133 research outputs found
HIGGS BOSON PRODUCTION IN
The production of the Standard Model Higgs boson in the four-fermion reaction
is studied. The complete tree-level matrix
element, including signal and backgrounds in the standard electroweak theory,
is computed and initial state radiation is taken into account in the
leading-log approximation. A Monte Carlo event generator has been built and
numerical results for some distributions of experimental interest for the
search of the Higgs particle at future electron-positron colliders are shown,
compared with those existing in the literature and commented.Comment: 8 pages, 5 figures available via anonymous ftp at:
ftp://cobra1.pv.infn.it/pub/4f/, files fig#h.ps with #=1,...,5
On Large-Angle Bhabha Scattering at LEP
The theoretical accuracy of the program TOPAZ0 in the large-angle Bhabha
channel is estimated. The physical error associated with the full Bhabha cross
section and its forward and backward components separately is given for some
event selections and several energy points of interest for LEP1 physics, both
for the and non- contributions to the cross section.Comment: 8 pages, LaTeX, six tables, no figure
On the QED Radiator at Order
The leading logarithmic contribution to the QED
radiator in the additive form is considered. The effect of the correction on
two-fermion physics at LEP1 and LEP2 is evaluated and critically compared with
the one of next-to-leading corrections. A critical
comparison with existing estimates for the LEP1 energy range is also performed.
The leading logarithmic corrections turn out to be
relevant in view of the experimental precision already reached at LEP1 and
foreseen at LEP2.Comment: 10 pages, LaTeX, 3 .eps figures; added references, Comments and a
comparison, basic results unchanged; final version to appear in Phys. Lett.
ISR corrections to associated production at future Higgs factories
We evaluate the QED corrections due to initial state radiation (ISR) to
associated Higgs boson production in electron-positron () annihilation
at typical energies of interest for the measurement of the Higgs properties at
future colliders, such as CEPC and FCC-ee. We apply the QED Structure
Function approach to the four-fermion production process , including both signal and background contributions. We
emphasize the relevance of the ISR corrections particularly near threshold and
show that finite third order collinear contributions are mandatory to meet the
expected experimental accuracy. We analyze in turn the r\^ole played by a full
four-fermion calculation and beam energy spread in precision calculations for
Higgs physics at future colliders.Comment: 11 pages, 3 figure
Pricing financial derivatives with neural networks
Abstract Neural network algorithms are applied to the problem of option pricing and adopted to simulate the nonlinear behavior of such financial derivatives. Two different kinds of neural networks, i.e. multi-layer perceptrons and radial basis functions, are used and their performances compared in detail. The analysis is carried out both for standard European options and American ones, including evaluation of the Greek letters, necessary for hedging purposes. Detailed numerical investigation show that, after a careful phase of training, neural networks are able to predict the value of options and Greek letters with high accuracy and competitive computational time
Higgs boson decay into four leptons at NLOPS electroweak accuracy
In view of precision studies of the Higgs sector at the Run II of the LHC,
the improvement of the accuracy of the theoretical prediction is becoming a
pressing issue. In this framework, we detail a calculation of the full
Next-to-Leading Order (NLO) electroweak corrections to Higgs boson decay into
four charged leptons, by considering the gold-plated channel H -> Z(*) Z(*) ->
2l 2l', l,l' = e, mu. We match the NLO corrections with a QED Parton Shower
(PS), in order to simulate exclusive multiple photon emission and provide novel
results at NLOPS electroweak accuracy. We compare our NLO predictions to those
of the program Prophecy4f and present NLOPS phenomenological results relevant
for Higgs physics studies, with particular attention to precision measurements
of the Higgs boson mass, spin-parity assignment and tests of the Standard
Model. Our calculation is implemented in a new code, Hto4l, which can be easily
interfaced to any generator describing Higgs boson production. As an example,
we provide illustrative results for Higgs production and decay in the process
gg -> H -> 4l using POWHEG with NLOPS accuracy in the production mode.Comment: 27 pages, 2 tables, 9 figures. New numerical results and plots for
dressed leptons. Conclusions unchanged. Version to appear in JHE
Neutral current Drell-Yan with combined QCD and electroweak corrections in the POWHEG BOX
Following recent work on the combination of electroweak and strong radiative
corrections to single W-boson hadroproduction in the POWHEG BOX framework, we
generalize the above treatment to cover the neutral current Drell-Yan process.
