Sukanta Dutta, Ashok Goyal, Mamta
We compute the one loop new physics effects to the CP even triple neutral gauge boson vertices $γ^\star γZ$, $γ^\star Z \,Z$, $Z^\star \,Z\,γ$ and $Z^\star\,Z\,Z$ in the context of Little Higgs models. In addition, we re-examine the MSSM contribution at the chosen point of SPS1a' and compare with the SM and Little Higgs models.
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We study the CP even trilinear neutral gauge boson vertices at one-loop in the context of the Standard Model and the Minimal Supersymmetric Standard Model, assuming two of the vector bosons are on-shell. We also study the changes in the form-factors when these two bosons are off-shell.
We consider the measurement of the trilinear couplings of the neutral Higgs bosons~($H^0, h^0$) in the minimal supersymmetric standard model~(MSSM) at a high energy $e^+$ $e^-$ linear collider in the light of the discovery of a Higgs boson at the CERN Large Hadron Collider~(LHC). We identify the state observed at the LHC with the lightest CP-even Higgs boson of the MSSM. We implement this constraint, as well as all the other relevant experimental constraints, on the parameter space of the MSSM in order to study the feasibility of measuring the trilinear couplings of the neutral Higgs bosons. F…
We consider the measurement of the trilinear couplings of the neutral Higgs bosons in the Minimal Supersymmetric Standard Model~(MSSM) at a high energy $e^+ e^-$ linear collider in the light of the discovery of a Higgs boson at the CERN Large Hadron Collider~(LHC). We identify the state observed at the LHC with the lightest Higgs boson~($h^0$) of the MSSM, and impose the constraints following from this identification, as well as other experimental constraints on the MSSM parameter space. In order to measure trilinear neutral Higgs couplings, we consider different processes where the heavier Hi…
We present a study of the trilinear gauge interactions in extensions of the Standard Model (SM) with several anomalous extra U(1)'s, identified in various constructions, from special vacua of string theory to large extra dimensions. In these models an axion and generalized Chern-Simons interactions for anomalies cancelation are present. We derive generalized Ward identities for these vertices and discuss their structure in the Stuckelberg and Higgs-Stuckelberg phases. We give their explicit expressions in all the relevant cases, which can be used for phenomenological studies of these models at…
We list all the lowest dimension effective operators inducing off-shell trilinear neutral gauge boson couplings Z-Z-Photon, Z-Photon-Photon, and ZZZ within the effective Lagrangian approach, both in the linear and nonlinear realizations of the SU(2)_{L} X U(1)_Y gauge symmetry. In the linear scenario we find that these couplings can be generated only by dimension eight operators necessarily including the Higgs boson field, whereas in the nonlinear case they are induced by dimension six operators. We consider the impact of these couplings on some precision measurements such as the magnetic and …
The Higgs boson effective self-couplings $λ_{hhh}$ and $λ_{HHH}$ are calculated in the framework of the Minimal Supersymmetric Standard Model (MSSM) for the complete set of one-loop diagrams with one of the Higgs bosons off-shell. The comparison with previous results, where only the leading correction terms in the limiting case of large masses of virtual particles were calculated, is carried out. We analyse the dependence of the self-couplings on the energy and ${\tt tan} β$; it is demonstrated that the tree-level self-couplings could acquire substantial one-loop corrections, which could be ph…
The four self-couplings $λ_{hhh}$, $λ_{hhH}$, $λ_{hHH}$, $λ_{HHH}$ and decay width $Γ(H \to hh)$ are calculated taken into account one-loop $t,b,c$ - (s)quarks, $τ$ - (s)lepton corrections in the framework of the Minimal Supersymmetric Standard Model (MSSM). By the example of self-couplings dependencies from $ \tg β$ and \textrm{$M_A$}, it is shown, that calculated corrections can give the essential contribution to self-couplings and decay width determined at one-loop level. The radiative corrections account becomes necessary condition for performance of Higgs potential reconstruction procedur…
We present a detailed analysis of multiple production of the lightest CP-even Higgs boson (h) of the Minimal Supersymmetric Standard Model (MSSM) at high-energy e^+ e^- colliders. We consider the production of the heavier CP-even Higgs boson (H) via Higgs-strahlung e^+e^- \to ZH, in association with the CP-odd Higgs boson (A) in e^+e^- \to AH, or via the fusion mechanism e^+e^- \to ν_e \barν_e H, with H subsequently decaying through H \to hh, thereby resulting in a pair of lighter Higgs bosons (h) in the final state. These processes can enable one to measure the trilinear Higgs couplings λ_{Hh…
