We investigate the pair production process e^+e^- → H^+H^- in the framework of the scotogenic model. The production mechanism receives contributions at tree level from photon and Z-boson exchange, as well as from t-channel exchange of the new singlet right-handed fermions N_1,2,3. where neutrino masses are generated radiatively and one of the singlet right-handed fermions serves as a viable dark matter candidate. We evaluate the individual contributions of these diagrams and compute the total production cross section after imposing all relevant theoretical and experimental constraints on the model parameters, including those associated with dark matter relic abundance and direct detection limits. Our results demonstrate that the dominant contribution to the cross section originates from the exchange of the singlet fermions N_1,2,3, particularly from the dark matter component of the spectrum. In addition, we examine the dependence of the cross section on the center-of-mass energy for several benchmark scenarios in the allowed parameter space. These predictions can be probed at future high-energy e^+e^- colliders, providing a sensitive test of the scotogenic framework and the role of fermionic dark matter, as well as enabling more stringent constraints on the model parameters.

Recent anomalies in B-meson decays, such as deviations in RD(*) and B→Kνν¯, suggest possible lepton flavor universality violation and new exotic interactions. In this work, we explore these anomalies within a non-minimal SU(5) grand unified theory (GUT) framework, which introduces a 45-dimensional Higgs representation predicting exotic scalar particles, including the leptoquark R2 and diquark S6. The R2 leptoquark addresses charged current anomalies in b → cτν transitions, the S6 diquark contributes to nonleptonic neutral current processes, such as B → Kπ, while at the loop level, diagrams involving the exchanges of the leptoquark, diquark, and the Standard Model particles contribute to B→Kνν¯, offering solutions to longstanding puzzles.

In the Standard Model, the $$c \rightarrow u\nu {\bar{\nu }}$$ c → u ν ν ¯ transition arises only at the one-loop level, leading to extremely suppressed branching ratios for the corresponding three-body decays of charmed hadrons. This suppression motivates the search for possible enhancements from physics beyond the Standard Model. In this work, we study the contributions to the $$c \rightarrow u\nu {\bar{\nu }}$$ c → u ν ν ¯ transition from the $$R^{a2}_2$$ R 2 a 2 scalar leptoquark predicted in the Non-Minimal SU(5) GUT framework. We derive constraints on the model parameters using the recent BESIII results on $$D^0 \rightarrow \pi ^0\nu {\bar{\nu }}$$ D 0 → π 0 ν ν ¯ and available data on $$D^0$$ D 0 – $$\bar{D}^0$$ D ¯ 0 mixing. Additional bounds from direct LHC searches for scalar leptoquarks, lepton flavor violation processes, and the LHCb upper limit on $$\mathcal {B}(D^0 \rightarrow \mu ^+ \mu ^-)$$ B ( D 0 → μ + μ - ) are also taken into account. After imposing all constraints, we show that the branching ratios of the three-body charmed hadron decays with missing energy can be enhanced up to $${{\mathcal {O}}}(10^{-6})$$ O ( 10 - 6 ) .

This study presents a sensitivity analysis of exotic Higgs boson decays at the electron–positron stage of the Future Circular Collider (FCC-ee), performed within the FCCAnalyses framework. The analysis investigates Higgs boson production in association with a Z boson in electron–positron collisions at a center-of-mass energy of 240 GeV. The Higgs boson is assumed to decay into a pair of long-lived scalar particles, while the Z boson decays leptonically. A hadronic final state is considered, in which the long-lived scalars subsequently decay into bottom–antibottom quark pairs. The simulation chain is implemented using the FCCAnalyses framework, with event generation performed using MadGraph and Pythia, and detector effects modeled with Delphes. Displaced vertices arising from the decays of long-lived particles are reconstructed using the FCCAnalyses implementation of the LCFIPlus secondary vertex finding algorithm, enhanced with extended features such as customized track selection. The final event selection requires the reconstruction of a Z boson together with at least two displaced vertices. This strategy efficiently suppresses Standard Model backgrounds while retaining at least three expected signal events, including statistical uncertainties, over most of the explored parameter space. The study considers scalar masses of 20 GeV and 60 GeV and mixing angles of 10^-5, 10^-6, and 10^-7. The results demonstrate that FCC-ee will be sensitive to long-lived scalars with decay lengths ranging from approximately 1 mm to 10 m, with optimal sensitivity around a decay length of 0.3 m.

