Search for Pair Production of First-Generation Scalar Leptoquarks Using Events Containing Two Electrons And Two Jets Produced in pp Collisions at √s = 7 TeV

Abstract

A search for pair production of first-generation scalar leptoquarks is performed in the final state containing two electrons and two jets using proton-proton collision data at √s = 7 TeV. The data sample used corresponds to an integrated luminosity of 33 pb-1 collected with the CMS detector at the CERN LHC. The number of observed events is in good agreement with the predictions for the standard model background processes, and an upper limit is set on the leptoquark pair production cross section times β^2 as a function of the leptoquark mass, where β is the branching fraction of the leptoquark decay to an electron and a quark. A 95% confidence level lower limit is set on the mass of a first-generation scalar leptoquark at 384 GeV for β =1, which is the most stringent direct limit to date.

Plots from PAPER EXO-10-005 based on 33.2 pb-1 (click on plot to get .pdf)

In the following plots:

• Pre-selection is defined as:
  • at least two electrons with p_T > 30 GeV and abs(η) < 2.5
  • at least two jets with p_T > 30 GeV and abs(η) < 3
  • minimum ΔR between any of the 2 selected electrons and any of the 2 selected jets greater than 0.7.
  • M_ee > 50 GeV
  • S_T > 250 GeV (scalar sum of the p_T of the 2 selected electrons and 2 selected jets)
• Full selection includes the pre-selection cuts and
  • M_ee > 125 GeV
  • S_T > f(LQ mass hypothesis)
• The Z+jets MC has been normalized using the data/MC ratio (1.20 +- 0.14) determined at the Z boson mass after the pre-selection.
• Other backgrounds include W+jets, di-boson, and single top.
• All background histograms are cumulative.
• The black dots are data, with the square root of the number of entries used as uncertainties.

Figure	Abbreviated Caption
	M_ee after pre-selection
	S_T after full selection (except the cut on S_T itself)
	Upper limit on the LQ cross section x Beta^2 vs. LQ mass
	Minimum Beta for LQ hypothesis exclusion vs. LQ mass

Additional APPROVED Plots based on 33.2 pb-1 (click on plot to get .pdf)

	p_T 1st electron after pre-selection
	Eta 1st electron after pre-selection
	p_T 2nd electron after pre-selection
	Eta 2nd electron after preselection
	p_T 1st jet after preselection
	Eta 1st jet after preselection
	p_T 2nd jet after preselection
	Eta 2nd jet after preselection
	S_T after preselection (except the cut on S_T itself)
	M_ej after pre-selection. There are 2 ways to combine the 2 leading electrons and the 2 leading jets to make 2 candidate LQs; the pair of M_{ej} values with minimum difference is used.
	Mej after final selection for M_LQ=300 GeV. There are 2 ways to combine the 2 leading electrons and the 2 leading jets to make 2 candidate LQs; the pair of M_{ej} values with minimum difference is used.

Event Displays of the 3 Highest-S_T events (Black or White background) from the PAPER analysis (33.2 pb-1)

• The details on the 7 events that passed the final selection (prior to final S_T cut) in this file

run148864_ls435_evt501826759_ST585GeV
run148822_ls204_evt218300385_ST367GeV
run149181_ls1209_evt1189919527_ST305GeV

-- PaoloRumerio - 28-Nov-2010