Tom Banks, Linda M. Carpenter, Jean-François Fortin
We discuss SUSY models in which renormalizable lepton number violating couplings hide the decay of the Higgs through h -> χ_1^0 + χ_1^0 followed by χ_1^0 -> τ+ 2 jets or χ_1^0 -> ν_τ+ 2 jets and also explain neutrino masses. This mechanism can be made compatible with gauge mediated SUSY breaking.
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We consider the proton decay involving a light gravitino or axino in gauge-mediated supersymmetry breaking models to derive constraints on the $R$ parity and baryon number violating Yukawa couplings. Bounds on all nine coupling constants are obtained by considering the decay amplitudes at one-loop order.
We study the impact of the inverse seesaw mechanism on several low-energy flavour violating observables such as tau decaying to three muons in the context of the Minimal Supersymmetric Standard Model. As a consequence of the inverse seesaw, the contributions of the right-handed sneutrinos significantly enhance the Higgs-mediated penguin diagrams. We find that different flavour violating branching ratios can be enhanced by as much as two orders of magnitude. We also comment on the impact of the Higgs-mediated processes on the leptonic B-meson decays and on the Higgs flavour violating decays.
We study the impact of the inverse seesaw mechanism on several leptonic and hadronic low-energy flavour-violating observables in the context of the Minimal Supersymmetric Standard Model. Indeed, the contributions of the light right-handed sneutrinos from the inverse seesaw significantly enhance the Higgs-mediated penguin diagrams. We find that this can increase the different branching ratios by as much as two orders of magnitude.
The size of the branching ratios for the $τ\to μγ$ and $τ\to μγγ$ decays induced by a lepton flavor violating Higgs interaction $Hτμ$ is studied in the frame of effective field theories. The best constraint on the $Hτμ$ vertex, derived from the know measurement on the muon anomalous magnetic moment, is used to impose the upper bounds $Br(τ\to μγ)<2.5\times 10^{-10}$ and $Br(τ\to μγγ)<2.3\times 10^{-12}$, which are more stringent than current experimental limits on this class of transitions.
Lepton Flavor-Violating Higgs Decays Mediated by Ultralight Gauge Boson
本研究分析超轻规范玻色子介导的希格斯轻子味破缺衰变，通过匹配树图阶味破缺相互作用模型与有效场论，结合CMS和ATLAS实验数据间接给出非标准衰变的上限，并研究了多种相关可观测量。
We propose a new scenario that solves the slepton negative mass squared problem of the minimal supersymmetric standard model with anomaly mediated supersymmetry breaking. The solution is achieved by including three trilinear R-parity violating operators in the superpotential. The soft supersymmetry breaking terms satisfy renormalisation group invariant relations in terms of supersymmetric couplings and the overall supersymmetry breaking mass scale. Flavour changing neutral currents can be naturally highly suppressed. A specific model predicts tan beta=4.2+/-1.0. Excluding sleptons, the supersy…
Most studies of Higgs sector CP violation focus on the detection of CP-violating neutral Higgs-fermion Yukawa couplings, which yield P-odd, CP-violating phenomena. There is some literature on purely bosonic signatures of Higgs sector CP violation, where the simultaneous observation of three processes (suitably chosen) constitutes a signal of P-even CP violation. However, in the examples previously analyzed, some of the processes are strongly suppressed in the approximate Higgs alignment limit (corresponding to the existence of a Standard Model like Higgs boson as suggested by LHC data), in whi…
We study the three body lepton flavor violating (LFV) decays $μ^- \to e^- e^+ e^-$, $τ^- \to l_i^- l_j^+ l_j^-$ and the semileptonic decay $τ\to μϕ$ in the flavor changing neutral current (FCNC) mediated $Z$ boson model. We also calculate the branching ratios for LFV leptonic B decays, $B_{d,s} \to μe$, $B_{d,s} \to τe$, $B_{d,s} \to τμ$ and the conversion of muon to electron in Ti nucleus. The new physics parameter space is constrained by using the experimental limits on $μ^- \to e^- e^+ e^-$ and $τ^- \to μ^- μ^+ μ^-$. We find that the branching ratios for $τ\to eee $ and $τ\to μϕ$ processes …
