The multiplicities per event of π ± and K ± are measured separately for e + e - annihilation into c c , b b , and light quark pairs at E cm=29 GeV. The K ± multiplicity is higher for heavy quark events than for light quark events. The π ± multiplicity and the π ± scaled differential cross section at low x = E beam/ E beam are found to be higher for b b events than for other events.
Numerical values requested from authors. Data given separately for (b bbar), (c cbar) and light quark jets.
Measured multiplicities for (b bbar) jets.
Measured multiplicities for (c cbar) jets.
The inclusive production cross sections and mean multiplicities of π±, K±, p, and p¯ in e+e− annihilation at a c.m. energy of 29 GeV have been measured with the time-projection chamber at PEP, using ionization energy loss to separate particle types. On average, 10.7±0.6 π±, 1.35±0.13 K±, and 0.60±0.08 p,p¯ are contained in an annihilation event. The fraction of pions among final-state particles decreases from over 95% at 0.3 GeV/c momentum to about 60% at high momentum; the kaon and proton fractions rise correspondingly.
PARTICLE FRACTIONS.
PARTICLE FRACTIONS.
PARTICLE FRACTIONS.
We present a study of the inclusive production of neutral pions and charged particles from 112 000 hadronic Z 0 decays. The measured inclusive momentum distributions can be reproduced by parton shower Monte Carlo programs and also by an analytical QCD calculation. Comparing our results to e + e − data between √ s = 9 and 91 GeV, we findfind that the evolution of the spectra with center of mass energy is consistent with the QCD predictions.
No description provided.
Error is dominated by systematic uncertainties.
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We present a study of the global event shape variables thrust and heavy jet mass, of energy-energy correlations and of jet multiplicities based on 250 000 hadronic Z 0 decays. The data are compared to new QCD calculations including resummation of leading and next-to-leading logarithms to all orders. We determine the strong coupling constant α s (91.2 GeV) = 0.125±0.003 (exp) ± 0.008 (theor). The first error is the experimental uncertainty. The second error is due to hadronization uncertainties and approximations in the calculations of the higher order corrections.
Measured EEC distribution corrected for detector effects and photon radiation. Errors are combined statistical and systematic uncertainties.
Measured average jet multiplicities for the K_PT algorithm. All numbers are corrected for detector effects and photon radiation. Errors are combined statistical and systematic uncertainties.
Value of strong coupling constant, alpha_s, determined from the data. First error is experimental, the second is theoretical.
The structure of hadronic events fromZ0 decay is studied by measuring event shape variables, factorial moments, and the energy flow distribution. The distributions, after correction for detector effects and initial and final state radiation, are compared with the predictions of different QCD Monte Carlo programs with optimized parameter values. These Monte Carlo programs use either the second order matrix element or the parton shower evolution for the perturbative QCD calculations and use the string, the cluster, or the independent fragmentation model for hadronization. Both parton shower andO(α2s matrix element based models with string fragmentation describe the data well. The predictions of the model based on parton shower and cluster fragmentation are also in good agreement with the data. The model with independent fragmentation gives a poor description of the energy flow distribution. The predicted energy evolutions for the mean values of thrust, sphericity, aplanarity, and charge multiplicity are compared with the data measured at different center-of-mass energies. The parton shower based models with string or cluster fragmentation are found to describe the energy dependences well while the model based on theO(α2s calculation fails to reproduce the energy dependences of these mean values.
Unfolded Thrust distribution. Statistical error includes statistical uncertainties of the data as well as of the unfolding Monte Carlo Sample. The systematic error combines the uncertainties of measurements and of the unfolding procedure.
Unfolded Major distribution where Major is defined in the same way as Thrust but is maximized in a plane perpendicular to the Thrust axis.
Unfolded Minor distribution where the minor axis is defined to give an orthonormal system.
We present a study of the inclusive production of π 0 , η, K s 0 and Λ based on 929,000 hadronic Z decays recorded with the L3 detector at LEP. The measured inclusive momentum distributions have been compared with predictions from parton shower models as well as an analytical Quantum Chromodynamics calculation. Comparing to low energy e + e - data, we find that QCD describes the energy evolution of the hadron spectrum.
