Footprint of Triplet Scalar Dark Matter in Direct, Indirect Search and Invisible Higgs Decay

0.17 MB·English

by  Seyed Yaser Ayazi

From Higgs to Dark Matter, Geilo, Norway, December 14 17, 2014 1
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Footprint of Triplet Scalar Dark Matter in Direct, Indirect Search and Invisible
Higgs Decay
Seyed Yaser Ayazi1 and S. Mahdi Firouzabadi2
1School of Particles and Accelerators, Institute for Research in Fundamental
Sciences (IPM),P.O. Box 19395 −5531,Tehran,Iran and
2Department of Physics, Shahid Beheshti University, G. C., Evin, Tehran 19839, Iran
In this talk, we will review Inert Triplet Model (ITM) which provide candidate for dark matter
(DM) particles. Then westudypossible decaysof Higgs boson toDMcandidate andapply current
experimental data for invisible Higgs decay to constrain parameter space of ITM. Wealso consider
indirect search for DM and use FermiLAT data to put constraints on parameter space. Ultimately
5 wecomparethislimit withconstraintsprovidedbyLUXexperimentforlowmassDMandinvisible
1 Higgs decay.
0
2
1. INTRODUCTION 2. THE MODEL
n
a
J InITM,the matter contentofSMis extendedwith

5 There are strong evidences for non-baryonic DM a SU(2)L triplet scalar with Y = 0 or Y = 2. These
2 whichaccordingto Plancksatellite[1]constitute more additionalfieldsareoddunderZ2symmetrycondition
while all the SM fields own even eigenvalues. The
than 0.26 of energy density in the universe. WIMP’s
h] asarelicremnantsofearlyuniversearethemostplau- Z2 symmetry is not spontaneously broken since the
p sible candidates for DM. Since the standard model triplet does not develop a vacuum expectation value.
- (SM) cannot explain DM evidences, there is a strong The triplet T for Y = 0 has VEV = 0 and the SM
p
Higgs doublet H and the triplet T scalars are defined
motivationto extendSM in a way to providesuitable
e
h DMcandidate. Singletscalarorfermionfieldsarepre- as:
[ ferred as simple candidates for DM. It is shown that
v1 aalrleowsterdictrleygiloimnsitoedf pbayraWmMetAerPs dspaatace[2fo],r[3t].heOsenemoofdtehles T = √−12TT−0 −−√1T2+T0 !,hHi= √12(cid:18)v0 (cid:19), (1)
6 simplest models for a scalar dark matter is ITM. In
7 this model, a scalar SU(2) triplet is odd under Z where v = 246 GeV. The relevant Lagrangian which
L 2
1 symmetry so that they can directly couple to the SM is allowed by Z symmetry can be given by:
2
6 particles and the neutral components of the triplets
0 play role of DM. = DµH 2+trDµT 2 V(H,T),
. L | | | | −
1 V(H,T) = m2 H 2+M2tr[T2]+λ H 4
1
0 | | | |
5 After a few decades of expectations, the LHC has + λ2(tr[T2])2+λ3 H 2tr[T2], (2)
1 foundaSMlikeHiggsparticlewithamassof125GeV. | |
: Since the Higgs boson can participate in DM-nucleon In the case Y = 0, ITM has three new parameters
v
scattering and DM annihilation, current analysis of compared to the SM. We require that Higgs poten-
i
X the LHC data and measurements of its decay rates tial is bounded from below, which leads to following
r would set limit on any beyond SM that provides a conditions on the parameters of the potential:
a DM candidate.
1
λ , λ 0, (λ λ )1/2 λ >0 . (3)
1 2 1 2 3
In this talk, we extend SM by a SU(2) triplet ≥ − 2| |
L
scalar with hypercharge Y = 0,2. The lightest com-
The conditions for local minimum are satisfied if and
ponent of triplet field is neutral and providessuitable only if m2 < 0, v2 = m2/2λ and 2M2+λ v2 > 0.
1 3
candidateforDM[4]. Then,wereviewallowedparam- −
The masses of triplet scalars can be written:
eters space of ITM by PLANCK data and invisible
higgs decay measurement, direct and indirect detec-
1
tion. mT0 =mT± = M2+ 2λ3v2. (4)
r
This letter is organized as follows:In the next sec- Note that at tree level, masses of neutral and
tion, we introduce the model. In section 3, we will charged components are the same, but at loop level
review relic density, and constraints which arise from the T are slightly heavier than T0 [5]. The scalar
±
experimentalobservablesatLEPandLHC,directde- andgaugeinteractionsofITMhavebeenextractedin
tection and indirect detection. The conclusions are terms of real fields in [6]. In case Y =0, the Z sym-
2
given in section 4. metry ensures that T0 cannot decay to SM fermions
2 From Higgs to Dark Matter, Geilo, Norway, December 14 17, 2014
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FIG.1: RelicdensityasafunctionofDMmassforallthe
FIG.2: Therelic densityplot inλ3 andDMmassplane.
