We study an extension of the Standard Model (SM) in which two copies of the SM-Higgs doublet which do not acquire a vacuum expectation value, and hence are {\it inert}, are added to the scalar sector. The lightest particle from the inert sector, which is protected from decaying to SM particles through the conservation of a $Z_2$ symmetry, is a viable dark matter candidate. We allow for CP-violation in this extended dark sector and evaluate the $ZZZ$ vertex and its CP-violating form factor in several benchmark scenarios. We provide collider signatures of this dark CP-violation in the form of potentially observable asymmetries and cross sections for the $f\bar f\to Z^*\to ZZ$ process at both leptonic and hadronic machines.
Lepton flavor violation at linear collider experiments is discussed. We show that detectable lepton flavor violation could occur through scalar lepton pair production and decay in the supersymmetric SU(5) grand unified theory in spite of the stringent present experimental constraints by rare process searches. Possible cross sections about 40fb for an e+e- collider and 280fb for an e-e- collider are illustrated.
We present a comprehensive analysis on the MSSM Higgs sector CP violation at photon colliders including the chargino contributions as well as the contributions of other charged particles. The chargino loop contributions can be important for the would-be CP odd Higgs production at photon colliders. Polarization asymmetries are indispensable in determining the CP properties of neutral Higgs bosons.
A brief review of the strategies used in looking for CP violation in B decays is presented. Some problems due to penguin diagrams are addressed. Penguin trapping is discussed, in the context of the upcoming experiments. The high rates and the possibility to perform experiments on the $B_s$ system justify the interest in hadronic colliders.
By assuming a dynamical source of CP violation, the tension between sufficient CP violation for successful electroweak baryogenesis and strong constraints from current electric dipole moment measurements could be alleviated. We study how to explore such scenarios through gravitational wave detection, collider experiments, and their possible synergies with a well-studied example.
The general production {\it and} decay mechanism of $\ttbar$ in future high-energy $\epem$ colliders has been investigated in a model-independent way, focusing on an observation of possible CP violation. Angular asymmetries sensitive to CP violation either in the production {\it or} in the subsequent decays have been found. General considerations are illustrated through 1-loop effects induced by gluino exchange in the supersymmetric version of the Standard Model.
A muon collider would be a powerful probe of flavor violation in new physics. There is a strong complementary case for collider measurements and precision low-energy probes of lepton flavor violation (as well as CP violation). We illustrate this by studying the collider reach in a supersymmetric scenario with flavor-violating slepton mixing. We find that the collider could discover sleptons and measure the slepton and neutralino masses with high precision, enabling event reconstruction that could cleanly separate flavor-violating new physics signals from Standard Model backgrounds. The discove…
Parity violation induced by the chromo-anapole form factor of the bottom quark, generated from weak corrections, is studied in polarized hadron collisions. The forward-backward asymmetry in the bottom quark pair production at polarized $pp$ and $p\bar{p}$ colliders is evaluated in the Standard Model and in a Two Higgs Doublet Model to examine the effects of parity violation. In the models studied, promising results are found for polarized $p\bar{p}$ colliders.
To explore the discovery possibilities of a high-energy muon-proton collider, we examine signals that could arise from direct-channel formation of supersymmetric-particle resonances through operators that do not respect R-parity.
We present an outlook for possible R-parity violating SUSY search at gamma-proton and gamma-electron colliders. Single production of third generation slepton/sneutrino through the lambda'-ijk couplings at a gamma-p collider is investigated and compared with the results of the resonant sfermion productions at the existing colliders. Also single sneutrino production at a future gamma-electron collider through the lambda(ijk) couplings is disussed.
The prospects of experimental detection of $CP$ violation at $e^+e^-$ and $pp/p\overline{p}$ colliders are reviewed. After a general discussion on the quantities which can measure $CP$ violation and on the implications of the $CPT$ theorem, various possibilities of measuring $CP$ violation arising outside the standard model are taken up. $CP$ violation in leptonic processes, especially polarization effects in $e^+e^-\rightarrow l^+l^-$ are discussed next. $CP$ violation in $t\overline{t}$ and $W^+W^-$ production and decay is also described. (Based on talk presented at the WHEPP3, Madras, Janua…
In this review we demonstrate physics potential of a photon linear collider by studying the neutral Higgs-boson sector of the MSSM in which interesting CP-violating Higgs mixing could arise via radiative corrections.
