78 research outputs found
Electroweak corrections to production at hadron colliders
In this paper we present the results from a calculation of the full
electroweak one-loop corrections for vector-boson pair production at
hadron colliders. The cases of proton--antiproton as well as proton--proton
collisions, at the Tevatron and the LHC, respectively, are considered. Results
are presented for the distribution of the invariant mass and for the
transverse momentum of the final-state photon. The higher-order electroweak
effects are numerically significant, in particular for probing possible
anomalous gauge-boson couplings
The Road Towards the ILC: Higgs, Top/QCD, Loops
The International Linear e+e- Collider (ILC) could go into operation in the
second half of the upcoming decade. Experimental analyses and theory
calculations for the physics at the ILC are currently performed. We review
recent progress, as presented at the LCWS06 in Bangalore, India, in the fields
of Higgs boson physics and top/QCD. Also the area of loop calculations,
necessary to achieve the required theory precision, is included.Comment: 7 pages, 1 figure. Plenary talk given at the LCWS06 March 2006,
Bangalore, India. Top part slightly enlarged, references adde
Emotions in context: examining pervasive affective sensing systems, applications, and analyses
Pervasive sensing has opened up new opportunities for measuring our feelings and understanding our behavior by monitoring our affective states while mobile. This review paper surveys pervasive affect sensing by examining and considering three major elements of affective pervasive systems, namely; âsensingâ, âanalysisâ, and âapplicationâ. Sensing investigates the different sensing modalities that are used in existing real-time affective applications, Analysis explores different approaches to emotion recognition and visualization based on different types of collected data, and Application investigates different leading areas of affective applications. For each of the three aspects, the paper includes an extensive survey of the literature and finally outlines some of challenges and future research opportunities of affective sensing in the context of pervasive computing
Hard exclusive photoproduction of mesons
We calculate the differential cross section and single-polarization
observables for the reaction within perturbative QCD,
treating the proton as a quark-diquark system. The phenomenological couplings
of gauge bosons to (spatially extended) diquarks and the quark-diquark
distribution amplitude of the proton are adopted from previous investigations
of baryon form factors and two-photon processes. Going beyond leading order, we
take into account hadron-mass effects by means of a systematic expansion in the
small parameter (hadron mass/ photon energy). With the -meson
distribution amplitude taken from the literature our predictions for the
differential cross section at | t | \agt 4 \text{GeV}^2 seem to provide a
reasonable extrapolation of the low-t data and are also comparable in magnitude
with the results of a two-gluon exchange model in which the gluons are
considered as a remnant of the pomeron. For momentum transfers of a few GeV
hadron-mass effects appear still to be sizeable.Comment: 37 pages, 7 figures, uses RevTeX styl
MSSM Higgs bosons associated with high-pT jets at hadron colliders
The cross section for the production of the lightest neutral Higgs boson in
association with a high-pT hadronic jet, calculated in the framework of the
minimal supersymmetric standard model (MSSM), is presented. The expectations
for the hadronic cross section at the Large Hadron Collider are discussed using
reasonable kinematical cuts. In particular the contributions from superpartner
loops to the cross section and their dependence on the parameters of the MSSM
are investigated and found to be significant. Comparisons show that the
production rate for h0 + jet in the MSSM can differ widely from the
corresponding standard-model prediction.Comment: 20 page
Electroweak corrections to Higgs-strahlung off W/Z bosons at the Tevatron and the LHC with HAWK
The associate production of Higgs bosons with W or Z bosons, known as
Higgs-strahlung, is an important search channel for Higgs bosons at the hadron
colliders Tevatron and LHC for low Higgs-boson masses. We refine a previous
calculation of next-to-leading-order electroweak corrections (and recalculate
the QCD corrections) upon including the leptonic decay of the W/Z bosons,
thereby keeping the fully differential information of the 2-lepton + Higgs
final state. The gauge invariance of the W/Z-resonance treatment is ensured by
the use of the complex-mass scheme. The electroweak corrections, which are at
the level of -(5-10)% for total cross sections, further increase in size with
increasing transverse momenta p_T in differential cross sections. For instance,
for p_T,H >~ 200GeV, which is the interesting range at the LHC, the electroweak
corrections to WH production reach about -14% for M_H = 120GeV. The described
corrections are implemented in the HAWK Monte Carlo program, which was
initially designed for the vector-boson-fusion channel, and are discussed for
various distributions in the production channels pp / p \bar p -> H + l nu_l /
l^-l^+ / nu_l \bar nu_l + X.Comment: 22 p
W^+- H^-+ Associated Production at the Large Hadron Collider
We study the production of a charged Higgs boson in association with a W
boson at the CERN Large Hadron Collider in the context of the minimal
supersymmetric extension of the standard model. This production mechanism is
particularly promising if the charged Higgs boson is too heavy to be generated
by top-quark decay. We compare the contributions due to b b-bar annihilation at
the tree level and gg fusion, which proceeds at one loop. Apart from the total
cross section, we also consider distributions in transverse momentum and
rapidity. We also assess the viability of W^+- H^-+ associated production at
the Fermilab Tevatron after the installation of the Main Injector and the
Recycler.Comment: 16 pages (Latex), 8 figures (Postscript
A simple way to generate high order vacuum graphs
We describe an efficient practical procedure for enumerating and regrouping
vacuum Feynman graphs of a given order in perturbation theory. The method is
based on a combination of Schwinger-Dyson equations and the
two-particle-irreducible ("skeleton") expansion. The regrouping leads to
skeletons containing only free propagators, together with "ring diagrams"
containing all the self-energy insertions. As a consequence, relatively few
diagrams need to be drawn and integrations carried out at any single stage of
the computation and, in low dimensions, overlapping ultraviolet/infrared
subdivergences can be cleanly isolated. As an illustration we enumerate the
graphs contributing to the 4-loop free energy in QCD, explicitly in a continuum
and more compactly in a lattice regularization.Comment: 19 pages. Reference added. To appear in Phys.Rev.
Complete one--loop corrections to e+e- -> sf_i sf_j
We have calculated the complete one-loop corrections to the sfermion pair
production process e+e- -> sf_i sf_j (f = t, b, tau, tau-neutrino) in the
Minimal Supersymmetric Standard Model. Our results also include the previously
calculated SUSY-QCD corrections. We present the details of the renormalization
scheme used. It is found that the weak corrections are of the same magnitude as
the SUSY-QCD corrections at higher energies (sqrt(s) ~ 1TeV). At these energies
the main part of the weak corrections stems from the box contribution. This is
best seen in sneutrino production.Comment: 15 pages, 7 figures, shortened version for publicatio
Gauge-Independent W-Boson Partial Decay Widths
We calculate the partial decay widths of the W boson at one loop in the
standard model using the on-shell renormalization scheme endowed with a
gauge-independent definition of the Cabibbo-Kobayashi-Maskawa (CKM) mixing
matrix. We work in gauge and explicitly verify that the final
expressions are independent of the gauge parameters. Furthermore, we establish
the relationship between the on-shell and definitions of
the CKM matrix, both in its generic form and in the Wolfenstein
parameterization. As a by-product of our analysis, we recover the beta function
of the CKM matrix.Comment: 15 pages; reference added; input parameters updated according to 2000
PDG report; accepted for publication in Phys. Rev.
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