Kaneko, S., Saito, H., Sato, J., Shimomura, T., Vives, O., & Yamanaka, M. (2011). Correlation between flavor-violating decay of long-lived slepton and tau in the coannihilation scenario with the seesaw mechanism. Phys. Rev. D, 83(11), 115005–10pp.
Abstract: We investigate flavor violating decays of the long-lived lightest slepton and the tau lepton in the coannihilation region of the minimal supersymmetric standard model with a seesaw mechanism to generate neutrino masses. We consider a situation where the mass difference between the lightest neutralino, as the lightest supersymmetric particle, and the lightest slepton, as the next-to-lightest supersymmetric particle, is smaller than the mass of tau lepton. In this situation, the lifetime of the lightest slepton is very long and it is determined by lepton flavor violating (LFV) couplings because the slepton mainly consists of the lighter stau and the flavor conserving 2-body decay is kinematically forbidden. We show that the lifetime can change many orders of magnitude by varying the Yukawa couplings entering the seesaw mechanism. We also show that the branching ratios of LFV tau decays are strongly correlated with the lightest slepton lifetime. Therefore the branching ratios of LFV tau decays can be determined or constrained by measuring the slepton lifetime at the LHC experiment.
|
Calibbi, L., Hodgkinson, R. N., Jones Perez, J., Masiero, A., & Vives, O. (2012). Flavour and collider interplay for SUSY at LHC7. Eur. Phys. J. C, 72(2), 1863–26pp.
Abstract: The current 7 TeV run of the LHC experiment shall be able to probe gluino and squark masses up to values larger than 1 TeV. Assuming that hints for SUSY are found in the jets plus missing energy channel by the end of a 5 fb(-1) run, we explore the flavour constraints on three models with a CMSSM-like spectrum: the CMSSM itself, a seesaw extension of the CMSSM, and Flavoured CMSSM. In particular, we focus on decays that might have been measured by the time the run is concluded, such as B-s -> μμand μ-> e gamma. We also analyse constraints imposed by neutral meson bounds and electric dipole moments. The interplay between collider and flavour experiments is explored through the use of three benchmark scenarios, finding the flavour feedback useful in order to determine the model parameters and to test the consistency of the different models.
|
Boubekeur, L., Dodelson, S., & Vives, O. (2012). Cold positrons from decaying dark matter. Phys. Rev. D, 86(10), 103520–14pp.
Abstract: Many models of dark matter contain more than one new particle beyond those in the Standard Model. Often, heavier particles decay into the lightest dark matter particle as the Universe evolves. Here, we explore the possibilities which arise if one of the products in a (heavy particle) -> (dark matter) decay is a positron, and the lifetime is shorter than the age of the Universe. The positrons cool down by scattering off the cosmic microwave background and eventually annihilate when they fall into Galactic potential wells. The resulting 511 keV flux not only places constraints on this class of models, but might even be consistent with that observed by the INTEGRAL satellite.
|
Barenboim, G., Bosch, C., Lopez-Ibañez, M. L., & Vives, O. (2014). Improved tau-lepton tools for Higgs boson hunting. Phys. Rev. D, 90(1), 015003–14pp.
Abstract: In this work, we use the results from Higgs searches in the gamma gamma and tau tau decay channels at LHC and indirect bounds as BR (B -> X-s gamma) to constrain the parameter space of a generic minimal supersymmetric standard model (MSSM) Higgs sector. In particular, we include the latest CMS results that look for additional Higgs states with masses up to 1 TeV. We show that the tau tau channel is the best and most accurate tool in the hunt for new Higgs states beyond the standard model. We obtain that present experimental results rule out additional neutral Higgs bosons in a generic MSSM below 300 GeV for any value of tan beta and, for instance, values of tan beta above 30 are only possible for Higgs masses above 600 GeV. ATLAS stored data have the potential to render this bound obsolete in the near future.
|
Barenboim, G., & Vives, O. (2015). Transplanckian inflation as gravity echoes. Phys. Lett. B, 748, 336–342.
Abstract: In this work, we show that, in the presence of non-minimal coupling to gravity, it is possible to generate sizeable tensor modes in single-field models without transplanckian field values. These transplanckian field values apparently needed in Einstein gravity to accommodate the experimental results may only be due to our insistence of imposing a minimal coupling of the inflaton field to gravity in a model with non-minimal couplings. We present three simple single-field models that prove that it is possible to accommodatea large tensor-to-scalar ratio without requiring transplanckian field values within the slow-roll regime.
|
Barenboim, G., Bosch, C., Lee, J. S., Lopez-Ibañez, M. L., & Vives, O. (2015). Flavor-changing Higgs boson decays into bottom and strange quarks in supersymmetric models. Phys. Rev. D, 92(9), 095017–15pp.
