We study impacts of dimension-five lepton-number violating operators associated with two same-sign weak bosons, $\ell^\pm \ell^{\prime \pm} W^\mp W^\mp$, on current and future experiments for neutrino oscillation, lepton-number violating rare processes and high-energy collider experiments. These operators can contain important information on the origin of tiny neutrino masses, which is independent of that from the so-called Weinberg operator. We examine constraints on the coefficients of the operators by the neutrino oscillation data. Upper bounds on the coefficients are also investigated by using the data for processes of lepton number violation such as neutrinoless double beta decays and $μ^-$-$e^+$ conversion. These operators can also be directly tested by searching for lepton-number violating dilepton production via the same-sign W boson fusion process at high-energy hadron colliders like the Large Hadron Collider. We find that these operators can be considerably probed by these current and future experiments.
In this review we discuss physics of the lepton sector, the anomalous dipole moment of muon, the charged lepton-flavor violation, and the electric dipole moments of charged leptons, from viewpoints of the minimal supersymmetric standard model and the extensions.
In the first part of this thesis, we consider an extension to the Standard Model composed by a Massive Vector Doublet under SU(2)L and a Left-handed Heavy Neutral Lepton. We study the production of these exotic leptons with a Same Flavor Opposite Sign standard lepton pair, and jets. We establish limits on the parameter space considering previous searches in this final state. After the limit definition, we study a modification on the event selection criteria in order to increase the possibility of probing these new particles at the Large Hadron Collider. Finally, we perform a parameter scan con…
We discuss possibilities to measure the tt-gamma and ttZ couplings at hadron and lepton colliders. We also briefly describe how these measurements can be used to constrain the parameter space of models of new physics, in particular Little Higgs models.
We examine relation between neutrino oscillation parameters and prediction of lepton flavor violation, in light of deviations from tri-bimaximal mixing. Our study shows that upcoming experimental searches for lepton flavor violation process can provide useful implications for neutrino mass spectrum and mixing angles. With simple structure of heavy right-handed neutrino and supersymmetry breaking sectors, the discovery of tau \to mu gamma decay determines neutrino mass hierarchy if large (order 0.1) reactor angle is established.
The International Linear Collider (ILC) will be able to precisely measure the electroweak couplings of the top in e+e- -> tt~. We compare the limits which can be achieved at the ILC with those which can be obtained in tt~gamma$ and tt~Z production at the Large Hadron Collider (LHC).
$SU(2)_L$-invariance links charged dilepton $\bar q\,q^\prime\,\ell^+\,\ell^-$ and dineutrino $\bar q\, q^\prime\, \barν\,ν$ couplings. This connection can be established using the Standard Model Effective Field Theory framework, and allows to perform complementary experimental tests of lepton universality and charged lepton flavor conservation with flavor-summed dineutrino observables. We present its phenomenological implications for the branching ratios of rare charm decays $c\to u\,ν\,\barν$ and rare $B$ decays $b\to s\,\barν\,ν$ decays.
Models of neutrino mass generation provide well motivated scenarios of Beyond-the-Standard-Model physics. The synergy between low energy and high energy LHC searches facilitates an effective approach to rule out, constrain or ideally pinpoint such models. In this proceedings report, we provide a brief overview of scenarios where searches at the LHC can help determine the mechanism of light neutrino masses and potentially falsify baryogenesis mechanisms.
In the littlest Higgs model with T-parity, the new interactions between the mirror leptons and the Standard Model leptons can induce some lepton flavor violation (LFV) processes at loop level. We study the possibility of the ILC to probe the LFV production processes $e^+e^-(γγ)\rightarrow l_{i}\bar{l}_{j}$. Our results show that the rates of $γγ\rightarrow l_{i}\bar{l}_{j}$ can reach 1 fb in optimal cases after reasonable kinematical cuts, which implies that these processes may be observed at the ILC.
We evaluate the differential cross section for the electroproduction of lepton pairs off a polarized nucleon target in the generalized Bjorken region to leading power accuracy in hard momentum. We discuss the importance of this process for phenomenology of generalized parton distributions. A special attention is given to the sensitivity of physical observables, i.e., diverse asymmetries, to their dependence on scaling variables that allows to map directly the functional two-dimensional surface of generalized parton distributions.
