Proton Fragmentation Region Research Articles

TRIPLE REGGE ANALYSIS AND $K\bar{K}$ OFF-SHELL INTERACTIONS FROM $p\mathop{\to} \limits^{K^-}\Lambda$ AT 110 GeV/c

A study of Λ production has been made in the proton fragmentation region from K−p interactions at 110 GeV/c. From a simultaneous fit to the missing mass distributions and the inclusive Λ production cross section with P tab ≥10 GeV/c , the intercept of the strange meson trajectory is determined to be ≃−0.15. The contribution of the Pomeron is found to be dominant at the [Formula: see text] vertex in 110 GeV/c K−p interactions. The charged multiplicities and moments from off-shell [Formula: see text] interactions have been studied as a function of M2, the c.m. energy square of the virtual [Formula: see text] system.

Proton fragmentation into pions and pion systems inK − p interactions at 110 GeV/c and comparison to model predictions

Thex dependence of single pion and multi pion production is studied in the proton fragmentation region ofK − p interactions at 110 GeV/c. A recombination and a string fragmentation model have been tuned to describe the single particle distributions well and are then used to describe two and three pion production when one particle or particle system is selected in a given interval of longitudinal momentum. The string fragmentation model reproduces most of the observed distributions correctly, but fails in the case of multi π+ production.

Constituent-quark model for production of forward hyperons in proton-nucleus collisions

Cross sections for the inclusive reactions $p+A\ensuremath{\rightarrow}\ensuremath{\Lambda} or {\ensuremath{\Xi}}^{0}+\mathrm{anything}$ in the proton fragmentation region are analyzed in terms of the constituent-quark model. Contributions from the leading single quarks and leading diquarks are determined separately and the results are interpreted in terms of the quark-fragmentation-recombination picture. It is strongly suggested that recombination of leading quarks with a heavy (anti)quark ($s, \overline{s}, c, \overline{c}, \dots{}$)) or a pair of (anti)quarks from the central sea is strongly suppressed compared to recombination with a single light (anti)quark ($u, \overline{u}, d, or \overline{d}$) from the sea.

Study of longitudinal correlations between pions from fragmentation processes inK − p interactions at 32 GeV/c

Longitudinal correlations between pions inclusively produced in the target and beam fragmentation regions are studied in aK−p bubble chamber experiment at 32 GeV/c with a sensitivity of about 6.7 ev/μb. It was found that the\({{\tilde x_2 = x_2 } \mathord{\left/ {\vphantom {{\tilde x_2 = x_2 } {(1 - \left| {x_1 } \right|)}}} \right. \kern-\nulldelimiterspace} {(1 - \left| {x_1 } \right|)}}\) distributions of charged pions with momentum fraction in the proton hemisphere with respect to a charged “trigger” pion with momentum fraction x1 do not show scaling, that those of the associated π1/π2 do not compare toK+p interactions and give indications for quark annihilation. The invariant two- and three pion longitudinal C.M. distributions show significant deviations from the naive quark recombination picture. Distinct long-range correlations observed between π−s from the proton fragmentation region and π+s from theK− fragmentation region could imply contributions from quark exchange or quark annihilation mechanisms inK−p interactions at 32 GeV/c.

Proton fragmentation in deep inelastic scattering: A treatment in the valon-recombination model

A detailed analysis is presented for the fragmentation of a proton in deep inelastic scattering. The valon-recombination model is used as a framework for the description of proton structure on the one hand and of the hadronization of quarks on the other. No arbitrary parmeters are involved in the treatment. Perturbative QCD is used to calculate the effects of scaling violation. Predictions are made for the pion inclusive distributions in the proton fragmentation region for semi-inclusive reactions induced by muon, neutrino and antineutrino. The results are determined for both τ+ and τ− at various Feynmanx for different values of Bjorkenx andQ2. Resonance contribution in the final state has also been taken into account.

A critical analysis of inclusive resonance and background production in the quark recombination model

Recent measurements of rising ratios of resonance to back-ground with Feynmanx of various particle combinations in inclusive reactions seem to point against the quark recombination model. We show, for the proton fragmentation region and for the case ρ0/(π+π-) that a) ρ0-resonance production is well reproduced by the recombination model up tox ≅ — 0.2,b) for the (π+π-) nonresonant background due to kinematical reasons one of the pions is slow in most cases forxπ+π-≳ 0.8 and the recombination model-suited only for the fragmentation region ofboth pions- cannot be applied to such a configuration, c) for a reasonable empirical extrapolation of the joint two-pion distribution to lowx of the background pions the rising resonance/background ratio can be Well reproduced. We conclude that the data are hardly suited to test the recombination model.

