Search for supersymmetry with photons in pp collisions at $\sqrt{s}$ = 8TeV

Abstract

Two searches for physics beyond the standard model in events containing photons are presented. The data sample used corresponds to an integrated luminosity of 19.7fb$^{-1}$ of proton-proton collisions at $\sqrt{s}$ = 8TeV, collected with the CMS experiment at the CERN LHC. The analyses pursue different inclusive search strategies. One analysis requires at least one photon, at least two jets, and a large amount of transverse momentum imbalance, while the other selects events with at least two photons and at least one jet, and uses the razor variables to search for signal events. The background expected from standard model processes is evaluated mainly from data. The results are interpreted in the context of general gauge-mediated supersymmetry, with the next-to-lightest supersymmetric particle either a bino- or wino-like neutralino, and within simplified model scenarios. Upper limits at 95% confidence level are obtained for cross sections as functions of the masses of the intermediate supersymmetric particles.

Link to paper draft

arXiv:1507.02898
CDS Record 1754939

Figures in the paper (click on the plot to get it in pdf format)

Figures Caption
Figure 1: Typical Feynman diagrams for the general gauge-mediation model with bino- (top left) and wino-like (top right) neutralino mixing scenarios. Here, the $\widetilde{\chi}^0_1$ can decay to $\tilde{G}g$ or $\tilde{G}Z$, with the branching fraction dependent on the $\widetilde{\chi}^0_1$ mass. The diagrams for the T5gg (bottom left) and T5wg (bottom right) simplified model spectra are also shown.
Figure 2: Tests of the background estimation method for the single-photon analysis using simulated events in bins of $E_{\mathrm{T}}^{\text{miss}}$. The direct simulation of $\gamma_\mathrm{tight}$ events is compared to the prediction of the multijet background from simulated $\gamma_\mathrm{loose}$ events (left). Simulated events with $\gamma_\mathrm{tight}$ originating from generated electrons are compared to the simulated prediction using the EW background method (right). The blue hatched area represents the total uncertainty and is the quadratic sum of the statistical (red vertical bars) and systematic (red hatched area) uncertainties. In the bottom panels, the ratio of the direct simulation to the prediction is shown.
  Figure 3: Distribution of $E_{\mathrm{T}}^{\text{miss}}$ from the single-photon search in comparison to the standard model background prediction. The expectation from an example GGMwino signal model point is also shown. In the bottom panels, the ratio of the data to the prediction is shown. The representations of uncertainties are defined as in Fig. 2
Figure 4: Distribution of M$_\mathrm{R}$ in the double-photon search for the background model, derived from a fit in the data control region, and for the T5gg (left) and GGMbino (right) signal models. The background model is normalized to the number of events in the signal region. The signal models are normalized to the expected signal yields.
Figure 5: Distribution of M$_\mathrm{R}$ in the double-photon search for a control sample of jets misreconstructed as photons (see text) in the control (left) and signal (right) regions. The data are compared to the 68\% range obtained from a fit in the control region and extrapolated to the signal region (blue bands). The open dots represent the center of the 68% range. The rightmost bin in each plot contains zero data entries.The bottom panel of each figure gives the z-scores (number of Gaussian standard deviations) comparing the filled dots to the band. The filled band shows the position of the 68\% window with respect to the expected value.
  Figure 6: Distribution of M$_\mathrm{R}$ in the double-photon search for a control sample of jets misreconstructed as photons to which a simulated sample of GGMbino events has been added. The squark and gluino masses are respectively set to $m_\tilde{q} = 1400$ GeV and $m_\tilde{g} = 1820$ GeV, and the production cross section is fixed to $\sigma = 2.7$ fb. The signal contribution is shown by the red histogram. The representations of the uncertainty bands, data points, and the information shown in the bottom panel are the same as in Fig. 5.
Figure 7: Distribution of M$_\mathrm{R}$ for the control (left) and signal (right) regions. The representations of the uncertainty bands, data points, and the information shown in the bottom panel are the same as in Fig. 5.
Figure 8: Single-photon analysis 95% C.L. observed upper limits on the signal cross section and exclusion contours in the gluino-squark (top) and gaugino-gluino (bottom) mass plane for the GGMbino (top left), GGMwino (top right), T5gg (bottom left), and T5wg (bottom right) models.The thick red dashed (black solid) line shows the expected (observed) limit. The thin dashed line and band show the 68% C.L. range about the expected limit. The solid line quantifies the impact of the theoretical uncertainty in the cross section on the observed limit. The color scale shows the excluded cross section for each set of mass values.
Figure 9: Double-photon analysis 95% C.L. observed cross section upper limits and excluded mass regions for the GGMbino (left) and T5gg (right) models. The representations of excluded regions and cross sections are the same as in Fig. 8.

Additional material

Figures Caption
Number of signal events in four different models after each selection step for the single photon analysis with statistical uncertainties.
Number of signal events in five different models after each selection step for the Razor analysis with statistical uncertainties.

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PDFpdf DiPhoton_Control_HighR.pdf r1 manage 15.4 K 2015-07-15 - 21:33 ToyokoOrimoto  
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