Global search for new physics with $2.0{\mathrm{fb}}^{-1}$ at CDF

Data collected in run II of the Fermilab Tevatron are searched for indications of new electroweak-scale physics. Rather than focusing on particular new physics scenarios, CDF data are analyzed for discrepancies with the standard model prediction. A model-independent approach (Vista) considers gross features of the data, and is sensitive to new large cross-section physics. Further sensitivity to new physics is provided by two additional algorithms: a Bump Hunter searches invariant mass distributions for “bumps” that could indicate resonant production of new particles, and the Sleuth procedure scans for data excesses at large summed transverse momentum. This combined global search for new physics in $2.0{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ reveals no indication of physics beyond the standard model.

Figure 1

Distribution of observed discrepancy between data and the SM prediction for populations of final states, measured in units of standard deviation ($\sigma$). The black line represents the theoretical expectation assuming no new physics.

Figure 2

Distribution of observed discrepancy between data and the SM prediction for shapes of kinematic distributions, measured in units of standard deviation ($\sigma$). The black line represents the theoretical expectation assuming no new physics.

Figure 3

One of the significant shape discrepancies seen by Vista, $\Delta R=\sqrt{\Delta {\varphi }^2+\Delta {\eta }^2}$, between the second and third highest $p_T$ jets in the Vista 3-jet final state. Data are shown as filled (black) circles, with the standard model prediction shown as the shaded (red) histogram.

Figure 4

Significance of the most interesting bump in each mass variable ($P_a$, in units of standard deviations) considered by the Bump Hunter. The black line represents the theoretical expectation assuming no new physics.

Figure 5

Distribution of the invariant mass of all four jets in the $4j\sum _{}^{}{p}_T<400\mathrm{GeV}$ final state. This variable contains the most significant bump found by the Bump Hunter, indicated by the dashed (blue) lines.

Figure 6

The distribution of $\mathcal{P}$ in the data, with one entry for each final state considered by Sleuth. The black line represents the theoretical expectation assuming no new physics.

Figure 7

The $\sum _{}^{}{p}_T$ distributions of the four most interesting final states found by Sleuth. Data are shown as filled (black) circles, with the expected contribution from standard model processes shown as the shaded (red) histograms and identified in the legend. The category “Other” represents the sum of all remaining relevant SM processes, each of which individually is smaller than the smallest itemized contribution. The label in the top left corner of each plot lists the objects in the final state, where $l^{\pm }$ is a lepton ($e$ or $\mu$), $l^{\prime }$ is an additional lepton of different flavor, $j$ denotes a jet, and ${\mathrm{p̸}}_T$ represents missing transverse momentum. Global charge conjugation is implied, so that a final state labeled $l^{+}{l}^{\prime +}$ also includes $l^{-}{l}^{\prime -}$. The region with the most significant excess of data over the SM expectation is indicated by the arrow below the $x$ axis, and displayed in the inset with the number of events expected (SM) and observed (d). The significance of the excess is shown by the value of $\mathcal{P}$ in the top right corner.