We investigate the prospects to extract supersymmetric couplings from a decay length measurement at the LHC. Specifically, we exploit the opportunity of a light and long-lived stop which is pair-produced through gluinos in association with like-sign top quarks. Any observed finite value of the stop decay length strongly supports models in which flavor is broken in a minimal way solely by the Standard Model Yukawa couplings. We find that a 1 picosecond stop lifetime, dominated by t~ -> c chi^0 decays, yields macroscopic transverse impact parameters of about 180 microns. If the lightest neutralino is predominantly higgsino or very close in mass to the light stop, the stop lifetime even increases and allows to observe stop tracks and possibly secondary vertices directly. Measuring squark flavor violation with the stop decay length works also with a gravitino LSP if the neutralino is the NLSP. For this case, opportunities from t~ -> c chi^0 -> c gamma G~ decays for very light gravitinos with mass <= keV are pointed out.
We calculate e+e- --> stop/stop/Z at a linear collider. For large splitting between the two stops the cross-section is sensitive to the value of m(stop2) when this particle is too heavy to be directly produced. The results are compared to e+e- --> stop/stop/h.
We calculate stop stop Higgs production at the linear collider. Combining the measurements from the pair production of the lightest stop and that of the mass of the Higgs we show how, in a scenario where only the lightest stop and the lightest Higgs were accessible, one could extract the mass of the heavier stop and infer some useful information on the SUSY parameters.
In the Minimal Supersymmetric Standard Model, the cross section for the associated production of the lightest neutral Higgs boson with the lightest top squark pairs can be rather substantial at high energies. We summarize the properties of this production process at a future e^+e^- linear collider, including the $γγ$ mode.
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.
We study the detectability of the stoponium in the di-Higgs decay mode at the photon-photon collider option of the International $e^+e^-$ Linear Collider (ILC), whose center-of-mass energy is planned to reach $\sim 1$ TeV. We find that $5σ$ detection of the di-Higgs decay mode is possible with the integrated electron-beam luminosity of $1 {\rm ab}^{-1}$ if the signal cross section, $σ(γγ\rightarrow σ_{\tilde{t}_1} \rightarrow hh)$, of ${\cal O}(0.1)$ fb is realized for the stoponium mass smaller than $\sim$ 800 GeV at 1 TeV ILC. Such a value of the cross section can be realized in the minimal …
In some supersymmetric extensions of the Standard Model fairly light superpartner of t-quark is predicted, which may form bound states ({\it stoponiums}) under certain conditions. We study prospects of search for stoponium at the future Photon Linear Collider. It is found that this machine could be the best machine for discovery and study of these resonances at some scenarios of supersymmetric extension of the Standard Model. In particular, if the $hh$ decay channel is dominant stoponium could be observed at the beginning of PLC run with collision energy tuned at the stoponium mass. If this ch…
If the lighter top squark has no kinematically allowed two-body decays that conserve flavor, then it will live long enough to form hadronic bound states. The observation of the diphoton decays of stoponium could then provide a uniquely precise measurement of the top squark mass. In this paper, we calculate the cross section for the production of stoponium in a hadron collider at next-to-leading order (NLO) in QCD. We present numerical results for the cross section for production of stoponium at the LHC and study the dependence on beam energy, stoponium mass, and the renormalization and factori…
I present improved predictions for the total hadronic cross section of stop-antistop production at hadron colliders including next-to-next-to-leading-order threshold corrections and approximated Coulomb corrections. The results are based on soft corrections, which are logarithmically enhanced near threshold. I present analytic formulas for the NNLO scaling functions at threshold and explicit numbers for the total hadronic cross sections for the Tevatron and the LHC. Finally I discuss the systematic error, the scale uncertainty and the PDF error of the hadronic cross section.
