Charged Higgs boson phenomenology in Supersymmetric models with Higgs triplets

1.1 MB·English

by  J. L. Diaz-Cruz

SHEP-06-35
DCP-07-04
LPT-ORSAY-07-98
February 2, 2008
Charged Higgs boson phenomenology
in Supersymmetric models with Higgs triplets
8
0
0 J. L. D´ıaz-Cruz,1, J. Hern´andez–S´anchez,2, S. Moretti,3, and A. Rosado4,
∗ † ‡ §
2
1Fac. de Cs. F´ısico-Matema´ticas, BUAP. Apdo. Postal 1364, C.P. 72000 Puebla,
n
a
Pue., M´exico and Dual C-P Institute of High Energy Physics, M´exico.
J

3 2Centro de Investigacio´n en Matema´ticas, UAEH,

] Carr. Pachuca-Tulancingo Km. 4.5, C.P. 42184, Pachuca,
h
p Hgo., M´exico and Dual C-P Institute of High Energy Physics.
-
p 3 School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK
e
h and
[
Laboratoire de Physique Th´eorique, U. Paris-Sud and CNRS, F-91405 Orsay, France.

2
v 4 Instituto de F´ısica, BUAP. Apdo. Postal J-48, C.P. 72570 Puebla, Pue., M´exico.
9
6 (Dated: February 2, 2008)
1
4
We present a detailed study of the Higgs sector within an extension of the Minimal Su-
.
0
persymmetric Standard Model that includes one Complex Higgs Triplet (MSSM+1CHT).
1
7
The model spectrum includes three singly charged Higgs bosons as well as three CP-even
0
: (or scalar)andtwo CP-odd(or pseudoscalar)neutral Higgsbosons. We presentanapproxi-
v
i
X matedcalculationofthe one-loopradiativecorrectionsto the neutralCP-evenHiggsmasses
r (m ) and the couplings H0Z0Z0 (i = 1, 2, 3), which determine the magnitude of the
a Hi0 i
Higgs-strahlung processes e+e− Z0H0. Limits from LEP2 are then considered, in order
→ i
to obtain bounds on the neutral Higgs sector. Further, we also include the experimental
limits from LEP2 on e+e− H+H− and those on BR(t bH+) from Tevatron, to derive
→ →
± ±
boundsonthemassofthe twolightestchargedHiggsbosons(H andH ). Concerningthe
1 2
latter,wefindsomecases,wheremH1± ≃90GeV,thatarenotexcludedbyanyexperimental
bound, evenfor largevalues oftanβ, so thatthey shouldbe lookedfor atthe LargeHadron
Collider (LHC).
PACS numbers: 12.60.Cn,12.60.Fr,11.30.Er
∗Electronic address: [email protected]
2
I. INTRODUCTION
The Higgs spectrum of many well motivated extensions of the Standard Model (SM) often
include charged Higgs bosons whose detection at future colliders would constitute a clear evidence
of a Higgs sector beyond that of the Standard Model (SM) [1]. In particular, the 2-Higgs-Doublet-
Model (2HDM, hereafter, of Type II), in both its Supersymmetric(SUSY) and non-SUSY versions
[2], has been extensively studied as a prototype of a Higgs sector that includes one charged Higgs
boson pair (H ), whose detection is expected to take place at the LHC [3]. However, a definitive
±
test of the mechanism of Electro-Weak Symmetry Breaking (EWSB) will require further studies
aiming at pinning down the underlying complete Higgs spectrum. In particular, probing the
properties of charged Higgs bosons could help to find out whether they are indeed associated with
a weakly-interacting theory, as in the case of the most popular SUSY extension of the SM, the
so-called Minimal Supersymmetric Standard Model (MSSM) [4], or with a strongly-interacting
scenario, like the ones discussed recently [5]. Ultimately, while many analyses in this direction can
becarried outattheLHC,itwillbeafutureInternationalLinearCollider(ILC)sayingthedefinite
word about which mechanism leads to mass generation. Notice that these tests should also allow
one to probe the symmetries of the Higgs potential and to determine whether the charged Higgs
bosons belong to a weak doublet or to some larger multiplet. Among the latter, in particular,
Higgs triplets have been considered [6], mainly to search for possible manifestations of an explicit
breaking of the custodial SU(2) symmetry, which keeps Veltman’s so-called ‘rho parameter’ close
c
to one, i.e. ρ 1. Motivations to discuss Higgs triplets can also be drawn from models of neutrino
≃
masses [7]as wellas scenarios withextra spacial dimensions[8]. Thoughmostof thework hasbeen
within non-SUSY models [9], there have also been studies of SUSY scenarios with complex Higgs
triplets, such as in [10], where some phenomenological aspects of the Higgs sector were explored.
