An interesting class of models posits that the dark matter is a Majorana
fermion which interacts with a quark together with a colored scalar mediator. Such a
theory can be tested in direct detection experiments, through dark matter scattering
with heavy nuclei, and at the LHC, via jets and missing energy signatures. Motivated
by the fact that such theories have spin-independent...
This talk will report the results of a search for new phenomena in final states with at least one energetic jet and large missing transverse momentum. The search uses $80$ fb$^{−1}$ of $pp$ collision data at $\sqrt{S}=13$ TeV collected in Run-2 with the ATLAS detector at the Large Hadron Collider. Results are interpreted in the context of Dark Matter, Dark Energy, Supersymmetry, Higgs...
Discovering dark matter particles and understanding their connection to the Standard Model is one of the greatest quests in particle physics and cosmology today and the Large Hadron Collider (LHC) offers a large range of important search channels. The first searches for weakly interacting massive particle dark matter produced in association with top quarks based on the complete dataset at 13...
The LHC offers the best prospects for direct production of WIMP Dark Matter (DM) and gauge bosons arising from a dark sector beyond the Standard Model (SM). In particular, a neutral Z’{DM} boson mediating DM-SM interactions is a prime target for resonance searches, and its couplings can thereby be constrained within the broad context of mediator-based simplified DM models. In this poster I...
Abstract: Dark matter models predict the production of weakly interacting massive particles (WIMPs) in proton-proton collisions. Many of these theories are tested at the LHC using the ATLAS detector, in which events are characterised by large missing transverse momentum carried by a dark matter particle-antiparticle pair. These models predict that the dark matter pair may be produced via a new...
One of the ways to look for evidence of dark matter (DM) at a collider experiment is through s-channel processes where a DM mediator decays to two quarks. At ATLAS, analyses looking for di-jet resonances are limited to mediator masses above a TeV, due to the high transverse momentum (pT) requirements of jet triggers. However, sub-TeV mass regions can be explored if the resonance is produced...
A RECAST of an existing ATLAS analysis is used to perform a search for dark matter produced in association with a dark Higgs boson decaying to two b-quarks from pp collisions at a centre-of-mass energy of sqrt(s) = 13 TeV. RECAST is an analysis reinterpretation framework; since analyses are often sensitive to a range of models, RECAST can be used to constrain the plethora of dark matter models...
A search for new resonances decaying into two hadronic jets is reported using the entire dataset of proton-proton collisions recorded at sqrt(s) = 13 TeV with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 fb−1. The dijet invariant mass distribution is compared to a smoothly-falling background prediction obtained by...
A search for dark matter produced in association with a Higgs boson decaying to a bottom quark-antiquark pair is performed in proton-proton collisions at a center-of-mass energy of 13 TeV collected with the CMS detector at the LHC. The analyzed data sample corresponds to an integrated luminosity of 35.9 fb-1. The signal is characterized by a large missing transverse momentum recoiling against...
Probing the energy frontier with increasingly large particle colliders has culminated at the beginning of the current decade with the discovery of the Higgs boson, the final particle predicted by the Standard Model of particle physics. Nevertheless, the energy frontier program has so far failed to find any particles of the dark sector comprising the 95% of the Universe’s energy density not...
The SHiP Collaboration has proposed a general-purpose experimental facility operating in beam dump mode at the CERN SPS accelerator with the aim of searching for light, long-lived exotic particles of Hidden Sector models. The SHiP experiment incorporates a muon shield based on magnetic sweeping and two complementary apparatuses. The detector immediately downstream of the muon shield is...
Based on a benchmark Hidden Sector model, this analysis explores the possibility of new physics being present at the LHC through long-lived particles. Given that the lifetime of these particles is mostly unconstrained, this raises the possibility of these particles decaying before they leave ATLAS detector. The specific scenario of two of these long-lived particles decaying to standard model...
In R-parity conserving supersymmetric extensions of the standard model, the lightest neutralino $\tilde{\chi}_{1}^{0}$, which is also the lightest supersymmetric particle (LSP), plays the role of the canonical dark matter particle candidate. The traditional $\tilde{\chi}_{1}^{0}$ searches using Drell-Yan processes suffer in the compressed spectrum scenarios, where the LSP mass is only slightly...
Long-lived particles (LLPs) are a feature of many theories beyond the Standard Model and would be generically produced in exotic decays of the Higgs boson. No known search strategy with current experiments will be able to observe the decay of neutral LLPs with masses above $\sim 1\ \mathrm{GeV}$ at lifetimes near the upper limit of $c\tau \sim 10^7\ \mathrm{m}$ set by effects on Big Bang...
CP violation has been observed in neutral meson oscillations, which may explain the matter-antimatter asymmetry of the Universe. We found that a supersymmetric theory with an unbroken U(1)R symmetry and Dirac gauginos can accommodate baryogenesis and asymmetric sneutrino dark matter production via B meson oscillations. This model can be tested via semileptonic asymmetries of B mesons, Flavor...
Dark matter direct searches place very stringent constraints on the possible DM candidates proposed in extensions of the Standard Model. There are however models where these constraints are avoided. One of the simplest and most striking examples comes from a straightforward Higgs portal pseudoscalar DM model featured with a softly broken U(1) symmetry. In this model the tree-level DM-nucleon...
