International Journal of Modern Physics A

Recent experimental studies of meson spectroscopy at the B-factories are reviewed. This report covers updates of studies for exotic candidates of both charmonium-like and bottomonium-like particles as well as searches and measurements of other new or known states including conventional heavy quarkonia.

Results based on 106 M ψ′ events and about 226 M J/ψ events acquired with the BESIII detector at BEPCII are reported, including a confirmation of the BESII threshold enhancement in , branching ratios for χ_cJ → π⁰π⁰ and ηη, and first measurements of the branching ratios for ψ′ → π⁰h_c and h_c → γη_c, as well as measurements of the mass and width of the h_c.

In recent years a large number of new states in the charm sector was discovered above the first inelastic threshold that not at all match to the predictions of the quark model, which on the other hand was extremely successful below that threshold. Since most of those states are located close to a two–hadron threshold, many authors proposed a molecular nature for them. In this talk we will collect the evidences and discuss how the picture can be tested further. In addition, if hadron loops induce non-perturbative effects above the inelastic threshold, one should also expect them to have some impact on the properties of standard charmonia. In the last part of this write-up an effective field theory is introduced that allows one to investigate this issue systematically.

Collisions of heavy atomic nuclei at very high beam energies allow to create and study hot QCD matter under laboratory-controlled conditions. Measurements at the SPS and RHIC facilities have yielded compelling evidence for the formation of this novel state of matter, the so-called Quark-Gluon Plasma (QGP). Due to their large mass, heavy quarks (charm and bottom) are believed to be predominantly produced in the initial state of the collision so that they probe the entire lifetime of the QGP. Thus, the investigation of heavy-flavor meson production in nucleus-nucleus collisions provides profound insight into the QGP properties. In this paper we review recent results from the RHIC facility on heavy-flavor meson production and their interaction with the QCD matter on the partonic level.

The recent, selected results on meson production at HERA electron-proton collider from the H1 and ZEUS experiments are presented and interpreted within the framework of quantum chromodynamics.

We provide a glimpse of recent progress in meson physics made via QCD's Dyson-Schwinger equations with: a perspective on confinement and dynamical chiral symmetry breaking (DCSB); a précis on the physics of in-hadron condensates; results for the masses of the π, σ, ρ, a₁ mesons and their first-radial excitations; and an illustration of the impact of DCSB on the pion form factor.

The roles of the COSY-TOF and COSY-ANKE spectrometers in the measurement of strange meson production are briefly reviewed, mainly in connection with new results on the pp → K⁺pΛ, pp → K⁺pΣ⁰ and pp → K⁺nΣ⁺ reactions.

With the HADES spectrometer at GSI we have studied dilepton production in various collision systems from elementary N+N, over p+A, up to the medium-heavy Ar+KCl system. We have confirmed the puzzling results of the former DLS collaboration at the Bevalac. While we have traced the origin of the excess pair yield in C+C collisions to elementary p+p and n+p processes, we find a significant contribution from the dense phase of the collision in larger Ar+KCl system. From recently obtained e⁺e^- pair spectra in p+p and p+Nb interactions at 3.5 GeV kinetic beam energy the inclusive production cross sections for neutral pions, η , ω and ρ mesons are extracted for the first time at this beam energy. Furthermore, the production mechanisms of the vector mesons, which are not known at these energies, are investigated. The direct comparison of p+p and p+Nb data allows us to investigate in-medium mass modifications of vector mesons at nuclear ground state density.

On the other hand, exclusive production of ω and η mesons in p+p reactions at 3.5 GeV were studied via their π⁺π^-π⁰ decay channel. Production cross sections and angular distributions for both states were determined.

CERN has a long tradition of pursuing fundamental physics on a variety of energy scales. For anti-protons CERN famously produced the high-energy SPS beam but also the world's only and unique sources of low-energy anti-protons – first the Low Energy Anti-proton Ring (LEAR) and thereafter the Anti-proton Decelerator (AD).

