Abstract
Current LHC searches for new colored particles generally focus on their pair production channels and assume any single production to be negligible. We argue that such an assumption may be unnecessary in some cases. Inclusion of model dependent single productions in pair production searches (or vice versa) can give us new information about model parameters or better exclusion limits. Considering the example of the recent CMS search for first generation scalar leptoquarks in the pair production channel, we illustrate how single productions can be systematically included in the signal estimations and demonstrate how it can affect the mass exclusion limits and give new bounds on leptoquark-lepton-quark couplings. We also estimate the effect of the pair production in the more recent CMS search for scalar leptoquarks in single production channels.
Highlights
LQs are hypothetical color-triplet bosons that carry lepton quantum numbers
We show the theoretical cross-sections for pair production at the leading order (LO) and inclusive single productions for eejj and eνjj channels with M q = 550, 650, 750 GeV and λ = 0.3, 0.5
For λ = λQED = 0.3 the CMS analysis in ref. [1] underestimates the mass ELs
Summary
The limits from HERA data [20, 21] roughly indicate that the generic (scalar) LQ-leptonquark coupling, λ could even be larger than 0.5 if M q 600 GeV. In the leading order (LO) of couplings, the pair production of LQs is almost independent of λ (see figures 1a–1d) except for the t-channel lepton exchange contribution whose amplitude is proportional to λ2 (figure 1e). For small λ, this contribution is quite small, e.g. with λ = 0.3 it amounts to only about 5 percent of the λ independent contribution to the LO pair production cross-section for M q = 650 GeV (see table 1). New subprocess of three-body single production (NS3): it originates at O(gs2λ) and includes diagrams for pp → q j that do not count as BR1 single production (see figures 1h–1j for example)
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