Soft-gluon resummation for Higgs differential distributions at the Large Hadron Collider

We study the transverse-momentum (q_T) and rapidity (y) distributions of the Higgs boson in perturbative QCD, including the most advanced theoretical information presently available: fixed-order perturbation theory at Next-to-Leading Order (NLO) in the large-q_T region (q_T ~ M_H, being M_H the Higgs mass), and soft-gluon resummation at the Next-to-Next-to-Leading Logarithmic accuracy (NNLL) in the small-q_T region (q_T << M_H). We present numerical results for the doubly-differential (q_T and y) cross section for the production of a Standard Model Higgs boson at the Large Hadron Collider (LHC).Comment: Submitted for the SUSY07 proceedings, 4 pages, LaTeX, 4 PostScript figure

Selected Items in Jet Algorithms

I provide a very brief overview of recent developments in jet algorithms, mostly focusing on the issue of infrared-safety.Comment: 3 pages. Talk given at IFAE 2008, Bologna, Italy, 26-28 March 200

PDF uncertainties on the W boson mass measurement from the lepton transverse momentum distribution

We study the charged current Drell-Yan process and we evaluate the proton parton densities uncertainties on the lepton transverse momentum distribution and their impact on the determination of the W-boson mass. We consider the global PDF sets CT10, MSTW2008CPdeut, NNPDF2.3, NNPDF3.0, MMHT2014, and apply the PDF4LHC recipe to combine the individual results, obtaining an uncertainty on MW that ranges between +-18 and +-24 MeV, depending on the final state, collider energy and kind. We discuss the dependence of the uncertainty on the acceptance cuts and the role of the individual parton densities in the final result. We remark that some PDF sets predict an uncertainty on MW of O(10 MeV); this encouraging result is spoiled, in the combined analysis of the different sets, by an important spread of the central values predicted by each group.Comment: version accepted for publication on Phys.Rev.D, one figure and two references adde

Prospects for improving the LHC W boson mass measurement with forward muons

Measurements of the $W$ boson mass are planned by the ATLAS and CMS experiments, but for the time being, these may be unable to compete with the current world average precision of 15~MeV, due to uncertainties in the PDFs. We discuss the potential of a measurement by the LHCb experiment based on the charged lepton transverse momentum $p_T^{\ell}$ spectrum in $W \to \mu\nu$ decays. The unique forward acceptance of LHCb means that the PDF uncertainties would be anti-correlated with those of $p_T^{\ell}$ based measurements by ATLAS and CMS. We compute an average of ATLAS, CMS and LHCb measurements of $m_W$ from the $p_T^{\ell}$ distribution. Considering PDF uncertainties, this average is a factor of 1.3 more precise than an average of ATLAS and CMS alone. Despite the relatively low rate of $W$ production in LHCb, we estimate that with the Run-II dataset, a measurement could be performed with sufficient experimental precision to exploit this anti-correlation in PDF uncertainties. The modelling of the lepton-pair transverse momentum distribution in the neutral current Drell-Yan process could be a limiting factor of this measurement and will deserve further studies.Comment: 10 pages, 3 figures, submitted to EPJ

Non-Diagonal and Mixed Squark Production at Hadron Colliders

We calculate squared helicity amplitudes for non-diagonal and mixed squark pair production at hadron colliders, taking into account not only loop-induced QCD diagrams, but also previously unconsidered electroweak channels, which turn out to be dominant. Mixing effects are included for both top and bottom squarks. Numerical results are presented for several SUSY benchmark scenarios at both the CERN LHC and the Fermilab Tevatron, including the possibilities of light stops or sbottoms. The latter should be easily observed at the Tevatron in associated production of stops and sbottoms for a large range of stop masses and almost independently of the stop mixing angle. Asymmetry measurements for light stops at the polarized BNL RHIC collider are also briefly discussed.Comment: 22 pages, 11 figure

Effect of flavor-dependent partonic transverse momentum on the determination of the WW boson mass in hadronic collisions

