arXiv subjects

K. P. Khemchandani

Publications and source records attributed to K. P. Khemchandani.

At least 19 recordsLinked to original sources

arXiv2026

Enigmatic properties of $Ξ(1620)$ and $Ξ(1690)$

Motivated by a considerable release of data on first two excited states of the doubly strange baryon, $Ξ(1620)$ and $Ξ(1690)$, from different experimental collaborations in recent years, we investigate meson-baryon interactions in a coupled-channel approach. The systems are composed of pseudoscalar and vector mesons and the calculations are done for the total spin 1/2 and isospin 1/2 configuration. The tree-level interactions are deduced from Lagrangians based on chiral and hidden local symmetries. Specifically, we make an attempt to describe (1) data on the $K^-Λ$ femtoscopic correlation function coming from $p\,p$ and $Pb\,Pb$ collisions, and (2) the available data on invariant mass distributions for different systems: $πΞ$, $\bar K Σ$ and $\bar K Λ$. We find that the amplitude which yields the correlation function close to the data results in mass distributions of different meson-baryon systems that are in discordance with the experimental data and vice-versa.

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arXiv2026

Exotic states with charm and/or strangeness

In this talk, I will discuss the properties of several exotic states with charm and/or strangeness. These states can be interpreted either as being generated from two- or three-hadron dynamics. In particular, I will focus on $D_1(2420)$ and some predictions of three-body states obtained from $n\bar

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arXiv2026

Nature of the newly found $Ω(2109)$

We present model calculations to reveal the nature of the newly found $Ω^-(2109)$ by the BESIII Collaboration, and show that the state has a strong correlation with the $\bar K^*(892)Ξ$ system. Our study is based on solving scattering equations in a coupled channel approach, which involves $K^-Ξ^0$, $\bar K^0Ξ^-$, $K^{*-}Ξ^0$, and $\bar K^{*0}Ξ^-$. We obtain the lowest order amplitudes for different spin and isospin cases and find that an isoscalar state with spin-parity $1/2^-$ is generated with precisely the same mass as $Ω^-(2109)$. We do not find any state with total spin 3/2, nor do we find any state in the isovector sector. We determine correlation functions to encourage such an experimental study and confirm the nature of $Ω^-(2109)$.

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arXiv2026

Explicitly exotic heavy flavor mesons

In this talk, I summarize the highlights of our recent and ongoing work on exotic hadrons involving explicitly exotic heavy-flavor mesons. By heavy flavors, I refer in particular to strange and charm quarks. As discussed in this manuscript, several puzzle-like features appearing in recent experimental data can be understood in terms of coupled-channel interactions. The main result is the prediction of an exotic meson carrying both charm and strangeness quantum numbers, whose properties cannot be explained as those of a simple quark-antiquark bound state. I also discuss the future prospects of our research program on this topic.

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arXiv2026

Probing the X(3700) through two-photon $D \bar{D}$ production in ultraperipheral collisions and at the EIC

We investigate whether photon-induced production in ultraperipheral heavy-ion collisions and at the EIC can provide a new environment to search for the scalar $D \bar{D}$ molecular candidate usually denoted as $X(3700)$. We calculate the tree-level amplitudes for $γγ\to D^+ D^-$ and $γγ\to D^0 \bar{D^0}$, dress the outgoing pair with a coupled-channel Bethe-Salpeter interaction in the $(D^+ D^- , D^0 \bar{D^0})$ basis, and convolute the resulting subprocess cross sections with equivalent-photon spectra. In the adopted two-channel scenario the analytic continuation of the $T$-matrix gives a bound state at $M_X=3.7162$~GeV, which is below the $D^0 \bar{D^0}$ threshold. As a consequence of this, the observed signal in the continuum is not simply an isolated narrow peak, and a characteristic near-threshold line-shape distortion is produced: around $3.70 \leq W \leq 3.85$~GeV the integrated dressed-to-bare ratios are $(13.71,0.35)$ in Pb-Pb UPCs and $(13.74,0.35)$ in $e$-Au collisions for $(D^+D^-,D^0 \bar{D^0})$. Using the BABAR-fitted central normalization $K_{\rm dressed}=0.382$, the corresponding dressed cross sections are $(24.6,14.6)~μ{\rm b}$ in Pb-Pb UPCs and $(2.41,1.43)~\rm nb$ at the EIC. The charged-to-neutral ratios are directly accessible observables, whereas the dressed-to-bare ratios provide theoretical diagnostics of the final-state interaction. The near-threshold features are controlled by the common $γγ\to D\bar{D}$ dynamics and are rather independent of the external photon source.