We analyze a minimal flavored gauge mediation model in which the electroweak Higgs and messenger doublets are embedded in multiplets of a discrete non-Abelian symmetry. In this scenario, the minimal Higgs-messenger sector that is consistent with the 125 GeV Higgs mass has two vectorlike pairs of messenger fields. This scenario is obtained in a specific limit of the superpotential interactions of the Higgs-messenger fields and the matter fields. Due to the structure of the messenger-matter Yukawa couplings in this limit, sizable stop mixing and flavor-diagonal soft supersymmetry breaking parame…
We perform a critical reassessment of the constraints on the R-parity and baryon number violating (s)top couplings coming from flavor physics. In particular, we study K0-K0bar mixing, including QCD corrections and a class of diagrams that were neglected in previous analyses: both effects give sizeable contributions. We explain how the resulting bounds can be translated into constraints on individual couplings in the simplest class of flavor models, based on U(1) horizontal symmetries. We finally discuss the implications for the possibility of observing single superparticle production at the Te…
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.
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 have investigated the resonant production of a stop at the Large Hadron Collider, driven by baryon number violating interactions in supersymmetry. We work in the framework of minimal supergravity models with the lightest neutralino being the lightest supersymmetric particle which decays within the detector. We look at various dilepton and trilepton final states, with or without b-tags. A detailed background simulation is performed, and all possible decay modes of the lighter stop are taken into account. We find that higher stop masses are sometimes easier to probe, through the decay of the …
A proton-proton collider with center of mass energy around 100 TeV is the energy frontier machine that is likely to succeed the LHC. One of the primary physics goals will be the continued exploration of weak scale naturalness. Here we focus on the pair-production of stops that decay to a top and a neutralino. Most of the heavy stop parameter space results in highly boosted tops, populating kinematic regimes inaccessible at the LHC. New strategies for boosted top-tagging are needed and a simple, detector-independent tagger can be constructed by requiring a muon inside a jet. Assuming 20% system…
We discuss production and decays of stops, sbottoms, tau-sneutrinos, and staus in e+e- annihilation in the energy range \sqrt{s} = 0.5-1 TeV. We present numerical predictions within the Minimal Supersymmetric Standard Model for cross sections and decay rates, including one-loop radiative corrections as well as initial state radiation. We also study the importance of beam polarization for the determination of the underlying SUSY parameters. Moreover, we make a comparison of the potential to study squarks and sleptons of the 3rd generation between Tevatron, LHC, and Linear Collider.
We discuss pair production and decays of stops, sbottoms, $τ$-sneutrinos, and staus in $e^+e^-$ annihilation in the energy range $\sqrt{s} = 500 GeV$ to 2 TeV. Numerical predictions within the Minimal Supersymmetric Standard Model (MSSM) for cross sections and decay rates are presented. We study the stop discovery potential for $\sqrt{s} = 500 GeV$ and $10 \fb^{-1}$ integrated luminosity for polarized e^- beams. Moreover, we give an estimate of the error of the soft-breaking stop and sbottom parameters that can be obtained by cross section measurements with polarized e^- beams.