The scientific demand for low-energy anti-protons at the AD continues to grow. More rapid progress and much higher measurement precision might be possible by upgrading the AD to increase and optimize the number of cold anti-protons that can be trapped and accumulated. To achieve this the construction of an Extra Low ENergy Antiproton (ELENA) ring is proposed which involves both the addition of a small storage ring and electrostatic beam lines to the experiments. The design parameters have been carefully studied and agreed upon over several years. At least during the next decade there is no alternative low-energy anti-proton source for physics to be done now.

Results presented here constitute the first achievements of the rich QCD physics program of the CMS experiment at LHC. Using data from proton-proton collisions at center-of-mass energies of 0.9, 2.36 and 7 TeV, measurements of charged particle yields, Bose-Einstein correlations and underlying event features have been produced. These are among the first results concerning the properties and interactions of charged hadrons at the new energy frontier accessible at LHC.

Experimental tests of the Λ(1405) properties are suggested. These could reflect the position and shape of this state in the channel. The first test consists in precise determinations of the level widths in the highest accessible K-mesic atom states. One needs to study the dependence of these widths on the binding energy of the valence protons in the involved nuclei. The second test consists in the measurement of radiative transitions from the P-wave atomic hydrogen levels to the Λ(1405) state. In both cases one can study the absorptive part of scattering amplitude in the subthreshold region.

The present status and future physics program of Central Production using the STAR detector at RHIC will be described. The program focuses on particle production resulting from the Double Pomeron Exchange (DPE) process. Forward protons from the DPE interaction are detected in the Roman Pot system installed at 55.5 m and 58.5 m on both sides of the STAR interaction point. The recoil system of charged particles from the DPE process is measured in the STAR Time Projection Chamber (TPC). The first data were taken in 2009 during the RHIC-Run 9 using polarized proton-proton collisions at . The preliminary spectra of two pion and four pion invariant mass reconstructed by STAR TPC in central region of pseudo-rapidity |η| < 1, are presented. Plans to take data with the current system at and plans to upgrade the forward proton tagging system, so that it can reach higher masses and obtain large data samples in searching for glueballs that could be produced in the DPE process, are also discussed.

The AMADEUS experiment will give a first conclusive answer to the question on the existence of the deeply bound kaonic states, which is discussed quite controversially in the hadron physics community today. Using the KLOE detector system together with the AMADEUS apparatus an exclusive measurement will be performed that means a complete determination of all formation and decay channels of kaonic nuclear states is possible in the reaction using ³He and ⁴He targets. The upgraded high luminosity DAɸNE e⁺e^- collider at LNF is essential for successful measurements. Using missing mass and invariant mass spectroscopy a conclusive observation of these exotic objects should be reachable, and their properties, such as binding energies, total and partial widths, size and density could be determined. Thus, will open a new field in the spectroscopy of di- and tri-baryon systems with strangeness (S = -1).

FINUDA (FIsica NUcleare a DAɸne) is a spectrometer built to study the interactions of stopped K^- on nuclei, with emphasis on spectroscopy and decay of Λ-hypernuclei. Due to the nice performances of the apparatus and its ability to reconstruct secondary vertices, it proved suited to study also final states with several particles (including neutron), hence greatly enlarging the physical topics that could be addressed.

We discuss recent results and open problems in baryon-baryon interactions at small relative energies. Here we concentrate on pp and pn final state interactions in pion production reactions and on Λp interactions in kaon production.

The SIDDHARTA experiment aims a precise measurement of K-series kaonic hydrogen x-rays and the first-ever measurement of the kaonic deuterium x-rays to determine the strong-interaction energy-level shifts and widths of the lowest lying atomic states. These measurements offer a unique possibility to precisely determine the isospin-dependent kaon-nucleon (KN) scattering lengths [1] which are directly connected with the physics of the KN interaction. Kaonic Helium transitions to the 2p level (L-lines) were as well measured. The experiment has been performed at the DAΦNE e⁺e^- collider which produces the Φ-resonance. The resulting low energy negative charged kaons, coming from the Φ decay, are well suited to be stopped efficiently in a high density gas target for producing such kind of atoms. As x-ray detectors, we employed 144 Silicon Drift Detectors developed especially for this experiment, having good energy resolution of 140 eV FWHM at 6keV and time resolution of sub-micro seconds. The data taking was completed in November 2009. In this paper, an overview of this experiment and preliminary results are presented, together with future plans.

dynamics and its realization through the Λ(1405) resonance are introduced, highlighting recent theoretical studies of K^-pp quasibound states. The role of mesons in nuclei and in multistrange hadronic matter is discussed within RMF calculations.

