Search for New Physics in Di-Electron Events

Search for New Physics in Di-Electron Events

A search for a narrow resonance in di-electron events in the invariant mass range of 150-950 GeV/c^2 is reported, using approximately 1.3 fb^{-1} of p-pbar collision data collected by the CDF II detector at the Fermilab Tevatron at sqrt{s} = 1.96 TeV. The search uses a frequentist p-value method to scan the mass spectrum for significant excesses over the Standard Model. Separately to the search, direct limits on cross section x branching ratio are placed on the Randall-Sundrum graviton and Z' bosons as a function of mass. The E6 Z' bosons; the Z'_I, Z'_PSI, Z'_CHI and Z'_ETA bosons are excluded with masses below 729, 822, 822, and 891 GeV/c^2 respectively. A Randall-Sundrum graviton with k/Mpl = 0.1 is excluded for M_{G} < 807 GeV/c^2. These results are combined with the di-photon channel to improve the exclusion region for the Randall-Sundrum graviton to M_{G} < 889 GeV/c^2 for k/Mpl = 0.1. These limits are the most exclusive limits at the current time.

Contacts: Joel Goldstein, Sam Harper and Peter Renton (University of Oxford)
Data: Run II, 1288 pb^-1
Documentation: PS, PDF

Plots and Tables:

Mass Spectrum Plots :
	Di-Electron mass spectrum (5 GeV binning): central-central: GIF, EPS central-plug: GIF, EPS central-central + central-plug: GIF, EPS
	Di-Electron mass spectrum (larger bins, otherwise the same): central-central: GIF, EPS central-plug: GIF, EPS central-central + central-plug: GIF, EPS
Signal Search:
	P-value Plot : GIF, EPS This plot looks for an excess of the Standard Model predictions, with a lower p-value indicating a larger excess. No excess larger than that expected from background flucations alone is observed.
Limits :
	spin-1 (Z'): GIF, EPS spin-2 (RS Graviton) : GIF, EPS
Combined limits with the di-photon channel :
	cross-section limits GIF, EPS
	k/Mpl vs mass limits GIF, EPS

Mass Limits Z':

Z' Model	Z'_{SM}	Z'_{ETA}	Z'_{CHI}	Z'_{PSI}	Z'_{IOTA}
Mass Limit (GeV/c^2)	923	891	822	822	729

Mass Limits RS Graviton (GeV/c^2):

k/Mpl	0.01	0.025	0.05	0.07	0.10
e+e-	302	469	674	741	807
gamma gamma	230	500	694	782	850
e+e- + gamma gamma	267	580	761	820	889

Other Studies:
A separate analysis has determined the significance of the largest excess in a smaller dielectron data sample with different event selection criteria.

last updated Febuary 15th, 2007 by Sam Harper.
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