We study the observed enhancement of a $p\bar p$ system near the threshold in the process $J/ψ\to γp\bar p$ and $e^+ e^- \to p\bar p$. From early studies the enhancement can be explained by final state interactions, which are in general taken into account with some potential models. In this work we offer a simple approach within quantum field theory to explain the observed enhancement. We point out that among different final state interactions the rescattering in a $N\bar N$ system though exchange of $π$ is the most important. The effects of the rescattering is completely fixed by the well-known coupling $g_{πNN}$. Our results show that the enhancement in $J/ψ\to γp\bar p$ and $e^+ e^- \to p\bar p$ can be well described with the rescattering effects.
We investigate the two-photon corrections to the process $p\bar{p} \to e^+e^-$ at large momentum transfer, aimed to access the time-like nucleon form factors. We estimate the two-photon corrections using a hard rescattering mechanism, which has already been used to calculate the corresponding corrections to elastic electron-proton scattering. Using different nucleon distribution amplitudes, we find that the two-photon corrections to the $p\bar{p} \to e^+e^-$ cross sections in the momentum transfer range 5 - 30 GeV$^2$ is below the 1 % level.
Using purely phenomenological approach we show that the peaking structures observed in the psi(2S) pi+ and chi_c1 pi+ mass spectra in B -> psi(2S)(chi_c1) pi+ K decays can be result of (D \bar{D}^(*))+ -> (ccbar)_res pi+ rescattering in the decays B -> D_sJ (-> \bar{D}(*) K) D(*). In particular, the position of the peak in the chain B -> D_s(2S) D+ -> K- \bar{D}*0 D+ -> K- psi(2S) pi+ coincides well with the measured Z(4430) mass, assuming the mass of D_s(2S) (the first radial excitation of D_s) to be 2610 MeV/c2. The widths of the Z(4430) peak is also well reproduced in this approach independ…
Final-state rescattering in $\bar{B}^{0}_{(s)}\to Λ^{+}_{c}\barΛ^{-}_{c}$ decays
Frontiers Science Center for Rare Isotopes, and School of Nuclear Science and Technology, Lanzhou University（兰州大学前沿稀有同位素科学中心及核科学与技术学院）；School of Physical Science and Technology, Inner Mongolia Key Laboratory of Microscale Physics and Atomic Manufacturing, Inner Mongolia University（内蒙古大学物理科学与技术学院）；Physik Department, Universität Siegen（锡根大学物理系）
Final State Rescattering and Color-suppressed \bar B^0-> D^{(*)0} h^0 Decays
The color-suppressed \bar B^0-> D^{(*)0}π^0, D^{(*)0}η, D^0ωdecay modes have just been observed for the first time. The rates are all larger than expected, hinting at the presence of final state interactions. Considering \bar B^0-> D^{(*)0}π^0 mode alone, an elastic D^{(*)}π-> D^{(*)}πrescattering phase difference δ \equiv δ_{1/2} - δ_{3/2} \sim 30^ \circ would suffice, but the \bar B^0-> D^{(*)0}η, D^0ωmodes compel one to extend the elastic formalism to SU(3) symmetry. We find that a universal a_2/a_1=0.25 and two strong phase differences 20^ \circ \sim θ< δ< δ^ \prime \sim 50^ \circ can desc…
Final-state rescattering mechanism of the $Δ(1232)^{++}$ production in $Λ^+_c \to K^- π^+ p$ decay
Qufu Normal University（曲阜师范大学）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）；Tianjin University（天津大学）
We study the property of the $X(3872)$ meson by analyzing the $B\to K D\bar D^*$ and $B\to K J/ψπ^+π^-$ decay processes. The competition between the rescattering mediated through a Breit-Wigner resonance and the rescattering generated from a local $D\bar{D}^* \to D\bar{D}^*$ interaction is carefully studied through an effective lagrangian approach. Three different fits are performed: pure Breit-Wigner case, pure $D\bar{D}^*$ molecule case with only local rescattering vertices (generated by the loop chain), and the mixed case. It is found that data supports the picture where X(3872) is mainly a…
In a previous paper we suggested an explanation for the peak designated as $Z(4430)^+$ in the $ψ^\primeπ^+$ mass spectrum, observed by Belle in ${\bar{\!B}} \to {ψ^\prime} π^+ K$ decays, as an effect of $\bar{\!D}{}^{\,*0}D^{\,+} \to ψ^\primeπ^+$ rescattering in the decays ${\bar{\!B}} \to {D_{s}^{\,\prime -}} {D}$, where the $D_{s}^{\,\prime -}$ is an as-yet unobserved radial excitation of the pseudoscalar ground state $D_{s}^{\,-}$-meson. In this paper, we demonstrate that this hypothesis provides an explanation of the double $Z^+$-like peaking structures, which were studied by LHCb with muc…
Several $B$ and $B_s$ decays have been observed which have been cited as evidence for exchange ($E$), penguin annihilation ($PA$) and annihilation ($A$) processes, such as $\bar b d \to \bar u u$, $\bar b s \to \bar u u$ and $\bar b u \to W^* \to \bar c s$, respectively. These amplitudes are normally thought to be suppressed, as they involve the spectator quark in the weak interaction and thus should be proportional to the $B$-meson decay constant $f_B$. However, as pointed out a number of years ago, they can also be generated by rescattering from processes whose amplitudes do not involve $f_B…
A model for the $B^\pm \to π^-π^+π^\pm$ decay amplitude is proposed to study the large CP violation observed at the high mass region of the Dalitz plane. A short distance $ b \to u $ amplitude with the weak phase $γ$ is considered together with the contribution of a hadronic charm loop and a s-wave $D\bar{D}\to ππ$ rescattering. In the model, the $χ_c^0$ appears as a narrow resonant state of the $D\bar D$ system below threshold. It is introduced in an unitary two channel S-matrix model of the coupled $D\bar D$ and $ππ$ channels, where the $χ_c^0$ complex pole in $D\bar D$ channel shows its sig…
