Observation of a diffractive contribution to dijet production in proton-proton collisions at = 7 TeV

Abstract

The cross section for dijet production in pp collisions at sqrt(s) = 7 TeV is presented as a function of xi, a variable that approximates the fractional momentum loss of the scattered proton in single-diffractive events. The analysis is based on an integrated luminosity of 2.7 inverse nanobarns collected with the CMS detector at the LHC at low instantaneous luminosities, and uses events with jet transverse momentum of at least 20 GeV. The dijet cross section results are compared to the predictions of diffractive and nondiffractive models. The low-xi data show a significant contribution from diffractive dijet production, observed for the first time at the LHC. The associated rapidity gap survival probability is estimated.

Approved plots

Figure	Caption
	Figure 2a: The generated versus generated correlations for single-diffractive dijet events simulated by PYTHIA8.
	Figure 2b: The generated versus reconstructed correlations for single-diffractive dijet events simulated by PYTHIA8.
	Figure 3a: Reconstructed transverse-momentum distributions of the leading jet (black dots) compared to detector-level MC simulations (histograms) generated with two non-diffractive models (PYTHIA6 Z2 and PYTHIA8 tune 1).
	Figure 3b: Reconstructed transverse-momentum distributions of the second-leading jet (black dots) compared to detector-level MC simulations (histograms) generated with two non-diffractive models (PYTHIA6 Z2 and PYTHIA8 tune 1).
	Figure 4a: Reconstructed pseudorapidity distributions of the leading jet (black dots) compared to detector-level MC simulations (histograms) generated with two non-diffractive models (PYTHIA6 Z2 and PYTHIA8 tune 1).
	Figure 4b: Reconstructed pseudorapidity distributions of the second leading jet (black dots) compared to detector-level MC simulations (histograms) generated with two non-diffractive models (PYTHIA6 Z2 and PYTHIA8 tune 1).
	Figure 5a: Reconstructed pseudorapidity distributions of the leading jet after the selection (black dots) compared to three detector-level MC simulations (histograms).
	Figure 5b: Reconstructed pseudorapidity distributions of the second-leading jet after the selection (black dots) compared to three detector-level MC simulations (histograms).
	Figure 6: Reconstructed distribution compared to detector-level MC predictions with and without diffractive dijet production.
	Figure 7: Reconstructed distributions with (open symbols) and without (closed symbols) the (or ) condition are compared to detector-level MC predictions including diffractive dijet production.
	Figure 8: The differential cross section for inclusive dijet production as a function of for jets with axes in the range and GeV. The error bars indicate the statistical uncertainty and the band represents the systematic uncertainties added in quadrature. The predictions of non-diffractive (PYTHIA6 Z2 and PYTHIA8 tune 1) and diffractive (POMPYT SD, POMWIG SD and PYTHIA8 SD+DD) MC generators are also shown, along with that of the NLO calculation based on POWHEG (first bin only).

Presentations

* FSQ meeting (31/01/2012) Approval2

* FSQ meeting (17/01/2012) Approval

* CMS week (28/06/2011) Pre-approval

CADI info

* CADI info

-- AlexandrProskuryakov - 02-Apr-2011

Responsible: AlexandrProskuryakov

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