Strange Mesons Research Articles

First observation of universality of short range nucleon correlations in the production of strange mesons

First observation of universality of short range nucleon correlations in the production of strange mesons

First Observation of Universality of Short Range Nucleon Correlations in the Production of Strange Mesons

First Observation of Universality of Short Range Nucleon Correlations in the Production of Strange Mesons

Hyperons in neutron stars: studies of hyperon spectroscopy and the hyperon-nucleon interaction with the K-long Facility.

Elucidating the role of strange baryons (hyperons) in neutron stars requires detailed knowledge of hyperon-nucleon interactions in the light (u,d,s) quark sector. The structure of the hyperons and their excitation spectra also directly impact, and are an input to, models of big-bang nucleosynthesis. The upcoming K-long Facility will provide a much-needed intense and clean neutral strange meson beam, from which hyperons can be produced at rates where hyperon structure, hyperon-nucleon interactions and higher-order interactions can be studied with a new level of accuracy and for hitherto unreachable measurements. The new facility has the potential to address long-standing questions surrounding the strange sector of the strong force and its relevance to the structure of atomic nuclei, neutron stars and the cosmos at large. This article is part of the theme issue 'The liminal position of Nuclear Physics: from hadrons to neutron stars'.

Anomalous interactions between mesons with nonzero spin and glueballs

Topologically nontrivial fluctuations control the anomalous interactions for the η and η′ pseudoscalar mesons. We consider the anomalous interactions for mesons with higher spin, the heterochiral nonets with JPC=1+− and 2−+. Under the approximation of a dilute gas of instantons, the mixing angle between nonstrange and strange mesons decreases strongly as J increases, and oscillates in sign. Anomalous interactions also open up new, rare decay channels. For glueballs, anomalous interactions indicate that the X(2600) state is primarily gluonic. Published by the American Physical Society 2024

Contributions of the subprocess K0*(1430)→Kη′ in the charmless three-body B meson decays

We study the contributions for Kη′ pair originating from the scalar intermediate state K0*(1430) in the three-body decays B→Kη′h (h=π, K) within the perturbative QCD approach. The contribution of K0*(1430)→Kη′ is described by the Flatté formula with coupled channels Kπ, Kη, and Kη′. The strong coupling constants gK0*Kη(′) are extracted from gK0*Kπ within flavor SU(3) symmetry. In spite of the strong depression by phase space near the threshold of Kη′, the CP averaged branching fractions for the B→K0*(1430)h→Kη′h decays are predicted to be on the order of 10−8 to 10−5, which are non-negligible for the corresponding three-body B decays. Since the Kη system is almost decoupled from the even-spin strange mesons under flavor SU(3) symmetry, those quasi-two-body B decays with subprocess K0*(1430)→Kη shall have quite small branching ratios and are not taken into account in this work. We also estimate that the branching fraction for K0*(1430)→Kη′ is about one fifth of that for K0*(1430)→Kπ. The predictions for the relevant decays are expected to be tested by the LHCb and Belle-II experiments in the future. Published by the American Physical Society 2024

Open strange and open heavy flavor mesons in asymmetric nuclear matter within quark meson coupling model

Open strange and open heavy flavor mesons in asymmetric nuclear matter within quark meson coupling model

Progress in the Partial-Wave Analysis Methods at COMPASS

Abstract. We study the excitation spectrum of light and strange mesons in diffractive scattering. We identify different hadron resonances through partial wave analysis, which inherently relies on analysis models. Besides statistical uncertainties, the model dependence of the analysis introduces dominant sys tematic uncertainties. We discuss several of their sources for the π−π−π+ and K0S K¯ final states and present methods to reduce them. We have developed a new approach exploiting a-priori knowledge of signal continuity over adjacent final-state-mass bins to stably fit a large pool of partial-waves to our data, al lowing a clean identification of very small signals in our large data sets. For two-body final states of scalar particles, such as K0S K¯, mathematical ambigui ties in the partial-wave decomposition lead to the same intensity distribution for different combinations of amplitude values. We will discuss these ambiguities and present solutions to resolve or at least reduce the number of possible so lutions. Resolving these issues will allow for a complementary analysis of the aJ-like resonance sector in these two final states.

Strangeness in Neutron Stars

In this contribution I briefly review the dynamics of strange mesons and baryons with dense nuclear matter, paying a special attention to their pres ence in the inner core of neutron stars and the consequences for the structure of these compact stars.

Determination of Tsallis parameters for K∗(892)± mesons in inelastic pp, pPb and PbPb collisions

Doubly differential transverse momentum spectra of strange mesons [Formula: see text] and [Formula: see text] within rapidity interval of [Formula: see text] are studied by using Monte Carlo event generators in pp, pPb and PbPb collisions at different center-of-mass energies. The predictions of simulations are compared to the ALICE data. The fitting of doubly differential transverse momentum spectra of ALICE data is performed by using Tsallis distribution function. To check the quality of the fitting, chemical potential is also set to zero value. The extracted values of the non-extensive parameter ([Formula: see text]), a chemical potential [Formula: see text] and effective Tsallis temperature [Formula: see text] for different particle species have been obtained from the thermodynamically consistent Tsallis distribution function. It is observed that the effective Tsallis temperature increases at different center-of-mass energies. The predictions of the MC event generators, i.e. PYTHIA8 CR and HIJING 2.0 are compared to the ALICE data, deviations are observed which may be due to the reshuffling of parton colors and string fragmentation.