In this article, we consider theoretically the d + d reaction for the formation of the η-⁴He bound state. We evaluate the formation rate and show expected spectra using a simple theoretical model with Green's function method.

Meson electro-production is used in Hall C at Jefferson Lab to probe nucleon, baryon and nuclear structure. The experimental program in Hall C includes studies of semi-inclusive pion production, p, d(e, e′π^±)X, where low energy factorization has been observed, suggesting that these reactions can be used to probe nucleon structure, including transverse momentum distributions of quarks, at energies available at JLab after the upcoming 12 GeV upgrade.

At the laser electron photon facility at SPring-8 (LEPS), meson photoproduction reactions have been studied by using highly polarized photon beams produced by the Compton backscattering of the laser off the high energy electrons. The recent activities at the LEPS experiment are overviewed. From the recent results, the meson photo-production reactions at the backward angles, and the photoproduction of Λ(1405) are discussed. In order to extend our study to wider kinematical range, construction of the new beamline and the large acceptance detector has been started.

During the last few years photoproduction of mesons off light target nuclei (²H, ³He, ⁷Li) has been systematically studied at the tagged photon beams of the Bonn ELSA accelerator and the Mainz MAMI accelerator. The experiments used the combined Crystal Barrel/TAPS setup in Bonn and the Crystal Ball/TAPS setup in Mainz. Most measurements investigated meson photoproduction off the neutron for many different reaction channels in order to establish the iso-spin structure of electromagnetic resonance couplings. This project used mostly deuteron targets. The measurements with the He and Li targets aimed at the search for η-mesic nuclei and hadron in-medium properties.

The 'kaonic atoms puzzle' is a conflict between phenomenological potentials and potentials constructed from more fundamental approaches. Whereas the former are typically 180 MeV deep, the latter are less than 50 MeV deep. Extrapolating to neutron star densities only the former could sustain kaon condensation. Likewise only the deep potential could support the recently proposed clusters of nucleons strongly bound by an antikaon. Careful re-analyses of the world's data on kaonic atoms could not suggest an explanation to the puzzle. Repeating some of the 30-40 years old experiments seems the only way to proceed. We propose to repeat measurements for a small group of kaonic atom species, namely C, Si, Ni, Sn and Pb. It is found that fits to the data for any four of these five targets reproduce all the features obsereved in fits to the full set of 23 targets.

Studies of light meson decays are the key experiments for the WASA detector at COSY-Jülich. One of the world largest data samples of the η meson decays have been recently collected in the pd →³Heη and in the pp → ppη reactions. The status of the analysis of various decay channels and the further plans for the light meson decay program are presented.

New results on CP violation measurements performed on events collected at the Υ(4S) in upto 432 fb^-1 of data at the BABAR experiment and upto 770 fb^-1 of data collected at the Belle experiment. The measurements provide new constraints on the unitarity triangle angles γ and β. The measurements presented include: results from BABAR and Belle on CPV using Dalitz plot analyses, measurements of the CKM angle γ using a GLW analysis of B → DK^± decays and from using B → D*°K^- decays and results on yCP using D° mixing.

I review here the status of tests of discrete symmetries in nuclear beta decay, including neutron decay. The focus is given on tests of maximal parity violation, tests of time reversal invariance as well as searches for parity and time reversal invariant exotic interactions. Along with the most sensitive results, I present also some recent achievements of precision beta decay experiments as well as selected ongoing project.

I give a brief overview of the exploration of baryon properties in meson photo- and electroproduction. These processes provide ample information for the study of electromagnetic couplings of baryon resonances and to search for states, yet to be discovered. The CLAS detector, combined with the use of energy-tagged polarized photons and polarized electrons, as well as polarized targets and the measurement of recoil polarization, provide the tools for a comprehensive nucleon resonance program. I briefly present the status of this program, prospects for the next few years, and plans for the Jefferson Lab 12 GeV upgrade.

