A study of kinematical correlations between charmed particles produced in π-Cu interactions at √s = 26 GeV
TL;DR: In this article, a sample of 475 events, in which two charmed-particle decays are observed, is analyzed to determine distributions of twoparticle kinematic variables.
About: This article is published in Physics Letters B.The article was published on 1996-09-26 and is currently open access. It has received 9 citations till now. The article focuses on the topics: Quantum chromodynamics.
Summary (2 min read)
Jump to: [1 Introduction] – [2 Event selection] – [3 Momentum estimator] – [4 Background subtraction and acceptances] – [5 Results] and [6 Conclusions]
1 Introduction
- Hadroproduction of heavy quarks is an important testing ground for Quantum Chro- modynamics (QCD).
- The observed experimental correlations between charmed particles provide a test of the NLO QCD calculations.
- These variables are useful in subsequent comparisons with the predictions of charm production models.
- The DkD has analogue readout so that secondary interactions in the detector material may be identi ed by their large energy deposits.
- More details of the description and performance of the experimental apparatus can be found in Refs. [3, 4].
2 Event selection
- Events are selected in which one charmed particle is fully reconstructed, while recon- struction of the decay vertex is all that is required for the second.
- At this stage no cut is applied on the charmed candidate's invariant mass, except that 2-prong vertices compatible with K0 or 0 decays are rejected.
- From the events which satisfy the previous requirements, 690 (2251) in the 1992 (1993) data, the authors extract two samples: the signal sample if the mass of the fully reconstructed vertex in the hypothesis D !.
- The range and width of the side-bands has been chosen to allow the subtraction of a linear background distribution and at the same time to minimize the statistical error of this subtraction.
- They were found to be compatible, so only the combined results are presented.
3 Momentum estimator
- As previously noted, the momenta of the charmed particles is not needed for the measurement of ; however, it is required for the determination of the other correlation variables.
- Thus it is necessary to have an estimator for the momentum of the partially reconstructed vertex which takes into account the unseen decay products.
- The charm momentum can be deduced imposing the charm mass: pD = D DMD: A comparison between these two methods and the simulation indicates that both methods give useful and independent information; however the rst method systematically underestimates the momentum while the second method systematically overestimates it.
- The optimal weights are acceptance dependent; for their experimental setup equal weights give a good result.
- The resulting fractional errors on the correlation variables are well below 10% over most of the range of their measurements.
4 Background subtraction and acceptances
- The invariant mass distribution for the fully reconstructed vertex is shown in Fig. 2a.
- Fitting the data mass distributions with a Gaussian peak above a linear background, the authors nd that the background in the signal region is 15% for both the 1992 and 1993 data sets.
- Comparison of the data and Monte Carlo distributions shows that the charm events with reconstruction errors account for all the background in this mass interval.
- 3 and 4, therefore acceptance corrections were evaluated by dividing each distribution of reconstructed events by the corresponding distribution of generated events.
5 Results
- 3 and 4 show the distributions of the charm correlation variables after back- ground subtraction and acceptance correction.
- Table 1 reports the mean values found by the present analysis for all measured correlation variables.
- The asymmetry in these distributions is thought to result from asymmetry in quark contents of the beam and target particle.
- The and p2T distributions are plotted in Fig. 3 along with the results of a model based on a NLO QCD calculation [22] which includes non-perturbative e ects such as hadronization and initial transverse momentum of the incident partons [23].
- Within the context of this model, no meaningful prediction is available for comparison with the data.
6 Conclusions
- This paper presents correlations observed in the WA92 experiment between two charmed particles produced in {Cu interactions at p s = 26GeV, where one of the charmed particles, which is fully reconstructed, has positive xF .
- The distributions observed are similar in shape and statistics to the previous highest statistics experiment.
- A comparison has been made between the and p2T distributions observed and a model based on NLO QCD.
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Citations
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CERN1
TL;DR: In this paper, the authors review the hadro-production data presently available on open charm and beauty absolute production cross-sections, collected by experiments at CERN, DESY and Fermilab.
129 citations
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TL;DR: In this article, the authors studied charmed meson production by 350 GeV/c π − particles incident on copper and tungsten targets at the CERN Ω′ spectrometer.
50 citations
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TL;DR: In this article, the results of charmonium production were compared with results on open-charm production, relating to the same experimental conditions, and the ratio between the J / ψ cross-section and the charmed-meson crosssection was found to be σ 0 (J/ψ)/σ 0 (D D − ) = 1.13 ± 0.01.
11 citations
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University of California, Davis1, CINVESTAV2, University of Colorado Boulder3, Fermilab4, Universidad de Guanajuato5, University of Illinois at Urbana–Champaign6, Indiana University7, Korea University8, Kyungpook National University9, University of Milan10, University of North Carolina at Chapel Hill11, University of Puerto Rico at Mayagüez12, University of South Carolina13, University of Tennessee14, Vanderbilt University15
TL;DR: In this article, a large sample of events containing fully and partially reconstructed pairs of charmed D mesons recorded by the Fermilab photoproduction experiment FOCUS (FNAL-E831) is presented.
9 citations
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TL;DR: This paper measured the azimuthal correlation between beauty particles, and compared their result with predictions based on perturbative QCD, using a sample of 108 triggered events, produced in 350 GeV /c π− interactions in a copper target.
7 citations
References
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CERN1
TL;DR: Pythia and JETSET as discussed by the authors are two main components of the “Lund Monte Carlo” program suite, and they can be used to generate high-energy-physics "events".
2,109 citations
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TL;DR: This work designs and implements a parser replacement for the FORTRAN 77 programming language, and demonstrates the power of the JETSET programming language.
972 citations
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TL;DR: In this paper, the origin of the observed scaling violations in the hadron spectra is investigated, and a simple parametrization for the heavy-quark fragmentation function is given which describes well recently measured charmed-meson spectra.
Abstract: The origin of the observed scaling violations in inclusive ${e}^{+}{e}^{\ensuremath{-}}$ annihilation is investigated. Perturbative jet evolution is not necessarily the only reason for scale breaking in the hadron spectra at present energies. Remnants of finite-transverse-momentum and mass effects are still important in nonperturbative, cascade-type, jet formation in the \ensuremath{\sim}10 GeV range. Heavy-quark fragmentation has a strong impact on hadronic inclusive spectra. A simple parametrization for the heavy-quark fragmentation function is given which describes well recently measured charmed-meson spectra. Taking these effects into account, good agreement with the observed scaling violations is obtained in cascade-type jet models with hard-gluon bremsstrahlung.
926 citations
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TL;DR: In this article, the authors presented a calculation of the fully exclusive parton cross sections for heavy-quark production at order O( α S 3 ) in QCD, where α is the number of quarks in the system.
590 citations