In supersymmetric models where the gravitino is the lightest superparticle, the next-to-lightest superparticle (NLSP) is long-lived, and hence could be collected and studied in detail. We study the prospects of direct detection of lepton flavour violation in charged slepton NLSP decays. Mixing angles in the slepton sector as small as ~ 3\times 10^{-2} (9\times 10^{-3}) could be probed at the 90% confidence level if 3\times 10^3 (3\times 10^4) sleptons could be collected.
In an effective Lagrangian description of physics beyond the standard model, gluonic couplings of leptons that respect the symmetries of the standard model occur in operators of dimension eight. Normally the effect of such operators is much suppressed in processes that occur at energies below the scale of new physics. For this reason usual studies of the effective Lagrangian are limited to the lowest dimension operators which is typically six. We point out that the large parton luminosity for gluon-gluon interactions at the LHC places these gluonic couplings to leptons within observable reach …
We examine the lepton dipole moments in an extension of the Standard Model (SM), which contains vector-like leptons that couple only to the second-generation SM leptons. The model naturally leads to sizable contributions to the muon $g-2$ and the muon electric dipole moment (EDM). One feature of this model is that a sizable electron EDM is also induced at the two-loop level due to the existence of new vector-like leptons in the loops. We find parameter regions that can explain the muon $g-2$ anomaly and are also consistent with the experimental constraints coming from the electron EDM and the …
The possibility of discovering heavy Majorana neutrinos and lepton number violation via the like sign dilepton signal at hadron super- colliders is investigated. The cross-sections for the production of these neutrinos singly as well as in pairs are computed both in three and four generation scenarios within the framework of the gauge group $SU(2)_L \otimes U(1)_Y$ and the dominant processes are identified. The suppression of the Standard model background by suitable kinematical cuts is also discussed.
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…
One of the main neutrino oscillation parameters whose value has not been determined very precisely is the leptonic $δ_{CP}$ phase. Since neutrinos have a tiny but finite mass they can undergo decay both visibly and invisibly. The effect of invisible decay of the third mass eigen state $ν_3$ on the sensitivity to $δ_{CP}$ is analysed here using atmospheric neutrino and anti-neutrino events. Effects of detector resolutions and systematic uncertainties are studied to identify the optimum resolutions and efficiencies required by a detector to obtain a significant sensitivity even in presence of de…
We study the LHC sensitivity to a $W'$ produced via bottom and charm quarks and decaying to $τ$ flavor leptons in the mass range 200-1000 GeV. We show that the extra $b$ quarks necessitated by the production mechanism can improve the background rejection compared to an inclusive analysis relying solely on $τ$-tagging and $E_{T}^{\text{miss}}$. We present prospective limits on the couplings and compare them to the best fit to the $R(D^{(\ast)})$ anomalies in $B$ meson decays.
We study leptonic flavor and CP violating observables in supersymmetric (SUSY) models with heavy sfermions, which is motivated by the recent results of the LHC experiments (i.e., the discovery of the Higgs-like boson with the mass of about 126 GeV and the negative searches for the superparticles). Even if the sfermion masses are of O(10-100 TeV), signals may be within the reach of future leptonic flavor- and CP-violation experiments assuming that the off-diagonal elements of the sfermion mass matrices are unsuppressed compared to the diagonal ones. We also consider the SUSY contribution to the…
We study a CP and T violating triple (spin) correlation in the muon to electron conversion in nuclei in the context of the seesaw mechanism. After concluding that the results are negative for all three seesaw types, we turn to the left-right symmetric theories as the original source of seesaw. We find that in general this correlation is of order one which offers a hope of observing CP violation in lepton flavor violating processes for a L-R scale below around 10-30 TeV. We discuss the conditions that could render to (unlikely) conspiracies as to suppress the CP violating effects.
