Abstract
Abstract The staged increase of the LHC beam energy provides a new class of interesting observables, namely ratios and double ratios of cross sections of various hard processes. The large degree of correlation of theoretical systematics in the cross section calculations at different energies leads to highly precise predictions for such ratios. We present in this letter few examples of such ratios, and discuss their possible implications, both in terms of opportunities for precision measurements and in terms of sensitivity to Beyond the Standard Model dynamics.
Highlights
JHEP08(2012)010 of specific cross sections, to test and improve parton density functions (PDFs) fits, and even to probe the existence of underlying beyond the SM (BSM) phenomena
In this letter we explore the nature of the correlations among theoretical systematics, and the precision potential, of measurements taken at different LHC beam energies
We studied the stability of our results with respect to changes in the PDF parameterizations, as shown in tables 4– 6, where we collect the central values, systematics and shifts relative to the reference NNPDF2.1 NNLO set, obtained by using the MSTW08 and ABKM09 NNLO PDF sets
Summary
The W − ratios obtained with the ABKM09 set differ from NNPDF2.1 and MSTW08 by 2.3 × 10−3, which is nominally a difference of about 2σ, given the individual values of δPDF This difference is much reduced when considering double ratios (W +/W − and Z/W ), and it is unlikely to be measurable, given the uncertainty on the relative luminosity calibration at the two energies, which is ∼ 2%. Scale and PDF uncertainties are comparable in the case of jet production, for both thresholds of pT > 1 TeV and pT > 2 TeV This is the result of the rather different composition of the initial state at the two energies (see section 4), so that the scale dependence at the two energies is only weakly correlated
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