For three-body hadron decays mediated by intermediate resonances with large widths, we show how to properly extract the quasi-two-body decay rates for a meaningful comparison with the corresponding theoretical estimates, using several $B$ decays as explicit examples. We compute the correction factor from finite width effects in the QCD factorization approach, and make a comparison with that using the experimental parameterization in which the momentum dependence in the weak dynamics is absent. Although the difference is generally less than $10\%$ for tensor and vector resonances, it can be as large as $(25-40)\%$ for scalar resonances. Our finding can in fact be applied to general quasi-two-body decays.
In the context of the Standard Model (SM) of particle physics, the relationship between the top-quark mass and width ($Γ_t$) has been precisely calculated. However, the uncertainty from current direct measurements of the width is nearly 50%. A new approach for directly measuring the top-quark width using events away from the resonance peak is presented. By using an orthogonal dataset to traditional top-quark width extractions, this new method may enable significant improvements in the experimental sensitivity in a method combination. Recasting a recent ATLAS differential cross section measurem…
Though top quark was discovered more than twenty years ago, measurement of its width is still challenging task. Most measurements either have rather low precision or they are done in assumption of the SM top quark interactions. We consider model independent parametrization of the top quark width and provide estimations on achievable accuracy using a combination of fiducial cross sections in double, single and non-resonant regions.
In this work, we study the ($S$, $P$ and $D$)-wave $K^+K^-$ contributions to $B\to KKK$ decays in the perturbative QCD approach at leading order. Within the two-meson wave functions describing the nonperturbative dynamics in the kaon-pair for different waves, we calculate the branching fractions and the direct $CP$ asymmetries of these decay modes in the corresponding resonance regions. Most of our numerical results are well consistent with the current measurements. We note that the narrow-width approximation is invalid in the quasi-two-body decays $B\to Kf_0(980)\to KKK$. For other decays, un…
We introduce the differential and the total decay widths of a resonant (Gamow) state decaying into a continuum of stable states. When the resonance has several decay modes, we introduce the corresponding partial decay widths and branching fractions. In the approximation that the resonance is sharp, the expressions for the differential, partial and total decay widths of a resonant state bear a close resemblance with the Golden Rule. In such approximation, the branching fractions of a resonant state are the same as the standard branching fractions obtained by way of the Golden Rule. We also intr…
This letter details and discusses the next-to-leading order QCD corrections to $t$-channel electro-weak $W^+ b j$ production, where finite top-width effects are consistently taken into account. The computation is done within the aMC@NLO framework and includes both resonant and non-resonant contributions as well as interferences between the two. Results are presented for the LHC and compared to those of the narrow-width approximation and effective theory approaches.
The cross sections of e+e- to pi+pi-h_c at center-of-mass energies from 3.90 to 4.42 GeV were measured by the BESIII and the CLEO-c experiments. Resonant structures are evident in the e+e- to pi+pi-h_c line shape, the fit to the line shape results in a narrow structure at a mass of (4216\pm 18) MeV/c^2 and a width of (39\pm 32) MeV, and a possible wide structure of mass (4293\pm 9) MeV/c^2 and width (222\pm 67) MeV. Here the errors are combined statistical and systematic errors. This may indicate that the Y(4260) state observed in e+e- to pi+pi-J/psi has fine structure in it.
