scenarii of new physics beyond the Stan- throughtrianglediagramevadesfromthedecouplingthe-
. orem as their mass becomes heavy.
1 dard Model (BSM) which include models related to DM
0 physics [5–44], new gauge symmetry models [13, 20, 23, The Yukawa interactions and the scalar potential in-
6 35, 38–40, 43, 45–57] and other models [58–161]. It is cluding new fields in the dark sector are described by
1
not easy to generate a large enough width 45 GeV
: ∼
v with large BR(φ γγ), maintaining relevant cross sec-
Xi tion of σ(pp→φ→→γγ)∼O(10) fb and evading various LYukawa =yEE¯LERΦ+yNN¯LNRΦ†+yUU¯LURΦ†
collider search bounds.
ar In this letter, we solve these problems by introducing +yDD¯LDRΦ+yEeE¯LeRX +yUuU¯LuRX†
darkU(1)X gaugesymmetry,darkphotonZ′, threegen- +yDdD¯LdRX +h.c., (4)
erations of dark fermions with SU(3) U(1) charges
C Y
×
andsingletscalarDMX. DarkphotonZ candecayinto
′
SM fermions via a small Z Z mixing. Dark fermions
′
−
areassumedtobechiralunderU(1) darkgaugesymme- Fermions Scalar
X
tryandgetmassiveafterspontaneousbreakingofU(1)X EL ER NL NR UL UR DL DR Φ X
by nonzero VEV of U(1)X-charged complex scalar field SU(3) 1 1 1 1 3 3 3 3 1 1
Φ, and a new Higgs boson φ appears from Φ. This sim-
SU(2) 1 1 1 1 1 1 1 1 1 1
pinlteerseesttuipngfosrigdnaartkurmesaatttehrigishaenveiargbylecDolMlidesrcse.nario with U(1)Y −1 −1 0 0 23 23 −31 −31 0 0
U(1)X a −b −a b −a b a −b a+b a
TABLE I: Contents of new fermions and scalar fields
MODEL
and their charge assignments under the gauge symmetry
SU(3)×SU(2)L×U(1)Y×U(1)X. We consider three families
of dark fermions.
2
V =µ2H H +λ(H H)2+µ2Φ Φ+µ2 X X X˜ ;
† † Φ † X † µ
+λΦ(Φ†Φ)2+λX(X†X)2+λHΦ(H†H)(Φ†Φ) = 1Wa Waµν
+λ (H H)(X X)+λ (X X)(Φ Φ). (5) Lkin − 4 µν
HX † † XΦ † †
1 1 s B˜µν
(B˜ ,X˜ ) χ , (9)
where H denote the SM Higgs field [177]. We have sup- − 4 µν µν sχ 1 ! Z˜′µν !
pressed the generation indices on the SM and the dark
where s sinχ. The kinetic terms are diagonalized by
fermionsforsimplicity. TheYukawainteractionsprovide χ ≡
the following non-unitary transformation;
masstermsforthedarkfermionsF,whichdecaythrough
cFan→didXatfe.. XNoitsetthheatSMthesriengilsetananadcccidanenbtaelaZgosoydmDmMe- B˜µ = 1 −tχ Bµ , (10)
try, X X, F F and F F wh2ich make X˜µ ! 0 1/tχ ! Xµ !
L L R R
→ − → − → −
X stable at renormalizable level. There could be gauge where t = tanχ. After Φ and H develop non-zero
χ
invariantoperatorsthatbreakthisaccidentalZ2 symme- VEVs,the massmatrixforneutralgaugefieldisapprox-
try: X†Φn and/or XΦn which would generate nonzero imately given by
VEV for X after U(1) symmetry breaking by nonzero
X T
Φ =0. Gauge invariance requires that a/(a+b)=n 1 Z˜ (g2+g2)v2 t g g2+g2v2 Z˜
h i6 ± ′ χ ′ ′ .
