We have analyzed the reaction $χ_{c0}\to \bar{p} K^+Λ$ reported by the BESIII Collaboration, taking into account the contributions from the intermediate $K(1830)$, $N(2300)$, and $Λ(1520)$ resonances. Our results are in good agreement with the BESIII measurements, and it is found that the anomalous enhancement near the $\bar{p}Λ$ threshold is mainly due to the contribution of the $K(1830)$ resonance. We also show that the interference of the high-mass $N^*$ and $Λ^*$ can not produce the anomalous enhancement near the $\bar{p}Λ$ threshold.
We have chosen the $\bar{B}^0 \to D^{*+} \bar{D}^{*0} K^-$ reaction in order to observe the $I=0, J^P=1^+$ ($R_1$) partner state of the $X_0(2866)$ stemming from the $D^*\bar{K}^*$ molecular picture. The reaction proceeds via external emission in the most favored Cabibbo decay mode and one observes the $R_1$ state as a very strong peak versus the background in the $D^{*+} K^-$ spectrum. The branching ratio for $R_1$ production in this reaction is estimated of the order of $4\times 10^{-3}$. The method used, applied to the $B^+ \to D^- D^+ K^+$ reaction, produces a ratio of signal to background…
We demonstrate that triangle singularity (TS) and box singularity (BS) mechanisms can produce unique narrow enhancements at the $Λ_c\bar{D}$ and $Λ_c\bar{D}^*$ thresholds in the invariant mass spectra of $J/ψp$ and $J/ψpπ$, respectively. Taking into account that such mechanisms only depend on the initial $Σ_c^{(*)}\bar{D}^{(*)}$ interactions near threshold within the TS or BS kinematic regimes, the $Λ_c\bar{D}$ and $Λ_c\bar{D}^*$ threshold enhancements can be regarded as a feed-down phenomenon originated from both the heavier pentaquark decays and the $Σ_c^{(*)}\bar{D}^{(*)}$ scatterings from …
Solved is a new puzzle raised by the observation of an enhancement structure Z(3930) in $γγ\to D\bar{D}$. If categorizing Z(3930) as $χ_{c2}(2P)$ suggested by Belle and BaBar, we must explain why $χ_{c0}(2P)$ dominantly decaying into $D\bar{D}$ is missing in the $D\bar{D}$ invariant mass spectrum. In this work, we propose that the Z(3930) enhancement structure may contain two $P$-wave higher charmonia {$χ_{c0}(2P)$} and $χ_{c2}(2P)$. We show that this assumption is supported by our analysis of the $D\bar{D}$ invariant mass spectrum and $\cosθ^\ast$ distribution of $γγ\to D\bar{D}$. This observ…
The $Y(4220)$ production in the process of $p\bar{p} \to Y(4220)π^0$ is studied within the effective Lagrangian approach. We first study the $e^+e^-\to Y(4220) \to p\bar{p}π^0$ reaction at center-of-mass energy $4.258$ GeV with the assumption that the $Y(4220)$ is a $ψ(4S)$ state. We show that the inclusion of nucleon and nucleon resonance leads to a quite good description of the experimental data of $π^0 p$ and $π^0 \bar{p}$ invariant mass distributions. Then, the total and angular distributions of the $p\bar{p} \to Y(4220)π^0$ reaction are investigated. It is shown that the nucleon pole is d…
In sqrt(sNN) = 200 GeV Au+Au collisions PHENIX reported a significant enhancement in the low-mass region (0.1 < m_ee < 0.7 GeV) of the dielectron spectrum, which is still not fully understood. Several theoretical works and an indirect measurement suggest that, due to the possible restoration of the U_A(1) part of the chiral symmetry in a hot and dense medium, the mass of the eta' meson may substantially decrease. This work reports on a statistically acceptable description of the PHENIX low-mass dilepton enhancement using a radial flow dominated meson spectra, chain decays of long-lived resonan…
