Projects / Programmes
Measurement of the absolute branching fractions of leptonic D(s) decays and the extraction of the decay constant f_D(s)
| Code |
Science |
Field |
Subfield |
| 1.02.06 |
Natural sciences and mathematics |
Physics |
Experimental physics of elementary particles |
| Code |
Science |
Field |
| P210 |
Natural sciences and mathematics |
Elementary particle physics, quantum field theory |
| Code |
Science |
Field |
| 1.03 |
Natural Sciences |
Physical sciences |
Charmed mesons, leptonic and semileptonic decays, lattice QCD calculations
Researchers (1)
| no. |
Code |
Name and surname |
Research area |
Role |
Period |
No. of publicationsNo. of publications |
| 1. |
25620 |
PhD Anže Zupanc |
Physics |
Head |
2011 - 2013 |
349 |
Organisations (1)
| no. |
Code |
Research organisation |
City |
Registration number |
No. of publicationsNo. of publications |
| 1. |
0106 |
Jožef Stefan Institute |
Ljubljana |
5051606000 |
90,753 |
Abstract
The aim of the proposed project is to measure D and Ds meson decay constants, f_D and f_Ds, respectively, by measuring the absolute branching fraction of leptonic decays of D mesons to mu nu_mu and Ds mesons to mu nu_mu and tau nu_tau. The measurements will be performed using a data sample corresponding to an integrated luminosity of 1020 fb^-1, collected at the center-of-mass energies near 10.58 GeV with the Belle detector at the KEKB positron-electron collider in Tsukuba, Japan. In the first step of the measurement, an inclusive sample of D(s) mesons is obtained by reconstructing the rest of the event in reactions of the kind e+e- › cc › DKXD(s)*, where D(s)* decays to D and a neutral pion or Ds and a photon. Here, D represents a charmed hadron, K a charged or neutral kaon, and X any number of pions produced in the fragmentation process. The DKX system is fully reconstructed but no requirements are imposed on the decay products of the D(s) so that the selected events correspond to an inclusive sample and can be used for normalization. In the second step, a single muon or tau decay products are required in order to obtain the absolute branching fraction of studied leptonic decays. The D(s) meson decay constants can be at the end extracted from the measured branching ratios of leptonic decays, since they are proportional to the meson decay constant squared. The measured values of the meson decay constants can then be compared to precise theoretical calculations obtained within the Standard model of elementary particles and their interactions. Currently, all experimental measurements of f_Ds are above the most precise theoretical calculation; however, the precision of the experimental determinations is not good enough to make any strong conclusions. More precise experimental determinations of f_Ds are therefore needed to allow for more stringent tests of the Standard model predictions. If the discrepancy between experiment and theory is not resolved, this could point to the existence of particles and processes not included in the Standard model, such as a two-Higgs doublet or leptoquarks. The world average value of D meson decay constant is basically dominated by a single measurement performed by the Cleo-c collaboration, which is, however, in agreement with theoretical predictions within their uncertainties. It is important to validate the results of this measurement and perform it in a different environment and with a different detector. The proposed measurements of D and Ds meson decay constants would have a significant impact on the world average values and provide more stringent tests of the Standard Model.
Significance for science
In order to extract fundamental parameters of any theory of elementary particles and interactions between them we need to use predictions and calculations on the lattice of effects of quantum chromodynamics. These theoretical calculations need to be thoroughly tested by as many experimental observables as possible. Precise measurement of D_s+ meson decay constant enables such tests to be performed. In addition, the measurement enables to constrain possible values of the parameters included in models that describe the processes and particles beyond the currently verified Standard Model of particles and interactions among them. The measured values of branching fractions of hadronic D_s+ meson adn Lambda_c+ baryond decays will enable more precise measurements of various b-quark hadrons to be performed at the large hadron collider LHC at CERN.
Significance for the country
While the direct influence of the basic research on the development is difficult to estimate, some of the tools and methods used in this project can be applied to the outside purelz scientific fields. An example are the Grid computing technology and data mining. To successfully finish the project we have used a local computing cluster that is a part of the Belle virtual organization. Currently the computing cluster is in the process of upgrade to a center that will be exploited for the analysis of data collected with the Belle II detector. Data mining techniques used in this project are as well more and more often used in the information technology industry. Probably even more important impact arises from the continuing involvement in the cutting-edge research efforts and technology used in the experiments, where the accumulated knowledge is transferred to students through the pedagogical work at university (in form of seminars, bachelor and master thesis or PhD research). Last but not least, state of the art scientific results represent a promotion of Slovenia through regular contacts among worldwide community of scientists at the international conferences, within the international Belle collaboration and through publication of papers in the international scientific journals.
Most important scientific results
Annual report
2011,
2012,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Final report,
complete report on dLib.si
