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| 3. |
- Andersson, Bo, et al.
(författare)
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A general model for jet fragmentation
- 1983
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Ingår i: European Physical Journal C. - 0170-9739. ; 20:4, s. 317-329
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Tidskriftsartikel (refereegranskat)abstract
- We present a general condition on quark fragmentation which gives a hadron distribution satisfying Lorentz invariance and causality. The hadronization can be described as an iterative cascade process, symmetric with respect to iteration from the quark and the antiquark ends. The possible particle distributions are strongly restricted, with few free parameters related to the total multiplicity and corelations in rapidity. These parameters can be given an appealing interpretation in terms of the expected area and perimeter dependence of Wilson loop integrals.
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| 8. |
- Andersson, Bo, et al.
(författare)
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Coherence Effects in Deep Inelastic Scattering
- 1989
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Ingår i: Zeitschrift für Physik C Particles and Fields. - 0170-9739. ; 43:4, s. 625-632
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Tidskriftsartikel (refereegranskat)abstract
- We present a framework for deep inelastic scattering, with bound state properties in accordance with a QCD force field acting like a vortex line in a colour superconducting vacuum, which implies some simple coherence effects. Within this scheme one may describe the results of present energies very well, but one obtains an appreciable depletion of gluon radiation in the HERA energy regime.
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| 9. |
- Andersson, Bo, et al.
(författare)
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Gluon Splitting in the Color Dipole Cascades
- 1990
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Ingår i: Nuclear Physics B. - 0550-3213. ; 339:2, s. 393-405
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Tidskriftsartikel (refereegranskat)abstract
- We present a method to implement the gluon splitting process, g → QQ, into the dipole approximation to QCD cascades. It is known that due to the uncertainties in the interpolation between the pole regions, there are large uncertainties in the results. We show that there are further uncertainties due to the ordering in phase space of the gluon emission and gluon splitting processes. We present two options called the IO scheme (for independent dipoles) and another, the DO scheme (corresponding to an ordering in transverse momentum of the emissions) both of which lead to enhanced (hard) QQ-pair production, as compared to conventional cascades. We compare to present experimental data and give predictions for LEP energies.
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| 11. |
- Andersson, Bo, et al.
(författare)
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Implications of a large vector meson production on quark jet fragmentation and large p T reactions
- 1978
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 18:4, s. 193-195
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Tidskriftsartikel (refereegranskat)abstract
- A large vector meson production in quark jet fragmentation implies characteristic differences between the kaon and pion spectra. This prediction is verified in a recent SLAC-MIT experiment. Similar considerations are relevant for the c-quark fragmentation into D-mesons, as observed in ν scattering experiments.The difference in kaon and pion spectra provides a test of the hard quark-quark scattering description of large p T events. In particular the K+/π+ ratio (∼ 1/2 for single particle triggers) should be around 0.1-0.2 for jet triggers.
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| 12. |
- Andersson, Bo, et al.
(författare)
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Investigations into the BFKL mechanism with a running QCD coupling
- 1998
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Ingår i: Physical Review D (Particles and Fields). - 0556-2821. ; 57:9, s. 5543-5554
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Tidskriftsartikel (refereegranskat)abstract
- We present approximations of varying degree of sophistication to the integral equations for the (gluon) structure functions of a hadron ("the partonic flux factor") in a model valid in the leading log approximation with a running coupling constant. The results are all of the BFKL type, i.e., a power in the Bjorken variable x(B)(-lambda) with the parameter lambda determined from the size alpha(0) of the "effective" running coupling <(alpha)over bar>=3 alpha(s)/pi =alpha(0)/ln(k(perpendicular to)(2)) and varying depending upon the treatment of the transverse momentum pole, we also consider the implications for the transverse momentum (k(perpendicular to)) fluctuations along the emission chains and we obtain an exponential falloff in the relevant kappa=ln(k(perpendicular to)(2)) variable, i.e., an inverse power (k(perpendicular to)(2))(-(2+lambda)) with the same parameter lambda. This is different from the BFKL result for a fixed coupling, where the distributions are Gaussian in the kappa variable with a width as in a Brownian motion determined by "the length" of the emission chains, i.e., In(1/x(B)). The results are verified by a realistic Monte Carlo simulation and we provide a simple physics motivation for the change.
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| 13. |
- Andersson, Bo, et al.
(författare)
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Is there screwiness at the end of the QCD cascades?
- 1998
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Ingår i: Journal of High Energy Physics. - : Springer Science and Business Media LLC. - 1029-8479. ; :9
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Tidskriftsartikel (refereegranskat)abstract
- We discuss what happens at the end of the QCD cascades. We show that, with just a few reasonable assumptions, the emission of soft gluons is constrained to produce an ordered field in the form of a helix. We describe how to modify the Lund fragmentation scheme in order to fragment such a field. Our modified fragmentation scheme yields results which are consistent with current experimental measurements, but predicts at least one signature which should be observable.
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| 14. |
- Andersson, Bo, et al.
(författare)
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ON HIGH-ENERGY LEPTOPRODUCTION
- 1981
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Ingår i: Zeitschrift für Physik C Particles and Fields. - 0170-9739. ; C9, s. 233-233
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Tidskriftsartikel (refereegranskat)
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| 17. |
- Andersson, Bo, et al.
(författare)
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Quark Jet Fragmentation
- 1979
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 19:2, s. 184-190
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Tidskriftsartikel (refereegranskat)abstract
- A semiclassical model is presented for the way the energy of a fast quark is transformed into observable hadrons. It reproduces the features of 1 + 1 dimensional QED (the Schwinger model) concerning a flat rapidity distribution in the central region. In particular the model predicts that the probability to find a meson containing a leading quark is independent of the Feynman scaling variable. Also a quark jet interpretation of low PT jets in hadronic interactions is discussed shortly.
