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M. Raidal

Publications and source records attributed to M. Raidal.

49 records · Page 3Linked to original sources
arXiv1997

Spontaneous CP violation and the B system

We investigate effects of spontaneous breakdown of CP in $B^0_{d,s}-\overline{B^0}_{d,s}$ systems in left-right symmetric models. Assuming that the left-right contribution to the $B^0-\overline{B^0}$ matrix element $M_{12}$ can be at most equal to the standard model one we obtain a new lower bound, $M_H\gsim 12$ TeV, on the flavour changing Higgs boson mass. Most importantly, the convention independent parameter $Re(\overlineε_B),$ which measures the amount of $ΔB=2$ CP violation, can be enhanced by a factor of four or more for $B^0_d$ and almost by two orders of magnitude for $B^0_s$ systems when compared with the Standard Model predictions. Therefore, interesting possibilities to observe indirect CP violation in the $B$ system are open in the planned facilities.

hep-ph↗
arXiv1997

Testing the left-right symmetric model at linear collider

We review possible tests of the left-right electroweak model at future linear colliders, concentrating on signatures of the central predictions of the model, i.e. right-handed currents, massive neutrinos and triplet Higgs bosons. We analyse processes in e+e-, e-e- and e-γcollision modes. We present the mass reaches for the new particles at linear collider and sensitivities to their couplings.

hep-ph↗
arXiv1997

Doubly charged Higgs at LHC

We have investigated production of doubly charged Higgs particles $Δ_{L,R}^{++}$ via WW fusion process in proton-proton collisions at LHC energies in the framework of the left-right symmetric model. The production cross section of the right-triplet Higgs is for representative values of model parameters at femtobarn level. The discovery reach depends on the mass of the right-handed gauge boson W_R. At best $Δ_R^{++}$ mass up to 2.4 TeV are achievable within one year run. For $Δ^{++}_L$ the corresponding limit is 1.75 TeV which depends on the value of the left-triplet vev v_L. Comparison with Drell-Yan pair production processes shows that studies of the WW fusion processes extend the discovery reach of LHC roughly by a factor of two. The main experimental signal of a produced Higgs would be a hard same-sign lepton pair. There will be no substantial background due to the Standard Model (SM) interactions, since in the SM a same-sign lepton pair will always be associated with missing energy, i.e. neutrinos, due to lepton number conservation.

hep-ph↗
arXiv1996

Constraints on doubly charged Higgs interactions at linear collider

Production of a single doubly charged Higgs boson $Delta^{--}$ in polarized $e^+e^-$ and $e^+γ$ collision modes of the linear collider have been investigated. The mass range of $Delta^{--}$ to be probed extends up to the collision energy. The diagonal lepton number violating Yukawa coupling $h_{ee}$ will be tested at least three orders of magnitude more strictly than in present experiments.

hep-ph↗
arXiv1996

Constraints on the Wr mass and CP-violation in left-right models

We update the constraints on the right-handed $W_R$ gauge boson mass, mixing angle $ζ$ with the left-handed $W_L$ gauge boson, and other parameters in general left-right symmetric models with different mechanisms of CP violation. Constraints mostly independent of any assumption on the quark sector are obtained from a re-analysis of muon decay data. Estimates of the left-right hadronic matrix elements in the neutral kaon system and their uncertainties are revised using large $N_c$ and Chiral Perturbation Theory arguments. With explicitly given assumptions on the long-distance $(ΔS=1)^2$ contributions to the $K_L-K_S$ mass difference, lower bounds on $M_{W_R}$ are obtained. With the same assumptions, one also gets strong upper bounds from the CP-violating parameter $ε_K$, for most of the parameter space of left-right models where the right-handed third family does not contribute in CP-violating quantities.

