共查询到20条相似文献,搜索用时 15 毫秒
1.
An explicit form for the charmed quark fragmentation function DCc(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). DCc(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 DCc(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. 相似文献
2.
L. Van Hove 《Zeitschrift fur Physik C Particles and Fields》1981,9(2):145-154
Following earlier theoretical and experimental work (Kalinowski et al. [6], Bourquin et al. [7]), baryon production by fragmentation of incident protons in high energy hadron collisions is re-investigated in terms of a fragmentation-recombination mechanism similar to a model proposed by Fukuda and Iso [4]. The multiplicitiesn f (B) for the various types of baryonsB produced in proton fragmentation are expressed in terms of the probabilitiesa i fori=0, ..., 3 valence quarks of the incident proton to emerge in the baryonB and 3?i to emerge in mesons (following [7] we suppose that antibaryon production is mostly due to baryon-antibaryon pair production by a mechanism of non-fragmentation type, and this is taken into account in deducingn f (B) from baryon and antibaryon multiplicity data). The positivity of thea i is found to impose remarkably narrow constraints on then f (B) for (meta)stableB, and we find the data to satisfy these constraints. We show furthermore that the data are compatible with uncorrelated behaviour of the valence quarks of the incident proton, each of them having a probability ? 0.6 to emerge in the fragmentation baryonB, and a probability ? 0.4 to emerge in a meson. We also briefly discuss the relation of our analysis to previous work on the recombination model of proton fragmentation and its possible extension to meson fragmentation. 相似文献
3.
The valence part of the quark fragmentation function resulting in the octet of baryons together with their spin structure are parametrised, using a model for the hadronisation and the available experimental data on baryon products in e+e? annihilation and μp deep inelastic scattering. Spin correlations are predicted. 相似文献
4.
P. Exner 《Czechoslovak Journal of Physics》1984,34(11):1145-1149
5.
J. L. Cortes B. Pire J. P. Ralston 《Zeitschrift fur Physik C Particles and Fields》1992,55(3):409-416
The transverse spin polarization distribution of quarks in a proton contributes at leading twist to the angular distribution of lepton pair production in doubly polarized proton-proton collisions. Although this distribution is straightforward to define in the QCD-improved parton model and represents a fundamental quark degree of freedom, it has never been measured. Moreover, deeply inelastic electroproduction experiments are only sensitive to this distribution at the higher twist level, and then mix this contribution with others, including the one coming from multiparton initial states. Reviewing this, we conclude that the Drell-Yan process is the best way to measure the quark transverse spin polarization distribution.Unité propre du CNRS 相似文献
6.
A model is proposed describing main features of a behaviour of the fragmentation cross sections for relativistic ions including their relative yields. The reaction is assumed to proceed in two stages: At the first one the ion is excited by the peripheral collision with a nucleus, at the second one it decays statistically in flight with emitting a fragment. A strong analogy is demonstrated for the process with the corresponding reactions of nonrelativistic ions. 相似文献
7.
Meson production at low transverse momentum in the fragmentation region (x>0.5) in pp collisions is considered in the context of the parton model. It is shown that the quark decay process is unimportant compared to the quark-antiquark recombination process. The calculated results of the model agree very well with the experimental data on the longitudinal momentum distributions of π± and K± in both the shapes and the normalizations. 相似文献
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Mehmet Akif Cirit 《Physics letters. [Part B]》1980,94(2):242-244
Using the Kuti-Weisskopf model we calculate dressed quark fragmentation function from proton. We show that the fragmentation spectrum of such a quark correctly fits to the fast meson spectrum. 相似文献
10.
Prabir Pal Padmanabha Dasgupta Nanda Dasgupta 《Zeitschrift fur Physik C Particles and Fields》1983,17(3):243-248
Low-P T production off deuteron in the fragmentation region is studied on the basis of a six-quark picture of deuteron. It is argued that all the six valence quarks participate equally in the hadronization processes associated with meson and baryon productions. Thex-distribution of the inclusive cross sections is studied in the framework of a quark recombination model. Fit with experimental data leads to a determination of the valence and sea quark distributions in deuteron. Probabilistic arguments applied to a general recombination picture are shown to lead to some experimentally verifiable constraints on baryon multiplicities. Possibilities of determining the various recombination probabilities are also discussed. 相似文献
11.