We study the one loop new physics effects to the CP even triple neutral gauge boson vertices $γ^\star γZ$, $γ^\star Z Z$, $Z^\star Z γ$ and $Z^\star Z Z$ in the context of Little Higgs models. We compute the contribution of the additional fermions in Littles Higgs model in the framework of direct product groups where $[SU(2)\times U(1)]^2 $ gauge symmetry is embedded in SU(5) global symmetry and also in the framework of simple group where $SU(N)\times U(1)$ gauge symmetry breaks down to $SU(2)_L\times U(1)$. We calculate the contribution of the fermions to these couplings when $T$ parity is in…
We study pair-production as well as the triple self-couplings of the neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) at the Future International Linear $e^{+}e^{-}$ Collider (ILC) and Compact Linear Collider (CLIC). The analysis is based on the reactions $e^{+}e^{-}\to b \bar b h_ih_i, t \bar t h_ih_i$ with $h_i=h, H, A$. We evaluate the total cross-section for both $b\bar bh_ih_i$, $t\bar th_ih_i$ and calculate the total number of events considering the complete set of Feynman diagrams at tree-level. We vary the triple couplings $κλ_{hhh}$, $κλ_{Hhh}$, $κλ_{hAA}$, $κλ…
We examine trilinear gauge boson couplings (TGCs) in the context of the $SU(3)_W\otimes U(1)'$ gauge-Higgs unification scenario. The TGCs play important roles in the probes of the physics beyond the standard model, since they are highly restricted by the experiments. We discuss mass spectrum of the neutral gauge boson with brane-localized mass terms carefully and find that the TGCs and $ρ$ parameter may deviate from standard model predictions. Finally we put a constraint from these observables and discuss the possible parameter space.
The basic parameters of supersymmetric theories can be determined at future e^+e^- linear colliders with high precision. We investigate in this report how polarisation measurements in \tildeτ and \tilde{t} or \tilde{b} decays to τleptons and t quarks plus neutralinos or charginos can be used to measure \tanβ(in particular for large values) and to determine the trilinear couplings A_τ, A_t and A_b in sfermion pair production.
We analyze the flavor structure of the trilinear couplings in the different theoretical models of SUSY breaking. We generically obtain A_{ij}= A^L_i + A^R_j in all the models examined. In fact, this is the rigorous form when SUSY breaking effects appear through the Kahler metric of chiral fields or through wave-function renormalization. Indeed, the low-energy phenomenological requirements from the absence of charge and color breaking minima and the measurements in flavor changing neutral current (FCNC) observables strongly favor this restricted form of the trilinear matrices. As a straightforw…
To establish the Higgs mechanism {\it sui generis} experimentally, the Higgs self-interaction potential must be reconstructed. This task requires the measurement of the trilinear and quadrilinear self-couplings, as predicted in the Standard Model or in supersymmetric theories. The couplings can be probed in multiple Higgs production at high-luminosity e+e- linear colliders. We present the theoretical analysis for the production of neutral Higgs-boson pairs in the relevant channels of double Higgs-strahlung and associated multiple Higgs production.
In minimal Supergravity (mSUGRA) models the lightest supersymmetric particle (assumed to be the lightest neutralino) provides an excellent cold dark matter (CDM) candidate. The supersymmetric parameter space is significantly reduced, if the limits on the CDM relic density, obtained from WMAP data, are used. Assuming a vanishing trilinear scalar coupling A0 and fixed values of tan(beta), these limits result in narrow lines of allowed regions in the m0-m1/2 plane, the so called WMAP strips. In this analysis the trilinear coupling A0 has been varied within +/-4 TeV. A fixed non vanishing A0 value…
In a R-parity violating (RPV) model of neutrino mass with three bilinear couplings $μ_i$ and three trilinear couplings $λ'_{i33}$, where $i$ is the lepton index, we find six generic scenarios each with a distinctive pattern of the trilinear couplings consistent with the oscillation data. These patterns may be reflected in direct RPV decays of the lighter top squark or in the RPV decays of the lightest superparticle, assumed to be the lightest neutralino. Typical signal sizes at the Tevatron RUN II and the LHC have been estimated and the results turn out to be encouraging.
