No Arabic abstract
$Upsilon(nS)$ and $chi_b(nP)$ (n=1,2,3) production at the LHC is studied at next-to-leading order in $alpha_s$ in nonrelativistic QCD. Feeddown contributions from higher $chi_b$ and $Upsilon$ states are all considered for lower $Upsilon$ cross sections and polarizations. The long distance matrix elements (LDMEs) are extracted from the yield data, and then used to make predictions for the $Upsilon(nS)$ polarizations, which are found to be consistent with the measured polarization data within errors. In particular, the $Upsilon(3S)$ polarization puzzle can be understood by a large feeddown contribution from $chi_b(3P)$ states. Our results may provide a good description for both cross sections and polarizations of prompt $Upsilon(nS)$ and $chi_b(nP)$ production at the LHC.
We present next-to-next-to-leading-order (NNLO) QCD corrections to the production of three isolated photons in hadronic collisions at the fully differential level. We employ qT subtraction within MATRIX and an efficient implementation of analytic two-loop amplitudes in the leading-colour approximation to achieve the first on-the-fly calculation for this process at NNLO accuracy. Numerical results are presented for proton-proton collisions at energies ranging from 7 TeV to 100 TeV. We find full agreement with the 8 TeV results of arXiv:1911.00479 and confirm that NNLO corrections are indispensable to describe ATLAS 8 TeV data. In addition, we demonstrate the significance of NNLO corrections for future precision studies of triphoton production at higher collision energies.
We predict the shape of the transverse momentum p_T spectrum of Upsilon production. The distribution at low p_T is dominated by the region of small impact parameter b and may be computed reliably in perturbation theory. We resum to all orders in the strong coupling alpha_s the process-independent large logarithmic contributions that arise from initial-state gluon showers in the small p_T (< M_Upsilon) region. The cross section at large p_T is represented by the alpha_s^3 lowest-order non-vanishing perturbative contribution.
We present the Higgs boson production cross section at Hadron colliders in the gluon fusion production mode through N3LO in perturbative QCD. Specifically, we work in an effective theory where the top quark is assumed to be infinitely heavy and all other quarks are considered to be massless. Our result is the first exact formula for a partonic hadron collider cross section at N3LO in perturbative QCD. Furthermore, this result represents the first analytic computation of a hadron collider cross section involving elliptic integrals. We derive numerical predictions for the Higgs boson cross section at the LHC. Previously this result was approximated by an expansion of the cross section around the production threshold of the Higgs boson and we compare our findings. Finally, we study the impact of our new result on the state of the art prediction for the Higgs boson cross section at the LHC.
We report on the first computation of the next-to-next-to-leading order (NNLO) QCD corrections to $W^{pm}Z$ production in proton collisions. We consider both the inclusive production of on-shell $W^{pm}Z$ pairs at LHC energies and the total $W^{pm}Z$ rates including off-shell effects of the $W$ and $Z$ bosons. In the off-shell computation, the invariant mass of the lepton pairs from the $Z$ boson decay is required to be in a given mass window, and the results are compared with the corresponding measurements obtained by the ATLAS and CMS collaborations. The NNLO corrections range from 8% at $sqrt{s}$=7 TeV to 11% at $sqrt{s}$=14 TeV and significantly improve the agreement with the LHC data at $sqrt{s}$=7 and 8 TeV.
A fully differential calculation of the next-to-leading order QCD corrections to the production of Z-boson pairs in association with a hard jet at the Tevatron and LHC is presented. This process is an important background for Higgs particle and new physics searches at hadron colliders. We find sizable corrections for cross sections and differential distributions, particularly at the LHC. Residual scale uncertainties are typically at the 10% level and can be further reduced by applying a veto against the emission of a second hard jet. Our results confirm that NLO corrections do not simply rescale LO predictions.