Production of heavy Majorana neutrino $N_{e}$ predicted by left-right symmetric extension of the Standard Model at future { ormalsize TeV} scale $ep$ colliders have been considered. In order to estimate potential of $ep$ colliders for $N_{e}$ search we consider back-groundless process $e^{-}prightarrow e^{+}X$ which is consequence of Majorana nature of $N_{e}$. It is shown that { ormalsize linac-LHC} and { ormalsize linac-FCC} based $ep$ colliders will cover much wider regions of $N_{e}$ and $W_{R}$ masses than corresponding linear electron-positron colliders.
The status of two on-going studies concerning important aspects of the phenomenology of gauge-mediated supersymmetry breaking (GMSB) models at TeV colliders is reported. The first study deals with the characteristics of the light Higgs boson spectrum allowed by the (minimal and non-minimal) GMSB framework. Todays most accurate GMSB model generation and two-loop Feynman-diagrammatic calculation of m_h have been combined. The Higgs masses are shown in dependence of various model parameters at the messenger and electroweak scales. In the minimal model, an upper limit on m_h of about 124 GeV is found for m_t = 175 GeV. The second study is focused on the measurement of the fundamental SUSY breaking scale sqrt(F) at the LHC in the GMSB scenario where a stau is the next-to-lightest SUSY particle (NLSP) and decays into a gravitino with c*tau_NLSP in the range 0.5 m to 1 km. This implies the measurement of mass and lifetime of long lived sleptons. The identification is performed by determining the time of flight in the ATLAS muon chambers. Accessible range and precision on sqrt(F) achievable with a counting method are assessed.
High-energy lepton colliders with a centre-of-mass energy in the multi-TeV range are currently considered among the most challenging and far-reaching future accelerator projects. Studies performed so far have mostly focused on the reach for new phenomena in lepton-antilepton annihilation channels. In this work we observe that starting from collider energies of a few TeV, electroweak (EW) vector boson fusion/scattering (VBF) at lepton colliders becomes the dominant production mode for all Standard Model processes relevant to studying the EW sector. In many cases we find that this also holds for new physics. We quantify the size and the growth of VBF cross sections with collider energy for a number of SM and new physics processes. By considering luminosity scenarios achievable at a muon collider, we conclude that such a machine would effectively be a high-luminosity weak boson collider, and subsequently offer a wide range of opportunities to precisely measure EW and Higgs coupling as well as to discover new particles.
We explore the signatures of the $tilde{R}_2$ class of leptoquark (LQ) models at the proposed $e^- p$ and $e^+p$ colliders. We carry out an analysis for the proposed colliders LHeC and FCC-eh with center of mass (c.m.) energy 1.3 TeV and 3.46 TeV, respectively. For $tilde{R}_2$ class of LQ models, there are a number of final states that can arise from LQ production and its subsequent decay. In this report we do a detailed cut-based analysis for the $l^{pm}j$ final state. We also discuss the effect of polarized electron and positron beams on LQ production and in turn on $l^{pm}j$ production. At LHeC, the final state $l^+j$ has very good discovery prospect. We find that, only 100 $text{fb}^{-1}$ of data can probe LQ mass upto 1.2 TeV with $5sigma$ significance, even with a generic set of cuts. On the contrary, at FCC-eh, one can probe LQ masses upto 2.2 TeV (for $e^-$ beam) and 3 TeV (for $e^+$ beam), at more than $5sigma$ significance with luminosity $1000,text{fb}^{-1}$ and $500,text{fb}^{-1}$, respectively.
In multiscale and topcolor-assisted models of walking technicolor, relatively light spin-one technihadrons $rho_T$ and $omega_T$ exist and are expected to decay as $rho_T to W pi_T, Z pi_T$ and $omega_T to gamma pi_T$. For $M_{rho_T} simeq 200 GeV$ and $M_{pi_T} simeq 100 GeV$, these processes have cross sections in the picobarn range in $bar p p$ colisions at the Tevatron and about 10 times larger at the Large Hadron Collider. We demonstrate their detectability with simulations appropriate to Run II conditions at the Tevatron.
We investigate the nature (Dirac vs. Majorana) and size of left-handed neutrino masses in a supersymmetric five-dimensional model compactified in the interval [0,pi R], where quarks and leptons are localized on the boundaries while the gauge and Higgs sectors propagate in the bulk of the fifth dimension. Supersymmetry is broken by Scherk-Schwarz boundary conditions and electroweak breaking proceeds through radiative corrections. Right-handed neutrinos propagate in the bulk and have a general five-dimensional mass M, which localizes the zero modes towards one of the boundaries, and arbitrary boundary terms. We have found that for generic boundary terms left-handed neutrinos have Majorana masses. However for specific boundary configurations left-handed neutrinos are Dirac fermions as the theory possesses a conserved global U(1) symmetry which prevents violation of lepton number. The size of neutrino masses depends on the localization of the zero-modes of right-handed neutrinos and/or the size of the five-dimensional neutrino Yukawa couplings. Left-handed neutrinos in the sub-eV range require either MR~10 or Yukawa couplings ~10^{-3}R, which make the five-dimensional theory perturbative up to its natural cutoff.