Search results for " Collider"

Third generation SUSY searches in ATLAS

2016

Supersymmetry (SUSY) is one of the most popular and promising extensions to the Standard Model (SM) of particle physics. It predicts partner particles for all SM particles with a spin difference of $1/2$. These SUSY partners, if they exist within a reachable energy scale, should be produced at the Large Hadron Collider (LHC). The events are usually characterized by high missing transverse energy and can have varying jet and lepton multiplicities, depending on the model used. Searches for partners of third generation squarks are of special interest because of their special event topologies.\\ Many searches have been performed in proton-proton collisions at $\sqrt{s}=13$ TeV at the LHC with t…

A Brief Discussion on the Performance of the MoEDAL and the LHCf Experiments

2018

The Monopole and Exotics Detector at the LHC (MoEDAL) experiment is an experiment dedicated to searching for beyond standard model (BSM) particles like magnetic monopoles, highly ionizing particles and slow-moving supersymmetric particles. In many ways, this detector complements the BSM searches of ATLAS and CMS. In this document, a brief description of the MoEDAL detector and performance is given. The Large Hadron Collider Forward (LHCf) experiment, on the other hand, is dedicated to measuring the neutral particles produced in the hadronic collision in the very forward region. This document also briefly discusses the LHCf detector and its performance.

Search for the Production of a Long-Lived Neutral Particle Decaying within the ATLAS Hadronic Calorimeter in Association with a Z Boson from pp Colli…

2019

This Letter presents a search for the production of a long-lived neutral particle (Zd) decaying within the ATLAS hadronic calorimeter, in association with a standard model (SM) Z boson produced via an intermediate scalar boson, where Z→+ (=e, μ). The data used were collected by the ATLAS detector during 2015 and 2016 pp collisions with a center-of-mass energy of s=13 TeV at the Large Hadron Collider and correspond to an integrated luminosity of 36.1±0.8 fb-1. No significant excess of events is observed above the expected background. Limits on the production cross section of the scalar boson times its decay branching fraction into the long-lived neutral particle are derived as a function of …

FIRST EVIDENCE FOR DIRECT CP VIOLATION

1989

LHC phenomenology of light pseudoscalars in the NMSSM

2015

After the discovery of the 125 GeV Higgs boson, the Next-to-Minimal Supersymmetric Standard Model (NMSSM) has become more interesting as a model for new physics since new tree-level contributions to the Higgs mass makes it easier to accommodate the relatively high measured value, as compared to the MSSM. One very distinctive feature of the NMSSM is the possible existence of a light singlet-like pseudoscalar. As this pseudoscalar may be lighter than the discovered Higgs boson without conflict with data, it may lead to LHC signatures rather different to what is usually searched for in terms of new physics. In these proceedings we will discuss studies concerning the discoverability of such lig…

LHC constraints on two-Higgs doublet models

2014

The recent discovery of a Standard Model-like boson with mass of about 126 GeV seems to be the first direct information on the electroweak symmetry breaking mechanism. Using the available experimental data from the LHC and Tevatron we study the implications on the parameter space of the Two-Higgs Doublet Model extension of the Standard Model. The generic structure of the Aligned Two-Higgs Doublet Model (ATHDM) is imposed in the Yukawa sector; also the models with discrete Z2 symmetries are analyzed.

R-parity violating supersymmetry and neutrino physics: experimental signatures

2015

$R$-parity violating supersymmetric models (RPV SUSY) are becoming increasingly more appealing than its $R$-parity conserving counterpart in view of the hitherto non-observation of SUSY signals at the LHC. In this paper, we discuss RPV scenarios where neutrino masses are naturally generated, namely RPV through bilinear terms (bRPV) and the $\mu$-from-$\nu$ supersymmetric standard model ($\mu\nu$SSM). The latter is characterised by a rich Higgs sector that easily accommodates a 125-GeV Higgs boson. The phenomenology of such models at the LHC is reviewed, giving emphasis on final states with displaced objects, and relevant results obtained by LHC experiments are presented. The implications fo…

Search for Heavy Higgs Bosons Decaying into Two Tau Leptons with the ATLAS Detector Using pp Collisions at s=13  TeV

2020

A search for heavy neutral Higgs bosons is performed using the LHC Run 2 data, corresponding to an integrated luminosity of 139  fb^{-1} of proton-proton collisions at sqrt[s]=13  TeV recorded with the ATLAS detector. The search for heavy resonances is performed over the mass range 0.2-2.5 TeV for the τ^{+}τ^{-} decay with at least one τ-lepton decaying into final states with hadrons. The data are in good agreement with the background prediction of the standard model. In the M_{h}^{125} scenario of the minimal supersymmetric standard model, values of tanβ>8 and tanβ>21 are excluded at the 95% confidence level for neutral Higgs boson masses of 1.0 and 1.5 TeV, respectively, where tanβ is the…

Neutron emission from electromagnetic dissociation of Pb nuclei at $\sqrt {s_{NN}} = 2.76$ TeV measured with the ALICE ZDC

2014

The ALICE Zero Degree Calorimeter system (ZDC) is composed of two identical sets of calorimeters, placed at opposite sides with respect to the interaction point, 114 meters away from it, complemented by two small forward electromagnetic calorimeters (ZEM). Each set of detectors consists of a neutron (ZN) and a proton (ZP) ZDC. They are placed at zero degrees with respect to the LHC axis and allow to detect particles emitted close to beam direction, in particular neutrons and protons emerging from hadronic heavy-ion collisions (spectator nucleons) and those emitted from electromagnetic processes. For neutrons emitted by these two processes, the ZN calorimeters have nearly 100% acceptance. Du…

Lepton number violation and scalar searches at the LHC

2013

We review the SM extensions with scalar multiplets including doubly- charged components eventually observable as di-leptonic resonances at the LHC. Special emphasis is paid to the limits on LNV implied by doubly- charged scalar searches at the LHC, and to the characterization of the multiplet doubly-charged scalars belong to if they are observed to decay into same-sign charged lepton pairs.