Current and upcoming experiments at the ELectron Stretcher Accelerator (ELSA) facility will determine polarization (or spin) observables for photoproduction processes involving baryon resonances. Differences between the predictions for these observables can be large, and so conversely they provide strong constraints in the analyses that aim at studying the properties of known resonances and at searching for hitherto unobserved states. The current effort with the Crystal Barrel/TAPS detector at ELSA is to utilize highly-polarized frozen-spin (butanol) and deuterium targets in combination with polarized photon beams. I will discuss recent spectroscopy results and present a brief status of the polarization program.

With an effective Lagrangian approach, we give a full analysis on the NN → NNππ and reactions by exploring the roles of various resonances with mass up to 1.72 GeV. We find large contributions from Δ, N*(1440), Δ(1600) and Δ(1620) resonances. Our calculations also indicate sizeable contributions from nucleon poles for the energies close to the threshold. A good description to the existing data of different isospin channels of NN → NNππ and for beam energies up to 2.2 GeV is reached. Our results provide important implications to the ABC effect and guildlines to the future experimental projects at COSY, HADES and HIRFL-CSR. We point out that the at FAIR could be an essential place for studying the properties of baryon resonances and the data with baryon and anti-baryon in final states are worth analyzing.

The charge-exchange reaction π^-p → ω(780)ɸ(1020)n is studied with the VES setup. The (ωΦ) system is observed at relatively low background. Its invariant mass distribution peaks near threshold. The two-particles partial wave analyses shows that the J^PC = 0⁺⁺ state dominates. Comparison with scalar wave in ωω system at the comparable mass gives evidence for violation of the OZI rule. Another subject is a search for possible transition f₀(980) → a₀(980), which violates the isospin symmetry.

The ALICE experiment is aimed at studying the properties of the hot and dense matter produced in heavy-ion collisions at LHC energies. In the first years of LHC operation the ALICE physics program will be focused on Pb-Pb and p-p collisions. The latter, on top of their intrinsic interest, will provide the necessary baseline for heavy-ion data. After its installation and a long commissioning with cosmic rays, in late fall 2009 ALICE participated (very successfully) in the first LHC run, by collecting data in p-p collisions at c.m. energy 900 GeV. After a short stop during winter, LHC operations have been resumed; the machine is now able to accelerate proton beams up to 3.5 TeV and ALICE has undertaken the data taking campaign at 7 TeV c.m. energy. After an overview of the ALICE physics goals and a short description of the detector layout, the ALICE performance in p-p collisions will be presented. The main physics results achieved so far will be highlighted as well as the main aspects of the ongoing data analysis.

The physics program of the PANDA experiment at FAIR, studying antiproton-proton and antiproton-nucleus collisions, is described. A brief overview of the full program is given, but the emphasis is laid on spectroscopy of hidden and open charm mesons, as well as of multi-strange baryons. In addition the investigation of the J/ψ-nucleon interaction using transparency measurements in antiproton-nucleus collisions is discussed.

The basic motivation of the KLOE-2 experiment is the test of fundamental symmetries and Quantum Mechanics coherence of the neutral kaon system, and the search for phenomena beyond the Standard Model in the hadronic and leptonic decays of ground-state mesons. Perspectives for experimentation by means of the KLOE-2 apparatus equipped with the inner tracker, new scintillation calorimeters, and the γγ taggers at the DAΦNE electron-positron collider upgraded in luminosity and energy are presented.

The J-PARC Hadron Facility is designed as a multipurpose experimental facility for a wide range of particle and nuclear physics programs, aiming to provide the world highest intensity secondary beams. The first primary beam has been successfully extracted and transported to the beam dump on January 2009. Currently three secondary beam lines come into operation, and the new beam line will be completed in the early summer of 2010. Various experimental programs are proposed at each beamline and some of them are preparing to start physics run. Most of the experimental researches concerns the studies of hypernuclei and searches for new hadronic states. As the first experiment at the J-PARC Hadron Facility, search for the Θ⁺ pentaquark via pion-induced hadronic reaction will be performed in the autumn of 2010. The current status and recent results of the commissioning for the beam line are reported.

