[Show abstract][Hide abstract] ABSTRACT: We show that the recently reported excess in resonant diboson production can
be explained in the context of non-custodial composite Higgs models. Dibosons
are generated via the s-channel exchange of massive vector bosons present in
these models. We discuss the compatibility of the signal excess with other
diboson experimental searches. We also discuss the tension between diboson
production and other experimental tests of the model that include electroweak
precision data, dilepton, dijet and top pair production and show that there is
a region of parameter space in which they are all compatible with the excess.
Journal of High Energy Physics 07/2015; 2015(9). DOI:10.1007/JHEP09(2015)186 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Gauge mediated supersymmetry breaking (GMSB) is an elegant mechanism to
transmit supersymmetry breaking from the hidden to the MSSM observable sector,
which solves the supersymmetric flavor problem. However the smallness of the
generated stop mixing requires superheavy stops to reproduce the experimental
value of the Higgs mass. Two possible ways out are: i) To extend GMSB by direct
superpotential messenger-MSSM Yukawa couplings to generate sizeable mixing,
thus reintroducing the flavor problem; ii) To extend the MSSM Higgs sector with
singlets and/or triplets providing extra tree-level corrections to the Higgs
mass. Singlets will not get any soft mass from GMSB and triplets will
contribute to the $\rho$ parameter which could be an issue. In this paper we
explore the second way by introducing extra supersymmetric triplets with
hypercharges $Y=(0,\pm 1)$, with a tree-level custodial $SU(2)_L\otimes
SU(2)_R$ global symmetry in the Higgs sector protecting the $\rho$ parameter: a
supersymmetric generalization of the Georgi-Machacek model, dubbed as
supersymmetric custodial triplet model (SCTM). The renormalization group
running from the messenger to the electroweak scale mildly breaks the custodial
symmetry. We will present realistic low-scale scenarios (with the NLSP being a
Bino-like neutralino or the right-handed stau) based on general (non-minimal)
gauge mediation and consistent with all present experimental data. Their main
features are: i) Light ($\sim 1$ TeV) stops; ii) Exotic couplings ($H^\pm W^\mp
Z$ and $H^{\pm\pm} W^\mp W^\mp$) absent in the MSSM and proportional to the
triplets VEV, $v_\Delta$; and, iii) A possible (measurable) universality
breaking of the Higgs couplings $\lambda_{WZ}=r_{WW}/r_{ZZ}\neq 1$.
Journal of High Energy Physics 05/2015; 2015(8). DOI:10.1007/JHEP08(2015)159 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper we explore extensions of the Minimal Supersymmetric Standard
Model involving two $SU(2)_L$ triplet chiral superfields that share a
superpotential Dirac mass yet only one of which couples to the Higgs fields.
This choice is motivated by recent work using two singlet superfields with the
same superpotential requirements. We find that, as in the singlet case, the
Higgs mass in the triplet extension can easily be raised to $125\,\text{GeV}$
without introducing large fine-tuning. For triplets that carry hypercharge, the
regions of least fine tuning are characterized by small contributions to the
$\mathcal T$ parameter, and light stop squarks, $m_{\tilde t_1} \sim
300-450\,\text{GeV}$; the latter is a result of the $\tan\beta$ dependence of
the triplet contribution to the Higgs mass. Despite such light stop masses,
these models are viable provided the stop-electroweakino spectrum is
sufficiently compressed.
Physical Review D 04/2015; 92(3). DOI:10.1103/PhysRevD.92.035009 · 4.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Supersymmetric Custodial Triplet Model (SCTM) adds to the particle
content of the MSSM three $SU(2)_L$ triplet chiral superfields with hypercharge
$Y=(0,\pm1)$. At the superpotential level the model respects a global $SU(2)_L
\otimes SU(2)_R$ symmetry only broken by the Yukawa interactions. The pattern
of vacuum expectation values of the neutral doublet and triplet scalar fields
depends on the symmetry pattern of the Higgs soft breaking masses. We study the
cases where this symmetry is maintained in the Higgs sector, and when it is
broken only by the two doublets attaining different vacuum expectation values.