to be an integer. We can forbid this type of operators 8 X ! tχg′ g2+g′2v2 4(ap+b)2gX2 vΦ2 ! X !
by making a judicious choice of a,b so that a/(a+b)
(11)
± p
is not an integer. Or we can make n very large so that where W3 =cosθ Z +sinθ A and B = sinθ +
evenif X develops a nonzeroVEV, the lifetime of X be- µ W µ W µ µ − W
cosθ A areused. Assumingχ 1[178],neutralgauge
W µ
comes long enough (τ & 1028 sec) to be a good DM ≪
X boson masses are
candidate. This model can be considered as a general-
1
ization of the singlet portal extensions of the SM where m2Z ≃ 4(g2+g′2)v2, m2Z′ ≃(a+b)2gX2 vΦ2. (12)
dark matter lives in the dark sector [166], but the dark
sector now contains dark fields which are charged under The mass eigenstates are given by
the SM gauge group as well as dark gauge group, unlike
Z cosθ sinθ Z˜
the earlier models [166]. µ = − µ , (13)
ThegaugesymmetryisbrokenafterH andΦgetnon- Zµ′ ! sinθ cosθ ! Xµ !
zero VEVs: and the small Z Z mixing angle is given by
′
−
g g2+g2v2
G+ 1 tan2θ ′ ′ t . (14)
H = √12(v+h+iG0)! , Φ= √2(vφ+φ+iGφ), ≃ 2(pm2Z −m2Z′) χ
(6) InFig.1,weshowthebranchingratiosofZ′asafunction
whereG ,G0 andG areNGbosonswhichareabsorbed of its mass. Here q = u,d,s,c,b, and νν¯ includes all the
± φ
by W±, Z and Z′ respectively. We shall call φ as dark three flavors. Note that Z′ decays into the SM through
Higgs boson, since it appears as a result of spontaneous the kinetic mixing so that Γ(Z′)/mZ′ O(χ2) . 10−4.
∼
breaking of dark U(1)X gauge symmetry. Therefore Z′ would be a very narrow resonance.
We also find that Yukawa coupling of new dark
We assume λ is negligible and the mixing between
HΦ
SMHiggsbosonhandφisnegligiblysmallwhichiscon- fermions andλΦ canbe written interms of gX andmZ′;
sistentwith the currentHiggs data analysis [167]. Then √2(a+b)g M
the scalar VEVs are given approximately by yF = X F, (15)
m
′Z
(a+b)2m2g2
φ X
v −µ2, vΦ −µ2Φ. (7) λΦ = 2m2Z′ . (16)
≃r λ ≃s λΦ
In our analysis,we require these couplings are perturba-
tive as yF <4π and λ <4π.
The masses of new fermions are generated such that Φ
yF PHENOMENOLOGY
M = v , (8)
F Φ
√2
750 GeV Diphoton Excess
where F =E,N,U and D.
We consider kinetic mixing of the U(1) and U(1) In this section, we analyze the production of φ and
Y X
gauge fields which are denoted respectively as B˜ and its decays at the LHC 13 TeV. The production of φ is
µ
3
1.00 0.8
yU,D=4Π Kgg=2.0
qq 0.7
0.50
0.6 ΛF=4Π
e+e-+Μ+Μ-
R 0.20 0.5 40 30
B ΝΝ X 20
g
0.4
Τ+Τ-
0.10
10
0.3
5
0.05 0.2
1
150 200 250 300 350 0.1
m @GeVD 150 200 250 300 350
Z'
m @GeVD
Z'
FIG. 1: Branching ratios of Z′ as a function of mZ′.
FIG.2: Theσ(gg→φ)inunitofpbwhere3copyoffermions
in Table I are applied and a ≃ b ≃ 1 with a 6= b is adopted.
