In a search for new phenomena in a signature suppressed in the standard model of elementary particles (SM), we compare the inclusive production of events containing a lepton (l), a photon (gamma), significant transverse momentum imbalance (missing E(t)), and a jet identified as containing a b-quark, to SM predictions. The search uses data produced in proton-antiproton collisions at s**(1/2) = 1.96 TeV corresponding to 1.9 fb-1 of integrated luminosity taken with the CDF detector at the Fermilab Tevatron. We find 28 ell gamma_b missing E(t) events versus an expectation of 31.0+4.1_-3.5 events. If we further require events to contain at least three jets and large total transverse energy, simulations predict that the largest SM source is top-quark pair production with an additional radiated photon, tt-bar + gamma. In the data we observe 16 tt-bar gamma candidate events versus an expectation from non-top-quark SM sources of 11.2+2.3_-2.1. Assuming the difference between the observed number and the predicted non-top-quark total is due to SM top quark production, we estimate the tt-bar gamma cross section to be 0.15 +/- 0.08 pb.
Searching the Inclusive ell_gamma Missing E(t) + b-quark Signature for Radiative Top Quark Decay and Non-Standard-Model Processes
CASTRO, ANDREA;DENINNO, MARIA MADDALENA;MOGGI, NICCOLO';RIMONDI, FRANCO;ZUCCHELLI, STEFANO
2009
Abstract
In a search for new phenomena in a signature suppressed in the standard model of elementary particles (SM), we compare the inclusive production of events containing a lepton (l), a photon (gamma), significant transverse momentum imbalance (missing E(t)), and a jet identified as containing a b-quark, to SM predictions. The search uses data produced in proton-antiproton collisions at s**(1/2) = 1.96 TeV corresponding to 1.9 fb-1 of integrated luminosity taken with the CDF detector at the Fermilab Tevatron. We find 28 ell gamma_b missing E(t) events versus an expectation of 31.0+4.1_-3.5 events. If we further require events to contain at least three jets and large total transverse energy, simulations predict that the largest SM source is top-quark pair production with an additional radiated photon, tt-bar + gamma. In the data we observe 16 tt-bar gamma candidate events versus an expectation from non-top-quark SM sources of 11.2+2.3_-2.1. Assuming the difference between the observed number and the predicted non-top-quark total is due to SM top quark production, we estimate the tt-bar gamma cross section to be 0.15 +/- 0.08 pb.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.