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Aguilar-Saavedra J.A.,University of Granada | Juste A.,Catalan Institution for Research and Advanced Studies | Juste A.,Institute Of Fisica Daltes Energies Ifae | Rubbo F.,Institute Of Fisica Daltes Energies Ifae
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

We propose a kinematical enhancement of the tt̄ charge asymmetry at the LHC by selecting events with the tt̄ centre of mass frame highly boosted along the beam axis. This kinematical selection increases the asymmetries and their significance up to a factor of two in a rather model-independent fashion. Hence, it can be a perfect complement to enhance model discrimination at the LHC. © 2011 Elsevier B.V.

Nieves J.,University of Valencia | Sanchez F.,Institute Of Fisica Daltes Energies Ifae | Simo I.R.,University of Granada | Vacas M.J.V.,University of Valencia
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We show that because of the multinucleon mechanism effects, the algorithm used to reconstruct the neutrino energy is not adequate when dealing with quasielastic-like events, and a distortion of the total flux-unfolded cross-section shape is produced. This amounts to a redistribution of strength from high to low energies, which gives rise to a sizable excess (deficit) of low (high) energy neutrinos. This distortion of the shape leads to a good description of the MiniBooNE unfolded charged current quasielastic-like cross sections published by A.A. Aguilar-Arevalo [(MiniBooNE Collaboration), Phys. Rev. DPRVDAQ1550-7998 81, 092005 (2010)]10.1103/PhysRevD.81.092005. However, these changes in the shape are artifacts of the unfolding process that ignores multinucleon mechanisms. © 2012 American Physical Society.

Aguilar-Saavedra J.A.,University of Granada | Aguilar-Saavedra J.A.,CERN | Amidei D.,University of Michigan | Juste A.,Catalan Institution for Research and Advanced Studies | And 2 more authors.
Reviews of Modern Physics | Year: 2015

The asymmetries in top quark pair production at the Tevatron and the LHC are reviewed. The experimental measurements and the interpretations of a possible excess in terms of new physics are summarized. Other top quark properties are also reviewed, emphasizing effects related to the tt¯ asymmetries, as well as other collider signals. © 2015 American Physical Society.

Alberte L.,Abdus Salam International Center For Theoretical Physics | Baggioli M.,Institute Of Fisica Daltes Energies Ifae | Baggioli M.,Urbana University | Khmelnitsky A.,Abdus Salam International Center For Theoretical Physics | Pujolas O.,Institute Of Fisica Daltes Energies Ifae
Journal of High Energy Physics | Year: 2016

Abstract: Momentum dissipation is an important ingredient in condensed matter physics that requires a translation breaking sector. In the bottom-up gauge/gravity duality, this implies that the gravity dual is massive. We start here a systematic analysis of holographic massive gravity (HMG) theories, which admit field theory dual interpretations and which, therefore, might store interesting condensed matter applications. We show that there are many phases of HMG that are fully consistent effective field theories and which have been left overlooked in the literature. The most important distinction between the different HMG phases is that they can be clearly separated into solids and fluids. This can be done both at the level of the unbroken spacetime symmetries as well as concerning the elastic properties of the dual materials. We extract the modulus of rigidity of the solid HMG black brane solutions and show how it relates to the graviton mass term. We also consider the implications of the different HMGs on the electric response. We show that the types of response that can be consistently described within this framework is much wider than what is captured by the narrow class of models mostly considered so far. © 2016, The Author(s).

Gran R.,University of Minnesota | Nieves J.,University of Valencia | Sanchez F.,Institute Of Fisica Daltes Energies Ifae | Vacas M.J.V.,University of Valencia
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We extend to 10 GeV results from a microscopic calculation of charged-current neutrino-nucleus reactions that do not produce a pion in the final state. For the class of events coming from neutrino interactions with two nucleons producing two holes (2p2h), limiting the calculation to three-momentum transfers less than 1.2 GeV produces a two-dimensional distribution in momentum and energy transfer that is roughly constant as a function of energy. The cross section for 2p2h interactions approximately scales with the number of nucleons for isoscalar nuclei, similar to the quasi-elastic cross section. When limited to momentum transfers below 1.2 GeV, the cross section is 26% of the quasi-elastic cross section at 3 GeV, but 14% if we neglect a Δ1232 resonance absorption component. The same quantities are 33% and 17% for antineutrinos. For the quasi-elastic interactions, the full nuclear model with long range correlations produces an even larger, but approximately constant distortion of the shape of the four-momentum transfer at all energies above 2 GeV. The 2p2h enhancement and long-range correlation distortions to the cross section for these interactions are significant enough they should be observable in precision experiments to measure neutrino oscillations and neutrino interactions at these energies, but also balance out and produce less total distortion than each effect does individually. © 2013 American Physical Society.

