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Pavon Valderrama M.,Julich Research Center | Pavon Valderrama M.,Institute Fisica Corpuscular IFIC
Physical Review C - Nuclear Physics | Year: 2011

We study the perturbative renormalizability of chiral two-pion exchange for singlet and triplet channels within effective field theory, provided that the one-pion exchange piece of the interaction has been fully iterated. We determine the number of counterterms/subtractions needed to obtain finite results when the cutoff is removed, resulting in three counterterms for the singlet channel and six for the triplet. The results show that perturbative chiral two-pion exchange reproduce the data up to a center-of-mass momentum of k∼200-300 MeV in the singlet channel and k∼300-400 MeV in the triplet. © 2011 American Physical Society. Source


Pavon Valderrama M.,Julich Research Center | Pavon Valderrama M.,Institute Fisica Corpuscular IFIC | Ruiz Arriola E.,University of Granada
Physical Review C - Nuclear Physics | Year: 2011

In this work we consider the renormalization of the chiral two-pion exchange potential with explicit Δ excitations for nucleon-nucleon scattering at next-to-leading (NLO) and next-to-next-to-leading order (N2LO). Because of the singular nature of the chiral potentials, correlations between different partial waves are generated. In particular, we show that two-body scattering by a short distance power like singular attractive interaction can be renormalized in all partial waves with a single counterterm, provided the singularities are identical. A parallel statement holds in the presence of tensor interactions when the eigenpotentials in the coupled channel problem also coincide. Although this construction reduces the total number of counterterms to 11 in the case of nucleon-nucleon scattering with chiral two-pion exchange interactions with Δ degrees of freedom, the differences in the scattering phases as compared to the case with the uncorrelated partial-wave renormalization become smaller as the angular momentum is increased in the elastic scattering region. © 2011 American Physical Society. Source


Sanchez Martinez V.,Institute Fisica Corpuscular IFIC
Nuclear and Particle Physics Proceedings | Year: 2016

The ATLAS experiment has performed a search for new states decaying to top quark pairs using a data set of 14fb-1 of proton-proton collisions collected during the 2012 run at s=8 TeV of the Large Hadron Collider (LHC). The combination of a classical, resolved analysis with a novel algorithm designed specifically for boosted top quarks yields good acceptance for a broad range of resonance masses. No deviations from the Standard Model expectations are observed and stringent limits are set on the production cross-section times branching ratio of several resonance models. © 2016 Elsevier B.V.. Source


Escudero L.,Institute Fisica Corpuscular IFIC
Nuclear and Particle Physics Proceedings | Year: 2016

The T2K long-baseline neutrino oscillation experiment has observed the disappearance of νμ and the appearance of νe from its νμ beam and it has accumulated 6.57×1020 protons on target, ~ 8% of its goal POT. Combining its νμ disappearance and νe appearance measurements with the results from reactor experiments, T2K has obtained the first constraint to date on the CP-violating phase δCP. Two kind of joint 3-flavour oscillation analyses have been performed, based on either Frequentist or Bayesian methods, and the results from both analyses indicate that δCP is consistent with -π/2. Furthermore, the data excluded values for δCP: the excluded regions found at the 90% CL with the Frequentist analysis are [0.146,0.825]π ([-0.080,1.091]π) for normal (inverted) mass hierarchy; and the Bayesian 90% CI obtained, marginalizing over the mass hierarchy and assuming flat priors, is [-1.13,0.14]π. Although more T2K neutrino (and possibly anti-neutrino) data is necessary to confirm this result, whose sensitivity could be enhanced in combination with results from a new generation of long-baseline neutrino oscillation experiments and the latest reactor measurements, this first hint on CP violation opens exciting possibilities. © 2015 Elsevier B.V.. Source


Escudero L.,Institute Fisica Corpuscular IFIC
Nuclear and Particle Physics Proceedings | Year: 2016

The T2K long-baseline neutrino oscillation experiment has observed the disappearance of νμ and the appearance of νe from its νμ beam. Since 2010, it has accumulated 6.57×1020 protons on target and observed 120νμ and 28νe event candidates. With this dataset, corresponding to only ~8% of its goal POT, T2K has achieved world leading results: the best precision in θ23, the strongest evidence of νe appearance in a νμ beam and the first hint on δCP. Its first joint 3-flavour oscillation analysis, combining the νμ disappearance and νe appearance channels, is presented in this paper using a Frequentist approach. The results of this analysis, combined with the measurements from reactor experiments, indicate that δCP is consistent with -π/2. Furthermore, the data excluded values of δCP in the interval [0.146, 0.825]π([-0.080, 1.091]π) at the 90% CL for normal (inverted) mass hierarchy. © 2015 Elsevier B.V. Source

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