We analyze the inclusive decay mode $B\to X_s+{\rm Missing Energy}$ in the unparticle model, where an unparticle can also serve as the missing energy. We use the Heavy Quark Effective Theory in the calculation. The analytical result of the decay width in the free quark limit and that of the differential decay rate to the order of $1/m_b^2$ are presented. Numerical results of the inclusive mode show interesting differences from those of the exclusive modes. Near the lower endpoint region, the $d_{\mathcal U}<2$ unparticle has very different behavior from the Standard Model particles.
We analyze the branching ratio and spectrum for the decay mode $K^+ \toπ^++{\not}E$(missing energy) in the unparticle model, where an unparticle can also serve as the missing energy. A vector unparticle can even mediate the $K^+ \to π^+ +ν\barν$, resulting complicated interference with the Standard Model.
In the present work we study the effects of an unparticle $\unpart$ as the possible source of missing energy in the decay $B \to K (K^*) + {\rm missing energy}$. We find that the dependence of the differential branching ratio on the $K$($K^*$)-meson's energy in the presence of the vector unparticle operators is very distinctive from that of the SM. Moreover, in using the existing upper bound on $B \to K (K^*) + {\rm missing energy}$ decays, we have been able to put more stringent constraints on the parameters of unparticle stuff.
We study unparticle physics effects in (Lambda_b -> Lambda + missing energy) decay with polarized $Λ_b$ and $Λ$ baryons. The sensitivity of the branching ratio of this decay and polarizations of (Lambda_b) and (Lambda) baryons on the scale dimension d_U and effective cut-off parameter (Lambda_U) are discussed.
We examine the effects of an unparticle $\mathcal{U}$ as a possible source of missing energy in the p-wave decays of $B$ meson. The dependence of the differential branching ratio on the $K_{0}^{\ast}(K_{1}) -$% meson's energy is discussed in the presence of scalar and vector unparticle operators and significant deviation from the standard model value is found after addition of these operators. Finally, we have shown the dependence of branching ratio for the above said decays on the parameters of the unparticle stuff like the effective couplings, cutoff scale $Λ_{% \mathcal{U}}$ and the scale d…
We summarize the works presented in Refs. \cite{1,2} on collider phenomenology of the unparticle physics associated with an exact scale invariant sector possessing a non-trivial infrared fixed point at a high energy scale. We give highlights on the motivations of unparticle and derivation of the phase space and the unparticle propagator. We study two categories of phenomenology: (i) real emission of unparticle that gives rise to peculiar missing energy signatures, and (ii) virtual exchange of unparticle that interferes with the standard model amplitudes.
We study the production of the vector $U$ -unparticle stuff and a single photon in decays of a dilaton. The signals of an unparticle can be detected through the missing energy and momentum distribution carried away by $U$ once it was produced in radiative decay of a dilaton The continuous energy spectrum of the emitted photons encoding the recoil unparticle can be measured in precision studies of rare decays of the dilaton or Higgs-boson after their discoveres.
I discuss some simple aspects of the low-energy physics of a nontrivial scale invariant sector of an effective field theory -- physics that cannot be described in terms of particles. I argue that it is important to take seriously the possibility that the unparticle stuff described by such a theory might actually exist in our world. I suggest a scenario in which some details of the production of unparticle stuff can be calculated. I find that in the appropriate low energy limit, unparticle stuff with scale dimension $d_{\mathcal{U}}$ looks like a non-integral number $d_{\mathcal{U}}$ of invisib…
In this paper, we study the effects of the unparticles on the parity-violating asymmetry for the low energy electron-electron scattering, $e^-e^-\to e^-e^-$. Using the data from the E158 experiment at SLAC we extract the limits on the unparticle coupling $λ_{AV}$, and on the the energy scale $Λ$ at 95% C.L. for various values of the scaling dimension $d$.
We place limits on scalar and vector unparticle couplings to electrons and neutrinos using data from reactor neutrino experiments originally designed to search for neutrino magnetic moment. Upper bounds on Standard Model lepton-scalar unparticle and lepton-vector unparticle couplings $λ_0$, and $λ_1$ are given for various values of the unparticle mass dimension d, and the unparticle energy scale $Λ_{\cal U}$. Especially for smaller values of the mass dimension d (1 <d <1.3) these bounds are very significant and comparable to those obtained from production rates at high energy colliders. These …
The unparticle is proposed by Georgi as a conceptual new physics beyond the standard model to describe the low energy sector of a nontrivial scale invariant sector of an effective theory. We consider the neutrino decay in unparticle scenario and investigate the effect of such decay for the case of ultra high energy neutrinos from GRB. The effect on the detection yield of these neutrinos are also probed for a kilometer scale ice-Cerenkov detector.
