Constituent Quark Meson Research Articles

SemileptonicBq→Dq*lν(q=s,d,u)decays in QCD sum rules

The form factors relevant to ${B}_{q}\ensuremath{\rightarrow}{D}_{q}^{*}({J}^{P}={1}^{\ensuremath{-}})\ensuremath{\ell}\ensuremath{\nu}$ ($q=s$, $d$, $u$) decays are calculated in the framework of the three point QCD sum rules approach. The heavy quark effective theory prediction of the form factors as well as $1/{m}_{b}$ corrections to those form factors are obtained. A comparison of the results for the ratio of form factors at zero recoil limit and other values of ${q}^{2}$ with the predictions of the subleading Isgur-Wise form factor application for $B\ensuremath{\rightarrow}{D}^{*}\ensuremath{\ell}\ensuremath{\nu}$ is presented. The total decay width and branching ratio for these decays are also evaluated using the ${q}^{2}$ dependencies of these form factors. The results are in good agreement with the constituent quark meson model and existing experimental data. The $q=s$ case can also be detected at LHC in the near future.

Study of semileptonic decays Bs → Ds1(2536)lν̄ and Bs → Ds2(2573)lν̄ in the CQM model**Supported by Natural Science Fund of Hebei Province (A2005000090,E2005000129), Fund of Education Department of Hebei Province (2007409) and Natural Science Fund of Hebei University (2005007)

Based on the assumption that Ds1(2536) and Ds2(2573) belong to T doublet (1+,2+), we calculate the semileptonic decays of Bs to Ds1(2536) and Ds2(2573) in terms of the Constituent Quark Meson (CQM) model. For Bs → Ds1(2536)+lν̄ and Bs → Ds2(2573)+lν̄, the order of magnitude of the obtained branching ratios is 10−3. Our numerical results of the semileptonic decays of Bs to Ds1(2536) and Ds2(2573) are large, which implies that two semileptonic decays should be seen in future experiments.

QCD sum rules study of the semileptonic [formula omitted] Decays

The form factors of the semileptonic B q → D q ( J P = 0 − ) ℓ ν with q = s , u , d transitions are calculated in the framework of three point QCD sum rules. Using the q 2 dependencies of the relevant form factors, the total decay width and the branching ratio for these decays are also evaluated. A comparison of our results for the form factors of B → D ℓ ν with the lattice QCD predictions within heavy quark effective theory and zero recoil limit is presented. Our results of the branching ratio are in good agreement with the constituent quark meson model for ( q = s , u , d ) and experiment for ( q = u , d ). The result of branching ratio for B s → D s ( 1968 ) ℓ ν indicates that this transition can also be detected at LHC in the near future.

Study of Bs→DsJ(2317,2460)lν̄ semileptonic decays in the CQM model

Assuming D* sJ(2317) and DsJ(2460) to be the (0+,1+) chiral partners of the regular particles Ds(1968) and D* s(2112), we calculate the semileptonic decays of Bs to Ds(1968), D* s(2112), DsJ *(2317) and DsJ(2460) in terms of the constituent quark meson model. The large branching ratios of the semileptonic decays of Bs to DsJ *(2317) and DsJ(2460) indicate that these two semileptonic decays should be seen in future experiments.

Study on decays of DsJ *(2317) and DsJ(2460) in terms of the CQM model

Based on the assumption that DsJ *(2317) and DsJ(2460) are the (0+,1+) chiral partners of Ds and D* s, we evaluate the strong pionic and radiative decays of DsJ *(2317) and DsJ(2460) in the constituent quark meson (CQM) model. Our numerical results of the relative ratios of the decay widths are reasonably consistent with the data.

Formula omitted] absorption in heavy-ion collisions

We present a new calculation of the π– J / ψ dissociation cross sections within the constituent quark–meson model recently introduced. To discuss the absorption of J / ψ in heavy-ion collisions, we assume the J / ψ to be produced inside a thermalized pion gas, as discussed by Bjorken, and introduce the corrections due to absorption by nuclear matter as well. We fit the absorption length of the J / ψ to the data obtained at the CERN SPS by the NA50 Collaboration for Pb–Pb collisions. Collisions of lower centrality allow us to determine the temperature and the energy density of the pion gas. For both these quantities we find values close to those indicated by lattice gauge calculations for the transition to a quark–gluon plasma. A simple extrapolation to more central collisions, which takes into account the increase of the energy deposited due to the increased nucleon flux, fails to reproduce the break in J / ψ absorption indicated by NA50, thus lending support to the idea that an unconfined quark–gluon phase may have been produced. This conclusion could be sharpened by analysing in a similar way, as a function of centrality, other observables such as strange particle production.

How can one understand the lightest scalars, especially the σ

We discuss how the a_0(980), f_0(980), K^*_0(1430) and particularly the broad sigma resonance can be understood within a coupled channel framework, which includes all light two-pseudoscalar thresholds together with constraints from Adler zeroes, flavour symmetric couplings, unitarity and physically acceptable analyticity. All (qbar q) scalars are, when unitarized, strongly distorted by hadronic mass shifts, and the nonstrange isoscalar state becomes a very broad resonance, with its pole at 470-i250 MeV. We believe this is the sigma meson required by models for spontaneous breaking of chiral symmetry. Recently this light resonance has clearly been observed in D-> sigma pi-> 3pi by the E791 experiment at Fermilab, and we discuss how this decay channel can be predicted in a Constituent Quark Meson Model (CQM), which incorporates heavy quark and chiral symmetries. We also discuss the less well known phenomenon that with a large coupling there can appear two physical resonance poles on the second sheet although only one bare quark-antiquark state is put in. The f_0(980) and f_0(1370) resonance poles can thus be two manifestations of the same (sbar s) quark state. Both of these states are seen clearly in D_s-> 3pi by the E791 experiment, where (sbar s) intermediate states are expected to be dominant.

The [formula omitted] and [formula omitted] nature of f0(980) in Ds decays

We examine the D s → f 0(980) π amplitude through a constituent quark–meson model, incorporating heavy quark and chiral symmetries, finding a good agreement with the recent E791 data analysis of D s →3 π via f 0(980). The f 0(980) resonance is considered at the moment of production as an s s ̄ state, later evolving to a superposition of mainly s s ̄ and K K ̄ . The analysis is also extended to the more frequent process D s → φπ.

Predicting D→ σπ

We examine the D→ σπ amplitude through a constituent quark–meson model, incorporating heavy quark and chiral symmetries, finding a good agreement with the recent E791 data analysis of D→3 π via σ.