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arXiv2026

Revealing the nature of double-strangeness pentaquark states via femtoscopic correlation functions

Recent discoveries of exotic hadrons, which cannot be classified within the conventional quark model of $q \bar{q}$ mesons and $qqq$ baryons, strongly imply the existence of dynamically generated hadronic molecules. Some of these hadron-hadron interactions are accompanied by coupled-channel effects, which remain challenging to quantitatively determine. In this work, we demonstrate that femtoscopy provides a sensitive probe of such coupled-channel dynamics. We calculate correlation functions for the double-strangeness pentaquark candidates $P_{css}(4493)$ ($J^P=1/2^-$) and $P_{css}(4633)$ ($J^P=1/2^-$ or $3/2^-$), revealing clear signatures of the attractive interactions that can form bound states. The results are markedly different from those obtained in scenarios that neglect off-diagonal transitions, highlighting the importance of coupled-channel effects for understanding the structure of these hadrons.

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arXiv2026

$D^*π$ interaction from the lineshape of $D_1(2420)$ in $B$-decays

We present a model calculation to reproduce the differential mass distribution for the $D^*π$ system in the reactions $B^- \to D^{*+} π^- π^-$ and $B^{+}\to D_s^+D^{*-}π^{+}$ analyzed by the LHCb Collaboration, which shows a dominant signal for $D_1(2420)$. %\textbf{We} (The idea is to) We consider a model based on coupled channel meson-meson interactions that can describe the properties of $D_1(2420)$ in terms of the underlying dynamics, use it to determine the invariant mass distribution of the $D^*π$ system, and compare the results with the experimental data. We also determine the $D^*π$ scattering length, for which different values are available from different sources, leading to a controversy. To our knowledge, this is the first attempt to reproduce the mentioned data using model calculations. Our formalism relies on the hadronization of different mesons through a weak decay, allowing for the final-state (strong) interactions among the relevant constituents. We benefit from our previous work when obtaining the amplitudes corresponding to the strong interactions. We hope that our findings can be useful in further investigations of the properties of $D_1(2420)$.

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arXiv2025

Correlation functions for $n\,\bar{D}_{s1}(2460)$ and $n\,\bar{D}_{s1}(2536)$

We study the interaction of the $n \bar {D}_{s1}(2460)$ and $n \bar {D}_{s1}(2536)$ systems from the perspective that the $D_{s1}(2460)$ and $D_{s1}(2536)$ states are molecular states of $K D^*$ and $K^*D$, respectively. We use an improved version of the fixed center approximation to the Faddeev equations which fulfills exact elastic unitarity at the threshold of the systems. We predict the existence of resonant states below threshold and also determine the scattering length, effective range and correlation functions of these systems, showing that the results contain important information to test the assumed molecular nature of the two $D_{s1}$ states.

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arXiv2025

Strangeness $+1$ light multiquark baryons

In view of the renewing experimental interest for searching strangeness $+1$ baryons at J-PARC, we study the existence of light baryon resonances with strangeness +1 generated in the $K$-$(N^*/Δ^*)$ system, where $N^*$ represents either $N^*(1535)$/$N^*(1650)$/$N^*(1700)$, and $Δ^*$ corresponds to $Δ(1620)$. The description of the properties of the aforementioned states requires considering the dynamics involved in the coupled pseudoscalar-baryon and vector-baryon systems with strangeness $S=0$ in the s-wave. For the purpose of our current study, we consider the pseudoscalar-baryon (PB) and vector-baryon channels (VB) to which the mentioned $N^*$ and $Δ^*$ resonances couple and solve the Faddeev equations for the coupled channel system $K$-$\text{PB}$, $K$-$\text{VB}$, with all interactions being in the s-wave. Despite some strong attraction present in two of the subsystems, we do not find clear evidence supporting the formation of strangeness +1 states, with spin-parity $J^P=1/2^+$, in the energy region $2000-2200$ MeV. However, the case of spin-parity $J^P=3/2^+$ seems more promising, showing the formation of a resonance with a mass around 2167 MeV, with a width of 90-100 MeV. We suggest that a signal of such a state could be found in processes with final states like $KN$, $K^*(892) N$.