We used parameter set as {MU,D,ME,N,mX,λXΦ} =
throughgluonfusionprocesswherethe relevanteffective {800GeV,400GeV,350GeV,0.075}. Gray(light gray) region
coupling is given by indicate yU,D(λΦ)>4π usingEq. (15) and (16).
α (a+b)√2g
= s XA (τ ) φGaµνGa ,
Lφgg 8π  mZ′ 1/2 F  µν
F=U,D
X
  (17) where Q and NF are electric charge and number of
F c
where A (τ) = 2τ[1 + (1 τ)f(τ)] with f(τ) = color of an exotic fermion F. The partial decay width
1/2
−
[sin−1(1/√τ)] for τ ≥ 1 and τF ≡ 4m2F/m2φ. We for φ→Zγ is also formulated by
find that the effective coupling is described by mZ′
and g since exotic fermion mass is given by VEV
X
of Φ. Applying the effective coupling, the produc- m3 m2 3
btiyonucserososfseCcatlicoHnEfPor [t1h6e9]dawrikthHiCgTgEsQ6φLisPDcaFlcu[l1a7t0e]d. Γφ→Zγ =32φπ |AZγ|2 1− mZ2φ! , (20)
Fig. 2 shows the cross section in the mZ′ − gX plane A =2√2αsWgX
using parameter setting {MU,D,ME,N,mX,λXΦ} = Zγ πcW
K{w8e-0fa0aclGtsooerVinf,od4r0ic0galGtueoeVnex,fc3ul5us0idoGendeaVps,a0Kr.a0gm7g5e}=tera2sr.0ea.giorInenfewtrheheniccfiheguvairnoed-, × F NcF(am+Z′b)Q2F[I1(τF,λF)−I2(τF,λF)],
X
late perturbative condition yU,D < 4π and λ < 4π de-
Φ
rivedfromEq.(15) and(16)respectively. Thus asizable
productioncrosssectioncanbe obtainedin perturbative where λF = 4m2F/m2Z and the loop integrals are given
parameter region. as [171]:
The partial decay widths for φ gg mode is derived
→
by
xy x2y2
2 I (x,y)= + [f(x)2 f(y)2]
α2m3 (a+b)g 1 2(x y) 2(x y)2 −
Γ = s φ XA (τ ) . (18) − −
φ→gg 32π3 (cid:12)(cid:12)F=U,D 2mZ′ 1/2 F (cid:12)(cid:12) + x2b [g(x) g(y)],
(cid:12) X (cid:12) (x y)2 −
(cid:12) (cid:12) −
Similarlythe partial(cid:12)(cid:12)decaywidthforφ→γγ is(cid:12)(cid:12) givenvia I2(x,y)= xy [f(x)2 f(y)2],
dark fermion loops such that − 2(x y) −
−
2 g(t)=√t 1sin−1(1/√t). (21)
α2m3 (a+b)g Q2 −
Γ = φ NF X FA (τ ) ,
φ→γγ 256π3 (cid:12) c mZ′ 1/2 F (cid:12)
(cid:12)XF (cid:12)
(cid:12) (cid:12) (19) Ontheotherhand,thedecaywidthsofφintoZ Z ,X X
(cid:12) (cid:12) ′ ′ ∗
(cid:12) (cid:12)
4
and F¯F modes are given at tree level as 1
Z'Z'
Γφ Z′Z′ =(a+b)2gX2 m2Z′ 0.1 mX=350GeV
→ 32πmφ
× m4φ−4m2φmm4Z2Z′′ +12m4Z′s1− 4mm2φ2Z′ , BR 0.01 gg
XX
(22)
0.001
λ2 m2 4m2
Γφ→X∗X =16π(aX+Φb)2Zg′X2 mφs1− m2φX, (23) ΓΓ ZΓ
10-4
g2 M2 4M2
Γφ→F¯F =4Xπm2ZF′mφs1− m2ZF′ . (24) 0.2 0.4 gX0.6 0.8 1.0
Fig. 3 shows the total decay width of φ in the mZ′ gX FIG. 4: Branching fraction for decay of φ.