We study the $\bar K p \to Y K\bar K π$ reactions with $\bar K = \bar K^0, K^-$ and $Y=Σ^0, Σ^+, Λ$, in the region of $K\bar K π$ invariant masses of $1200-1550$ MeV. The strong coupling of the $f_1(1285)$ resonance to $K^* \bar K$ makes the mechanism based on $K^*$ exchange very efficient to produce this resonance observed in the $K\bar K π$ invariant mass distribution. In addition, in all the reactions one observes an associated peak at $1420$ MeV which comes from the $K^* \bar K$ decay mode of the $f_1(1285)$ when the $K^*$ is placed off shell at higher invariant masses. We claim this to be…
The near-threshold $e^+e^- \to Λ\barΛ$ reaction is studied with the assumption that the production mechanism is due to a near-$Λ\barΛ$-threshold bound state. The cross section of $e^+e^- \to Λ\barΛ$ reaction is parametrized in terms of the electromagnetic form factors of $Λ$ hyperon, which are obtained with the vector meson dominance model. It is shown that the contribution to the $e^+e^- \to Λ\barΛ$ reaction from a new narrow state with quantum numbers $J^{PC}=1^{--}$ is dominant for energies very close to threshold. The mass of this new state is around 2231 MeV, which is very close to the ma…
Within the effective Lagrangian approach, we study the $p\bar{p} \rightarrow ψη$ [$ψ\equivψ(3686)$, $J/ψ$] reaction at the low energy where the contributions from nucleon pole and low-lying nucleon resonances, $N(1520)$, $N(1535)$ and $N(1650)$ are considered. All the model parameters are determined with the help of current experimental data on the decay of $ψ\to p \bar{p} η$. Within the model parameters, the total and differential cross sections of the $p\bar{p} \rightarrow ψη$ reaction are predicted. We show that the relative phases between different amplitudes of different nucleon resonance…
High-statistics data on the reactions $γγ\to K^+K^-$ and $γγ\to K^0\bar K^0$ are the last missing link in investigations of the light scalar mesons $f_0(980)$ and $a_0(980)$ in photon-photon collisions. It is believed that $f_0(980)$ and $a_0(980)$ resonances exhibit their four-quark structure in these reactions in a vary peculiar way. The work estimates the feasibility of measurements of scalar contributions near $γγ\to K^+K^-$ and $γγ\to K^0\bar K^0$ reaction thresholds at modern colliders.
A theoretical study of $\bar{p}p \to \bar{p}n π^+ $ reaction for anti-proton beam energy from 1 to 4 GeV is made by including contributions from various known $N^*$ and $Δ^*$ resonances. It is found that for the beam energy around 1.5 GeV, the contribution of the Roper resonance $N^*_{(1440)}$ produced by the t-channel $σ$ exchange dominates over all other contributions. Since such reaction can be studied in the forthcoming $\bar{P}$ANDA experiment at Facility of Antiproton and Ion Research (FAIR), the reaction will be realistically the cleanest place for studying the properties of the Roper r…
In this work, we investigate the reaction of $γγ\to D\bar{D}$, taking into account the s-wave $D\bar{D}$ final state interaction. By fitting to the $D\bar{D}$ invariant mass distributions measured by the Belle and BaBar Collaborations, we obtain a good reproduction of the data by means of a $D\bar{D}$ amplitude that produces a bound $D\bar{D}$ state with $I=0$ close to threshold. The error bands of the fits indicate, however, that more precise data on this reaction are needed to be more assertive about the position and width of such state.