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arXiv2024

Bolstering up the existence of $P_s(2080)$

We present a detailed study of the partial decay widths of a spin-parity resonance $J^P=3/2^-$ $N^*$ with a mass of $\simeq$ 2070 MeV obtained from the coupled channel s wave vector-baryon $ρN$, $ωN$, $ϕN$, $K^*Λ$ and $K^*Σ$ dynamics. This state, which couples strongly to the $K^*Σ$ channel, corresponds to a nucleon with a hidden strange quark content, in analogy to the $P_c$ states discovered by the LHCb collaboration, and we denote it as $P_s(2080)$. A state with such a nature can decay to vector-baryon, pseudoscalar-baryon, and pseudoscalar-baryon resonance channels, involving triangular loops in the latter two cases. As we will show, the partial decay widths to pseudoscalar-baryon resonance channels, like $πN^*(1535)$, $πN^*(1650)$, $KΛ(1405)$, are comparable to those related to ground state baryons in the final state, like $πN$, $ηN$, $KΛ$. In this way, reactions involving such lighter baryon resonances in the final state can be used as an alternative source of information on the properties of a $N^*$ with hidden strangeness.

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arXiv2024

Heavy $K^$ mesons with open charm from $KD^{()}D^*$ interactions

In view of the recent discovery of $T_{cc}$, which can be described as a $DD^*$ molecular state, we perform a study of the $KDD^*$ system, and its extension to studying $KD^*D^*$, where $D^*D^*$ is bound as a spin 1 $T_{cc}$-like state, to search for the possible existence of exotic mesons with the open flavors $ccs$ being part of their quark configuration. Considering the additional attractive interactions present in the $KD$ and $KD^*$ subsystems, where the states $D^*_{s0}(2317)$ and $D_{s1}(2460)$ are generated, we solve the Faddeev equations considering the fixed-center approximation for the mentioned three-body systems and find the existence of two doubly charmed $K^*$-like mesons, $K_{cc}^*(4309)$ and $K_{cc}^*(4449)$, with quantum numbers $I(J^P)=1/2\,(1^-)$. Considering the respective three-body thresholds of the two systems, both $K_{cc}$-states are bound by around $60$ MeV. An experimental confirmation will bring evidence for the existence of a degree of exoticity beyond charm +2.

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arXiv2024

A study of the $ϕN$ correlation function

The femtoscopic $ϕN$ correlation function is studied within a hadronic effective Lagrangian approach with coupled channels, based on hidden local symmetry. The results are compared with the data recently reported by the ALICE collaboration. We find that the correlation function has very different features for the $ϕN$ system in the spin 1/2 and 3/2 configurations, with the spin-averaged combination matching well with the experimental data. A strong attraction, leading to the formation of a $ϕN$ bound state or a very prominent cusp is found in the spin 3/2 case. The correlation function for spin 1/2, on the other hand, is strongly impacted by the negative parity $N^*(1895)$ nucleon resonance.

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arXiv2024

Can femtoscopic correlation function shed light on the nature of the lightest, charm, axial mesons?

We present a coupled channel treatment of meson-meson dynamics, for systems with spin-parity $1^+$, and determine the corresponding amplitudes by solving the Bethe-Salpeter equations, which lead to the generation of two axial resonances when mesons are considered as the degrees of freedom in the model. One of them is narrow and has properties in good agreement with those of $D_1(2420)$. The other pole is wider, but its real and imaginary parts do not match well with the mass and width of $D_1(2430)$. The situation improves when a bare quark-model state is included, indicating that the dynamics at the quark level as well as among hadrons can describe the two states simultaneously. Further, we discuss that there exists a divergence in the value of the $D^*π$ scattering length determined through data coming from lattice QCD calculations and from heavy ion collisions. Such different values can be accommodated in the model by making small changes in the parameters while producing two poles having properties compatible with the two lightest $D_1$ states. With these results, we proceed to calculate the correlation function for the $D^{*+(0)}π^{0(+)}$ system for different sizes of the source. We discuss which scenarios can be useful to shed some light on the issue.

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arXiv2024

Intriguing aspects of light baryon resonances

We discuss that some light baryon resonances exhibit properties which cannot be described when attributing a three-valence quark structure to them. Besides pointing out the hadron resonances which clearly require description beyond the quark model, we focus on the third $s_{11},~ N^*$ state and its decay to final states consisting of the lightest hyperon resonances which have a partial width comparable to that for the decay to $πN$. Such properties of the mentioned nucleon resonance get manifested in the cross sections and other observables related to processes producing the lightest hyperon resonances. We show that all these findings arise from the strong association of the baryon resonances to the dynamics among the ground-state hadrons.