Subsequent work in this model has been done in [11].
Decays of charged Higgs bosons have been studied in the literature [12], including the radia-
tive modes W γ,W Z0 [13], mostly within the context of the 2HDM or its MSSM incarnation
± ±
(including into SUSY particles [14]), but also for the effective Lagrangian extension of the 2HDM
definedin[15]andmorerecently withinanextension oftheMSSMwithoneComplex Higgs Triplet
(MSSM+1CHT) [16]. All these activities are particularly relevant especially in view of the fact
†Electronic address: [email protected]
‡Electronic address: [email protected]
§Electronic address: [email protected]
3
that charged Higgs boson decays can be exploited to determine key parameters of the underlying
Higgs sector [17]. Charged Higgs boson production at hadron colliders was studied long ago [18]
and, more recently, systematic calculations of production processes at the upcoming LHC have
been presented [19], including some higher order effects in QCD and SUSY QCD [20]. Current
bounds on the mass of the charged Higgs bosons have been obtained at Tevatron, by studying the
top decay t bH+, which already eliminates some regions of the 2HDM and MSSM parameter
→
spaces [21], whereas LEP2 gives a model independent bound of m > 80 GeV [22, 23].
H±
In this paper we present a detailed study of the spectrum and discuss the phenomenology of
the Higgs sector of the MSSM+1CHT model, i.e., the scenario that includes one complex Higgs
triplet in addition to the usual MSSM Higgs content, namely two Higgs doublets. Our main focus
will eventually be on the production and decay phenomenology of the charged Higgs states of the
model.
This article is organized as follows. In section II, we discuss the Higgs sector of this model, in
particular, we presentthecharged Higgs bosonspectrumand theinclusion of an estimated calcula-
tion of the one-loop radiative corrections for the CP-even neutral Higgs sector. In this section, we
also present a study of the couplings H0Z0Z0, which are modified by radiative corrections. Then,
i
in section III, we derive the expressions for the vertex H ff (where f and f are generic fermions
± ′ ′
withcumulative electromagnetic charge 1)andwecalculate thedecay t H+bintheframework
± → i
of the MSSM+1CHT model, also presenting numerical results for the most relevant charged Higgs
Branching Ratios (BR’s)1. (A comparison with latest bounds from Tevatron Run2 is also given
therein.) A discussion of the main production mechanism at the LHC is presented in section IV.
LHC event rates are given in section V. Finally, we summarize and conclude in section VI.
II. THE CHARGED HIGGS SPECTRUM IN A SUSY MODEL WITH AN
ADDITIONAL COMPLEX HIGGS TRIPLET
The SUSY model with two doublets and a complex Higgs triplet (MSSM+1CHT) of [10] is one
of the simplest extensions of the MSSM that allows one to study phenomenological consequences
of an explicit breaking of the custodial SU(2) symmetry [10, 11]. In the reminder of this section,
c
we recap its main theoretical features.
1 In the framework of the MSSM+1CHT the three charged Higgs states are denoted by H± with the convention:
i
mH1± <mH2± <mH3±.