We discuss perturbative and non-perturbative strong interaction effects in the pair production of stop squarks ($\tilde{t}_1$) at $e^+ e^-$ colliders. Events with an additional hard gluon allow to detect or exclude stop pair production even in scenarios with very small mass splitting between $\tilde{t}_1$ and an invisible lightest supersymmetric particle (LSP). Such events can also help to establish that $\tilde{t}_1$ transforms as a triplet under $SU(3)_C$. We also carefully study non-perturbative $\tilde{t}_1$ fragmentation, which is currently not well understood: not only is the $\tilde{t}_…
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…
The discovery of a SM-like Higgs boson near 125 GeV and the flavor texture of the Standard Model motivate the investigation of supersymmetric quiver-like BSM extensions. We study the properties of such a minimal class of models which deals naturally with the SM parameters. Considering experimental bounds as well as constraints from flavor physics and Electro-Weak Precision Data, we find the following. In a self-contained minimal model - including the full dynamics of the Higgs sector - top squarks below a TeV are in tension with b->sγ constraints. Relaxing the assumption concerning the mass ge…
Right-handed neutrinos offer us the possibility of accommodating neutrino masses. In a supersymmetric model, this implies the existence of right-handed sneutrinos. Right-handed sneutrinos are expected to be as light as other supersymmetric particles if the neutrinos are Dirac fermions, or if the lepton-number breaking scale is at (or below) the supersymmetry (SUSY) breaking scale, assumed to be around the electroweak scale. Depending on the mechanism of SUSY breaking, the lightest right-handed sneutrino may be the lightest supersymmetric particle (LSP). We consider the unique hadron collider s…
Stop particles are expected to be the lightest squarks in supersymmetric theories and the search for these particles is an important experimental task. We therefore present the cross sections for the production processes $p\bar{p}/pp \to \ste\steb$ and $\stz\stzb$ at Tevatron and LHC energies in next-to-leading order supersymmetric QCD. The corrections stabilize the theoretical predictions for the cross sections, and they are positive, thus raising the cross sections to values above the leading-order predictions. Mixed $\ste\stzb/\steb\stz$ pairs can only be generated in higher orders at stron…
A future proton-proton collider with center of mass energy around 100 TeV will have a remarkable capacity to discover massive new particles and continue exploring weak scale naturalness. In this work we will study its sensitivity to two stop simplified models as further examples of its potential power: pair production of stops that decay to tops or bottoms and higgsinos; and stops that are either pair produced or produced together with a gluino and then cascade down through gluinos to the lightest superpartner (LSP). In both simplified models, super-boosted tops or bottoms with transverse mome…
We discuss pair production and decays of stops, sbottoms, and staus in $e^+e^-$ annihilation in the energy range $\sqrt{s}$ = 500 GeV to 2 TeV. We present numerical predictions within the Minimal Supersymmetric Standard Model for cross sections and decay rates. We study the stop discovery potential for $\sqrt{s}$ = 500 GeV and $10~\fb^{-1}$ integrated luminosity with full statistics background simulation.
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…
We study photoproduction of jets and heavy flavors in a polarized collider mode of HERA and in polarized $ep$ collisions at $\sqrt{S}\approx 30$ GeV. We examine the sensitivity of the cross sections and their asymmetries to the proton's polarized gluon distribution and to the completely unknown parton distributions of longitudinally polarized photons.
We analyze the production of a single top squark at hadron colliders: ppbar/pp -> \tilde{t}_1 + X. The total cross sections and the transverse momentum distributions are presented in next-to-leading order QCD. The higher-order corrections render the predictions theoretically stable with respect to variations of the factorization and renormalization scales. The transverse momentum distribution is resummed to estimate effects of the small transverse momentum regime on possible analyses. Since the corrections increase the cross sections and reduce the theoretical uncertainty, the discovery range …
Can the Large Hadron Collider explain the masses and mixings of the known fermions? A promising possibility is that these masses and mixings are determined by flavor symmetries that also govern new particles that will appear at the LHC. We consider well-motivated examples in supersymmetry with both gravity- and gauge-mediation. Contrary to spreading belief, new physics need not be minimally flavor violating. We build non-minimally flavor violating models that successfully explain all known lepton masses and mixings, but span a wide range in their predictions for slepton flavor violation. In na…
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.
If low energy supersymmetry is realized in nature it is possible that a first generation linear collider will only have access to some of the superpartners with electroweak quantum numbers. Among these, sleptons can provide sensitive probes for lepton flavor violation through potentially dramatic lepton violating signals. Theoretical proposals to understand the absence of low energy quark and lepton flavor changing neutral currents are surveyed and many are found to predict observable slepton flavor violating signals at linear colliders. The observation or absence of such sflavor violation wil…
We investigate the potentials of high energy lepton-proton colliders to detect a flavor changing $l-l^{\prime}-Z$ or $l-l^{\prime}-γ$ couplings from the processes $ep\toμ(τ)X$ and $μp\to τX$. For the $l-l^{\prime}-Z$ coupling we consider string inspired $E_6$ model whereas $l-l^{\prime}-γ$ coupling is analyzed in the framework of anomalous magnetic moment type interaction (AMMI) model.