We investigate R-D and R-D* anomalies in a low scale left-right symmetric model based on SU(3)(C) x SU(2)(L) x SU(2)(R) x U(1)(B-L) with a simplified Higgs sector consisting of only one bidoublet and one SU(2)(R) doublet. The Wilson coefficients relevant to the transition b -> c tau nu are derived by integrating out the charged Higgs H-+/- boson, which gives the dominant contributions. We emphasize that the charged Higgs effects, with the complex right-handed quark mixing matrix, can account for both R-D and R-D* anomalies simultaneously, while adhering to a set of significant constraints including, for instance, BR(B-c(-) -> tau(-)(nu) over bar (tau)) and B-s(d) - (B) over bar (s(d)) mixing. In relation to this, we show that the predicted values of the D-*, tau longitudinal polarizations and P-tau (D) can be affected for the set of the parameters of the model resolving the R-D,R-D* anomalies.

The early Universe was characterized by the presence of heavy particles that decoupled at different temperatures leading to different phases of the Universe. This had some consequences on the time evolution of the thermodynamic and the cosmological parameters characterizing each phase of the early Universe. In this study, we derive the analytic expressions of the equations governing the time evolution of these parameters using the equations of state of the MIT bag model describing the quark–gluon plasma era. In addition, using the equations of state derived from considering the recent results of the lattice QCD simulations, we solve numerically the differential equation governing the time evolution of the energy density in the early Universe. The time evolution of the parameters under concern including the energy density, entropy density, temperature, pressure in addition to Hubble parameter and scale factor can then be estimated as will be presented in this work.

We investigate $$R_D$$ R D and $$R_{D^*}$$ R D ∗ anomalies in a low scale left–right symmetric model based on $$SU(3)_C\times SU(2)_L\times SU(2)_R\times U(1)_{B-L}$$ S U ( 3 ) C × S U ( 2 ) L × S U ( 2 ) R × U ( 1 ) B - L with a simplified Higgs sector consisting of only one bidoublet and one $$SU(2)_R$$ S U ( 2 ) R doublet. The Wilson coefficients relevant to the transition $$b\rightarrow c\tau \nu $$ b → c τ ν are derived by integrating out the charged Higgs $$H^\pm $$ H ± boson, which gives the dominant contributions. We emphasize that the charged Higgs effects, with the complex right-handed quark mixing matrix, can account for both $$R_D$$ R D and $$R_{D^*}$$ R D ∗ anomalies simultaneously, while adhering to a set of significant constraints including, for instance, $$\textrm{BR}(B^-_c \rightarrow \tau ^- \bar{\nu }_\tau ) $$ BR ( B c - → τ - ν ¯ τ ) and $$B_{s(d)}-\bar{B}_{s(d)}$$ B s ( d ) - B ¯ s ( d ) mixing. In relation to this, we show that the predicted values of the $$D^*$$ D ∗ , $$\tau $$ τ longitudinal polarizations and $$P_\tau (D)$$ P τ ( D ) can be affected for the set of the parameters of the model resolving the $$R_{D,D^*}$$ R D , D ∗ anomalies.

AbstractWe investigate $$R_D$$ R D and $$R_{D^*}$$ R D ∗ anomalies in a low scale left–right symmetric model based on $$SU(3)_C\times SU(2)_L\times SU(2)_R\times U(1)_{B-L}$$ S U ( 3 ) C × S U ( 2 ) L × S U ( 2 ) R × U ( 1 ) B - L with a simplified Higgs sector consisting of only one bidoublet and one $$SU(2)_R$$ S U ( 2 ) R doublet. The Wilson coefficients relevant to the transition $$b\rightarrow c\tau \nu $$ b → c τ ν are derived by integrating out the charged Higgs $$H^\pm $$ H ± boson, which gives the dominant contributions. We emphasize that the charged Higgs effects, with the complex right-handed quark mixing matrix, can account for both $$R_D$$ R D and $$R_{D^*}$$ R D ∗ anomalies simultaneously, while adhering to a set of significant constraints including, for instance, $$\textrm{BR}(B^-_c \rightarrow \tau ^- \bar{\nu }_\tau ) $$ BR ( B c - → τ - ν ¯ τ ) and $$B_{s(d)}-\bar{B}_{s(d)}$$ B s ( d ) - B ¯ s ( d ) mixing. In relation to this, we show that the predicted values of the $$D^*$$ D ∗ , $$\tau $$ τ longitudinal polarizations and $$P_\tau (D)$$ P τ ( D ) can be affected for the set of the parameters of the model resolving the $$R_{D,D^*}$$ R D , D ∗ anomalies.

