Search for excited electrons through γγ\gamma\gamma scattering

We study the potential of $\gamma \gamma$ option of future high energy linear $e^{+}e^{-}$ colliders to search for excited electrons with spin-1/2. We calculate single production cross sections, give the angular distributions and $f-m^*$ contour plots for $\sqrt{s}=0.5$ TeV and $\sqrt{s}=3$ TeV both using the standard (tree level) couplings and anomal couplings.Comment: 10 pages, 6 figures, accepted for publication in PR

Excited muon searches at the FCC based muon-hadron colliders

We study the excited muon production at the FCC based muon-hadron colliders. We give the excited muon decay widths and production cross section. We deal with the $\mu p\rightarrow\mu^{\star}q\rightarrow\mu\gamma q$ process and we plot the transverse momentum, rapidity and invariant mass distributions of final state particles to get the discovery cuts. By using discovery cuts, we get the mass limits for excited muons. It is shown that the discovery limits on the mass of $\mu^{\star}$ are 2.2 TeV, 5.9 TeV and 7.5 TeV for $\mu63$-FCC, $\mu750$-FCC and $\mu1500$-FCC, respectively.Comment: 13 pages, 10 figures, 3 tables, version of published in Adv. High Energy Physic

Search for excited spin-3/2 neutrinos at LHeC

We study the potential of the next $ep$ collider, namely LHeC, with two options $\sqrt{s}=1.3$ TeV $\sqrt{s}=1.98$ TeV, to search for excited spin-1/2 and spin-3/2 neutrinos. We calculate the single production cross section of excited spin-1/2 and spin-3/2 neutrinos according to their effective currents describing their interactions between gauge bosons and SM leptons. We choose the $\nu^{\star}\rightarrow eW$ decay mode of excited neutrinos and $W\rightarrow jj$ decay mode of $W$-boson for the analysis. We put some kinematical cuts for the final state detectable particles and plot the invariant mass distributions for signal and the corresponding backgrounds. In order to obtain accessible limits for excited neutrino couplings, we show the $f-f^{\prime}$ and $c_{iV}-c_{iA}$ contour plots for excited spin-1/2 and excited spin-3/2 neutrinos, respectively.Comment: 15 pages, 8 figures, 5 Table

Constraints on Unparticles from Low Energy Neutrino-Electron Scattering

We place limits on scalar and vector unparticle couplings to electrons and neutrinos using data from reactor neutrino experiments originally designed to search for neutrino magnetic moment. Upper bounds on Standard Model lepton-scalar unparticle and lepton-vector unparticle couplings $\lambda_0$, and $\lambda_1$ are given for various values of the unparticle mass dimension d, and the unparticle energy scale $\Lambda_{\cal U}$. Especially for smaller values of the mass dimension d (1 <d <1.3) these bounds are very significant and comparable to those obtained from production rates at high energy colliders. These bounds are also similar to those obtained by the analysis of the absence of the decay of the low-energy solar and reactor neutrinos.Comment: 6 pages of LATEX, 3 figure

Unparticle Searches Through Low Energy Parity Violating Asymmetry

In this paper, we study the effects of the unparticles on the parity-violating asymmetry for the low energy electron-electron scattering, $e^-e^-\to e^-e^-$. Using the data from the E158 experiment at SLAC we extract the limits on the unparticle coupling $\lambda_{AV}$, and on the the energy scale $\Lambda$ at 95% C.L. for various values of the scaling dimension $d$

Single production of excited spin-3/2 neutrinos at linear colliders

We study the potential of future high energy e+e- colliders to probe excited neutrino signals in different channels coming from the single production process via gauge interactions. We calculate the production cross section, decay widths and branching ratios of excited spin-3/2 neutrinos according to their effective currents and we compare them with that of the spin-1/2 ones. The signals and corresponding backgrounds are examined in detail to get accessible limits on the masses and couplings of excited spin-3/2 neutrinos.Comment: 21 pages, 13 figures, 8 table

Search for excited spin-3/2 and spin-1/2 leptons at linear colliders

We study the single production of excited spin-3/2 and spin-1/2 leptons in future high energy $e^+e^-$ collisions. We calculate the production cross section and decay widths of excited spin-3/2 and spin-1/2 leptons according to their effective currents. We show that these possible new excited states can be probed up to the mass $m^*$ ~ $\sqrt{s}$ depending on their couplings to leptons and gauge bosons. We present the angular distributions of final state particles as a measure to discriminate between an excited spin-3/2 and spin-1/2 lepton signal. The signals and the corresponding backgrounds are studied in detail to obtain attainable limits on masses and couplings of excited leptons at future linear collidersComment: 20 pages, 8 figures, 5 table

Single Production of Vectorlike Y Quarks at the HL-LHC

We study single production of exotic vectorlike $Y$ quark with electric charge $|Q_{Y}|=4/3$ and its subsequent decay at the High Luminosity LHC (HL-LHC). Most of the vector like quark (VLQ) decays have the electroweak $W$ bosons in the intermediate state. Besides their direct productions singly or pairs, the $W$-bosons are involved in decay chains as a result of the decay of a top quark which contributes to the background. This is particularly the case since vectorlike $Y$ quark, which is estimated to be produced with a high cross-section, can only decay via a $W$ boson and a down type quark ($d,s,b$). We calculate the cross sections of signal (for different couplings and mass values) and relevant Standard Model (SM) backgrounds. After a fast simulation of signal and background events, estimations of the sensitivity to the parameters (mass range 1000-2500 GeV for coupling value $\kappa_{Y}=0.5$, and mass range 500-2000 GeV for coupling values $\kappa_{Y}=0.3$ and $\kappa_{Y}=0.15$) have been presented at the HL-LHC with center of mass energy $\sqrt{s}=14$ TeV and integrated luminosity projections of 300 fb$^{-1}$, 1000 fb$^{-1}$ and 3000 fb$^{-1}$.Comment: 14 pages, 21 figure

Realistic constraints on the doubly charged bilepton couplings from Bhabha scattering with LEP data

Upper limits on doubly charged bilepton couplings and masses are extracted from LEP data for Bhabha scattering at energy range $\sqrt{s}=183-202$ GeV using standard model program ZFITTER which calculates radiative corrections. We find that $g_{L}^{2}/M_{L}^{2}<O(10^{-5})GeV^{-2}$ at 95% C.L. for scalar and vector bileptons.Comment: 5 pages, 1 EPS figur