Search for supersymmetry with taus using the razor variables

Link to cdsweb CDS PAS-SUS-11-029

Abstract

We present a search for pair-produced supersymmetric particles in √s = 7 TeV proton-proton collisions that decay to tau-enriched final states. The search is performed on 4.7 fb⁻¹ of data collected by the CMS experiment in 2011 at the CERN Large Hadron Collider. The signal candidates are isolated from the standard model background using the dimensionless razor variable R, related to the missing transverse energy E_T^miss. The new physics signal would be characterized by a broad peak in the distribution of M_R, an event-by-event indicator of the heavy particle mass scale. After background, modeled based on data, has been accounted for, no significant deviation is observed from the standard model expectation. The results are interpreted in tau-enriched simplified models of new physics.

Figures and tables

Figure 1

Figure 1: Definition of the fit region (green shaded area). The grid delimited by the gray vertical and horizontal represent the binning used to describe the signal distribution.

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Figure 2

Figure 2: Projection of the 2D fit result on MR (left) and R² (right) for the MU-TAU (top) and MU (bottom) boxes. Data are represented by the black points with error bars. The blue histogram is the total Standard Model prediction as obtained from a single pseudo-experiment based on the 2D fit. The red and yellow histograms represent a steep slope component denoted as V+jets 1st component and a component that encapsulates the steeper slope first component in t ̄t+jets and the effective second component which is indistinguishable for the different SM background processes. The fit is performed in the R² − MR fit region and projected into the full region. The green histogram is an example of signal distribution for the T3tauh simplified model with gluino mass set to 800 GeV/c² and LSP mass set to 200 GeV/c².

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Figure 3

Figure 3: Projection of the 2D fit result on MR (left) and R² (right) for the ELE-TAU (top) and ELE (bottom) boxes. The description of all the components in the figure is in the caption of Fig. 2.

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Table 1

Table1: The p-values corresponding to the observed numbers of events in the MU-TAU (left figure) and MU (right figure) box signal regions (SRi). The p-values test the compatibility of the observed number of events in data with the SM expectation. We quote the median and the mode of the yield distribution for each SR, together with the observed yield. A 68% probability interval is calculated using the probability associated with each yield outcome as the ordering principle.

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Table 2

Table 2: The p-values corresponding to the observed numbers of events in the ELE-TAU (left figure) and ELE (right figure) box signal regions (SRi). The p-values test the compatibility of the observed number of events in data with the SM expectation. We quote the median and the mode of the yield distribution for each SR, together with the observed yield. A 68% probability interval is calculated using the probability associated with each yield outcome as the ordering principle.

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Figure 4

Figure 4: Illustration of the simplified models considered to interpret the result: T5taunu (left) and T3tauh (right).

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Table 3

Table 3: Summary of the systematic uncertainties on the signal yield and shape.

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Figure 5

Figure 5: Exclusion cross-section vs. model spectrum for the T5taunu (left) and T3tauh (right) simplified models. The solid black (green) lines show the observed (expected) limits. The color scale shows the model independent cross-section excluded in the SMSs. The solid grey region indicates model points where the analysis was found to have dependence on initial state radiation modelling in the simulation of signal events above a pre-defined tolerance; no interpretation is presented for these model points.

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Figure 6

Figure 6: Event selection efficiency in the analysis signal region of the mLSP - mgluino plane for the Mu-Tau (top-left), Mu (top-right), Ele-Tau (bottom-left) and Ele (bottom-right) boxes for the T5taunu simplified model.

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Figure 7

Figure 7: Event selection efficiency in the analysis signal region of the mLSP - mgluino plane for the Mu-Tau (top-left), Mu (top-right), Ele-Tau (bottom-left) and Ele (bottom-right) boxes for the T3tauh simplified model.

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