Heavy Hadron Chiral Perturbation Theory Research Articles

First measurements of the absolute branching fraction of Λc(2625)+→Λc+π+π− and upper limit on Λc(2595)+→Λc+π+π−

The absolute branching fraction of the decay Λc(2625)+→Λc+π+π− is measured for the first time to be (50.2±5.7stat±3.5syst)% with 368.48 pb−1 of e+e− collision data collected by the BESIII detector at the center-of-mass energies of s=4.918 and 4.950 GeV. Although the central value of the result is lower than the theoretical prediction of 67%, obtained from isospin symmetry, they are consistent taking the uncertainties into account. This is the first absolute branching fraction measurement for Λc(2625)+ since it was found. This measurement is necessary to obtain the coupling constants for the transitions between s-wave and p-wave charmed baryons in heavy hadron chiral perturbation theory. In addition, we search for the decay Λc(2595)+→Λc+π+π−. No significant signal is observed, and the upper limit on its branching fraction is determined to be 85.0% at the 90% confidence level. Published by the American Physical Society 2024

ALPs and heavy hadron chiral perturbation theory

ALPs and heavy hadron chiral perturbation theory

Radiative three-body D-meson decays in and beyond the standard model

We study radiative charm decays D rightarrow P_1 P_2 gamma , P_{1,2}=pi ,K in QCD factorization at leading order and within heavy hadron chiral perturbation theory. Branching ratios including resonance contributions are around sim 10^{-3} for the Cabibbo-favored modes into K pi gamma and sim 10^{-5} for the singly Cabibbo-suppressed modes into pi ^+ pi ^- gamma , K^+ K^- gamma , and thus in reach of the flavor factories BES III and Belle II. Dalitz plots and forward–backward asymmetries reveal significant differences between the two QCD frameworks; such observables are therefore ideally suited for a data-driven identification of relevant decay mechanisms in the standard-model dominated D rightarrow K pi gamma decays. This increases the potential to probe new physics with the D rightarrow pi ^+ pi ^- gamma and D rightarrow K^+ K^- gamma decays, which are sensitive to enhanced dipole operators. CP asymmetries are useful to test the SM and look for new physics in neutral |Delta C|=1 transitions. Cuts in the Dalitz plot enhance the sensitivity to new physics due to the presence of both s- and t, u-channel intermediate resonances.

Spectrum of Nonstrange Singly Charmed Baryons in the Constituent Quark Model

We study the masses of radial and orbital excited states of nonstrange singly charmed baryons in the framework of hypercentral Constituent Quark Model (hCQM). To obtain the mass spectra, the Coulomb plus screened potential is employed with the first order correction, which gives a relativistic effect of order $\cal{O}$$(1/m)$. The spin-spin, spin-orbit and tensor interactions are included (perturbatively as a spin dependent potential) in order to generate the splitting in mass spectra. We compare our computed mass spectra of nonstrange singly charmed baryons with the other theoretical predictions as well as with the experimental observations. We construct the Regge trajectories of these baryons in the $(J, M^2)$ plane. Further, we analyze the strong one pion decay rates for $S$, $P$ and the $D$-wave transitions in the framework of Heavy Hadron Chiral Perturbation Theory (HHChPT). Moreover, the electromagnetic properties like magnetic moments, transition magnetic moments and the radiative decay widths are determined for the ground state of these baryons in the constituent quark model.

Spectrum of strange singly charmed baryons in the constituent quark model

Excited states masses of the strange singly charmed baryons are calculated using the non-relativistic approach of hypercentral Constituent Quark Model (hCQM). The hyper-Coulomb plus screened potential is used as a confinement potential with the first order correction. The spin-spin, spin-orbit and spin-tensor interaction terms are included perturbatively. Our calculated masses are allowed to construct the Regge trajectories in both $(n_r, M^2)$ and $(J, M^2)$ planes. The mass spectra and the Regge trajectories study predict the spin-parity of $\Xi{_c(2970)^{+/0}}$, $\Xi{_c(3080)^{+/0}}$, $\Xi{_c(3123)^+}$, $\Omega{_c}(3000)^0$ and $\Omega{_c}(3119)^0$ baryons. Moreover, the strong one pion decay rates of the isodoublet states of $\Xi{_c(2645)}$, $\Xi{_c(2790)}$ and $\Xi{_c(2815)}$ are analyzed in the framework of Heavy Hadron Chiral Perturbation Theory (HHChPT). Also, the ground state magnetic moments and the radiative decay rates based on the transition magnetic moments are calculated in the framework of constituent quark model.

