Threshold Resummation for the Production of Four Top Quarks at the LHC.

We compute the total cross section for tt[over ¯]tt[over ¯] production at next-to-leading logarithmic (NLL^{'}) accuracy. This is the first time resummation is performed for a hadron-collider process with four colored particles in the final state. The calculation is matched to the next-to-leading order strong and electroweak corrections. The NLL^{'} corrections enhance the total production rate by 15%. The size of the theoretical error due to scale variation is reduced by more than a factor of 2, bringing the theoretical error significantly below the current experimental uncertainty of the measurement.

NLO+NLL squark and gluino production cross sections with threshold-improved parton distributions.

We present updated predictions for the cross sections for pair production of squarks and gluinos at the LHC Run II. First of all, we update the calculations based on NLO+NLL partonic cross sections by using the NNPDF3.0NLO global analysis. This study includes a full characterization of theoretical uncertainties from higher orders, PDFs and the strong coupling. Then we explore the implications for this calculation of the recent NNPDF3.0 PDFs with NLO+NLL threshold resummation. We find that the shift in the results induced by the threshold-improved PDFs is within the total theory uncertainty band of the calculation based on NLO PDFs. However, we also observe that the central values of the NLO+NLL cross sections are modified both in a qualitative and a quantitative way, illustrating the relevance and impact of using threshold-improved PDFs together with resummed partonic cross sections. The updated NLO+NLL cross sections based on NNPDF3.0NLO are publicly available in the NLL-fast format, and should be an important ingredient for the interpretation of the searches for supersymmetric particles at Run II.

Squark and gluino production cross sections in [Formula: see text] collisions at [Formula: see text] and [Formula: see text] TeV.

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 [Formula: see text] and [Formula: see text] TeV, and at potential future [Formula: see text] colliders operating at [Formula: see text] and [Formula: see text] 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.

Novel tetrahydropyran-based peptidomimetics from a bioisosteric transformation of a tripeptide. Evidence of their activity at melanocortin receptors.

We have prepared novel peptidomimetics based on a 2,4,6-trisubstituted tetrahydropyran. This scaffold was constructed in an isosteric transformation using conceptual constraints imposed on a tripeptide moiety involving O(i)'-C(i+1)(gamma) and O(i)'-N(i+2) formal cyclization modes. A series of regioselective transformations commencing with a substituted dihydropyran-4-one readily provided the required analogues. Specific tetrahydropyrane analogues modeled on PheArgTrp as a truncated version of the melanocortin receptor message sequence, showed activity at the melanocortin receptors MC4R and MC1R. Thus, the 2,4,6-trisubstituted tetrahydropyran scaffold has provided a potentially useful peptidomimetic lead, and conceptual cyclization of peptide moieties can offer a valuable design strategy in peptidomimetic research.

Synthesis of 2,4,5-trisubstituted tetrahydropyrans as peptidomimetic scaffolds for melanocortin receptor ligands.

[reaction: see text] We have synthesized a series of 2,4,5-trisubstituted tetrahydropyran derivatives to determine the utility of this scaffold as a peptidomimetic platform. The key synthetic steps involved a palladium-mediated cross-coupling reaction of a dihydropyran-4-one moiety to introduce R(2) followed by a sequential regio- and diastereoselective reduction of sp(2) carbon centers. Selected compounds have shown biological activity at melanocortin receptors, indicating that this scaffold may be useful in the design of peptidomimetics relating to a tripeptide structure.