A muon collider with controllable energy resolution and transverse beam polarization provides a powerful probe of the Higgs sector in the minimal supersymmetric standard model with explicit CP violation, through s-channel production of Higgs bosons. The production rates and the CP-even and CP-odd transverse-polarization asymmetries are complementary in diagnosing CP violation in the Higgs sector.
A future linear e+e- collider with a clean environment, tunable collision energy, high luminosity, polarized incoming beams, and additional e-e-, e-gamma and gamma-gamma modes, will offer precision tools to explore new physics. Here we summarize three papers submitted to the ICHEP04 conference in which polarized e+e- and gamma-gamma beams are exploited to search for CP violation, and universal extra dimensions (UED).
CP violations in B meson decays at hadron colliders are reviewed. In particular I examine: $B^0-\bar{B^0}$ mixing and oscillations within Standard Model and the Cabibbo-Kobayashi-Maskawa picture for CP violations; $B^0$ decays into CP eigenstates and the measurements of the angles in the unitarity triangle; finally I consider a class of charged $B$ decays that allow to avoid uncertainties arising from the computation of hadronic matrix elements.
CP violating asymmetries in both the production and the decays of $s$-channel neutral Higgs bosons at $μ^+μ^-$ colliders can be large. If the CP violation occurs in the muon-Higgs coupling, one observes a production asymmetry with transversely polarized $μ^+μ^-$ beams. Likewise if the CP violation occurs in the top-Higgs or $τ$-Higgs coupling, one observes an azimuthal decay asymmetry in $μ^+μ-\to t\bar t$ (or $τ^+τ^-$). CP studies at such colliders allow a uniquely clean way of deducing the underlying CP phases; in turn these parameters would significantly improve our understanding of baryoge…
CP violation in the decays $t \to \ell^+νb$ and $\bar t \to \ell^-\barν\bar b$ from the production process $e^-e^+ \to \ttbar$ is discussed. Since the asymmetry proposed as a measure of CP violation vanishes even at the one-loop level in the Standard Model (SM), it may be a useful tool to search for sources of CP violation outside of the SM. As an illustration the asymmetry has been computed within supersymmetric extensions of the SM. Prospects for its measurement at future high-energy linear colliders are discussed.
Supersymmetric theories generally have new flavor and CP violation sources in the squark and slepton mass matrices. They will contribute to the lepton flavor violation processes, such as $μ\to e γ$, which can be probed far below the current bound with an intense muon source at the front end of the muon collider. In addition, if sleptons can be produced at the muon collider, the flavor violation can occur at their production and decay, allowing us to probe the flavor mixing structure directly. Asymmetry between numbers of $μ^+ e^-$ and $e^+ μ^-$ events will be a sign for CP violation in supersy…
In supersymmetric extensions of the Standard Model, the lepton flavour violation (LFV) is closely related to the structure of slepton masses and mixing. Allowing for the most general flavour structure of the slepton sector, consistent with the experimental limits on rare lepton decays, large and distinct signals of LFV at future colliders can be expected. A case study of mixing of second and third generation of sleptons at an e+e- collider is presented and compared to that of tau to mu+gamma rare decay.
We investigate simplified models involving an inert scalar triplet and vector-like leptons that can account for the muon $g-2$ anomaly. These simplified scenarios are embedded in a model that features W' and Z' bosons, which are subject to stringent collider bounds. The constraints coming from the muon $g-2$ anomaly are put into perspective with collider bounds, as well as bounds coming from lepton flavor violation searches. The region of parameter space that explains the $g-2$ anomaly is shown to be within reach of lepton flavor violation probes and future colliders such as HL-LHC and HE-LHC.
We argue that CP--violation effects below a few tenths of a percent are probably undetectable at hadron and electron colliders. Thus only operators whose contributions interfere with tree--level Standard Model amplitudes are detectable. We list these operators for Standard Model external particles and some two and three body final state reactions that could show detectable effects. These could test electroweak baryogenesis scenarios.