Hidden charm pentaquark states and ΣcD¯(*) interaction in chiral perturbation theory

In this work, we employ the heavy hadron chiral perturbation theory (HHChPT) to calculate the $\Sigma_c\bar{D}^{(*)}$ potentials to the next-to-leading order. The contact, the one-pion exchange and the two-pion exchange interactions are included. Besides, the mass splittings between the heavy quark spin symmetry (HQSS) multiplets are kept in calculations. Our result shows that neglecting the heavy quark symmetry (HQS) violation effect may be misleading to predict the potentials between the charmed hadrons. We perform numerical analysis with three scenarios. In the first scenario, we relate the low-energy constants (LECs) in the contact terms of $\Sigma_c\bar{D}^{(*)}$ to those of nucleon systems, and reproduce the $P_c(4312)$ and $P_c(4440)$ as loosely bound states. In the second scenario, we vary the unknown LECs and find a small parameter region in which $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ can coexist as molecular states. In the third scenario, we include the coupled-channel effect on the basis of scenario II, and notice that the three $P_c$ states can be reproduced as molecular states simultaneously in a large region of parameters. Our analytical results can be used for the chiral extrapolations in lattice QCD. With the lattice QCD results in the future as inputs, the identification of the $P_c$ states and predictions for other systems would be more reliable.

Quantum numbers of Ωc states and other charmed baryons

Possible spin-parity quantum numbers for excited charmed baryon resonances are discussed in this work. Our main results are: (i) Among the five newly observed $\Omega_c$ states, we have identified $\Omega_c(3090)$ and $\Omega_c(3119)$ with radially excited $\frac12^+(2S)$ and $\frac32^+(2S)$ states, respectively, and $\Omega_c(3000)$ with $\frac12^-(1P)$ and $S=\frac32$. The two states $\Omega_c(3050)$ and $\Omega_c(3066)$ form a $P$-wave $(\frac32^-,\frac52^-)$ doublet. (ii) The widths of $\Omega_c(3066)$ and $\Xi'_c(2930)$ are calculable within the framework of heavy hadron chiral perturbation theory. (iii) Since the width of $\Omega_{c0}(\frac12^-)$ is of order 410 MeV, not all observed narrow $\Omega_c$ baryons can be identified with $1P$ states. (iv) For the antitriplet $\Lambda_c$ and $\Xi_c$ states, their Regge trajectories for the orbital excitations of $\frac12^-$ and $\frac32^-$ are parallel to each other. Based on this nice property of parallelism, we see that the highest state $\Lambda_c(2940)$ does not fit if its quantum numbers are $\frac32^-$ as found by LHCb. We suggest that $\Lambda_c(2940)^+$ is most likely the $\frac12^-(2P)$ state. (v) The charmed baryon $\Sigma_c(2800)$ cannot be a $\frac12^-$ state; otherwise, its width will be over 400~MeV, too large compared to the measured one. (vi) In the study of Regge trajectories of $\Xi'_c$ states, we find a missing state. It should have quantum numbers $\frac52^-$ with a mass around 2920~MeV.

Mass spectra of heavy-light mesons in heavy hadron chiral perturbation theory

We study the masses of the low-lying charm and bottom mesons within the framework of heavy- hadron chiral perturbation theory (HHChPT). We work to third order in the chiral expansion, where meson loops contribute. In contrast to previous approaches, we use physical meson masses in evaluating these loops. This ensures that their imaginary parts are consistent with the observed widths of the D-mesons. The lowest odd- and even-parity, strange and nonstrange charm mesons provide enough constraints to determine only certain linear combinations of the low-energy constants (LECs) in the effective Lagrangian. We comment on how lattice QCD could provide further information to disentangle these constants. Then we use the results from the charm sector to predict the spectrum of odd- and even-parity of the bottom mesons. The predicted masses from our theory are in good agreement with experimentally measured masses for the case of the odd-parity sector. For the even-parity sector, the B-meson states have not yet been observed; thus, our results provide useful information for experimentalists investigating such states. The near degeneracy of nonstrange and strange scalar B mesons is confirmed in our predictions using HHChPT. We show why previous approaches of using HHChPT in studying the mass degeneracy in the scalar states of charm and bottom meson sectors gave unsatisfactory results.

