Paolo Bolzoni

A subtraction scheme for computing QCD jet cross sections at NNLO: integrating the iterated singly-unresolved subtraction terms

We perform the integration of all iterated singly-unresolved subtraction terms, as defined in ref. [1], over the two-particle factorized phase space. We also sum over the unresolved parton flavours. The final result can be written as a convolution (in colour space) of the Born cross section and an insertion operator. We spell out the insertion operator in terms of 24 basic integrals that are defined explicitly. We compute the coefficients of the Laurent expansion of these integrals in two different ways, with the method of Mellin-Barnes representations and sector decomposition. Finally, we present the Laurent-expansion of the full insertion operator for the specific examples of electron-positron annihilation into two and three jets.

Vector boson fusion at next-to-next-to-leading order in QCD: Standard model Higgs boson and beyond

Weak vector boson fusion provides a unique channel to direct ly probe the mechanism of electroweak symmetry breaking at hadron colliders. We present a method that allows to calculate total cross sections to next-to-next-to-leading order (NN LO) in QCD for an arbitraryV∗V∗→ X process, the so-called structure function approach. By dis cussing the case of Higgs production in detail, we estimate several classes of previously neglecte d contributions and we argue that such method is accurate at a precision level well above the typica l residual scale and PDF uncertainties at NNLO. Predictions for cross sections at the Tevatron and t he LHC are presented for a variety of cases: the Standard Model Higgs (including anomalous cou plings), neutral and charged scalars in extended Higgs sectors and (fermiophobic) vector resona nce production. Further results can be easily obtained through the public use of the VBF@NNLO code.

Timelike Single-logarithm-resummed Splitting Functions

We calculate the single logarithmic contributions to the quark singlet and gluon matrix of timelike splitting functions at all orders in the modified minimal-subtraction (MS¯) scheme. We fix two of the degrees of freedom of this matrix from the analogous results in the massive-gluon regularization scheme by using the relation between that scheme and the MS¯ scheme. We determine this scheme transformation from the double logarithmic contributions to the timelike splitting functions and the coefficient functions of inclusive particle production in e+e− annihilation now available in both schemes. This approach fixes two of the four degrees of freedom, and a third degree of freedom is fixed by reasonable physical assumptions. The results agree with the fixed-order results at next-to-next-to-leading order in the literature.

Fully double-logarithm-resummed cross sections

Abstract We calculate the complete double logarithmic contribution to cross sections for semi-inclusive hadron production in the modified minimal-subtraction ( MS ¯ ) scheme by applying dimensional regularization to the double logarithm approximation. The full double logarithmic contribution to the coefficient functions for inclusive hadron production in e + e − annihilation is obtained in this scheme for the first time. Our result agrees with all fixed order results in the literature, which extend to next-to-next-to-leading order.

Inclusive J/psi and psi(2S) production from b-hadron decay in p anti-p and pp collisions

We study the inclusive production of J/psi and psi(2S) mesons originating from the decays of bottom-flavored hadrons produced in p anti-p collisions at the Fermilab Tevatron and in pp collisions at the CERN LHC. We work at next-to-leading order in the general-mass variable-flavor-number scheme (GM-VFNS) implemented with nonperturbative fragmentation functions fitted to e^+e^- data of inclusive b-hadron production exploiting their universality. The three-momentum distributions of the charmonia used were extracted from B-decay data in the framework of nonrelativistic-QCD factorization. Comparing the theoretical predictions thus obtained with transverse-momentum distributions measured by the CDF II, ALICE, ATLAS, CMS, and LHCb Collaborations, we find excellent overall agreement as for both absolute normalization and lineshape, which provides a nontrivial test of the GM-VFNS over wide ranges of center-of-mass energy, transverse momentum, and rapidity.

Timelike structure functions and hadron multiplicities

In this talk we discuss the results obtained in the new approach that we recently introduced to consider and include both the perturbative and nonperturbative contributions to the evolution of the gluon and quark avarage multiplicities. We report on our progresses in solving a longstanding puzzle of QCD. The new formalism is motivated by recent important theoretical developments in timelike small-x resummation which are also discussed mostly from an historical point of view. We have extended our global analysis to fit the available data adding the strong coupling constant as a fit parameter. In this way our best fit gives

A new approach to gluon-quark multiplicity ratio

\alpha_s(M_z)=0.124\pm 0.005

Inclusive lepton production from heavy hadron decay in pp collisions at the LHC

and for the corresponding

NNLO jet cross sections by subtraction

\chi^2

Higgs production at NNLO in QCD: the VBF channel

we have obtained a further improvement.