Heavy Hadron Chiral Perturbation Theory Research Articles

X(3872)as a molecularDD*state in a potential model

We discuss the possibility that the X(3872) can be a hadronic DD* bound state in the framework of a potential model. The potential is generated by the exchange of pseudoscalar, scalar and vector mesons resulting from the Lagrangian of heavy hadron chiral perturbation theory. The hadronic bound state configuration contains charged and neutral DD* components, while orbital S- and D-waves are included. Isospin symmetry breaking effects are fully taken into account. We show that binding in the DD* system with J(PC)=1(++) already exists for a reasonable value of the meson-exchange regularization parameter of Lambda around 1.2 GeV. We also explore the possibility of hadronic BB* bound states and show that binding can be achieved in the isoscalar limit for J(PC)=1(++) or 1(+-).

Hadronic decays of theX(3872)toχcJin effective field theory

The decays of the $X(3872)$ to $P$-wave quarkonia are calculated under the assumption that it is a shallow bound state of neutral charmed mesons. The $X(3872)$ is described using an effective theory of nonrelativistic $D$ mesons and pions (X-EFT). We calculate $X(3872)$ decays by first matching heavy hadron chiral perturbation theory ($\mathrm{HH}\ensuremath{\chi}\mathrm{PT}$) amplitudes for ${D}^{0}{\overline{D}}^{*0}\ensuremath{\rightarrow}{\ensuremath{\chi}}_{cJ}({\ensuremath{\pi}}^{0},\ensuremath{\pi}\ensuremath{\pi})$ onto local operators in X-EFT, and then using these operators to calculate the $X(3872)$ decays. This procedure reproduces the factorization theorems for $X(3872)$ decays to conventional quarkonia previously derived using the operator product expansion. For single pion decays, we find nontrivial dependence on the pion energy from $\mathrm{HH}\ensuremath{\chi}\mathrm{PT}$ diagrams with virtual $D$ mesons. This nontrivial energy dependence can potentially modify heavy-quark symmetry predictions for the relative sizes of decay rates. At leading order, decays to final states with two pions are dominated by the final state ${\ensuremath{\chi}}_{c1}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$, with a branching fraction just below that for the decay to ${\ensuremath{\chi}}_{c1}{\ensuremath{\pi}}^{0}$. Decays to all other final states with two pions are highly suppressed.

Puzzles of excited charm meson masses

We attempt a comprehensive analysis of the low lying charm meson states which present several puzzles, including the poor determination of masses of several non-strange excited mesons. We use the well-determined masses of the ground states and the strange first excited states to ‘predict’ the mass of the non-strange first excited state in the framework of heavy hadron chiral perturbation theory, an approach that is complementary to the well-known analysis of Mehen and Springer. This approach points to values for the masses of these states that are smaller than the experimental determinations. We provide a critical assessment of these mass measurements and point out the need for new experimental information.