This paper investigates a signature of Lorentz invariance violation with the $t\bar{t}$ production at the LHC and future hadron colliders. Possible deviations from the Lorentz symmetry remain poorly constrained in the top quark sector. With a dedicated analysis of $t\bar{t}$ events produced at the LHC, bounds in the top sector can be improved by up to three orders of magnitude relative to Tevatron, the only measurement existing so far. The sensitivity will be even further enhanced at the HL-LHC and future colliders.
The CP properties of Higgs bosons can be probed through their s-channel resonance productions via photon-photon collisions by use of circularly and/or linearly polarized backscattered laser photons at a TeV-scale linear e^+ e^- collider. Exploiting this powerful tool, we investigate in detail the Higgs sector of the minimal supersymmetric Standard Model with explicit CP violation.
Lorentz violation has been a popular field in recent years in the search for new physics beyond the Standard Model. We present a general method to build all Lorentz-violating terms in gauge field theories, including ones involving operators of arbitrary mass dimension. Applying these results to two types of experiments in high-energy colliders, light-by-light scattering and deep-inelastic scattering, we extract first bounds on certain coefficients for Lorentz violation.
We discuss several manifestations of charged lepton flavour violation at high energies. Focusing on a supersymmetric type I seesaw, considering constrained and semi-constrained supersymmetry breaking scenarios, we analyse different observables, both at the LHC and at a future Linear Collider. We further discuss how the synergy between low- and high-energy observables can shed some light on the underlying mechanism of lepton flavour violation.
We consider single charged Higgs ($H^{\pm}$) production in association with a $W^{\pm}$ boson at $μ^+μ^-$ colliders, in the context of the general CP violating Two Higgs Doublet Model (2HDM). We find that large cross-sections for the processes $μ^+μ^-\to H^+W^-,H^-W^+$ are possible, and offer an attractive way of producing $H^{\pm}$ at $μ^+μ^-$ colliders. The difference in the cross-sections for $H^+W^-$ and $H^-W^+$ may exceed 1000 fb, and this represents a novel way of probing CP violation in the Higgs sector.
We present a study of loop-level lepton flavor vioalting signals in models with heavy Majorana neutrinos and in the supersymmetric extension of the standard model. The attention is focused to the $e^- e^-$ option of the next generation of linear colliders and its potential of discovering new physics is emphasized.
The lepton or baryon number violating top quark interactions in the supersymmetric standard model with R parity violation contribute to the process d dbar to t tbar at the tree level via the t- or u-channel sfermion exchange. Since these interactions are chiral, they induce polarization to the top quark in the t tbar events at hadron colliders. We show in this article that the polarization can be a useful observable for probing these interactions at the upgraded Fermilab Tevatron collider, because the polarization is expected to be very small in the standard model.
In supersymmetric models with R-parity violating interactions, sneutrinos may be produced as $s$-channel resonances at $μ^+ μ^-$ colliders. We demonstrate that, for R-parity violating couplings as low as $10^{-4}$, sneutrinos can be discovered and their couplings measured to high accuracy. The excellent beam energy resolution of muon colliders is found to be especially useful for studying such resonances in certain cases.
The observation of lepton flavor violation indicates new physics beyond the Standard Model. Lepton colliders are ideal facilities to probe charged lepton flavor violation (CLFV) signals induced by new physics at high energy. In this work we perform a comprehensive study of the sensitivity of future lepton colliders to charged lepton flavor violation. We consider the most general renormalizable Lagrangian coupling two leptons to new bosonic particles, involving both $ΔL=0$ and $ΔL=2$ interactions. The CLFV processes are introduced by the exchange of off-shell new particles at tree-level. We fin…
In the framework of models with R-parity violation, scalar neutrinos and scalar leptons production in the processes $l_i^+l_j^-\to\tilde ν_{k,L} Z^0$ and $l^+_il^-_j\to \tilde{l}^{\mp}_{k,L}W^{\pm}$ is considered.We also consider within the Minimal Supersymmetric Standard Model Higgs bosons production in the processes $μ^+μ^-\toH_i^0Z^0$, $μ^+μ^-\to H^{\pm}W^{\mp}$.