We perform a calculation of the strong interaction effects between the $B$ and $D$ mesons in the $\bar{B} \to D \barν \ell$ reaction, as a crossing process of reactions with $BD$ in the final state, where the strong interaction between the mesons leads to a bound $BD$ state. We find corrections to the tree level amplitude of the order of $15-25\%$. We further see the effect of the corrections studied in the $R_D$ ratio for the rates of $\bar{B} \to D \barν_ττ$ and $\bar{B} \to D \barν_e \ell$ decays and find corrections of the order of $10\%$. Given the claims of $1.5\%$ precision in this rati…
In this work, we make a theoretical study on the $p \bar p \rightarrow Λ\barΛη$ reaction for antiproton beam energy from threshold to 4GeV within an effective Lagrangian approach and isobar model. By assuming this reaction is dominated by the excitation of $Λ$ and $\bar Λ$ resonances in intermediate states, we calculate the total cross sections and give the predictions of the angular distribution and invariant mass spectrum of final particles. In particular, we discuss the possibility to verify the existence of a narrow $Λ$ resonance found in the process of $K^- p\to ηΛ$ in the present reactio…
We investigate roads for evaluating model-independent cross-section distributions for the sequential hyperon decay $Σ^0\rightarrowΛγ;Λ\rightarrow pπ^- $ and its corresponding antihyperon decay. The hyperons are produced in the reaction $e^+e^-\rightarrow J/ψ\rightarrow Σ^0\barΣ^0$. Cross-section distributions are calculated using the folding technique.
There is a significant discrepancy between the current theoretical prediction of the cosmological lithium abundance, mostly produced as Be7 during the Big Bang, and its observationally inferred value. We investigate whether the resonant enhancement of Be7 burning reactions may alleviate this discrepancy. We identify one narrow nuclear level in B9, E_{5/2^+} \simeq 16.7 MeV that is not sufficiently studied experimentally, and being just \sim 200 keV above the Be7+d threshold, may lead to the resonant enhancement of Be7(d,γ)B9 and Be7(d,p)ααreactions. We determine the relationship between the do…
A double-scattering reaction $π^+ + d\to p + p + η$, where an $η$ meson is rescattered, may provide new information on the $ηN\to ηN$ scattering. An idea to measure this reaction is proposed. Moreover, experimental search for $η$-mesic nuclei by the same $(π, N)$ reaction is discussed.
We report on a study of the sequential hyperon decay $Σ^0\rightarrowΛγ;Λ\rightarrow pπ^- $ and its corresponding anti-hyperon decay. We derive a multi-dimentional and model-independent formalism for the case when the hyperons are produced in the reaction $e^+e^-\rightarrowΣ^0\barΣ^0$. Cross-section distributions are calculated using the folding technique. We also study sequential decays of single-tagged hyperons.
Cross-section distributions are calculated for the reaction $e^+ e^- \rightarrow J/ψ\rightarrow \barΛ(\rightarrow \bar{p}π^+) Λ(\rightarrow pπ^-)$, and related annihilation reactions mediated by vector mesons. The hyperon-decay distributions depend on a number of structure functions that are bilinear in the, possibly complex, psionic form factors $G_M^ψ$ and $G_E^ψ$ of the Lambda hyperon. The relative size and relative phase of these form factors can be uniquely determined from the unpolarized joint-decay distributions of the Lambda and anti-Lambda hyperons. Also the decay-asymmetry parameters…
We study the charmed baryon production reaction ${\bar p} p \to {\bar Λ}_c^- Λ_c^+$ using the $t$-channel $D^0$ and $D^{*0}$ meson exchange diagrams within an effective Lagrangian model involving the physical hadron masses and the coupling constants determined from SU(4) flavor symmetry. The initial and final state distortion effects are accounted for by using a simple eikonal approximation based procedure. The vertex parameters of our model have been checked by employing them to calculate the cross sections for the ${\bar p} p \to {\bar Λ} Λ$ reaction within a similar model. We predict the ${…
A model for the $\bar K d \to πY N$ reactions with $Y=Λ, Σ$ is developed, aiming at establishing the low-lying $Λ$ and $Σ$ hyperon resonances through analyzing the forthcoming data from the J-PARC E31 experiment. The off-shell amplitudes generated from the dynamical coupled-channels (DCC) model, which was developed in Kamano et al. [Phys. Rev. C 90, 065204 (2014)], are used as input to the calculations of the elementary $\bar K N \to \bar K N$ and $\bar K N \to πY$ subprocesses in the $\bar K d \to πY N$ reactions. It is shown that the cross sections for the J-PARC E31 experiment with a rather…
The production of superheavy $Λ_{c\bar{c}}^{\ast }(4209)$ baryon in the $K^{-}p\rightarrow η_{c}Λ$ process via $s$-channel is investigated with an effective Lagrangian approach and the isobar model. Moreover, the $t$-channel with $K^{\ast }$ and $u$-channel with nucleon exchange are also considered, which are regarded as the background for the $Λ_{c\bar{c}}^{\ast }(4209)$ production in the $K^{-}p\rightarrow η_{c}Λ$ reaction. The numerical results indicate it is feasible to searching for the superheavy $Λ_{c\bar{c}}^{\ast }(4209)$ via $K^{-}p$ scattering. These theoretical results not only pro…
Since the $N^*(1535)$ resonance was found to have large coupling to the strangeness due to its possible large $s\bar s$ component, we investigate the possible contribution of the t-channel $N^*(1535)$ exchange for the $p\bar p \to ϕϕ$ reaction. Our calculation indicates that the new mechanism gives very significant contribution for the energies above 2.25 GeV and may be an important source for evading the Okubo-Zweig-Iizuka rule in the $ϕ$ production from $N \bar{N}$ annihilation.
