arXiv subjects

Pilar Hernández

Publications and source records attributed to Pilar Hernández.

24 records · Page 2Linked to original sources

arXiv2019

Meson interactions at large $N_c$ from Lattice QCD

We report on the computation of the scaling of QCD observables with the number of colours, $N_c$. For this, we use dynamical configurations with four active flavours, $N_f=4$, and values of $N_c=3-6$. We study the meson masses and decay constants, and compute the leading and subleading contributions to the Low Energy Constants (LECs) of the chiral Lagrangian. We also explore $ππ$ scattering in the $I=2$ channel, and compute the $K \to π$ weak decay matrix elements. We comment on the relation of the latter to $K \to ππ$ processes and the $ΔI=1/2$ rule.

hep-lat↗

arXiv2019

Large $N_c$ scaling of meson masses and decay constants

We perform an $\textit{ab initio}$ calculation of the $N_c$ scaling of the low-energy couplings of the chiral Lagrangian of low-energy strong interactions, extracted from the mass dependence of meson masses and decay constants. We compute these observables on the lattice with four degenerate fermions, $N_f=4$, and varying number of colours, $N_c=3-6$, at a lattice spacing of $a\simeq 0.075$ fm. We find good agreement with the expected $N_c$ scaling and measure the coefficients of the leading and subleading terms in the large $N_c$ expansion. From the subleading $N_c$ corrections, we can also infer the $N_f$ dependence, that we use to extract the value of the low-energy couplings for different values of $N_f$. We find agreement with previous determinations at $N_c=3$ and $N_f=2, 3$ and also, our results support a strong paramagnetic suppression of the chiral condensate in moving from $N_f=2$ to $N_f=3$.

hep-lat↗

arXiv2018

Follow-up on non-leptonic kaon decays at large $N_c$

We report on the status of our dynamical simulations of a $SU (N_c )$ gauge theory with $N_c=3-6$ and $N_f =4$ fundamental fermions. These ensembles can be used to study the Large $N_c$ scaling of weak matrix elements in the GIM limit $m_c=m_u$, that might shed some light on the origin of the $ΔI=1/2$ rule. We present preliminary results for the $K \to π$ matrix elements in the $N_c=3$ dynamical simulations, where we observe a significant effect of the quark loops that goes in the direction of enhancing the ratio of $A_0/A_2$ amplitudes. Finally, we present the relevant NLO Chiral Perturbation Theory predictions for the relation between $K \to π$ and $K \to ππ$ amplitudes in the light charm limit.

hep-lat↗

arXiv2015

Probing the Type I Seesaw Mechanism with Displaced Vertices at the LHC

The observation of Higgs decays into heavy neutrinos would be strong evidence for new physics associated to neutrino masses. In this work we propose a search for such decays within the Type I seesaw model in the few-GeV mass range via displaced vertices. Using 300 fb$^{-1}$ of integrated luminosity, at 13 TeV, we explore the region of parameter space where such decays are measurable. We show that, after imposing pseudorapidity cuts, there still exists a region where the number of events is larger than $\mathcal{O}(10)$. We also find that conventional triggers can greatly limit the sensitivity of our signal, so we display several relevant kinematical distributions which might aid in the optimization of a dedicated trigger selection.

hep-ph↗

arXiv2012

N_f=2 chiral dynamics in the mixed chiral regime

We present a study of the pseudoscalar propagator in the mixed chiral regime with valence quark masses in the ε-regime and sea quark masses in the p-regime. We first show the NNLO prediction of this observable in the chiral expansion. In sectors of fixed topology, the correlator has a pole in 1/m_v^2 that can be matched to the topological zero-mode contributions to the correlator. We compute the residue of this pole in a N_f=2 mixed-action simulation and compare the results with the prediction in Chiral Perturbation Theory.

hep-lat↗

arXiv2002

Residual mass effects in improved domain wall fermions

In order to improve simulations with domain wall fermions (DWFs), it has been suggested to project out a number of low-lying eigenvalues of the 4-dimensional Dirac operator that generates the transfer matrix of DWF. We investigate how this projection method affects chiral properties of quenched DWF. In particular, we study the behaviour of the residual mass as a function of the size of the extra dimension.

hep-lat↗