We investigate the effects of R-parity-violating $LL\bar E$ and $LQ\bar D$ operators on the production of fermion pairs at a $μ^+ μ^-$ collider with high energy and luminosity. We show that comparison of angular distributions leads to useful discovery limits for the R-parity-violating couplings, especially if the exchanged sfermions turn out to be heavy. Products of these couplings can also be probed well beyond present experimental limits, especially for the second and third generations. Finally, we compare results at a muon collider with those obtainable from an $e^+ e^-$ linear collider wit…
We study the phenomenological implications of the Higgs sector CP violation at a photon collider. In our model, the CP violation is radiatively induced by the non-trivial CP phases of the third-generation scalar-quark sector in the MSSM. We re-evaluate the $s$-channel resonance production cross sections and the polarization asymmetries of the neutral Higgs bosons based on the calculation of the mass matrix of the neutral Higgs bosons which is valid for any values of the relevant SUSY parameters. The CP properties of the Higgs bosons can be precisely probed through their $s$-channel resonance p…
Supersymmetric theories with significant lepton flavor violation have $\tilde{e}$ and $\tildeμ$ nearly degenerate. In this case, pair production of $\tilde{e}^+ \tilde{e}^-$ and $\tildeμ^+ \tildeμ^-$ at LEPII and at the Next Linear Collider leads to the phenomenon of slepton oscillations, which is analogous to neutrino oscillations. The reach in $Δm^2$ and $\sin^2 2 θ$ gives a probe of lepton flavor violation which is significantly more powerful than the current bounds from rare processes, such as $μ\to eγ$. Polarizable $e^-$ beams and the $e^-e^-$ mode at the NLC are found to be promising opt…
Hadron colliders are providing a unique opportunity for testing Lorentz invariance and CPT symmetry at high energy and in a laboratory. A first measurement in the top-quark sector was performed at the Tevatron. We present here prospective studies for testing Lorentz invariance in top-quark pair production at the LHC and future colliders. The b-quark sector was investigated recently at LHCb. Eventually, new bounds on photon parameters can be extracted from the observation of TeV photons at the LHC. We will conclude by highlighting other opportunities provided by hadron colliders.
We consider a general two-Higgs-doublet model with CP violation in the scalar sector. Three neutral Higgs fields of the model all mix and the resulting physical Higgs bosons have no definite CP properties. That leads, at the one-loop level of the perturbation expansion, to CP-violating form factors for gamma-t-tbar, Z-t-tbar and W-t-b interaction vertices. We discuss asymmetries sensitive to CP violation induced by the form factors for the process e^+ e^- -> t tbar -> l^\pm ... and e^+ e^- -> t tbar -> b/bbar ... at future linear e+ e- colliders.
In supersymmetric models with R-parity violation, sneutrinos may be produced as s-channel resonances at muon colliders. We demonstrate that, for R-parity violating couplings as low as 10^-4, sneutrino resonances may be observed and may be exploited to yield high precision SUSY parameter measurements. The excellent beam energy resolution of muon colliders may also be used to resolve MeV level splittings between CP-even and CP-odd sneutrino mass eigenstates.
In the presence of Lorentz violation, the motion of a charged particle in a magnetic field is distorted. By measuring the eccentricities of particles' elliptical orbits and studying how those eccentricities vary with the absolute orientation of the laboratory, it is possible to constrain the Lorentz-violating c_JK parameters. For each observed species, this method can provide constraints on four linear combinations of coefficients for which, in some species, there are presently no two-sided bounds.
The notion that dark matter and standard-model matter are connected through flavor implies a generic collider signature of the type 2 jets + $μ^\pm$ + $e^\mp$ + missing energy. We discuss the theoretical basis of this proposal and its verifiability at the Large Hadron Collider.