Strong decays of charmed baryons in heavy hadron chiral perturbation theory

Strong decays of charmed baryons are analyzed in the framework of heavy hadron chiral perturbation theory (HHChPT) in which heavy quark symmetry and chiral symmetry are synthesized. HHChPT works excellently for describing the strong decays of $s$-wave charmed baryons. For $L=1$ orbitally excited states, two of the unknown couplings, namely, ${h}_{2}$ and ${h}_{10}$, are determined from the resonant ${\ensuremath{\Lambda}}_{c}^{+}\ensuremath{\pi}\ensuremath{\pi}$ mode produced in the ${\ensuremath{\Lambda}}_{c}(2593)$ decay and the width of ${\ensuremath{\Sigma}}_{c}(2800)$, respectively. Predictions for the strong decays of the $p$-wave charmed baryon states ${\ensuremath{\Lambda}}_{c}(2625)$, ${\ensuremath{\Xi}}_{c}(2790)$ and ${\ensuremath{\Xi}}_{c}(2815)$ are presented. Since the decay ${\ensuremath{\Lambda}}_{c}(2593{)}^{+}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}\ensuremath{\pi}\ensuremath{\pi}$ receives nonresonant contributions, our value for ${h}_{2}$ is smaller than the previous estimates. We also discuss the first positive-parity excited charmed baryons. We conjecture that the charmed baryon ${\ensuremath{\Lambda}}_{c}(2880)$ with ${J}^{P}=\frac{5}{2}\genfrac{}{}{0}{}{+}{}$ is an admixture of ${\ensuremath{\Lambda}}_{c2}(\frac{5}{2}\genfrac{}{}{0}{}{+}{})$ with an ${\stackrel{\texttildelow{}}{\ensuremath{\Lambda}}}_{c3}^{\ensuremath{'}\ensuremath{'}}(\frac{5}{2}\genfrac{}{}{0}{}{+}{})$; both are $L=2$ orbitally excited states. The potential model suggests ${J}^{P}=\frac{5}{2}\genfrac{}{}{0}{}{\ensuremath{-}}{}$ or $\frac{3}{2}\genfrac{}{}{0}{}{+}{}$ for ${\ensuremath{\Lambda}}_{c}(2940{)}^{+}$. Measurements of the ratio of ${\ensuremath{\Sigma}}_{c}^{*}\ensuremath{\pi}/{\ensuremath{\Sigma}}_{c}\ensuremath{\pi}$ will enable us to discriminate the ${J}^{P}$ assignments for ${\ensuremath{\Lambda}}_{c}(2940)$. We advocate that the ${J}^{P}$ quantum numbers of ${\ensuremath{\Xi}}_{c}(2980)$ and ${\ensuremath{\Xi}}_{c}(3077)$ are $\frac{1}{2}\genfrac{}{}{0}{}{+}{}$ and $\frac{5}{2}\genfrac{}{}{0}{}{+}{}$, respectively. Under this ${J}^{P}$ assignment, it is easy to understand why ${\ensuremath{\Xi}}_{c}(2980)$ is broader than ${\ensuremath{\Xi}}_{c}(3077)$.

Magnetic moments of heavy baryons in the relativistic three-quark model

The magnetic moments of ground state single, double and triple heavy baryons containing charm or bottom quarks are calculated in a relativistic three-quark model, which, in the heavy-quark limit, is consistent with heavy-quark effective theory and heavy hadron chiral perturbation theory. The internal quark structure of baryons is modeled by baryonic three-quark currents with a spin-flavor structure patterned according to standard covariant baryonic wave functions and currents used in QCD sum rule calculations.

Even- and odd-parity charmed meson masses in heavy hadron chiral perturbation theory

We derive mass formulae for the ground state, J^P = 0^- and 1^-, and first excited even-parity, J^P = 0^+ and 1^+, charmed mesons including one loop chiral corrections and O(1/m_c) counterterms in heavy hadron chiral perturbation theory. We show that including these counterterms is critical for fitting the current data. We find that certain parameter relations in the parity doubling model are not renormalized at one loop, providing a natural explanation for the equality of the hyperfine splittings of ground state and excited doublets.

Baryon electromagnetic properties in partially quenched heavy hadron chiral perturbation theory

The electromagnetic properties of baryons containing a heavy quark are calculated at next-to-leading order in partially quenched heavy hadron chiral perturbation theory. Calculations are performed for three light flavors in the isospin limit and additionally for two light nondegenerate flavors. We use partially quenched charge matrices that are easy to implement on the lattice. The results presented are necessary for the light-quark mass extrapolation and zero-momentum extrapolation of lattice QCD and partially quenched lattice QCD calculations of heavy hadron electromagnetic properties. Additionally relations between the sextet electromagnetic form factors and transition form factors are derived.

Baryon masses in partially quenched heavy hadron chiral perturbation theory

The masses of baryons containing a heavy quark are calculated to next-to-leading order in partially quenched heavy hadron chiral perturbation theory. Calculations are performed for three light flavors in the isospin limit and additionally for two light non-degenerate flavors. The results presented are necessary for extrapolating lattice QCD and partially quenched lattice QCD calculations of the heavy hadron masses.

Heavy-quark symmetry and the electromagnetic decays of excited charmed strange mesons

Heavy-hadron chiral perturbation theory (HH$\chi$PT) is applied to the decays of the even-parity charmed strange mesons, D_{s0}(2317) and D_{s1}(2460). Heavy-quark spin symmetry predicts the branching fractions for the three electromagnetic decays of these states to the ground states D_s and D_s^* in terms of a single parameter. The resulting predictions for two of the branching fractions are significantly higher than current upper limits from the CLEO experiment. Leading corrections to the branching ratios from chiral loop diagrams and spin-symmetry violating operators in the HH$\chi$PT Lagrangian can naturally account for this discrepancy. Finally the proposal that the D_{s0}(2317) (D_{s1}(2460)) is a hadronic bound state of a D (D^*) meson and a kaon is considered. Leading order predictions for electromagnetic branching ratios in this molecular scenario are in very poor agreement with existing data.