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| 18. |
- Andersson, Bo, et al.
(författare)
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Small x phenomenology: summary and status
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 25:1, s. 77-101
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Forskningsöversikt (refereegranskat)abstract
- The aim of this paper is to summarize the general status of our understanding of small-x physics. It is based on presentations and discussions at an informal meeting OIL this topic held in Lund, Sweden, in March 2001. This document also marks the founding of an informal collaboration between experimentalists and theoreticians with a special interest in small-x physics. This paper is dedicated to the memory of Bo Andersson. who died unexpectedly from a heart attack on March 4th, 2002.
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| 19. |
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| 20. |
- Andersson, Bo, et al.
(författare)
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Structure Functions and general final state properties in the linked dipole chain model
- 1996
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Ingår i: Zeitschrift für Physik C Particles and Fields. - : Springer Science and Business Media LLC. - 0170-9739 .- 1431-5858. ; 71:4, s. 613-624
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Tidskriftsartikel (refereegranskat)abstract
- We have in an earlier paper, [1], presented a generalization, the Linked Dipole Chain Model LDC, of the model developed by Ciafaloni-Catani-Fiorani-Marchesini, [2], to decribe the structure functions and the states in Deep Inelastic Scattering events. In this paper we would like to present an investigation of a set of general features of the LDC Model, viz the behaviour of the structure functions (we will show how the result interpolates in a precise way in between the well-known DGLAP and BFKL approaches), the average bremsstrahlung emission in the states and finally a partitioning of the structure functions into three different channels: the ''ordinary'' parton-probe events, where all bremsstrahlung emissions are below the probe Q(2), the boson-gluon fusion events where the last splitting of the par ton chains contain transverse momentum above Q(2), and the resolved Rutherford scattering events between the probe and the hadron (where the largest transverse momentum occur somewhere along the emission lines away from the ends).
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| 21. |
- Andersson, Bo, et al.
(författare)
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The Feynman-Wilson gas and the Lund model
- 1999
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 7:2, s. 251-261
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Tidskriftsartikel (refereegranskat)abstract
- We derive a partition function for the Lund fragmentation model and compare it with that of a classical gas. For a fixed rapidity “volume” this partition function corresponds to a multiplicity distribution which is very close to a binomial distribution. We compare our results with the multiplicity distributions obtained from the JETSET Monte Carlo for several scenarios. Firstly, for the fragmentation vertices of the Lund string. Secondly, for the final state particles both with and without decays.
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| 22. |
- Andersson, Bo, et al.
(författare)
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The flavouring of a gluon jet
- 1990
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Ingår i: Physics Letters B. - 0370-2693. ; 236:4, s. 461-465
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Tidskriftsartikel (refereegranskat)abstract
- We show that the hard qq̄ production is very sensitive to the details of the parton shower and that our treatment based on the dipole approximation gives significantly larger production than “conventional” parton showers. For our model we find qualitative agreement with experimental data for the Kπ ratio and D-meson production in high-pT jets.
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| 25. |
- Asif, Sana, et al.
(författare)
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Heparinization of cell surfaces with short peptide-conjugated PEG-lipid regulates thromboinflammation in transplantation of human MSCs and hepatocytes
- 2016
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Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1742-7061 .- 1878-7568. ; 35, s. 194-205
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Tidskriftsartikel (refereegranskat)abstract
- Infusion of therapeutic cells into humans is associated with immune responses, including thromboinflammation, which result in a large loss of transplanted cells\ To address these problems, heparinization of the cell surfaces was achieved by a cell-surface modification technique using polyethylene glycol conjugated phospholipid (PEG-lipid) derivatives. A short heparin-binding peptide was conjugated to the PEG-lipid for immobilization of heparin conjugates on the surface of human mesenchymal stem cells (hMSCs) and human hepatocytes. Here three kinds of heparin-binding peptides were used for immobilizing heparin conjugates and examined for the antithrombogenic effects on the cell surface. The heparinized cells were incubated in human whole blood to evaluate their hemocompatibility by measuring blood parameters such as platelet count, coagulation markers, complement markers, and Factor Xa activity. We found that one of the heparin-binding peptides did not show cytotoxicity after the immobilization with heparin conjugates. The degree of binding of the heparin conjugates on the cell surface (analyzed by flow cytometer) depended on the ratio of the active peptide to control peptide. For both human MSCs and hepatocytes in whole-blood experiments, no platelet aggregation was seen in the heparin conjugate-immobilized cell group vs. the controls (non-coated cells or control peptide). Also, the levels of thrombin-antithrombin complex (TAT), C3a, and sC5b-9 were significantly lower than those of the controls, indicating a lower activation of coagulation and complement. Factor Xa analysis indicated that the heparin conjugate was still active on the cell surface at 24 h post-coating. It is possible to immobilize heparin conjugates onto hMSC and human hepatocyte surfaces and thereby protect the cell surfaces from damaging thromboinflammation. Statement of Signigficance We present a promising approach to enhance the biocompatibility of therapeutic cells. Here we used short peptide-conjugated PEG-lipid for cell surface modification and heparin conjugates for the coating of human hepatocytes and MSCs. We screened the short peptides to find higher affinity for heparinization of cell surface and performed hemocompatibility assay of heparinized human hepatocytes and human MSCs in human whole blood. Using heparin-binding peptide with higher affinity, not only coagulation activation but also complement activation was significantly suppressed. Thus, it was possible to protect human hepatocytes and human MSCs from the attack of thromboinflammatory activation, which can contribute to the improvement graft survival. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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