In the former case, the symmetry is spontaneously broken down to the vectorial
subgroup $SU(2)_V$ and the $\rho$ parameter is protected by the custodial
symmetry. However in both situations the $\rho$ parameter is protected at tree
level, allowing for light triplet scalars with large vacuum expectation values.
We find that over a large range of parameter space, a light neutralino can
supply the correct relic abundance of dark matter either through resonant
s-channel triplet scalar funnels or well tempering of the Bino with the triplet
fermions. Direct detection experiments have trouble probing these model points
because the custodial symmetry suppresses the coupling of the neutralino and
the $Z$ and a small Higgsino component of the neutralino suppresses the
coupling with the Higgs. Likewise the annihilation cross sections for indirect
detection lie below the Fermi-LAT upper bounds for the different channels.
Physical Review D 04/2015; 92(1). DOI:10.1103/PhysRevD.92.015011 · 4.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper examines detection prospects and constraints on the chromomagnetic
dipole operator for the bottom quark. This operator has a flavor, chirality and
Lorentz structure that is distinct from other dimension six operators
considered in Higgs coupling studies. Its non-standard Lorentz structure
bolsters boosted $b \bar{b} h$ events, providing a rate independent signal of
new physics. To date, we find this operator is unconstrained by $p p
\rightarrow h + {\rm jets}$ and $pp \rightarrow \bar b b $ searches: for
order-one couplings the permitted cutoff $\Lambda$ for this operator can be as
low as $\Lambda \sim 1~{\rm TeV}$. We show how to improve this bound with
collider cuts that allow a $b$-tagged Higgs plus dijet search in the Higgs to
diphoton decay channel to exclude cutoffs as high as $\sim 6~{\rm TeV}$ at $2
\sigma$ with 3 $\text{ab}^{-1}$ of luminosity at the 14 TeV LHC. Cuts on the
$p_T$ of the Higgs are key to this search, because the chromomagnetic dipole
yields a non-standard fraction of boosted Higgses.
[Show abstract][Hide abstract] ABSTRACT: In this paper we present a new search technique for electroweakinos, the
superpartners of electroweak gauge and Higgs bosons, based on final states with
missing transverse energy, a photon, and a dilepton pair, $\ell^+\,\ell^- +
\gamma + \displaystyle{\not} E_T$. Unlike traditional electroweakino searches,
which perform best when $m_{\widetilde{\chi}^0_{2,3}} -
m_{\widetilde{\chi}^0_1}, m_{\widetilde{\chi}^{\pm}} - m_{\widetilde{\chi}^0_1}
> m_Z$, our search favors nearly degenerate spectra; degenerate electroweakinos
typically have a larger branching ratio to photons, and the cut $m_{\ell\ell}
\ll m_Z$ effectively removes on-shell Z boson backgrounds while retaining the
signal. This feature makes our technique optimal for `well-tempered' scenarios,
where the dark matter relic abundance is achieved with inter-electroweakino
splittings of $\sim 20 - 70\,\text{GeV}$. Additionally, our strategy applies to
a wider range of scenarios where the lightest neutralinos are almost
degenerate, but only make up a subdominant component of the dark matter -- a
spectrum we dub `well-forged'. Focusing on bino-Higgsino admixtures, we present
optimal cuts and expected efficiencies for several benchmark scenarios. We find
bino-Higgsino mixtures with $m_{\widetilde{\chi}^0_{2,3}} \lesssim
190\,\text{GeV}$ and $m_{\widetilde{\chi}^0_{2,3}} - m_{\widetilde{\chi}^0_1}
\cong 30\,\text{GeV}$ can be uncovered after roughly $600\,\text{fb}^{-1}$ of
luminosity at the 14 TeV LHC. Scenarios with lighter states require less data
for discovery, while scenarios with heavier states or larger mass splittings
are harder to discriminate from the background and require more data. Unlike
many searches for supersymmetry, electroweakino searches are one area where the
high luminosity of the next LHC run, rather than the increased energy, is
crucial for discovery.
