Quark Fragmentation Functions Research Articles

Gluon fragmentation functions from quark jets

The analysis of events with a fixed, different from unity, fraction of energy flowing into a solid angle ΔΩ can be used to extract the probability functions related to the scaling violations of deep inelastic scattering. One can obtain from the study of a quark jet, both the gluon and the quark fragmentation functions into hadrons.

The transverse momentum dependence of quark fragmentation functions from cascade models

A covariant generalization of the one-dimensional cascade model for quark fragmentation functions is presented, so as to include the transverse momentum behaviour and the possibility to produce different particles at different vertices along the chain. In the scaling limit the exact solution is given, if the primordial function is of the type αz α−1·T(p T ). For the more general case of factorizing primordial functions an analytic expression for the seagull effect is derived, which turns out to be independent of the functionT(p T ).

Experimental Properties of Neutrino-Induced Jets

We analyze a sample of about 2000 charged-current neutrino-proton interactions with neutrino energy greater than 10 GeV produced in the 15 ft. hydrogen bubble chamber at Fermilab using a broad band neutrino beam. We study the details of the hadrons produced and find generally good agreement with the quark-parton model and present parametrizations of quark fragmentation (D) functions. The D functions are found to be independent of Q2 and W (total hadronic mass) for W > 4 GeV, in agreement with the model. The height of the rapidity plateau in the quark (current) fragmentation region is compared to that of the di-quark (target) fragmentation region and the two are found to agree. The mean transverse momentum PT of the hadrons is studied for its Q2 and Feynman-X dependence. We find a sizeable increase of ⟨PT2⟩ with Feynman-X which agrees, however, with our longitudinal phase space model. We find no statistically significant dependent of ⟨PT2⟩ on Q2, up to Q2 = 64 GeV2, although the highest momentum hadrons are consistent with a mild Q2 dependence. There are no effects of high "primordial" parton momentum apparent in the data. No effects of gluon radiation are found in the Q2 dependence of the phase space density of particle production near zero c.m. rapidity.

Finite corrections to quark fragmentation functions in perturbative QCD

The finite corrections of order α s in perturbative QCD to the cross-sections for semi-inclusive hadron production from deep inelastic leptonhadron scattering and electron-positron annihilation are calculated. We define the effective quark fragmentation functions viae + e − → hadron +X including the finite terms in order to estimate these corrections for the reactions lepton + hadron → lepton + hadron + anything. Contrary to the leading term the next-to-leading order term does not factorize into parts depending on the target and the fragment, respectively. For the processese +p →e + π± +X andv +p →μ − + π± +X the finite corrections of order α s turn out to be at most 20% in the range of momenta covered by present experiments.

Experimental study of hadrons produced in high-energy charged-current neutrino-proton interactions

We analyze a sample of about 2000 charged-current neutrino-proton interactions with neutrino energy greater than 10 GeV produced in the 15-ft hydrogen bubble chamber at Fermilab using a broad-band neutrino beam. We study the details of the hadrons produced and find generally good agreement with the quark-parton model and present parametrizations of quark fragmentation ($D$) functions. The $D$ functions are found to be independent of ${Q}^{2}$ and $W$ (total hadronic mass) for $Wg4$ GeV, in agreement with the model. The height of the rapidity plateau in the quark (current) fragmentation region is compared to that of the diquark (target) fragmentation region and the two are found to agree. Detailed charge-correlation data are presented and compared to the Field-Feynman model of the $D$ functions, and also to a longitudinal-phase-space model, and are found to disagree with both. The mean transverse momentum ${P}_{T}$ of the hadrons is studied for its ${Q}^{2}$ and Feynman-$X$ dependence. We find a sizeable increase of $〈{{P}_{T}}^{2}〉$ with Feynman $X$ which agrees, however, with our longitudinal-phase-space model. We find no statistically significant dependence of $〈{{P}_{T}}^{2}〉$ on ${Q}^{2}$, up to ${Q}^{2}=64$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$, although the highest-momentum hadrons are consistent with a mild ${Q}^{2}$ dependence. The azimuthal angular distribution of the highest-momentum hadrons in high-${Q}^{2}$ events is examined for evidence of anisotropy of the type that has been predicted for effects of gluon radiation.