We consider a gaugino-mediated supersymmetry breaking scenario where in addition to the gauginos the Higgs fields couple directly to the field that breaks supersymmetry. This yields non-vanishing trilinear scalar couplings in general, which can lead to large mixing in the stop sector providing a sufficiently large Higgs mass. Using the most recent release of FeynHiggs, we show the implications on the parameter space. Assuming a gravitino LSP, we find allowed points with a neutralino, sneutrino or stau NLSP. We test these points against the results of Run 1 of the LHC, considering in particular…
Trilinear couplings of the neutral CP-even Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM) can be measured through the multiple production of the lightest CP-even Higgs boson (h) at high-energy e^+e^- colliders. This includes the production of the heavier CP-even Higgs boson (H) via e^+e^- \to ZH, in association with the CP-odd Higgs boson (A) in e^+e^- \to AH, or via e^+e^- \to ν_e \barν_e H, with H subsequently decaying through H \to hh. These processes can enable one to measure the trilinear Higgs couplings λ_{Hhh} and λ_{hhh}, which can be used to theoretically reconstruct…
An elementary Higgs boson, which is the remnant of the spontaneous symmetry breaking mechanism in the Standard Model, remains one of the most elusive particles. If a Higgs boson candidate is found at future accelerators, it becomes necessary to determine its properties, beyond the mass, production cross section and decay rates. The other crucial properties relate to the self-couplings of the Higgs boson, which are necessary to reconstruct the Higgs potential, and thereby confirm the mechanism of spontaneous symmetry breaking. In this paper we review the question of the measurability of some of…
We propose the signal $1b+1l+N_j+\etslash$ along with appropriate selection criteria for the LHC 7 TeV run, where the number of jets $(N_j)$ is $\ge$ 2 or 4. These signals can complement the canonical $Jets + \etslash$ signature since they are sensitive to the trilinear soft breaking parameter $(A_0)$ and low values of the parameter tan$β$ in the minimal supergravity (mSUGRA) model. A large region of this mSUGRA parameter space within the reach of the ongoing experiments at the LHC is disfavoured by the bound on the lightest Higgs boson mass ($m_h \ge 114.4 $ GeV) unless $A_0$ has moderate to …
The Higgs sector of the Minimal Supersymmetric Extension of the Standard Model may be described with a two Higgs doublet model with properties that depend on the soft supersymmetry breaking parameters. For instance, flavor independent CP-violating phases associated with the gaugino masses, the squark trilinear mass parameters and the Higgsino mass parameter $μ$ may lead to sizable CP-violation in the Higgs sector. For these CP-violating effects to affect the properties of the recently observed SM-like Higgs resonance, the non-standard charged and neutral Higgs bosons masses must be of the orde…
Multiple production of Higgs particles is essential to study Higgs self-couplings at future high-energy colliders. In this paper we calculated the resonance contributions to the production of three lightest neutral supersymmetric Higgs bosons in gluon fusion at LHC. The cross sections due to trilinear Higgs couplings is sizeable but the measurement of the quartic coupling hhhH(h) seems to be impossible.
We study the C and P even WWγand WWZ trilinear gauge boson vertices (TGV's), in the context of the MSSM assuming that the external W's are on their mass shell. We find that for energies less than 200 GeV squark and slepton contributions to the aforementioned couplings are two orders of magnitude smaller than those of the Standard Model (SM). In the same energy range the bulk of the supersymmetric Higgs corrections to the TGV's is due to the lightest neutral Higgs, h_0, whose contribution is like that of a Standard Model Higgs of the same mass. The contributions of the Neutralinos and Charginos…
Using the effective potential method, we computed one-loop corrections to the mass matrix of neutral Higgs bosons of the Non-Holomorphic Supersymmetric Standard Model (NHSSM) with explicit CP violation, where the radiative corrections due to the quarks and squarks of the third generation were taken into account. We observed that the non-holomorphic trilinear couplings can compete with the holomorphic ones in CP violating issues for the mass and mixing of the neutral Higgs bosons.
Pair production processes of neutral Higgs particles will allow us to study the trilinear Higgs couplings at future high--energy colliders. Several mechanisms give rise to multi--Higgs final states in hadron interactions. In the present paper we investigate Higgs pair production in gluon--gluon collisions. After recapitulating pair production in the Standard Model, the analysis of the cross sections is carried out in detail for the neutral Higgs particles in the minimal supersymmetric extension.