We employ an effective Lagrangian approach and isobar model to investigate the role of the $N^*_{c\bar{c}}(4261)$ resonance with hidden charm in the $π^- p \to J/ψn$ reaction. The total and differential cross sections of this reaction are predicted by including contributions from both $N^*_{c\bar{c}}(4261)$ and nucleon pole. It is found that the maximal value of the total cross section can exceed 11 $μb$ and a clear $N^*_{c\bar{c}}(4261)$ peak is visible there, well distinguished from background. As center-of-mass energy increases to about 4.8 GeV, the background makes the differential cross s…
We study the reaction $e^+e^-\to\bar DD$ near threshold in the $^3P_0$ non-relativistic quark model, including as intermediate states the $J/ψ$, $ψ(2S)$, $ψ(3770)$ and $ψ(4040)$ mesons. The work reveals that experimental data strongly favor one of the two $ψ(2S)-ψ(3770)$ mixing angles derived by fitting to the $e^-e^+$ partial decay widths of the $ψ(2S)$ and $ψ(3770)$ mesons. The meson $X(3940)$ as well as the resonance around 3.9 GeV observed by Belle and BaBar Collaborations in the reaction $e^+e^-\rightarrow \bar DD$ is unlikely to be a $c\bar c$ $I^G(J^{PC})=0^-(1^{--})$ state.
We investigate the two-body reactions $\bar K N\rightarrow \bar K N$, $\bar K N\rightarrow πΛ$, and $\bar K N\rightarrow πΣ$ via single-energy partial-wave analyses in the c.m.\ energy range 1480 to 2100 MeV. The partial-wave amplitudes for these reactions thus extracted were constrained by a multichannel energy-dependent model satisfying unitarity of the partial-wave $S$-matrix. We obtain excellent predictions of differential cross sections, polarizations, polarized cross sections, and cross sections for these reactions from a global energy-dependent solution.
Production of Hyperons, Charmed Baryons, and Hadronic Molecule Candidates in Neutrino-Proton Reaction
Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）；Tsinghua University（清华大学）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）
Stimulated by the recent LHCb observation of a new exotic charged structure $T^{+}_{cc}$, we propose to use the central diffractive mechanism existing in the $γp\to{}D^{+}\bar{T}^{-}_{cc}Λ_c^{+}$ ($\bar{T}_{cc}$ is antiparticle of $T^{+}_{cc}$) reaction to produce $T^{+}_{cc}$. Our theoretical approach is based on the chiral unitary theory where the $T^{+}_{cc}$ resonance is dynamically generated. With the coupling constant of the $T^{+}_{cc}$ to $DD^{*}$ channel obtained from chiral unitary theory, the total cross sections of the $γp\to{}D^{+}\bar{T}^{-}_{cc}Λ_c^{+}$ reaction are evaluated. O…
We study the $B^+ \to J/ψωK^+ $ reaction, measured by the LHCb collaboration, and show that it is driven by the presence of two resonances, the $X(3940)$ and $X(3930)$, that are of molecular nature and couple most strongly to $D^* \bar{D}^*$, but also to $J/ψω$. Because of that, in the $J/ψω$ mass distribution we find a peak related to the excitation of the resonances and a cusp with large strength at the $D^* \bar{D}^*$ threshold.