An attempt is made to present the influence of the scalar unparticle on some scattering processes in the Randall - Sundum model. The contribution of the scalar unparticle on the production of Higgs - radion at high energy colliders is studied in detail. We evaluate the production cross-sections in the electron-positron ($e^{+}e^{-}$), photon-photon ($γγ$) and gluon-gluon ($gg$) collisions, which depend strongly on the collision energy $\sqrt{s}$, the scaling dimension $d_{U}$ of the unparticle operator $\mathcal{O}_{U}$ and the energy scale $Λ_{U}$. Numerical evaluation shows that the cross - …
The tau is the only known lepton that can decay hadronically. From this class of decays, high precision measurements of several quantities can be extracted: the CKM matrix element $V_{us}$, the mass of the strange quark, etc. Also, as a result of its large variety of decay channels, the study of the tau lepton represents an interesting tool to search for CP violation and other new physics effects. In this work, a spin-0 unparticle is considered and its contributions to the electromagnetic and weak properties of the tau lepton are calculated. It is found that such contributions can be greater t…
We calculate cosmological and astrophysical bounds on the couplings between standard model fields and tensor unparticles. The present day density of tensor unparticles from neutrino-neutrino and photon-photon annihilation is calculated. Also, the supernovae volume energy loss rates from electron-positron and photon-photon annihilation to tensor unparticles are calculated. The constraints from matter density and supernovae volume energy loss rates from photon-photon annihilation are on the same order of magnitude, while the bounds from supernovae volume energy loss rates from electron-positron …
The existence of an unparticle sector, weakly coupled to the standard model, would have a profound impact on supernova (SN) physics. Emission of energy into the unparticle sector from the core of SN1987A would have significantly shortened the observed neutrino burst. The unparticle interaction with nucleons, neutrinos, electrons and muons is constrained to be so weak that it is unlikely to provide any missing-energy signature at colliders. One important exception are models where scale invariance in the hidden sector is broken by the Higgs vacuum expectation value. In this case the SN emission…
An attempt is made to present the contribution of the scalar unparticle on the Z-production cross-section at International Linear Colliders (ILC) with polarized initial beams in the Randall-Sundrum model. The cross-sections depend strongly on the polarization of $e^{-}$, $e^{+}$ initial beams, the center of mass energy $\sqrt{s} $, the scaling dimension $d_{U}$ of the unparticle operator $\mathcal{O}_{U}$ and the energy scale $Λ_{U}$. The results indicate that with the effect of the scalar propagators in the s-channel, including radion, Higgs and scalar unparticle, the cross-section for the ZZ…
We study supersymmetric QCD in the conformal window as a laboratory for unparticle physics, and analyze couplings between the unparticle sector and the Higgs sector. These couplings can lead to the unparticle sector being pushed away from its scale invariant fixed point. We show that this implies that low energy experiments will not be able to see unparticle physics, and the best hope of seeing unparticles is in high energy collider experiments such as the Tevatron and the LHC. We also demonstrate how the breaking of scale invariance could be observed at these experiments.
