D mesons

According to the method of phenomenological chiral Lagrangians (PCL s), this decay channel would originate via the intermediate D° — meson state (FIG. 2). In this case the weak interaction Lagrangian between (f) and D° mesons has the form given (Kalinovsky,1988) as... 

Figure 2. The diagram with the intermediate D° — meson, (S) anomalous strong-interection vertex.

As we have already seen, the first evidence for charm D meson production) came from analysing the Ktttt invariant mass produced in e e collisions above 4 GeV. The sharp narrow enhancement visible in the A 7r+7r+ exotic channel is absent in the non-exotic AT+tt+tt" channel (Fig. 13.9) and is convincing evidence that what is seen is indeed the decay of a i meson. 

By far the best way to study the D meson properties, however, is to analyse the decay of the l >i state of charmonium, the so-called "(3772) (see Chapter 11) whose mass lies less than 50 MeV/c above the DD threshold (so that the Ds move slowly) and is below the threshold for D production. This situation allows a very precise measurement of the mass from m = (E —p ) where E M n/2 is the energy of the beam which is known with only 1 MeV/c uncertainty. The momentum is very small, being so close to threshold (p ci 0.08(GeV/c) ) that any uncertainty in its value is irrelevant in the mass determination, whose resolution is then 3 MeV/c. The inveiriaiit mass spectra for various Kn combinations are shown in Fig. 13.10. 

Fig. 13.11. Decay angular distributions for neutral and charged D mesons. (Prom Schopper, 1977.)...

Figure 2.13. The difference between the reconstructed z position of the B decay vertex and the true position generated by the Monte Carlo for three important CP eigenstates a) b) — with each D meson seen in the Kirw channel, and c) 5° — 7r 7r .

Further topics of interest that can be studied at PEP-II include semileptonic decays of D s and the spectroscopy of D mesons. There are interesting predictions concerning the spins and decay patterns of excited D meson states [26] that result from the simplicity of a heavy quark - light quark bound state. In addition, charmed baryons will be copiously produced and their spectroscopy and decay patterns can be studied. The sample will be more than an order of magnitude larger than that currently available. 

After the discovery of the combined charge and space symmetry violation, or CP violation, in the decay of neutral mesons [2], the search for the EDMs of elementary particles has become one of the fundamental problems in physics. A permanent EDM is induced by the super-weak interactions that violate both space inversion symmetry and time reversal invariance [11], Considerable experimental efforts have been invested in probing for atomic EDMs (da) induced by EDMs of the proton, neutron, and electron, and by the P,T-odd interactions between them. The best available limit for the electron EDM, de, was obtained from atomic T1 experiments [12], which established an upper limit of de < 1.6 x 10 27e-cm. The benchmark upper limit on a nuclear EDM is obtained from the atomic EDM experiment on Iyt,Hg [13] as d ig < 2.1 x 10 2 e-cm, from which the best restriction on the proton EDM, dp < 5.4 x 10 24e-cm, was also obtained by Dmitriev and Senkov [14]. The previous upper limit on the proton EDM was estimated from the molecular T1F experiments by Hinds and co-workers [15]. 

Deser S., Goldberger M. L., Baumann K. and Thirring W. Energy Level Displacements in Pi-Mesonic Atoms, Phys. Rev. 96, 774-776 (1954) Anagnostopoulos D. F. et al., Precision measurements in pionic hydrogen, Nucl. Phys. A 721, 849-852 (2003). 

The second-order term can be interpreted as due to the interaction between two nucleons with the virtual excitation of a nucleon-antinucleon pair [17]. This interaction is a TBF with the exchange of a scalar (a) meson, as illustrated by the diagram (d) of Fig. 2. Actually this diagram represents a class of TBF with the exchange of light (7r, p) and heavy (a, u) mesons. There are, however, several other diagrams representing TBF, Fig. 2(a-c), which should be evaluated as well in a consistent treatment of TBF. 

The positive muon was discovered in cloud chamber photographs made by C D. Anderson and S.H. Neddermyer on Pike s Peak in 1935, and the negative muon almost simultaneously in cloud chamber photographs made by J.C. Street and E.C. Stevenson. These particles have long been called mu-mesons, but since they are fermions (spin h while all other mesons arc bosons, the name muon is preferred, as is their classification with the leptons because of their small rest mass, which is about 206 mr, where me is the mass of the electron. Another reason is their inability to interact with other particles through the nuclear forces. 

J. P. Vigier, M. Flato, D. and J. Sternheimer, and G. Wathaghin, On the masses on non-strange pseudo-scalar mesons and the generalized Klein-Gordon equation (1966). 

J. P. Vigier, Signification physique des potentiels vecteurs et abandon de la notion d invariance de jauge en theorie des mesons vectoriels intermediates, C. R. Acad. Sci. Paris 259 (1964). 

Amaldi, U. et al. (1987). Comprehensive analysis of data pertaining to the weak neutral current and the intermediate vector meson masses, Phys. Rev. D 36, 1385-1407. 

D. Fleming and M. Senba, in Perspectives of Meson Science, T. Yamazaki, K. Nakai and K. Nagamine, Eds., Elsevier, Amsterdam, 1992. 

Furthermore, we have investigated the influence that differences between different NN potentials have on nuclear structure predictions. It turns out that for potentials that fit the NN data reasonably well, on-shell differences have only a negligible effect. However, potentials that are essentially identical on-shell, may differ substantially off-shell. Such off-shell differences may lead to large differences in nuclear structure predictions. Relativistic, meson-theory based potentials (which are non-local) are in general weaker off-shell than their local counterparts. In particular, the weaker (off-shell) tensor force component (as quantified by a small deuteron D-state probability, Pd) leads to more binding in finite nuclei. For several examples shown, these predictions compare favourably with experiment. 

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