We analyse the Higgs sector of an $S_3$ model with three Higgs doublets and no CP violation. After electroweak breaking there are nine physical Higgs bosons, one of which corresponds to the Standard Model one. We study the scalar and gauge sectors of this model, taking into account the conditions set by the minimisation and stability of the potential. We calculate the masses, trilinear and quartic Higgs-Higgs, and Higgs-gauge couplings. We consider two possible alignment scenarios, where only one of the three neutral scalars has couplings to the gauge bosons and corresponds to the SM Higgs, an…
Neutral Higgs-boson pair production provides the possibility of studying the trilinear Higgs couplings at future high-energy colliders. We present the QCD corrections to the gluon-initiated processes in the limit of a heavy top quark in the loops and the Drell-Yan-like pair production of scalar and pseudoscalar Higgs particles. The pp cross sections are discussed for LHC energies within the Standard Model and its minimal supersymmetric extension. The QCD corrections are large, enhancing the total cross sections significantly.
We compute the one-loop corrections to the triple Higgs self-interaction $hhh$ in the framework of the Standard Model (SM), the Two Higgs Doublet Model type III (THDM-III) and the Littlest Higgs Model with T parity (LHBM+T). Our results are compared with previous results for the SM. In particular, we find that an imaginary part for the $λ_{hhh}$ form factor is induced when one of the Higgs boson legs is off-mass shell with 4-momentum magnitude higher than the Higgs boson mass. This contribution is sensitive to virtual effects of the Higgs self-interaction, that induces a radiative correction t…
We study the $C$ and $P$ even $WWγ$ and $WWZ$ trilinear gauge boson vertices (TGV's), in the context of the MSSM as functions of the soft SUSY breaking parameters $A_0, m_0, M_{1/2}$ and the momentum $q$ carried by $γ, Z$, assuming the external $W$'s are on their mass shell. We follow a complete renormalization group analysis taking into account all constraints imposed by the radiative breaking of the electroweak symmetry. It is found that for energies ${\sqrt{s}} \equiv q^2 \le 200 \; GeV$ squark and slepton contributions to the aforementioned couplings are two orders of magnitude smaller tha…
Gluon fusion is the main production mechanism for Higgs bosons with masses up to several hundred GeV in $pp$ collisions at the CERN Large Hadron Collider. We investigate the effects of the CP-violating phases on the fusion process including both the sfermion-loop contributions and the one-loop induced CP-violating scalar-pseudoscalar mixing in the minimal supersymmetric standard model. With a universal trilinear parameter assumed, every physical observable involves only the sum of the phases of the universal trilinear parameter $A$ and the higgsino mass parameter $μ$. The phase affects the lig…
We present the full one-loop corrections to charged and CP-even neutral Higgs boson decays into sfermions including also the crossed channels. The calculation was carried out in the minimal supersymmetric extension of the Standard Model and we use the on-shell renormalization scheme. For the down-type sfermions, we use DR-running fermion masses and the trilinear coupling A_f as input. Furthermore, we present the first numerical analysis for decays according to the Supersymmetric Parameter Analysis project. This requires the renormalization of the whole MSSM. The corrections are found to be num…
New heavy neutral gauge bosons Z' are predicted by many models of physics beyond the Standard Model. It is quite possible that Z's are heavy enough to lie beyond the discovery reach of the CERN Large Hadron Collider LHC, in which case only indirect signatures of Z' exchanges may emerge at future colliders, through deviations of the measured cross sections from the Standard Model predictions. We discuss in this context the foreseeable sensitivity to Z's of W^\pm-pair production cross sections at the e^+e^- International Linear Collider (ILC), especially as regards the potential of distinguishin…
We compute the rates for $q \bar{q}$ annihilation into charginos and neutralinos by taking into account the effects of supersymmetric soft phases. In particular, the phase of the $μ$ parameter gains direct accessibility via the production of dissimilar charginos and neutralinos. The phases of the trilinear soft masses do not have a significant effect on the cross sections. Our results can be important for sparticle searches at the LHC.
