Excited Charm Mesons Research Articles

Production of orbitally excited charm mesons in c and b decays at LEP

A study of the production of L = 1 charmed mesons ( D ** states) has been performed using 4 million Z decays collected by the ALEPH detector at LEP. J P = 1 + states ( D 1 , D s l ) are observed in the decay channel D * π and D * K respectively, and the J P = 2 + states ( D * 2 ,D * 2 ) in the channels D* π , Dπ and DK respectively. Siince D ** states could originate from beauty hadron decay produced in Z 0 → bb or from charm fragmentation in Z 0 → cc events, rates are measured separately for b → D 1 , D * 2 , D s 1, D * 2 and c → D 1 , D * s2 , D s 1, D * s2 .

Production of P-wave charm and charm-strange mesons in hadronic Z $^0$ decays

Results are presented on the production of excited charm and excited charm-strange mesons in hadronic Z(0) decays. The results are obtained from approximately 4.3 million hadronic Z(0) decays, collected on or near the Z(0) resonance using the OPAL detector at LEP. The D-1(0)(2420) and D*(0)(2)(2460) mesons are reconstructed in the D*(+)pi(-) final state and their separate production rates in charm fragmentation and in weak decays of b-hadrons are determined. Assuming that the decay widths of these mesons are saturated by the allowed D*pi and D pi final states, the charm hadronization fractions and the inclusive branching ratios of b-hadrons to these neutral P-wave charm mesons are determined to bef(c --> D-1(0)) = 0.021 +/- 0.007(stat) +/- 0.003(syst), f(c --> D*(0)(2)) = 0.052 +/- 0.022(stat)+/- 0.013(syst), f(b --> D-1(0)) = 0.050 +/- 0.014(stat) +/- 0.006(syst), f(b --> D*(0)(2)) = 0.047 +/- 0.024(stat) +/- 0.013(syst).We also present the first observation at LEP of the D-s1(+)(2536) meson which is reconstructed in both the D*K-+(s)0 and D*K-0(+) final states After correcting for the expected contribution from bb events, assuming that the D*K channels saturate the available final states, these results are used to derive the charm hadronization fraction f(c --> D-s1(+)):f(c --> D-s1(+)) = 0.016 +/- 0.004(stat) +/- 0.003(syst).

Production of orbitally excited charm mesons in semileptonic B decays

A sample of 3.6 million hadronic Z decays recorded between 1991 and 1995 with the ALEPH detector at LEP is used to investigate semileptonic decays of B mesons into final states involving orbitally excited charm mesons. Topological vertex criteria are used to search for decays involving narrow D$^{**}$ states as well as wide D$^{**}$ resonances and non-resonant D$^{(*)}\pi$ final states. The sum of the branching ratios for these processes is measured to be \begin{eqnarray*} \lefteqn{{\mathrm{Br}}({\overline {\mathrm{B}}} \to {\mathrm{D}}\pi\ell^-\overline\nu) +{\mathrm{Br}}({\overline {\mathrm{B}}} \to {\mathrm{D}}^*\pi\ell^-\overline\nu)}\\ & & = (2.26\pm 0.29(\mathrm{stat}) \pm 0.33(\mathrm{syst}))\%, \end{eqnarray*} which accounts for a significant fraction of the deficit between inclusive measurements and the sum of exclusive semileptonic B decay modes.

Reconstruction of the decay B− → D10(2414) π −

We present the results of a partial reconstruction of the decay channel B − → D j (∗)π − performed using the ARGUS detector operating at the e + e − storage-ring DORIS II. In the context of this paper, D j (∗)0 is an L = 1 excited charm meson decaying to D ∗+π − . The measured product of branching ratios is Br(B − → D 1 0(2414)π −) · Br Br(D 1 0 → D ∗+π −) = (0.17 ± 0.05 ± 0.04)% where the first error is statistical and statistical and the second systematic. No evidence for the decay B − → D 2 ∗0 (2459) π −) · Br(D 2 ∗0 → D ∗+π −) < 0.07% at the 90% confidence level.

Semileptonic decays ofB mesons into excited charm mesons: Leading order and 1/m c contributions

We use the heavy quark effective theory to investigate the form factors that describe the semileptonic decays of aB meson into excited daughter mesons. For an excited daughter meson with charm, a single form factor is needed at leading order, while five form factors and two dimensionful constants are needed to order 1/m c in the heavy quark expansion. For non-charmed final states, a total of four form factors are needed at leading order. For the processB→D*Xlν, four form factors are also needed at leading order.

Excited charm mesons in semileptonic B-bar decay and their contributions to a Bjorken sum rule.

It has recently been shown that hadrons containing a single heavy quark exhibit a new flavor-spin symmetry of QCD. We exploit this symmetry to obtain model-independent predictions for the 14 form factors in weak decays from the ground-state pseudoscalar meson {ital P}{sub {ital Q}{ital i}} of a heavy quark {ital Q}{sub {ital i}} to the low-lying positive-parity excited states of a heavy quark {ital Q}{sub {ital j}} in terms of two universal functions of momentum transfer. These predictions are of interest in the study of {ital {bar B}}{r arrow}{ital D}{sub 2}{sup *}(2460), {ital D}{sub 1}(2420), {ital D}{sub 1}({similar to}2360), and {ital D}{sub 0}{sup *}({similar to}2360) semileptonic decays. We also discuss the connection between these results and the slope of the function {xi} (which determines the {ital {bar B}}{r arrow}{ital D} and {ital {bar B}}{r arrow}{ital D}{sup *} transition form factors) given by a heavy-quark sum rule suggested by Bjorken.