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 illustrate the possibility of observing signals from Flavor Changing Neutral Currents, originating from the scalar sector of a Two Higgs Doublet Model. In particular, we focus on the tree level process mu^+ mu^- --> tbar c + cbar t, via scalar exchange in the s-channel, as a distinctive process for mu^+ mu^- colliders.
If the lighter top squark has no kinematically allowed two-body decays that conserve flavor, then it will form hadronic bound states. This is required in models that are motivated by the supersymmetric little hierarchy problem and obtain the correct thermal relic abundance of dark matter by top-squark-mediated neutralino annihilations, or by top-squark-neutralino co-annihilations. It is also found in models that can accommodate electroweak-scale baryogenesis within minimal supersymmetry. I study the prospects for detecting scalar stoponium from its diphoton decay mode at the Large Hadron Colli…
The degenerate stop NLSP and neutralino LSP scenario is well motivated but hard to detect at the collider experiments. We propose a novel signature for detection this scenario at the Large Hadron Collider (LHC) and demonstrate its feasibility.
We present a general phenomenological analysis of a class of Two Higgs Doublet Models with Flavor Changing Neutral Currents arising at the tree level. The existing constraints mainly affect the couplings of the first two generations of quarks, leaving the possibility for non negligible Flavor Changing couplings of the top quark open. The next generation of lepton and hadron colliders will offer the right environment to study the physics of the top quark and to unravel the presence of new physics beyond the Standar Model. In this context we discuss some interesting signals from Flavor Changing …
The prospect of observing the flavor changing decay $\fH\to t\bar c$ of a neutral Higgs boson produced via $s$-channel and its subsequent decay into $t\bar c$ is considered at a $μ^+μ^-$ collider. Numerical estimates are given in the context of a two Higgs doublet model with flavor changing couplings. It is found that for many values of the model parameters such {\it tree-level} flavor changing decays will be produced at an observable level. In addition studies of the helicity of the top will allow the determination of the relative strengths of the flavor changing Higgs couplings and these may…
We compare `fixed flavor number scheme' (FFNS) and `variable flavor number scheme' (VFNS) parton model predictions at high energy colliders. Based on our recent LO- and NLO-FFNS dynamical parton distributions, we generate radiatively two sets of VFNS parton distributions where also the heavy quark flavors h=c,b,t are considered as massless partons within the nucleon. By studying the role of these distributions in the production of heavy particles (h\bar{h}, t\bar{b}, hW^{+-}, Higgs--bosons, etc.) at high energy ep, p\bar{p} and pp colliders, we show that the VFNS predictions are compatible wit…
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 study the fermionic couplings of the neutral Higgs bosons in the THDM, assuming a four-texture structure for the Yukawa matrices. We then derive the low-energy constraints on the model, focusing in b-quark and lepton physics, and apply them to study Higgs boson detection at future colliders.
At hadron colliders, the search for R-parity violating supersymmetry can probe scalar masses beyond what is covered by pair production processes. We evaluate the next-to-leading order SUSY-QCD corrections to the associated stop or sbottom production with a lepton through R-parity violating interactions. We show that higher order corrections render the theoretical predictions more stable with respect to variations of the renormalization and factorization scales and that the total cross section is enhanced by a factor up to 70% at the Tevatron and 50% at the LHC. We investigate in detail how the…
In this work pair productions of charged and doubly charged scalars in the framework of littlest Higgs model at $e^+e^-$ colliders are studied. In the allowed parameter space of the littlest Higgs model, the production rates of the scalar pairs are calculated. It is obtained that pair productions of charged and doubly charged scalars are reachable at $e^+ e^-$ colliders with energy $\sqrt{S}\geq 1.7TeV$. Using the lepton flavor violating decays of charged scalars calculated in literature, final state analysis is done for pair production processes. This analysis show that depending on the model…
The mixing between third and second (or first) generation squarks is very small in supersymmetric models with minimal flavor violation such as gauge-, anomaly- or gaugino-mediation. An opportunity to measure this mixing will arise if the lightest stop is close enough in mass to the lightest neutralino, so that the decays into third generation quarks are kinematically forbidden. We analyze under which circumstances it might become possible to measure at the Large Hadron Collider (LHC) the rate of the flavor changing stop decays.