We study a purely leptonic signature of the Randall-Sundrum scenario with Standard Model fields in the bulk at LHC: the contribution from the exchange of Kaluza-Klein (KK) excitations of gauge bosons to the clear Drell-Yan reaction. We show that this contribution is detectable (even with the low luminosities of the LHC initial regime) for KK masses around the TeV scale and for sufficiently large lepton couplings to KK gauge bosons. Such large couplings can be compatible with ElectroWeak precision data on the Zff coupling in the framework of the custodial O(3) symmetry recently proposed, for sp…
We complement the analysis of the anomalous top-Higgs coupling effects on the secondary lepton distributions in the associated production of the top-quark pair and Higgs boson in proton-proton collisions at the LHC of the former work by one of the present authors by taking into account the quark-antiquark production mechanism. We also present simple arguments which explain why the effects of the scalar and pseudoscalar anomalous couplings on the unpolarized cross section of the process are completely insensitive to the sign of either of them.
Since decays to four leptons is widely considered a promising way to search for the Higgs particle, we show how the same final state can also be used to search for signals of CP nonconservation. Energy asymmetries and triple correlations are related to parameters in the underlying CP violating effective interaction at the $H^0$-$W$-$W$ and $H^0$-$Z$-$Z$ vertex. Expected size of the effects are shown to be small for both the Sandard Model and its extension with an extra Higgs doublet.
We establish model independent bounds on the anomalous magnetic and electric dipole moments of the tau-lepton using the two-photon processes $γγ\to τ^+τ^-$ and $γγ\to τ^+τ^-γ$. We use ${\cal L}=10, 50, 100, 300, 500, 1000, 1500, 2000, 3000 \hspace{0.8mm}fb^{-1}$ of data collected with the future $e^+e^-$ linear collider such as the CLIC at $\sqrt{s}=380, 1500, 3000 \hspace{0.8mm}GeV$ and we consider systematic uncertainties of $δ_{sys}=0, 3, 5\hspace{1mm}\%$. Precise bounds at $95\%$ C. L. on the anomalous dipole moments to the tau-lepton $-0.00015\leq \tilde{a}_τ\leq 0.00017$ and $|\tilde{d}_…
The most recent measurements of the observables $R_{D^{(*)}}$ are in tension with the Standard Model offering hints of New Physics in $b\rightarrow c \ell \barν_{\ell}$ transitions. Motivated by these results, in this work we present an analysis on their $b\rightarrow u \ell \barν_{\ell}$ counterparts (for $\ell=e, ~μ, ~τ$). Our study has three main objectives. Firstly, using ratios of branching fractions, we assess the effects of beyond the Standard Model scalar and pseudoscalar particles in leptonic and semileptonic $B$ decays ($B^-\rightarrow \ell^- \barν_{\ell}$, $\bar{B}\rightarrow π\ell …
We discuss the production at $e^+e^-$ colliders of Higgs bosons in association with both the scalar leptons and the lightest neutralinos in the Minimal Supersymmetric extension of the Standard Model. While the rates for associated Higgs production with neutralinos and first/second generation sleptons are rather tiny, the cross section for the production of the lightest Higgs boson $h$ with scalar $τ$ lepton pairs can reach the femtobarn level at c.m. energies at and above 500 GeV in favorable regions of the parameter space, making this process potentially detectable at a high-luminosity $\ee$ …
The evaluation, systematic analysis and numerical study of the semileptonic $τ$-lepton decays with two mesons in the final state has been made in the frame of the standard model extended by right handed neutrinos. In the analysis, heavy-neutrino nondecoupling effects, finite quark masses, quark and meson mixings, finite widths of vector mesons, chiral symmetry breakings in vector-meson--pseudoscalar-meson vertices and effective Higgs-boson--pseudoscalar-meson couplings have been included. Numerical estimates reveal that the decays $τ^-\to e^-π^-π^+$, $τ^-\to e^-K^-K^+$ and $τ^-\to e^-K^0\bar{K…
The doubly charged Higgs bosons $Δ^{--}$ that are present in exotic Higgs representations can have lepton-number-violating couplings to $e^-e^-$. We discuss general constraints and phenomenology for the $Δ^{--}$ and demonstrate that extremely small values for the $e^-e^-\rightarrowΔ^{--}$ coupling (some 8 orders of magnitude smaller than the current limit) would produce observable signals for $Δ^{--}$ production in direct $s$-channel production at an $e^-e^-$ collider.