The vector charmoniumlike state $Y(4220)$ was reported recently in the cross sections of $e^+e^-\to ωχ_{c0}$, $π^+π^-h_c$, $π^+π^- J/ψ$, and $D^0 D^{*-}π^+ + c.c.$ measured by the BESIII experiment. A combined fit is performed to the cross sections of these four final states to extract the resonant parameters of the $Y(4220)$. We determine a mass $M=(4219.6\pm 3.3\pm 5.1)$~MeV/$c^2$ and a total width $Γ=(56.0\pm 3.6\pm 6.9)$~MeV for the $Y(4220)$, where the first uncertainties are statistical and the second ones systematic. Assuming the $Y(4220)$ decays dominantly to the above four modes and t…
Searches of lepton-number violation in different processes are very useful to constrain the parameter space of Majorana neutrinos. Here we use available upper bounds on the branching fractions of B^- -> D^0pi^+mu^-mu^- and D^0 -> (pi^-pi^-/K^-pi^-) mu^-mu^- decays to derive constraints on the mass and mixings of Majorana neutrinos by assuming they are produced resonantly in these four-body decays. While the excluded region obtained from B^- decays are competitive with existing limits from three-body D^- and B^- decays, it is shown that experimental improvements on D^0 decays offer a good poten…
In this work, we study the $S$, $P$ and $D$ wave resonance contributions to three-body decays $B_{(s)} \to [ D^{(*)}, \bar{D}^{(*)} ] K^+K^-$ by employing the perturbative QCD (PQCD) approach, where the kaon-kaon invariant mass spectra are dominated by the $f_0(980),f_0(1370),$ $ϕ(1020),ϕ(1680),f_2(1270),f^{\prime}_2(1525),f_2(1750)$ and $f_2(1950)$ resonances. The $KK$ $S$-wave component $f_0(980)$ is modeled with the Flatté formalism, while other resonances are described by the relativistic Breit-Wigner (BW) line shape. The corresponding decay channels are studied by constructing the kaon-ka…
We calculate the mass spectrum of the $S$-wave fully-charmed tetraquark resonant states $cc\bar c\bar c $ in the nonrelativistic quark model, which successfully describes the charmonium spectrum. The four-body system is solved with the Gaussian expansion method. The complex scaling technique is used to identify the genuine resonances. With the nonrelativistic quark model, our results show the existence of two $cc\bar c\bar c$ resonances in each of the $J^{PC}=$ $0^{++}$, $1^{+-}$ and $2^{++}$ sectors, respectively. In the $S$-wave sector, no resonance is found at the energy region of the $X(62…
Two-body decay widths of lowest lying and next-to-lowest lying scalar and pseudoscalar mesons are studied in Generalized Linear Sigma Model (GLSM) of low-energy QCD. This model which considers mixing between "two quark" and "four quark" chiral nonets has been employed to investigate various decays and scatterings in low energy region of QCD. In this paper, $Γ[f_0(980) \rightarrow K \bar{K}]$ and $Γ[a_0(980) \rightarrow K \bar{K}]$ are obtained and it is shown that two-body decay widths of lowest lying mesons are well predicted by this model while for the next-to-lowest lying mesons, only some …
We calculate the branching ratio of the non-resonant $B \to D^- π^+π^+π^- $ decay using a simple model based on the framework of the factorization approach. In naive factorization approach, there are only tow tree diagrams for this decay mode. In the first diagram, the matrix element of decay mode is factorized into a $B\to D$ form factor multiplied by a $3π$ decay constant and in the second diagram, the matrix element is factorized into a $B\to Dπ$ form factor multiplied by a $2π$ decay constant, We assume that in the rest frame of B meson, the $D$ meson remains stationary, so we obtain the v…
We study the width of a two-body resonance in a coupled-channel system. We demonstrate how the width does not come only determined by the available phase space for its decay to the detection channel, but it greatly depends on the relative position of the mass of the resonance with respect to the masses of the coupled-channels generating the state. Our results are consistent with the experimental observation of narrow hadrons lying well above their lowest decay threshold.
In Phys. Rev. Lett. 102, 091804 (2009) [arXiv:0903.0787], R.S. Raghavan claims that due to motional averaging by lattice vibrations, 18.6 keV electron antineutrinos emitted/captured without recoil from 2-body decay in the 3H/3He system embedded in Nb metal will be observable with natural width. In this comment we argue that 1) stochastic relaxation processes and 2) inhomogeneities in the metal matrices will prevent the generation of antineutrinos with natural width in the 3H/3He system, 3) the different lattice-deformation energies of 3H and 3He in the Nb matrix will drastically decrease the f…
We find new and universal relations for the properties of dark matter particles consistent with standard relic abundances. Analysis is based on first characterizing the $s$-channel resonant annihilation process in great detail, keeping track of all velocity-dependence, the presence of multiple scales and treating each physical regime above, below, and close to thresholds separately. The resonant regime as well as extension to include non-resonant processes are then reduced to analytic formulas and inequalities that describe the full range of multi-dimensional numerical work. These results elim…
Many newly discovered excited states are interpreted as bound states of hadrons. Can these hadrons also form resonant states? In this paper, we extend the complex scaling method (CSM) to calculate the bound state and resonant state consistently for the $Λ_c D(\bar D)$ and $Λ_c Λ_c (\bar Λ_c)$ systems. For these systems, the $π, η, ρ$ meson exchange contributions are suppressed, the contributions of intermediate- and short-range forces from $σ/ω$ exchange are dominant. Our results indicate that $Λ_c D$ system can not form bound state and resonant state. There exist resonant states in a wide ran…
It has been recently reported an intriguing theoretical result of a narrow three-body resonance with a large available phase space. The resonance was reported in the $NΛΛ-ΞNN$ system near the $Ξd$ threshold, having a very small width in spite of the open $NΛΛ$ channel lying around 23 MeV below the $ΞNN$ channel. We use first-order perturbation theory as a plausible argument to explain this behavior. We apply our result to realistic local interactions. Other systems involving several thresholds are likely to follow the same behavior.