χ cJ → e + e − decays revisited

We present a calculation of the width for $\chi_{cJ}\rightarrow e^{+}e^{-}$ decay. The amplitude of the process is computed within the NRQCD framework. The leading-order contribution is described by two terms associated with the two different integration domains in the electromagnetic loop describing two-photon annihilation of the heavy quark-antiquark pair. The corresponding operators are defined in the framework of NRQCD. The matrix element of one of these operators describes a configuration with an ultrasoft photon and can be associated with the higher Fock state of the heavy meson. In order to compute this contribution we use the heavy hadron chiral perturbation theory. We obtain that this contribution is numerically dominant. The obtained estimates for the decay widths of the $\chi_{c1}$ and $\chi_{c2}$ states are $0.09$ eV and $0.06$ eV, respectively.

Strong decays of charmed baryons in heavy hadron chiral perturbation theory: An update

We first give a brief overview of the charmed baryon spectroscopy and discuss their possible structure and spin-parity assignments in the quark model. With the new Belle measurement of the widths of $\Sigma_c(2455)$ and $\Sigma_c(2520)$ and the recent CDF measurement of the strong decays of $\Lambda_c(2595)$ and $\Lambda_c(2625)$, we give updated coupling constants in heavy hadron chiral perturbation theory. We find $g_2=0.565^{+0.011}_{-0.024}$ for $P$-wave transitions between $s$-wave and $s$-wave baryons, and $h_2$, one of the couplings responsible for $S$-wave transitions between $s$-wave and $p$-wave baryons, is extracted from $\Lambda_c(2595)^+\to\Lambda_c^+\pi\pi$ to be $0.63\pm0.07$. It is substantially enhanced compared to the old value of order 0.437. With the help from the quark model, two of the couplings $h_{10}$ and $h_{11}$ responsible for $D$-wave transitions between $s$-wave and $p$-wave baryons are determined from $\Sigma_c(2880)$ decays. There is a tension for the coupling $h_2$ as its value extracted from $\Lambda_c(2595)^+\to \Lambda_c^+\pi\pi$ will imply $\Xi_c(2790)^0\to\Xi'_c\pi$ and $\Xi_c(2815)^+\to\Xi_c^*\pi$ rates slightly above the current limits. It is conceivable that SU(3) flavor symmetry breaking can help account for the discrepancy.

Analysis of the vertices BsBK* and DsDK* with QCD Sum Rules

In this work, we calculated the form factors and coupling constant of the vertex DsDK* using the QCD Sum Rules. The calculation of the form factors were performed for the cases D, Ds and K* off shell. Using the similarities between B and D mesons, we also calculated the form factors and coupling constant of the vertex BsBK*. The coupling constants of the vertices BsBK* and DsDK* were compared with each other through the Heavy Hadron Chiral Perturbation Theory(HHChPT). We found a difference of 19% between BsBK* and DsDK* coupling constants using the HHChPT relation.

Matrix elements ofΔB=0operators in heavy hadron chiral perturbation theory

We study the light-quark mass and spatial volume dependence of the matrix elements of $\Delta B=0$ four-quark operators relevant for the determination of $V_{ub}$ and the lifetime ratios of single-$b$ hadrons. To this end, one-loop diagrams are computed in the framework of heavy hadron chiral perturbation theory with partially quenched formalism for three light-quark flavors in the isospin limit; flavor-connected and -disconnected diagrams are carefully analyzed. These calculations include the leading light-quark flavor and heavy-quark spin symmetry breaking effects in the heavy hadron spectrum. Our results can be used in the chiral extrapolation of lattice calculations of the matrix elements to the physical light-quark masses and to infinite volume. To provide insight on such chiral extrapolation, we evaluate the one-loop contributions to the matrix elements containing external $B_d$, $B_s$ mesons and $\Lambda_b$ baryon in the QCD limit, where sea and valence quark masses become equal. In particular, we find that the matrix elements of the $\lambda_3$ flavor-octet operators with external $B_d$ meson receive the contributions solely from connected diagrams in which current lattice techniques are capable of precise determination of the matrix elements. Finite volume effects are at most a few percent for typical lattice sizes and pion masses.

Mass degeneracy of heavy-light mesons with chiral partner structure in the half-Skyrmion phase

We explore the mass splitting of the heavy-light mesons with chiral partner structure in nuclear matter. In our calculation, we employed the heavy hadron chiral perturbation theory with chiral partner structure and the nuclear matter is constructed by putting skyrmions from the standard Skyrme model onto the face-centered cubic crystal and regarding the skyrmion matter as nuclear matter. We find that, although the masses of the heavy-light mesons with chiral partner structure are splitted in the matter-free space and skyrmion phase, they are degenerated in the half-skyrmion phase in which the chiral symmetry is restored globally. This observation suggests that the magnitude of the mass splitting of the heavy-light mesons with chiral partner structure can be used as a probe of the phase structure of the nuclear matter.