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arXiv2024

The properties of $ϕ(2170)$ and its three-body nature

We summarize the results we obtained for the partial decay widths of $ϕ(2170)$ into two-body final states formed by a $\bar K$ and a Kaonic resonance, like $K(1460)$, $K_1(1270)$, as well as to final states constituted by a $ϕ$ and an $η/η^\prime$ mesons. The results obtained are compared with the values extracted from experimental data on the corresponding branching ratios, which were determined by the BESIII collaboration. A reasonable agreement is found, which together with the previous reproduction of the mass, width, and cross section for the process $e^+ e^-\to ϕf_0$ strongly indicates the molecular nature of $ϕ(2170)$ as a $ϕK\bar K$ system.

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arXiv2023

$ϕ(2170)$ decaying to $ϕη$ and $ϕη^\prime$

In this work we calculate the decay widths of $ϕ(2170)$ to $ϕη$ and $ϕη^\prime$ by considering $ϕ(2170)$ as a $ϕK\bar K$ state, with $K\bar K$ clustering as $f_0(980)$. These decay widths have been recently determined by the BESIII, BaBar and Belle collaborations with the aim of unraveling the nature of $ϕ(2170)$. By analyzing the data on the cross sections of the process $e^+e^-\toϕη$, two solutions were found by the BESIII collaboration with the same $χ^2/n.d.f$, mass and width for $ϕ(2170)$. However, different values for $\mathcal{B}^{ϕ(2170)}_{ϕη}Γ^{ϕ(2170)}_{e^+e^-}$ were obtained: $0.24^{+0.12}_{-0.07}$ eV (solution I) and $10.11^{+3.87}_{-3.13}$ eV (solution II). In case of $\mathcal{B}^{ϕ(2170)}_{ϕη^\prime}Γ^{ϕ(2170)}_{e^+e^-}$, a value of $7.1\pm 0.7\pm 0.7$ was determined by the BESIII collaboration from fits to the data on the cross section of $e^+e^-\toϕη^\prime$. The Belle collaboration has also determined $\mathcal{B}^{ϕ(2170)}_{ϕη}Γ^{ϕ(2170)}_{e^+e^-}$ more recently, although the statistical significance related to the signal of $ϕ(2170)$ in the data is low. We calculate the decay widths of $ϕ(2170)$ to $ϕη$ and $ϕη^\prime$, and compare their ratio $Γ^{ϕ(2170)}_{ϕη}/Γ^{ϕ(2170)}_{ϕη^\prime}$ with the one determined by using the above mentioned experimental data. Considering the theoretical and experimental uncertainties, the lower limit of our theoretical result ($\simeq 2.6$) is close to the upper value obtained ($\simeq 2$) by using the solution II of BESIII for $\mathcal{B}^{ϕ(2170)}_{ϕη}Γ^{ϕ(2170)}_{e^+e^-}$, as well as to the upper limit found ($\simeq 2.8$) when considering the solutions III and IV of the Belle collaboration for $\mathcal{B}^{ϕ(2170)}_{ϕη}Γ^{ϕ(2170)}_{e^+e^-}$.

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arXiv2023

Leading $Λ$ production in future electron-proton colliders

Leading $Λ$ (LL) production in $ep$ collisions at high energies is investigated using the color dipole formalism and taking into account the nonlinear QCD effects. In particular, the impact of the absorptive effects on the LL spectra are estimated considering the kinematical range that will be probed by the Electron Ion Collider (EIC) and by the Large Hadron electron Collider (LHeC). Our results indicate that the LL spectrum is strongly suppressed at small photon virtualities. These results suggest that absorptive effects are not negligible and should be taken into account in order to extract the kaon structure function from data on leading $Λ$ production.

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arXiv2023

$N^*$ states with hidden charm and a three-body nature

In this work we study the formation of $N^*$'s as a consequence of the dynamics involved in the $ND\bar D^*-N\bar D D^*$ system when the $D\bar D^*-\bar D D^*$ subsystem generates $X(3872)$ in isospin 0 and $Z_c(3900)$ in isospin 1. States with isospin $I=1/2$ and mass in the energy region $4400-4600$ MeV are found to arise with spin-parity $J^P=1/2^+$ and $3/2^+$, leading to predictions in this way of the existence of $N^*$ resonances with hidden charm and a three-body nature. We also discuss the possibility of the existence of $Δ_c$ states, i.e., $Δ$'s with hidden charm.

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