hep-ph↗
arXiv1996

Non-decoupling and lepton number violation in left-right models

We argue that large non-decoupling effects of heavy neutrinos can appear naturally in manifestly left-right symmetric models due to the minimization conditions of the scalar potential and the structure of vev's imposed by phenomenology. We derive constraints on off-diagonal light-heavy and heavy-heavy neutrino mixings from the searches for lepton violating decays $μ\rightarrow eγ,$ $μ\rightarrow e e^-e^+$ and $μ-e$ conversion in nuclei. The most stringent limits come from the latter process because its amplitude shows a quadratic non-decoupling dependence on the heavy neutrino mass. Due to the suppression of right-handed currents by large $W_R$ mass the present experiments are not sensitive to the intergenerational mixings between heavy neutrinos if $M_{W_R}>200$ TeV.

hep-ph↗
arXiv1996

Spontaneous CP violation in the left-right model and the kaon system

A left-right model with spontaneous $CP$ breakdown, consistent with the particle physics phenomenology, is presented. Constraints on free parameters of the model: mass of the new right handed gauge boson $M_2$ and ratio $r$ of the two vacuum expectation values of the bidoublet, are found from the measurement of $ε$ in the kaon system. For most of the parameter space, $M_2$ is restricted to be below 10 TeV. Higher masses can be achieved only by fine tuning of Kobayashi-Maskawa matrix elements, quark masses, $r$ and the phase $α$ which is the unique source of $CP$-violation in the model. Large number of combinations of signs of quark masses, which are observables of the model, are found to be not allowed since they contradict with data. The range of $ε'/ε$ the model predicts is around $10^{-4}$ in magnitude.

hep-ph↗
arXiv1996

Single W-boson production in e-γcolliders

Single $W$-boson production in $e^-γ$ collisions with polarized beams is investigated. In the framework of the Standard Model the updated estimates for the measurement precision of photon anomalous coupling parameters $ κ_{ γ},$ $ λ_{ γ}$ at the Next Linear Collider with $ \sqrt{s_{ eγ}}=420$ GeV are obtained. The production of right-handed gauge bosons $ W^-_{ 2 }$ in this collision mode is also analysed. If the associated neutrino is light, the channel would give the best discovery reach for $ W^-_{ 2 }$ in the Next Linear Collider.

hep-ph↗
arXiv1995

The $W_R$ production in $eγ$ collisions

We consider the production of a single right-handed gauge boson $W_R$ in the high-energy $e^-γ$ collisions with polarized beams. If the associated neutrino is light, the reaction will give the best discovery reach for $W_R$ in the Next Linear Collider.

hep-ph↗
arXiv1994

Supersymmetric Left-Right Model and its Phenomenological Implications

We review here our study of a supersymmetric left-right model (SLRM). In the model the $R$-parity is spontaneously broken. Phenomenologically novel feature of the model is the occurrance of the doubly charged particles in the Higgs sector, which are possibly light enough to be seen in the next linear collider. Detection of the doubly charged higgsinos in the next linear collider is discussed.

hep-ph↗
arXiv1994

Slepton pair production in e+e- collision in supersymmetric left-right model

The pair production of sleptons in electron-positron collisions is investigated in a supersymmetric left-right model. The cross section is found considerably larger than in the minimal supersymmetric version of the Standard Model (MSSM) because of more contributing graphs. A novel process is a doubly charged higgsino exchange in u-channel, which makes the angular distribution of the final state particles and the final state asymmetries to differ from those of the MSSM. It also allows for the flavour non-diagonal final states $\tilde e\tildeμ$, $\tilde e\tildeτ$ and $\tilde μ\tildeτ$, forbidden in the MSSM. These processes also give indirect information about neutrino mixings since they depend on the same couplings as the Majorana mass terms of the right-handed neutrinos.

hep-ph↗
arXiv1993

Supersymmetric Left-Right Model and its Tests in Linear Colliders

We investigate phenomenological implications of a supersymmetric left-right model based on $SU(2)_L\times SU(2)_R\times U(1)_{B-L}\,$ gauge symmetry testable in the next generation linear colliders. We concentrate in particular on the doubly charged $SU(2)_R$ triplet higgsino $\tildeΔ$, which we find very suitable for experimental search. We estimate its production rate in $e^+e^-$, $e^-e^-$, $e^-γ$ and $γγ$ collisions and consider its subsequent decays. These processes have a clear discovery signature with a very low background from other processes.

hep-ph↗