We study the Lepton number violating like-sign dilepton processes $h_1 h_2 \to l^\pm l^{\prime \pm} jj X$ and $h_1 h_2 \to l^\pm l^{\prime \pm} W^\pm X$, mediated by heavy GeV scale Majorana neutrinos. We focus on the resonantly enhanced contributions with a nearly on-mass-shell Majorana neutrino in the s-channel. We study the constraints on like-sign dilepton production at the Tevatron and the LHC on the basis of the existing experimental limits on the masses of heavy neutrinos and their mixings $U_{αN}$ with $α= ν_{e}, ν_μ, ν_τ$. Special attention is paid to the constraints from neutrinoless…
We derive the general resummed effective Lagrangian for Higgs-mediated flavour-changing neutral-current (FCNC) interactions in the Minimal Supersymmetric Standard Model (MSSM), without resorting to particular assumptions that rely on the squark-mass or the quark-Yukawa structure of the theory. In our derivation we also include the possibility of explicit CP violation through the Cabibbo--Kobayashi--Maskawa mixing matrix and soft supersymmetry-breaking mass terms. The advantages of our resummed FCNC effective Lagrangian are explicitly demonstrated within the context of phenomenologically motiva…
The projected reach of direct electroweakino searches at the HL-LHC ($\sqrt{s}=14~{\rm TeV}, ~3000~{\rm fb^{-1}}$ LHC) in the framework of simplified models with R-parity violating (RPV) operators: $λ_{112}^{\prime \prime}u^{c}d^{c}s^{c}$ and $λ_{113}^{\prime\prime}u^{c}d^{c}b^{c}$, is studied. Four different analysis channels are chosen: $Wh$ mediated $1l+2b+jets+\rm E{\!\!\!/}_T$, $Wh$ mediated $1l+2γ+jets+\rm E{\!\!\!/}_T$, $WZ$ mediated $3l+jets+\rm E{\!\!\!/}_T$ and $WZ$ mediated $3l+2b+jets+\rm E{\!\!\!/}_T$ and the projected exclusion/discovery reach of direct wino searches in these cha…
We construct realistic supergravity models where supersymmetry breaking arises from the $D$-terms of an anomalous $U(1)$ gauge symmetry broken at the Planck scale. The model has the attractive feature that the gaugino masses, the $A$ and $B$ terms and the mass splittings between the like-charged squarks of the first two generations compared to their average masses are all suppressed. As a result, the electric dipole moment of the neutron as well as the flavor changing neutral current effects are predicted to be naturally small. These models predict naturally the expected value of the $μ$-term …
We consider the lepton-number-violating processes in $Λ_b$/$Λ_c$ decays mediated by on-shell GeV-scale sterile neutrino. We calculate the branching ratio for the following processes: $Λ_b^{0} \rightarrow \mathcal{B}^+ μ^{-}μ^- π^+$, where $\mathcal{B}^+$ is $Λ_c^+$ or proton, and $Λ_c^{+} \rightarrow Λμ^{+}μ^+ π^-$, as function of the mass of the sterile neutrino $m_N$ and the heavy-light mixing coefficient of the extended Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix $|U_{μN}|^2$. The effect of finite detector size is included in our calculation. After comparing the theoretical effective bran…
Higgs mediated flavor violating electromagnetic interactions, induced at the one--loop level by a nondiagonal $Hf_if_j$ vertex, with $f_i$ and $f_j$ charged leptons or quarks, are studied within the context of a completely general effective Yukawa sector that comprises $SU_L(2)\times U_Y(1)$--invariant operators of up to dimension--six. Exact formulae for the one--loop $γf_if_j$ and $γγf_if_j$ couplings are presented and their related processes used to study the phenomena of Higgs mediated lepton flavor violation. The experimental limit on the $μ\to eγ$ decay is used to derive a bound on the b…
