This paper presents a measurement of the production cross-section of a $Z$ boson in association with $b$- or $c$-jets, in proton-proton collisions at $\sqrt{s} = 13$ TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 140 fb$^{-1}$. Inclusive and differential cross-sections are measured for events containing a $Z$ boson decaying into electrons or muons and produced in association with at least one $b$-jet, at least one $c$-jet, or at least two $b$-jets with transverse momentum $p_\textrm{T} > 20$ GeV and rapidity $|y| < 2.5$. Predictions from several Monte Carlo generators based on next-to-leading-order matrix elements interfaced with a parton-shower simulation, with different choices of flavour schemes for initial-state partons, are compared with the measured cross-sections. The results are also compared with novel predictions, based on infrared and collinear safe jet flavour dressing algorithms. Selected $Z + \ge 1 c$-jet observables, optimized for sensitivity to intrinsic-charm, are compared with benchmark models with different intrinsic-charm fractions.
Figure 6(left) of the article. Measured fiducial cross sections for events with $Z (\rightarrow ll) \ge 1 $ b-jets. The thin inner band corresponds to the statistical uncertainty of the data, and the outer band to statistical and systematic uncertainties of the data, added in quadrature.
Figure 6(right) of the article. Measured fiducial cross sections for events with $Z (\rightarrow ll) \ge 2 $ b-jets. The thin inner band corresponds to the statistical uncertainty of the data, and the outer band to statistical and systematic uncertainties of the data, added in quadrature.
Figure 7 of the article. Measured fiducial cross sections for events with $Z (\rightarrow ll) \ge 1 $ c-jets. The thin inner band corresponds to the statistical uncertainty of the data, and the outer band to statistical and systematic uncertainties of the data, added in quadrature.
We have measured cross sections for forward neutron production from a variety of targets using proton beams from the Fermilab Main Injector. Measurements were performed for proton beam momenta of 58 GeV/c, 84 GeV/c, and 120 GeV/c. The cross section dependence on the atomic weight (A) of the targets was found to vary as $A^(alpha)$ where $\alpha$ is $0.46\pm0.06$ for a beam momentum of 58 GeV/c and 0.54$\pm$0.05 for 120 GeV/c. The cross sections show reasonable agreement with FLUKA and DPMJET Monte Carlos. Comparisons have also been made with the LAQGSM Monte Carlo.
Total inelastic PP cross section.
Average multiplicities and production cross section for neutral particles from PP interactions at 84 GeV.
Cross sections for neutron production greater than threshold and within an angular range of 20.4 mrad.
The production of neutrons carrying at least 20% of the proton beam energy ($\xl > 0.2$) in $e^+p$ collisions has been studied with the ZEUS detector at HERA for a wide range of $Q^2$, the photon virtuality, from photoproduction to deep inelastic scattering. The neutron-tagged cross section, $e p\to e' X n$, is measured relative to the inclusive cross section, $e p\to e' X$, thereby reducing the systematic uncertainties. For $\xl >$ 0.3, the rate of neutrons in photoproduction is about half of that measured in hadroproduction, which constitutes a clear breaking of factorisation. There is about a 20% rise in the neutron rate between photoproduction and deep inelastic scattering, which may be attributed to absorptive rescattering in the $\gamma p$ system. For $0.64 < \xl < 0.82$, the rate of neutrons is almost independent of the Bjorken scaling variable $x$ and $Q^2$. However, at lower and higher $\xl$ values, there is a clear but weak dependence on these variables, thus demonstrating the breaking of limiting fragmentation. The neutron-tagged structure function, ${{F}^{\rm\tiny LN(3)}_2}(x,Q^2,\xl)$, rises at low values of $x$ in a way similar to that of the inclusive \ff of the proton. The total $\gamma \pi$ cross section and the structure function of the pion, $F^{\pi}_2(x_\pi,Q^2)$ where $x_\pi = x/(1-\xl)$, have been determined using a one-pion-exchange model, up to uncertainties in the normalisation due to the poorly understood pion flux. At fixed $Q^2$, $F^{\pi}_2$ has approximately the same $x$ dependence as $F_2$ of the proton.
The XL bins, their acceptance and the acceptance uncertainty. The RH columnshows the contribution from the energy-scale uncertainty - this is completely c orrelated between the bins.
The slope of the PT**2 distribution from the 1995 DIS data. The uncertainties shown in this table were communicated to us by the authors, and supercede those given in the paper.
The normalized cross section (1/SIG)DSIG/dXL for leading neutrons with THETA < 0.8 mrad with statistical errors only.. For the lowest Q**2 data, the normalization uncertainty is +-5 PCT, and with XL > 0.52 there is a further normalization uncertainty of +-4 PCT.. For the intermediate Q**2 and DIS data the normalization uncertainty is +-4 PCT.
The inclusive cross section for the photoproduction of neutral pions has been measured as a function of the transverse momentum, rapidity, and Feynman x of the pizero mesons at an average photon--proton centre-of-mass energy of 208 GeV and for photon virtualities below Q^2=0.01 GeV^2. The pizero measurement extends the range covered by previous charged particle measurements at HERA by two units of rapidity in the photon direction down to a value of -5.5 in the gamma p centre-of-mass frame. The pizero transverse momentum distribution is well described over the whole measured range by a power law ansatz, while an exponential fit falls below the data at transverse momentum values above 1.5 GeV/c. Good agreement with the predictions of the Monte Carlo models PYTHIA and PHOJET is found. In the context of the PYTHIA model the data are inconsistent with large intrinsic transverse momentum values in the photon.