In this article we present studies of the near threshold pp → ppK⁺K^- reaction in view of the K⁺K^- final state interaction. The investigations include analysis of both the low-energy K⁺K^- invariant mass distributions measured by COSY-11 collaboration at excess energies of Q = 10 MeV and Q = 28 MeV and the near threshold excitation function for the pp → ppK⁺K^- reaction. As a result of these studies we have estimated the K⁺K^- scattering length more precise compared to the previous analysis based only on the analysis of the differential cross sections.

Rare B^± decays to three charged kaons are analysed. The weak decay amplitudes are derived in the QCD factorization approach. The strong final state interactions between pairs of kaons are described using the kaon scalar and vector form factors. The scalar form factors at low K⁺K^- effective mass distributions are constrained by chiral symmetry and are related to the coupled channel meson-meson amplitudes describing all the transitions between three channels consisting of two kaons, two pions and four pions. The vector form factors are fitted to the data on e⁺e^- collisions. The model results are compared with the Belle and BaBar data.

We report on investigations of B-meson decays into baryons with the BABAR detector. The comparison of different decay channels reveals that higher multiplicities are preferred for these decays. Furthermore, an enhancement in the invariant baryon-antibaryon mass distribution can be observed in several baryonic decay modes. In addition, the study of baryon resonances seen in baryonic B-meson decays is presented.

We have calculated the kinematical correlations between charged leptons from semileptonic decays of open charm/bottom as well as leptons produced in the Drell-Yan mechanism in proton-proton collisions at BNL RHIC. Presented production rates for open charm and bottom were estimated by a detailed analysis of so-called nonphotonic electrons. The distributions for charm and bottom quarks pairs are calculated in the k_t-factorization approach with the help of the Kwieciński unintegrated parton distributions. The hadronization of heavy quarks is done by means of Peterson et al. fragmentation function. The semileptonic decay functions are found by fitting recent semileptonic data obtained by the CLEO and BABAR. We get good description of recent PHENIX data.

Within the chamonium-threshold QCD theory, the two-photon spectroscopies of charmonia will provide the unique test on the non-perturbative treatment. With the high luminosity and excellent detector in the BESIII experiment, the two-photon transition from ψ(2S) to J/ψ is firstly observed and the preliminary result of the measurement of the branching fraction is given.

Data from the absorption reaction on light nuclei, ^6,7Li, ⁹Be and ¹²C, have recently been collected by FINUDA at DAΦNE (LNF). The studies rely on Λp(d,t) correlations. Regardless of A, the Λp(d,t) pairs are found to be preferentially emitted in opposite directions. Moreover the analysis are based on the Λp(d, t) invariant mass and missing mass distributions, which allow the structure of bound [K^-NN(NNN,NNNN)] systems in nuclei to be examined.

We investigated the dependence of the K^-d scattering length on two models of interaction, providing one or two poles for the Λ(1405) resonance. The system is described by coupled-channels Faddeev equations in AGS form. The two-body interaction models reproduce all existing experimental data on K^-p scattering and K^-p atom level shift. The comparison with several approximations, commonly used for such calculations, was done.

The J-PARC E15 experiment aims to search for the lightest kaonic nuclear states, namely K^-pp, using in-flight (K^-, n) reaction on ³He. In this experiment, the missing mass in the (K^-, n) reaction and the invariant mass of the decay such as K^-pp → Λp → pπ^-p will be measured simultaneously. In this article, the experimental feature and the present status are presented.

We search for the most basic kaonic nuclear state, K^-pp, by studying an exclusive p + p → p + Λ + K⁺ process at T_p = 3.1 GeV using FOPI apparatus at GSI, Darmstadt, Germany. A possible signature of the K^-pp is searched as a p + p → K^-pp + K⁺ → p + Λ + K⁺ reaction in the event sample of pΛK⁺ three body process. A missing-mass ΔM(K⁺) spectrum, a Λp invariant-mass M(Λp) spectrum and a mono energetic kaon will characterize such a two body process. The reaction channel is basically the same as the one which T. Yamazaki et al. very recently reported a possible hint of such state with M = 2267 MeV/c² and Γ = 118 MeV from a re-analysis of the DISTO experiment data. The DISTO data was taken at T_p = 2.85 GeV. The beam energy of the FOPI experiment is chosen to optimize the signal to background ratio and also to see the background shape separately. FOPI data taking took place in August-September 2009 and analysis is currently undergoing.

