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| 2. |
- Alwall, Johan, et al.
(author)
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Interpretation of electron-proton scattering at low Q2
- 2004
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In: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 596, s. 77-83
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Journal article (peer-reviewed)abstract
- Low-Q2 photons do not resolve partons in the proton, which gives problems when applying the deep inelastic scattering formalism, such as an unphysical, negative gluon density extracted from data. Considering instead hadronic fluctuations of the photon, we show that the generalised vector meson dominance model (GVDM) gives a good description of the measured cross section at low Q2, i.e., reproduces F2(x,Q2), using only few parameters with essentially known values. Combining GVDM and parton density functions makes it possible to obtain a good description of F2 data over the whole range of x and Q2.
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| 3. |
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| 4. |
- Alwall, Johan, et al.
(author)
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Quark Asymmetries in the Proton from a Model for Parton Densities
- 2005
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In: Physical Review D. ; 71:094015
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Journal article (peer-reviewed)abstract
- Based on quantum fluctuations in momentum and of the proton into meson-baryon pairs, we develop a physical model for the non-perturbative x-shape of parton density functions in the proton. The model describes the proton structure function and gives a natural explanation of observed quark asymmetries, such as the difference between the anti-up and anti-down sea quark distributions and between the up and down valence distributions. An asymmetry in the momentum distribution of strange and anti-strange quarks in the nucleon is found to reduce the NuTeV anomaly to a level which does not give a significant indication of physics beyond the standard model.
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| 5. |
- Alwall, Johan, 1975-
(author)
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Quark Distributions and Charged Higgs Boson Production : Studies of Proton Structure and New Physics
- 2005
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Doctoral thesis (other academic/artistic)abstract
- The Standard Model describes all elementary particles known today, but at larger energies it will have to be complemented with new particles and interactions. To be able to distinguish new physics at proton colliders such as LHC at CERN, it is essential to have an appropriate description of the colliding protons and their interactions. The study of the proton is important also in itself, to get a better understanding of the non-perturbative aspects of the strong interaction.In paper I-IV of this thesis, a model for the non-perturbative dynamics of quarks and gluons is developed, based on quantum fluctuations in hadrons. The parton distributions of the proton are given by momentum fluctuations, with sea quark distributions generated by fluctuations into baryon-meson pairs. This model can reproduce proton structure function data, as well as measured asymmetries between up and down valence quark distributions and between the anti-up and anti-down sea. It provides an intrinsic charm quark component as indicated by data. It also predicts an asymmetry in the strange sea of the proton, which can explain the NuTeV anomaly first attributed to new physics beyond the Standard Model.Charged Higgs bosons are predicted by several theories for new physics, including Supersymmetry. At proton colliders, the predicted dominant production mechanism is in association with top and bottom quarks. In paper V-VII, different contributions to this production are studied, and an algorithm is developed for combining the two dominant processes gb -> tH+/- and gg -> tbH+/-. The algorithm gives a smooth transition from small to large transverse momenta of the b-quark, which is important when the b-quark is observed. It also gives arguments for the choice of factorisation scale in the process.
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| 6. |
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| 7. |
- Alwall, Johan, et al.
(author)
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Strange quark asymmetry in the nucleon and the NuTeV anomaly
- 2004
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In: Physical Review D. - 0556-2821. ; 70, s. 111505(R)-
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Journal article (peer-reviewed)abstract
- The NuTeV anomaly of a nonuniversal value of the fundamental parameter sin2thetaW in the electroweak theory has been interpreted as an indication for new physics beyond the standard model. However, the observed quantity depends on a possible asymmetry in the momentum distributions of strange quarks and antiquarks in the nucleon. This asymmetry occurs naturally in a phenomenologically successful physical model for such parton distributions, which reduces the NuTeV result to only about 2 standard deviations from the standard model.
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| 8. |
- Andersen, J. R., et al.
(author)
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Small-x phenomenology - Summary of the 3rd Lund small-x workshop in 2004
- 2006
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 48:1, s. 53-105
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Research review (peer-reviewed)abstract
- A third workshop on small-x physics, within the Small-x Collaboration, was held in Hamburg in May 2004 with the aim of overviewing recent theoretical progress in this area and summarizing the experimental status.
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| 9. |
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| 10. |
- Andersson, Bo, et al.
(author)
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ON HIGH-ENERGY LEPTOPRODUCTION
- 1981
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In: Zeitschrift für Physik C Particles and Fields. - 0170-9739. ; C9, s. 233-233
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Journal article (peer-reviewed)
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