The inclusive PI0 photoproduction cross section in bias of rapidity and PT.Bin centre corrections have been applied and the errors are the quadratic sum o f the statistics and systematics (which dominate).
The inclusive PI0 photoproduction cross section as a function of PT for therapidity range -3.5 to -1.5. Bin centres are given in addition to limits. Error s are the quadratic sum of statistics and systematics.
The inclusive PI0 photoproduction cross section as a function of XL (the Feyman X variable) for the rapidity range -3.5 to -1.5. Bin centres are given as well as limits. Errors are the quadratic sum of statistics and systematics.
We report on the production of J/psi mesons in 530 and 800 GeV/c proton - Be collisions in the Feynman-x range 0.0 < xf < 0.6. The J/psi mesons were detected via decays into opposite sign muon pairs. Differential distributions for J/psi production have been measured as functions of xf, pT^2, and cosine of the Gottfried-Jackson decay angle. These distributions are compared with results on J/psi production obtained in 515 GeV/c pion - Be collisions, measured by the same experiment, as well as with results from other experiments using incident protons.
Differential XL distribution for J/PSI production in 530 GeV pBe collisions. Errors are combined statistics and systematics.
Differential PT**2 distribution for J/PSI production in 530 GeV pBe collisions. Errors are combined statistics and systematics.
Differential COS(THETA) distribution for J/PSI production in 530 GeV pBe collisions. Errors are combined statistics and systematics.
We have studied the production of J/ψ and ψ(2S) charmonium mesons in 515 GeV/c π−Be collisions in the Feynman-x range 0.1
Statistical errors only. Normalization uncertainty is 12%.
Statistical errors only. Normalization uncertainty is 12%.
Statistical errors only. Normalization uncertainty is 12%.. Theta is the angle between the MU+ and the beam axis in the J/PSI restframe (Gottfried-Jackson decay angle).
A study of scaling violations in fragmentation functions performed by the ALEPH collaboration at LEP is presented. Data samples enriched in uds, c, b and gluon jets, respectively, together with measurements of the longitudinal and transverse inclusive cross sections are used to extract the fragmentation function for the gluon and for each flavour. The measurements are compared to data from experiments at energies between 22 GeV and 91 GeV and scaling violations consistent with QCD predictions are observed. From this, a measurement of the strong coupling constant α s ( Mz ) = 0.126 ±0.009 is obtained.
No description provided.
No description provided.
No description provided.
This paper presents results on charm photoproduction in the energy interval 40 to 160 GeV, obtained from the high-statistics charm samples of the NA 14/2 experiment at CERN. We measure the charm cross-section, the distributions inxF andp2T and various production ratios and charge asymmetries. The total non-diffractive open-charm cross-section per nucleon is measured to be\(\sigma _{(\gamma N \to c\bar cX)} \) at 〈Eγ〉 =100 GeV. We discuss the photoproduction of charm in terms of theoretical and phenomenological models. We compare the measuredp2T andxF distributions with first-order QCD calculations of photon-gluon fusion and obtain a value for the charm-quark mass ofmc=1.5+0.2−0.1GeV/c2.
D0 cross section assuming branching ratio of D0 --> K- PI+ of 3.65 +- 0.21 PCT.
D+(-) cross section assuming branching ratio of D+ --> K- PI+ PI+ of 8.0 +0.8,-0.7 PCT.
Total non diffractive open charm production cross section allowing for contributions for other charmed particles (D/S and LAMBDA/C). Comparison of data with first order QCD leads to a predicted charm quark mass of 1.5 +0.2,-0.1 GeV.
None
Data is extrapolated to full x range.
Data requested from authors.
We present the general properties of jets produced bye+e− annihilation. Their production and fragmentation characteristics have been studied with charged particles for c.m. energies between 12 and 43 GeV. In this energy rangee+e− annihilation into hadrons is dominated by pair production of the five quarksu, d, s, c andb. In addition, hard gluon bremsstrahlung effects which are invisible at low energies become prominent at the high energies. The observed multiplicity distributions deviate from a Poisson distribution. The multiplicity distributions for the overall event as well as for each event hemisphere satisfy KNO scaling to within ∼20%. The distributions ofxp=2p/W are presented; scale breaking is observed at the level of 25%. The quantityxpdδ/dxp is compared with multigluon emission calculations which predict a Gaussian distribution in terms of ln(1/x). The observed energy dependence of the maximum of the distributions is in qualitative agreement with the calculations. Particle production is analysed with respect to the jet axis and longitudinal and transverse momentum spectra are presented. The angular distribution of the jet axis strongly supports the idea of predominant spin 1/2 quark pair production. The particle distributions with respect to the event plane show clearly the growing importance of planar events with increasing c.m. energies. They also exclude the presence of heavy quark production,e+e−→Q\(\bar Q\) for quark masses up to 5
R VALUES BELOW 32.5 GEV ARE IDENTICAL TO THOSE GIVEN IN BRANDELIK ET AL., PL 113B, 499 (1982).
No description provided.
CHARGED PARTICLE MULTIPLICITY DISTRIBUTIONS.
Forum