−
plane where the same parameter set as in Fig. 2 is
used. The branching fractions of φ decay can be ob-
tained by partial decay widths, which is shown as a 0.8
function of gX in Fig. 4 for mZ′ = 300 GeV with the yU,D=4Π
0.7
above parameter setting. Finally Fig. 5 shows contours
othfeσre(gfogre→finφd)BthRa(tφ3→ γ1γ0)fbinctrhoessmseZc′t−iongXforpldainpeh.otWone 0.6 ΛF=4Π 10
−
modecanbeobtainedintheregionofg 0.2 0.5and 0.5 7
X
≃ −
mZ′ < mS/2, simultaneously with a rather large decay gX 5
0.4
width of φ: Γ (φ) 5 40 GeV.
tot
≈ −
3
0.3
0.8
yU,D=4Π
0.2
0.7 ΛF=4Π 50
0.1
0.6 40
30 150 200 250 300 350
m @GeVD
0.5 Z'
20
X
g 0.4 FIG.5: Theσ(gg→φ)BR(φ→γγ)in unitoffbwith same
10
parameter setting as Fig. 2.
0.3
5
0.2
1 of DM in our model are XX (NN¯) Z Z assuming
∗ ′ ′
0.1 →
mX,N > mZ′. We have included the t(u) channel pro-
150 200 250 300 350 −
cesses mediated by virtual F exchange as well as the
m @GeVD
Z' s channel process mediated by φ exchange. Note that
−
theZ -exchangingprocessesaresuppressedsinceinterac-
FIG.3: ThetotaldecaywidthofφinunitofGeVwithsame ′
tions between Z and SM particles are small due to the
parameter setting as Fig. 2. ′
small Z Z mixing we assume.
′
−
Thethermalrelicdensityisnumericallyestimatedwith
micrOMEGAs 4.1.5 [173]to solvethe Boltzmannequa-
tion by implementing relevant interactions relevant for
Dark Matter Phenomenology the DM pair annihilation processes. In calculating the
relic density we assume a b 1 (but a = b). We
≃ ≃ 6
The DM candidates of our model are X and N. We find that the DM relic density is given dominantly by
assume that the Higgs portal coupling λ =0 for sim- scalar DM X in the parameter region where one can ex-
HX
plicity, since this case is studied in great detail [172]. plain the 750 GeV diphoton excess. It turns out that
We alsoassumethat the Yukawa couplingsinvolvingthe the relic density of N is small due to large Yukawa cou-
DM X and SM fermions in Eq. (4) are small enough pling yN which makes the amplitude for the N¯N
→
so that their contribution to thermal relic calculation φ Z Z process large. Thus the thermal relic density
′ ′
→
is negligible. Then the dominant annihilation processes of scalar DM X is calculated with fixed parameter set
5
of M ,M ,m = 800GeV,400GeV,350GeV 0.45
U,D E,N X
and{by taking {gX,λ}XΦ,m{Z′} as free parameters. W}e mΛXXS==3050 GeV
thensearchfortheparameterregionwhichgivetheright
thermal relic density, i.e. Ωh2 = 0.1199 0.0027 as re-
± 0.40
ported by Planck Collaboration [174]. The upper figure
in Fig. 6 shows the parameter region in the (mZ′,gX)
plane providing the observed relic density for λXΦ = 0. gX
On the other hand, the lower figure in Fig. 6 shows the
0.35
correspondingparameter regionin the (mZ′,λXΦ) plane
for g = 0.1 and 0.3. We find that interference between
X
t(u) channel processes and φ exchanging s channel
− −
process makes λXΦ dependence of the relic density non- 0.30
trivial. For smaller λ and g , small amount of Higgs
XΦ X 150 200 250 300
portal coupling λHX can help us to achieve the correct mZ'@GeVD
thermal relic density. 0.035 mX=350 GeV
In this model, DM-nucleon scattering occurs through
h, φ and Z exchanges. The amplitude for Z exchange
′ ′ 0.030
will be small since it involves Z Z mixing which can
′
−
be sufficiently small. Also the Higgs contribution can 0.025 gX=0.3
be made small enough if we take a small λ . For φ
HX F
exchange,wehavecontributiontoDM-nucleonscattering ΛX
0.020
amplitude from φ-gluon-gluon coupling in Eq. (17) and
φ X X coupling even if we suppress φ h mixing.