In this contribution we address the question whether kaon condensation could occur in strongly interacting self-bound strange hadronic matter. In our comprehensive dynamical relativistic mean-field (RMF) calculations of nuclear and hypernuclear systems containing several antikaons we found saturation of separation energy as well as the associated nuclear and density distributions upon increasing the number of mesons. The saturation pattern was found to be a universal feature of these multi-strangeness configurations. Since in all cases the separation energy does not exceed 200 MeV, we conclude that mesons do not provide the physical "strangeness" degrees of freedom for self-bound strange hadronic matter.

We present recent studies of charmonium multiquark states. We use different interacting models and numerical methods to study deeply bound four-quark states and meson-meson molecules. No deeply bound four-quark states are found in our analysis. A nice description of the X(3872) is obtained as a coupled channel state.

We calculate the exclusive cross section for the processes e⁺e^- → D⁰D^-π⁺ and e⁺e^- → D⁰D*^-π⁺ using a constituent quark model which successfully describes the sector.

We present recent results from charmonium and open charm production at the LHCb experiment at CERN, Geneva. We concentrate on studies for the measurement of the cross section pp → J/ψX in its decay channel with two muons, showing the agreement of the simulation with the data in few key distributions. We also show the reconstructed modes of D⁰ → K^-π⁺, D⁰ → K^-π⁺π⁰, and and their prospects.

Recent results on Charmonium spectrum and decays at Beijing Spectrometers III (BES-III) experiment will be presented. This report includes the following topics: 1, first measurement of the transition rates of ψ′ → π⁰h_c and h_c → γη_c, and improved measurement of the mass and width of the h_c; 2, observations of χ_cJ → VV, with VV being ɸɸ, ωω and ωɸ, χ_cJ → ωɸ as well as χ_c1 → ɸɸ and ωω are first observations; 3, improved measurement of the branching fractions of χ_cJ decay into neutral pseudo-scalar pairs, including χ_c0,2 → π⁰π⁰ and χ_c0,2 →ηη. All these measurements are based on the world largest ψ′ data sample collected with the BES-III detector at the Beijing Electron Positron Collider II (BEPC-II).

We consider exclusive double diffractive production of polarised axial-vector χ_c(1⁺) and tensor χ_c(2⁺) charmonia in proton-(anti)proton collisions at Tevatron energy. The corresponding amplitudes for these processes are derived within the k_t-factorisation approach. Contributions from different polarisation states of axial-vector and tensor charmonia are quantified. Corresponding experimental consequences are discussed.

With the advent of chiral perturbation theory, the low-energy effective field theory of QCD, high accuracy calculations for hadronic reactions have become possible. We review the recent developments in the reaction NN → NNπ in chiral EFT.

We present a calculation of the π^-d scattering length in the framework of chiral perturbation theory (ChPT) with focus on virtual-photon effects. Using data on pionic deuterium and pionic hydrogen atoms, we extract the isoscalar and isovector pion–nucleon scattering lengths and , as well as—via the Goldberger–Miyazawa–Oehme sum rule—the charged-pion–nucleon coupling constant

We study charge symmetry breaking (CSB) in the reaction pn → dπ⁰. CSB manifests itself in a forward-backward asymmetry of the differential cross section measured recently at TRIUMF. A complete calculation of CSB effects at leading order in chiral perturbation theory is performed. A new leading-order operator is included. This allows us to extract the strong contribution to the neutron-proton mass difference from the analysis. The value obtained is consistent with the result of Gasser and Leutwyler based on the Cottingham sum rule and with an extraction from lattice QCD.

Charge symmetry breaking effects can be used as an experimental tool to study quark mass effects. Using recent high precision data from TRIUMF and IUCF an international theory collaboration is working on a consistent description within the framework of chiral pertubation theory. The WASA-at-COSY collaboration has started an experimental program extending the studies on the reaction dd → ⁴Heπ⁰ towards higher excess energies in order to provide necessary information on the contribution of p-waves. First preliminary results on the total cross section at Q = 60 MeV are presented.