We interest to investigate of the three-body decays of $B^{0}$ meson to $ ϕπ^+π^- $ and $B_s^{0}$ meson to $ ϕπ^{+}π^{-}$. Hadronic three-body decays include both nonresonant and resonant contributions, on the basis of the factorization hypothesis. In this analysis, resonant structure is exhibited only in the $ π^+π^-$ channel which the resonant contribution can be described by S-wave, P-wave and D-wave $ π^+π^-$ contribution from $ f_0(980)$, $ ρ$ and $f_2$ mesons and other possible resonance. Therefore, the theoretical values at the scale $ m_b$ are $(1.69 \pm 0.19 )\times10^{-7}$ and $(3.28…
In the present work we study possible time dependent effects in Axion Dark Matter searches employing resonant cavities. We find that the width of the resonance, which depends on the axion mean square velocity in the local frame, will show an annual variation due to the motion of the Earth around the sun (modulation). Furthermore, if the experiments become directional, employing suitable resonant cavities, one expects large asymmetries in the observed widths relative to the sun's direction of motion. Due to the rotation of the Earth around its axis, these asymmetries will manifest themselves as…
We study the leptoquark model of Buchmüller, Rückl and Wyler, focusing on a particular type of scalar ($R_2$) and vector ($U_1$) leptoquark. The primary aim is to perform the calculations for leptoquark production and decay at next-to-leading order (NLO) to establish the importance of the NLO contributions and, in particular, to determine how effective the narrow-width-approximation (NWA) is at NLO. For both the scalar and vector leptoquarks it is found that the NLO contributions are large, with the larger corrections occurring for the case vector leptoquarks. For the scalar leptoquark it is f…
We express the resonant energies of the delta-shell potential in terms of the Lambert $W$ function, and we calculate their decay widths and decay constants. The ensuing numerical results strengthen the interpretation of such decay widths and constants as a way to quantify the coupling between a resonance and the continuum. We calculate explicitly the decay energy spectrum of the resonances of the delta-shell potential, and we show numerically that the lineshape of such spectrum is not the same as, and can be very different from, the Breit-Wigner (Lorentzian) distribution. We argue that the sta…
It is rare for an $S$-wave resonance to remain narrow while approaching threshold as a result of the interaction parameters being fine tuned. Such an interaction is, however, realized by pion-charmed baryon system $πΣ_c$, which has a narrow resonance $Λ_c^+(2595)$ located a few MeVs above its threshold. We study the consequence of narrowly resonant inter-species interaction in a three-body system composed of two identical light bosons and an extremely heavy particle. We concern ourselves in the present paper with resonances of the three-body system, as opposed to bound states. The focus is on …
Resonant P-wave interactions can be described by a minimal zero-range model defined by a truncated effective range expansion, so that the only 2-body interaction parameters are the inverse scattering volume 1/a_P and the P-wave effective range r_P. This minimal model can be formulated as a local quantum field theory with a P-wave interaction between atom fields and a molecular field. In the two-atom sector, the model is renormalizable, but it has unphysical behavior at high energies, because there are negative-probability states with momentum scale r_P. In the sector with three atoms, two of w…
We explore a nuclear physics resolution to the discrepancy between the predicted standard big-bang nucleosynthesis (BBN) abundance of 7Li and its observational determination in metal-poor stars. The theoretical 7Li abundance is 3-4 times greater than the observational values, assuming the baryon-to-photon ratio, eta_wmap, determined by WMAP. The 7Li problem could be resolved within the standard BBN picture if additional destruction of A=7 isotopes occurs due to new nuclear reaction channels or upward corrections to existing channels. This could be achieved via missed resonant nuclear reactions…
