192 research outputs found
Composite Higgs at high transverse momentum
In this paper we explore composite Higgs scenarios through the effects of light top-partners in Higgs+Jet production at the LHC. The pseudo-Goldstone boson nature of the Higgs field means that single-Higgs production via gluon fusion is insensitive to the mass spectrum of the top-partners. However in associated production this is not the case, and new physics scales may be probed. In the course of the work we consider scenarios with both one and two light top-partner multiplets in the spectrum of composite states. In compliance with perturbativity and experimental constraints, we study corrections to the Higgs couplings and the effects that the light top-partner multiplets have on the transverse momentum spectrum of the Higgs. Interestingly, we find that the corrections to the Standard Model expectation depend strongly on the representation of the top-partners in the global symmetry
Non-Custodial Warped Extra Dimensions at the LHC?
With the prospect of improved Higgs measurements at the LHC and at proposed
future colliders such as ILC, CLIC and TLEP we study the non-custodial
Randall-Sundrum model with bulk SM fields and compare brane and bulk Higgs
scenarios. The latter bear resemblance to the well studied type III
two-Higgs-doublet models. We compute the electroweak precision observables and
argue that incalculable contributions to these, in the form of higher
dimensional operators, could have an impact on the T-parameter. This could
potentially reduce the bound on the lowest Kaluza-Klein gauge boson masses to
the 5 TeV range, making them detectable at the LHC. In a second part, we
compute the misalignment between fermion masses and Yukawa couplings caused by
vector-like Kaluza-Klein fermions in this setup. The misalignment of the top
Yukawa can easily reach 10%, making it observable at the high-luminosity LHC.
Corrections to the bottom and tau Yukawa couplings can be at the percent level
and detectable at ILC, CLIC or TLEP.Comment: 24 pages, 4 figures; v2: Typo in eq.48 fixed, references adde
Kaluza-Klein gravitons at LHC2
In this work we study constraints from new searches for heavy particles at the LHC on the allowed masses and couplings of a KK Graviton in a holographic composite Higgs model. Keeping new electroweak states heavy such that electroweak precision tests are satisfied, we control the mass of the lightest KK graviton using a brane kinetic term. With this we study KK graviton masses from 0.5-3 TeV. In our analysis we also employ Little Randall-Sundrum (RS) Models, characterised by a lower UV scale in the 5D model which in turn implies modified couplings to massless bulk fields. Viewing this scenario as a strongly coupled 4D theory with a composite Higgs boson, the KK graviton is interpreted as a composite spin-2 state and the varying UV scale corresponds to a varying intermediate scale between the cutoff of the low energy effective theory and the Planck scale. We find that KK gravitons with masses in the range 0.5-3 TeV are compatible with current collider constraints, where the most promising channels for detecting these states are the di-photon and ZZ channels. A detection is more likely in the little RS models, in which the dual gauge theory has a larger number of colours than in traditional RS models
Bump Hunting in Latent Space
Unsupervised anomaly detection could be crucial in future analyses searching
for rare phenomena in large datasets, as for example collected at the LHC. To
this end, we introduce a physics inspired variational autoencoder (VAE)
architecture which performs competitively and robustly on the LHC Olympics
Machine Learning Challenge datasets. We demonstrate how embedding some physical
observables directly into the VAE latent space, while at the same time keeping
the classifier manifestly agnostic to them, can help to identify and
characterise features in measured spectra as caused by the presence of
anomalies in a dataset.Comment: 5 pages, 4 figure
A Normalized Autoencoder for LHC Triggers
Autoencoders are an effective analysis tool for the LHC, as they represent
one of its main goal of finding physics beyond the Standard Model. The key
challenge is that out-of-distribution anomaly searches based on the
compressibility of features do not apply to the LHC, while existing
density-based searches lack performance. We present the first autoencoder which
identifies anomalous jets symmetrically in the directions of higher and lower
complexity. The normalized autoencoder combines a standard bottleneck
architecture with a well-defined probabilistic description. It works better
than all available autoencoders for top vs QCD jets and reliably identifies
different dark-jet signals.Comment: 26 pages, 11 figures; update based on referees repor
Bayesian Probabilistic Modelling for Four-Tops at the LHC
Monte Carlo (MC) generators are crucial for analyzing data at hadron
colliders, however, even a small mismatch between the MC simulations and the
experimental data can undermine the interpretation of LHC searches in the SM
and beyond. The jet multiplicity distributions used in four-top searches, one
of the ultimate rare processes in the SM currently being explored at the LHC,
makes an ideal testing ground to explore for new ways
to reduce the impact of MC mismodelling on such observables. In this Letter, we
propose a novel weakly-supervised method capable of disentangling the signal from the dominant background, while partially correcting for
possible MC imperfections. A mixture of multinomial distributions is used to
model the light-jet and -jet multiplicities under the assumption that these
are conditionally independent given a categorical latent variable. The signal
and background distributions generated from a deliberately untuned MC simulator
are used as model priors. The posterior distributions, as well as the signal
fraction, are then learned from the data using Bayesian inference. We
demonstrate that our method can mitigate the effects of large MC mismodellings
using a realistic search in the same-sign dilepton channel,
leading to corrected posterior distributions that better approximate the
underlying truth-level spectra.Comment: 5 pages, 3 figures, with supplementary material at
https://github.com/ManuelSzewc/bayes-4top
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