Within the framework of transverse-momentum-dependent factorization, we investigate for the first time the impact of a flavor-dependent intrinsic transverse momentum of quarks on the production of $W^{\pm}$ bosons in proton-proton collisions at $\sqrt{s}$ = 7 TeV. We estimate the shift in the extracted value of the $W$ boson mass $M_W$ induced by different choices of flavor-dependent parameters for the intrinsic quark transverse momentum by means of a template fit to the transverse-mass and the lepton transverse-momentum distributions of the $W$-decay products. We obtain $-6\leq \Delta M_{W^+} \leq 9$ MeV and $-4\leq \Delta M_{W^-} \leq 3$ MeV with a statistical uncertainty of $\pm 2.5$ MeV. Our findings call for more detailed investigations of flavor-dependent nonperturbative effects linked to the proton structure at hadron colliders.Comment: 5 pages, 2 tables; revised version with new results with more statistics, more comments, conclusions unchanged, added one referenc

Joint resummation for slepton pair production at hadron colliders

We present a precision calculation of the transverse-momentum and invariant-mass distributions for supersymmetric particle pair production at hadron colliders, focusing on Drell-Yan like slepton pair and slepton-sneutrino associated production at the CERN Large Hadron Collider. We implement the joint resummation formalism at the next-to-leading logarithmic accuracy with a process-independent Sudakov form factor, thus ensuring a universal description of soft-gluon emission, and consistently match the obtained result with the pure perturbative result at the first order in the strong coupling constant, i.e. at O(alpha_s). We also implement three different recent parameterizations of non-perturbative effects. Numerically, we give predictions for ~e_R ~e_R^* production and compare the resummed cross section with the perturbative result. The dependence on unphysical scales is found to be reduced, and non-perturbative contributions remain small.Comment: 12 pages, 4 figure

Emergence of resummation scales in the evolution of the QCD strong coupling and PDFs

The QCD strong coupling and the parton distribution functions (PDFs) of the proton are fundamental ingredients for phenomenology at high-energy facilities such as the Large Hadron Collider (LHC). It is therefore of crucial importance to estimate any theoretical uncertainties associated to them. Both the coupling and the PDFs obey their own renormalisation-group equations (RGEs) whose solution determines their scale evolution. Although the kernels that govern these RGEs have been computed to very high perturbative precision, they are not exactly known. In this contribution, we outline a procedure that allows us to assess the uncertainty on the evolution of the coupling and the PDFs due to our imperfect knowledge of their respective evolution kernels. Inspired by transverse-momentum and threshold resummation, we introduce additional scales, that we dub resummation scales, that can be varied to estimate the uncertainty on the evolution at any scale. As a test case, we consider the deep-inelastic-scattering structure function 2 in a region relevant for the extraction of PDFs. We study the effect of varying these resummation scales and compare it to the usual renormalisation and factorisation scale variations

Higgs at LHC

An overview of recent theoretical results on the Higgs boson and its discovery strategy at ATLAS and CMS will be presented, focusing on the main Higgs analysis effective with low integrated luminosity (less than 30 fb^-1).Comment: 10 pages, 9 figures, talk given at: V Workshop Italiano sulla fisica p-p ad LHC, Perugia, Italy, 30 Jan. - 2 Feb. 200

Higgs boson production at the LHC: Transverse-momentum resummation and rapidity dependence

We consider Higgs boson production by gluon fusion in hadron collisions, We study the doubly-differential transverse-momenturn (qT) and rapidity (y) distribution of the Higgs boson in perturbatiye QCD. In the region of small qT (qT &lt;&lt; M-H, M-H being the mass of the Higgs boson), we include the effect of logarithmically-enhanced contributions due to multiparton radiation to all perturbative orders. We use the impact parameter and double Mellin moments to implement and factorize the multiparton kinematics constraint of transverse- and longitudinal-momentum conservation. The logarithmic terms are then systematically resummed in exponential form. At small qT, we perform the all-order resummation of large logarithms up to next-to-next-to-leading logarithmic accuracy, while at large qT (qT similar to M-H), we apply a matching procedure that recovers the fixed-order perturbation theory up to next-to-leading order. We present quantitative results for the differential cross section in qT and y at the LHC, and we comment on the comparison with the (IT cross section integrated over y