We investigate R_D and R_D^* anomalies in a low scale left–right symmetric model based on SU(3)_C× SU(2)_L× SU(2)_R× U(1)_B-L with a simplified Higgs sector consisting of only one bidoublet and one SU(2)_R doublet. The Wilson coefficients relevant to the transition b→ cτν are derived by integrating out the charged Higgs H^± boson, which gives the dominant contributions. We emphasize that the charged Higgs effects, with the complex right-handed quark mixing matrix, can account for both R_D and R_D^* anomalies simultaneously, while adhering to a set of significant constraints including, for instance, BR(B^-_c →τ ^- ν̅_τ ) and B_s(d)-B̅_s(d) mixing. In relation to this, we show that the predicted values of the D^* , τ longitudinal polarizations and P_τ (D) can be affected for the set of the parameters of the model resolving the R_D,D^* anomalies.

Direct CP asymmetry in semi-leptonic τ decays is an intriguing hint for new physics beyond the standard model. We investigate the CP asymmetry in τ^-→K_S^0π^-ν_τ and τ− → K−π0ντ decays in the context of the non-minimal SU(5) model, with 45-dimensional Higgs multiplet. We show that the associate color-triplet scalar, which is a natural example of a scalar leptoquark, can mediate the τ→ suν_τ transition and account for the observed 2.8 σ discrepancy in A_CP(τ^-→K_S^0π^-ν_τ) compared to the SM expectation. We also predict a sizable ACP(τ− → K−π0ντ), of 𝒪 (10−3), which can be experimentally accessible in current and near future experiments.

We investigate the impact of the recent results concerning the fit to the global data on neutrino oscillations, the direct detection experiments of the dark matter, and the Planck measurement for the relic density on the parameter space relevant to the fermionic dark matter sector of the scotogenic model. In this sector, the lightest new singlet fermion is adopted to be the dark matter candidate. We show that masses of dark matter and new scalars smaller than or equal to 1 TeV satisfying the strongest constraints arise from |Δm2 31| Δm2 21 , μ → eγ, and direct detection constraints do not guarantee that Ωˆh2 lies in the 2σ range provided recently by the Planck satellite measurements with Δm2i j = m2i −m2j . This result is valid for the case that the lightest new singlet fermion N1 is the dark matter candidate and for the scenarios of normal and inverted ordering of neutrino masses. Moreover, we find that if N1 is degenerate or nearly degenerate in mass with the next lightest singlet fermion N2, the new contributions from coannihilation of N1 and N2 become relevant to reduce the values of the Yukawa coupling needed for producing the relic density of dark matter within 2σ range of its measured value while respecting the imposed constraints.

Abstract We investigate $$R_D$$ R D and $$R_{D^*}$$ R D ∗ anomalies in a low scale left–right symmetric model based on $$SU(3)_C\times SU(2)_L\times SU(2)_R\times U(1)_{B-L}$$ S U ( 3 ) C × S U ( 2 ) L × S U ( 2 ) R × U ( 1 ) B - L with a simplified Higgs sector consisting of only one bidoublet and one $$SU(2)_R$$ S U ( 2 ) R doublet. The Wilson coefficients relevant to the transition $$b\rightarrow c\tau \nu $$ b → c τ ν are derived by integrating out the charged Higgs $$H^\pm $$ H ± boson, which gives the dominant contributions. We emphasize that the charged Higgs effects, with the complex right-handed quark mixing matrix, can account for both $$R_D$$ R D and $$R_{D^*}$$ R D ∗ anomalies simultaneously, while adhering to a set of significant constraints including, for instance, $$\textrm{BR}(B^-_c \rightarrow \tau ^- \bar{\nu }_\tau ) $$ BR ( B c - → τ - ν ¯ τ ) and $$B_{s(d)}-\bar{B}_{s(d)}$$ B s ( d ) - B ¯ s ( d ) mixing. In relation to this, we show that the predicted values of the $$D^*$$ D ∗ , $$\tau $$ τ longitudinal polarizations and $$P_\tau (D)$$ P τ ( D ) can be affected for the set of the parameters of the model resolving the $$R_{D,D^*}$$ R D , D ∗ anomalies.