According to the POWHEG method, we combine both the next-to-leading order (NLO)
electroweak and QED multiple photon corrections with the native NLO and Parton
Shower QCD contributions. We show comparisons with the predictions of the
electroweak generator HORACE, to validate the reliability and accuracy of the
approach. We also present phenomenological results obtained with the new tool
for physics studies at the LHC.Comment: 10 pages, 14 figures, 1 table. One new figure, some plots with
updated results, added text. Final version to appear in EPJ
W gamma production in hadronic collisions using the POWHEG+MiNLO method
We detail a calculation of W gamma production in hadronic collision, at
Next-to-Leading Order (NLO) QCD interfaced to a shower generator according to
the POWHEG prescription supplemented with the MiNLO procedure. The fixed order
result is matched to an interleaved QCD+QED parton shower, in such a way that
the contribution arising from hadron fragmentation into photons is fully
modeled. In general, our calculation illustrates a new approach to the fully
exclusive simulation of prompt photon production processes accurate at the NLO
level in QCD. We compare our predictions to those of the NLO program MCFM,
which treats the fragmentation contribution in terms of photon fragmentation
functions. We also perform comparisons to available LHC data at 7 TeV, for
which we observe good agreement, and provide phenomenological results for
physics studies of the W gamma production process at the Run II of the LHC. The
new tool, which includes W leptonic decays and the contribution of anomalous
gauge couplings, allows a fully exclusive, hadron-level description of the W
gamma process, and is publicly available at the repository of the POWHEG BOX.
Our approach can be easily adapted to deal with other relevant isolated photon
production processes in hadronic collisions.Comment: 38 pages, 5 Tables, 9 Figures. Final version published in JHEP.
Acknowledgments to Galileo Galilei Institute for Theoretical Physics and to
INFN adde
Electroweak Sudakov Corrections to New Physics Searches at the CERN LHC
We compute the one-loop electroweak Sudakov corrections to the production
process Z (nu bar{nu}) + n jets, with n = 1,2,3, in p p collisions at the LHC.
It represents the main irreducible background to new physics searches at the
energy frontier. The results are obtained at the leading and next-to-leading
logarithmic accuracy by implementing the general algorithm of Denner-Pozzorini
in the event generator for multiparton processes ALPGEN. For the standard
selection cuts used by ATLAS and CMS collaborations, we show that the Sudakov
corrections to the relevant observables can grow up to - 40% at sqrt{s} = 14
TeV. We also include the contribution due to undetected real radiation of
massive gauge bosons, to show to what extent the partial cancellation with the
large negative virtual corrections takes place in realistic event selections.Comment: 5 pages, 3 figures, 1 table. Extended discussion on real radiation
processes. Added references. Results unchanged. Version to appear in Phys.
Rev. Let
Precision Measurement of the W-Boson Mass: Theoretical Contributions and Uncertainties
We perform a comprehensive analysis of electroweak, QED and mixed
QCD-electroweak corrections underlying the precise measurement of the W-boson
mass M_W at hadron colliders. By applying a template fitting technique, we
detail the impact on M_W of next-to-leading order electroweak and QCD
corrections, multiple photon emission, lepton pair radiation and factorizable
QCD-electroweak contributions. As a by-product, we provide an up-to-date
estimate of the main theoretical uncertainties of perturbative nature. Our
results can serve as a guideline for the assessment of the theoretical
systematics at the Tevatron and LHC and allow a more robust precision
measurement of the W-boson mass at hadron colliders.Comment: 51 pages, 10 figures and 16 tables. Minor corrections: new citations
and reference to the svn revisions of the POWHEG code. Numerical results and
conclusions unchange
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