We are interested in the purpose of a dipolar fermionic particle as a viable candidate of Dark Matter (DDM). Then, we study the annihilation of dark matter, considering it as a neutral particle with magnetic ($M$) and electric ($D$) dipolar moments not vanishing. Total cross section $\sigma(\chi \chi \rightarrow \gamma \gamma$) is computed by starting from a general form of coupling $\chi \chi...
A search for compressed supersymmetry in the stau-neutralino ($\tilde{\tau}\tilde{\chi}^{0}_{1}$) coannihilation region is presented. The search targets final states with exactly one low-energy (``soft'') hadronically-decaying $\tau$ lepton and large missing transverse momentum ($\vec{E}^{miss}_{T}$) due to the natural kinematic boost from a high transverse momentum jet from initial state...
Many models predict new particles with sizeable couplings to quarks and gluons. A search is performed for localised excesses in dijet mass distributions of low-dijet-mass events produced in association with a high transverse energy photon. The search uses up to 79.8 fb-1 of LHC proton–proton collisions collected by the ATLAS experiment at a centre-of-mass energy of 13 TeV during 2015–2017. Two...
I will discuss the cosmology and LHC phenomenology of a consistent, strongly interacting dark sector coupled to Standard Model particles through a Z' mediator. I will lay out the requirements for the model to be cosmologically viable, consider the dominant freeze-out processes, and discuss bounds from direct detection. Using this consistent SIMP sector, I will then focus on the sensitivity of...
We propose a strategy for searching for theoretically-unanticipated new physics. Searches for resonances decaying into pairs of visible particles are experimentally very powerful due to the localized mass peaks and have a rich history of discovery. Yet, due to a focus on subsets of theoretically-motivated models, the landscape of such resonances is far from thoroughly explored. We survey the...
Searches for dark matter at the LHC have largely focused on Weakly Interacting Massive Particles (WIMPs). But what if instead of just one type of dark matter particle, there exists a richer dark sector hidden from ordinary view? This opens up a whole new paradigm for dark matter searches, allowing us to focus not only on the coupling between dark matter and the Standard Model, but also on the...
Most theories that predict dark matter production at colliders rely on weakly coupled dark matter and the existence of WIMPs, or weakly interacting massive particles; however, there can be dark matter signatures in colliders that emerge from strongly coupled dark matter. These signatures are varied, ranging from emerging jets to Stealth Dark Matter. Another possible signature is semi-visible...
In this study, we apply LHC data to constrain the extension of the Standard Model by an anomaly-free $U(1)_{l_\mu-l_\tau}$ gauge group; this model contains a new gauge boson ($Z′$) and a scalar dark matter particle ($\phi_{DM}$). We recast a large number of LHC analyses from ATLAS and CMS of multi-lepton final states. We find that for 10 GeV < $m_{Z′}$ < 60 GeV the strongest constraint comes...
I will summarize recent studies by the GAMBIT Collaboration in which we investigated the combined collider constraints on the chargino and neutralino sector of the Minimal Supersymmetric Standard Model. Through a large fit using GAMBIT we found that current ATLAS and CMS results with 36\,fb$^{-1}$ of 13\,TeV LHC collision data do not provide a general constraint on the lightest neutralino and...
Long-lived particles provide a unique probe for dark sectors. The searches for such signatures are challenging at the LHC. In comparison with the light Standard Model particles, the decay
products of massive LLPs arrive at detectors with time delay around the nanosecond scale. We propose new strategies to take advantage of this time delay by using initial state radiation jets to timestamp the...
The observed matter-antimatter asymmetry in universe poses a serious challenge to our understanding of nature. BNV decay has been used in experiments to study this large scale fact. BESIII searches for BNV and LNV processes with the world largest J/psi data sets directly produced in e+e- collision. The BNV/LNV channel J/psi -> Lambda_c+ e- +c.c. is analyzed, no signal event is observed. The...
New interactions of neutrinos can stop them from free streaming in the early Universe even after the weak decoupling epoch. This results in the enhancement of the primordial gravitational wave amplitude on small scales compared to the standard $\Lambda$CDM prediction. We calculate the effect of dark matter neutrino interactions in CMB tensor B-modes spectrum. We show that the effect of new...
We present a novel framework capable of addressing the dark matter problem through freeze-in and freeze-out mechanisms, separately or together depending on the region of the parameter space considered. Apart from the fermionic dark matter candidate, the model features two charged partners, one fermionic and another scalar, which often have delayed decays leading to distinct features of such...
A search for beyond standard model (BSM) physics in events with a Z boson recoiling against missing transverse momentum at the CMS experiment at the LHC is presented. This search is interpreted for a spin-1 simplified dark matter vector or axial-vector mediator as well as for a Higgs-like scalar or pseudoscalar mediator. The search utilises the full Run II dataset corresponding to an...
We show that a simple Higgs-portal dark matter model can contain stable non-topological soliton states of dark matter. This macroscopic dark matter candidate has its interior in an electroweak symmetry unbroken vacuum. These dark matter balls can have its radius around the atomic scale and mass as large as $10^{34}$ GeV. We discuss the formation of these dark matter balls from the first-order...
The total decay width of the Higgs has not yet been constrained precisely, which allows for up to 30% of the branching fraction to be from beyond the standard model decays. If sufficiently light, dark matter motivates a decay of the Higgs to invisible final states. This talk will discuss searches for invisible decays of the Higgs produced in all production modes in pp collisions at √s= 13 TeV...