The recent measurements on a number of b → sμ + μ − processes have manifested anomalous results which could be early evidence for the presence of new physics beyond the standard model in b → s transitions. Supposing this to be the case, we entertain the possibility that a heavy Z ′ boson is responsible for these anomalies and that it also affects the rare nonleptonic decays of the B ¯ s meson which receive substantial contributions from the so-called penguin diagrams. The majority of these B ¯ s decay modes are not yet discovered, and within the standard model their rates have been estimated to be relatively suppressed. Taking into account various constraints, we find that the Z ′ effects can enlarge the rates of a few of the modes, especially B ¯ s → η π 0 , ϕ π 0 , η ω , ϕ ω , considerably above their standard-model expectations. Consequently this Z ′ scenario may be experimentally testable in the near future.

We investigate the phenomenology of an extension of the Standard Model (SM) by a non-abelian gauge group $SU(2)_{HS}$ where all SM particles are singlets under this gauge group, and a new scalar representation $\phi$ that is singlet under SM gauge group and doublet under $SU(2)_{HS}$. In this model, the dark matter (DM) candidates are the three mass degenerate dark photons $A_{i}$ $(i=1,2,3)$ of $SU(2)_{HS}$; and the hidden sector interacts with the (SM) particles through the Higgs portal interactions. Consequently, there will be a new CP-even scalar $\eta$ that could be either heavier or lighter than the SM-like Higgs. By taking into account all theoretical and experimental constraints such as perturbativity, unitarity, vacuum stability, non-SM Higgs decays, DM direct detection, DM relic density, we found viable DM is possible in the range from GeV to TeV. Within the viable parameters space, the both of the triple Higgs coupling and the di-Higgs production at LHC14 could be enhanced or reduced depending on the scalar mixing and the mass of the scalar particle $\eta$.

Abstract A general analysis of possible violation of CP in processes like $$\tau \rightarrow K\pi \nu $$ τ → K π ν , for unpolarized $$\tau $$ τ is presented. In this paper, we derive the new contributions to the effective Hamiltonian governs $$\vert \Delta S \vert =1$$ | Δ S | = 1 semileptonic tau decays in the framework of two Higgs doublet model with generic Yukawa structure and Leptoquarks models. Within these models, we list all operators, in the effective Hamiltonian and provide analytical expression for their corresponding Wilson coefficients. Moreover, we analyze the role of the different contributions, originating from the scalar, vecor and tensor hadronic currents, in generating direct CP asymmetry in the decay rate of $$\tau ^-\rightarrow K^-\pi ^0\nu _\tau $$ τ - → K - π 0 ν τ . We show that non vanishing direct CP asymmetry in the decay rate of $$\tau ^-\rightarrow K^-\pi ^0\nu _\tau $$ τ - → K - π 0 ν τ can be generated due to the presence of both, the weak phase in the Wilson coefficient corresponding to the tensor operator and the strong phase difference resulting from the interference between the form factors expressing the matrix elements of the vector and tensor hadronic currents. After taking into account all relevant constraints, we find that the generated direct CP asymmetry is of order $$10^{-8}$$ 10 - 8 which is several orders of magnitude larger than the standard model prediction. We show also that, in two Higgs doublet model with generic Yukawa structure , direct local or non integrated CP violation can be as large as 0.3 % not far from experimental possibilities. This kind of asymmetry can be generated due to the interference between vector and scalar contributions with different weak phases which is not the case in the SM.

Abstract We investigate the possibility that scalar leptoquarks generate consequential effects on the flavor-changing neutral-current decays of charmed hadrons into final states with missing energy "Image missing" carried away by either standard model or sterile neutrinos. We focus on scenarios involving the R2, $$ {\tilde{R}}_2 $$ R ˜ 2 , and $$ {\overline{S}}_1 $$ S ¯ 1 leptoquarks and take into account various pertinent constraints, learning that meson-mixing ones and those inferred from collider searches can be of significance. We find in particular that the branching fractions of charmed meson decays D →"Image missing", M = π, ρ, and Ds→"Image missing" and singly charmed baryon decays $$ {\Lambda}_c^{+} $$ Λ c + →"Image missing" and Ξc→"Image missing" are presently allowed to attain the 10−7-10−6 levels if induced by R2 and that the impact of $$ {\tilde{R}}_2 $$ R ˜ 2 is comparatively much less. In contrast, the contributions of $$ {\overline{S}}_1 $$ S ¯ 1 , which couples to right-handed up-type quarks and the sterile neutrinos, could lead to branching fractions as high as order 10−3. This suggests that these charmed hadron decays might be within reach of the BESIII and Belle II experiments or future super charm-tau factories and could serve as potentially promising probes of leptoquark interactions with sterile neutrinos.