Abstract: In this work, we explore the flavor-changing decays H-i -> bs in a general supersymmetric scenario. In these models the flavor-changing decays arise at loop level, but-because they originate from a dimension-four operator-they do not decouple and may provide a first sign of new physics for heavy masses beyond the reach of colliders. In the framework of the minimal supersymmetric extension of the Standard Model, we find that the largest branching ratio of the lightest Higgs (H-1) is O(10(-6)) after imposing present experimental constraints, while heavy Higgs states may still present branching ratios O(10(-3)). In a more general supersymmetric scenario, where additional Higgs states may modify the Higgs mixings, the branching ratio BR(H-1 -> bs) can reach values O(10(-4)), while heavy Higgses still remain at O(10(-3)). Although these values are clearly out of reach for the LHC, a full study in a linear collider environment could be worth pursuing.
|
Barenboim, G., Bernabeu, J., Mitsou, V. A., Romero Adam, E., & Vives, O. (2016). METing SUSY on the Z peak. Eur. Phys. J. C, 76(2), 57–13pp.
Abstract: Recently the ATLAS experiment announced a 3 sigma excess at the Z-peak consisting of 29 pairs of leptons together with two or more jets, E-T(miss) > 225 GeV and H-T > 600 GeV, to be compared with 10.6 +/- 3.2 expected lepton pairs in the Standard Model. No excess outside the Z-peak was observed. By trying to explain this signal with SUSY we find that only relatively light gluinos, m((g) over bar) less than or similar to 1.2 TeV, together with a heavy neutralino NLSP of m((chi) over bar) greater than or similar to 400 GeV decaying predominantly to Z-boson plus a light gravitino, such that nearly every gluino produces at least one Z-boson in its decay chain, could reproduce the excess. We construct an explicit general gauge mediation model able to reproduce the observed signal overcoming all the experimental limits. Needless to say, more sophisticated models could also reproduce the signal, however, any model would have to exhibit the following features: light gluinos, or heavy particles with a strong production cross section, producing at least one Z-boson in its decay chain. The implications of our findings for the Run II at LHC with the scaling on the Z peak, as well as for the direct search of gluinos and other SUSY particles, are pointed out.
|
MoEDAL Collaboration(Acharya, B. et al), Bernabeu, J., Garcia, C., Mamuzic, J., Mitsou, V. A., Ruiz de Austri, R., et al. (2017). Search for Magnetic Monopoles with the MoEDAL Forward Trapping Detector in 13 TeV Proton-Proton Collisions at the LHC. Phys. Rev. Lett., 118(6), 061801–6pp.
Abstract: MoEDAL is designed to identify new physics in the form of long-lived highly ionizing particles produced in high-energy LHC collisions. Its arrays of plastic nuclear-track detectors and aluminium trapping volumes provide two independent passive detection techniques. We present here the results of a first search for magnetic monopole production in 13 TeV proton-proton collisions using the trapping technique, extending a previous publication with 8 TeV data during LHC Run 1. A total of 222 kg of MoEDAL trapping detector samples was exposed in the forward region and analyzed by searching for induced persistent currents after passage through a superconducting magnetometer. Magnetic charges exceeding half the Dirac charge are excluded in all samples and limits are placed for the first time on the production of magnetic monopoles in 13 TeV pp collisions. The search probes mass ranges previously inaccessible to collider experiments for up to five times the Dirac charge.
|
Das, D., Lopez-Ibañez, M. L., Jay Perez, M., & Vives, O. (2017). Effective theories of flavor and the nonuniversal MSSM. Phys. Rev. D, 95(3), 035001–16pp.
Abstract: Flavor symmetries a la Froggatt-Nielsen provide a compelling way to explain the hierarchies of fermionic masses and mixing angles in the Yukawa sector. In supersymmetric (SUSY) extensions of the Standard Model where the mediation of SUSY breaking occurs at scales larger than the breaking of flavor, this symmetry must be respected not only by the Yukawas of the superpotential but also by the soft-breaking masses and trilinear terms. In this work we show that contrary to naive expectations, even starting with completely flavor blind soft breaking in the full theory at high scales, the low-energy sfermion mass matrices and trilinear terms of the effective theory, obtained upon integrating out the heavy mediator fields, are strongly nonuniversal. We explore the phenomenology of these SUSY flavor models after the latest LHC searches for new physics.
|
Bhattacharyya, G., Das, D., Jay Perez, M., Saha, I., Santamaria, A., & Vives, O. (2018). Can measurements of 2HDM parameters provide hints for high scale supersymmetry? Phys. Rev. D, 97(9), 095018–9pp.
Abstract: Two-Higgs-doublet models (2HDMs) arc minimal extensions of the Standard Model (SM) that may still be discovered at the LHC. The quartic couplings of their potentials can be determined from the measurement of the masses and branching ratios of their extended scalar sectors. We show that the evolution of these couplings through renormalization group equations can determine whether the observed 2HDM is a low energy manifestation of a more fundamental theory, as for instance, supersymmetry, which fixes the quartic couplings in terms of the gauge couplings. At leading order, the minimal supersymmetric extension of the SM (MSSM) dictates all the quartic couplings, which can be translated into a predictive structure for the scalar masses and mixings at the weak scale. Running these couplings to higher scales, one can check if they converge to their MSSM values, and more interestingly, whether one can infer the supersymmetry breaking scale. Although we study this question in the context of supersymmetry, this strategy could be applied to any theory whose ultraviolet completion unambiguously predicts all scalar quartic couplings.
|
