In supersymmetric theories with R-parity violation, squarks and sleptons can mediate Standard Model fermion-fermion scattering processes. These scalar exchanges in e+e- initiated reactions can give new signals at future linear colliders. We explore use of transverse beam polarization in the study of these signals in the process e+e- -> b bar{b}. We highlight certain asymmetries, which can be constructed due to the existence of the transverse beam polarization, which offer discrimination from the Standard Model background and provide increased sensitivity to the R-parity violating couplings.
Supersymmetry can explain the observed dark matter relic density with a neutralino dark matter particle and a coannihilating, almost mass-degenerate sparticle. If this were the case in nature, a linear electron positron collider like the ILC could discover the two sparticles if their masses are in the kinematic reach of the collider. This contribution discusses which observations are necessary at the ILC for predicting the dark matter relic density correctly and for confirming that the observed lightest neutralino is the only kind of dark matter. We take the case of stau coannihilation as an e…
Taking into account the constraints on the free parameters of the littlest Higgs model with T-parity (called $LHT$ model) from some rare decay processes, such as $μ\rightarrow eγ$ and $μ\rightarrow 3e$, we consider the contributions of the $LHT$ model to the lepton flavor violating ($LFV$) processes $e^{+}e^{-}\rightarrow l_{i}\bar{l}_{j}$ and $γγ\rightarrow l_{i}\bar{l}_{j}$ ($i\neq j$). We find that the $LHT$ model can indeed produce significant contributions to these $LFV$ processes and its $LFV$ signal might has a chance of being observed in the future $ILC$ experiments.
In topcolor-assisted technicolor models (TC2) the hitherto unconstrained lepton flavor mixing induced by the new gauge boson $Z'$ will lead to the lepton flavor violating productions of $τ\bar μ$, $τ\bar e$ and $μ\bar e$ in photon-photon collision at the proposed International Linear Collider (ILC). Through a comparative analysis of these processes, we find that the better channels to probe the TC2 is the production of $τ\bar μ$ or $τ\bar e$ which occurs at a much higher rate than $μ\bar e$ production due to the large mixing angle and the large flavor changing coupling, and may reach the detec…
We study the possible reach of the proposed International Linear Collider (ILC) in exploring the lepton flavor violating (LFV) Higgs boson decay $h\toμτ$. Two generic types of models are investigated, both involving an extended scalar sector. For the first type, the rest of the scalars are heavy and beyond the reach of ILC but the LFV decay occurs through a tiny admixture of the Standard Model (SM) doublet with the heavy degrees of freedom. In the second class, which is more constrained from the existing data, the SM Higgs boson does not have any LFV decay but there are other scalars degenerat…
We study CP violation in the two-body decay of a scalar tau into a neutralino and a tau, which should be probed at the LHC and ILC. From the normal tau polarization, a CP asymmetry is defined which is sensitive to the CP phases of the trilinear scalar coupling parameter $A_τ$, the gaugino mass parameter $M_1$, and the higgsino mass parameter $μ$ in the stau-neutralino sector of the Minimal Supersymmetric Standard Model. Asymmetries of more than 70% are obtained in scenarios with strong stau mixing. As a result, detectable CP asymmetries in stau decays at the LHC are found, motivating further d…
The hitherto unconstrained lepton flavor mixing, induced by the new charged scalar ϕ^\pm and ϕ^{\pm\pm} predicted by many new physics models such as higgs triplet models, may lead to the lepton flavor violating productions of τ\bar μ, τ\bar e and μ\bar e in photon-photon collision at the proposed international linear collider. In this paper, we consider the contributions of the ϕ^\pm and ϕ^{\pm\pm} in the context of the higgs triplet models to the processes γγ\to l_i\bar l_j (i, j= e, μ, τ, i\neq j) and find that they can be good channels to probe these new physics models. The lepton flavor vi…
In this work, Higgs couplings with gauge bosons is probed through $e^-e^+ \rightarrow W^-W^+H$ in an effective Lagrangian framework. An ILC of 500 $GeV$ center of mass energy with possible beam polarization is considered for this purpose. The reach of ILC with integrated luminosity of 300 $fb^{-1}$ in the determination of both the CP-conserving and CP-violating parameters are obtained. Sensitivity of the probe of each of these couplings on the presence of other couplings is investigated. The most influential couplings parameters are $\bar c_W=-\bar c_B$. Other parameters of significant effect …
Flavour-violating Higgs interactions are suppressed in the Standard Model such that their observation would be a clear sign of new physics. We investigate the prospects for detecting quark flavour-violating Higgs decays in the clean ILC environment. Concentrating on the decay to a bottom and a light quark $j$, we identify the dominant Standard Model background channels as coming from hadronic Standard Model Higgs decays with mis-identified jets. Therefore, good flavour tagging capabilities are essential to keep the background rate under control. Through a simple cut-based analysis, we find tha…
Run-I results from the CMS collaboration show an excess of events in the decay $h \to μτ_e$ with a local significances of 2.4$σ$. This could be the first hint of flavour violation in the Higgs sector. We summarise the bounds on the flavour violating Yukawa couplings from direct searches, low energy measurements and projected future experiments. We discuss the sensitivity of upcoming HL-LHC runs and future lepton colliders in measuring lepton-flavour violating couplings using an effective field theory framework. For the HL-LHC we find limits on BR($h\to μτ$) and BR$(h\to e τ) \lesssim \mathcal{…
We present the two-loop $β$-functions for non-standard soft supersymmetry-breaking couplings including non-standard R-parity violating soft terms in the Minimal Supersymmetric Standard Model
A collider signal with a stable gravitino of ${\cal O}(10)$eV mass at the International Linear Collider (ILC) experiment is investigated. Such a light gravitino is generally predicted in the low-scale gauge mediation scenario of the supersymmetry breaking. We particularly focus on the case that the next lightest supersymmetric particle is stau, which eventually decays into a gravitino and a $τ$-lepton. With such a small gravitino mass, the lifetime of the stau is $10^{-15}$--$10^{-11}$sec, and the produced stau decays before reaching the first layer of the inner detector of the ILC. It is show…
Taking into account the constraints on the lepton flavor violation (LFV) couplings of the Standard Model (SM) Higgs boson H with leptons from low energy experiments and the recent Compact Muon Solenoid experiment results, we investigate production of the SM Higgs boson associated with a lepton τvia e γcollision at the International Linear Collider (ILC) and Large Hadron Electron Collider experiments. The production cross sections are calculated and the LFV signals and the relevant SM backgrounds are examined. The LFV signals of the SM Higgs boson might be observed via e γcollision in future IL…
We summarized our report on leptonic flavor violating Higgs decay into mu + tau under the scheme of a generic supersymmetric standard model without R parity. With known experimental constraints imposed, important combinations of R-parity violating parameters which can give notable branching ratios are listed.