valid values of λ3. The shadowed panel indicates regions Theblueregionleadstomoreparticipationinrelicdensity.
in which T0 particles contribute more than 10 percent of
dark matter density.
freeze-out, the universe is hot and dense. As the uni-
verse expand, the temperature fall down. Ultimately
and can be considered as cold DM candidate. Never-
T0 particles will become so rare that they will not
theless the Z boson can decay to T . The decay rate
± be able to find each other fast enough to maintain
of Z T T is given by:
→ ∓ ± the equilibrium abundance. So the equilibrium ends
Γ(Z T T )) = g2c2WmZ(1 4m2T±)3/2, (5) andthefreeze-outstarts. Inertparticles,T0,cancon-
→ ∓ ± π − m2Z tribute in the relic density of DM through freeze-out
mechanism. Solving Boltzman equation will deter-
where g is the weak coupling and cW = cosθW. The mine the freeze-out abundance. We have used Lan-
Z boson decay width was measured by LEP experi- Hep [7] to generate model files which Micromega 3.2
ment(Γ =2.4952 0.0023GeV). Thismeasurement
Z [8] employs to calculate relic density. The relic den-
±
is consistent with SM prediction. This means the Z
sity as a function of interaction rate changes for the
bosondecaywidthwillstrictlyconstrainITMparam-
different values in parameter space. Fig. 1 and 2 in-
eters space. Therefore, we assume that mT0,mT± > dicate how inert particles contribute in dark matter
45.5 GeV.
density for the different values of mass and coupling.
In case Y = 2 the SU(2) triplet can be parame-
L In large mass regimes and low couplings, Inert par-
terized with five new parameters[6]. The ITM with
ticle can constitute whole the dark matter which is
Y=2,isalreadyexcludedbythelimitsfromdirectde-
very plausible. As it is seen in Fig. 1 and 2, in con-
tectionexperiments. Therewon’tbeanyusetostudy
text of ITM, in mass regimes lower than 7 TeV, relic
the case in this regard.
densityconditionsaresatisfied. We emphasisthatfor
m 2 TeV, ITM can not saturate the relic den-
DM
≤
sityandit demandsmulti-componentsDM toexplain
3. OBSERVABLES AND NUMERICAL
whole density.
RESULTS
In this section,we willreview the relic density con- 3.2. Direct Detection
ditions for ITM and constraints arising from experi-
mentalobservablesatLHC,directandindirectdetec-
In the case of Y = 0, DM candidate can interact
tion.
with nucleon by exchanging Higgs boson. The DM-
nucleon scattering cross section is given by [9]:
3.1. Relic Density λ2f2 m4
σ = 3 N N , (7)
SI 4πm4h(mN +mT0)2
TherelicdensityofDMiswellmeasuredbyWMAP
and Planck experiments and the current value is [1]: where the coupling constant fN is given by nuclear
matrix elements[10] and m = 0.939 GeV is nucleon
N
ΩDMh2 =0.1199 0.0027, (6) mass. ThemoststrictboundontheDM-nucleoncross
±
sectionobtainedfromLUX[11]experiment. Themini-
where h = 0.67 0.012 is the scaled current Hubble mumupperlimitonthespinindependentcrosssection
±
parameterin units of 100km/s.Mpc. In the following, is:
wewillusethisvalueasupperboundonthecontribu-
tion of ITM in production of DM. Before the onsetof σ 7.6 10 46cm2. (8)
SI −
≤ ×
From Higgs to Dark Matter, Geilo, Norway, December 14 17, 2014 3
−
As it was mentioned in Y = 2 case, Due to gauge
couplingofZ toDMcandidate,theDM-nucleoncross
sectionis10 38cm2 andmuchlargerthanupperlimit
−
by LUX experiment. This excludes all the regions of
parameter.
Fig. 4, shows allowed region in DM mass and λ
3
couplings plane which does not violate 90% C.L ex-
perimental upper bounds of LUX for mZ/2<mT0 <
m /2. In this figure, we compare these bounds with
h
other constraints which arise from other observables.
3.3. Invisible Higgs decays
A SM-like Higgs boson was discovered at the LHC
FIG. 3: The thermal average annihilation cross-section of
in 2012. Some extensions of the SM allow a Higgs
T0 (DM) to γγ as a function of the DM mass for several
particle to decay into new stable particlewhich is not
valuesofλ3. Thesolidredlinesshowstheupperlimitson
observed by ATLAS and CMS detectors yet. For ex-
annihilation cross-section which haveborrowed from [15].
ample, the Higgs boson can decay into per of DM
particles. The branching ratio of the Higgs particle
to invisible particle can be used directly to constrain
which is consistent with experimental upper limit on
parameter space of new physics. Nevertheless, invis-
Br(h Invisible)(with 95% C.L). It is remarkable
ible Higgs boson decay is not sensitive to DM cou- →
thatvalid areaof Br(h Invisible)and directdetec-
pling when mT0 > mh/2. In ITM, if triplet scalar tion experiments are ver→y similar.