The possibility of detecting double flavor violating top quark transitions at future colliders is explored in a model-independent manner using the effective Lagrangian approach through the $t \to u_iτμ$ ($u_i=u,c$) decays. A Yukawa sector that contemplates $SU_L(2)\times U_Y(1)$ invariants of up to dimension six is proposed and used to derive the most general flavor violating and CP violating $q_iq_jH$ and $l_il_jH$ vertices of renormalizable type. Low-energy data, on high precision measurements, and experimental limits are used to constraint the $tu_iH$ and $Hτμ$ vertices and then used to pre…
Gauge-mediated supersymmetry breaking is known to greatly suppress flavor changing neutral current effects. However, we show that gauge mediation in the context of leptogenesis implies potentially large lepton flavor violating signals. If the heavy right-handed neutrinos that participate in leptogenesis are lighter than the messenger scale of gauge mediation, they will induce flavor off-diagonal masses to the sleptons which in turn can induce large effects in mu to e gamma, tau to mu gamma, and mu-e conversion in nuclei. We demonstrate this result and compute numerically the lepton-flavor viol…
The lepton number violating process, $e^- e^- \to W^- W^-$ has been widely discussed in the Majorana neutrino exchange mechanism. Here, we discuss this process in a composite neutrino model where excited Majorana neutrinos are exchanged. We found several qualitatively different features from the neutrino exchange case: (1) The longitudinally polarized $W$'s are not produced, (2) the neutrinoless double beta decay does not constrain much and a much larger cross section is expected, and (3) CP violating phases may be explored because all excited neutrinos are heavy so that large mixings among th…
In this paper we study lepton flavor violating semileptonic decays of heavy baryons in a framework of a model with large extra dimensions and a single generation . Resulting branching ratios for these decays mediated by Kaluza-Klein modes of photon and Z-boson are presented in a model-independent form.
We consider supersymmetric extensions of the standard model with general non-universal soft breaking terms. We analyse in a model-independent way the constraints on these terms at the electroweak energy scale coming from gluino mediated flavour (F) changing neutral current and CP-violating processes. We have computed the complete $ΔF=1$ and $ΔF=2$ effective hamiltonian for gluino mediated processes, including for the first time the effect of box diagrams in the evaluation of $ε^{\prime}/ε$. We present numerical results for the constraints on these non-universal soft breaking terms for differen…
Light CP-violating Higgs bosons with mass lower than 70 GeV might have escaped detection in direct searches at the LEP collider. They may remain undetected in conventional search channels at the Tevatron and LHC. In this Letter we show that exclusive diffractive reactions may be able to probe for the existence of these otherwise elusive Higgs particles. As a prototype example, we calculate diffractive production cross-sections of the lightest Higgs boson within the framework of the Minimal Supersymmetric Standard Model with explicit CP violation. Our analysis shows that the challenging regions…
The SUSY CP problem in the framework of gauge mediated SUSY breaking model is considered. We first discuss the electric dipole moments of the electron and neutron, which are likely to be larger than the experimental upper bound if all the phases in the Lagrangian are O(1). We derive a constraint on the phases in the so-called $μ$- and $B_μ$-parameters and gaugino masses. Then, we discuss a model in which the CP violating phase can be adequately suppressed. If the $μ$- and $B_μ$-parameters originate from the same superpotential interaction as the SUSY breaking field, the CP violating phase vani…
In Lorentz- and CPT-violating effective field theories involving scalar and spinor fields, there exist forms of Lorentz violation that modify only the scalar-spinor Yukawa interaction vertices. These affect low-energy fermion and antifermion scattering processes through modifications to the nonrelativistic Yukawa potentials. The modified potentials involve novel combinations of momentum, spin, and Lorentz-violating background tensors.