4
A. The Higgs potential of the model
The MSSM+1CHT model includes two Higgs doublets and a complex Higgs triplet given by
φ 0 φ + 1ξ0 ξ+
Φ1 =  1  , Φ2 =  2  , =  q2 − 2  . (1)
 φ1−   φ20  X  ξ1− −q12ξ0 
The Higgs triplet, of zero hypercharge, is described in terms of a 2 2 matrix representation: ξ0 is
×
the complex neutral field and ξ , ξ+ denote the charged fields. The most general gauge invariant
1− 2
andrenormalizableSuperpotentialthatcan bewritten fortheHiggs SuperfieldsΦ andΣisgiven
1,2
by:
W = λΦ ΣΦ +µ Φ Φ +µ Tr(Σ2) , (2)
1 2 1 1 2 2
· ·
where we have used the notation Φ Φ ǫ ΦaΦb. The resulting scalar potential involving only
1· 2 ≡ ab 1 2
the Higgs fields is thus written as
V = V +V +V ,
SB F D
where V denotes the most general soft-Supersymmetry breaking potential, which is given by
SB
V = m2 Φ 2+m2 Φ 2+m2Tr(Σ Σ)
SB 1| 1| 2| 2| 3 †
+ [AλΦ ΣΦ +B µ Φ Φ +B µ Tr(Σ2)+h.c.], (3)
1 2 1 1 1 2 2 2
· ·
V is the SUSY potential from F-terms
F
2 2
1 1
V = µ φ0+λ φ+ξ φ0ξ0 + µ φ0+λ φ ξ+ φ0ξ0
F (cid:12) 1 2 (cid:18) 2 1−− √2 2 (cid:19)(cid:12) (cid:12) 1 1 (cid:18) −1 2 − √2 1 (cid:19)(cid:12)
(cid:12) (cid:12) (cid:12) (cid:12)
(cid:12) (cid:12)2 (cid:12) (cid:12) 2
+ (cid:12)µ φ++λ 1 φ+ξ0 φ0ξ+ (cid:12) +(cid:12)µ φ +λ 1 φ ξ0 φ0ξ (cid:12)
(cid:12) 1 2 (cid:18)√2 2 − 2 2 (cid:19)(cid:12) (cid:12) 1 −1 (cid:18)√2 −1 − 1 1−(cid:19)(cid:12)
(cid:12) (cid:12) (cid:12) (cid:12)
(cid:12) (cid:12)2 (cid:12) 2 (cid:12) 2
+ (cid:12)2µ ξ0 λ φ0φ0+φ φ+ (cid:12) + (cid:12)λφ0φ+ 2µ ξ+ + λφ φ0 (cid:12)2µ ξ , (4)
(cid:12) 2 − √2(cid:18) 1 2 −1 2(cid:19)(cid:12) (cid:12) 1 2 − 2 2 (cid:12) (cid:12) −1 2− 2 1−(cid:12)
(cid:12) (cid:12) (cid:12) (cid:12) (cid:12) (cid:12)
(cid:12) (cid:12) (cid:12) (cid:12) (cid:12) (cid:12)
(cid:12) (cid:12) (cid:12) (cid:12) (cid:12) (cid:12)
V is the SUSY potential from D-terms
D
g2 2
V = φ0 2 φ 2+ φ+ 2 φ0 2+2ξ+ 2 2ξ 2
D 8 (cid:20)| 1| −| −1| | 2| −| 2| | 2 | − | 1−| (cid:21)
g′2 2
+ φ0 2+ φ 2 φ+ 2 φ0 2
8 (cid:20)| 1| | −1| −| 2| −| 2| (cid:21)
g2 2
+ φ0 φ +φ+ φ0+√2(ξ+ +ξ )ξ0 +h.c.
8 (cid:20) 1∗ −1 2∗ 2 2 1− ∗ (cid:21)
g2 2
φ φ0+φ0 φ++√2(ξ+ ξ )ξ0 h.c. . (5)
− 8 (cid:20) −1∗ 1 2∗ 2 2 − 1− ∗− (cid:21)
5
In turn, the full scalar potential can be split into its neutral and charged parts, i.e., V = V +
charged
V [10, 11].
neutral
Besides the Supersymmetry-breaking mass terms, m2 (i = 1, 2, 3), the potential depends on
i
the parameters λ, µ , µ , that appear in Eq. (2), as well as the trilinear and bilinear terms, A
1 2
and B , respectively. For simplicity, we will assume that there is no CP violation in the Higgs
i
sector and thus all the parameters and Vacuum Expectations Values (VEVs) are assumed to be
real. In the charged Higgs sector with the basis of states (φ+, φ , ξ+, ξ ) one has a 4 4
2 −1∗ 2 2−∗ ×
squared-matrix mass (M2) , i = j = 1, ...4. For the CP-odd Higgs sector with the basis of states
ij
±
( 1 Imφ0, 1 Imφ0, 1 Imξ0) one obtains a 3 3 squared-matrix mass (M2) , i = j = 1, 2, 3.