We discuss possibilities of measuring CP violation in the Two-Higgs-Doublet Model by studying effects of one-loop generated $ZZZ$ and $ZWW$ vertices. We discuss a set of CP-sensitive asymmetries for $ZZ$ and $W^+W^-$ production at linear $e^+e^-$-colliders, that directly depends on the weak-basis invariant Im $J_2$ that parametrises the strength of CP violation. Given the restrictions on this model that follow from the LHC measurements, the predicted effects are small. Pursuing such measurements is however very important, as an observed signal might point to a richer scalar sector.
We analyze the prospects of observing lepton flavour violation in future e-e- and e+e- linear colliders in scenarios where the gravitino is the lightest supersymmetric particle, and the stau is the next-to-lightest supersymmetric particle. The signals consist of multilepton final states with two heavily ionizing charged tracks produced by the long-lived staus. The Standard Model backgrounds are very small and the supersymmetric backgrounds can be kept well under control by the use of suitable kinematical cuts. We discuss in particular the potential of the projected International Linear Collide…
In the framework of minimal flavor violation (MFV), we discuss the decay properties of a supersymmetric scalar top (stop) in the presence of a light gravitino. Given a small mass difference between the lighter stop and lightest neutralino and an otherwise sufficiently decoupled spectrum, the stop may be long-lived and thus can provide support to MFV at hadron colliders. For a bino-like lightest neutralino, we apply bounds from searches in the gamma gamma plus missing transverse energy channel (ATLAS with 1 fb^-1 and D0 with 6.3 fb^-1) and give a 5 fb^-1 projection for the ATLAS search.
A detailed, model-independent study of CP violation at present and future electron-positron colliders is reported. Firstly, we investigate CP violation effects in $W$ boson and $t$ quark pair production in $e^+e^-$ annihilation and in two-photon fusion at a next $e^+e^-$ linear collider, where Compton-backscattered laser light off the electrons or positrons are employed as a powerful polarized photon source. Secondly, noting that there do not exist any direct measurements for the tau-lepton electric dipole moment (EDM), we address the importance of performing its direct measurements at $e^+e^-…
The leading weak corrections to the production of top quark pairs via $q\bar{q} \to t\bar{t}$ in $p\bar{p}$ collisions are evaluated. The chromo-anapole form factor of the top quark and effects of parity violation are studied in the Standard Model (SM) and the Minimal Supersymmetric Model (MSSM). The parity violation effect in $q\bar{q} \to g \to t\bar{t}$ from the SM weak corrections is found to be very small. In the MSSM, the effects of parity violation can be enhanced for $\tanβ\equiv v_2/v_1 > \sqrt{m_t/m_b}$.
Several supersymmetric models with extended gauge structures predict light doubly-charged Higgsinos. Their distinctive signature at the large hadron collider is highlighted by studying their production and decay characteristics.
The model-independent determination of the Higgs-boson CP properties at the Photon Collider at TESLA has been studied in detail, for masses between 200 and 350 GeV, using realistic luminosity spectra and detector simulation. We consider a generic model with the CP violating Higgs tensor couplings to gauge bosons. We introduce a new variable describing angular distributions of the secondary WW and ZZ decay products which is very sensitive to the CP properties of the Higgs-boson. Understanding of the detector performance turns out to be crucial, as the influence of the acceptance corrections is …
We proposed the spontaneous CP-violation in the Simplest Little Higgs model. In this model, the pseudoscalar field can acquire a nonzero vacuum expected value. It leads to a mixing between the two scalars with different CP-charge, which means spontaneous CP-violation happens. It is also a connection between composite Higgs mechanism and CP-violation. Facing the experimental constraints, the model is still alive for both scenarios in which the extra scalar appears below or around the electro-weak scale. We also discussed the future collider tests on CP-violation in the scalar sector through mea…
The observation of charged lepton flavor violation is a clear sign of physics beyond the Standard Model (SM). In this work, we investigate the sensitivity of future lepton colliders to charged lepton flavor violation via on-shell production of bileptons, and compare their sensitivity with current constraints and future sensitivities of low-energy experiments. Bileptons couple to two charged leptons with possibly different flavors and are obtained by expanding the general SM gauge invariant Lagrangians with or without lepton number conservation. We find that future lepton colliders will provide…