We have studied the possible signals of unparticle in atomic parity violation(APV) along an isotope chain and in the NuTeV experiment. The effects of unparticle physics could be observed in APV, if the uncertainty in relative neutron/proton radius shift $δ(Δ\frac{R_N}{R_P})$ is less than a few times $10^{-4}$ by measuring the parity violating electron scattering. The constraints imposed by NuTeV experiment on unparticle physics are discussed in detail. If the NuTeV results are confirmed by future experiments, we suggest that unparticle could account for a part of NuTeV anomaly. There exist cer…
The coupling of unparticles to the Standard Model (SM) Higgs boson leads to a breaking of conformal symmetry which produces an effective mass term in the unparticle propagator. Simultaneously, the unparticle couplings to other SM fields produces an effective unparticle decay width via one-loop self-energy graphs. The resulting unparticle propagator then leads to a rather unique appearance for the shape of unparticle resonances that are not of the usual Breit-Wigner variety when they form in high energy collisions. In this paper we explore whether or not such resonances, appearing in the Drell-…
Phenomenology of the notion of an unparticle U, recently perceived by Georgi, to describe a scale invariant sector with a non-trivial infrared fixed point at a higher energy scale is explored in details. Behaving like a collection of d_U (the scale dimension of the unparticle operator O_U) invisible massless particles, this unparticle can be unveiled by measurements of various energy distributions for the processes Z to fermion pair + U and e-e+ to gamma U at e-e+ colliders, as well as mono-jet production at hadron colliders. We also study the propagator effects of the unparticle through the D…
A study of mu-tau conversion via the deep inelastic scattering process μN -> τX, with N a nucleon, is performed taking into account the effects from both spin-0 and spin-1 unparticles with lepton flavor violating (LFV) couplings. This process has attracted attention in the past as it may be at the reach of a future neutrino or muon factory. For the model parameters, we use the most recent constraints on the unparticle LFV couplings from the experimental limits on the muon anomalous magnetic moment and the LFV decay τ-> 3μ, whereas for the unparticle scale Λ_U and scale dimension d_U we use the…
We investigate the impact of unparticle physics on the annihilation of relic neutrinos with the neutrinos identified as primary source of ultra high energy (UHE) cosmic ray events, producing a cascade of photons and charged particles. We compute the contribution of the unparticle exchange to the cross-sections $ν\barν\toγγ$ and $ν\barν\to f \bar f$ scattering. We estimate the neutrino photon decoupling temperature from the reaction rate of $ν\barν\toγγ$. We find that inclusion of unparticles can in fact account for the flux of UHE cosmic rays and can also result in the lowering of neutrino - p…
We investigate the single top quark production with the exchange of unparticles through high energy photon-photon collision $γγ\to t \bar c$. The effects of unparticles on the scattering cross sections for different polarization configurations, and for various values of the scaling dimension $d, 1<d<2$ are analysed. It is shown that the $(+-)$ polarisation configuration is more preferable searching for unparticle physics signatures.
Interest has been directed recently towards low energy implications of a non-trivial conformal sector of an effective field theory with an IR fixed point (Λ), manifest in terms of ``unparticles'' with bizarre properties. We re-examine the implications of the limits on decay lifetimes of solar neutrinos for unparticle interactions. We study in detail the fundamental parameter space (Λ, M) and derive bounds on the energy scale M characterizing the new physics. We work strictly within the framework where conformal invariance holds down to low energies. We first assume that couplings of the unpart…
Unparticles ($\U$) interact weakly with particles. The direct signature of unparticles will be in the form of missing energy. We study constraints on unparticle interactions using totally invisible decay modes of $Z$, vector quarkonia $V$ and neutrinos. The constraints on the unparticle interaction scale $Λ_\U$ are very sensitive to the dimension $d_\U$ of the unparticles. From invisible $Z$ and $V$ decays, we find that with $d_\U$ close to 1 for vector $\U$, the unparticle scale $Λ_\U$ can be more than $10^4$ TeV, and for $d_\U$ around 2, the scale can be lower than one TeV. From invisible ne…
Recently H. Georgi suggested that a scale invariant unparticle ${\mathcal{U}}$ sector with an infrared fixed point at high energy can couple with the SM matter via a higher-dimensional operator suppressed by a high cut-off scale. Intense phenomenological search of this unparticle sector in the collider and flavour physics context has already been made. Here we explore it's impact in cosmology, particularly it's possible role in the supernovae cooling. We found that the energy-loss rate (and thus the cooling) is strongly dependent on the effective scale \LdaU and the anomalous dimension \dU of …
We consider a scenario where ultra high energy neutrinos undergo unparticle decay during its passage from its cosmological source to Earth. The idea of unparticle had been first proposed by Georgi by considering the possible existence of an unknown scale invariant sector at high energies and the unparticles in this sector manifest itself below a dimensional transmutation scale $Λ_{\cal U}$. We then explore the possible signature of such decaying neutrinos to unparticles at a square kilometer detector such as IceCube.
The decay of the standard model Higgs boson into a single photon and a vector unparticle through a one-loop process is studied. For an intermediate mass Higgs boson, this single photon plus unparticle mode can have a branching ratio comparable with the two-photon discovery mode. The emitted photon has a continuous energy spectrum encoding the nature of the recoil unparticle. It can be measured in precision studies of the Higgs boson after its discovery.