One of the key experiments of the physics program of WASA-at-COSY is the determination of the p- wave contributions to the Charge Symmetry breaking amplitude in the reaction dd → ⁴Heπ⁰ at 1.2 GeV/c beam momentum. As a first step towards realisation of this goal the Charge Symmetry conserving reaction dd → ³Henπ⁰ was measured. For an overall theoretical analysis of CSB reactions in terms of Chiral Perturbation Theory this reaction channel will be used to gain information on the deuteron-deuteron initial state interaction for s- and p- wave pion production.

The SIDDHARTA experiment (SIlicon Drift Detector for Hadronic Atom Research by Timing Application) had the aim to perform kaonic atoms X-ray transitions measurements, to better understand aspects of the low-energy QCD in the strangeness sector. The experiment combined the excellent low-energy kaon beam generated at DAΦNE, allowing to use gaseous targets, with excellent fast X-rays detectors: Silicon Drift Detectors. SIDDHARTA was installed on DAΦNE in autumn 2008 and took data till late 2009. Apart of the kaonic hydrogen and kaonic deuterium measurements, we have performed the kaonic helium transitions to the 2p level (L-lines) measurements: for the first time in a gaseous target for helium4 and for the first time ever for kaonic helium3. The interest for such type of measurement was rather high, being it triggered by two reasons: the so-called "kaonic helium puzzle" (even if this was solved by KEK-PS E570 experiment, but a cross-check was useful) and some theoretical predictions of possible high energy shift (at the level of 10 eV). In this paper the preliminary results for the measurements to the 2p level (L-series) for kaonic helium4 and kaonic helium3 are presented.

X-ray spectroscopy is an advantageous tool for investigation of the shift and width of the energy levels in kaonic atoms, evoked due to strong interaction between nucleus and kaon. In order to study the 2p level shift in kaonic ³He, the X-ray transition 3p→2d in liquid kaonic ³He will be measured with a precision of <2 eV in the E17 experiment at J-PARC. To reach this desired precision, a well designed setup, in-situ calibration and state-of-the-art semiconductor detectors will be used. The idea and the preparation status of the whole setup will be reported in this article.

We outline the extension of the globally chirally invariant N_f = 2 linear sigma model with vector and axial-vector degrees of freedom to N_f = 3. We present preliminary results concerning the scalar meson masses.

In the combined analysis data on multi-channel ππ scattering and J/ψ decays, a status and parameters of the scalar mesonic resonances are obtained.

The structure and different decay modes of the X(3872) resonance are described in a constituent quark model as dynamically generated by the coupling of a molecular DD* state with a state.

We also obtain in the D*D* J^PC = 1^-- channel a bound state that can be identify with the Y(4008) charmonium state. Other possible molecular states in the hidden bottom sector are discussed.

The decay of Λ(1405) into Σ⁰π⁰ was studied in p+p collisions at E_Kin=3.5 GeV, measured by the High Acceptance Di-Electron Spectrometer (HADES). To extract the line shape of the Λ(1405), special techniques have been developed to describe the misidentification background and extract the contributions of different production channels.

Within an extended chiral constituent quark model, three- and five-quark structure of the S₀₁ resonance Λ(1405) is investigated with respect to the coupling constants and . Our findings corroborate with about 50% of five-quark admixture in the Λ(1405) needed in reproducing the strong decay width, Γ_{Λ(1405)→(Σπ)°}.

One of the objectives of the physics programme of the WASA-at-COSY facility is to study the isospin violating η hadronic decays into π⁺π^-π⁰ systems driven by the term of QCD Lagrangian which depends on the d and u quark mass difference. These studies can be made in terms of the Dalitz plot parameters describing the density population which is proportional to the square of the amplitude |A(x, y)|². This contribution describes the current status of the analysis of the η → π⁺π^-π⁰ decay in the pd →³ Heη and as well in the pp → ppη reaction with WASA-at-COSY.

We present the results of our QCD analysis for quark distributions and structure functions for polarized deep inelastic scattering of leptons on nucleons and nuclei using the Jacobi polynomials up to NLO approximation. Finally by having proton and also neutron structure functions, we have enough motivation to extract ³He and ³H polarized structure functions.

