Searcharxiv⌕ Search

arXiv subjects

J. Maalampi

Publications and source records attributed to J. Maalampi.

35 records · Page 2Linked to original sources
arXiv1998

Production of qqQQ final states in ee collisions in the left-right symmetric model

We consider the reaction ee ->qqQQ as a test of lepton number non-conservation in the framework of the left-right-symmetric electroweak model. The main contributions to this process are due to Majorana neutrino exchange in t-channel and doubly charged Higgs (Delta{--}) exchange in s-channel with a pair of right-handed weak bosons (WR) as intermediate state. We show that in a linear ee collider with the collision energy of 1 TeV (1.5 TeV) the cross section of this process is 0.01 fb (1 fb), and it will, for the anticipated luminosity of 10**{35} cm**{-2}, be detectable below the WR threshold. We study the sensitivity of the reaction on the masses of the heavy neutrino, WR and Delta{--}.

hep-ph↗
arXiv1997

New constraints on R-parity violation from μ-e conversion in nuclei

We derive new constraints on the products of explicitly R-parity violating couplings $λ$ and $λ'$ in MSSM from searches for μ-e conversion in nuclei. We concentrate on the loop induced photonic coherent conversion mode. For the combinations $|λλ|$ which in μ-e conversion can be probed only at loop level our constraints are in many cases more stringent than the previous ones due to the enhancement of the process by large $\ln(m^2_f/m^2_{\tilde f}).$ For the combinations of $|λ'λ'|$ the tree-level μ-e conversion constraints are usually more restrictive than the loop ones except for two cases which involve the third generation. With the expected improvements in the experimental sensitivity, the μ-e conversion will become the most stringent test for all the involved combinations of couplings.

hep-ph↗
arXiv1997

Phenomenology of SUSY-models with spontaneously broken R-parity

We review the consequences of spontaneously broken R-parity in present and planned lepton-lepton colliders. In the left-right models the R-parity, $R=(-1)^{3(B-L)+2S}$, is preserved due to the gauge symmetry, but it must be spontaneously broken in order to the scalar spectrum to be physically consistent. The spontaneous breaking is generated via a non-vanishing VEV of at least one of the sneutrinos, which necessarily means non-conservation of lepton number $L$. The R-parity violating couplings are parametrized in terms of mixing angles, whose values depend on model parameters. Combined with the constraints derived from low-energy measurements this yields allowed ranges for various R-parity breaking couplings. The R-parity breaking allows for the processes in which a single chargino or neutralino is produced, subsequently decaying at the interaction point to non-supersymmetric particles.

hep-ph↗
arXiv1997

Signals of spontaneous R parity breaking at LEP and at a linear collider

We study the production of neutralinos and charginos at LEP and at a linear collider in the case of spontaneously broken R-parity. We first investigate the constraints on the single neutralino and chargino production from the LEP 1 experiments, and then we consider the production at LEP 2 and at a linear collider. We concentrate on the supersymmetric $SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ model, where the spontaneous R-parity breaking is inevitable and is associated with the breaking of the LR-symmetry.

hep-ph↗
arXiv1997

Heavy neutrino mixing and single production at Linear Collider

We study the single production of heavy neutrinos via the processes $e^-e^+ \to νN$ and $e^-γ\to W^- N$ at future linear colliders. As a base of our considerations we take a wide class of models, both with vanishing and non-vanishing left-handed Majorana neutrino mass matrix $m_L$. We perform a model independent analyses of the existing experimental data and find connections between the characteristic of heavy neutrinos (masses, mixings, CP eigenvalues) and the $m_L$ parameters. We show that with the present experimental constraints heavy neutrino masses almost up to the collision energy can be tested in the future experiments.

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

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↗
arXiv1995

WW$γ$ and WWZ Production in $e^-e^-$ Collisions in the Left-Right Model

We have investigated the three vector boson production in electron-electron collisions in the framework of the left-right symmetric electroweak model. The process occurs due to lepton number violating interactions mediated by Majorana neutrinos and triplet Higgs scalars. We find that only the reactions with a heavy gauge boson pair in the final state, $e^-e^-\to W^{-}_2 W^{-}_2γ$ and $e^-e^- \to W^{-}_2 W^{-}_2Z^0_1$, are phenomenologically interesting from the point of view of the Next Linear Collider. If the mass of $W_2^-$ is 0.5 TeV and the mass of the heavy Majorana neutrino of the order of 1 TeV, the cross section of both reactions is in the range 1 to 10 fb at $\sqrt{s}= 2$ TeV, depending on the mass of the doubly charged triplet Higgs $δ^{--}$, yielding a 1 % background for the pair production of $W_2^-$. At the $δ^{--}$ resonance the cross section can be as large as 1 pb.

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

Phenomenological Determination of the Beauty Meson Decay Parameter $f_B$ and the CP-Violating Angle $δ$

We fit the ${\cal CKM}$-matrix to all recent data with the following free parameters: three mixing angles, the CP-violating angle $δ$ in the Maiani parametrisation, the top quark mass $m_t$, and the product $f_B{\cal B}_{\B}^{1/2}$, where $f_B$ is the $B$-meson decay parameter and ${\cal B}_{\B}$ is the bag parameter. Our fits span a contiguous region in the $(f_B{\cal B}_{\B}^{1/2},\ \cosδ)$--plane, limited by $0.117\lsim f_B{\cal B}_{\B}^{1/2}/{\rm GeV}\lsim 0.231$ and --0.95 $\lsim$ $\cosδ$ $\lsim$ 0.70. The parameters $f_B{\cal B}_{\B}^{1/2}$ and $\cosδ$ are strongly positively correlated.

hep-ph↗
arXiv1994

Baryon and lepton number transport in electroweak phase transition

We consider the baryon number generation by charge transport mechanism in the electroweak phase transition taking properly into account thermal fluxes through the wall separating true and false vacuum in the spatial space. We show that the diffusion from the true vacuum to the false one has a large diminishing effect on the baryon number unless the wall velocity is near to, but less than, the speed of sound in the medium and the ratio between the collision rate and wall thickness is about 0.3. The maximum net baryon density generated is $ρ_B/s\simeq 0.2\times 10^{-10}$, where $s$ is the entropy density of the Universe. If the wall proceeds as a detonation, no baryon number is produced.

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↗