√2 1 √2 2 √2 × P ij
For the CP-even Higgs sector with the basis of states ( 1 Reφ0, 1 Reφ0, 1 Reξ0) one also has a
√2 1 √2 2 √2
3 3 squared-matrix mass (M2) , i = j = 1, 2, 3. The explicit expression of the resulting Higgs
× S ij
potential is given in Refs. [10, 11].
B. Parameters of the model and definition of scenarios
We can combine the VEVs of the doublet Higgs fields through the relation v2 v2 +v2 and
D ≡ 1 2
define tanβ v /v . Furthermore, the parameters v , v , m2 and m2 are related as follows:
≡ 2 1 D T W Z
m2 = 1g2(v2 +4v2),
W 2 D T
1g2v2
m2 = 2 D ,
Z cos2θ
W
which implies that the ρ-parameter is different from 1 at the tree level, namely,
M2 v
ρ W = 1+4R2, R T . (6)
≡ M2cos2θ ≡ v
Z W D
The bound on R is obtained from the ρ parameter measurement, which presently lies in the range
0.9993–1.0006, from the global fit reported in Refs. [6, 23]. Thus, one has R 0.012 and v 3
T
≤ ≤
GeV. We have taken into account this bound in our numerical analyses.
Thus, the Higgs sector of this model depends of the following parameters: (i) the gauge-
related parameters (g, g , v, R, tanβ); (ii) the Yukawa couplings (λ, µ , µ ) and (iii) the soft
′ 1 2
Supersymmetry-breaking parameters (A, B , B ). The gauge-related parameters can be replaced
1 2
by thequantities (G , α, m , ρ, tanβ). For the numericalanalysis toberealized in theremainder
F W
of this paper,wemustmake surethatthefollowing theoretical conditions of theMSSM+1CHTare
satisfied: (a) the global stability condition of the potential; (b) the necessary condition for having
a global minimum and (c) the positivity of the mass eigenvalues of the full spectrum of charged,
pseudoscalar and scalar Higgs bosons [10].
6
The parameter space analyzed here for the MSSM+1CHT is the same that was considered
before in the specialized literature [10, 16], namely, we consider characteristic values below their
perturbative limits. Small and large values of tanβ are both considered. Typical cases for A, B ,
1
B , µ and µ are used to define the following scenarios.
2 1 2
Scenario A. It is defined by considering B = µ = 0, B = A and µ = 100 GeV while for λ
1 1 2 2
−
we shall consider the values λ = 0.1, 0.5, 1.0. In this scenario it happens that the additional Higgs
triplet plays a significant role in EWSB.
Scenario B. This scenario is defined by choosing: B = µ = 0, B = A, while for λ we shall
2 2 1
−
consider again the values λ = 0.1, 0.5, 1.0. Most results will take µ = 200 GeV, though other
1
values (such as µ = 400,700 GeV) will also be considered. Here, the effects of the additional
1
Higgs triplet are smaller, hence the behaviour of the model is similar to that of the MSSM.
C. One-loop radiative corrections to the CP-even Higgs bosons masses in the
MSSM+1CHT
Insomecases, withintheScenariosAandB,wewillshowthataverylightCP-evenHiggsboson
appears at the tree level, with a mass around 10 GeV, which can even be as small as (0.1) GeV.
O
However, it is known that, in the MSSM, the inclusion of radiative corrections from top and stop
loops can alter significantly the (lightest) neutral CP-even Higgs mass. Thus, we can expect that
similar effects will appear here and, furthermore, one also needs to consider in the MSSM+1CHT
a possible large correction from Higgs-chargino loops, which could lift the corresponding Higgs
mass above current experimental bounds. This means that one needs to include all such radiative
correctionsinordertoavoidmisleadingconclusions. Wearealsointerestedindiscussingtheneutral
Higgs bosons masses here because of their possible appearance in charged Higgs boson decays. As
it will be shown later, this effect is important for large regions of the MSSM+1CHT parameter
space.
