Charm-charm correlation properties are studied in detail for the first time using a sample of D D pairs produced in 360 GeV/ c π − p interactions. The data are compared with various models of charm production.
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We have measured the inclusive production properties of D and D messons produced from pp interactions at s =27.4 GeV . The differential production cross section is well represented by the empirical form d 2 σ d x F d P 2 T = 1 2 [σ ( D / D )(n+1)b](1−|x F |) n exp (−bp 2 T ) with n=4.9 ± 0.5, b=(1.0±0.1)( GeV /c) −2 , and the inclusive D / D cross section σ ( D / D ) is (30.2±3.3) ωb. The QCD fusion model predicts D / D production which is in good agreement with our data except for the magnitude of the cross section which depends sensitively on the assumed mass of the charm quark.
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Results of fitting the differential distributions in x F and p T 2 of D mesons produced in 400 GeV/ c p-p interactions to the form d 2 σ d x F d p T 2 ∝(1−x F ) n exp [−(p T 2 /〈p T 2 〉)] are discussed. The D + distribution is found to be relatively hard [ n =3.1±0.8〈 P t 2 〉=1.32±0.27 (GeV/ c ) 2 ] and the D̄ 0 distribution relatively soft [ n =8.1±1.9,〈 p T 2 〉=0.62±0.14 (GeV/ c ) 2 ] compared to the average for all D's [ n =4.9±0.5,〈 p T 2 〉=0.99±0.10 (GeV/ c ) 2 ]. It is suggested that these distributions could reflect contribution of leading di-quarks in pp collisions. Comparison is made with evidence for leading quarks in charm production in 360 GeV/ cπ − p interactions.
The invariant (C=INV) and non-invariant (C=NON-INV) distributions are fitted to (1-XL)**POWER. Pt distribution is fitted to EXP(-PT**2/SLOPE).
We report evidence for the production of the charged D ∗ mesons in pp̄ collisions at s = 540 GeV . The search was confined to the charged particle fragments of hadronic jets, which are expected to be predominantly gluon jets in this experiment. The fragmentation function and production rate for D ∗ in jets of average transverse momentum of 28 GeV/ c are given.
THE D*'S ARE CONSIDERED AS ARISING ONLY FROM FRAGMENTATION OF HADRONIC JETS ('GLUON' JETS). HERE THE <PT> OF THE JET IS AROUND 28 GEV THE DEFINITION OF Z IS P(D*).P(JET)/(P(JET))**2.
Inclusive K 0 -production has been measured in e + e - annihilation at a center of mass energy of about W = 30 GeV. The ratio of K 0 + K 0 production to μ + μ - production is R K 0 = 5.6 ± 1.1 (statist. error) ± 0.8 (system.error) This value is about a factor of three higher than R K 0 at W = 7 GeV. The cross sections ( s / β ) d σ /d x is consistent with a scaling behaviour.
No description provided.
DIFFERENTIAL CROSS SECTION.
INVARIANT CROSS SECTION.
This paper presents measurements of the inclusive production cross sections of Λ baryons in e+e− annihilations at s=29 GeV. The data sample corresponds to an integrated luminosity of 256 pb−1 collected with the High-Resolution Spectrometer at the SLAC storage ring PEP. Comparisons are made to the predictions of the Lund model. The data are well described with use of a strange-diquark suppression parameter, (usud)(sd), of 0.89 ± 0.10−0.16+0.56, and the measured Λc→Λ+X branching ratio of (23 ± 10)%.
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Rapidity relative to thrust axis.
Corrected for unobserved moment regions.
We present the measurements of the Λ c production cross section in proton-proton interactions at s =27.4 GeV and give new limits on the exclusive branching ratio Λ c →pK + π − .
No description provided.
We have observed Λc baryons in nonresonant e+e− annihilation at energies around s=10.5 GeV through their decay to Λπ+π+π−. We measure the branching fraction to be (2.8 ± 0.7 ± 1.1)%. The momentum spectrum of the Λc is similar to that of charmed mesons, providing a constraint on models of charmed-quark hadronization.
Data are extrapolated over whole x range using the 'Peterson' formula.
We have observed Σc++ and Σc0 baryons in nonresonant e+e− interactions through their decays to Λc+π± using the CLEO detector. The mass difference M(Σc++)-M(Λc+) is measured to be 167.8±0.4±0.3 MeV; for M(Σc0)-M(Λc+) we find 167.9±0.5±0.3 MeV. Σc decay accounts for (18±3±5)% of Λc+ production.
The cross section ratio is multiplied by a factor of 1.5 to account for theunobserved SIGMA/C(2455)+.
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The cross sections for Ξ− and Ω− inclusive production in Ξ− Be collisions at 116 GeV/c have been measured in the kinematic domain [0.1<xF<0.9, 0<pT<1.7 GeV/c]. The integrated cross sections per nucleon are found to be about twice as large as in Ξ−p collisions. The invariant cross sections increase by a factor of 70 for the Ξ−s and of 100 for the Ω−s between the central region (xF∼0.2) and the projectile fragmentation region (xF∼0.8). In the central region, they have about the same magnitude as the ones for Ξ− and Ω− inclusive production inp nucleon collisions. The Ξ− and Ω− polarisations have been measured over the same kinematic domain and are found to be compatible with zero.