No description provided.
No description provided.
No description provided.
Data on inclusive and semi-inclusive production of nonstrange meson resonances from a bubble chamber study of pn interactions at 19 GeV/c are presented. Most of the results concern ρ0 production. The inclusive cross-sectionσ(pn → ρ0+x)=(2.4±0.4) mb agrees well with pp data. The ρ0 cross-sections are equal in the protonlike and neutron-like hemispheres. The differential cross-sections are in general agreement with earlier observation in pp interactions. In the fragmentation region the approximate structure function can be described byEdσ/dx= =a(1−|x|)n withn=3.0±0.8 in agreement with recent predictions from quark counting rules. The production of ω(780) is observed in the reaction pn→pp+ω+X with a cross-section σ=(0.13±0.03) mb. There is indication of f0(1270) and g(1680) production.
Axis error includes +- 0.0/0.0 contribution (?////FITTING ERRORRES-DEF(RES=RHO0,BACK=CORRECTED,DEF=0.5 < M(PI+ PI-) < 1.05 GEV,C=MASS AND WIDTH FROM PDG 1980)//RES-DEF(RES=F,BACK=CORRECTED,DEF=0.9 < M(PI+ PI-) < 1.5 GEV,C=MASS AND WIDTH FROM PDG 1980)//RES-DEF(RES=G(1700)0,BACK=CORRECTED,DEF=1.36 < M(PI+ PI-) < 2.1 GEV,C=MASS AND WIDTH FROM PDG 1980)NO REFLECTIONS ,E.G. FROM DEL++, DEL-, OMEGA HAVE BEEN CONSIDERED).
Axis error includes +- 0.0/0.0 contribution (?////FITTING ERRORRES-DEF(RES=RHO0,BACK=CORRECTED,DEF=0.5 < M(PI+ PI-) < 1.05 GEV,C=MASS AND WIDTH FROM PDG 1980)//RES-DEF(RES=F,BACK=CORRECTED,DEF=0.9 < M(PI+ PI-) < 1.5 GEV,C=MASS AND WIDTH FROM PDG 1980)//RES-DEF(RES=G(1700)0,BACK=CORRECTED,DEF=1.36 < M(PI+ PI-) < 2.1 GEV,C=MASS AND WIDTH FROM PDG 1980)NO REFLECTIONS ,E.G. FROM DEL++, DEL-, OMEGA HAVE BEEN CONSIDERED).
Axis error includes +- 0.0/0.0 contribution (?////FITTING ERRORRES-DEF(RES=RHO0,BACK=CORRECTED,DEF=0.5 < M(PI+ PI-) < 1.05 GEV,C=MASS AND WIDTH FROM PDG 1980)//RES-DEF(RES=F,BACK=CORRECTED,DEF=0.9 < M(PI+ PI-) < 1.5 GEV,C=MASS AND WIDTH FROM PDG 1980)//RES-DEF(RES=G(1700)0,BACK=CORRECTED,DEF=1.36 < M(PI+ PI-) < 2.1 GEV,C=MASS AND WIDTH FROM PDG 1980)NO REFLECTIONS ,E.G. FROM DEL++, DEL-, OMEGA HAVE BEEN CONSIDERED).
Measurements of jet characteristics from inclusive jet production in proton-proton collisions at a centre-of-mass energy of 7 TeV are presented. The data sample was collected with the CMS detector at the LHC during 2010 and corresponds to an integrated luminosity of 36 inverse picobarns. The mean charged hadron multiplicity, the differential and integral jet shape distributions, and two independent moments of the shape distributions are measured as functions of the jet transverse momentum for jets reconstructed with the anti-kT algorithm. The measured observables are corrected to the particle level and compared with predictions from various QCD Monte Carlo generators.
The measured differential jet shape $\rho(r)$ for jets with 20 GeV $< p_{\mathrm{T}} <$ 25 GeV and 0 <|y|< 0.5. The CF in the table refers to unfolding correction factor from {\sc pythia6} Tune Z2. The systematic uncertainties from different sources, jet energy scale (JES), unfolding, and single particle response (SPR), are also presented.