Charmed-baryon spectroscopy from lattice QCD withNf=2+1+1flavors

We present the results of a calculation of the positive-parity ground-state charmed-baryon spectrum using 2+1+1 flavors of dynamical quarks. The calculation uses a relativistic heavy-quark action for the valence charm quark, clover-Wilson fermions for the valence light and strange quarks, and HISQ sea quarks. The spectrum is calculated with a lightest pion mass around 220 MeV, and three lattice spacings (a \approx 0.12 fm, 0.09 fm, and 0.06 fm) are used to extrapolate to the continuum. The light-quark mass extrapolation is performed using heavy-hadron chiral perturbation theory up to O(m_pi^3) and at next-to-leading order in the heavy-quark mass. For the well-measured charmed baryons, our results show consistency with the experimental values. For the controversial J=1/2 Xi_{cc}, we obtain the isospin-averaged value M_{Xi_{cc}}=3595(39)(20)(6) MeV (the three uncertainties are statistics, fitting-window systematic, and systematics from other lattice artifacts, such as lattice scale setting and pion-mass determination), which shows a 1.7 sigma deviation from the experimental value. We predict the yet-to-be-discovered doubly and triply charmed baryons Xi_{cc}^*, Omega_{cc}, Omega_{cc}^* and Omega_{ccc} to have masses 3648(42)(18)(7) MeV, 3679(40)(17)(5) MeV, 3765(43)(17)(5) MeV and 4761(52)(21)(6) MeV, respectively.

Axial Couplings and Strong Decay Widths of Heavy Hadrons

We calculate the axial couplings of mesons and baryons containing a heavy quark in the static limit using lattice QCD. These couplings determine the leading interactions in heavy hadron chiral perturbation theory and are central quantities in heavy quark physics, as they control strong decay widths and the light quark mass dependence of heavy hadron observables. Our analysis makes use of lattice data at six different pion masses, 227 MeV<m(π)<352 MeV, two lattice spacings, a=0.085, 0.112 fm, and a volume of (2.7 fm)(3). Our results for the axial couplings are g(1)=0.449(51), g(2)=0.84(20), and g(3)=0.71(13), where g(1) governs the interaction between heavy-light mesons and pions and g(2,3) are similar couplings between heavy-light baryons and pions. Using our lattice result for g(3), and constraining 1/m(Q) corrections in the strong decay widths with experimental data for Σ(c)(*) decays, we obtain Γ[Σ(b)(*)→Λ(b)π(±)]=4.2(1.0), 4.8(1.1), 7.3(1.6), 7.8(1.8) MeV for the Σ(b)(+), Σ(b)(-), Σ(b)(*+), Σ(b)(*-) initial states, respectively. We also derive upper bounds on the widths of the Ξ(b)(I(*)) baryons.

Decay of theX(3872)intoχcJand the operator product expansion in effective field theory

XEFT is a low energy effective theory for the X(3872) that can be used to systematically analyze the decay and production of the X(3872) meson, assuming that it is a weakly bound state of charmed mesons. In a previous paper, we calculated the decays of X(3872) into \chi_{cJ} plus pions using a two-step procedure in which Heavy Hadron Chiral Perturbation Theory (HH\chiPT) amplitudes are matched onto XEFT operators and then X(3872) decay rates are then calculated using these operators. The procedure leads to IR divergences in the three-body decay X(3872) \to \chi_{cJ} \pi \pi when virtual D mesons can go on-shell in tree level HH\chiPT diagrams. In previous work, we regulated these IR divergences with the $D^{*0}$ width. In this work, we carefully analyze X(3872) \to \chi_{cJ} \pi^0 and X(3872) \to \chi_{cJ} \pi \pi using the operator product expansion (OPE) in XEFT. Forward scattering amplitudes in HH\chiPT are matched onto local operators in XEFT, the imaginary parts of which are responsible for the decay of the X(3872). Here we show that the IR divergences are regulated by the binding momentum of the X(3872) rather than the width of the D^{*0} meson. In the OPE, these IR divergences cancel in the calculation of the matching coefficients so the correct predictions for the X(3872) \to \chi_{c1} \pi \pi do not receive enhancements due to the width of the D^{*0}. We give updated predictions for the decay X(3872) \to \chi_{c1} \pi \pi at leading order in XEFT.

