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P. J. Mulders

Publications and source records attributed to P. J. Mulders.

At least 91 records · Page 5Linked to original sources
arXiv1999

Beyond collinearity in the N(e,e'q) process

We discuss a few examples of structure functions for polarized, semi-inclusive scattering processes to show the richness of structure. Then we indicate how polarization and particle production can be used to study the quark and gluon structure of hadrons going further than the well-known parton densities and fragmentation functions. We also emphasize how single spin asymmetries in leptoproduction may shed light on explanations for single spin asymmetries in pion production in pp collissions.

nucl-th↗
arXiv1998

Spin physics in deep inelastic scattering

The problem of our understanding of the spin structure of the nucleon has been with us since the publication of the EMC measurements of the polarised structure function of the proton in 1987. In this talk a brief history of the subject is given followed by a review of the results presented in this workshop and the progress made to date.

hep-ph↗
arXiv1998

Spin physics with spin-0 hadrons

We discuss various azimuthal asymmetries in semi-inclusive DIS and e^+e^- ==> h1 h2 X which involve chiral odd quantities like the transversity distribution h_1 and a fragmentation function H_1^\perp. For the fragmentation described by H_1^\perp azimuthal angular dependence has to be measured, but no polarization vector of a final state hadron. We present first results on asymmetries including the electroweak currents in one-hadron inclusive DIS.

hep-ph↗
arXiv1998

Single spin asymmetries in semi-inclusive deep inelastic scattering

In this talk I want to illustrate the many possibilities for studying the structure of hadrons in hard scattering processes by giving a number of examples involving increasing complexity in the demands for particle polarization, particle identification or polarimetry. In particular the single spin asymmetries will be discussed. The measurements discussed in this talk are restricted to lepton-hadron scattering, but can be found in various other hard processes such as Drell-Yan scattering or $e^+e^-$-annihilation.

hep-ph↗
arXiv1998

Leading asymmetries in two-hadron production in e^+e^- annihilation at the Z pole

We present the leading unpolarized and single spin asymmetries in inclusive two-hadron production in electron-positron annihilation at the Z pole. The azimuthal dependence in the unpolarized differential cross section of almost back-to-back hadrons is a leading cos(2 phi) asymmetry, which arises solely due to the intrinsic transverse momenta of the quarks. An extensive discussion on how to measure this asymmetry and the accompanying time-reversal odd fragmentation functions is given. A simple estimate indicates that the asymmetry could be of the order of a percent.

hep-ph↗
arXiv1997

Time-reversal odd distribution functions in leptoproduction

We consider the various asymmetries, notably single spin asymmetries, that appear in leptoproduction as a consequence of the presence of time-reversal odd distribution functions. This could facilitate experimental searches for time-reversal odd phenomena.

hep-ph↗
arXiv1997

Single spin asymmetries in the Drell-Yan process

We discuss single transverse spin asymmetries in the Drell-Yan process originating from so-called gluonic poles in twist-three hadronic matrix elements, as first considered by Qiu and Sterman. Even though time-reversal invariance is not broken, the effects of such poles cannot be distinguished from those of time-reversal odd distribution functions. We show the connection between gluonic poles and large distance gluon fields, in particular we focus on boundary conditions. We identify the possible single spin asymmetries in the Drell-Yan process.

hep-ph↗
arXiv1997

Intrinsic transverse momentum in hard processes

In this contribution I discuss transverse momentum dependent quark distributions and their operator structure. Some of the experimental signatures, in particular in Drell-Yan scattering, are given.

hep-ph↗
arXiv1997

Single spin asymmetries from a gluonic background in the Drell-Yan process

We discuss the effects of so-called gluonic poles in twist-three hadronic matrix elements, as first considered by Qiu and Sterman, in the Drell-Yan process. These effects cannot be distinguished from those of time-reversal odd distribution functions, although time-reversal invariance is not broken by the presence of gluonic poles. Both gluonic poles and time-reversal odd distribution functions can lead to the same single spin asymmetries. We explicitly show the connection between gluonic poles and large distance gluon fields, identify the possible single spin asymmetries in the Drell-Yan process and discuss the role of intrinsic transverse momentum of the partons.