− − −
The relevant effective coupling is given by 0.015
gX=0.1
α λ 0.010
LXXGG = 4πS  mX2ΦA1/2(τF)X†XGaµνGaµν 150 200 250 300
F=XU,D φ mZ'@GeVD
≡ α4πSCgX†XGaµνGaµν.  (25) FIG. 6: The colored region in upper(lower) plot indicate pa-
rameter space in mZ′ −gX(mZ′ −λXΦ) plane which explain
Then the spin-independent DM-nucleon scattering cross observed relic density of X where other parameters are indi-
section is obtained as [175] cated in thefigures.
m2
σ = N f2 (26)
SI π(m +m )2 N
X N
ForsuchalargeYukawacoupling,however,wehavelarge
f 2
N = C f(N) (27) crosssectionforDMannihilationintoleptonpairthrough
m −9 g TG
N the t-channel exchange of E . Therefore when the muon
i
(g 2) isexplainedbythedarkleptonswithinourmodel,
wheremN isthenucleonmassandfT(NG) isthemassfrac- th−e thµermal relic density of X is too small and we need
tion of gluonic operators in the nucleon mass. For the
another component of DM. Therefore we don’t consider
numerical values for these parameters, we adopt values
this possibility any more in this letter.
in Ref. [176]. We find that DM-nucleon scattering cross
section is small as σ . 10 48cm2 for the λ provid-
SI − XΦ
ing the observed relic density in Fig. 6. Therefore it is Stability of the potential
difficult to observe the DM-nucleon scattering in direct
detection experiment.
Herewebrieflydiscussthestabilityofthescalarpoten-
tial. Theone-loopbetafunctionsoftheYukawacoupling
yF and λ are given by [128]
Muon (g−2)µ φ
18
It is interesting to note that this model can also solve βyF =yF 3(2NcF +1)(yF)2− 5 Q2Fg12−8g32 , (28)
(cid:20) (cid:21)
themuon(g 2) throughthedarkmuonanddarkmat-
ter loop. Fo−r mµX = 350 GeV and mEi = 400 GeV, βλΦ =8λΦ NcF(yF)2+18λ2Φ−8 NcF(yF)4 (29)
we can account for the deficit in the a = 8 10 10 XF XF
µ −
×
if yEiµ ∼ 2−3 assuming the universal yEiµ and mEi. where g1(3) are gauge couplings for SU(1)Y(SU(3)) and
If we assume flavor conserving Yukawa, y 5 is needed. the MS scheme is applied. As aroughestimation,we ig-
∼
6
nore the running of gauge couplings in the energy range LHC@√s = 13 TeV. Therefore a dedicated search for
of O(1) TeV to O(10) TeV since the moderate running dark photon pair could confirm or exclude our model.
ofgaugecouplingsinthe RHSofEq.(28)doesnotmake Our model also opens widely a new window for DM
significant changes for the running behavior of yF and model building, especially the Higgs portal DM. By as-
λΦ. In Fig. 7, we show the renormalization group run- suming that the dark sector matter fields carry nonzero
SM charges, the collider signatures become richer and
5 also the Higgs signal strength can be different from the
yF=1.2 usualHiggsportalDMmodelsinthepresenceofthemix-
ing between the dark Higgs and the SM Higgs bosons.
4
Our model can satisfy all the constraints from (in)direct
search bounds as well as DM searches at colliders.