The role of charmed meson loops in charmonium decays

We investigate the effect of intermediate charmed meson loops on the M1 radiative decays $J/\psi \to \eta_c \gamma$ and $\psi'\rightarrow\eta^{(\prime)}_c\gamma$ as well as the isospin violating hadronic decays $\psi'\rightarrow J/\psi \,\pi^0(\eta)$ using heavy hadron chiral perturbation theory (HH$\chi$PT). The calculations include tree level as well as one loop diagrams and are compared to the latest data from CLEO and BES-III. Our fit constrains the couplings of 1S and 2S charmonium multiplets to charmed mesons, denoted $g_2$ and $g_2^\prime$, respectively. We find that there are two sets of solutions for $g_2$ and $g_2^\prime$. One set, which agrees with previous values of the product $g_2 g_2^\prime$ extracted from analyses that consider only loop contributions to $\psi'\rightarrow J/\psi \,\pi^0(\eta)$, can only fit data on radiative decays with fine-tuned cancellations between tree level diagrams and loops in that process. The other solution for $g_2$ and $g_2^\prime$ leads to couplings that are smaller by a factor of 2.3. In this case tree level and loop contributions are of comparable size and the numerical values of the tree level contributions to radiative decays are consistent with estimates based on the quark model as well as non-relativistic QCD (NRQCD). This result shows that tree level HH$\chi$PT couplings are as important as the one loop graphs with charmed mesons in these charmonium decays. The couplings $g_2$ and $g_2^\prime$ are also important for the calculations of the decays of charmed meson bound states, such as the X(3872), to conventional charmonia.

J/ψ production by magnetic excitation of ηc

We compute the probability of J/ψ production from the interaction between ηc and the strong magnetic field generated in relativistic heavy ion collisions. The computation is first carried out in the heavy quark effective model, in which the M1 radiative transition is considered. Then, we investigate the transition in the framework of non-relativistic heavy hadron chiral perturbation theory and show that the polarization of J/ψ produced by this process is parallel to the direction of magnetic field and thus perpendicular to the reaction plane. The transition probability obtained in both approaches is of order 2 × 10−4.

Axial couplings in heavy-hadron chiral perturbation theory at the next-to-leading order

We present calculations of axial-current matrix elements between various heavy-meson and heavy-baryon states to the next-to-leading order in heavy-hadron chiral perturbation theory in the $p$-regime. When compared with data from lattice computations or experiments, these results can be used to determine the axial couplings in the chiral Lagrangian. Our calculation is performed in partially quenched chiral perturbation theory for both $\mathrm{SU}(4|2)$ and $\mathrm{SU}(6|3)$. We incorporate finite-size effects arising from a single Goldstone meson wrapping around the spatial volume. Results for full QCD with two and three flavors can be obtained straightforwardly by taking the sea-quark masses to be equal to the valence-quark masses. To illustrate the impact of our chiral perturbation theory calculation on lattice computations, we analyze the SU(2) full-QCD results in detail. We also study one-loop contributions relevant to the heavy-hadron strong-decay amplitudes involving final-state Goldstone bosons, and demonstrate that the quark-mass dependence of these amplitudes can be significantly different from that of the axial-current matrix elements containing only single-hadron external states.

Radiative decaysX(3872)→ψ(2S)γandψ(4040)→X(3872)γin effective field theory

Heavy hadron chiral perturbation theory (HHchiPT) and XEFT are applied to the decays X(3872) -> psi(2S) + gamma and psi(4040) -> X(3872) + gamma under the assumption that the X(3872) is a molecular bound state of neutral charm mesons. In these decays the emitted photon energies are 181 MeV and 165 MeV, respectively, so HHchiPT can be used to calculate the underlying D^0 bar{D}^{0*}+ bar{D}^0 D^{0*} -> psi(2S) + gamma or psi(4040) -> (D^0 bar{D}^{0*}+ bar{D}^0 D^{0*}) + gamma transition. These amplitudes are matched onto XEFT to obtain decay rates. The decays receive contributions from both long distance and short distance processes. We study the polarization of the psi(2S) in the decay X(3872) -> psi(2S) + gamma and the angular distribution of X(3872) in the decay psi(4040) -> X(3872) + gamma and find they can be used to differentiate between different decay mechanisms as well as discriminate between 2^{-+} and 1^{++} quantum number assignments of the X(3872).