It is known that limits on baryon-violating nucleon decays do not, in general, imply corresponding suppression of $n - \bar n$ transitions. In the context of a model with fermions propagating in higher dimensions, we investigate a related question, namely the implications of limits on $ΔL=-1$ proton and bound neutron decays mediated by four-fermion operators for rates of nucleon decays mediated by $k$-fermion operators with $k =6$ and $k=8$. These include a variety of nucleon and dinucleon decays to dilepton and trilepton final states with $ΔL=-3, \ -2, \ 1$, and $2$. We carry out a low-energy…
$\mathcal{P}$, $\mathcal{T}$-violating axion-mediated interactions in RaOH molecule
研究RaOH分子对轴子介导的$\mathcal{P}$, $\mathcal{T}$违反相互作用的敏感性，分析振动对轴子介导电子-核相互作用的影响。
In light of a discrepancy of the direct $CP$ violation in $K\toππ$ decays, $\varepsilon'/\varepsilon_K$, we investigate gluino contributions to the electroweak penguin, where flavor violations are induced by squark trilinear couplings. Top-Yukawa contributions to $ΔS = 2$ observables are taken into account, and vacuum stability conditions are evaluated in detail. It is found that this scenario can explain the discrepancy of $\varepsilon'/\varepsilon_K$ for the squark mass smaller than 5.6 TeV. We also show that the gluino contributions can amplify $\mathcal{B}(K \to πν\overlineν)$, $\mathcal{B…
In the presence of P,T-violating interactions, the exchange of axion-like particles between electrons and nucleons in atoms and molecules induces electric dipole moments (EDMs) of atoms and molecules. We perform calculations of such axion-exchange-induced atomic EDMs using the relativistic Hartree-Fock-Dirac method including electron core polarisation (RPA) corrections. We present analytical estimates to explain the dependence of these induced atomic EDMs on the axion mass and atomic parameters. From the experimental bounds on the EDMs of atoms and molecules, including $^{133}$Cs, $^{205}$Tl, …
The exchange of an axion-like particle between atomic electrons and the nucleus may induce electric dipole moments (EDMs) of atoms and molecules. This interaction is described by a parity- and time-reversal-invariance-violating potential which depends on the product of a scalar $g^s$ and a pseudoscalar $g^p$ coupling constant. We consider the interaction with the specific combination of these constants, $g_e^s g_N^p$, which gives significant contributions to the EDMs of diamagnetic atoms. In this paper, we calculate these contributions to the EDMs of $^{199}$Hg, $^{129}$Xe, $^{211}$Rn and $^{2…
We perform a comprehensive study of the dominant two- and higher-loop contributions to the $^{205}$Tl, neutron and muon electric dipole moments induced by Higgs bosons, third-generation quarks and squarks, charginos and gluinos in the Minimal Supersymmetric Standard Model (MSSM). We find that strong correlations exist among the contributing CP-violating operators, for large stop, gluino and chargino phases, and for a wide range of values of $\tanβ$ and charged Higgs-boson masses, giving rise to large suppressions of the $^{205}$Tl and neutron electric dipole moments below their present experim…
Updated constraints on $\mathcal{T}$,$\mathcal{P}$-violating axionlike-particle-mediated electron-electron and electron-nucleus interactions from HfF$^+$ experiment
本文利用从头算相对论耦合簇理论计算HfF$^+$分子参数，从JILA实验数据中为宽质量范围的类轴子粒子介导的电子-电子与电子-核相互作用推导出更新一个数量级的约束。
We compute the CP-violating (CPV) scalar axion coupling to nucleons in the framework of baryon chiral perturbation theory and we apply the results to the case of left-right symmetry. The correlated constraints with other CPV observables show that the predicted axion nucleon coupling is within the reach of present axion-mediated force experiments for $M_{W_R}$ up to $1000$ TeV.