Study of inclusive production of ?� and protons in $$\bar p$$ p interactions at 32 GeV/c

Results are presented on the inclusive production of π± mesons and protons in\(\bar p\)p interactions at an incident antiproton momentum of 32 GeV/c in the MIRABELLE bubble chamber, based on a sample of 55,000 inelastic events. The spectra of π+(π−) andp(\(\bar p\)) are separated in the whole kinematically admitted region of phase space by a statistical method. The semi-inclusive and inclusive cross sections and the main average characteristics of π andp production are calculated. The invariant differential cross sections are studied as functions of the Fevnman scaling variablex, the rapidity and the transverse momentum. Thex distribution of π± mesons in the proton fragmentation region does not show any significant contribution from quark exchange or annihilation processes. A possible contribution of hard quark scattering on mesons or baryons is observed for large transverse momenta.

Diquark fragmentation functions in hadron-nucleon interactions at 19 GeV/c and other energies

New data on pion production in pn interactions at 19 GeV/c are used, together with earlier data on pion production in pn π{su+}n at at other energies, to determine the diquark fragmentation functions\(\mathop D\nolimits_{dd}^{\pi \pm } ( = \mathop D\nolimits_{uu}^{\pi \mp } )\) andDudπ in the neutron and proton fragmentation regions. Typical high-energy data on pion production in pp interactions are also considered. The unfavoured fragmentation function\(\mathop D\nolimits_{dd}^{\pi \pm } (x)\) is found to be much smaller than the favoured fragmentation function\(\mathop D\nolimits_{dd}^{\pi \_} (x)\) and to have a steeperx-dependence. The diquark fragmentation functions agree very well with those from\(\nu (\bar \nu ) - proton\) interaction as expected from quark parton models.

?+/?? Ratio and two particle production in Proton's fragmentation region by Monte Carlo simulation

Hadron jet at lowp T is generated by Monte Carlo method using several models including our quark cascade model in which the recombination mechanism is taken into account. The predicted results from those models on π+/π− ratio,K + /K − ratio, π± meson spectra and π+/π− ratio under π± meson and Λ particle trigger, ratio between invariant two particle cross-section (p→π + /π − )/(p→π − /π − are compared with the experimental data. The effects of the asymmetric initialu- andd-quark distributions the scaling and its violation of particle spectra and particle ratios under the other particle trigger are discussed. Predictions from our recombination model fit to the experimental data fairly well.

Study of longitudinal distributions in the fragmentation regions, using the quark-parton model, in K −p interactions at 70 GeV/ c

The study of π ±, π 0, K 0 and Λ production in the fragmentation regions (| x|0.2) of K −p interactions at 70 GeV/ c shows that the x-dependence of each invariant cross section is well described by the power law (1−| x|) n suggested by the dimensional counting rule. Furthermore, pion production is found, both in K − and proton fragmentation regions, to be very similar to their production in ν( ν) p interactions as expected from quark-parton models. The quark and diquark fragmentation functions D u π , D uu π and D ud π are extracted from our data.

Target proton fragmentation and two-reggeon final state

Data on π−, π+, K+ and p production by hadrons in the target proton fragmentation region are analysed in terms of the hadronhadron to reggeon-reggeon process. The difference in the energy dependence of the cross-sections is explained successfully.

Inclusive Spectra and Two Particle Correlations in Small pT Hadron Jets from Quark Cascade Model with Recombination Mechanism

Inclusive single particle spectra, charge and momentum flows, ratios of pion pairs produced in kaon's and pion's fragmentation regions, two meson correlation functions in meson's and proton's fragmentation regions and π+ meson spectrum in proton's fragmentation region under π± meson trigger are calculated using a quark cascade model in which the recombination mechanism is taken into account and momentum and quantum numbers are conserved automatically. Both Monte Carlo simulation and analytical calculation are performed to give these predictions.

Baryon production through diquark-quark recombination at the proton fragmentation region

Baryon production through diquark-quark recombination at the proton fragmentation region

Inclusive production of Σ+ and Σ− in K −p interactions at 10 and 16 GeV/ c and comparison with Λ production

The inclusive production of Σ + and Σ − hyperons is studied in K −p interactions at 10 and 16 GeV/ c. The total cross sections are 1010 ± 105 μb and 910 ± 95 μb for Σ +, and 690 ± 70 μb and 700 ± 75 μb for Σ −, at 10 and 16 GeV/ c, respectively. The excess of Σ + over Σ − is found to originate mainly in the proton fragmentation region, from low-multiplicity events of the hypercharge annihilation reactions K −p → Σ ++pions. The production of Σ ± is ∼2.6 times more abundant than that of Σ ∗±(1385) . The channels corresponding to the hypercharge non-annihilating reactions, K − p → Σ ± K K+X , represent ∼25% and ∼35% of the total, at 10 and 16 GeV/ c, respectively. Evidence is found for the production of Σ ∗0(1385), Λ ∗(1405) and Λ ∗(1520) , whose decay account for (7 ± 1)% of the Σ ± observed at both 10 and 16 GeV/ c.