Jets in small- pT hadronic collisions, universality of quark fragmentation, and rising rapidity plateaus

We consider a two-rapidity-chain fragmentation model for small- p T hadronic collisions based on the dual topological approach. This model, when supplemented by the universality of quark fragmentation functions, accounts for the energy and x-dependence of all available one particle inclusive data. The model provides a novel explanation for the rise of hadronic plateaus with energy.

Monte Carlo approach to multiparticle production in a quark-parton model. III.e+e−annihilation and quark fragmentation functions

A Monte Carlo quark-parton model of multiparticle production in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation is presented. The model is based on the assumption that the polarization cloud in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation behaves in a similar way as the parton system near ${y}^{*}\ensuremath{\approx}0$ in hadronic collisions. The model is constructed in a close analogy with our previous work on multiple production in hadron collisions. With all the parameters fixed by data on hadron collisions the model gives reasonable results for ${e}^{+}{e}^{\ensuremath{-}}$ annihilation. Quark fragmentation functions are extracted from our results on particle production in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation. Our results for fragmentation of quarks to mesons are similar to those obtained recently by Field and Feynman in a different model. Scale breaking of quark fragmentation functions following from our model is discussed. Predictions for fragmentation of quarks to baryons are presented.

Q2 dependence of quark and gluon fragmentation functions in a parton picture based on QCD

The Q 2 dependence of quark and gluon fragmentation functions is investigated within the framework of a parton model based on Quantum Chromodynamics (QCD). Contributions from gluon fragmentation become important through the mixing effects at large Q 2. The Q 2-dependent fragmentation functions are shown to satisfy the momentum conservation constraints.

On the fragmentation functions of heavy quarks into hadrons

An explicit form for the charmed quark fragmentation function D C c( z) into hadrons has been obtained with the help of the “reciprocity relation” and the c-quark distribution function in charmed mesons (the function calculated in terms of the Kuti-Weisskopf model). D C c( z) turns out to peak mainly at z close to 1. The analysis of new data on muon pair production in neutrino reactions points to such a behaviour of the D C c( z) function. The obtained fragmentation function, contrary to those, used earlier, leads to a charmed particle (average) multiplicity in e +e −-annihilation independent of energy.

Detailed quantum-chromodynamic predictions for high-pTprocesses

High-${p}_{T}$ single-particle inclusive cross section calculations are presented for the CERN ISR and ISABELLE energy ranges, taking into account all lowest-order hard-scattering subprocesses required by quantum chromodynamics (QCD). The input quark and gluon distribution and fragmentation functions were determined from analyses of deep-inelastic lepton data and were subject to various theoretical constraints such as sum rules and SU(3) symmetry. We thoroughly discuss the effects of the individual contributions from fermionic and gluonic subprocesses, as well as those effects stemming from QCD scaling violations in parton distributions and/or fragmentation functions. In particular, the inclusion of the large elastic gluon-gluon and gluon-quark scattering terms has a profound effect on both the normalization and the ${p}_{T}$ dependence of the predictions. The ${p}_{T}$ and $\ensuremath{\theta}$ dependences of single-${\ensuremath{\pi}}^{0}$ production are shown to be in good agreement with available data in the region ${p}_{T}\ensuremath{\gtrsim}4.5$ GeV/c and $\sqrt{s}\ensuremath{\gtrsim}50$ GeV. In addition, we predict and discuss various ratios for inclusive single-particle production of ${\ensuremath{\pi}}^{+}$, ${\ensuremath{\pi}}^{\ensuremath{-}}$, ${K}^{+}$, and ${K}^{\ensuremath{-}}$, which also turn out to be in excellent agreement with presently available experiments.