Placing of the recently observed bottom strange states BsJ(6063) and BsJ(6114) in bottom spectra

Abstract We employ the heavy quark effective theory (HQET) to give spin-parity quantum numbers for the bottom strange states BsJ(6063) and BsJ(6114) recently observed by the LHCb Collaboration [9]. By exploring flavor-independent parameters $\Delta _{F}^{(c)} =\Delta _{F}^{(b)}$ and $\lambda _{F}^{(c)} = \lambda _{F}^{(b)}$ appearing in the HQET Lagrangian, we calculate the masses of the experimentally missing bottom strange meson states 2S, 1P, 1D. The parameter ΔF appears in the HQET Lagrangian and gives the spin-averaged mass splitting between excited-state doublets (F) and ground-state doublets (H). Another parameter λF comes from first-order corrections in the HQET Lagrangian and gives hyperfine splittings. We also analyze these bottom strange masses by taking 1/mQ corrections, which lead to modifications of parameter terms of $\Delta _{F}^{(b)} =\Delta _{F}^{(c)} + \delta \Delta _F$ and $\lambda _{F}^{(b)} = \lambda _{F}^{(c)}\delta \lambda _F$. Further, we analyze their two-body decays, couplings, and branching ratios via the emission of light pseudoscalar mesons. Based on the predicted masses and decay widths, we tentatively identify the states BsJ(6063) as 23S1 and BsJ(6114) as 13D1. Our predictions provide crucial information for future experimental studies.

CP Violation in Baryon Decays at LHCb

Observations in astronomy suggest that our Universe contains an abundance of matter over antimatter, which can only be explained if the combined CP symmetry is violated. Studies of CP violation have driven the flavor physics with the aim of testing the Standard Model of particle physics and searching for physics beyond it. CP violation is discovered in strange, beauty, and charm meson systems; however, no conclusive sign of CP violation in baryon decays has been observed yet. This review summarizes CP violation studies performed by the LHCb experiment in charmless decays and rare decays of beauty baryons and singly Cabibbo-suppressed decays of charm baryons. A brief on prospects for future LHCb measurements is also discussed.

Study of strange beauty neutral meson decays into vector and pseudoscalar mesons

Study of strange beauty neutral meson decays into vector and pseudoscalar mesons

Mass spectroscopy, decays and mixing parameters of open flavour bottom and bottom strange mesons using instanton induced potential with additional confinement

The mass spectra for the heavy-light ; q = u or d and s bottom and bottom strange mesons are computed based on the instanton induced interactions inspired potential along with additional confinement term. Spectroscopic predictions for ground, radial and orbital states are provided. The low-lying states 1S and 1P are found to be in an excellent agreement with the PDG reported values. The predicted mass spectra strongly support the newly observed B J (5840) and B J (5970) by LHCb collaboration as 21 S 0 and 13 D 3 states respectively. Apart from the mass spectra, the other observables like radiative transitions, decay constant for 1S state, the di-leptonic rare decays and the Cabibbo allowed two body hadronic decays are also predicted. The predicted value of branching ratio of rare decay as 3.65 ×10−9 is in excellent agreement with the recent measurement of LHCb of . The branching ratios of color favoured decays and are found to be exceeding by factor of two as compared to the PDG listed values. The mixing parameters of , ΔM q , x q and χ q are obtained as 0.512, 0.755 and 0.1877 respectively which are very close to the PDG listed values of 0.5065 ± 0.0019, 0.769 ± 0.004 and 0.1858 ± 0.0011 respectively.

Production of Strange Mesons, Hyperons and Hypernuclei in Ag\(+\)Ag Collisions at \(\sqrt {s_{NN}}=2.55\)~GeV measured with HADES

Production of Strange Mesons, Hyperons and Hypernuclei in Ag\(+\)Ag Collisions at \(\sqrt {s_{NN}}=2.55\)~GeV measured with HADES

In-medium effects in ϕ meson production in heavy-ion collisions from subthreshold to relativistic energies