Physical Review D 08/2014; 90(9). DOI:10.1103/PhysRevD.90.095008 · 4.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The recent discovery of a light CP-even Higgs in a region of masses
consistent with the predictions of models with low energy supersymmetry have
intensified the discussion of naturalness in these situations. The focus point
solution alleviates the MSSM fine tuning problem. In a previous work, we showed
the general form of the MSSM focus point solution, for different values of the
messenger scale and of the ratio of gaugino and scalar masses. Here we study
the possibility of inducing a light stop as a result of the renormalization
group running from high energies. This scenario is highly predictive and leads
to observables that may be constrained by future collider and flavor physics
data.
Physical Review D 06/2014; 90(3). DOI:10.1103/PhysRevD.90.035011 · 4.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present the general behavior of the scalar sector in a Three Higgs Doublet
Model (3HDM) with a $\mathbb{Z}_5$ flavor symmetry. There are regions of the
parameters space where it is possible to get a SM-like Higgs boson with the
other Higgs bosons being heavier, thus decoupled from the SM, and without
relevant contributions to any flavor observables. There are however other more
interesting regions of parameter space with a light charged Higgs ($m_{H^\pm}
\sim $ 150 GeV) that are consistent with experimental results and whose
phenomenological consequences could be interesting. We present a numerical
analysis of the main $B$-physics constraints and show that the model can
correctly describe the current experimental data.
[Show abstract][Hide abstract] ABSTRACT: In the wake of the Higgs discovery and over the long haul of the LHC run, one
should keep a lookout for kinematic anomalies in the most massive known trio of
coupled particles, $t \bar{t} h$. After surveying the scope of prior
constraints on chromomagnetic dipole and Higgs-gluon kinetic couplings, we
focus on surpluses of boosted-$p_T$ Higgs bosons fomented by these momentum
dependent dimension-six operators in $t \bar{t} h$ final states. We uncover a
number of simple, $p_T$ weighted angular variables useful for discriminating
Standard Model from dimension-6 boosted Higgs distributions, and make headway
arguing that one of these variables may improve the reach of existing Standard
Model top-Higgs searches. The approach we take is model independent, because we
just consider a set of effective operators that contribute to the same
three-body final state.
Physical Review D 02/2014; 89(9). DOI:10.1103/PhysRevD.89.093006 · 4.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The minimal supersymmetric extension of the Standard Model (SM) is a well
motivated scenario for physics beyond the SM, which allows a perturbative
description of the theory up to scales of the order of the Grand Unification
scale, where gauge couplings unify. The Higgs mass parameter is insensitive to
the ultraviolet physics and is only sensitive to the scale of soft
supersymmetry breaking parameters. Present collider bounds suggest that the
characteristic values of these parameters may be significantly larger than the
weak scale. Large values of the soft breaking parameters, however, induce large
radiative corrections to the Higgs mass parameter and therefore the proper
electroweak scale may only be obtained by a fine tuned cancellation between the
square of the holomorphic \mu-parameter and the Higgs supersymmetry breaking
square mass parameter. This can only be avoided if there is a correlation
between the scalar and gaugino mass parameters, such that the Higgs
supersymmetry breaking parameter remains of the order of the weak scale. The
scale at which this happens is dubbed as focus point. In this article, we
define the general conditions required for this to happen, for different values
of the messenger scale at which supersymmetry breaking is transmitted to the
observable sector, and for arbitrary boundary conditions of the sfermion,
gaugino, and Higgs mass parameters. Specific supersymmetry breaking scenarios
in which these correlations may occur are also discussed.