We investigate a potential of discovering lepton flavor violation (LFV) at the Large Hadron Collider. A sizeable LFV in low energy supersymmetry can be induced by massive right-handed neutrinos, which can explain neutrino oscillations via the seesaw mechanism. We investigate a scenario where the distribution of an invariant mass of two hadronically decaying taus ($\tauh\tauh$) from $\schizero{2}$ decays is the same in events with or without LFV. We first develop a transfer function using this ditau mass distribution to model the shape of the non-LFV $\tauhμ$ invariant mass. We then show the fe…
The occurrence of a significant amount of supersymmetric lepton flavour violation at laboratory energies, through $\tildeν_μ- \tildeν_τ$ mixing, has become a realistic possibility in the wake of the super-Kamiokande atmospheric neutrino result. This effect can be observed in an e+e- linear collider with the distinct final state tau+mu+ jets+E_T. We show that the pair production of charginos can make an important contribution to this process and has to be taken into account in addition to that of sneutrinos or charged sleptons. Some case studies are presented with CM energies of 500 and 800 GeV…
We discuss signals for CP-violation in $μ^+ μ^- \to \tilde τ_i^- \tilde τ_j^+$, where $i,j = 1,2$ label the two scalar $τ$ mass eigenstates. We assume that these reactions can proceed through the production and decay of the heavy neutral Higgs bosons present in supersymmetric models. CP-violation in the Higgs sector can be probed through a rate asymmetry even with unpolarized beams, while the CP-odd phase associated with the $\tilde τ$ mass matrix can be probed only if the polarization of at least one beam can be varied. These asymmetries might be ${\cal O}(1)$.
Angular and energy distributions for leptons and bottom quarks in the process e+e- --> t tbar --> l/b ... have been calculated assuming the most general top-quark couplings. The double distributions depend both on modification of the top-quark production and tbW decay vertices. However, the leptonic angular distribution turned out to be insensitive to non-standard parts of tbW vertex. The method of optimal observables have been used to estimate sensitivity of future measurements at linear e+e- colliders
We investigate a possible CP violating effect in $e^+e^-$ annihilation into $t\bar t$ top quark pairs. As an illustrative example, we assume the source of the CP nonconservation is in the Yukawa couplings of a neutral Higgs boson which contain both scalar and pseudoscalar pieces. One of the interesting observable effects is the difference in production rates between the two CP conjugate polarized $t\bar t$ states.
A R-parity breaking SUSY model characterized by an effective bilinear violation with only $τ$-lepton number breaking in the superpotential is outlined. The CP-odd Higgs boson masses and those of charged Higgs bosons are discussed. In the model, several interesting mass mixings else such as the mixing between $τ$ lepton and charginos etc in the model are discussed too. Being one of example, we have computed the mixing production $e^{+} e^{-} \to τ^{\mp} \tildeκ^{\pm}_{i} (i=1,2)$ in e^+ e^- colliders, where $τ^{\mp}, \tildeκ^{\pm}_{i}(i=1,2)$ denote the physical $τ$ lepton and charginos.
An experimental search for signatures of Kaluza-Klein graviton states at the 500 GeV e+e- linear collider, in which the graviton states are produced in association with a photon, is presented. The study of the signal extraction is performed with the help of Monte Carlo simulations
We examine lepton flavor violating (LFV) interactions for heavy right-handed neutrinos that exist in most of the standard model extensions that address dark matter (DM) and neutrino mass at the loop level. In order to probe the collider effect of these LFV interactions, we impose the assumption that the model parameters give the right values of the DM relic density and fulfill the constraints from the LFV processes $\ell_α\rightarrow\ell_βγ$ and $\ell_α\rightarrow3\ell_β$. We also investigate the possibility of probing these interactions, and hence the right-handed neutrino, at leptonic collid…
We explore possible signatures for right-handed neutrinos in TeV scale B-L extension of the Standard Model (SM) at the Large Hadron Collider (LHC). The studied four lepton signal has a tiny SM background. We find the signal experimentally accessible at LHC for the considered parameter regions.