We investigate the charmed baryon production reaction $p\bar{p}\rightarrowΛ_c\barΛ_c$ in an effective Lagrangian approach. Besides the $t$-channel $D^0$ and $D^{*0}$ mesons exchanges, the $s$-channel $Y(4630)$ meson exchange is taken into account. For the total cross sections, the $D^0$ and $D^{*0}$ mesons provide minor background contributions, while the $Y(4630)$ state gives a clear peak structure with the magnitude of 10 $μ$b at center of mass energy 4.63 GeV. Basing on the results, we suggest that the reaction of $p\bar{p}\rightarrowΛ_c\barΛ_c$ can be used to search for the $1^{--}$ charmo…
Within the framework of the local hidden gauge formalism, we have reanalyzed the hidden-charm vector-vector meson $D^*\bar{D}^*$, $K^*\bar{K}^*$, and $ρρ$ interactions with the quantum numbers $I(J^P)=1(1^+)$. The estimation indicates that $D^*\bar{D}^*$ system could form a bound state around 4010 MeV. By comparing our theoretical estimation with the BESIII measurements of the $e^+e^- \to (D^*\bar{D}^*)^{\pm}π^{\mp}$ and $e^+e^- \to (D^*\bar{D}^*) ^{0}π^{0}$ reactions at $\sqrt{s}=4.26$ GeV , we find that the enhancement structure of the $Z_c(4025)$ in the $D^*\bar{D}^*$ invariant mass distrib…
Radiation reaction (RR) is the oldest still-unsolved problem in electrodynamics. In addition to conceptual difficulties in its theoretical formulation, the requirement of exceedingly large charge accelerations has thus far prevented its unambiguous experimental identification. Here, we show how measurable RR effects in a laser-electron interaction can be achieved through the use of flying focus pulses (FFPs). By allowing the focus to counterpropagate with respect to the pulse phase velocity, a FFP overcomes the intrinsic limitation of a conventional laser Gaussian pulse (GP) that limits its fo…
Next-to-leading order QCD corrections to top quark spin correlations at hadron colliders: the reactions $g g \to t {\bar t} (g)$ and $g q ({\bar q}) \to t {\bar t} q ({\bar q})$
Impact of Baryon anti-Baryon annihilation on hyperon ($Λ$, $\barΛ$) production and apparent strangeness enhancement in $\barΛ/\bar{p}$ in heavy ion collisions at SPS energy
Variable Energy Cyclotron Centre（可变能量回旋加速器中心）；Homi Bhabha National Institute（霍米·巴巴国立研究所）
Resonance model study of kaon production in baryon baryon reactions for heavy ion collisions
在相对论树能级处理的共振模型下，研究了重子-重子（$N$和$Δ$）碰撞中总K介子产生截面的能量依赖性.本研究是首次尝试完成一个系统的，一致的调查的基本K介子生产反应的介子重子和重子重子反应。我们的模型表明，$N N \to N Y K$和$ΔN \to N Y K$（$Y = Λ$或$Σ$）反应的同位旋平均总截面的大小几乎是相等的能量高达约200兆电子伏以上的阈值。然而，$ΔN$反应的幅度变得约6倍以上的$N N$反应在能量约1 GeV以上的阈值。此外，$N N \to ΔY K$反应的同位旋平均总截面的大小原来是可比较的$N N \to N Y K$反应在$N N$不变碰撞能量约3.1 GeV，约5至10倍大的$N N$不变碰撞能量约3.5 GeV。对重离子碰撞中K介子产生的输运模型研究所需的所有同位旋通道的微观截面进行了参数化。然后将这些横截面应用于相对论输运模型中，以研究对底层基元K ~+产生横截面的敏感性。
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, …