The process e + e − → π 0 + anything has been measured at c.m. energies of 14 and 34 GeV for π 0 energies between 0.5 and 4 GeV. The ratio of π 0 to π ± production for π momenta between 0.5 and 1.5 GeV/ c is measured to be 2 σ ( π 0 )/ [ σ ( π + ) + σ ( π − )] = 1.3 ± 0.4 (1.2 ± 0.4) at 14 (34) GeV. The scaled cross section ( s / μ )d σ /d x when compared with lower energy (4.9–7.4 GeV) π 0 data indicates a substantial scaling violation.
COMPARISON OF PI0 WITH CHARGED PION CROSS SECTIONS (SCALED BI 1/S TO SAME ENERGIES).
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Inclusive ϱ 0 meson production has been measured in 120 GeV and 280 GeV muon-proton interactions. Distributions of z and p T 2 are presented. Primary ϱ 0 production is found to be equal to that of π 0 production within errors.
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Inclusive distributions of ρ0 and ω mesons have been measured in deep inelastic μ-p interactions at 280 GeV/c. A comparison of the ρ0 cross sections with other leptoproduction experiments is presented. The ω results represent the first observation of this inclusive channel in high energy leptoproduction. The ρ0 and ω yields are found to be equal as may be expected from the available density of states in isospin space. This contrasts with spin angular momentum where the vector to pseudoscalar meson ratio is suppressed relative to the available number of spin states.
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The prompt production of the charm baryon $\rm \Lambda_{c}^{+}$ and the $\rm \Lambda_{c}^{+}/\mathrm {D^0}$ production ratios were measured at midrapidity with the ALICE detector in pp and p-Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$TeV. These new measurements show a clear decrease of the $\rm \Lambda_{c}^{+}/\mathrm {D^0}$ ratio with increasing transverse momentum ($p_{\rm T}$) in both collision systems in the range $2<p_{\rm T}<12$ GeV/$c$, exhibiting similarities with the light-flavour baryon-to-meson ratios ${\rm p}/\pi$ and $\Lambda/\mathrm {K^0_S}$. At low $p_{\rm T}$, predictions that include additional colour-reconnection mechanisms beyond the leading-colour approximation; assume the existence of additional higher-mass charm-baryon states; or include hadronisation via coalescence can describe the data, while predictions driven by charm-quark fragmentation processes measured in $\mathrm {e^+e^-}$ and $\mathrm {e^-p}$ collisions significantly underestimate the data. The results presented in this letter provide significant evidence that the established assumption of universality (colliding-system independence) of parton-to-hadron fragmentation is not sufficient to describe charm-baryon production in hadronic collisions at LHC energies.
Prompt $\Lambda_{\rm {c}}^{+}$ baryon $p_{\rm {T}}$-differential cross section in pp collisions at $\sqrt{s} = 5.02$ TeV in the rapidity interval $|y|<0.5$.
Prompt $\Lambda_{\rm {c}}^{+}$ baryon $p_{\rm {T}}$-differential cross section in p-Pb collisions at $\sqrt{s_{\rm {NN}}} = 5.02$ TeV in the rapidity interval $-0.96 \lt y \lt 0.04$.
The nuclear modification factor $R_\mathrm{pPb}$ of prompt $\Lambda_{\rm {c}}^{+}$ baryons in p-Pb collisions at $\sqrt{s_{\rm {NN}}} = 5.02$ TeV in the rapidity interval $ -0.96\lt y \lt 0.04$.
We report on the measurement of $\rm{J}/\psi$ production in the dielectron channel at mid-rapidity (|y|<1) in p+p and d+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV from the STAR experiment at the Relativistic Heavy Ion Collider. The transverse momentum $p_{T}$ spectra in p+p for $p_{T}$ < 4 GeV/c and d+Au collisions for $p_{T}$ < 3 GeV/c are presented. These measurements extend the STAR coverage for $\rm{J}/\psi$ production in p+p collisions to low $p_{T}$. The $<p_{T}^{2}>$ from the measured $\rm{J}/\psi$ invariant cross section in p+p and d+Au collisions are evaluated and compared to similar measurements at other collision energies. The nuclear modification factor for $\rm{J}/\psi$ is extracted as a function of $p_{T}$ and collision centrality in d+Au and compared to model calculations using the modified nuclear Parton Distribution Function and a final-state $\rm{J}/\psi$ nuclear absorption cross section.
The mean square of $p_T$.
Nuclear absorption cross section.
Pairs of τ leptons produced at s=3.77 GeV have been studied in eμ, ee, and μμ final states. The leptonic branching ratios have been measured to be B(τ→eνν)=(18.2±0.7±0.5)% and B(τ→μνν)=(18.0±1.0±0.6)%. Limits have been set for the two-body decays τ→eG and τ→μG, where G is a light Goldstone boson.
