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  • 1
    Electronic Resource
    Electronic Resource
    Baryon trajectories revisited (1983)
    Springer
    The European physical journal 18 (1983), S. 47-52 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Various properties of baryon trajectories are re-examined in the light of the latest data: in particular we study trajectory assignments of the 1982 baryon resonance data and evaluate effective trajectories for backward πN scattering incorporating FNAL data. We find that all of the information is consistent with trajectories linear inu, withF/D ratios constant along the trajectories and parity doublets absent. We find that exchange degeneracy (EXD) is good for Λ and Σ trajectories and residues and shed some qualitative light on the systematics of EXD breaking.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01571705
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    LargeP T photoproduction in the hard scattering expansion (1982)
    Springer
    The European physical journal 14 (1982), S. 65-77 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Largep T photoproduction is studied in the hard scattering expansion, including both three- and four-jet processes. The higher twist corrections (∝p T −6 andp T −8 ) to the basic QCD hard scattering process (∝p T −4 ) are estimated using the constituent interchange model and the various terms compared. Both single jet inclusive cross sections and single particle inclusive π0 cross sections are evaluated, the latter using scale violating fragmentation functions. We find that the higher twist terms are significant at present energies, particularly for three-jet events, though the four-jet anomalous photon contribution can be measured. Three-jet QCD processes require considerably higher energies to provide a significant contribution to the cross section. Methods of separating the different processes experimentally are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01547965
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A phenomenological analysis of the photon structure functionF 2 γ (x, Q 2 ) (1991)
    Springer
    The European physical journal 51 (1991), S. 241-257 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new method of analysis of the photon structure functionF 2 γ (x, Q 2 ) is presented. It is a generalisation of Rossi's ansatz for generating regularised solutions of the inhomogeneous Altarelli-Parisi equations which enables initial conditions in theQ 2 evolution to be incorporated. Its equivalence to the normal solution is demonstrated. It is applied in a phenomenological analysis of the data on the structure functionF 2 γ . It is found that the recent TPCF 2 γ data in the range 0.3〈Q 2〈1.6 GeV2 cannot be used as a starting point for a perturbative QCD analysis, despite being well described by the vector meson dominance model (VMD) and exhibiting scaling. This conclusion invalidates previous discussions of the effect of the regularisation of the asymptotic point-like QCD prediction on the sensitivity ofF 2 γ to the QCD mass scale Λ, because they incorporated VMD assumptions in the perturbative region. A perturbative QCD analysis using higherQ 2 data as a starting point is presented but here the initial conditions necessarily involve more assumptions, and starting the evolution at a higherQ 2 involves an inevitable decrease in the sensitivity to Λ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01475792
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Exchange ofA 1 andZ 1 (J PC=2−−) mesons in charged pion photoproduction (1981)
    Springer
    The European physical journal 10 (1981), S. 263-266 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Finite energy sum rules are evaluated for the amplitudes corresponding to the exchange of theA 1 and its exchange degenerate partner, theZ 1 (J PC=2−−), in charged pion photoproduction. Both sum rules are roughly compatible with theoretical estimates of these exchanges, and a definiteA 1 signal found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01549734
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    The parton distribution functions of the photon and the structure functionF 2 γ (x, Q 2) (1992)
    Springer
    The European physical journal 56 (1992), S. 307-314 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present new parametrisations of the parton distribution functions of the photon including the first parametrisation in next-to-leading order QCD. We take into account some recent theoretical considerations pertaining to the gluon content of the photon,g γ. We argue that if an evolution is started at very lowQ 2 and a fit to allF 2 γ data performed with no constraints on the gluon distribution, then physically unreasonable gluon distributions may result. Our results support recent indications thatQ 0 2 ≤1 GeV2 is too low a value from which to start a perturbative evolution. Starting our evolution atQ 0 2 =5.3 GeV2, we evolve up inQ 2 using a modified version of Rossi's Ansatz. The limited lever arm inQ 2 leads to limited sensitivity to the QCD scale parameter Λ, though there is a preference for low values in the 0.1–0.2 GeV range. We also present new parametrisations of the singular asymptotic quark and gluon distribution functions of the photon which we believe are more accurate than those in current use.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01555529
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  • 6
    Electronic Resource
    Electronic Resource
    Largep T prompt photon production at HERA (1994)
    Springer
    The European physical journal 63 (1994), S. 581-588 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We examine the possibility of using direct photon production at HERA as a means of obtaining information about the photon structure and fragmentation functions. Estimates of the cross section for inclusive prompt photon production at theep collider HERA are made completely in next-to-leading order QCD. Using parton distributions for the photon evolved in next-to-leading order QCD for the first time, we show that theO(α s ) corrections to the processes involving these functions are significant in the regions where they dominate. This can have important consequences for the possibility of measuring the gluon content of the photon using these processes at HERA. Moreover, we show that it may not be straightforward to separate the various contributions to the cross section in theep lab frame.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01557624
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    Paper (German National Licenses)
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