6,895 research outputs found
Q_T resummation in Higgs boson production at the LHC
When considering the transverse momentum distribution (q_T) of the Higgs
boson production it is necessary to separate the small q_T region (q_T << M_H)
from the medium and large (q_T > M_H) one, the former being treated by means of
resummation techniques of logaritmhically-enhanced contributions and the latter
by fixed-order perturbation theory. Then these two approaches have to be
consistently matched to avoid double-counting in the intermediate q_T region.
Here soft gluon resummation is implemented up to NNLL order and the matching to
the corresponding NLO perturbative result is performed. Numerical results are
shown for the LHC. The main features of the differential distribution turn out
to be quite stable with respect to perturbative uncertainties.Comment: 5 pages, 2 figures,. Talk given in italian at "Incontri sulla Fisica
delle Alte Energie", Lecce, Italy, 23-26 April 200
Slepton production in polarized hadron collisions
We calculate cross sections and asymmetries for slepton pair production
through neutral and charged electroweak currents in polarized hadron collisions
for general slepton masses and including mixing of the left- and right-handed
interaction eigenstates relevant for third generation sleptons. Our analytical
results confirm and extend a previous calculation. Numerically, we show that
measurements of the longitudinal single-spin asymmetry at the existing
polarized pp collider RHIC and at possible polarization upgrades of the
Tevatron or the LHC would allow for a determination of the tau slepton mixing
angle and/or the associated supersymmetry breaking parameters Lambda for gauge
mediation and A0 for minimal supergravity. Furthermore, the Standard Model
background from tau pair production can be clearly distinguished due to the
opposite sign of the associated asymmetry.Comment: 16 pages, 4 figures; Tevatron/LHC polarization and tau identification
discussed, typos correcte
Next-to-leading order QCD corrections to W+Z and W-Z production via vector-boson fusion
We present the calculation of the next-to-leading order QCD corrections to
electroweak p p -> e+ nu_e mu+ mu- jj and p p -> e- nubar_e mu+ mu- jj
production at the CERN LHC in the form of a fully flexible parton-level Monte
Carlo program. The QCD corrections to the total cross sections are modest,
changing the leading-order results by less than 10%. At the Born level, the
shape of kinematic distributions can depend significantly on the choice of
factorization scale. This theoretical uncertainty is strongly reduced by the
inclusion of the next-to-leading order QCD corrections.Comment: 15 pages, 6 figures; new figure and comments added; version published
by PR
Squark and Gaugino Hadroproduction and Decays in Non-Minimal Flavour Violating Supersymmetry
We present an extensive analysis of squark and gaugino hadroproduction and
decays in non-minimal flavour violating supersymmetry. We employ the so-called
super-CKM basis to define the possible misalignment of quark and squark
rotations, and we use generalized (possibly complex) charges to define the
mutual couplings of (s)quarks and gauge bosons/gauginos. The cross sections for
all squark-(anti-)squark/gaugino pair and squark-gaugino associated production
processes as well as their decay widths are then given in compact analytic
form. For four different constrained supersymmetry breaking models with
non-minimal flavour violation in the second/third generation squark sector
only, we establish the parameter space regions allowed/favoured by low-energy,
electroweak precision, and cosmological constraints and display the chirality
and flavour decomposition of all up- and down-type squark mass eigenstates.
Finally, we compute numerically the dependence of a representative sample of
production cross sections at the LHC on the off-diagonal mass matrix elements
in the experimentally allowed/favoured ranges.Comment: 35 pages, 29 (partly colour) figures. Some typos corrected, wording
of several paragraphs improved, version accepted by Nucl. Phys.
QCD corrections to Higgs physics at the LHC
We summarize the status of QCD corrections for SM Higgs boson production at hadron colliders and briefly sketch the main search strategies at the LHC
Transverse-Momentum Resummation for Slepton-Pair Production at the LHC
We perform a first precision calculation of the transverse-momentum (q_T)
distribution of slepton pair and slepton-sneutrino associated production at the
CERN Large Hadron Collider (LHC). We implement soft-gluon resummation at the
next-to-leading logarithmic (NLL) level and consistently match the obtained
result to the pure fixed-order perturbative result at leading order (LO) in the
QCD coupling constant, i.e. O(alpha_s). We give numerical predictions for
stau_1 stau_1^* and stau_1 sneutrino_tau^* + stau_1^* sneutrino_tau production,
also implementing recent parameterizations of non-perturbative effects. The
results show a relevant contribution of resummation both in the small and
intermediate q_T-regions and little dependence on unphysical scales and
non-perturbative contributions.Comment: 4 pages, 2 figure
Transverse-momentum resummation and the spectrum of the Higgs boson at the LHC
We consider the transverse-momentum (q_T) distribution of generic high-mass
systems (lepton pairs, vector bosons, Higgs particles, ....) produced in hadron
collisions. At small q_T, we concentrate on the all-order resummation of the
logarithmically-enhanced contributions in QCD perturbation theory. We elaborate
on the -space resummation formalism and introduce some novel features: the
large logarithmic contributions are systematically exponentiated in a
process-independent form and, after integration over q_T, they are constrained
by perturbative unitarity to give a vanishing contribution to the total cross
section. At intermediate and large q_T, resummation is consistently combined
with fixed-order perturbative results, to obtain predictions with uniform
theoretical accuracy over the entire range of transverse momenta. The formalism
is applied to Standard Model Higgs boson production at LHC energies. We combine
the most advanced perturbative information available at present for this
process: resummation up to next-to-next-to-leading logarithmic accuracy and
fixed-order perturbation theory up to next-to-leading order. The results show a
high stability with respect to perturbative QCD uncertainties.Comment: 48 pages, 13 postscript figure
Threshold Effects in Slepton-Pair Production at the LHC
We present a study of threshold resummation effects for slepton pair
production at the Large Hadron Collider (LHC). After confirming the known NLO
QCD corrections and generalizing the NLO SUSY-QCD corrections to the case of
mixing squarks in the virtual loop contributions, we employ the Mellin N-space
resummation formalism to compute logarithmically enhanced soft-gluon terms to
all perturbative orders.Comment: 3 pages, 1 figure, presented at HEP 2007 (Manchester, July 2007
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