# A study of kinematical correlations between charmed particles produced in π-Cu interactions at √s = 26 GeV

Lebedev Physical Institute

^{1}, University of Genoa^{2}, University of Pisa^{3}, Imperial College London^{4}, University of Bologna^{5}, Sapienza University of Rome^{6}, CERN^{7}, University of Southampton^{8}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.

Did you find this useful? Give us your feedback

##### Citations

More filters

••

CERN

^{1}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

••

Lebedev Physical Institute

^{1}, University of Pisa^{2}, University of Geneva^{3}, Imperial College London^{4}, University of Bologna^{5}, CERN^{6}, Sapienza University of Rome^{7}, University of Southampton^{8}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

••

Lebedev Physical Institute

^{1}, University of Pisa^{2}, University of Genoa^{3}, Imperial College London^{4}, University of Bologna^{5}, CERN^{6}, Sapienza University of Rome^{7}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

••

University of California, Davis

^{1}, CINVESTAV^{2}, University of Colorado Boulder^{3}, Fermilab^{4}, Universidad de Guanajuato^{5}, University of Illinois at Urbana–Champaign^{6}, Indiana University^{7}, Korea University^{8}, Kyungpook National University^{9}, University of Milan^{10}, University of North Carolina at Chapel Hill^{11}, University of Puerto Rico at Mayagüez^{12}, University of South Carolina^{13}, University of Tennessee^{14}, Vanderbilt University^{15}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

••

Lebedev Physical Institute

^{1}, University of Pisa^{2}, University of Genoa^{3}, University of Bologna^{4}, Imperial College London^{5}, CERN^{6}, Sapienza University of Rome^{7}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

More filters

••

CERN

^{1}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

••

Lund University

^{1}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

••

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

••

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

••

473 citations