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تسجيل مستخدم جديدLocalized $4sigma$ and $5sigma$ Dijet Mass Excesses in ALEPH LEP2 Four-Jet Events
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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 $M_1+M_2sim 110mbox{ GeV}$; about half of the excess is concentrated in the region $M_1sim 80mbox{ GeV}$, $M_2sim 25mbox{ GeV}$, with a local significance between $4.7sigma$ and $5.5sigma$, depending on assumptions about hadronization uncertainties. The other half of the events are in a broad excess near $M_1sim M_2sim 55mbox{ GeV}$; these display a local significance of $4.1-4.5sigma$. We investigate the effects of changing the SM QCD Monte Carlo sample, the jet-clustering algorithm, and the jet rescaling method. We find that the excess is remarkably robust under these changes, and we find no source of systematic uncertainty that can explain the excess. No analogue of the excess is seen at LEP1.
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