Search results for "meson"
showing 10 items of 1548 documents
Meson-baryon threshold effects in the light-quark baryon spectrum
2008
We argue that selected $S$ wave meson-baryon channels may play a key role to match poor baryon mass predictions from quark models with data. The identification of these channels with effective inelastic channels in data analysis allows to derive a prescription which could improve the extraction and identification of baryon resonances.
T-odd and CP-odd triple momentum correlations in the exclusive semi-leptonic bottom meson decay
1990
Abstract We study T-odd triple momentum correlations in exclusive semi-leptonic (S l ) bottom meson decays B → D ∗ (→ D π)+ l +ν l . We define asymmetry ratios that measure these T-odd triple momentum correlation effects. We provide a careful discussion of possible unitarity contributions to the asymmetry ratios. The conclusion is that strong interaction unitarity contributions are small or, in the case of one particular T-odd observable, absent. CP-violating contributions to the asymmetry ratios would have to come from new non-standard sources as there are no standard model contributions. Possible new CP-violating contributions are parametrized in terms of an effective four-fermion hamilto…
Measurement of $B_d$ mixing using opposite-side flavor tagging
2006
We report on a measurement of the $B^0_d$ mixing frequency and the calibration of an opposite-side flavor tagger in the D{\O}experiment. Various properties associated with the $b$ quark on the opposite side of the reconstructed $B$ meson were combined using a likelihood-ratio method into a single variable with enhanced tagging power. Its performance was tested with data, using a large sample of reconstructed semileptonic $B \to \mu \dzero X$ and $B \to \mu \dst X$ decays, corresponding to an integrated luminosity of approximately 1 fb$^{-1}$. The events were divided into groups depending on the value of the combined tagging variable, and an independent analysis was performed in each group. …
Chiral SU(3) Bethe Salpeter Model: Extension to SU(6) and SU(8) Spin-Flavor Symmetries
2008
Consistent SU(6) and SU(8) spin-flavor extensions of the SU(3) flavor Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian are constructed, which incorporate vector meson degrees of freedom. In the charmless sector, the on-shell approximation to the Bethe-Salpeter (BS) approach successfully reproduces previous SU(3) WT results for the lowest-lying s--wave negative parity baryon resonances. It also provides some information on the dynamics of heavier ones and of the lightest d-wave negative parity resonances, as e.g. the Lambda(1520). For charmed baryons the scheme is consistent with heavy quark symmetry, and our preliminary results in the strangeness-less charm C=+1 sector describe the mai…
Open-charm meson spectroscopy
2006
We present a theoretical framework that accounts for the new $D_J$ and $D_{sJ}$ mesons measured in the open-charm sector. These resonances are properly described if considered as a mixture of conventional $P-$wave quark-antiquark states and four-quark components. The narrowest states are basically $P-$wave quark-antiquark mesons, while the dominantly four-quark states are shifted above the corresponding two-meson threshold, being broad resonances. We study the electromagnetic decay widths as basic tools to scrutiny their nature. The proposed explanation incorporates in a natural way the most recently discovered mesons in charmonium spectroscopy.
Deeply virtual electroproduction of photons and mesons on the nucleon : leading order amplitudes and power corrections
1999
We estimate the leading order amplitudes for exclusive photon and meson electroproduction reactions at large Q^2 in the valence region in terms of skewed quark distributions. As experimental investigations can currently only be envisaged at moderate values of Q^2, we estimate power corrections due to the intrinsic transverse momentum of the partons in the meson wavefunction and in the nucleon. To this aim the skewed parton distribution formalism is generalized so as to include the parton intrinsic transverse momentum dependence. Furthermore, for the meson electroproduction reactions, we calculate the soft overlap type contributions and compare with the leading order amplitudes. We give firs…
Tree-level flavor-changing neutral currents in theBsystem: FromCPasymmetries to rare decays
2001
corresponding to 0.59 ≤ sin(2�) ≤ 0.82, which is cer- tainly outside the 1� Babar range but not outside the world average. This potential discrepancy is at the ori- gin of several papers (6) studying the implications of a small aJ/ in the search of new physics. In this paper, we analyze the implications of this situ- ation for a realistic model, obtained with the only addi- tion of an isosinglet down vector-like quark (7) to the SM spectrum. This model naturally arises, for instance, as the low-energy limit of an E6 grand unified theory. At a more phenomenological level, models with isosinglet quarks provide the simplest self-consistent framework to study deviations of 3 ×3 unitarity of the…
Geometrical volume effects in the computation of the slope of the isgur-wise function
1994
We use a method recently suggested for evaluating the slope of the Isgur-Wise function, at the zero-recoil point, on the lattice. The computations are performed in the quenched approximation to lattice QCD, on a $24^3 \times 48$ lattice at $\beta=6.2$, using an $O(a)$-improved action for the fermions. We have found unexpectedly large finite-volume effects in such a calculation. These volume corrections turned out to be purely geometrical and independent of the dynamics of the system. After the study of these effects on a smaller volume and for different quark masses, we give approximate expressions that account for them. Using these approximations we find $\xi^\prime(1)=-1.7 \pm 0.2$ and $\…
Azimuthal correlations of electrons from heavy-flavor decay with hadrons inp+pand Au+Au collisions atsNN=200GeV
2011
Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled p+p collisions. These measurements indicate that charm and bottom quarks interact with the hot dense matter produced in heavy-ion collisions much more than expected. Here we extend these studies to two-particle correlations where one particle is an electron from the decay of a heavy-flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interactions between heavy quarks and the matter, such as whet…
Covariant trace formalism for heavy mesons-wave top-wave transitions
1993
Heavy meson,s- top-wave, weakb→c transitions are studied in the context of the heavy quark effective theory using covariant meson wave functions. We use the trace formalism to evaluate the weak transitions. As expected from heavy quark symmetry, the eight transitions betweens- andp-wave states are described in terms of only two universal form factors which are given in terms of explicit wave function overlap integrals. We present our results in terms of both invariant and helicity amplitudes. Using our helicity amplitude expressions we discuss rate formulae, helicity structure functions and joint angular decay distributions in the decays $$\bar B \to D^{**} ( \to (D,D^* ) + \pi ) + W^ - ( \…