We construct a model of an unparticle sector consisting of a supersymmetric SU(N) gauge theory with the number of flavors in the Seiberg conformal window. We couple this sector to the MSSM via heavy messengers. The resulting low energy theory has a Higgs coupling to unparticles. The Higgs vev drives the hidden Seiberg sector to a new conformal fixed point. The coupling to the Higgs mediates supersymmetry breaking to the Seiberg sector, and breaks conformal invariance at a lower scale. The low energy theory contains light stable and metastable mesons. Higgs decay into this sector gives signatur…
Recently H. Georgi has introduced an unparticle $\unpart$ in order to describe the low energy physics of a nontrivial scale invariant sector of an effective theory. In this work we have explored the phenomenology of an unparticle using the lepton flavour violating decay $μ^{-}\to e^{-} e^{+} e^{-}$, and found that the branching ratio of this decay is strongly dependent on the scaling dimension.
We investigate the potential of $γγ$ collisions to probe scalar unparticle couplings via top-antitop quark pair production. We find 95% confidence level limits on the unparticle couplings with an integrated luminosity of $500 fb^{-1}$ and $\sqrt{s}=1$ TeV energy. We investigate the effect of top quark spin polarization on the unparticle couplings. It is shown that spin polarization of the top quark leads to a significant improvement in the sensitivity limits.
Low energy phenomenology of the unparticle physics associated with an exact scale invariant sector possessing a non-trivial infrared fixed point at a higher energy scale is explored for both electron-positron and hadronic colliders. Feynman rules for a spin 0, 1 or 2 unparticle coupled to a variety of standard model gauge invariant operators that are relevant to many low energy processes involving either real emissions of unparticles or their virtual propagator effects are presented. Missing energy and/or recoil mass distributions of the unparticle in the associated production of unparticle to…
We investigate the effects of unparticles on Compton scattering, e gamma -> e gamma based on a future e^+e^- linear collider such as the CLIC. For different polarization configurations, we calculate the lower limits of the unparticle energy scale Lambda_U for a discovery reach at the center of mass energies sqrt(s)=0.5 TeV- 3 TeV. It is shown that, especially, for smaller values of the mass dimension d, (1 <d <1.3), and for high energies and luminosities of the collider these bounds are very significant. As a stringent limit, we find Lambda_U>80 TeV for d<1.3 at sqrt(s)=3 TeV, and 1 ab^(-1) in…
The updated CDF measurement of the forward-backward asymmetry (FBA) in the top quark production p{bar p} -> t{bar t} at Tevatron (with the CMS energy 1.96 TeV) shows a deviation of 2*sigma from the value predicted by the Standard QCD Model. We present calculation of this quantity in the scenario where colored unparticle physics contributes to the s-channel of the process, and obtain the regions in the plane of the unparticle parameters lambda and dU which give the values of the FBA and of the total t{bar t} production cross section compatible with the present measurements.
Unparticles from hidden conformal sectors provide qualitatively new possibilities for physics beyond the standard model. In the theoretical framework of minimal models, we clarify the relation between energy scales entering various phenomenological analyses. We show that these relations always counteract the effective field theory intuition that higher dimension operators are more highly suppressed, and that the requirement of a significant conformal window places strong constraints on possible unparticle signals. With these considerations in mind, we examine some of the most robust and sensit…
Unparticle $\U$ with scaling dimension $d_\U$ has peculiar thermal properties due to its unique phase space structure. We find that the equation of state parameter $ω_\U$, the ratio of pressure to energy density, is given by $1/(2d_\U +1)$ providing a new form of energy in our universe. In an expanding universe, the unparticle energy density $ρ_\U(T)$ evolves dramatically differently from that for photons. For $d_\U >1$, even if $ρ_\U(T_D)$ at a high decoupling temperature $T_D$ is very small, it is possible to have a large relic density $ρ_\U(T^0_γ)$ at present photon temperature $T^0_γ$, lar…
In the present work we study the effect of unparticle modified static potentials on the energy levels of the hydrogen atom. By using Rayleigh-Schrödinger perturbation theory, we obtain the energy shift of the ground state and we compare it with experimental data. Bounds on the unparticle energy scale $Λ_\mathcal{U}$ as a function of the scaling dimension $d_\mathcal{U}$ and the coupling constant $λ$ are derived. We show that there exists a parameter region where bounds on $Λ_\mathcal{U}$ are stringent, signalling that unparticles could be tested in atomic physics experiments.