Journal of High Energy Physics 02/2014; 2014(4). DOI:10.1007/JHEP04(2014)093 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We will explore the consequences on the electroweak breaking condition, the
mass of supersymmetric partners and the scale at which supersymmetry is broken,
for arbitrary values of the supersymmetric parameters tan(beta) and the stop
mixing X_t, which follow from the Higgs discovery with a mass m_H\simeq 126 GeV
at the LHC. Within the present uncertainty on the top quark mass we deduce that
radiative breaking requires tan(beta) \gtrsim 7 for maximal mixing X_t\simeq
\sqrt{6}, and tan(beta) \gtrsim 20 for small mixing X_t\lesssim 1. The scale at
which supersymmetry is broken \mathcal M can be of order the unification or
Planck scale only for large values of tan(beta) and negligible mixing X_t\simeq
0. On the other hand for maximal mixing and large values of tan(beta)
supersymmetry should break at scales as low as \mathcal M\simeq 10^5 GeV. The
uncertainty in those predictions stemming from the uncertainty in the top quark
mass, i.e. the top Yukawa coupling, is small (large) for large (small) values
of tan(beta). In fact for tan(beta)=1 the uncertainty on the value of \mathcal
M is of several orders of magnitude.
Physical Review D 12/2013; 90(1). DOI:10.1103/PhysRevD.90.015016 · 4.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We study an extension of the minimal supersymmetric standard model with a
zero hypercharge triplet, and the effect that such a particle has on stop
decays. This model has the capability of predicting a 125.5 GeV Higgs even in
the presence of light stops and it can modify the diphoton rate by means of the
extra charged fermion triplet coupled to the Higgs. Working in the limit where
the scalar triplet decouples, and with small values of mA, we find that the
fermion triplet can greatly affect the branching ratios of the stops, even in
the absence of a direct stop-triplet coupling. We compare the triplet extension
with the MSSM and discuss how the additional fields affect the search for stop
pair production.
Journal of High Energy Physics 11/2013; 2014(1). DOI:10.1007/JHEP01(2014)177 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this short letter we show that the excess of events in the decay of Higgs
to two photons reported by ATLAS and CMS can be easily accommodated in a flavor
renormalizable three Higgs doublet model (3HDM). The model is consistent with
all fermion masses, mixing angles, and flavor changing neutral current
constraints.
Physics Letters B 07/2013; 725(1-3):97. DOI:10.1016/j.physletb.2013.06.047 · 6.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We study the implications at the LHC for the minimal (least) version of the
supersymmetric standard model. In this model supersymmetry is broken by gravity
and extra gauge interactions effects, providing a spectrum similar in several
aspects to that in natural supersymmetric scenarios. Having the first two
generations of sparticles partially decoupled means that any significant signal
can only involve gauginos and the third family of sfermions. In practice, the
signals are dominated by gluino production with subsequent decays into the stop
sector. As we show, for gluino masses below 2300 GeV, a discovery at the LHC is
possible at \sqrt{s}=14 TeV, but will require large integrated luminosities.
[Show abstract][Hide abstract] ABSTRACT: Extending the Higgs sector of the MSSM by triplets alleviates the little
hierarchy problem and naturally allows for enhancements in the diphoton decay
rate of the lightest CP-even Higgs h. In the present paper we analyze in detail
the Higgs phenomenology of this theory with m_h~126 GeV. We mostly focus on a
light Higgs sector where the pseudoscalar A, the next-to-lightest CP-even
scalar H and the charged H^\pm Higgses are naturally at the electroweak scale.
It turns out that for any value m_A > m_h there is a parameter region at small
tan(beta) where the CP-even Higgs sector appears at colliders as the SM one,
except for loop-induced corrections. Notably the existence of this SM-like
point, which is absent in the MSSM, is shared with supersymmetric theories
where there are extra singlets. We also highlight a second parameter region at
small m_A and small tan(beta) where the h signal strengths, diphoton channel
included, are SM-like except those of bottoms and taus which can have at most a
10-15 % splitting. Improvements in the A and H^\pm searches are worthwhile in
order to discriminate this scenario from the SM.