Heavy Baryons and electromagnetic decays

In this talk I review the theory of electromagnetic decays of the ground state baryon multiplets with one heavy quark calculated using Heavy Hadron Chiral Perturbation Theory [1]. The M1 and E2 amplitudes for S * → Sγ, S * → Tγ and S → Tγ are separately analyzed. All M1 transitions are calculated up to ???(1/Λ χ 2). The E2 amplitudes contribute at the same order for S * → Sγ, while for S * → Tγ they first appear at ???(1/( m Q Λ χ 2)) and for S → Tγ are completely negligible. Once the loop contributions is considered, relations among different decay amplitudes are derived. In ref. [1] it is shown that the coupling of the photon to light mesons is responsible of a sizable enhancement of these decay widths. Furthermore, one can obtain an absolute prediction for Γ(Ξ c 0′(*) → Ξ c 0γ) and Γ(Ξ b −′(*) → Ξ b −γ).

Electromagnetic decays of heavy baryons

The electromagnetic decays of the ground state baryon multiplets with one heavy quark are calculated using Heavy Hadron Chiral Perturbation Theory. The M1 and E2 amplitudes for S^{*}--> S gamma, S^{*} --> T gamma and S --> T gamma are separately computed. All M1 transitions are calculated up to O(1/Lambda_chi^2). The E2 amplitudes contribute at the same order for S^{*}--> S gamma, while for S^{*} --> T gamma they first appear at O(1/(m_Q \Lambda_\chi^2)) and for S --> T gamma are completely negligible. The renormalization of the chiral loops is discussed and relations among different decay amplitudes are derived. We find that chiral loops involving electromagnetic interactions of the light pseudoscalar mesons provide a sizable enhancement of these decay widths. Furthermore, we obtain an absolute prediction for the widths of Xi^{0'(*)}_c--> Xi^{0}_c gamma and Xi^{-'(*)}_b--> Xi^{-}_b gamma. Our results are compared to other estimates existing in the literature.

Magnetic moments of heavy baryons

The first nontrivial chiral corrections to the magnetic moments of triplet (T) and sextet ${(S}^{(*)})$ heavy baryons are calculated using heavy hadron chiral perturbation theory. Since magnetic moments of the T hadrons vanish in the limit of infinite heavy quark mass ${(m}_{Q}\ensuremath{\rightarrow}\ensuremath{\infty}),$ these corrections occur at order $\mathcal{O}({1/(m}_{Q}{\ensuremath{\Lambda}}_{\ensuremath{\chi}}^{2}))$ for T baryons, while for ${S}^{(*)}$ baryons they are of order $\mathcal{O}(1/{\ensuremath{\Lambda}}_{\ensuremath{\chi}}^{2}).$ The renormalization of the chiral loops is discussed, and relations among the magnetic moments of different hadrons are provided. Previous results for T baryons are revised.

MeasuringβinB→D(*)+D(*)−Ksdecays

We consider the possibility of measuring both $\sin (2 \beta)$ and $\cos (2 \beta)$ in the KM unitarity triangle using the process $B^0 \to D^{*+}D^{*-}K_s$. This decay mode has a higher branching fraction (O(1%)) than the mode $B^0 \to D^{*+}D^{*-}$. We use the factorization assumption and heavy hadron chiral perturbation theory to estimate the branching fraction and polarization. The time dependent rate for $B^0(t) \to D^{*+} D^{*-} K_s$ can be used to measure $\sin (2 \beta)$ and $\cos(2 \beta)$ . Furthermore, examination of the $D^{*+} K_s$ mass spectrum may be the best way to experimentally find the broad $1^+$ p-wave $D_s$ meson.

Non-perturbative effects in [formula omitted] for large dilepton invariant mass

We reconsider the calculation of ϕ( Λ QCD 2/ m b 2) non-perturbative corrections to B→ X Sl +l − decay. Our analysis confirms the results of Ali et al. for the dilepton invariant mass spectrum, which were in disagreement with an earlier publication, and for the lepton forward-backward asymmetry. We also give expressions for the ϕ( Λ QCD 2/ m b 2) corrections to the left-right asymmetry. In addition we discuss the breakdown of the heavy quark expansion near the point of maximal dilepton invariant mass q 2 and consider a model-independent approach to this region using heavy hadron chiral perturbation theory. The modes B → Kl +l − and B → Kπl +l − , which determine the endpoint region of the inclusive decay, are analyzed within this framework. An interpolation is suggested between the region of moderately high q 2, where the heavy quark expansion is still valid, and the vicinity of the endpoint described by chiral perturbation theory. We also comment on further non-perturbative effects in B→ X Sl +l − .

