Publications (66)298.07 Total impact
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ABSTRACT: We examine the `diboson' excess at $\sim 2$ TeV seen by the LHC experiments in various channels. We provide a comparison of the excess significances as a function of the mass of the tentative resonance and give the signal cross sections needed to explain the excesses. We also present a survey of available theoretical explanations of the resonance, classified in three main approaches. Beyond that, we discuss methods to verify the anomaly, determining the major properties of the various surpluses and exploring how different models can be discriminated. Finally, we give a tabular summary of the numerous explanations, presenting their main phenomenological features. 
Article: Gauge mediation with light stops
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ABSTRACT: The mechanism of gauge mediated supersymmetry breaking (GMSB) solves the supersymmetric flavor problem although it requires superheavy stops to reproduce the experimental value (125 GeV) of the Higgs mass. A possible way out is to extend the MSSM Higgs sector with triplets which provide extra treelevel corrections to the Higgs mass. Triplets with neutral components getting vacuum expectation values (VEV) have the problem of generating a treelevel correction to the \rho parameter. We introduce supersymmetric triplets with hypercharges Y=(0,\pm 1), with a treelevel custodial SU(2)_L\otimes SU(2)_R global symmetry in the Higgs sector protecting the \rho parameter: a supersymmetric generalization of the GeorgiMachacek model. The renormalization group running from the messenger to the electroweak scale mildly breaks the custodial symmetry. We will present realistic lowscale scenarios, their main features being a Binolike neutralino or righthanded stau as the NLSP, light (1 TeV) stops, exotic couplings (H^\pm W^\mp Z and H^{\pm\pm} W^\mp W^\mp) absent in the MSSM and proportional to the triplet VEV, and a possible (measurable) universality breaking of the Higgs couplings \lambda_{WZ}= \left(g_{hWW}/g_{hWW}^{SM}\right)/ \left(g_{hZZ}/g_{hZZ}^{SM}\right)\neq 1.  [Show abstract] [Hide abstract]
ABSTRACT: We show that the recently reported excess in resonant diboson production can be explained in the context of noncustodial composite Higgs models. Dibosons are generated via the schannel 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. 
Article: Detecting underabundant neutralinos
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ABSTRACT: The electroweak sector may play a crucial role in discovering supersymmetry. We systematically investigate the patterns of the MSSMlike electroweakinos, when the neutralino relic abundance Ωχh 2 ≤ 0.12, that is, also admitting for multicomponent Dark Matter, in a broad range of the parameter space. We find that for a very large range of parameters the Direct Detection experiments are/will be sensitive to underabundant neutralinos, in spite of the strong rescaling of the flux factor. The second general conclusion is that the bound Ωχh 2 ≤ 0.12 together with the LUX (XENON1T) limits for the neutralino spin independent scattering cross sections constrain the electroweakino spectrum so that the mass differences between the NLSP and the LSP are smaller than 40 (10) GeV, respectively, with important implications for the collider searches. The future Direct Detection experiments and the high luminosity LHC run will probe almost the entire range of the LSP and NLSP mass spectrum that is consistent with the bound Ωχh 2 ≤ 0.12. 
Article: GMSB with light stops
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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 messengerMSSM 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 treelevel 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 treelevel custodial $SU(2)_L\otimes SU(2)_R$ global symmetry in the Higgs sector protecting the $\rho$ parameter: a supersymmetric generalization of the GeorgiMachacek 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 lowscale scenarios (with the NLSP being a Binolike neutralino or the righthanded stau) based on general (nonminimal) 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 $\lambda_{WZ}=r_{WW}/r_{ZZ}\neq 1$. 
Article: Dirac triplet extension of the MSSM
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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 finetuning. 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, $m_{\tilde t_1} \sim 300450\,\text{GeV}$; 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 stopelectroweakino spectrum is sufficiently compressed.  [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 schannel 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 FermiLAT upper bounds for the different channels.  [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 nonstandard 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 orderone 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 nonstandard 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 onshell Z boson backgrounds while retaining the signal. This feature makes our technique optimal for `welltempered' scenarios, where the dark matter relic abundance is achieved with interelectroweakino 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 `wellforged'. Focusing on binoHiggsino admixtures, we present optimal cuts and expected efficiencies for several benchmark scenarios. We find binoHiggsino 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.  [Show abstract] [Hide abstract]
ABSTRACT: The recent discovery of a light CPeven 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.  [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 SMlike 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 Higgsgluon kinetic couplings, we focus on surpluses of boosted$p_T$ Higgs bosons fomented by these momentum dependent dimensionsix 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 dimension6 boosted Higgs distributions, and make headway arguing that one of these variables may improve the reach of existing Standard Model topHiggs searches. The approach we take is model independent, because we just consider a set of effective operators that contribute to the same threebody final state. 
Article: General focus point in the MSSM
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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 \muparameter 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.  [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.  [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 stoptriplet coupling. We compare the triplet extension with the MSSM and discuss how the additional fields affect the search for stop pair production.  [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.  [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 CPeven 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 nexttolightest CPeven 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 CPeven Higgs sector appears at colliders as the SM one, except for loopinduced corrections. Notably the existence of this SMlike 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 SMlike except those of bottoms and taus which can have at most a 1015 % splitting. Improvements in the A and H^\pm searches are worthwhile in order to discriminate this scenario from the SM.  [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 (thirdgeneration) squarks which reintroduce some amount of finetuning 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 treelevel 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 noncustodial warped extradimensional models where the AdS_5 metric is modified near the infrared brane. Such models allow for TeV KaluzaKlein excitations without conflict with electroweak precision tests. We discuss both the production of electroweak and strong KaluzaKlein gauge bosons. As we will show, only signals involving the third generation of quarks seem to be feasible in order to probe this scenario.
Publication Stats
2k  Citations  
298.07  Total Impact Points  
Top Journals
Institutions

20082015

University of Notre Dame
 Department of Physics
South Bend, Indiana, United States


20052015

CERN
 Physics Department (PH)
Genève, Geneva, Switzerland


20022005

Johns Hopkins University
 Department of Physics and Astronomy
Baltimore, Maryland, United States


2001

Argonne National Laboratory
 Division of High Energy Physics
Lemont, Illinois, United States


19992001

Instituto de Estructura de la Materia
Madrid, Madrid, Spain