We discuss the collider signatures of electroweak (1,0)-mode excitations in the framework of two universal extra dimension (2UED) at the LHC and ILC. In general, pair production of electroweak (1,0)-mode particles of 2UED gives rise to multi lepton plus missing transverse momentum signal. Upto 1/R = 400 GeV two lepton plus missing transverse momentum signal and upto 1/R = 600 GeV three lepton plus missing transverse momentum signal stands over the $5σ$ standard deviation of the Standard Model background at the LHC with $100 fb^{-1}$ integrated luminosity. At ILC we study single photon plus mis…
A low energy non-unitary leptonic mixing matrix is a generic feature of many extensions of the Standard Model. In such a case, the task of future precision neutrino oscillation experiments is more ambitious than measuring the three mixing angles and the leptonic (Dirac) CP-phase, i.e., the accessible parameters of a unitary leptonic mixing matrix. A non-unitary mixing matrix has 13 parameters that affect neutrino oscillations, out of which four are CP-violating. In the scheme of Minimal Unitarity Violation (MUV) we analyse the potential of a Neutrino Factory for determining or constraining the…
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 discuss lepton number violating processes in the context of long-baseline neutrino oscillations. We summarise and compare neutrino flavour oscillations in quantum mechanics and quantum field theory, both for standard oscillations and for those that violate lepton number. When the active neutrinos are Majorana in nature, the required helicity reversal gives a strong suppression by the neutrino mass over the energy, $(m_ν/E_ν)^{2}$. Instead, the presence of non-standard lepton number violating interactions incorporating right-handed lepton currents at production or detection alleviate the mas…
We study the model with three right-handed neutrinos which masses are smaller than the weak scale ${\cal O}(10^2)$ GeV (called as the $ν$MSM). The model can explain the origin of neutrino masses by the seesaw mechanism, offer a candidate of dark matter and realize the baryogenesis via neutrino oscillation. The seesaw mechanism at such energy scales can induce phenomenon which are observable by experiments. As an example, we discuss the lepton universality of charged kaon decays in this model. It is shown that the heavy neutral leptons accounting for the neutrino masses and the cosmic baryon as…
We study the search potential of heavy triplet leptons in Type III Seesaw mechanism at future high-energy and high-luminosity muon colliders. The impact of up-to-date neutrino oscillation results is taken into account on neutrino parameters and the consequent decay patterns of heavy leptons in Type III Seesaw. The three heavy leptons in the Casas-Ibarra parametrization with diagonal unity matrix are distinguishable in their decay modes. We consider the pair production of charged triplet leptons $E^+ E^-$ through both $μ^+μ^-$ annihilation and vector boson fusion (VBF) processes. The leading-or…
We study the impact that future lepton flavor violating experiments will have on the viable parameter space of the scotogenic model. Within this model, the dark matter particle is assumed to be the lightest singlet fermion and two cases are considered depending on how its relic density is obtained: via self-annihilations or via coannihilations with the scalars. For each case, a scan over the parameter space of the model is used to obtain a large sample of viable points, which we subsequently analyze. We find that future lepton flavor violating experiments, in particular those searching for $μ\…
We study the effects of the identical leptons in the final state of the $B^+\to \ell^+ \ell^- \ell^+\barν_{\ell}$ decay. The amplitude of the process is described by the same form factors as the amplitude of the ${B\to \ell \ell \ell'\barν'_{\ell}}$ decay for non-identical leptons in the final state. However, the differential distributions are strongly different, as the ${B^+\to \ell^+ \ell^- \ell^+\barν_{\ell}}$ amplitude contains both the direct ($M_a$) and the exchange ($M_b$) diagrams. We calculate a number of the differential distirbutions. In particular, we propose an interesting observa…
Probing quark-lepton correlation in GUTs with high-precision neutrino measurements
Hangzhou Institute for Advanced Study, UCAS（杭州高等研究院）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）
We consider a scenario where light bino is the next-to-lightest supersymmetric particle (NLSP) and gravitino/axino is the lightest superysmmetric particle (LSP). For a bino mass less than or around hundred GeV, it can be pair produced at the future lepton colliders through $t-$channel slepton exchange, subsequently decaying into a gravitino/axino plus a photon. We study the prospects to look for such binos at the future colliders and find that a bino mass around 100 GeV can be probed at the $2σ$ ($5σ$) level for a slepton below 2 TeV (1.5 TeV) with a luminosity 3 $ab^{-1}$. For a bino mass aro…
Fermion compositeness and other new physics can be signalled by the presence of a strong four-fermion contact interaction. Here we present a study of $\ell\ell qq$ and $\ell\ell\ell'\ell'$ contact interactions using the reactions: $\ell^+ \ell^- \to \ell'^+\ell'^-,b\bar b, c\bar c$ at future $e^+e^-$ linear colliders with $\sqrt s=0.5-5$ TeV and $μ^+μ^-$ colliders with $\sqrt s=0.5,4$ TeV. We find that very large compositeness scales can be probed at these machines and that the use of polarized beams can unravel their underlying helicity structure.
