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Ernesto Arganda

Publications and source records attributed to Ernesto Arganda.

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Potential discovery of staus through heavy Higgs boson decays at the LHC

In this work we present a new search strategy for the discovery of staus at the LHC in the context of the minimal supersymmetric standard model. The search profits from the large s-channel $b$-quark annihilation production of the heavy CP-even and CP-odd Higgs bosons (H/A) which can be attained in regions of $\tanβ\gg 1$ that avoid the stringent $H/A \to τ^+ τ^-$ searches via decays into stau pairs. We also focus on regions where the staus branching ratios are dominated by the decays into a tau lepton and the lightest neutralino. Thus the experimental signature consists of final states made up of a tau-lepton pair plus large missing transverse energy. We take advantage of the large stau-pair production cross sections via heavy Higgs boson decays, which are between one or two orders of magnitude larger than the usual electroweak production cross sections for staus. A set of basic cuts allow us to obtain significances of the signal over the SM backgrounds at the discovery level (5 standard deviations) in the next LHC run with a center-of-mass energy of 14 TeV and a total integrated luminosity of only 100 fb$^{-1}$.

hep-ph

Search strategies for pair production of heavy Higgs bosons decaying invisibly at the LHC

The search for heavy Higgs bosons at the LHC represents an intense experimental program, carried out by the ATLAS and CMS collaborations, which includes the hunt for invisible Higgs decays and dark matter candidates. No significant deviations from the SM backgrounds have been observed in any of these searches, imposing significant constraints on the parameter space of different new physics models with an extended Higgs sector. Here we discuss an alternative search strategy for heavy Higgs bosons decaying invisibly at the LHC, focusing on the pair production of a heavy scalar $H$ together with a pseudoscalar $A$, through the production mode $q \bar q \to Z^\ast \to HA$. We identify as the most promising signal the final state made up of $4b + E_T^\text{miss}$, coming from the heavy scalar decay mode $H \to hh \to b \bar b b \bar b$, with $h$ being the discovered SM-like Higgs boson with $m_h=125$ GeV, together with the invisible channel of the pseudoscalar. We work within the context of simplified MSSM scenarios that contain quite heavy sfermions of most types with ${\cal O}(10)$ TeV masses, while the stops are heavy enough to reproduce the 125 GeV mass for the lightest SM-like Higgs boson. By contrast, the gauginos/higgsinos and the heavy MSSM Higgs bosons have masses near the EW scale. Our search strategies, for a LHC center-of-mass energy of $\sqrt{s} =$ 14 TeV, allow us to obtain statistical significances of the signal over the SM backgrounds with values up to $\sim$ 1.6$σ$ and $\sim$ 3$σ$, for total integrated luminosities of 300 fb$^{-1}$ and 1000 fb$^{-1}$, respectively.

hep-ph

Higgs effective $Hl_il_j$ vertex from heavy $ν_R$ and applications to LFV phenomenology

We present a new computation of the Lepton Flavor Violating effective vertex involving the Higgs boson and two leptons with different flavors. This vertex is generated from the integration to one-loop level of the heavy right handed neutrinos which are considered here within the context of the Low Scale Seesaw Models and with masses close to the TeV scale. We apply the Mass Insertion Approximation technique to compute the loop contributions from these heavy $ν_R$ and derive a symple analytical formula for the $Hl_il_j$ effective vertex in terms of the input $Y_ν$ Yukawa coupling matrix and right handed $M_R$ neutrino masses. Some interesting phenomenological applications of this $Hl_il_j$ effective vertex are also included.

hep-ph

Remark on the one-loop Z form factors for LFV Z-penguin diagrams in SUSY

In this note we shortly comment on our analytical results in PRD73(2006)055003 for the $Z$ boson one-loop form factors contributing to the Lepton Flavour Violating $Z$ penguin diagrams in SUSY. In a recent communication [arXiv:1312.5318v1] it has been pointed out a mistake in our formulas for the chargino contribution to the $Z$-form factor, $F_L^{(c)}$, and these authors have included corrections to our results in a way that we do not agree with. We wish to clarify here what are the correct results for these form factors.

hep-ph

Slim SUSY

The new SM-like Higgs boson discovered recently at the LHC, with mass $m_h \simeq$ 125 GeV, as well as the direct LHC bounds on the mass of superpartners, which are entering into the TeV range, suggest that the minimal surviving supersymmetric extension of the SM (MSSM), should be characterized by a heavy SUSY-breaking scale. Several variants of the MSSM have been proposed to account for this result, which vary according to the accepted degree of fine-tuning. We propose an alternative scenario here, Slim SUSY, which contains sfermions with multi-TeV masses and gauginos/higgsinos near the EW scale, but it includes the heavy MSSM Higgs bosons ($H^0$, $A^0$, $H^\pm$) near the EW scale too. We discuss first the formulation and constraints of the Slim SUSY scenario, and then identify distinctive heavy Higgs signals that could be searched at the LHC, within scenarios with the minimal number of superpartners with masses near the EW scale.

hep-ph

Decays of $H^0/A^0$ in supersymmetric scenarios with heavy sfermions

The recent discovery of a new boson at the LHC, which resembles a SM-like Higgs boson with $m_h=125$ GeV, is starting to provide strong guidelines into SUSY model building. For instance, the identification of such a state with the lightest CP-even Higgs boson of the MSSM ($h^0$), requires large values of $\tanβ$ and/or heavy sfermions. One outcome of this result is the possibility to solve the SUSY flavor and CP problems by decoupling, which points towards some realization of Split-inspired SUSY scenarios, in which scalars are much heavier than gauginos and higgsinos. However, we argue here that the remaining Higgs bosons of the MSSM ($H^0$, $A^0$, $H^{\pm}$) do not have to be as heavy as the sfermions, and having them with masses near the EW scale does not pose any conflict with current MSSM constraints. We discuss then some SUSY scenarios with heavy sfermions, from a bottom-up approach, which contain the full Higgs sector, as well as a possible dark matter candidate, with masses near the EW scale, and identify distinctive signals from these scenarios that could be searched at the LHC.

hep-ph