We study the hadroproduction of two neutral Higgs bosons in the minimal supersymmetric extension of the standard model, which provides a handle on the trilinear Higgs couplings. We include the contributions from quark-antiquark annihilation at the tree level and those from gluon-gluon fusion, which proceeds via quark and squark loops. We list compact results for the tree-level partonic cross sections and the squark loop amplitudes, and we confirm previous results for the quark loop amplitudes. We quantitatively analyze the hadronic cross sections at the CERN Large Hadron Collider assuming a fa…
In this work, the production processes of heavy neutral scalar and pseudo scalar associated with standard model gauge boson $Z_L$ at future $e^{+}e^{-}$ colliders (ILC and CLIC) are examined. The total and differential cross sections are calculated for the processes in the context of the littlest Higgs model. Also dependence of production processes to littlest Higgs model parameters in the range of compatibility with electroweak precision measurements and decays to lepton flavor violating final states are analyzed. We have found that both heavy scalar and pseudoscalar will be produced in $e^+e…
The cross sections for the multiple production of the lightest neutral Higgs boson at high--energy $e^+ e^-$ colliders are presented in the framework of the Minimal Supersymmetric extension of the Standard Model (MSSM). We consider production through Higgs--strahlung, associated production of the scalar and the pseudoscalar bosons, and the fusion mechanisms for which we will use the effective longitudinal vector--boson approximation. These cross sections allow one to determine trilinear Higgs couplings $λ_{Hhh}$ and $λ_{hhh}$, which are theoretically predicted by the Higgs potential.
In mSUGRA models the lightest supersymmetric particle (assumed to be the lightest neutralino) provides an excellent cold dark matter (CDM) candidate. The supersymmetric parameter space is significantly reduced, if the limits on the CDM relic density, obtained from WMAP data, are used. Assuming a vanishing trilinear scalar coupling A0 and fixed values of tan(beta), these limits result in narrow lines of allowed regions in the m0-m12 plane, the so called WMAP strips. In this analysis the trilinear coupling A0 has been varied within +/-4TeV resulting in largely extended areas in the m0-m12 plane …
The Higgs boson pair production process at hadron collider provides an opportunity for performing a study of the trilinear Higgs boson self-coupling. In this paper, we analyze the pair production of a neutral Higgs boson via both gluon-gluon and $b$-$\bar{b}$ fusions in the littlest Higgs (LH) model at the CERN LHC. We find that in some parameter space the relative corrections of the total cross section to the SM prediction may reach a value of 24% when $x ~ (=4 f v'/v^2)=0.95$ at the LHC. We conclude that if the parameter $x$ has a value above 0.8, the relative corrections contributed by the …
It is well known, that R-parity violating supersymmetric models predict a non-zero magnetic moment for neutrinos. In this work we study the Majorana neutrino transition magnetic moments within an RpV modified minimal supergravity model. Specifically, we discuss the contributions coming from the charged Higgs bosons, higgsinos, leptons, sleptons, charged gauge bosons, and charginos. We use the experimental results from the MUNU collaboration to restrict the model's parameter space. A comparison with two other types of contributions (only trilinear RpV couplings and trilinear plus neutrino--neut…
The simplest little Higgs model based on a SU(3) global symmetry contains a $SU(3)_{weak}$ triplet and a singlet per a generation in the lepton sector. A neutral component of the triplet and the singlet turn into a neutral vector-like $SU(2)_L$ singlet after electroweak symmetry breaking while the other neutral component of the triplet is the SM neutrino. At tree level, Yukawa couplings of the lepton sector not only allow the neutral vector-like lepton to couple to the SM neutrino, but also give them a Dirac mass. Majorana mass terms for the SM neutrinos and their partners arise at one loops, …
Constraints from flavour changing neutral currents are discussed in the context of predictive Grand Unified Supersymmetric Theories. Uncertainties in the estimation of their amplitudes are minimized by using a successful mass matrix ansatz which predicts the arbitrary parameters of the Standard Model. Furthermore, Renormalization Group Equations are used in order to express the sparticle masses involved, in terms of the gaugino mass $m_{1/2}$, the universal scalar mass $m_0$ and the trilinear coupling $A$ at the GUT scale. Modifications in the low energy expressions for the squark masses due t…
Flavour changing neutral current processes, being strongly suppressed in the Standard Model (SM), provide a unique window to new physics at scales much above the electroweak scale. Here, we summarize the recent progress in flavour physics studies of the Littlest Higgs model with T-parity, both in the quark and lepton sector. Particular emphasis is put on various correlations that could distinguish this model from other extensions of the SM.