Journal of High Energy Physics 03/2013; 2013(7). DOI:10.1007/JHEP07(2013)054 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recent results on Higgs searches at the LHC point towards the existence of a
Higgs boson with mass of about 126 GeV whose diphoton decay rate tends to be
larger than in the Standard Model. These results are in tension with natural
MSSM scenarios: such a Higgs mass requires heavy (third-generation) squarks
which reintroduce some amount of fine-tuning and in general the Higgs diphoton
decay rate tends to follow the Standard Model result. In this paper we prove
that these problems can be alleviated by introducing an extra supersymmetric
triplet coupled to the Higgs in the superpotential. This superfield generates a
sizeable tree-level correction to the Higgs mass so that the third generation
is no longer required to be heavy, and its charged component enhances the
diphoton Higgs decay rates by as much as 50% with respect to the Standard Model
values. We also show that such a scenario is compatible with present
electroweak precision observables.
[Show abstract][Hide abstract] ABSTRACT: We study the implications at the LHC for a recent class of non-custodial
warped extra-dimensional models where the AdS_5 metric is modified near the
infrared brane. Such models allow for TeV Kaluza-Klein excitations without
conflict with electroweak precision tests. We discuss both the production of
electroweak and strong Kaluza-Klein gauge bosons. As we will show, only signals
involving the third generation of quarks seem to be feasible in order to probe
this scenario.
[Show abstract][Hide abstract] ABSTRACT: In this paper we embed the light stop scenario, a MSSM framework which
explains the baryon asymmetry of the universe through a strong first order
electroweak phase transition, in a top-down approach. The required low energy
spectrum consists in the light SM-like Higgs, the right-handed stop, the
gauginos and the Higgsinos while the remaining scalars are heavy. This spectrum
is naturally driven by renormalization group evolution starting from a heavy
scalar spectrum at high energies. The latter is obtained through a
supersymmetry-breaking mix of gauge mediation, which provides the scalars
masses by new gauge interactions, and gravity mediation, which generates
gaugino and Higgsino masses. This supersymmetry breaking also explains the \mu\
and B_\mu\ parameters necessary for electroweak breaking and predicts small
tri-linear mixing terms A_t in agreement with electroweak baryogenesis
requirements. The minimal embedding predicts a Higgs mass around its
experimental lower bound and by a small extension higher masses m_H\lesssim 127
GeV can be accommodated.
Journal of High Energy Physics 01/2012; 2012(4). DOI:10.1007/JHEP04(2012)137 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The LHC is putting bounds on the Higgs boson mass. In this Letter we use those bounds to constrain the minimal supersymmetric standard model (MSSM) parameter space using the fact that, in supersymmetry, the Higgs mass is a function of the masses of sparticles, and therefore an upper bound on the Higgs mass translates into an upper bound for the masses for superpartners. We show that, although current bounds do not constrain the MSSM parameter space from above, once the Higgs mass bound improves big regions of this parameter space will be excluded, putting upper bounds on supersymmetry (SUSY) masses. On the other hand, for the case of split-SUSY we show that, for moderate or large tanβ, the present bounds on the Higgs mass imply that the common mass for scalars cannot be greater than 10(11) GeV. We show how these bounds will evolve as LHC continues to improve the limits on the Higgs mass.
[Show abstract][Hide abstract] ABSTRACT: A generalization of the Next-to-Minimal Supersymmetric Model (NMSSM) is
studied in which an explicit \mu-term as well as a small supersymmetric mass
term for the singlet superfield are incorporated. We study the possibility of
raising the Standard Model-like Higgs mass at tree level through its mixing
with a light, mostly-singlet, CP-even scalar. We are able to generate Higgs
boson masses up to 145 GeV with top squarks below 1.1 TeV and without the need
to fine tune parameters in the scalar potential. This model yields light
singlet-like scalars and pseudoscalars passing all collider constraints.
Physics Letters B 11/2011; 710(3). DOI:10.1016/j.physletb.2012.03.034 · 6.13 Impact Factor