3
F
Λ 2
CONCLUSION
1
In this letter, we proposed a new dark matter model
with3generationsofdarkfermionsthatarechiralunder
0
newdarkU(1) gaugesymmetry. Bothdarkphotonand
X
1.5 2.0 3.0 5.0 7.0 10.0 15.0 the dark fermions get their masses entirely from sponta-
Μ@TeVD neous breaking of dark U(1)X gauge symmetry from the
nonzeroVEVofΦ, anddarkHiggsbosonφ appearsas a
FIG. 7: The running of λΦ according to Eq. (28) and (29) result. Thenthediphotonexcessat750GeVisidentified
where we adopted yF =1.2 and λΦ ={1.3,1.4,1.5} at µ=1 as the dark Higgs boson from U(1) symmetry break-
X
TeV as reference points.
ing. The main decay mode of φ is a pair of dark photon
′ ′
(φ Z Z ) and could be probed at the LHC by search-
→
ingfor 4j,2j+ll,2j+E ,4l,2l+E . It isremainedto
ningofλ wherewetookλ = 1.3,1.4,1.5 asreference 6 T 6 T
Φ Φ { } be seen if the 750 GeV diphoton excess survives in the
points atµ=1TeVandassumeduniversalYukawacou-
futuredataaccumulation. Ifitdoes,themodelpresented
plings yF = 1.2 at the same µ for simplicity. We thus
in this letter would be an interesting possibility without
find thatλ cannotbe too smallortoo largeto stabilize
Φ conflict with the known experimental constraints even
the potential. Also relative magnitude between yF and
for large decay width of φ. In particular the production
λ changestherunningpropertysignificantly,whichcan
Φ and the decay of the dark Higgs boson φ involves dark
betunedbychangingU(1) chargeofΦ,a+b,according
X fermions in the triangle loops, opening a new window to
to Eq.(15) and(16). By tuning the parameters,the sta-
the dark sector.
bility of the potential can be achieved up to 10 TeV.
∼ We are grateful to Jack Kai-Feng Chen, Sung Won
The complete analysis is beyond the scope of this letter
Lee and Hwidong Yoo for discussions on the experi-
and we left it as future work.
mental status on the dark photon searches. We also
thank the anonymous referee for valuable suggestions.
Future Tests of This Model This work is supported in part by National Research
Foundation of Korea (NRF) Research Grant NRF-
2015R1A2A1A05001869, and by SRC program of NRF
Themodelpresentedinthislettercanbetestedatthe
GrantNo. 20120001176fundedbyMESTthroughKorea
upcoming LHC experiments by searching for a pair of
Neutrino Research Center at Seoul National University
dark photons around m ′ ′ 750 GeV in the following
Z Z ∼ (PK).
channels:
′ ′
pp φ Z Z
→ →
′ ′
Z Z 4j ,2j+ll ,2j+E ,4l ,2l+E ,
T T
→ 6 6
where E is from νν¯ pair. Note that the total de- ∗ [email protected]
T
cay wid6 th of dark photon Z′ should be very narrow, † [email protected]
Γtot(Z′)/mZ′ . 10−4. If the current ATLAS result on [[12]] TChMeSACToLlAlaSbocroaltlaiobnor[aCtMionS,CAoTllLaAboSr-aCtOioNn]F,-c2o0l1li5s-i0o8n1s.at
Γ 45 GeV is confirmed in the future, our model
φ ∼ 13TeV,” CMS-PAS-EXO-15-004.
predicts that the main decay channel of dark Higgs φ
[3] The ATLAScollaboration, ATLAS-CONF-2016-018.
should be a pair of dark photon, with a large cross sec- [4] CMS Collaboration [CMS Collaboration], CMS-PAS-
′ ′
tion, σ(φ Z Z ) O(5 40) pb (see Fig. 1) at the EXO-16-018.
→ ≈ −
7
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