The Excited Scalars of the Universal Extra Dimension Model

In the minimal Universal Extra Dimension (mUED) model, there are four physical scalar particles at the n=1 level, two charged and two neutral. Due to the almost degenerate nature of the spectrum, the detection of these scalars is a major challenge, perhaps the greatest experimental challenge if UED-type new physics is observed at the Large Hadron Collider (LHC). We explore the possibility of detecting these particles at the International Linear Collider (ILC), and emphasise the need of having an excellent soft tau detection efficiency.Comment: 12 pages, 9 figures: minor changes from v1, version to be publishe

The role of MSSM heavy Higgs production in the self coupling measurement of the 125 GeV Higgs boson at the LHC

Measurement of the self coupling of 125 GeV Higgs boson is one of the most crucial tasks for high luminosity run of the LHC and it can only be measured in the di-Higgs final state. In the minimal supersymmetric standard model, heavy CP even Higgs ($H$) can decay into lighter 125 GeV Higgs boson ($h$) and therefore influence the di-Higgs production. We investigate the role of single $H$ production in the measurement of self coupling of $h$. We find that $H \rightarrow hh$ decay can nontrivially affect the $h$ self coupling measurement in low tan$\beta$ regime when the mass of the heavy Higgs boson lies between 250 - 600 GeV and depending on the parameter space it may be seen as an enhancement of the self coupling of 125 GeV Higgs boson.Comment: 20 pages, 3 figures; References added; Text updated with more detailed results and new figures, To appear in Phys. Rev.

Lepton flavour violating decay of 125 GeV Higgs boson to μτ\mu\tau channel and excess in ttˉHt\bar t H

A recent search for the lepton flavor violating (LFV) decays of the Higgs boson, performed by CMS collaboration, reports an interesting deviation from the standard model (SM). The search conducted in the channel $H\rightarrow \mu\tau_e$ and $H\rightarrow \mu\tau_{\textrm{had}}$ shows an excess of $2.4\sigma$ signal events with 19.7 fb$^{-1}$ data at a center-of-mass energy $\sqrt s=8$ TeV. On the other hand, a search performed by CMS collaboration for the SM Higgs boson produced in association with a top quark pair ($t\bar t H$) also showed an excess in the same-sign di-muon final state. In this work we try to find out if these two seemingly uncorrelated excesses are related or not. Our analysis reveals that a lepton flavour violating Higgs decay ($H\rightarrow\mu\tau$) can partially explain the excess in the same sign di-muon final state in the $t\bar t H$ search, infact brings down the excess well within 2$\sigma$ error of the SM expectation. Probing such non-standard Higgs boson decay is of interest and might contain hints of new physics at the electroweak scale.Comment: 10 pages, 2 figures and 3 table

Study of energy deposition patterns in hadron calorimeter for prompt and displaced jets using convolutional neural network

Sophisticated machine learning techniques have promising potential in search for physics beyond Standard Model in Large Hadron Collider (LHC). Convolutional neural networks (CNN) can provide powerful tools for differentiating between patterns of calorimeter energy deposits by prompt particles of Standard Model and long-lived particles predicted in various models beyond the Standard Model. We demonstrate the usefulness of CNN by using a couple of physics examples from well motivated BSM scenarios predicting long-lived particles giving rise to displaced jets. Our work suggests that modern machine-learning techniques have potential to discriminate between energy deposition patterns of prompt and long-lived particles, and thus, they can be useful tools in such searches.Comment: 32 pages, 17 figures; version accepted for publication in JHE