hep-ph↗
arXiv1997

Spin structure functions in leptoproduction

We discuss a few examples of structure functions for polarized, semi-inclusive scattering processes to show the richness of structure. Then we indicate how polarization and particle production can be used to study the quark and gluon structure of hadrons going further than the well-known parton densities and fragmentation functions.

hep-ph↗
arXiv1997

Distribution and fragmentation functions in a spectator model

Quark distribution and spectator functions are estimated in a diquark spectator model. The representation of the functions in terms of non-local operators together with the rather simple model allow estimates for the yet experimentally undetermined functions, like the polarized fragmentation functions or higher twist functions.

hep-ph↗
arXiv1997

Asymmetries in polarized hadron production in e^+e^- annihilation up to order 1/Q

We present the results of the tree-level calculation of inclusive two-hadron production in electron-positron annihilation via one photon up to subleading order in 1/Q. We consider the situation where the two hadrons belong to different, back-to-back jets. We include polarization of the produced hadrons and discuss azimuthal dependences of asymmetries. New asymmetries are found, in particular there is a leading cos(2 phi) asymmetry, which is even present when hadron polarization is absent, since it arises solely due to the intrinsic transverse momenta of the quarks.

hep-ph↗
arXiv1997

Probing transverse quark polarization via azimuthal asymmetries in leptoproduction

We consider the leading order result for polarized leptoproduction, putting emphasis on transverse momentum dependent effects appearing in azimuthal asymmetries. Measurements of weighted cross sections enable extraction of the distribution of transversely polarized quarks. We focus on the distribution in a longitudinally polarized hadron and estimate the expected asymmetries in leptoproduction.

hep-ph↗
arXiv1997

Modelling quark distribution and fragmentation functions

The representation of quark distribution and fragmentation functions in terms of non-local operators is combined with a simple spectator model. This allows us to estimate these functions for the nucleon and the pion ensuring correct crossing and support properties. We give estimates for the unpolarized functions as well as for the polarized ones and for subleading (higher twist) functions. Furthermore we can study several relations that are consequences of Lorentz invariance and of C, P, and T invariance of the strong interactions.

hep-ph↗
arXiv1997

Quark Distribution Functions in a Diquark Spectator Model

The representation of quark distribution functions in terms of nonlocal operators is combined with a simple diquark spectator model. This allows us to estimate these functions for the nucleon ensuring correct crossing and support properties.

hep-ph↗
arXiv1996

Prospects for spin physics in semi-inclusive processes

I discuss inclusive and semi-inclusive lepton-hadron scattering emphasizing the importance of polarization in order to study various single or double spin asymmetries and the importance of particle identification and angular resolution in the dectection of final state particles to study azimuthal asymmetries. The observables obtained in this way enable a detailed study of quark and gluon correlations in hadrons.

nucl-th↗
arXiv1996

Time reversal odd fragmentation functions

The combination of transverse momentum and polarization effects in hard scattering processes, e.g polarized deep-inelastic leptoproduction, results in a rich variety of information on the hadronic structure. This information is encoded in a correspondingly large number of functions depending on both, longitudinal fractional momenta $x$ and transverse momenta $p_T$. Integration over transverse momenta establishes the connection to the usual distribution and fragmentation functions. Constraints from hermiticity and invariance under parity operation induce some relations between different functions. One specific aspect of the information on the hadronic structure is the appearance of {\em time reversal odd} fragmentation functions due to the non-applicability of time-reversal invariance for the hadronization of a quark. {\em T-odd} fragmentation functions are experimentally accessible via the measurement of, for instance, asymmetries in semi-inclusive leptoproduction.

hep-ph↗