We discuss $Z$ mediated flavour changing neutral currents within a model where the hierarchical quark and lepton masses are explained via a fourth vector-like family, together with a scalar sector consisting of two Higgs doublets augmented by a gauge singlet scalar field that spontaneously breaks an extra global $U(1)^{\prime}$ symmetry. The $Z$ mediated flavor violating interactions arise from the mixings between the SM fermions and the vector-like fermions, where the mixing is discussed in an analytic approximation and also exactly numerically. We first discuss charged lepton flavor violatin…
In minimal anomaly-mediated supersymmetry breaking models, tachyonic sleptons are avoided by introducing a common scalar mass similar to the one introduced in minimal supergravity. This may lead to non-minimal flavour-violating interactions, e.g., in the squark sector. In this paper, we analyze the viable anomaly-mediated supersymmetry breaking parameter space in the light of the latest limits on low-energy observables and LHC searches, complete our analytical calculations of flavour-violating supersymmetric particle production at hadron colliders with those related to gluino production, and s…
The R-parity non-conservation phenomenology within the minimal supersymmetric standard model with gauge mediated supersymmetry breaking has been studied. New constraints on the lepton number violating constant $λ_{111}^\prime$ were imposed by non-observability of the neutrinoless double beta decay. We find that $λ_{111}^\prime$ depends strongly on the effective supersymmetry breaking scale $Λ$ only and deduce limits which are much stronger than those previously found in literature.
Using the freedom in SO(10) GUT's one can generalize the existing models without changing the mass spectrum of fermions to obtain a significant suppression of proton decay resulting from the baryon number violating operators of dimension 5. In some limiting cases, their contributions can be made negligible compared to the dimension 6 operators resulting from the heavy gauge bosons exchange.
Revisiting the Electroweakino Sector of the Baryon Number Violating MSSM at the HL-LHC with Deep Neural Networks
本文利用深度神经网络研究HL-LHC对破坏重子数的MSSM轻子弱相互作用子区的探测灵敏度，通过不同中介机制下的信号通道分析，探讨winos的探测极限。
In the standard model (SM), lepton flavor violating (LFV) Higgs decay is absent at renormalizable level and thus it is a good probe to new physics. In this article we study a type of new physics that could lead to large LFV Higgs decay, i.e., a lepton-flavored dark matter (DM) model which is specified by a Majorana DM and scalar lepton mediators. Different from other similar models with similar setup, we introduce both left-handed and right-handed scalar leptons. They allow large LFV Higgs decay and thus may explain the tentative Br$(h\raτμ)\sim1\%$ experimental results from the LHC. In partic…
It has been shown that unless the tri-linear R-parity violating coupling $λ_{i33}$ (i = 1, 2) is small enough ($λ_{i33}<$ ${10}^{-2}$ for MSSM and ${10}^{-3}$ for GMSB model),the partial decay width of photino decaying into 'photon + $ν_{e,μ}$', both in supergravity motivated (MSSM) and gauge mediated (GMSB) supersymmetric models are larger than the partial decay width of photino decaying into 'photon + goldstino' in R-parity conserving GMSB model including one loop supersymmetric QED correction.
We present a detailed study of the Thallium, neutron, Mercury and deuteron electric dipole moments (EDMs) in the CP-violating Minimal Supersymmetric extension of the Standard Model (MSSM). We take into account the complete set of one-loop graphs, the dominant Higgs-mediated two-loop diagrams, the complete CP-odd dimension-six Weinberg operator and the Higgs-mediated four-fermion operators. We improve upon earlier calculations by including the resummation effects due to CP-violating Higgs-boson mixing and to threshold corrections to the Yukawa couplings of all up- and down-type quarks and charg…
The explanation of a 200 GeV R-parity violating squark to the HERA high-$Q^2$ anomaly would have an important impact on supersymmetry-breaking models. Here we show that a squark of mass around 200 GeV is disallowed in the minimal gauge-mediated SUSY-breaking models in the parameter space constrained by the radiative electroweak-symmetry breaking and the experimental lower limits on supersymmetric particles, even after including the large R-parity violating couplings. Supergravity motivated models can, on the other hand, give rise to these scalar quarks in a wide range of parameter space.