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…
Precision measurements of heavy-flavor hadroproduction at the Large Hadron Collider (LHC) have the ability to probe heavy-flavor parton distribution functions (PDFs) in the proton. Sensitivity of inclusive $B^\pm$ meson production cross section measurements at LHCb 13 TeV to the bottom-quark PDF is illustrated by using theory predictions obtained with a the S-ACOT-MPS general mass variable flavor number (GMVFN) scheme within the QCD factorization formula. This approach can easily be extended to other heavy-flavor production processes, such as $Z$ boson production in association with a bottom- …
We investigate charged tracks signals of a supersymmetric scenario, where the lighter stop is the next-to-lightest supersymmetric particle (NLSP). It is found that such an NLSP is stable on the scale of the detector at the LHC if one has a right-chiral sneutrino as the lightest supersymmetric particle (LSP). After identifying some benchmark points in the parameter space of a supergravity scenario with non-universal scalar masses, we study a few specific classes of signals, namely, stop pair production and gluino pair production followed by each decaying into a stop and a top. It is shown that …
The "golden region'' in the MSSM parameter space is the region where the experimental constraints are satisfied and the amount of fine-tuning is minimized. In this region, the stop trilinear soft term is large, leading to a significant mass splitting between the two stop mass eigenstates. As a result, the decay of the heavier stop into the lighter stop and a Z boson is kinematically allowed throughout the golden region. We propose that the experiments at the Large Hadron Collider (LHC) can search for this decay through an inclusive signature, Z+2jb+missing Et+X. We evaluate the Standard Model …
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…
We study lepton flavor violating signals at a future e+ e- linear collider within the general MSSM, allowing for the most general flavor structure. We demonstrate that there is a large region in parameter space with large signals, while being consistent with present experimental bounds on rare lepton decays such as mu -> e gamma. In our analysis, we include all possible signals from charged slepton and sneutrino production and their decays as well as from the decays of neutralinos and charginos. We also consider the background from the Standard Model and the MSSM. We find that in general the s…
We consider theories where the dark matter particle carries flavor quantum numbers, and has renormalizable contact interactions with the Standard Model fields. The phenomenology of this scenario depends sensitively on whether dark matter carries lepton flavor, quark flavor or its own internal flavor quantum numbers. We show that each of these possibilities is associated with a characteristic type of vertex, has different implications for direct detection experiments and gives rise to distinct collider signatures. We find that the region of parameter space where dark matter has the right abunda…
Randall-Sundrum models are models of quark flavor, because they explain the hierarchies in the quark masses and mixings in terms of order one localization parameters of extra dimensional wavefunctions. The same small numbers which generate the light quark masses suppress contributions to flavor violating tree level amplitudes. In this note we update universal constraints from electroweak precision parameters and demonstrate how future measurements of flavor violation in ultra rare decay channels of Kaons and B mesons will constrain the parameter space of this type of models. We show how collid…
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 present a study of the flavor changing decays $ϕ\to tc$ ($ϕ=H_F,\,A_F$) of the $CP$-even and $CP$-odd scalar flavons at the large hadron collider and its next stage, the high-luminosity large hadron collider. The theoretical framework is an extension of the standard model that incorporates an extra complex singlet and invokes the Froggatt-Nielsen mechanism with an Abelian flavor symmetry. The projected exclusion and discovery regions in terms of the model parameters are reported. We find that $A_F$ could be detected at the LHC by considering a reasonable scenario of the model parameter spac…
