We study the reactions $J/ψ\to\barΛK^-p$ and $J/ψ\to\barΛπ^+π^-Λ$ with a unitary chiral approach. We predict the ratio of the invariant mass distributions of these two reactions at the $Λ(1520)$ peak position, which is free of the unknown production mechanism and reflects only the properties of the $Λ(1520)$. An experimental measurement of this ratio will provide the couplings of the $Λ(1520)$ to its decay channels, allowing to test the predictions of the chiral unitary approach on this resonance, which appears as dynamically generated in that approach.
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…
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.
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…
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 study pion induced reactions for charmed baryons $B$, $π$ + N $\rightarrow$ $D^*$ + $B$. First we estimate charm production rates in comparison with strangeness production using a Regge model which is dominated by vector ($D^*$ or $K^*$ ) Reggeon exchange. Then we examine the production rates of various charmed baryons $B$ in a quark-diquark model. We find that the production of excited states are not necessarily suppressed, a sharp contrast to strangeness production, which is a unique feature of the charm production with a large momentum transfer.
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.
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.
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…
Next-to-leading order QCD corrections to top quark spin correlations at hadron colliders: the reactions $g g \to t {\bar t} (g)$ and $g q ({\bar q}) \to t {\bar t} q ({\bar q})$
The exclusive reaction $pp \to pp (K^{*0} \bar{K}^{*0} \to K^{+}π^{-}K^{-}π^{+})$ for the LHC experiments is discussed. The amplitudes for the reaction are formulated within the tensor-pomeron approach. We consider two diffractive mechanisms: the $f_{2}(1950)$ $s$-channel exchange mechanism and the $K^{*0}$-exchange mechanism. First mechanism is a candidate for central diffractive production of tensor glueball and the second one is an irreducible continuum. Comparison with data from WA102 experiment are made and predictions for LHC experiments are given. We find that including the continuum co…
We propose two reactions, $\bar{B}^0 \to K^0 D^{+} K^-$ and $\bar{B}^0 \to K^{*0} D^{*+} K^-$, already measured at Belle, to look into the $J^P=0^+$, $X_0(2866)$ state and a $1^+$ partner of molecular $D^*\bar{K}^*$ nature, by looking at the $D^+ K^-$ and $D^{*+} K^-$ invariant mass distributions, respectively. Very clear peaks over the background are predicted and the branching ratios for the production of these states are evaluated to facilitate the task of determining the needed statistics for their observation. The fact that the $K^{*0} K^-$ mass distribution from accumulation of events of…
We show that the measurement of the $Z$ polarization in the $e^+e^-\to t\bar t Z$ process would allow an interesting determination of the role of the top quark mass. This can be used for testing the possibility of top compositeness or of the occurence of final state interactions related to the mass generation in particular the interaction with dark matter.
The annihilation process p bar(p) -> p D0 bar(Lambda)_c(2286) is studied taking into account t-channel D0, D*0 meson exchange and the resonance contribution of Lambda_c(2286) and Lambda_c(2940) baryons. We assume that the Lambda_c(2940) baryon is a pD*0 molecular state with spin-parity (1/2)+ and (1/2)-. Our results show that near the threshold of p bar(p) -> Lambda_c(2286) bar(Lambda)_c(2286) the contribution from the intermediate state Lambda_c(2940) is also sizeable and can be observed at the PANDA experiment. Another conclusion is that the spin-parity assignment (1/2)- for Lambda_c(2940) g…
We show what type of effects on the rate of $Z_L$ production in the $γγ\to t\bar t Z$ and $gluon~gluon\to t\bar t Z$ processes could be produced by an effective scale dependent top mass or by final state interactions between massive particles for example generated by the presence of dark matter.
We have performed a calculation of the $D\bar D$, $D\bar D^\ast$, $D^\ast\bar D$, $D^\ast\bar D^\ast$ components in the wave function of the $ψ(3770)$. For this we make use of the $^3P_0$ model to find the coupling of $ψ(3770)$ to these components, that with an elaborate angular momentum algebra can be obtained with only one parameter. Then we use data for the $e^+e^-\to D\bar D$ reaction, from where we determine a form factor needed in the theoretical frame work, as well as other parameters needed to evaluate the meson-meson selfenergy of the $ψ(3770)$. Once this is done we determine the $Z$ …
We analyze the $Wt\bar b$ production processes and especially the rate of longitudinal $W$ polarization sensitive to a possible top quark mass scale dependence and to the presence of strong final state $Wt$ interactions for example generated by a dark matter environment. We give illustrations for the three processes $e^+e^-$, gluon-gluon and $γγ\to W t\bar b $.
We study the meson-baryon interaction in S-wave in the strangeness S=-1 sector using a chiral unitary approach based on a next-to-leading order chiral SU(3) Lagrangian. We fit our model to the large set of experimental data in different two-body channels. We pay particular attention to the $\bar{K} N \rightarrow K Ξ$ reaction, where the effect of the next-to-leading order terms in the Lagrangian are sufficiently large to be observed, since at tree level the cross section of this reaction is zero. For these channels we improve our approach by phenomenologically taking into account effects of th…
We study the $J/ψ\to ϕK \bar K$ decay, looking for differences in the production rates of $K^+ K^-$ or $K^0 \bar K^0$ in the region of 1700-1800 MeV, where two resonances appear dynamically generated from the vector-vector interaction. Two resonances are known experimentally in that region, the $f_0(1710)$ and a new resonance reported by the BABAR and BESIII collaborations. The $K \bar K$ should be produced with $I=0$ in that reaction, but due to the different $K^{*0}$ and $K^{*+}$ masses some isospin violation appears. Yet, due to the large width of the $K^*$, the violation obtained is very s…
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 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…
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 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…
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.
We examine the possibility that one could measure partonic charge symmetry violation (CSV) by comparing neutrino or antineutrino production through charged-current reactions induced by electrons or positrons at a possible electron collider at the LHC. We calculate the magnitude of CSV that might be expected at such a facility. We show that this is likely to be a several percent effect, substantially larger than the typical CSV effects expected for partonic reactions.
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 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, …
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…
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…
The meson-baryon interaction in s-wave in the strangeness S=-1 sector has been studied, employing a chiral SU(3) Lagrangian up to next-to-leading order (NLO) and implementing unitarization in coupled channels. The parameters of the Lagrangian have been fitted to a large set of experimental data in different two-body channels, paying special attention to the $\bar{K} N \rightarrow K Ξ$ reaction, which is particularly sensitive to the NLO terms. With the aim of improving the model in the $KΞ$ production channels, effects of the high spin hyperon resonances $Σ(2030)$ and $Σ(2250)$ have been taken…
The reaction $e^+e^-\rightarrow Λ^+_c\barΛ^-_c$ is investigated at energies close to the threshold with emphasis on the role played by the $X(4630)$ resonance. The interaction in the final $Λ^+_c \barΛ^-_c$ system, constructed within chiral effective field theory and supplemented by a pole diagram that represents a bare $X(4630)$ resonance, is taken into account rigorously. The pole parameters of the $X(4630)$ are extracted and found to be compatible with the ones of the $X(4660)$ resonance that have been established in the reaction $e^+e^- \to π^+π^-ψ(2S)$. The actual result for the $X(4630)$…
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…