Predictions fors-wave andp-wave heavy baryons from sum rules and the constituent quark model: Strong interactions

We study the strong interactions of the L=1 orbitally excited baryons with one heavy quark in the framework of the Heavy Hadron Chiral Perturbation Theory. To leading order in the heavy mass expansion, the interaction Lagrangian describing the couplings of these states among themselves and with the ground state heavy baryons contains 46 unknown couplings. We derive sum rules analogous to the Adler-Weisberger sum rule which constrain these couplings and relate them to the couplings of the s-wave heavy baryons. Using a spin 3/2 baryon as a target, we find a sum rule expressing the deviation from the quark model prediction for pion couplings to s-wave states in terms of couplings of the p-wave states. In the constituent quark model these couplings are related and can be expressed in terms of only two reduced matrix elements. Using recent CLEO data on $\Sigma_c^{*}$ and $\Lambda_{c1}^+$ strong decays, we determine some of the unknown couplings in the chiral Lagrangian and the two quark model reduced matrix elements. Specific predictions are made for the decay properties of all L=1 charmed baryons.

Erratum: Decays of excited charmed Λ-type and Σ-type baryons in heavy hadron chiral perturbation theory [Phys. Rev. D 52, 3986 (1995)

Erratum: Decays of excited charmed Λ-type and Σ-type baryons in heavy hadron chiral perturbation theory [Phys. Rev. D 52, 3986 (1995)

Sum rules for radiative and strong decays of heavy mesons.

We derive two model-independent sum rules relating the transition matrix elements for radiative and strong decays of excited heavy mesons to properties of the lowest-lying heavy mesons. The sum rule for the radiative decays is an analog of the Cabibbo-Radicati sum rule and expresses the sum of the radiative widths in terms of the isovector charge radius of the ground state heavy meson. Using model-dependent estimates and heavy hadron chiral perturbation theory calculations, we show that this sum rule is close to saturation with states of excitation energies less than 1 GeV. An analog of the Adler-Weisberger sum rule gives an useful sum rule for the pionic widths of heavy excited mesons, which is used to set a model-independent upper bound on the coupling of the P-wave heavy mesons.

Theoretical update on two non-resonant three-body channels in charmed meson decays

Predictions of two channels in the three-body decays of the charmed mesons are made within heavy hadron chiral perturbation theory. There still exists the problem that the theoretical expectation is too small compared to experimental data.

Excited charmed baryon decays and their implications for fragmentation parameters.

The production of the excited charmed baryon doublet ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}^{\mathrm{*}}$ via fragmentation is studied. An analysis of the subsequent hadronic decays of the doublet within the framework of heavy hadron chiral perturbation theory produces expressions for both the angular distribution of the decay products and the polarization of the final state heavy baryon in terms of various nonperturbative fragmentation parameters. Future experimental investigation of this system will determine these parameters. In addition, recent experimental results are shown to fix one of the parameters in the heavy hadron chiral Lagrangian. \textcopyright{} 1996 The American Physical Society.

Decays of excited charmed Lambda -type and Sigma -type baryons in heavy hadron chiral perturbation theory.

Ground states and some excited p-wave states of heavy baryons are studied within the framework of heavy hadron chiral perturbation theory. The effective Lagrangian is written out to terms of the next-to-leading order in 1/${\mathit{m}}_{\mathit{Q}}$ or 1/${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{\ensuremath{\chi}}}$. The coupling constants are estimated using the experimental data of \ensuremath{\Lambda} and \ensuremath{\Sigma} baryons in the static limit of the s quark. The single pion and double pion decay rates of these charmed baryons have been estimated. The numerical results show that both ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}$(1/${2}^{\mathrm{\ensuremath{-}}}$) and ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}$(3/${2}^{\mathrm{\ensuremath{-}}}$) are very narrow. We conclude that the two pion channel may offer the best hope for detecting the ${\mathrm{\ensuremath{\Sigma}}}_{\mathit{c}}$(3/${2}^{\mathrm{\ensuremath{-}}}$) and ${\mathrm{\ensuremath{\Sigma}}}_{\mathit{c}}$(1/${2}^{\mathrm{\ensuremath{-}}}$) p-wave doublet.