We perform a global fit on parity-conserving electron-quark interactions via spin-1 unparticle exchange. Besides the peculiar features of unparticle exchange due to non-integral values for the scaling dimension d_U and a non-trivial phase factor exp (-id_U π) associated with a time-like unparticle propagator, the energy dependence s^{-2 + d_U} of the unparticle contributions in the scattering amplitudes are also taken into account. The high energy data sets taken into consideration in our analysis are from (1) deep inelastic scattering at high Q^2 from ZEUS and H1, (2) Drell-Yan production at …
We examine a dark energy model where a scalar unparticle degree of freedom plays the role of quintessence. In particular, we study a model where the unparticle degree of freedom has a standard kinetic term and a simple mass potential, the evolution is slowly rolling and the field value is of the order of the unparticle energy scale ($λ_u$). We study how the evolution of $w$ depends on the parameters $B$ (a function of the unparticle scaling dimension $d_u$), the initial value of the field $ϕ_i$ (or equivalently, $λ_u$) and the present matter density $Ω_{m0}$. We use observational data from Typ…
We consider unparticle inspired corrections of the type ${(\frac{R_{G}}{r})}^β$ to the Newtonian potential in the context of the gravitational quantum well. The new energy spectrum is computed and bounds on the parameters of these corrections are obtained from the knowledge of the energy eigenvalues of the gravitational quantum well as measured by the GRANIT experiment.
In a new measurement on neutrino oscillation $ν_μ\toν_e$, the MiniBooNE Collaboration observes an excess of electron-like events at low energy and the phenomenon may demand an explanation which obviously is beyond the oscillation picuture. We propose that heavier neutrino $ν_2$ decaying into a lighter one $ν_1$ via the transition process $ν_μ\to ν_e+X$ where $X$ denotes any light products, could be a natural mechanism. The theoretical model we employ here is the unparticle scenario established by Georgi. We have studied two particular modes $ν_μ\to ν_e+\Un$ and $ν_μ\to ν_e+\barν_e+ν_e$. Unfort…
Unparticles as suggested recently by Georgi have surprising phenomenological implications, distinctive from any other new physics that we know of. But they must interact very feebly with ordinary matter to have avoided detection thus far. We determine how feebly they can interact with the electron, using the precisely measured quantities in QED: the electron g-2 and the bounds on invisible and exotic positronium decays. The most stringent bound comes from invisible ortho-positronium decays: the effective energy scale entering the vector unparticle-electron interaction must exceed 4 x 10^5 TeV …
Modern theoretical models strongly suggest that new phenomena await discovery above the energy scale of the Standard Model (SM) of particle interactions. In this paper we argue that correct description of particle physics in the TeV energy scale needs to account for degrees of freedom obeying the conformal (or scale) invariance. In this respect, the existing of Georgi's unparticles is strongly argued. We present the gauge model of scalar unparticles. The ground state of scalar unparticles in the continuum is restricted by the vacuum expectation value of the SM Higgs boson and the scale dimensi…
In a recent paper \cite{Artymowski:2020zwy} we suggested the possibility that the present acceleration of the Universe is due to thermodynamical behavior of unparticles. The model is free of scalar fields, modified gravity, a Cosmological Constant (CC), the coincidence problem, initial conditions problem and possesses interesting distinct predictions regarding the equation of state of Dark Energy, the growth rate and the number of relativistic degrees of freedom at BBN and CMB decoupling. In this work, we relate to a recent paper \cite{Abchouyeh:2021wey}, which discusses a similar setup of unp…
In this paper we present the un-Casimir effect, namely the study of the Casimir energy in the presence of an unparticle component in addition to the electromagnetic field contribution. The distinctive feature of the un-Casimir effect is a fractalization of metallic plates. This result emerges through a new dependence of the Casimir energy on the plate separation that scales with a continuous power controlled by the unparticle dimension. As long as the perfect conductor approximation is valid, we find bounds on the unparticle scale that are independent of the effective coupling constant between…
A limiting temperature of a species can cause the Universe to asymptote to it yielding a deSitter (dS) phase due to macroscopic emergent behavior. The limiting temperature is generic for theories slightly shifted from their conformal point. We demonstrate such behavior in the example of unparticles/Banks-Zaks theory. The unparticles behave like radiation at high energies reducing the Hubble tension, and a cosmological constant (CC) at low energies yielding a model that follows closely ΛCDM model but due to collective phenomenon. It is technically natural and avoids the no-dS conjecture. The mo…
