Measurement of Dijet Angular Distributions and Search for Quark Compositeness in pp Collisions at 7 TeV


Dijet angular distributions are measured over a wide range of dijet invariant masses in pp collisions at sqrt(s) = 7 TeV, at the CERN LHC. The event sample, recorded with the CMS detector, corresponds to an integrated luminosity of 36 pb^{-1}. The data are found to be in good agreement with the predictions of perturbative QCD, and yield no evidence of quark compositeness. With a modified frequentist approach, a lower limit on the contact interaction scale for left-handed quarks of L^{+} = 5.6 TeV (L^{-} = 6.7 TeV) for destructive (constructive) interference is obtained at the 95% confidence level.

Approved Plots from EXO-10-009 ( click on plot to get .pdf )

Normalized dijet angular distributions in several Mjj ranges, shifted vertically by the additive amounts given in parentheses in the figure for clarity. The data points include statistical and systematic uncertainties. The results are compared with the predictions of pQCD at NLO (shaded band) and with the predictions including a contact interaction term of compositeness scale L^{+} = 5 TeV (dashed histogram) and L^{-} = 5 TeV (dotted histogram). The shaded band shows the effect on the NLO pQCD predictions due to mu_r and mu_f scale variations and PDF uncertainties, as well as the uncertainties from the non-perturbative corrections added in quadrature.

Observed CLs (solid line) and expected CLs (dashed line) with one (two) standard deviation(s) indicated by the dark (light) band as a function of the contact interaction scale L^{+}. The 95% confidence level limits on L^{+} are extracted from the intersections of the observed and expected CLs lines with the horizontal line at CLs=0.05.

Link to the paper on the arXiv

-- SuvadeepBose - 11-Mar-2011

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PDFpdf limitcalc_withsys_plots_brigther.pdf r1 manage 4.6 K 2011-03-11 - 08:53 AndreasHinzmann  
PNGpng limitcalc_withsys_plots_brigther.png r1 manage 118.0 K 2011-03-11 - 08:59 AndreasHinzmann  
PDFpdf limitcalc_withsys_plusminus_v7.pdf r1 manage 4.6 K 2011-04-20 - 10:10 AndreasHinzmann  
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PDFpdf nlo_final-AK5Calo-paper-v5.pdf r1 manage 14.4 K 2011-03-11 - 08:52 AndreasHinzmann  
PNGpng nlo_final-AK5Calo-paper-v5.png r1 manage 162.2 K 2011-03-11 - 08:58 AndreasHinzmann  
PDFpdf nlo_final_plusminus_v5.pdf r1 manage 14.2 K 2011-04-20 - 10:09 AndreasHinzmann  
PNGpng nlo_final_plusminus_v5.png r1 manage 165.0 K 2011-04-20 - 10:09 AndreasHinzmann  
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