High Mass Sneutrino Search in the RPV Electron-Muon Channel

We search for high mass resonances decaying an oppositely charged electron/muon final state in 344 pb^-1 of Run II data. We interpret our results in terms of the R-Parity violating production and decay of the tau sneutrino. Data is found to be consistent with our Standard Model predictions and we constrain the tau sneutrino mass as a function of the relevant RPV SUSY couplings. A detailed description of the analysis is provided in CDF 7616. Please contact me with any questions.

Blessed Plots and Tables

(click on the graphics below for higher resolution images)

1. Feynman Diagram for RPV Sneutrino Production and Decay.

Shown near the vertices are the RPV lambda parameters in the SUSY Lagrangian that govern the production of the sneutrino from ddbar and its decay to e/mu.


2. Simulated Signal Acceptance and Resonance Width.

The fit to the acceptance curve ( on the left ) is used to obtain values used in the cross section calculation for a number of mass points between 50 and 800 GeV/c^2. The distance between mass points and the size of the acceptance window applied for each are determined using the fit to the width of the reconstructed MC mass distribution ( right ).


3. Expected Backgrounds.

This table shows the expected contribution for Standard Model processes across the 50-800 GeV/c^2 mass range. The uncertainties shown are statistical only but will be updated soon to included systematics.

4. e/mu Control Region.

Before unblinding we compared data to MC predictions for a mass range already excluded by the Run I analysis. The slight shift observed for data and MC in this region does not represent an inconsistency as it is contained by our acceptance window.


5. Data vs. MC

This plot compares the data to MC predictions over the full mass range.

6. Data vs. MC w/ Sneutrino Hypothesis

This is similar to the previous plot but includes the expected contribution to the SM background of a 200 GeV/c^2 sneutrino. The shape of the peak is derived from our Pythia simulation and its scale is set by the NLO cross-section and signal acceptance at 200 GeV/c^2.


7. Sensitivity, Observed and Theoretical Cross Section.

The dark blue line indicates the average (over a large number of pseudo-experiments) 95% CL cross section we would expect to measure assuming contributions from SM processes only. The yellow and cyan bands bordering this curve indicate 1 and 2 sigma fluctuations from the average. Our observation is shown in black while the NLO theoretical prediction (for specific values of the RPV couplings) is overlaid in red. The intersection of the red and black curves indicates that we can exclude sneutrino masses below ~460 GeV/c^2 for this particular choice of values for the RPV couplings.

8. Data and MC Chi-Squared Consistency Table.

We performed a chi-squared test for data and MC in order to address the potential observation of a broadly distributed excess in the region in which we are sensitive to new physics. Before unblinding we choose variable width mass bins to ensure occupancies sufficient for the test (5 MC events per bin). The total reduced chi-square statistic results in a p-value of 23%, indicating that our results are consistent with the Standard Model.


9. Exclusion Regions.

These plots show excluded values for the RPV SUSY couplings that govern the production and decay of the tau sneutrino. An individual point in the plot represents the mass limit for a choice of RPV couplings (see plot 7). The exclusion curves for each coupling are drawn for several values of the alternate coupling. Both plots contain the same information but appear different due to a difference in scale.


10. Event Displays for the Highest Mass Event

These graphics depicts the tracks, muon stubs and calorimeter depositions for our highest mass event.

Last Updated : 06.27.05