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The Indiana Silicon Sphere 4π detector has been used to measure light-charged particles and intermediate-mass fragments (IMFs) emitted in the 18–4.8 GeV He3+natAg, Au197 reactions. Ejectile multiplicity and total event kinetic energy distributions scale systematically with projectile energy and target mass, except for the Agnat target at 3.6 and 4.8 GeV. For this system, a saturation in deposition energy is indicated by the data, suggesting the upper projectile energy for stopping has been reached. Maximum deposition energies of ∼950 MeV for the Agnat target and ∼1600 MeV for the Au197 target are inferred from the data. The results also demonstrate the importance of accounting for fast cascade processes in defining the excitation energy of the targetlike residue. Correlations between various observables and the average IMF multiplicity indicate that the total thermal energy and total observed charge provide useful gauges of the excitation energy of the fragmenting system. Comparison of the experimental distributions with intranuclear cascade predictions shows qualitative agreement. © 1996 The American Physical Society.
Multifragmentation of Agnat and Au197 nuclei induced by 1.8–4.8 GeV He3 ions has been studied with the Indiana Silicon Sphere 4π detector array. Rapidity, moving source, and sphericity-coplanarity analyses are consistent with near-simultaneous emission from a source in approximate kinetic equilibrium. For the most dissipative collisions, the spectral peaks are broadened and shifted to very low energies, indicative of emission from an extended nuclear system with ρ/ρ0∼1/3. Predictions of an intranuclear cascade/expanding, emitting source model compare well with experimental multiplicity distributions and the evolution of fragment spectral shapes. © 1996 The American Physical Society.
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We have studied the inclusive production of the hadrons π ± , K ± , p, p , Λ, Λ , ρ and ⋉ in the central region at the ISR s = 53 GeV , in both pp and p p collisions. Differences are observed only for K ± , p, and p production. We then study also correlations between low- p T pp and p p pairs in the two types of collisions, separating the contribution from baryon pair production and from the incident particles (stopping protons). We observe a positive correlation between two stopping protons; between the production of two pairs, and between a stopping proton and a pair production, there are negative correlations.
No description provided.
Inclusive data are presented on ϱ 0 ,ϱ + and ω produced in k + p interactions at 250 GeV/ c , for ϱ + and ω for the first time in K + p experiment. In the forward CM hemisphere, the ϱ + , ϱ 0 and ω differential production rates are equal within errors, and remarkably similar to muon-inelastic scattering data on ϱ 0 and ω at 280 GeV/ c .
No description provided.
The energy distribution of inclusive hadrons produced by 280 GeV muons on hydrogen and deuterium targets are compared. The sum of the scaled energy distributions of the positive and negative hadrons is found to be the same for the two targets. The difference of these distributions is observed to factorise inx andz and thez-dependence is found to be independent of the target type and have a form (1−z)2.1±0.2. The net charge of the hadronic jet is positive at highx even in the case when the scattering takes place on the neutron. These results are in good agreement with the expectations of the Quark Parton Model.
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The fragmentation functions of u-quarks into positive and negative pions are determined from an analysis of identified pions produced in deep inelastic muon-deuterium scattering. The method adopted is not sensitive to the knowledge of the primary quark distribution functions. The fragmentation of u quarks to positive pions is found to fall less steeply in z than that to negative pions as expected in the quark parton model.
Results onK0 and Λ production ine+e− annihilation at c.m. energies of 14, 22 and 34 GeV are presented. The shape of theK0 and Λ differential cross sections are very similar to each other and to those of π±,K± and\(p(\bar p)\). Scaling violations are observed forK0 production. We obtain a value for the probability to produce strange quark-antiquark pairs relative to that to produce up or down quark-antiquark pairs of 0.35±0.02±0.05. The value ofRh=σ(e+e-→hX)/σµµ is shown to rise steadily with c.m. energy for all particle species. At 34 GeV we find 1.48±0.05K0 and 0.31±0.03 Λ per event. We have searched for possible Λ polarization. The production ofK0's and Λ's in jets is examined as a function ofpT2 and rapidity and compared to that of all charged particles; the yields in two and three jets are also investigated. Results are presented from events with two baryons\((\Lambda ,\bar \Lambda ,por\bar p)\) observed.
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The strong coupling constant, αs, has been determined in hadronic decays of theZ0 resonance, using measurements of seven observables relating to global event shapes, energy correlatio
Data corrected for finite acceptance and resolution of the detector and for intial state photon radiation. No corrections for hadronic effects are applied.. Errors include statistical and systematic uncertainties, added in quadrature.
Data corrected for finite acceptance and resolution of the detector and for intial state photon radiation. No corrections for hadronic effects are applied.. Errors include statistical and systematic uncertainties, added in quadrature.
Data corrected for finite acceptance and resolution of the detector and for intial state photon radiation. No corrections for hadronic effects are applied.. Errors include statistical and systematic uncertainties, added in quadrature.
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