In this paper we investigate CP violation in charged decays of D meson. Particularly, we study the direct CP asymmetry of the Cabibbo favored non-leptonic $$D^+ \rightarrow {\bar{K}}^0 \pi ^+$$ and the doubly Cabibbo-suppressed decay mode $$D^+ \rightarrow K^0 \pi ^+$$ within standard model, two Higgs doublet model with generic Yukawa structure and left right symmetric models. In the standard model, we first derive the contributions from box and di-penguin diagrams contributing to their amplitudes which are relevant to the generation of the weak phases essential for non-vanishing direct CP violation. Then, we show that the generated phases are so tiny leading to null direct CP asymmetries of both decay modes. Regarding the two Higgs doublet model with generic Yukawa structure, after taking into account all constraints on the parameter space of the model, we show that the weak phases of the amplitudes can be enhanced compared to the standard model ones. However, the enhancement is still not enough to have sizable direct CP asymmetries. Finally, within left right symmetric models, we find that $$|A^{SM+LR}_{CP} (D^+ \rightarrow {\bar{K}}^0 \pi ^+)|\lesssim \mathcal {O}(10^{-3})$$ after respecting all relevant constraints on the parameter space of the model.

This is a sequel to our earlier paper presenting a supersymmetric Nambu–Jona–Lasinio (NJL)-type model for a real superfield composite. The model in the simplest version has only a chiral superfield (multiplet), with a strong four-superfield interaction in the Kähler potential that induces a real two-superfield composite with vacuum condensate. The latter can have supersymmetry breaking parts, which we have shown to bear nontrivial solutions under a standard nonperturbative analysis for a Nambu–Jona–Lasinio-type model on a superfield setting. In this article, we generalize our earlier analysis by allowing a supersymmetric mass term for the chiral superfield, as well as possible θ2 components for the soft supersymmetry breaking part of the condensate. We present admissible nontrivial vacuum solutions and an analysis of the resulted low energy effective theory with components of the composite becoming dynamical. The determinant of the fermionic modes is shown to be zero, illustrating the presence of the expected Goldstino.

Abstract In this paper we investigate CP violation in charged decays of D meson. Particularly, we study the direct CP asymmetry of the Cabibbo favored non-leptonic $$D^+ \rightarrow {\bar{K}}^0 \pi ^+$$ D+→K¯0π+ and the doubly Cabibbo-suppressed decay mode $$D^+ \rightarrow K^0 \pi ^+$$ D+→K0π+ within standard model, two Higgs doublet model with generic Yukawa structure and left right symmetric models. In the standard model, we first derive the contributions from box and di-penguin diagrams contributing to their amplitudes which are relevant to the generation of the weak phases essential for non-vanishing direct CP violation. Then, we show that the generated phases are so tiny leading to null direct CP asymmetries of both decay modes. Regarding the two Higgs doublet model with generic Yukawa structure, after taking into account all constraints on the parameter space of the model, we show that the weak phases of the amplitudes can be enhanced compared to the standard model ones. However, the enhancement is still not enough to have sizable direct CP asymmetries. Finally, within left right symmetric models, we find that $$|A^{SM+LR}_{CP} (D^+ \rightarrow {\bar{K}}^0 \pi ^+)|\lesssim \mathcal {O}(10^{-3})$$ |ACPSM+LR(D+→K¯0π+)|≲O(10-3) after respecting all relevant constraints on the parameter space of the model.

In this paper we investigate CP violation in charged decays of D meson. Particularly, we study the direct CP asymmetry of the Cabibbo favored non-leptonic D^+ →K̅^0 π ^+ and the doubly Cabibbo-suppressed decay mode D^+ → K^0 π ^+ within standard model, two Higgs doublet model with generic Yukawa structure and left right symmetric models. In the standard model, we first derive the contributions from box and di-penguin diagrams contributing to their amplitudes which are relevant to the generation of the weak phases essential for non-vanishing direct CP violation. Then, we show that the generated phases are so tiny leading to null direct CP asymmetries of both decay modes. Regarding the two Higgs doublet model with generic Yukawa structure, after taking into account all constraints on the parameter space of the model, we show that the weak phases of the amplitudes can be enhanced compared to the standard model ones. However, the enhancement is still not enough to have sizable direct CP asymmetries. Finally, within left right symmetric models, we find that |A^SM+LR_CP (D^+ →K̅^0 π ^+)|≲𝒪(10^-3) after respecting all relevant constraints on the parameter space of the model.