Final-state rescattering mechanism of doubly-charmed baryon decays: $\mathcal{B}_{cc}\to\mathcal{B}_{c}V$
The College of Materials and physics, China University of mining and technology（中国矿业大学材料科学与工程学院）；Lanzhou Center for Theoretical Physics, Key Laboratory of Theoretical Physics of Gansu Province, Key Laboratory of Quantum Theory and Applications of MoE, Gansu Provincial Research Center for Basic Disciplines of Quantum Physics, Lanzhou University（兰州大学理论物理中心、甘肃省理论物理重点实验室、教育部量子理论与应用重点实验室、甘肃省量子物理基础学科研究中心）；Frontiers Science Center for Rare Isotopes, and School of Nuclear Science and Technology, Lanzhou University（兰州大学稀有同位素前沿科学中心、核科学与技术学院）
Following the experimental results from LHCb on the rare decay $B^+_c \to K^-K^+π^+$, we investigate the possibility where this process is dominated by a double charm rescattering. The $B_c$ decay to double charm channels have a weak topology that is favoured in comparison with the direct production of $K^-K^+π^+$ in the final state, suppressed by quark annihilation. The decay amplitude for $B^+_c \to K^-K^+π^+$ with $B_c$ decaying first to double charm channels is described by a charm penguin diagram, represented by charm hadronic triangle loops, which reach the final state of interest after …
The rare decay $\bar B_d^0\to J/ψϕ$ can proceed in four distinct mechanisms: (i) production of the $ϕ$ via tri-gluon fusion, (ii) photoproduction of the $J/ψ$ or $ϕ$, (iii) final-state rescattering of $D_s^{(*)}D_s^{(*)}$ produced in the $\bar B_d$ decay to $J/ψϕ$, and (iv) production of the $ϕ$ via $ω-ϕ$ mixing. In this work, we examine the contributions from photoproduction and final-state rescattering to $\bar B_d^0\to J/ψϕ$ and find that the corresponding branching ratios are of order $10^{-11}$ and $10^{-9}$, respectively. Hence, this decay is dominated by the $ω-ϕ$ mixing effect.
We evaluate the contribution of pion-pion rescattering to the $p p \to p p π^+ π^-$ and $p \bar p \to p \bar p π^+ π^-$ reactions. We compare our results with the close-to-threshold experimental data. The pion-pion rescattering contribution is found there to be negligible. The predictions for future experiments with PANDA detector at High Energy Storage Ring (HESR) in GSI Darmstadt are presented. It is discussed how to cut off the dominant Roper resonance and double-$Δ$ excitation mechanisms leading to the $p p π^+ π^-$ channel in final state. Differential distributions in momentum transfers, …
We consider exclusive two-pion production in antiproton-deuteron interactions at the beam momenta around 10 GeV/c in the kinematics with large momentum transfer in the underlying hard process $\bar p n \to π^- π^0$. The calculations are performed taking into account the antiproton and pion soft rescattering on the spectator proton in the framework of the generalized eikonal approximation. We focus on the color transparency effect that is modeled by introducing the dependence of rescattering amplitudes on the relative position of the struck and spectator nucleons along the momentum of a fast pa…
On the basis of the generalized eikonal approximation we study the exclusive reactions $\bar p d \to J/ψ\, n$ and $\bar p d \to ψ^\prime\, n$ in vicinity of the thresholds for charmonium production on a free proton target. It is shown that the rescattering of the incoming antiproton and outgoing charmonium on the spectator neutron leads to a depletion of the charmonium production at low- and to an enhancement at high transverse momenta. This is in qualitative agreement with previous studies of hard proton knockout in proton-deuteron collisions. We analyze different physical sources of uncertai…
In the $J/ψ$ radiative decay channels $J/ψ\to γV\bar{V}$, the result of partial wave analysis indicates that the $V\bar{V}$ systems are predominately pseudoscalar component, and most of these channels have relatively large branching ratios at an order of $10^{-3}$. Meanwhile, vector mesons, such as $ρ$, $ω$ and $K^*$, have strong couplings with nucleons and/or hyperons. This suggests a dynamical mechanism describing the $ηp\bar{p}$ form factors for higher $η$ mesons, such as $η(1405/1475)$ and $η(1760)$. It is thus natural to expect that rescatterings of these vector meson pairs into $p\bar{p}…
The LHCb collaboration reported the observation of a narrow peak in the $D^- K^+$ invariant mass distributions from the $B^+\to D^+ D^- K^+$ decay. The peak is parameterized in terms of two resonances $X_0(2900)$ and $X_1(2900)$ with the quark contents $\bar{c}\bar{s}ud$, and their spin-parity quantum numbers are $0^+$ and $1^-$, respectively. We investigate the rescattering processes which may contribute to the $B^+\to D^+ D^- K^+$ decays. It is shown that the $D^{*-}K^{*+}$ rescattering via the $χ_{c1}K^{*+}D^{*-}$ loop or the $\bar{D}_{1}^{0}K^{0}$ rescattering via the $D_{sJ}^{+}\bar{D}_{1…
The Sommerfeld rescattering formula is compared to the e+e- -> ppbar BaBar data at threshold and above. While there is the expected Coulomb enhancement at threshold, two unexpected outcomes have been found: |G^p (4M_p^2)|= 1, like for a pointlike fermion, and moreover data show that the resummation factor in the Sommerfeld formula is not needed. Other e+e- -> baryon-antibaryon cross sections show a similar behavior near threshold.
