Squark and gluino production cross sections in \(pp\) collisions at \(\sqrt{s} = 13, 14, 33\) and \(100\) TeV
Christoph Borschensky
2
Michael Krmer
1
Anna Kulesza
2
Michelangelo Mangano
0
Sanjay Padhi
4
Tilman Plehn
3
Xavier Portell
0
0
European Organization for Nuclear Research, CERN
,
Meyrin
,
Switzerland
1
Institute for Theoretical Particle Physics and Cosmology, RWTH Aachen University
,
52056 Aachen
,
Germany
2
Institut fur Theoretische Physik, Westfalische Wilhelms-Universitat Munster
,
48149 Munster
,
Germany
3
Institut fur Theoretische Physik, Universitat Heidelberg
,
Heidelberg
,
Germany
4
University of California, San Diego
,
USA
We present state-of-the-art cross section predictions for the production of supersymmetric squarks and gluinos at the upcoming LHC run with a centre-of-mass energy of s = 13 and 14 TeV, and at potential future pp colliders operating at s = 33 and 100 TeV. The results are based on calculations which include the resummation of soft-gluon emission at next-to-leading logarithmic accuracy, matched to next-to-leading order supersymmetric QCD corrections. Furthermore, we provide an estimate of the theoretical uncertainty due to the variation of the renormalisation and factorisation scales and the parton distribution functions.
-
pp qq , qq , q g, g g + X ,
together with the charge conjugated processes. In Eq. (1) the
chiralities of the squarks, q = (qL , qR ), are suppressed, and
we focus on the production of the partners of the (u, d, c, s, b)
quarks which we assume to be mass degenerate. The
production of the SUSY partners of top quarks, the stops (t), and,
when appropriate, the partners of bottom quarks, the
sbottoms (b), has to be considered separately due to parton
distribution function (PDF) effects and potentially large mixing
affecting the mass splittings. In this case, we explicitly
specify the different mass states in the pair-production processes,
pp ti ti, bi bi + X
i = 1, 2 ,
where i = 1, 2 corresponds to the lighter and heavier states,
respectively.
Given the importance of SUSY searches at the LHC,
accurate knowledge of theoretical predictions for the cross
sections is required. Starting from mid-2011, ATLAS and CMS
analyses have been based on resummed results at the
nextto-leading logarithmic (NLL) accuracy matched to
next-toleading order (NLO) predictions, referred to as NLO + NLL
in the rest of this paper.
With minimal assumptions on SUSY productions and
decays, the interpretation of the current LHCdata with s =
7 and 8 TeV leads to the mass bound for the gluino and light
squarks as mg = mq > 1.7 TeV, or mg > 1.4 TeV with a
decoupled squark sector, and mq > 850 GeV with the other
decoupled particles, based on the ATLAS/CMS studies. Pair
productions of SUSY third-generation lighter states also have
a mass bound above mt,b > 750 GeV. This paper provides a
reference for the evaluation of SUSY squark and gluino
production cross sections and their theoretical uncertainties for
the extended range of superpartner masses within the reach
of the upcoming LHC runs at s = 13 and 14 TeV, and for
future high-energy hadron colliders at s = 33 and 100 TeV.
The paper follows [3] in which results for s = 7 TeV were
presented. The detailed cross section values for the relevant
processes and SUSY models considered by the experiments,
as well as the results for lower LHC centre-of-mass energies,
are collected at the SUSY cross section working group web
page [4].
The next section briefly describes the current
state-of-theart higher-order calculations for squark and gluino
hadroproduction, followed by the prescription used for the treatment
of theoretical uncertainties in Sect. 3. In Sect. 4 the
production cross sections are presented, and a summary of the results
and of the future prospects is given in Sect. 5.
2 Higher-order calculationsNLO + NLL
The dependence of hadron collider observables on the
renormalisation and factorisation scales is an artifact of
perturbation theory and is generically reduced as higher-order
perturbative contributions are included. Assuming that there is no
systematic shift of an observable from order to order in
perturbation theory, for example due to the appearance of new
production channels, the range of rates covered by the scale
dependence at a given loop order should include the true
prediction of this rate. The scale dependence therefore provides
a lower limit on the theory uncertainty of a QCD prediction,
which becomes smaller as higher-order SUSY-QCD
corrections are included. To estimate the scale uncertainty in this
study we vary simultaneously factorisation and
renormalisation scales, within a range of 0.52 times the reference central
scale , where is the average of the two sparticle masses
in the final state.
The corrections often increase the size of the cross
section with respect to the leading-order prediction [57] if the
renormalisation and factorisation scales are chosen close to
the average mass of the produced SUSY particles. As a result,
the SUSY-QCD corrections have a substantial impact on the
determination of mass exclusion limits (...truncated)