917 research outputs found
Higgs production in bottom quark annihilation: Transverse momentum distribution at NNLO+NNLL
We present the inclusive transverse momentum distribution for Higgs bosons
produced in bottom quark annihilation at the LHC. The results are obtained in
the five-flavor scheme. The soft and collinear terms at small are
resummed through NNLL accuracy and matched to the NNLO transverse momentum
distribution at large . We find that the theoretical uncertainty, derived
from a variation of the unphysical scales entering the calculation, is
significantly reduced with respect to lower orders.Comment: 35 pages, 22 figure
Soft gluon resummation for gluon-induced Higgs Strahlung
We study the effect of soft gluon emission on the total cross section
predictions for the associated Higgs production process at the LHC.
To this end, we perform resummation of threshold corrections at the NLL
accuracy in the absolute threshold production limit and in the threshold limit
for production of a system with a given invariant mass. Analytical results
and numerical predictions for various possible LHC collision energies are
presented. The perturbative stability of the results is verified by including
universal NNLL effects. We find that resummation significantly reduces the
scale uncertainty of the contribution, which is the dominant source
of perturbative uncertainty to production. We use our results to evaluate
updated numbers for the total inclusive cross section of associated
production at the LHC. The reduced scale uncertainty of the
component translates into a decrease of the overall scale error by about a
factor of two.Comment: 22 pages, 4 figures, 2 table
Soft gluon resummation of Drell-Yan rapidity distributions: theory and phenomenology
We examine critically the theoretical underpinnings and phenomenological
implications of soft gluon (threshold) resummation of rapidity distributions at
a hadron collider, taking Drell-Yan production at the Tevatron and the LHC as a
reference test case. First, we show that in perturbative QCD soft gluon
resummation is necessary whenever the partonic (rather the hadronic)
center-of-mass energy is close enough to threshold, and we provide tools to
assess when resummation is relevant for a given process. Then, we compare
different prescriptions for handling the divergent nature of the series of
resummed perturbative corrections, specifically the minimal and Borel
prescriptions. We assess the intrinsic ambiguities of resummed results, both
due to the asymptotic nature of their perturbative expansion, and to the
treatment of subleading terms. Turning to phenomenology, we introduce a fast
and accurate method for the implementation of resummation with the minimal and
Borel prescriptions using an expansion on a basis of Chebyshev polynomials. We
then present results for W and Z production as well as both high- and low-mass
dilepton pairs at the LHC, and show that soft gluon resummation effects are
generally comparable in size to NNLO corrections, but sometimes affected by
substantial ambiguities.Comment: 75 pages, 34 figures, pdflate
Associated production at the LHC: theoretical predictions at NLO+NNLL accuracy
We perform threshold resummation of soft gluon corrections to the total cross
section and the invariant mass distribution for the process .
The resummation is carried out at next-to-next-to-leading-logarithmic (NNLL)
accuracy using the direct QCD Mellin space technique in the three-particle
invariant mass kinematics. After presenting analytical expressions we discuss
the impact of resummation on the numerical predictions for the associated Higgs
boson production with top quarks at the LHC. We find that NLO+NNLL resummation
leads to predictions for which the central values are remarkably stable with
respect to scale variation and for which theoretical uncertainties are reduced
in comparison to NLO predictions.Comment: 21 pages, 9 figures; NNLL results accounting now for color
decomposition of the one-loop hard function, discussion of the literature
added, typos correcte
Soft-gluon resummation for pseudoscalar Higgs boson production at hadron colliders
We compute the threshold-resummed cross section for pseudo-scalar MSSM Higgs
boson production by gluon fusion at hadron colliders. The calculation is
performed at next-to-next-to leading logarithmic accuracy. We present results
for both the LHC and Tevatron Run II. We analyze the factorization and
renormalization scale dependence of the results, finding that after performing
the resummation the corresponding cross section can be computed with an
accuracy better than 10%.Comment: 10 pages, 7 figures, accepted by Physics Letters
Four-Loop Cusp Anomalous Dimension From Obstructions
We introduce a method for extracting the cusp anomalous dimension at L loops
from four-gluon amplitudes in N=4 Yang-Mills without evaluating any integrals
that depend on the kinematical invariants. We show that the anomalous dimension
only receives contributions from the obstructions introduced in hep-th/0601031.
We illustrate this method by extracting the two- and three-loop anomalous
dimensions analytically and the four-loop one numerically. The four-loop result
was recently guessed to be f^4 = - (4\zeta^3_2+24\zeta_2\zeta_4+50\zeta_6-
4(1+r)\zeta_3^2) with r=-2 using integrability and string theory arguments in
hep-th/0610251. Simultaneously, f^4 was computed numerically in hep-th/0610248
from the four-loop amplitude obtaining, with best precision at the symmetric
point s=t, r=-2.028(36). Our computation is manifestly s/t independent and
improves the precision to r=-2.00002(3), providing strong evidence in favor of
the conjecture. The improvement is possible due to a large reduction in the
number of contributing terms, as well as a reduction in the number of
integration variables in each term.Comment: 23 pages, revtex; v2,v3: minor typos fixed and references adde
Small- phenomenology at the LHC and beyond: HELL 3.0 and the case of the Higgs cross section
Small- resummation has been proven recently to be a crucial ingredient for
describing small- HERA data, and the inclusion of small- resummation in
parton distribution function (PDF) determination has a sizeable effect on the
PDFs even at the electroweak scale. In this work we explore the implications of
small- resummation at the Large Hadron Collider (LHC) and at a Future
Circular Collider (FCC). We construct the theoretical machinery for resumming
physical inclusive observables at hadron colliders, and describe its
implementation in the public code HELL 3.0. We focus on Higgs production in
gluon fusion as a prototypical example, both because it is sensitive to
small- gluons and because of its importance for the LHC physics programme.
We find that adding small- resummation to the NLO Higgs production cross
section can lead to an increase of up to 10% at FCC, while the effect is
smaller (+1%) at LHC but still important to achieve a high level of precision.Comment: 42 pages, 8 figures. Added new Fig 6 and some discussions. Final
version published in EPJ
Soft-gluon resummation for squark and gluino hadroproduction
We consider the resummation of soft gluon emission for squark and gluino
hadroproduction at next-to-leading-logarithmic (NLL) accuracy in the framework
of the minimal supersymmetric standard model. We present analytical results for
squark-squark and squark-gluino production and provide numerical predictions
for all squark and gluino pair-production processes at the Tevatron and at the
LHC. The size of the soft-gluon corrections and the reduction in the scale
uncertainty are most significant for processes involving gluino production. At
the LHC, where the sensitivity to squark and gluino masses ranges up to 3 TeV,
the corrections due to NLL resummation over and above the NLO predictions can
be as high as 35% in the case of gluino-pair production, whereas at the
Tevatron, the NLL corrections are close to 40% for squark-gluino final states
with sparticle masses around 500 GeV.Comment: 31 pages, 7 figure
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