arXiv subjects

B. Zaldivar

Publications and source records attributed to B. Zaldivar.

41 records · Page 3Linked to original sources

arXiv2020

Neutron-Antineutron Oscillation Search using a 0.37 Megaton$\cdot$Year Exposure of Super-Kamiokande

As a baryon number violating process with $ΔB=2$, neutron-antineutron oscillation ($n\to\bar n$) provides a unique test of baryon number conservation. We have performed a search for $n\to\bar n$ oscillation with bound neutrons in Super-Kamiokande, with the full data set from its first four run periods, representing an exposure of 0.37~Mton-years. The search used a multivariate analysis trained on simulated $n\to\bar n$ events and atmospheric neutrino backgrounds and resulted in 11 candidate events with an expected background of 9.3 events. In the absence of statistically significant excess, we derived a lower limit on $\bar n$ appearance lifetime in $^{16}$O nuclei of $3.6\times{10}^{32}$ years and on the neutron-antineutron oscillation time of $τ_{n\to\bar n} > 4.7\times10^{8}$~s at 90\% C.L..

hep-ex↗

arXiv2020

Jet tagging made easy

We develop taggers for multi-pronged jets that are simple functions of jet substructure (so-called `subjettiness') variables. These taggers can be approximately decorrelated from the jet mass in a quite simple way. Specifically, we use a Logistic Regression Design (LoRD) which, even being one of the simplest machine learning classifiers, shows a performance which surpasses that of simple variables used by the ATLAS and CMS Collaborations and is not far from more complex models based on neural networks. Contrary to the latter, our method allows for an easy implementation of tagging tasks by providing a simple and interpretable analytical formula with already optimised parameters.

hep-ph↗

arXiv2019

Confronting minimal freeze-in models with the LHC

We present a class of dark matter models, in which the dark matter particle is a feebly interacting massive particle (FIMP) produced via the decay of an electrically charged and/or colored parent particle. Given the feeble interaction, dark matter is produced via the freeze-in mechanism and the parent particle is long-lived. The latter leads to interesting collider signatures. We study current LHC constrains on our models arising from searches for heavy charged particles, disappearing tracks, displaced leptons and displaced vertices. We demonstrate not only that collider searches can be a powerful probe of the freeze-in dark matter models under consideration, but that an observation can lead as well to interesting insights on the reheating temperature and thus on the validity of certain baryogenesis models.

hep-ph↗

arXiv2018

LHC-friendly minimal freeze-in models

We propose simple freeze-in models where the observed dark matter abundance is explained via the decay of an electrically charged and/or coloured parent particle into Feebly Interacting Massive Particles (FIMP). The parent particle is long-lived and yields a wide variety of LHC signatures depending on its lifetime and quantum numbers. We assess the current constraints and future high luminosity reach of these scenarios at the LHC from searches for heavy stable charged particles, disappearing tracks, displaced vertices and displaced leptons. We show that the LHC constitutes a powerful probe of freeze-in dark matter and can further provide interesting insights on the validity of vanilla baryogenesis and leptogenesis scenarios.

hep-ph↗

arXiv2018

Les Houches 2017: Physics at TeV Colliders New Physics Working Group Report

We present the activities of the `New Physics' working group for the `Physics at TeV Colliders' workshop (Les Houches, France, 5--23 June, 2017). Our report includes new physics studies connected with the Higgs boson and its properties, direct search strategies, reinterpretation of the LHC results in the building of viable models and new computational tool developments.

hep-ph↗