We propose a strategy for distinguishing the Dirac / Majorana character of heavy neutrinos with masses below the $W$ boson mass, using purely leptonic decays at the LHC. The strategy makes use of a forward-backward asymmetry of the opposite charge lepton in the $W^{+}\rightarrow l^{+}l^{+}l^{'-}ν$ decay. In order to check the experimental feasibility of the model, we show, through a numerical analysis, that in the decay $W^{+}\rightarrow e^{+}e^{+}μ^{-}ν$ the two positrons in the final state can be distinguished for different ranges of the heavy neutrino masses. Finally, we estimated the numbe…
To explain the small neutrino masses, heavy Majorana neutrinos are introduced in the left-right twin Higgs model. The heavy neutrinos, together with the charged scalars and the heavy gauge bosons, may contribute large mixings between the neutrinos and the charged leptons, which may induce some distinct lepton flavor violating processes. We will check the \bar \ell_i \ell_j (i,j= e,μ,τ,i\neq j) productions in the γγcollision in the left-right twin Higgs model, and find that the production rates may be large in some specific parameter space, in the optimal cases even possible to be detected with…
It has been argued in the literature that the search for the slepton oscillation phenomenon can be a powerful probe of intergenerational mixing between sleptons, once sleptons are found at future colliders. In this article we estimate possible reach of future lepton colliders in probing left-handed slepton flavor mixing, especially mixing between the first and third generations, on which constraints imposed by other processes like $τ\to e γ$ are very weak. $e^+e^-$ collider is suitable for this purpose, since it can produce, if kinematically allowed, sleptons of the first generation via t-chan…
It is shown that the hadronic dissociation of space-like $(Q^2>0)$ photons can be directly probed by performing measurements in the fragmentation region of transversely polarized and unpolarized proton beams at the electron-proton collider HERA. Measurements of momentum-distributions in the photon-fragmentation region in normal and in LRG (large rapidity gap) events are also suggested --- especially when the scattered proton or neutron in the proton-beam direction is tagged. It is pointed out that such distributions can yield useful information on the mechanisms of hadronic fragmentation in ge…
The lepton polarization asymmetry in the B\to\ell^{+}\ell^{-} decay, when one of the leptons is polarized, is investigated using the most general form of the effective Hamiltonian. The sensitivity of the asymmetry to the new Wilson coefficients is studied.Moreover, correlations between the lepton polarization asymmetry and the branching ratio is studied. It is observed that, there are not exist such regions of new Wilson coefficients, which the value of branching ratio coincides with SM result while the lepton polarization does not, i.e new physics effects can be established by studying lepton…
We point out unique relations between the decay widths for leptoquarks and Higgs bosons that can be used to test the unification of quarks and leptons at the TeV scale. We discuss the main predictions of the minimal theory for quark-lepton unification and show how the different decays for leptoquarks and Higgses are related by the symmetry of the theory.