The radiative corrections to Supersymmetric Higgs boson masses can be evaluated using the
effective potential technique [24], which at one-loop reads:
V (Q)= V (Q)+∆V (Q), (7)
1 0 1
1 M2 3
∆V (Q) = StrM4(log ), (8)
1 64π2 Q2 − 2
where V (Q) is the tree-level potential evaluated with couplings renormalized at some scale Q,
0
7
Str denotes the conventional Supertrace and M2 is the mass matrix for the CP-even sector. As
discussed in [24], the radiatively-corrected Higgs mass-squared matrix is given by the matrix of
the second derivatives of V with respect to the Higgs fields, which is written as a function of their
1
self-energies. In the MSSM, we know that the most important contributions to the Higgs self-
energies at the one-loop level come from the diagrams with the top quark (and its scalar partner)
circulating in the loop, due to the large top Yukawa coupling. However, for very large values of
tanβ, the bottom-sbottom contributions can become non-negligible. Therefore, for our settings,
the dominant contributions to the Supertrace in the MSSM+1CHT are due to the top-stop and
bottom-sbottom loops. Within this approximation, it happens that the squared-mass matrix of
the CP-even Higgs bosons only gets corrected along its (1,1) and (2,2) elements, given as follows:
3 m4
(∆M2) = λ2m2log ˜b,
S 1,1 8π2 b b m4
b
3 m4
(∆M2) = λ2m2log t˜, (9)
S 2,2 8π2 t t m4
t
where λ are the Yukawa couplings and the D-terms are omitted. In short, in the MSSM+1CHT,
t,b
the radiative corrections to the Higgs boson masses must include the dominant contribution from
the top-stop and bottom-sbottom systems. For this, it is enough to suitably modify the elements
(∆M2) , (∆M2) to the squared-mass matrix M2 of the CP-even Higgs boson. Furthermore,
S 1,1 S 2,2 S
as intimated already, we must also evaluate the contribution from the fermionic partner of the
Higgs Superfields, which includes the Higgs-Higgsino triplets, because there is a potentially large
effect emerging in the calculation of the squared-mass matrix of the CP-even Higgs bosons when
the parameter λ is large. Similarly to the top-stop and bottom-sbottom corrections, we estimate
that the correction from the Higgs-Higgsino only modifies the element (M2)
S 3,3
(∆M2) = 3 λ2m2 logm4χ± , (10)
S 3,3 8π2 χ± m4
H±
where λ is the Yukawa coupling that appears in the Superpotential of the Higgs Superfields and
– within our approximation – we take m and m as the mass scales of the lightest charginos
χ± H±
and charged Higgs bosons, respectively, i.e., m m and m m . D-terms are omitted,
χ± ≃ χ±1 H± ≃ H1±
as well as possible effects from stop, sbottom and Higgsino mixing. Previous studies of Higgs mass
bounds of this model were considered by J. R. Espinosa and M. Quir´os [25], who concluded that
the lightest Higgs boson of the model satisfy the bound,
m < m cos2(2β)+1/2(λ2v2/m2)sin2(2β). (11)
H10 ∼ Zq Z
8
Thus,forvalues ofλthatareconsistentwithperturbativity, wichthenimpliesaboundof theorder
m < 155 GeV. Throughout this paper we take values of λ that do not saturate this bound. A
H0
1 ∼
morecomplete calculation of theradiative corrections at one-loop level for this modelis in progress
[26].
Themain consequenceoftheseradiative corrections isthatthelightest CP-even Higgs masscan
beenhancedatsuchlevelsthatitmakesitpossibletopasscurrentexperimentalboundsfromLEP2.