Many models, such as topcolor-assisted technicolor (TC2) models and flavor-universal TC2 models, predict the existence of extra U(1) gauge bosons $Z^{\prime}$, which couple preferentially to the third generation. The lepton flavor violating (LFV) signals of these new particles at the future $e^{+}e^{-}$ colliders (LCs) are discussed via calculating its contributions to the LFV process $e^{+}e^{-}\toμτ$. We calculate the cross section of this process and discuss its dependence on the beam polarization. The ratio of signal over square root of the background $(S/\sqrt{B})$ is also calculated. The…
In the two Higgs doublet model type III and in several other extensions of the Standard Model, there are no discrete symmetries that suppress flavor changing couplings at tree level. The experimental observation of the nu_mu -- nu_tau flavor oscillation may suggest the non-conservation of lepton number. This would lead to the decay of the type A^0/H^0 --> tau^{+/-} mu^{+/-}. We determine the present low energy limit on lepton flavor violating (LFV) couplings from the muon g-2 measurement and discuss the prospects for detecting lepton flavor violating decays at the TeVatron and at the Large Had…
Current searches for the light top squark (stop) mostly focus on the decay channels of $\tilde{t} \rightarrow t χ_1^0$ or $\tilde{t} \rightarrow b χ_1^\pm \rightarrow bW χ_1^0$, leading to $t\bar{t}/bbWW+\met$ final states for stop pair productions at the LHC. However, in supersymmetric scenarios with light neutralinos and charginos other than the neutralino lightest supersymmetric particle (LSP), more than one decay mode of the stop could be dominant. While those new decay modes could significantly weaken the current stop search limits at the LHC, they also offer alternative discovery channel…
In this article I review some connections between flavor physics and collider physics. The first part discusses the effect of right-handed charged currents on the determination of the CKM elements V_ub. It is shown that such an effective right-handed W-coupling can be generated in the MSSM which would lead to a sizable enhancement of single-top production at the LHC. The second part of this article focuses on the constraints on the mass splitting between left-handed squarks from Kaon and D mixing. Such a mass splitting has interesting consequences for squark decay chains at colliders.
Lepton flavor violating (LFV) process $e^+ e^- \to e^+ τ^-$ induced by the four-Fermi contact interactions at the International Linear Collider (ILC) is studied. Taking account of the event selection conditions, it is shown that the ILC is sensitive to smaller LFV couplings as compared to the measurement of $τ\to 3e$ process at the B-factory experiment. The upper bounds on some of the LFV couplings are improved by several factors using polarized $e^-/e^+$ beams at $\sqrt{s}=250~\mathrm{GeV}$ and by an order of magnitude at $\sqrt{s}=1~\mathrm{TeV}$.
We study flavor changing effects on the \ppbchT process at the Large Hadron Collider(LHC), which are inspired by the left-handed up-type squark mixings in the Minimal Supersymmetric Standard Model(MSSM). We find that the SUSY QCD radiative corrections to $bcH^\pm$ coupling can significantly enhance the cross sections at the tree-level by a factor about $1.5 \sim 5$ with our choice of parameters. We conclude that the squark mixing mechanism in the MSSM makes the \ppbchT process a new channel for discovering a charged Higgs boson and investigating flavor changing effects.
More often than not, models of flavor symmetry rely on the use of nonrenormalizable operators (in the guise of flavons) to accomplish the phenomenologically successful tribimaximal mixing of neutrinos. We show instead how a simple renormalizable two-parameter neutrino mass model of tribimaximal mixing can be constructed with the non-Abelian discrete symmetry T_7 and the gauging of B-L. This is also achieved without the addition of auxiliary symmetries and particles present in almost all other proposals. Most importantly, it is verifiable at the Large Hadron Collider.
