Search for new physics with monotop final states in pp collisions at = 8 TeV

Link to the document in CDS

Abstract:

Results are presented from a search for new decaying massive particles whose presence is inferred from an imbalance in transverse momentum and which are produced in association with a single top quark that decays into a bottom quark and two light quarks. The measurement is performed using 19.7 inverse femtobarns of data from proton-proton collisions at a center-of-mass energy of 8 TeV, collected with the CMS detector at the CERN LHC. No deviations from the standard model predictions are observed and lower limits are set on the masses of new invisible bosons. In particular, scalar and vector particles, with masses below 330 and 650 GeV, respectively, are excluded at 95% confidence level, thus substantially extending a previous limit published by the CDF Collaboration.

Approved plots

Figure (click on the picture to get the eps file) Caption .pdf
click on it to get it Figure 1 (a): The invariant mass of the three leading jets in selected events with zero b tags. Measured distribution (points) are compared to the simulated backgrounds (stacked histograms) and one of the signal models (solid line) scaled to 19.7/fb. The shaded area represents the square sum of the systematic uncertainties related to the renormalization and factorization scales for the ttbar and V+jets backgrounds. Get
click on it to get it Figure 1 (b): The invariant mass of the three leading jets in selected events with one b tag. Measured distribution (points) are compared to the simulated backgrounds (stacked histograms) and one of the signal models (solid line) scaled to 19.7/fb. The shaded area represents the square sum of the systematic uncertainties related to the renormalization and factorization scales for the ttbar and V+jets backgrounds. Get
click on it to get it Figure 2 (a): Distribution of MET in events after the signal selection with the modified b tag requirement. Here we use a b tag veto so as to enrich the sample with the V+jets events. The shaded area represents the square sum of the systematic uncertainties related to the renormalization and factorization scales for the ttbar and V+jets backgrounds. Get
click on it to get it Figure 2 (b): Distribution of MET in events after the signal selection with the modified b tag requirement. Here we require two b tags so as to enrich the sample with ttbar events. The shaded area represents the square sum of the systematic uncertainties related to the renormalization and factorization scales for the ttbar and V+jets backgrounds. Get
click on it to get it Figure 3 (a): The 95% C.L. expected and observed CLs limits as a functions of the mass of the scalar DM candidate. The theory cross section is also shown with the red solid line. Get
click on it to get it Figure 3: The 95% C.L. expected and observed CLs limits as a functions of the mass of the vector DM candidate. The theory cross section is also shown with the red solid line. Get

Approved tables

Table Caption
table5.png
Total number of selected events in data compared to the background prediction for MET>350 GeV. The background yields are given with statistical (first) and systematic (second) uncertainties. Uncertainty on the simulated backgrounds (ttbar, single top, and VV) are presented as a square sum of the uncertainties from all of the sources. The QCD background is calculated using all of the other backgrounds and data. Uncertainty on the QCD background is 100% correlated with uncertainties on other backgrounds and therefore is dismissed. The final uncertainty on the sum of all backgrounds is the squre sum of uncertainties on all but QCD backgrounds.

Additional Material

Table Caption
table4.png
Relative uncertainties on the signal and background yields for the signal selection with MET>350 GeV. The last parameter, , is the absolute QCD yield, distributed uniformly in the given range.
table3.png
The probabilities to have zero and one b-tagged jet in the selected QCD () and signal () events.
table2.png
Standard Model backgrounds compared to data.
table1.png
Leading order production cross section of monotop events for scalar (middle column) and vector (right column) DM particles.

-- KhristianKotov - 12 Mar 2014

Topic attachments
I Attachment History Action Size Date Who Comment
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Topic revision: r8 - 2015-03-12 - AlexanderSchmidt
 
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