We investigate the hidden strange $\phi$ meson production in heavy-ion collisions from subthreshold ($E_{kin}\approx 1$ A GeV) to relativistic ($E_{kin}\approx 21$ A TeV) energies as well as its coupling to the open strange mesons (kaons, antikaons) and their productions. Our study is based on the off-shell microscopic Parton-Hadron-String Dynamics (PHSD) transport approach which is applicable for the dynamical description of strongly interacting hadronic and partonic degrees-of-freedom created in heavy-ion collisions. Implementing novel meson-baryon and meson-hyperon production channels for $\phi$ mesons, calculated within a T-matrix coupled channel approach based on the extended SU(6) chiral effective Lagrangian model, along with the collisional broadening of the $\phi$-meson in-medium spectral function, we find a substantial enhancement of $\phi$ meson production in heavy-ion collisions, especially at sub- and near-thresholds. This allows to describe the experimentally observed strong enhancement of the $\phi/K^-$ ratio at low energies without including hypothetical decays of heavy baryonic resonances to $\phi$ as in alternative approaches. Moreover, we show that in spite of a stronger contribution from enhanced $\phi$ to $K^-$ production, the majority of the experimental data for different A+A systems at low energies favor the scenario with in-medium modifications of the kaon and antikaon properties in the hot and dense environment. Moreover, we study the influence of the final state interactions of $K, \bar K$ mesons on the reconstruction of $\phi$'s by the by invariant mass method.

Open strange meson $K^\pm_1$ in hot and dense nuclear matter

Using the unification of the chiral SU(3) model and QCD sum rules, we deduce the in-medium properties of K^\pm_1K1± meson. Within the chiral SU(3) model, medium modified gluon and quark condensates are evaluated through their interactions with the scalar fields (\sigmaσ, \zetaζ, \deltaδ, and \chiχ). These condensates are further used as input in the Borel transformed equations of QCD sum rules to evaluate the in-medium mass of strange K^\pm_1K1± meson. The in-medium property of the above meson can be used to study the restoration of chiral symmetry in nuclear matter.

News from the light and strange meson sector

Recent high-quality data sets from various experiments grant new insights into the excitation spectrum of light mesons, which are composed of up, down, and strange quarks. In the non-strange light-meson sector, many recent experimental and theory efforts are focused on the search for so-called exotic states, which are states beyond the na¨ıve constituent quark-model. To this end, various potential decay modes of exotic states are studied at experiments such as GlueX or COMPASS. In addition, there is recent progress in the understanding of so-called non-resonant processes, which act as background in searches for light mesons, as well as in the prediction of light mesons from lattice QCD. While the non-strange light-meson spectrum is already mapped out rather well, many predicted strange mesons have not yet been observed experimentally or need further confirmation. Recent high-precision data from experiments such as LHCb and BESIII allow us to study strange mesons in heavy-meson decays. Alternatively, strange mesons are studied in diffractive scattering of high-energy kaon beams. The so far world’s largest data set on the diffractively produced K−π −π + final state was measured by the COMPASS experiment. A recent analysis of this data covers a large variety of strange mesons over a wide mass range in a single, self-consistent analysis

Test of lepton universality in beauty-quark decays

The standard model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton–proton collision data collected with the LHCb detector at CERN’s Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the standard model, such as a new fundamental interaction between quarks and leptons.

On Asymptotic Regge Trajectories of Heavy Meson Resonances

We performed the analysis of the asymptotic behavior of Regge trajectories of nonstrange and strange mesons and found that thewidth of heavy hadrons for these trajectories cannot linearly depend on their mass. Such a finding clearly demonstrates that a widely spread belief on the linear mass dependence of the resonance width contradicts the linearity of Regge trajectories on theMandelstam variable s. Using the data on masses and widths for ρJ––, ωJ––, aJ++,, and fJ++ mesons with the spin values J ≤ 6 and for K*J mesons with J ≤ 5, we extracted the parameters of the asymptotically linear Regge trajectories predicted by the finite-width model of quark gluon bags. It is shown that the parameters obtained for the data sets B and D are consistent with the cross-over temperaturedetermined by the lattice QCD simulations at the vanishing baryonic density and with the kinetic freeze-out temperature of early hadronizing particles found in relativistic heavy ion collisions at and above the highest SPS energy. Comparing the resonance width of sets B and D evaluated at the masses of Z and W bosons, respectively, we discovered that the calculated width values match that of the gauge bosons. We argue that such matches provide us with indirect, but the first experimental evidence for the compositeness of Z and W bosons. Based on these findings, we assume that Z, W, and Higgs bosons have the Regge trajectories which are similar to the asymptotic trajectories of the studied mesons. The predictions for the masses and widths of the Regge partners of Z and W bosons and for the mass dependence of the widths of Higgs boson Regge partners along with the values for the mass and width of the scalar Higgs mesons are made as well.

Investigating the K1(1270) – K1(1400) Mixing Angle via QCD Sum Rules

In this work, we investigated the mixing between strange axial vector mesons K1(1270) and K1(1400) by using QCD Sum Rules approach. Since these states couple to the same interpolating currents, we defined them in terms of orbital angular momentum eigen states K1A and K1B. By using the axial vector and tensor interpolating currents which are almost purely coupling to K1A and K1B, and then employing the orthogonality of the physical states, we obtained an analytical expression for the K1 mixing angle. We performed a Monte Carlo based numerical analysis to estimate the value of the mixing angle.