Anomalous 4-Jet Events at LEP: a Signal of Low Scale Technicolour?

ALEPH has reported a significant excess of four-jet events in the LEP runs above the Z^0 resonance, which however has not been confirmed by the other LEP collaborations. We assume here that this excess corresponds to a physics signal and try to interpret it in the context of supersymmetric models with R-parity violation. Associated production of a left and right selectron can explain all the distinctive features of the ALEPH data: the value of the cross section, the di-jet ma...

We investigate an excess observed in hadronic events in the archived LEP2 ALEPH data. This excess was observed at preselection level during data-MC comparisons of four-jet events when no search was being performed. The events are clustered into four jets and paired such that the mass difference between the two dijet systems is minimized. The excess occurs in the region $M_1+M_2\sim 110\mbox{ GeV}$; about half of the excess is concentrated in the region $M_1\sim 80\mbox{ GeV}$...

Scalar particles that couple to two up quarks may be produced at the LHC even if they are ultraheavy, in the $8-10$ TeV mass range. A renormalizable theory that includes a diquark particle of this type ($S_{uu}$), two vectorlike quarks ($\chi_1, \chi_2$), and a gauge-singlet pseudoscalar, predicts LHC signals involving four or more jets of very high $p_T$. Two remarkable events observed by the CMS experiment, each involving four high $p_T$-jets, may be due to an $S_{uu}$ of m...

Pair-production of heavy top quarks at the Tevatron Collider is significantly enhanced by the color--octet technipion, $\eta_T$, occurring in multiscale models of walking technicolor. We discuss $\bar tt$ rates for $m_t = 170$ GeV and $M_{\eta_T} = 400-500$ GeV. Multiscale models also have color--octet technirho states in the mass range 200-600 GeV that appear as resonances in dijet production and technipion pair--production.

We investigate the possibility that the excess of four-jet events in $e^+e^-$ collisions at LEP-1.5 which has been reported by the ALEPH Collaboration could be due to the production of charginos or neutralinos, followed by their decay into quark jets through baryon number-violating ($\lambda^{\prime\prime}$) couplings. An estimate at the parton level shows, however, that these events cannot be due to neutralinos because of the low cross-section, and is unlikely to be due to t...

I discuss high mass signatures of technicolor that would be observable at a very high energy muon collider. Most intriguing is the spectrum of spin-one technihadrons, rho_T, omega_T and A_{1T}, which may extend to 100 TeV and beyond in a walking technicolor theory.

We discuss how to search for a possibe signal of the recently observed 750 GeV enhancement in the diphoton channel in the four-jet production. In the present studies we assume that the produced state is pseudoscalar. This fact, when combined with specificity of the corresponding amplitude, allows to improve the signal-to-background (S/B) ratio. We discuss in detail how to impose cuts on jets in rapidity and transverse momenta in order to find optimal S/B ratio and not to loos...

We interpret the dijet enhancement reported by the ALEPH collaboration in the process $e^+e^- \rightarrow $ 4 jets as being due to the production of a pair of bottom squarks, followed by their R-parity violating decays into pairs of light quarks. Constraints on this speculative interpretation are examined. Some of the consequences of our hypothesis are drawn within the context of softly broken supersymmetry.

We study the theory and some experimental hints of ultraheavy resonances at the LHC. The production of an ultraheavy narrow particle may have a larger rate than the QCD background even when the final state includes only hadronic jets. We consider two classes of models that lead to 4-jet signals. In the first class a diquark scalar decays into two vectorlike quarks. In the second one a coloron decays into two color-octet scalars or into a pair of vectorlike quarks. We show tha...

We review briefly the indications for some relatively light superpartners based on the ~$R_b$ ~anomaly and discuss the dependence of the potential increase in $R_b$ on the assumption about ~$R-$parity (non)conservation. We point out that the exotic 4-jet events reported by ALEPH may constitute a signal for supersymmetry with such a light spectrum and with explicitly broken $R-$parity. A parton level simulation shows that production of a pair of light charginos with their subs...