Trilinear $Z$ boson interactions are sensitive probes both of new sources of $CP$ violation in physics Beyond the Standard Model and of new particle thresholds. Measurements of trilinear $Z$ interactions are typically interpreted in the frameworks of anomalous couplings and effective field theory, both of which require care in interpretation. To obtain a quantitative picture of the power of these measurements when interpreted in a TeV-scale context, we investigate the anatomy of $ZZZ$ interactions and consider two minimal and perturbative simplified models which induce such interactions throug…
We analyze neutral Higgs boson decays into squark pairs in the minimal supersymmetric extension of the Standard Model and improve previous analyses. In particular the treatment of potentially large higher-order corrections due to the soft SUSY breaking parameters A_b, the trilinear Higgs coupling to sbottoms, and mu, the Higgsino mass parameter, is investigated. The remaining theoretical uncertainties including the SUSY-QCD corrections are analyzed quantitatively.
We study two-body decays of a new neutral pseudoscalar into gauge bosons within the context of the Littlest Higgs model. Concretely, the $Φ^P \to WW, VV, gg$ processes induced at the one-loop level, with $V=γ, Z$, are considered. Since the branching ratios of the $Φ^P \to VV$ decays result very suppressed, only the $Φ^P \to WW, gg$ processes are thoroughly studied. The branching ratios for the $Φ^P \to gg$ and $Φ^P \to WW$ decays are of the order of $10^{-4}$ and $10^{-6}$, respectively, for $f$ around 2 TeV, which represents the global symmetry breaking scale of the theory. The production cro…
We investigate in detail the $γγ$ fusion production mechanisms of two neutral Higgs bosons ($h^0A^0$, $ H^0A^0$, $h^0H^0$ and $H^0H^0$) within the framework of the mSUGRA-inspired minimal supersymmetric standard model(MSSM) at an $e^+e^-$ linear colliders, which provide a probe of the trilinear Higgs self-couplings. We calculate the dependence of the production rates on Higgs boson masses, the ratio of the vacuum expectation values $\tan β$ and the CMS energy $\sqrt{s}$. We find that the cross section for the $H^0H^0$ production at LC can reach $0.2 fb$, while the cross section of $A^0H^0$ pro…
The possibility of testing trilinear neutral gauge boson couplings in radiative neutral current scattering at HERA is analyzed using a Monte Carlo program that includes the Standard Model at tree level and the anomalous vertices. Acceptance and isolation cuts are applied as well as optimized cuts to enhance the signal from new physics. The bounds on Zγγcouplings that can be achieved are not so stringent as present bounds, even for high luminosities, but probe a different kinematical region almost unsensitive to form factors.
We study the heavy neutral scalar decays into standard model electroweak gauge bosons in the context of the Littlest Higgs model. We focus our attention on the $Φ^0 \to WW, γV$ processes induced at the one-loop level, with $V=γ, Z$. Since the branching ratios of the $Φ^0 \to γV$ decays result very suppressed, only the $Φ^0 \to WW$ process is analyzed in the framework of possible experimental scenarios by using heavy scalar masses between 1.6 TeV until 3.3 TeV. The branching ratio for the $Φ^0 \to WW$ decay is of the order of $10^{-3}$ throughout the interval 2 TeV $< f <$ 4 TeV, which represen…
Higgs pair production provides a unique handle for measuring the strength of Higgs self interaction and constraining the shape of the Higgs potential. Including radiative corrections to the trilinear couplings of $CP$-even Higgs, we investigate the cross section of the lightest neutral Higgs pair production in gluon fusion at the Large Hadron Collider in the supersymmetric extensions of the standard model. Numerical results indicate that the correction to the cross section is about 11\% in the B-LSSM, while is only about 4\% in the MSSM. Considering the constraints of the experimental data of …
The Minimal Supersymmetric Standard Model with gauge mediated supersymmetry breaking and trilinear R-parity violation is applied to the description of neutrinoless double beta decay. A detailed study of limits on the parameter space coming from the B to (X,gamma) processes by using the recent CLEO results is performed. The importance of two-nucleon and pion-exchange realizations of neutrinoless double beta decay together with gluino and neutralino contributions to this process are addressed. We have deduced new limits on the trilinear R-parity breaking parameter lambda_{111}' from the non-obse…
Motived by the neutrino oscillation data, we consider the lightest tau sneutrino $\tilde ν_{τ_1}$ (which is mostly the right tau sneutrino) to be the lightest supersymmetric particle (LSP) in the framework of the minimal supersymmetric Standard Model. Both the standard and the non-standard trilinear scalar coupling terms are included for the right tau sneutrino interactions. The decay branching ratio of $\tilde ν_{τ_2} \to \tilde ν_{τ_1}+ h^0$ can become so large that the production rate of the lightest neutral Higgs boson ($h^0$) can be largely enhanced at electron or hadron colliders, either…
A generic feature of little Higgs models is presence of extra neutral gauge bosons. In the littlest Higgs model, the neutral extra gauge boson A_H is lightest among the extra particles and could be as light as a few hundred GeV, which may be produced directly at an e^+ e^- linear collider. We study production and decay of A_H at the linear collider and compare them with those of Z' bosons in supersymmetric E_6 models.