After the present establishment of CP-Violation in $B_{d}$-physics, consistency tests of unitarity in the Standard Model and the search of new phenomena are compulsory. I illustrate the way to look for T-violation, without contamination of absorptive parts, in correlated decays in B-factories. $B_{s}$-mixing and penguin-mediated $B_{s}$-decays are of prime importance in hadronic machines to look for new physics.
We propose a novel supersymmetric unified scenario of the triplet seesaw mechanism where the exchange of the heavy triplets generates both neutrino masses and soft supersymmetry breaking terms. Our framework is very predictive since it relates neutrino mass parameters, lepton flavour violation in the slepton sector, sparticle and Higgs spectra and electroweak symmetry breakdown. The phenomenological viability and experimental signatures in lepton flavor violating processes are discussed.
From analysis of data produced by the BABAR experiment, the first upper bounds (90% C.L.) were obtained on the branching ratios $Br(τ\to e γγ)<2.5 \times 10^{-4}$ and $Br(τ\to μγγ)<5.8 \times 10^{-4}$. In addition, improved upper bounds (95% C.L.) were found on branching ratios $Br(τ\to e X)<1.4 \times 10^{-3}$ and $Br(τ\to μX) <2.0 \times 10^{-3}$, where $X$ is an undetected weakly interacting boson with mass $m_X<1.6$ GeV/$c^2$.
In the following work we consider the possibility of explaining the observed baryon number asymmetry in the universe from simple baryon number violating modifications, involving massive scalar bosons, to the Standard Model. In these cases baryon number violation is mediated through a combination of Yukawa and scalar self-coupling interactions. Starting with a previously compiled catalogue of baryon-number violating extensions of the Standard Model, we identify the minimal subsets which can induce a $B-L$ asymmetry and thus be immune to sphaleron washout. For each of these models, we identify t…
Observing charge-parity (CP) or time-reversal (T) violations in the leptonic sector will give useful information to elucidate the nature of neutrinos. CP-violating couplings in charged leptonic currents carry out the weak phases necessary to break these symmetries. Here we study the interference of $W^{\pm}$ and $H^{\pm}$ bosons mediated amplitudes as the origin of possible CP and T violation in semileptonic decays of $K^{\pm}$ mesons and $τ^{\pm}$ leptons. We use the experimental bound on the T-odd transverse polarization asymmetry in $K^+_{μ3}$ decays to predict an upper limit on the CP viol…
The decay rate of neutrinoless double beta decay could be dominated by short-range diagrams involving heavy scalar particles ("topology-II" diagrams). Examples are diagrams with diquarks, leptoquarks or charged scalars. Here, we compare the discovery potential for lepton number violating signals at the LHC with constraints from dijet and leptoquark searches and the sensitivity of double beta decay experiments, using three example models. We note that already with 20/fb the LHC will test interesting parts of the parameter space of these models, not excluded by current limits on double beta deca…
We study the \textit{CP} violation in the lepton-number-violating process $B_s^0 \rightarrow D_s^- μ^+ μ^+ π^-$ and its \textit{CP}-conjugate process $\bar{B_s^0} \rightarrow D_s^+ μ^- μ^- π^+$ that are induced by two GeV-scale Majorana neutrinos with nearly-degenerate masses. Our result shows that the size of the \textit{CP} violation could become considerable if the mass difference between the two Majorana neutrinos is around the decay width of the neutrinos. We perform experimental analysis on the \textit{CP}-violating processes at LHCb within its upgrade II. The analysis shows that under c…
We study the effect of the FCNC mediated $Z$ boson in the rare semileptonic baryonic decays $Λ_b \to Λl^+ l^-$. We consider the model where the standard model fermion sector is extended by an extra vector like down quark, as a consequence of which it allows CP violating Z mediated flavor changing neutral current at the tree level. We find that due to this non-universal $Zbs $ coupling, branching ratios of the rare semileptonic $Λ_b$ decays are enhanced reasonably from their corresponding standard model values and the zero point of the forward backward asymmetry for $Λ_b \to Λμ^+ μ^-$ is shifte…