We re-evaluate prospects for supersymmetry at the proposed International Linear e^+e^- Collider (ILC) in light of the first two years of serious data taking at LHC: LHC7 with ~5 fb^{-1} of pp collisions at sqrt{s}=7 TeV and LHC8 with ~20 fb^{-1} at \sqrt{s}=8 TeV. Strong new limits from LHC8 SUSY searches, along with the discovery of a Higgs boson with m_h~125 GeV, suggest a paradigm shift from previously popular models to ones with new and compelling signatures. After a review of the current status of supersymmetry, we present a variety of new ILC benchmark models, including: natural SUSY, ra…
Particle physics models with Natural Supersymmetry are characterized by a superpotential parameter μ\sim m_h \sim125$ GeV, while third generation squarks have mass <0.5-1.5 TeV. Gluinos should be lighter than several TeV so as not to destabilize the lighter squarks. First and second generation sfermions can be at the tens-of-TeV level which yields a decoupling solution to the SUSY flavor and CP problems. Adopting a top-down approach, we delineate the range of GUT scale SUSY model parameters which leads to a Natural SUSY mass spectrum. We find natural SUSY models to be tightly constrained by th…
The measurement of Higgs self-coupling is one of the most crucial physics goals at the future colliders. At the LHC, the di-Higgs production is a main way to measure the Higgs trilinear coupling. As a complementary to the di-Higgs production, $t \bar{t} hh$ process may open a new avenue to measure di-Higgs physics at the LHC and a future 100 TeV $pp$ collider or a high energy $e^+e^-$ collider since the extra $t\bar t$ in the final states may efficiently suppress the backgrounds. However, such a kind of process is also controlled by the top-Higgs coupling. In this work, we investigate the impa…
The latest results from CMS on R-Parity violating Supersymmetry based on the 19.5/fb full dataset from the 8 TeV LHC run of 2012 are reviewed. The results are interpreted in the context of simplified models with multilepton and b-quark jets signatures that have low missing transverse energy arising from light top-squark pair with R-parity-violating decays of the lightest supersymmetric particle. In addition to simplified model, a new approach for phenomenological MSSM interpretation is shown which demonstrates that the obtained results from multilepton final states are valid for a wide range o…
K -> pi nu nubar and R-parity violating supersymmetry
基于最近E787、E949和E865合作的实验数据以及标准模型（SM）预测与数据之间的差异，我们详细考虑了R宇称破坏（RPV）对K -> pi nu nubar超对称性的贡献.这种衰减的理论上的干净性构成了一种有用的方式来提供约束，与长距离效应无关。包括单圈R-奇偶守恒（RPC）超对称性和树级RPV超对称贡献之间的干扰的可能性，我们的结果允许改善R-奇偶违反耦合相对于以前的分析的限制。
We update the single-coupling bounds on R-parity violating supersymmetry using the most up to date data as of October 2009. In addition to the data listed in the 2009 Review of Particle Properties, we utilize a new determination of the weak charge of cesium-133, and preliminary tau-decay branching fractions from Babar. Analysis of semileptonic D-decay is improved by the inclusion of experimentally measured form-factors into the calculation of the Standard Model predictions.
Phenomenological analysis to the R-parity violating supersymmetry with a vector-like extra generation is performed in detail. It is found that, via the trilinear couplings, the correct neutrino spectrum can be obtained. The Higgs mass rises to 125 GeV by new up-type Yukawa couplings of vector-like quarks with no need of very heavy superpartners. Phenomena of new heavy fermions at LHC are predicted.
We study the CP-violating terms of the spin-spin correlations in neutralino production and their subsequent two-body decays into sleptons plus leptons at the ILC. We analyze CP-sensitive observables with the help of T-odd products of the spin-spin terms. These terms depend on the polarizations of both neutralinos, with one polarization perpendicular to the production plane. We present a detailed numerical study of the CP-sensitive observables, cross sections, and neutralino branching ratios in the Minimal Supersymmetric Standard Model with complex parameters.
We update the bounds on $R$-parity violating supersymmetry originating from meson oscillations in the $B^0_{d/s}$ and $K^0$ systems. To this end, we explicitly calculate all corresponding contributions from $R$-parity violating operators at the one-loop level, thereby completing and correcting existing calculations. We apply our results to the derivation of bounds on $R$-parity violating couplings, based on up-to-date experimental measurements. In addition, we consider the possibility of cancellations among flavor-changing contributions of various origins, e.g. from multiple $R$-parity violati…