Megias E.,Max Planck Institute for Physics | Pujolas O.,Institute Of Fisica Daltes Energies Ifae | Quiros M.,Institute Of Fisica Daltes Energies Ifae | Quiros M.,Catalan Institution for Research and Advanced Studies | Quiros M.,São Paulo State University
Journal of High Energy Physics | Year: 2016

We study soft wall models that can embed the Standard Model and a naturally light dilaton. Exploiting the full capabilities of these models we identify the parameter space that allows to pass Electroweak Precision Tests with a moderate Kaluza-Klein scale, around 2 TeV. We analyze the coupling of the dilaton with Standard Model (SM) fields in the bulk, and discuss two applications: i) Models with a light dilaton as the first particle beyond the SM pass quite easily all observational tests even with a dilaton lighter than the Higgs. However the possibility of a 125 GeV dilaton as a Higgs impostor is essentially disfavored; ii) We show how to extend the soft wall models to realize a 750 GeV dilaton that could explain the recently reported diphoton excess at the LHC. © 2016, The Author(s).

Casas J.A.,Institute Fisica Teorica | Espinosa J.R.,Institute Of Fisica Daltes Energies Ifae | Espinosa J.R.,Catalan Institution for Research and Advanced Studies | Moreno J.M.,Institute Fisica Teorica
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2016

One of the most exciting explanations advanced for the recent diphoton excess found by ATLAS and CMS is in terms of sgoldstino decays: a signal of low-energy supersymmetry-breaking scenarios. The sgoldstino, a scalar, couples directly to gluons and photons, with strength related to gaugino masses, that can be of the right magnitude to explain the excess. However, fitting the suggested resonance width, Γ. ≃. 45 GeV, is not so easy. In this paper we explore efficient possibilities to enhance the sgoldstino width, via the decay into two Higgses, two Higgsinos and through mixing between the sgoldstino and the Higgs boson. In addition, we present an alternative and more efficient mechanism to generate a mass splitting between the scalar and pseudoscalar components of the sgoldstino, which has been suggested as an interesting alternative explanation to the apparent width of the resonance. © 2016 The Author(s).

Rico J.,Institute Of Fisica Daltes Energies Ifae
Nuclear and Particle Physics Proceedings | Year: 2016

MAGIC is a system of two 17-m diameter Cherenkov telescopes, located at the Observatorio del Roque de los Muchachos, in the Canary island La Palma (Spain). MAGIC performs astronomical observations of gamma-ray sources in the energy range between 50 GeV and 10 TeV. The first MAGIC telescope has been operating since 2004, and in 2009 the system was completed with the second one. During 2011 and 2012 the electronics for the readout system were fully upgraded, and the camera of the first telescope replaced. After that, no major hardware interventions are foreseen in the next years, and the experiment has undertaken a final period of steady astronomical observations.MAGIC studies particle acceleration in the most violent cosmic environments, such as active galactic nuclei, gamma-ray bursts, pulsars, supernova remnants or binary systems. In addition, it addresses some fundamental questions of Physics, such as the origin of Galactic cosmic rays and the nature of dark matter. Moreover, by observing the gamma-ray emission from sources at cosmological distances, we measure the intensity and evolution of the extragalactic background radiation, and perform tests of Lorentz Invariance.In this paper I present the status and some of the latest results of the MAGIC gamma-ray telescopes. © 2015 Elsevier B.V.

Sanchez F.,Institute Of Fisica Daltes Energies Ifae
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

Uncertainties in modeling neutrino-nucleus interactions are a major contribution to systematic errors in long-baseline neutrino oscillation experiments. Accurate modeling of neutrino interactions requires additional experimental observables such as the Adler angles which carry information about the polarization of the Δ resonance and the interference with nonresonant single pion production. The Adler angles were measured with limited statistics in bubble chamber neutrino experiments as well as in electron-proton scattering experiments. We discuss the viability of measuring these angles in neutrino interactions with nuclei. © 2016 American Physical Society.

Anjos N.,Institute Of Fisica Daltes Energies Ifae
EPJ Web of Conferences | Year: 2016

Several characteristics of jet production in pp collisions have been measured by the ATLAS and CMS collaborations at the LHC. Measurements of event shapes and multi-jet production probe the dynamics of QCD in the soft regime and can constrain parton shower and hadronisation models. Measurements of multi-jet systems with a veto on additional jets probe QCD radiation effects. Double-differential cross-sections for threeand four-jet final states are measured at different centre-of-mass energies of pp collisions and are compared to expectations based on NLO QCD calculations. The distribution of the jet charge has been measured in di-jet events and compared to predictions from different hadronisation models and tunes. Jet-jet energy correlations are sensitive to the strong coupling constant. These measurements constitute precision tests of QCD in a new energy regime. © 2016 Owned by the authors, published by EDP Sciences.

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