We investigate two-loop gluino corrections to the effective Lagrangian for $b\to s+γ(g)$ in the minimal supersymmetric extension of the standard model (MSSM) at large $\tanβ$, including the contributions in which quark flavor change is mediated by charginos. Using the translation invariant of loop momenta and the Ward-Takahashi identities (WTIs) that are required by the $SU(3)_c\times U(1)_{_{em}}$ gauge invariance, we simplify our expressions to concise forms. As an example, we discuss two-loop gluino corrections to the CP asymmetry of inclusive $B\to X_{_s}γ$ decay in CP violating MSSM.
In the next generation of long-baseline neutrino oscillation experiments, aiming to determine the charge-parity violating phase $δ_{CP}$ in the appearance channel, fine-grained time-projection chambers are expected to play an important role. In this Letter, we analyze an influence of realistic detector capabilities on the $δ_{CP}$ sensitivity for a setup similar to that of the Deep Underground Neutrino Experiment. We find that the effect of the missing energy, carried out by undetected particles, is sizable. Although the reconstructed neutrino energy can be corrected for the missing energy, th…
We study the effect of the Higgs-exchange diagram for the lepton flavor violating muon-electron conversion process in nuclei in the supersymmetric seesaw model. The contribution is significant for a large value of tan beta and a small value of a neutral heavy Higgs boson mass, in which case the ratio of the branching ratios of B(mu N -> e N) / B(mu -> e gamma) is enhanced. We also show that the target atom dependence of the conversion branching ratio provides information on the size of the Higgs exchange diagram.
We show that a supersymmetric standard model exhibiting anomaly mediated supersymmetry breaking can generate naturally the observed neutrino mass spectrum as well mixings when we include bilinear R-parity violation interactions. In this model, one of the neutrinos gets its mass due to the tree level mixing with the neutralinos induced by the R-parity violating interactions while the other two neutrinos acquire their masses due to radiative corrections. One interesting feature of this scenario is that the lightest supersymmetric particle is unstable and its decay can be observed at high energy …
We consider lepton flavour violating decays of the top quark, mediated by four-fermion operators. We compile constraints on a complete set of SU(3)*U(1)-invariant operators, arising from their loop contributions to rare decays and from HERA's single top search. The bounds on e-mu flavour change are more restrictive than l-tau; nonetheless the top could decay to a jet $+ e \barμ$ with a branching ratio of order $10^{-3}$. We estimate that the currently available LHC data (20 inverse-fb at 8 TeV) could be sensitive to $BR(t \to e \barμ$+ jet) $ \sim 6\times 10^{-5}$, and extrapolate that 100 inv…
The possible phenomenological consequences of R-parity violating interactions in the framework of low energy supersymmetry breaking are studied. It is pointed out that even very weak R-parity violation would completely overshadow one of the basic signatures of low energy supersymmetry breaking models, that is, the decay of the next to lightest supersymmetric particle into a photon (lepton) and missing energy. Thus, the observation of these decays would put very strong limits on R-parity violating couplings. Vice-versa, if R-parity violation is established experimentally, before a detailed know…
In the light of the recent measurement of the muon anmalous magnetic moment $a_μ$ by the Muon $(g-2)$ Collaboration, we examine the contribution to $a_μ$ from the exchange of flavor changing scalars. Assuming that the heavier generations have larger flavor changing couplings, we obtain a bound on $μ- τ$ Yukawa coupling for a given scalar mass. Constraints on other flavor changing/conserving couplings are also obtained from the lepton flavor violating decays of muon and tau lepton, and bounds on the branching ratio of $τ\to 3 e$, $μ\to 3 e$ and $τ\to e μe$ processes are predicted.
