We perform the transverse-momentum resummation for W + W − , ZZ, and W ± Z pair productions at the next-to-next-to-leading logarithmic accuracy using soft-collinear effective theory for √ S = 8 TeV and √ S = 14 TeV at the LHC, respectively. Especially, this is the first calculation of W ± Z transverse-momentum resummation. We also include the non-perturbative effects and discussions on the PDF uncertainties. Comparing with the next-to-leading logarithmic results, the next-to-next-to-leading logarithmic resummation can reduce the dependence of the transversemomentum distribution on the factorization scales significantly. Finally, we find that our numerical results are consistent with data measured by CMS collaboration for the ZZ production, which have been only reported by the LHC experiments for the unfolded transverse-momentum distribution of the gauge boson pair production so far, within theoretical and experimental uncertainties.

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We investigate the resummation effects with a jet veto, for W ± Z and ZZ productions at the LHC in soft-collinear effective theory. We present the invariant mass distributions and the total cross section with different jet veto p veto T and jet radius R for these process at Next-to-Next-to-LeadingLogarithmic level. Our results show that the jet-veto resummation can increase the jet-veto cross section and decrease the scale uncertainties, especially in the large center-of-mass energy. We find that for p veto T > 30 GeV and R = 0.4, the resummation results can increase POWHEG+PYTHIA predictions by about 19% for W ± Z production and 18% for ZZ production, respectively. Our results agree with the CMS data for W ± Z productions within 2σ C.L. at √ S = 8 TeV, which can explain the 2σ discrepancy between the CMS experimental results and theoretical predictions based on NLO calculation with parton showers.

We perform the threshold resummation for W ± Z and ZZ pair production at the next-to-nextto-leading logarithmic accuracy in Soft-Collinear Effective Theory at the LHC. Our results show that the resummation effects increase the total cross sections by about 7% for ZZ production and 12% for W ± Z production with √ S = 7, 8, 13 and 14 TeV, respectively, and the scale uncertainties are significantly reduced. Besides, our numerical results are well consistent with experimental data reported by the ATLAS and CMS collaborations.

We propose a simplified model to study the possible new heavy diphoton resonance from cascade decay of a heavier particle at colliders, which may be related to the dark matter or other new physics beyond the standard model. Model-independent constraints and predictions on the allowed couplings for generating the observed diphoton data are studied in detail. We demonstrate that this scenario can be tested by the possible four-photon signal or the W W/ZZ/Zγ resonances. Meanwhile, this cascade decay scenario also provides us with the dark matter candidates, which is consistent with the observed dark matter relic density. * wangyan728@ihep.ac.cn arXiv:1512.06732v4 [hep-ph]