《Nuclear Physics B》1995,445(1):3-21
Deep inelastic scattering (DIS) events, selected from 1993 data taken by the H1 experiment at HERA, are studied in the Breit frame of reference. The fragmentation function of the quark is compared with those of e+e− data. It is shown that certain aspects of the quarks emerging from within the proton in e−p interactions are essentially the same as those of quarks pair-created from the vacuum in e+e− annihilation. The measured area, peak position and width of the fragmentation function show that the kinematic evolution variable, equivalent to the e+e− squared centre of mass energy, is in the Breit frame the invariant square of the four-momentum transfer. We comment on the extent to which we have evidence for coherence effects in pArton showers. 相似文献
12.
The first moments of the polarized valence parton distribution functions truncated to the wide Bjorken x region 0.004 < x < 0.7 are directly (without any fitting procedure) extracted in NLO QCD from the combined COMPASS and HERMES semi-inclusive
deep inelastic scattering data. Applying the proposed original procedure to these results, we estimate the contributions of
light sea quarks to the proton spin, which occur just zero within the errors. 相似文献
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《Physics letters. [Part B]》1998,440(3-4)
The mechanism of baryon-anti-baryon pair production in e+e− annihilation into hadrons has been studied using the TOPAZ detector at the TRISTAN e+e− collider at an average center-of-mass energy of 58 GeV. The distributions of various
correlations were compared with two prominent models: the cluster-fragmentation model and the string-fragmentation model. We rejected the cluster-fragmentation model at the 90% C.L. Furthermore, in the context of the string-fragmentation model, we favor the “popcorn” model, rejecting the “diquark” model, where a diquark is considered to be a fundamental entity, at the 95% C.L. 相似文献
15.
New data on the x-dependence of the ratio of down to up quarks in the proton are presented from neutrino and antineutrino experiments using the Fermilab 15-foot bubble chamber filled with hydrogen. The new data are in good agreement with existing data from electron scattering experiments performed at SLAC but are not accurate enough at large x to discriminate between the QCD prediction and a (1 ? x) behavior as x → 1. 相似文献
16.
We show in the context of an effective Lagrangian for baryons and pseudoscalar mesons how derivative couplings to Goldstone bosons modify the axial charges. Applying these considerations to constituent quarks we relate a modification of their axialU(1) charges to their internal structure which is represented here in term of a flavour singletφ 0 field attached to quarks. We end up with aSU (6)-type constituent quark model which describes the experimental results very well. 相似文献
17.
M. Bourquin R. M. Brown Y. Chatelus J. C. Chollet A. Degré D. Froidevaux A. R. Fyfe J. -M. Gaillard C. N. P. Gee W. M. Gibson P. Igo-Kemenes P. W. Jeffreys B. Merkel R. Morand H. Plothow J. -P. Repellin B. J. Saunders G. Sauvage B. Schiby H. W. Siebert V. J. Smith K. -P. Streit R. Strub J. J. Thresher S. N. Tovey 《Zeitschrift fur Physik C Particles and Fields》1980,5(4):275-283
Measurements of the production inp-BeO collisions of charged baryons and antibaryons with strangeness between ?3 and +3 at \(\sqrt s = 21.2GeV\) x=0.48, andp T =600MeV/c are reported. The experimental results can be interpreted within the framework of a simple proton fragmentation-recombination model. 相似文献
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Boris Kopeliovich Bogdan Povh Irina Potashnikova 《Zeitschrift fur Physik C Particles and Fields》1996,73(1):125-131
Experiments at HERA looking for deep-inelastic electroproduction of neutrons in the proton fragmentation region are in progress. They are aimed to measure the pion structure function at small Bjorken x. The important condition for such a study is to establish under what kinematical conditions the dominance of the pion-pole graph in the process is guaranteed. We analyse other sources of the leading neutron, in order to figure out the kinematical region where the one-pion exchange dominates. 相似文献