We discuss the $μ$-$e$ transition processes induced by non-holomorphic Yukawa interactions in the minimal supersymmetric standard model (MSSM). When supersymmetry is broken, the coupling structures between Higgs doublets and leptons are modified and flavor-changing neutral currents could be generated. In the framework of the MSSM, we calculate those effects to the rates for $\meg$, $\meee$, and $μ$-$e$ conversion in nuclei. We perform more detailed calculations of the lepton flavor violating (LFV) operators in the heavy Higgs decoupling limit than previous works, and show the accurate $\tanβ$ …
The possibility of detecting double flavor violating top quark transitions $t \to u_iτμ$ ($u_i=u,c$) is explored in a model--independent manner, using the effective Lagrangian approach. Low--energy data, on high precision measurements, and current experimental limits are used to constraint the $tu_iH$ and $Hτμ$ vertices and then to calculate the branching ratio BR$(t \to u_iτμ)$. If in the Standard Model BR$(t \to u_iτμ)$ is of the order of $10^{-13}$$-10^{-14}$, higgs--mediated double flavor violating top quark decays can occur with branching ratios ranging from $10^{-3}$ to $10^{-4}$ for 114…
We perform a study of neutrinoless double beta ($0νββ$) decay mediated by the lightest neutralino of arbitrary mass in the Minimal Supersymmetric Standard Model (MSSM) under the presence of R-parity violating trilinear interactions. In this scenario, the exchange of the lightest neutralino can result in $0νββ$ decay of either long-range or short-range behaviour, depending on the neutralino mass. Using nuclear matrix elements calculated in the Interacting Boson Model, we use an interpolation between the long- and short-range behaviours with an approximate formula. The non-observation of $0νββ$ …
We consider an effective nondiagonal coupling $H\barμτ$ and present the analysis of the Higgs boson mediated lepton-flavor violating (LFV) reaction $μ^-μ^+ --> μτ$. For a Higgs boson mass around 115 GeV and convenient values of the strength of the coupling $H\barμτ$, which are within the bounds obtained from the experimental limits on the LFV decays $τ-->ημ$ and $τ-->μγ$, we found that there would be up to a few hundreds of $μτ$ events per year at a muon collider running with an integrated luminosity of $1 fb^{-1}$. We paid special attention on the background for this LFV reaction, which arise…
The rare top quark couplings $tu_iγ$ and $tu_iγγ$ ($u_i=u,c$) induced at the one-loop level by a flavor violating $tu_iH$ vertex are studied within the context of an effective Yukawa sector that incorporates $SU_L(2)\times U_Y(1)$-invariant operators of up to dimension six. Data on the recently observed $D^0-\overline{D^0}$ mixing are employed to constrain the $tu_iH$ vertex, which is then used to predict the $t\to u_iH$, $t\to u_iγ$, and $t\to u_iγγ$ decays, as well as the $γγ\to \bar{t}u_i+t\bar{u}_i$ reaction in the context of the ILC. It is found that the $t\to cH$ and $t\to cγγ$ decays ca…
We investigate a neutrino mass model in which the neutrino data is accounted for by bilinear R-parity violating supersymmetry with anomaly mediated supersymmetry breaking. We focus on the CERN Large Hadron Collider (LHC) phenomenology, studying the reach of generic supersymmetry search channels with leptons, missing energy and jets. A special feature of this model is the existence of long lived neutralinos and charginos which decay inside the detector leading to detached vertices. We demonstrate that the largest reach is obtained in the displaced vertices channel and that practically all of th…
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