The measured differential jet shape $\rho(r)$ for jets with 25 GeV $< p_{\mathrm{T}} <$ 30 GeV and 0 <|y|< 0.5. The CF in the table refers to unfolding correction factor from {\sc pythia6} Tune Z2. The systematic uncertainties from different sources, jet energy scale (JES), unfolding, and single particle response (SPR), are also presented.
The measured differential jet shape $\rho(r)$ for jets with 30 GeV $< p_{\mathrm{T}} <$ 40 GeV and 0 <|y|< 0.5. The CF in the table refers to unfolding correction factor from {\sc pythia6} Tune Z2. The systematic uncertainties from different sources, jet energy scale (JES), unfolding, and single particle response (SPR), are also presented.
A measurement of the underlying activity in scattering processes with transverse momentum scale in the GeV region is performed in proton-proton collisions at sqrt(s) = 0.9 TeV, using data collected by the CMS experiment at the LHC. Charged hadron production is studied with reference to the direction of a leading object, either a charged particle or a set of charged particles forming a jet. Predictions of several QCD-inspired models as implemented in PYTHIA are compared, after full detector simulation, to the data. The models generally predict too little production of charged hadrons with pseudorapidity eta < 2, p_T > 0.5 GeV/c, and azimuthal direction transverse to that of the leading object.
Average multiplicity of charged particles per unit of pseudorapidity as a function of pseudorapidity for events with leading track-jet transverse momenta > 1 and > 3 GeV. Statistical errors only.
Average scalar sum of the transverse momenta of charged particles per unit of pseusdorapidity and per radian as a function of DELTA(PHI) for events with leading track-jet transverse momenta > 1 and > 2 GeV. Statistical errors only. Typical systematic error of 1.8 PCT at a leading track-jet PT of 3.5 GeV.
The average multiplicity and average scalar sum of transverse momenta of charge particles per unit of pseudorapidity and per radian as a function of the leading track transverse momenta. Statistical errors only. Typical systematic error of 1.8 PCT at a leading track-jet PT of 3.5 GeV.
The charged particle multiplicities of two- and three-jet events from the reaction e+e- -> Z0 -> hadrons are measured for Z0 decays to light quark (uds) flavors. Using recent theoretical expressions to account for biases from event selection, results corresponding to unbiased gluon jets are extracted over a range of jet energies from about 11 to 30 GeV. We find consistency between these results and direct measurements of unbiased gluon jet multiplicity from upsilon and Z0 decays. The unbiased gluon jet data including the direct measurements are compared to corresponding results for quark jets. We perform fits based on analytic expressions for particle multiplicity in jets to determine the ratio r = Ng/Nq of multiplicities between gluon and quark jets as a function of energy. We also determine the ratio of slopes, r(1) = (dNg/dy)/(dNq/dy), and of curvatures, r(2) = (d2Ng/dy2)/(d2Nq/dy2), where y specifies the energy scale. At 30 GeV, we find r = 1.422 +/- 0.051, r(1) = 1.761 +/- 0.071 and r(2) = 1.98 +/- 0.13, where the uncertainties are the statistical and systematic terms added in quadrature. These results are in general agreement with theoretical predictions. In addition, we use the measurements of the energy dependence of Ng and Nq to determine an effective value of the ratio of QCD color factors, CA/CF. Our result, CA/CF = 2.23 +/- 0.14 (total), is consistent with the QCD value of 2.25.
Measurements of the mean charged particle multiplicity of biased two-jet uds flavour events from Z0 decays as a function of the transverse momentum cutoff PT(C=LU) used to separate two- and three-jet events.
Measurements of the mean charged particle multiplicity of three-jet uds flavour 'Y events' from Z0 decays, as a function of the angle THETA1 between the lowest two energy jets. The results for the quark jet scale SQRT(S(C=QQBAR)) and the gluon jet scales PT(C=LU) and PT(C=LE) are also given.
Measurements of the unbiased gluon multiplicity as a function of the energy scale Q=PT(C=LU). The corresponding bins of THETA1 in 'Y events' are also indicated.