An extended quark recombination model with valence quark annihilation compared to inclusive π+/π− ratios

Valence quark annihilation with subsequent recombination is considered as the dominant nonscaling process contributing to lowp⊥ pion production in the proton fragmentation region at medium energies. With the aid of a Kuti-Weisskopf model for quark distribution functions the inclusive ratios π+/π− have been calculated and compared to data forHp→π± +anything withH=π±,K−,\(\bar p\). Each of these beam particles carries valence antiquarks. The dependence of the ratios on the Feynman variablex and their energy dependence is well reproduced.

Inclusive π+ to π− ratios and quark distributions of pions and nucleons

The ratio R of inclusive π + π − production at low transverse momenta is measured in π + n and pn interactions at 195 GeV/ c. R ( 1 R ) in the proton (neutron) fragmentation region increases with Feynman- x and is smaller than R from π + fragmentation. The results agree with a quark-quark scattering model originally proposed for “hard” processes and disagree with a modified version of the model which includes gluon scattering.

Sdependence of proton fragmentation by hadrons. I. Incident laboratory momenta 4-24 GeV/c

Measurements of the dependence on $s={({p}_{a}+{p}_{b})}^{2}$ of the cross sections for production of single charged hadrons in the reactions $a+b\ensuremath{\rightarrow}c+\mathrm{anything}$ are presented. Particle $c$ was detected in a fixed interval of laboratory momentum and angle in the fragmentation region of the target proton. The ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ and ${K}^{+}$ production data are consistent with the Mueller-Regge prediction of an approach to scaling as $A+B{s}^{\ensuremath{-}\frac{1}{2}}$. Further tests of a simple Regge-pole model indicate that the $s$ dependence measured is fortuitous, and that higher-energy data are required in order to make detailed tests of the model.

Determination of the sea-quark distributions in the proton by single-particle inclusive reactions

We have determined the sea-quark distributions of the proton by using recent data on meson production in the proton fragmentation region in high-energy proton-proton collisions. We find that the magnitude of the sea distributions in hadron reactions is larger than the sea measured in lepton experiments. We interpret this enhancement as due to the additional contribution of quark-antiquark pairs created in the initial hadron collision. From our determination of the sea-quark distributions we are able to predict a number of particle ratios in single-particle inclusive production in p-p collisions. In addition, we have calculated the production cross section for low-mass muon pairs by the Drell-Yan mechanism and have obtained good agreement with experiment.

Inclusive production of lambda in the proton fragmentation region from K−p→ΛX at 4.2 GeV/c

A study of Λ production has been made for the process\(p\underrightarrow {K^ - }\Lambda \) from K−p interactions at 4.2 GeV/c. The total Λ production cross-section is (4.5±0.2) mb and the cross-section in which Λ is associated with\(K\bar K\) in the final state is found to be (0.44±0.03) mb. A study of the polarization is made for the off-mass-shell strangeness annihilations\( \ll K\bar K \gg \to pions\) and strangeness nonannihilations\( \ll K\bar K \gg \to K\bar K + pions\); the polarization, when plotted as a function ofx,pT and (recoiling mass)2, exhibits differences between the two processes. The polarization observed in the strangeness nonannihilation process shows identical behaviour to that in\(p\bar p\) reactions. An attempt has been made to understand the behaviour of the polarized and the unpolarized cross-sections as a function of (recoiling mass)2 in the triple-Regge framework.

Neutral kaon production in K +p interactions at 32 GeV/ c

The production of neutral kaons in the reaction K +p → K n + X is studied at the incident momentum of 32 GeV/ c. Inclusive cross sections and single-particle distributions are presented and compared with the data at lower energies. The total inclusive cross section amounts to 7.9 ± 0.3 mb at 32 GeV/ c and is significantly higher than at lower energies due to the rapid rise of multikaon production. The fraction of K n's coming from the decay of the K ∗ resonances stays roughly constant with energy between 8.2 and 32 GeV/ c. In the central and beam fragmentation regions the single-particle distributions reveal no energy dependence between the 16 and 32 GeV/ c data in contrast with the behaviour at lower energies, while in the proton fragmentation region the data are compatible with the trend observed at lower energies and with theoretical expectations.