Besides, the radiative corrections affect mainly the neutral Higgs bosons sector, in particular the
production of the neutral scalar Higgs in e+e collisions, which is the Higgs-strahlung processes
−
e+e H0Z0, whose cross sections can be expressed in terms of the SM Higgs boson (herein
− → i
denoted by φ0 ) production formula and the Higgs-Z0Z0 coupling, as follows [27]:
SM
σ = R2 σSM ,
Hi0Z Hi0Z0Z0 Hi0Z
g2
R2 = Hi0Z0Z0 , (12)
Hi0Z0Z0 gφ20 Z0Z0
SM
where g2 is the coupling H0Z0Z0 in the MSSM+1CHT and g2 is the SM coupling
H0Z0Z0 i φ0 Z0Z0
i SM
φ0 Z0Z0, which obey the relation
SM
3
g2 = g2 . (13)
H0Z0Z0 φ0 Z0Z0
Xi=1 i SM
In particular, for our model the factor R2 is given by:
H0Z0Z0
i
R2 = (VSc +VSs )2, (14)
H0Z0Z0 1i β 2i β
i
where VS denote the ij-elements of the rotation matrix for the CP-even neutral sector, which
ij
relates the physical states H0 and the real part of the fields φ0, φ0, ξ0 in the following way:
i 1 2
1 φ0 VS VS VS H0
√2 1 11 12 13 1
    
1 φ0 = VS VS VS H0 , (15)
 √2 2   21 22 23  2 
 1 ξ0  VS VS VS H0 
 √2   31 32 33  3 
where the VS are modified by the one-loop radiative corrections to the CP-even sector of our
ij
model. For our numerical analysis of the Higgs mass spectrum in the MSSM+1CHT we consider
the experimental limits on the charged Higgs mass from LEP2 and apply it to the lightest charged
Higgs state H [22, 23]. Theboundson theneutral Higgs bosonsH0, H0 are expressed in terms of
1± 1 2
the LEP2 bounds for R2 [27]. We will show that this excludes large regions of the parameter
H0Z0Z0
i
space of the MSSM+1CHT model. This is summarized in Tables I–IV. Herein, we define as the
9
“marginal regions” those cases that almost pass LEP2 bounds on the neutral Higgs, i.e., when
m 110 GeV and/or R2 are not consistent with experimental bounds but for which
H10,2 ∼ H10,2Z0Z0
we expect that the complete calculation of the one-loop radiative corrections to the mass of the
neutral Higgs boson in question could enhance its mass, thereby allowing it to eventually pass said
experimental limits.
D. Higgs masses: numerical results
Let us consider first Scenario A. Figures 1, 2 and 3(4, 5 and 6) show the results for
charged(neutral) Higgs bosons masses as a function of tanβ, in the range 1 tanβ 100,
≤ ≤
for the cases λ = 0.1, 0.5, 1.0, while taking A = 200, 300, 400 GeV, respectively. Throughout
this paper we shall assume that the numerical values for stop and sbottom masses, taken at the
electroweak scale, are degenerated. The above results for charged Higgs massed is based on the
tree-level analysis. Similarly, the coming results for the pseudoscalar masses is also based on the
tree-level formulae. However, the masses of the neutral CP-even Higgs bosons is based in the
previous discussion of one-loop radiative corrections to the Higgs masses. For the stop, sbottom
and chargino masses we take as input the value m = 1 TeV. In Figure 1 we present the charged
Higgs boson masses for λ = 0.1. We can see that the lightest charged Higgs boson has a mass
m < m , which is not below the theoretical limit that one obtains in the MSSM. Similarly,
H± W±
1 ∼
Figure 2 shows the charged Higgs boson masses for the case λ = 0.5, and again we have that
m < m is possible but only for large tanβ. Furthermore, here it is possible for both H and
H± W± 1±
1 ∼
H to be lighter than the top quark. Figure 3 shows the charged Higgs boson masses for the case
2±
λ = 1: now the lightest charged Higgs boson has a mass in the range 100 GeV <m < 200 GeV.