The CP violating asymmetry from the decay rates $H^\pm\to W^\pm h_1$ of charged Higgs bosons into the lightest neutral Higgs boson and a $W^\pm$ boson is calculated and discussed in the complex MSSM. The contributions from all complex phases are considered, especially from the top-squark trilinear coupling, which induces a large contribution to the CP asymmetry.
We propose a new dynamical relaxation mechanism of the little hierarchy problem, based on a singlet extension of the minimal supersymmetric standard model (MSSM). In this scenario, the small soft mass parameter of an MSSM singlet is responsible for the electroweak symmetry breaking and the non-zero Higgs vacuum expectation value, whereas the effect of the large soft mass parameter of the Higgs boson, -m_{h_u}^2 is dynamically compensated by a flat direction of the MSSM singlets. The small singlet's soft mass and the Z boson mass can be protected, even if the stop mass is heavier than 10 or 20 …
The reconstruction of the Higgs potential in the Standard Model or supersymmetric theories demands the measurement of the trilinear Higgs couplings. These couplings affect the multiple production of Higgs bosons at high energy colliders. We present a systematic overview of the cross sections for the production of pairs of (light) neutral Higgs bosons at the LHC. The analysis is carried out for the Standard Model and its minimal supersymmetric extension.
There is a recent proposal identifying the Higgs particle of the Standard Model as a pseudo Nambu-Goldstone boson. This new broken symmetry introduces new particles and new interactions. Among these new interactions a central role to get a new physics is played by two new heavy neutral gauge bosons. We have studied the two new neutral currents in the Littlest Higgs model and compared with other extended models. For high energy e+e- colliders we present a clear signature for these two new neutral gauge bosons that can indicate the theoretical origin of these particles. Previous analysis by othe…
We consider a supersymmetric Grand Unified Theory (GUT) based on the gauge group SO(10) suggested by Aulakh et al., which features two--step intermediate symmetry breaking, $SO(10) \to SU(4)_C \times SU(2)_L \times SU(2)_R \to SU(3)_C \times U(1)_{B-L} \times SU(2)_L \times SU(2)_R \to SU(3)_C \times SU(2)_L \times U(1)_Y$. {\bf $45, 54, 126+\overline{126}$} dimensional representations of Higgs superfields are employed to achieve this symmetry breaking chain. We also introduce a second, very heavy, pair of Higgs doublets, which modifies the Yukawa couplings of matter fields relative to minimal…
There is a recent proposal of identifying the Higgs particle of the Standard Model as a pseudo Nambu-Goldstone boson. This new broken symmetry introduces new particles and new interactions. Among these new interactions a central role to get a new physics is played by the new neutral gauge boson. We have studied the new neutral currents in the Littlest Higgs model and compared with other extended models. For high energy $e^+ + e^-$ colliders we present a clear signature for new neutral gauge bosons that can indicate the theoretical origin of these particles. Previous analysis by other authors w…
The phenomenology of the little-flavon model is discussed. Flavor changing neutral current and lepto-quark compositeness set the most stringent bounds to the lowest possible value for the scale at which the flavons arise as pseudo-Goldstone bosons.
The search for charged Higgs bosons, which are predicted in supersymmetric theories, is difficult at hadron colliders if the mass is large. In this paper we present the theoretical set-up for the production of charged Higgs boson pairs at the LHC in gluon-gluon collisions: $pp -> gg -> H^+ H^-$. When established experimentally, the trilinear couplings between charged and neutral CP-even Higgs bosons, $H^+ H^- h^0$ and $H^+ H^- H^0$, can be measured.
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