We study the effects of fermiophobic scalar/pseudo-scalar oblique corrections on bound state energy levels in muonic atoms. To make the treatment sufficiently general we will consider Unparticle scalars/pseudo-scalars which couple only to photons. We derive the relevant vacuum polarization functions and comment on the functional forms of the Unparticle Uehling potentials for various scaling dimensions in the point nucleus and finite nucleus approximations. It is estimated that for an infra-red fixed point near the scale of electroweak symmetry breaking, in the low TeV range, the energy shifts …
Addressing the discrepancy between the late and early time measurements of the Hubble parameter, $H_0$, and the so-called $S_8$ parameter has been a challenge in precision cosmology. Several models are present to address these tensions, but very few of them can do so simultaneously. In the past, we have suggested Banks-Zaks/Unparticles as an emergent Dark Energy model and claimed that it can ameliorate the Hubble tension. In this work, we test this claim and perform a likelihood analysis of the model and its parameters are given current data and compare it to $Λ$CDM. The model offers a possibl…
We explore the influence of new physics on extremely high energy cosmic ray (EXCER) particles. In particular, we devote our mind to one example of new physics, unparticle stuff, on one specific process that EXECRs participate in, photopion production of the EXECR nucleon with 2.7K cosmic microwave background radiation (CMBR). Through computing the differential cross section of virtual exchange of unparticle in the $p+γ\to p+ π^0$ process, we acquire the general consequence of new physics on the EXECR propagation. It is astonishing but reasonable that due to the lowness of interaction energy $\…
Searches for supersymmetry (SUSY) often rely on a combination of hard physics objects (jets, leptons) along with large missing transverse energy to separate New Physics from Standard Model hard processes. We consider a class of ``double-invisible'' SUSY scenarios: where squarks, stops and sbottoms have a three-body decay into two (rather than one) invisible final-state particles. This occurs naturally when the LSP carries an additional conserved quantum number under which other superpartners are not charged. In these topologies, the available energy is diluted into invisible particles, reducin…
We explore a novel method of mass reconstruction in events with missing transverse momentum at hadron colliders. In events with sizeable boost factors in the final steps of dual multi-stage decay chains, the missing energy particles may each be approximately collinear with a visible standard model particle, spanning a narrow "MET-cone." We exploit this collinear approximation, when applicable, to reconstruct the masses of exotica.
Missing energy signals such as monojets are a possible signature of Dark Matter (DM) at colliders. However, neutrino interactions beyond the Standard Model may also produce missing energy signals. In order to conclude that new "missing particles" are observed the hypothesis of BSM neutrino interactions must be rejected. In this paper, we first derive new limits on these Non-Standard neutrino Interactions (NSIs) from LHC monojet data. For heavy NSI mediators, these limits are much stronger than those coming from traditional low-energy $ν$ scattering or $ν$ oscillation experiments for some flavo…
Final states with leptons, jets and missing transverse energy are a promising way to detect Supersymmetry at the Large Hadron Collider. Results of simulation studies performed by the CMS and ATLAS collaborations are presented. The discovery of new physics is shown to be possible within the first fb^-1 of collected integrated luminosity.
Many beyond the Standard Model theories include a stable dark matter candidate that yields missing / invisible energy in collider detectors. If observed at the Large Hadron Collider, we must determine if its mass and other properties (and those of its partners) predict the correct dark matter relic density. We give a new procedure for determining its mass with small error.
WIMPless dark matter offers an attractive framework in which dark matter can be very light. We investigate the implications of such scenarios on invisible decays of bottomonium states for dark matter with a mass less than around $5 {\rm GeV}$. We relate these decays to measurements of nucleon-dark matter elastic scattering. We also investigate the effect that a coupling to $s$ quarks has on flavor changing $b\to s$ processes involving missing energy.
I will briefly discuss the signatures and discovery prospects of several new physics models containing dark matter candidates at future lepton colliders. In particular, I will discuss the two models that, among other signatures, lead to electroweak gauge bosons and missing energy: the Inert Doublet Model, as well as the THDMa, a two Higgs doublet model with an additional pseudoscalar that serves as a portal to the dark sector. Results are mainly based on a Snowmass Whitepaper arXiv:2203.07913
The H1 collaboration has recently reported the observation of events with an isolated high energy lepton and missing transverse momentum. All analysed Standard Model processes were found to fail in explaining the origin of muon events leaving a statistical fluctuation as the only explanation of their appearance. In this paper I discuss mechanisms by which Standard Model processes could either produce or mimic such events and point out several biases of the H1 analysis which led to an underestimation of their contribution.