H±
1
Figure 4 shows the neutral Higgs spectrum for the case λ = 0.1, and we notice the presence of a
light CP-even Higgs boson with 11 GeV < m < 50 GeV, especially for low values of tanβ ( 5),
H10 ≤
that at first sight it would seem excluded by the LEP2 experimental limits. In fact, when one
compares the results for R2 obtained for this model , which measures the strength of the
H0Z0Z0
1
Higgs-strahlung process, with the LEP2 bounds [27], which require it to be less than 0.01, we
conclude that this scenario is indeed excluded, as it is summarized in our Table I. We assume that
the lightest neutral Higgs boson decays predominantly into b¯b mode. Similarly, Figure 5 considers
the case λ = 0.5, and again we find 11 GeV < m < 50 GeV for 1 tanβ 100. However, we
H10 ≤ ≤
find that, for tanβ 77, R2 is within the range allowed by LEP2. There is also a region
≤ H10Z0Z0
where 111 GeV < m < 114 GeV, which we identify as marginal. Finally, Figure 6 corresponds
H0
2
10
to the case λ = 1.0, and we find that 14 GeV < m < 89 GeV, for 15 tanβ and, although
H10 ≤
R2 < 0.01, again we find that this is a marginal region because 111 GeV < m < 114 GeV.
H10Z0Z0 H20
As a lesson from these figures, for the case λ = 0.5, we find that the LEP2 limit on the charged
Higgs mass allows cases where m < m , while the neutral Higgs bosons (chiefly H0) satisfy
H± W± 1
1 ∼
the experimental limits of LEP2. However, the case λ = 0.1 is not a favorable scenario, because
R does not satisfy the experimental bounds. In contrast, for λ = 1.0, the charged Higgs
H0Z0Z0
1
boson masses are significantly heavier. A complete list of bounds for all cases considered within
Scenario A is shown in Table I.
TABLE I: Analysis of R2 consistent with LEP. We consider experimental limits allowed by LEP2 for
Hi0Z0Z0
charged and neutral Higgs bosons, for Scenario A with A=200, 300, 400 GeV and µ2 =100 GeV.
λ=0.1 tanβ≤5 11GemVH<1±m≈H8101<Ge5V0GeV 0.15R<2 R2H10Z0<Z00<.80.8 ExcludedbyR2H10Z0Z0
111GeV<mH20 <118GeV H20Z0Z0
λ=0.5 tanβ≤77 791.28GGeeVV<<mmHH110±<<51018GGeVeV 0.0020.<9<R2HR102Z0Z0 <0.2 buAtlmloawregdinbaylfRor2HR10Z20Z0,
111GeV<mH0 <114GeV H20Z0Z0 H20Z0Z0
2
89GeV<mH1± <187GeV R2H0Z0Z0 <0.01 AllowedbyR2H0Z0Z0,
λ=1 15≤tanβ 14GeV<mH10 <89GeV 0.91<R2 butmarginalforR12
111GeV<mH20 <114GeV H20Z0Z0 H20Z0Z0
For Scenario B, Figures 7, 8 and 9(10, 11 and 12) show the charged(neutral) Higgs bosons
masses, as a function of tanβ in the range 1 tanβ 100, and for the cases λ = 0.1, 0.5, 1.0,
≤ ≤
taking A = 200, 300, 0.1 GeV, respectively. The lowest value (A = 0.1) is designed in order to get
charged Higgs masses below the top mass. Let us comment first the results found for the charged
Higgs mass in the case λ = 0.1, that appear in Figure 7. We can see that the lightest charged
Higgs boson has a mass above 300 GeV for A = 200, 300 GeV, while even for A = 0.1 GeV, it has
a mass above m , but it is still lighter than the top quark. Similarly, Figure 8 shows the charged
W±
Higgs boson masses for the case λ = 0.5. We find that, for A = 200, 300 GeV, m > 300 GeV,
H±
1
while, for A = 0.1 GeV, the mass is still in the range 100 GeV < m < m . In turn, Figure 9
H± t
1
shows the charged Higgs boson masses for λ = 1. Now, we have that the lightest charged Higgs
boson is heavier than the top quark, even for A= 0.1 GeV.
Let us now discuss the neutral Higgs spectrum. Figure 10 shows the case λ = 0.1 for A= 200,
300 GeV, where one finds that 60 GeV < m < 110 GeV, for 1 tanβ 100, but the region
H10 ≤ ≤
allowed by R2 corresponds to 10 tanβ, while the parameter area corresponding to m
H10Z0Z0 ≤ H10 ∼
110 GeV is of marginal type. Then, the case A = 0.1 GeV gives neutral Higgs masses within the