massis lighterthanSMhiggsbosonmass,thenitcan
contribute to the invisible decay mode of higgs bo-
son. The total invisible Higgs boson branching ratio
is given by: 3.4. Annihilation of Dark Matter into
monochromatic gamma-ray
Br(h Invisible) = Γ(h→Inv)SM+Γ(h→2T0), (9)
→ Γ(h)ITM
DM particles annihilation or decay can produce
where Γ(h) =4.15MeV [12] is totalwidth ofhiggs monochromatic photon and contribute to the diffuse
SM
bosoninSMandΓ(h) istotaldecaywidthofhiggs gamma-ray background. In ITM, T can contribute
ITM ±
boson in ITM: to annihilation of DM candidate into monochromatic
photons 2T0 2γ. The amplitude of possible an-
→
Γ(h)ITM =Γ(h)SM+ Γ(h 2χ). (10) nihilation of DM candidate in ITM into 2γ has been
→
χ=TX0,T±,γ calculated in [4].
Flux upper limits for diffuse gamma-ray back-
The partial width for h 2T0 and h T T are
± ± ground and gamma-ray spectral lines from 7 to
→ →
given by:
300 GeV obtained from 3.7 years data has been pre-
sentedbyFermiLATcollaborationin[15]. Inthissec-
Γ(h 2T0) = λ23v02 1 4m2T0, tion, we obtain thermal average cross section of an-
→ 4πmhr − m2h nihilation and apply these data to set constrain on
Γ(h T T ) = λ23v02 1 4m2T±, (11) ITM parameter space. In Fig. 3, we display the ther-
→ ± ± πmhr − m2h mal average cross section for annihilation of DM to
γγ as a function of the DM mass for severalvalues of
andh 2γ was givenin [4]. The SMbranchingratio λ . For process 2T0 γγ, we assume E = m .
3 γ DM
forthe→decayofHiggstoinvisibleparticlesis1.2 10 3 The solid red lines de→picts the upper limits on anni-
−
×
which is produced by h ZZ 4ν [13]. A search hilation cross-section for NFW density profile in the
∗
→ →
for evidence of invisible decay mode of a Higgs bo- Milky Way which have borrowed from [15]. In this
son has done by ATLAS collaboration and an upper figure, for m > 63 GeV, total annihilation cross-
DM
limitof75%with95%C.Lissetonbranchingratioof section is much lower than FermiLAT upper limit.
Higgs boson invisible mode [14]. Since invisible higgs This means FermiLAT data can not constrain ITM
decay is forbidden kinematically for m > m , we parametersspace in this region. Nevertheless,for low
D h/2
present our results for Br(h Invisible) and other DM mass (m <63 GeV near to the pole of Higgs
DM
→
observables only for mZ/2<mT0 <mh/2. In Fig. 4, propagator at mDM = mh/2), the annihilation cross
we suppose mZ/2 < mT0 < mh/2 and depict al- section increases and will be larger than upper limit.
lowed region in mass of DM and λ coupling plane To study this phenomena, we consider the minimum
3
4 From Higgs to Dark Matter, Geilo, Norway, December 14 17, 2014
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4. CONCLUDING REMARKS
In this talk, we have presented an extension of SM
which includes a SU(2) triplet scalar with hyper-
L
charge Y = 0,2. This model provide suitable candi-
dateforDM,becausethelightestcomponentoftriplet
field is neutral and for the m <7 TeV, conditions
DM
of relic abundance are satisfied. We focus on param-
eter space which is allowed by PLANCK data and
study collider phenomenology of inert triplet scalar
DM at the LHC.
We have shown that the effect of ITM on invisible
Higgs decay for low mass DM (m < 63 GeV) can
DM
be as large as constraints from LUX direct detection
experiment ( see Fig. 3-b).
FIG. 4: Shaded areas depict ranges of parameter space
inmassofDMandλ3 couplingplanewhichareconsistent We consider the annihilation cross section of DM
with experimental measurements of Br(h → Invisible), candidate into 2γ. The minimum upper limit on an-
upper limit on σFermiLAT (indirect detection) and σLUX nihilationcross-sectionfromFermiLAThavebeenem-
(direct detection). ployed to constraint parameters space of ITM. We
also compared our results with constraints from di-
rect detection and showed for 52 < m < 63 GeV,
upper limit on σ = 0.33 10 28 for NFW DM
FermiLAT − FermiLATconstraintisstrongerthandirectdetection
×
profile [15] in Fig. 4 and depict allowed regions on
constraint for low mass DM.
DM mass and λ coupling plane which are consistent
3
with this limit. We compared all results for direct Acknowledgement
search, invisible Higgs decay and indirect search in We would like to thank the organizer of ”From
this figure. It is remarkable that indirect search con- Higgsto DarkMatter” conference held atGeilo, Nor-
straintisstrongerthandirectdetectionlimitinregion way (14-17 December 2014) where this talk was pre-
52<mDM <63. sented.
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