If pairs of new colored particles are produced at the Large Hadron Collider, determining their quantum numbers, and even discovering them, can be non-trivial. We suggest that valuable information can be obtained by measuring the resonant signals of their near-threshold QCD bound states. If the particles are charged, the resulting signatures include photons and leptons and are sufficiently rich for unambiguously determining their various quantum numbers, including the charge, color representation and spin, and obtaining a precise mass measurement. These signals provide well-motivated benchmark …
We evaluate the decays $\ell_1^\pm \to \ell_2^\pm γ$, $Z \to \ell_1^+ \ell_2^-$, and $h \to \ell_1^+ \ell_2^-$, where $\ell_1$ and $\ell_2$ are charged leptons with different flavours and $h$ is the scalar particle with mass 125.25 GeV, in a two-Higgs-doublet model where all the Yukawa-coupling matrices conserve the lepton flavours but the Majorana mass terms of the right-handed neutrinos break the flavour lepton numbers. We find that (1) the decays $\ell_1^\pm \to \ell_2^\pm γ$ require large Yukawa couplings and very light right-handed neutrinos in order to be visible, (2) the decays $Z \to \…
A sterile neutrino at GeV mass scale is of particular interest in this work. Though not take part in neutrino oscillation, the sterile neutrino can induce flavor violating semileptonic and leptonic decay of $K, D$ and $B$ mesons. We calculated a box diagram contribution in these processes. By making use of current experiment limit of lepton flavor violating decays $M^+_h\to M_l^+\ell_1^+\ell_2^-$ and $M^0\to \ell_1^-\ell_2^+$, we explore the allowed parameter space of $U_{e4}$ and $U_{μ4}$ in different mass ranges. Generally speaking, both channels give a limit to the product of $U_{e4}$ and $…
If massive neutrinos are Majorana particles, then the lepton number should be violated and neutrino-antineutrino oscillations will take place. In this talk, we present the properties of CP violation in neutrino-antineutrino oscillations with a non-unitary leptonic flavor mixing matrix, which naturally arises in the type-I seesaw model due to the mixing between light and heavy Majorana neutrinos. Taking into account current experimental bounds on the leptonic unitarity violation, we show that the CP asymmetries induced by the non-unitary mixing parameters can significantly deviate from those in…
Supersymmetry with bilinear R-parity violation provides a predictive framework for neutrino masses and mixings in agreement with current neutrino oscillation data. The model leads to striking signals at future colliders through the R-parity violating decays of the lightest supersymmetric particle. Here we study charged scalar lepton decays and demonstrate that if the scalar tau is the LSP (i) it will decay within the detector, despite the smallness of the neutrino masses, (ii) the relative ratio of branching ratios Br({tilde tau}_1 --> e sum nu_i)/ Br({tilde tau}_1 --> mu sum nu_i) is predicte…
We studied the process $e^{+}e^{-} \to t\bar{c}+c\bar{t}$ in a R_{p} violating supersymmetric model with effects from both B- and L-violating interactions. The calculation shows that it is possible to either detect the R_{p} violating signal at the Next Linear Collider or get more stringent constraints on the heavy-flavor $\rlap/R_{p}$ couplings. A comparision with results from $γγ\to t\bar{c}+ c\bar{t}$ may allow to distinguish between B- and L-violating interactions. For very clean background conditions and R_{p} violation parameters close to present limits, a future detection of B-violating…
Non-Abelian discrete symmetries provide an interesting opportunity to address the flavor puzzle in the lepton sector. However, the number of currently viable models based on such symmetries is rather large. High-precision measurements of the leptonic mixing parameters by future neutrino experiments, including ESSnuSB, T2HK, DUNE, and JUNO, will be crucial to test such models. We show that the complementarity among these experiments offers a powerful tool for narrowing down this broad class of lepton flavor models.
Inspired by the recent hints of lepton flavor universality violation in $b\to s\ell\ell$ and $b\to c\ellν$ transitions, we study lepton flavor violating exclusive $Λ_b\toΛ\ell_1^+\ell_2^-$ ($\ell_1\neq \ell_2$) decay, which is forbidden in the Standard Model. Starting from a general effective Hamiltonian for a $b\to s\ell_1^+\ell_2^-$ transition that includes vector and axial-vector operators, and scalar and pseudo-scalar operators, we derive a two-fold decay distribution of $Λ_b\toΛ\ell_1^+\ell_2^-$. The distribution helps us to construct the differential branching ratio and the lepton side f…