Light-quark and heavy-quark fragmentation functions

We discuss the shape of the leading-fragment momentum distribution function in light- and heavy-quark fragmentation. The features of the u-quark and s-quark leading fragmentation functions extrapolated to higher quark masses lead to the conclusion that as the quark mass increases the average momentum 〈 z〉 carried by the heavy meson increases and the fragmentation function becomes narrower. This result fully supports Bjorken's proposal for heavy quark decay. Predictions are given for the shape of the c, b, … quark fragmentation functions.

Relations for hadron pairs at largepTin the elastic quark-quark scattering model

Relations between cross sections for producing hadrons pairs with large transverse momenta are presented. They follow from the isospin and charge-conjugation properties of the elastic quark-quark scattering model. These relations are independent of any specific parametrization for the quark-distribution and quark-fragmentation functions and of any specific form for the hard-scattering cross section.

Quark fragmentation function in inclusive hadron scattering: Universality

We extract from 16-GeV/c and 32-GeV/c data on ${K}^{+}p\ensuremath{\rightarrow}{K}^{0}X$ and ${K}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\overline{K}}^{0}X$ the strange-quark fragmentation function ${D}_{s}^{\overline{\mathrm{k}}0}(x)$. We show that it has the right properties expected for such a function. This is in agreement with predictions on the universality of quark fragmentation functions obtained in two-dimensional gauge models, and also with what is suggested in some dual models.

On the Q2 dependence of parton fragmentation functions

The Q2 dependences of parton fragmentation functions are calculated using lowest-order quantum chromodynamics (QCD). The resulting scaling deviations have a simple intuitive form when a suitable valence-sea decomposition is employed for the quark fragmentation functions.

A quark parton model for hadronic fragmentation distributions

The one-particle inclusive distributions in the fragmentation regions in hadronic interactions are described in a parameter free way by a simple additative quark parton model by means of the quark fragmentation functions measured in leptoproduction. We interpret the result so that while the main interaction in hadronic collisions is due to the wee partons almost all the momenta is carried by one of the valence quarks yielding fragmentation region distributions similar to the ones in leptoproduction.

Test of the Quark Parton Model with Data from Electroproduction of Pions

We have measured the relative cross sections of ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ electroproduction from protons and neutrons, and combined them in a way which permits a new, detailed comparison with the quark parton model of the nucleon. We confirm the expected behavior with $\frac{1}{\ensuremath{\omega}}$ of the quark charge ratio and the quark fragmentation function.

A simple model for the quark fragmentation functions seen in deep inelastic processes

Using some simple assumptions, we present in this paper a calculation of the quark fragmentation functions seen in deep inelastic processes. The results provide evidence for the conjecture that both jets seen in high p⊥ reactions at the ISR stem from similar parents. The calculated functions are in excellent agreement with the inclusive distributions seen in νp and νp scattering, and in particular explain the puzzling presence of leading π −′s from the fragmentation of a leading up quark. The results are also in agreement with the charge ratios extracted from deep inelastic electron scattering.

On the Determination of the Ratios of Quark Fragmentation Functions by Inclusive Electro-Pion-Production Experiments

On the Determination of the Ratios of Quark Fragmentation Functions by Inclusive Electro-Pion-Production Experiments

On the Determination of the Ratios of Quark Fragmentation Functions in Inclusive Electroproduction

On the Determination of the Ratios of Quark Fragmentation Functions in Inclusive Electroproduction

Dynamical connections between quark fragmentation functions

Assuming that the quark kicked by a virtual photon emits pions one by one, integral equations connecting the fragmentation functions D u π + ( z) and D u π − ( z) are obtained. It is shown that they have a plateau the height of which can be determined from the multiplicity difference N p π + ( z) − N p π − ( z). Comparison with experiment is made.