The ABC effect — an intriguing low-mass enhancement in the ππ invariant mass spectrum — is known from inclusive measurements of two-pion production in nuclear fusion reactions. Exclusive measurements have been carried out at CELSIUS/WASA and WASA-at-COSY for the fusion reactions leading to d, ³He and ⁴He. They all reveal this effect to be of isoscalar nature and associated with a narrow Lorentzian-shaped structure in the total cross section. The latter could point to the formation of an isoscalar resonance, which couples to the pn channel as well as to an intermediate ΔΔ state.

The search for the decay η → e⁺e^- was carried out using the WASA detector at the COSY storage ring. Data were taken during a two week experimental run in Sept-Nov 2008 in which about 10⁷ η mesons were collected from the reaction of pp → ppη at energy of 1.4 GeV. Background studies were performed for several different reactions. The performance of the WASA detector for the measurement of electron-positron pairs based on the single Dalitz decay of the η meson was studied. We also identified a statistically significant data sample of other more frequent leptonic decays.

The study of the charmonium system is a powerful tool to understand the strong interaction. In annihilations studied with , the mass and width of the charmonium state, such as h_c, will be measured with an excellent accuracy, determined by the very precise knowledge of the beam resolution and not limited by the resolution of the detector. The analysis of h_c demonstrates the feasibility to accurately determine a specific final state in the spectrum of charmed mesons. The preliminary background analysis of the decay competing with a signal channel is under control. A comparison of three decay modes of charmonium h_c via the electromagnetic transition is presented.

Parameters of ρ-like resonances are obtained in the multichannel analysis of the ππ-scattering data below 1.9 GeV and a possible classification of the resonance states is discussed. In the 3-channel analysis, we confirmed the existence of the ρ(1250) meson and showed that the simultaneous existence of the ρ(1450) and ρ(1250) mesons does not contradict the data. The analysis indicates an importance of presence of some effective channel with the threshold at 1512 MeV, which might be interpreted as the ρσ channel.

Photoproduction process γp → Vp has been mesured recently at HERA. We compare our results with the recent data. The corresponding amplitude is used to predict the cross section for exclusive production in pp and collisions. Here we present distribution in rapidity and transverse momentum of vector mesons for Tevatron and LHC energies. The absorption effects are discussed.

Net proton rapidity distributions are calculated, reproduce very well data obtained at AGS, SPS, RHIC and predict results for the LHC experiment.¹ Presence of non-ideal plasma effects due to strongly coupled plasma in the early stage of relativistic heavy-ion collisions is investigated in the framework of non-conventional statistical mechanics.

We shortly discuss results on the isospin dependence of the η′ production cross section in nucleon-nucleon collisions, results of comparative analysis of the invariant mass distributions for the pp → ppη′ and pp → ppη reactions, and we present the value of the total width of the η′ meson as derived directly from the mass distribution measured with the mass resolution of 0.3 MeV/c².

We present the results of a Bayesian analysis of a Regge model for K⁺Λ photoproduction. The model is based on the exchange of K⁺(494) and K*⁺(892) trajectories in the t-channel. For different prior widths, we find decisive Bayesian evidence (Δ ln Ƶ ≈ 24) for a K⁺Λ photoproduction Regge model with a positive vector coupling and a negative tensor coupling constant for the K*⁺(892) trajectory, and a rotating phase factor for both trajectories. Using the χ² minimization method, one could not draw this conclusion from the same dataset.

We have performed the tree-level calculations of the eta meson photoproduction on proton for photon laboratory energies between 714 and 1500 MeV. The resonances N(1535), N(1710), N(1650), N(1440) and N(1520) were assumed. The form factors were introduced in the hadron vertices to involve the structure of hadrons. The influence of various form factor recipes was investigated. In order to keep gauge invariance, the appropriate contact term was introduced. The parameters of our model (coupling constants, cutoffs) were fitted to recent experimental data of the cross sections and some polarization observables.

We present results from a Partial-Wave Analysis (PWA) of diffractive dissociation of 190 GeV/c π^- into π^-π⁺π^- final states on nuclear targets. A PWA of the data sample taken during a COMPASS pilot run in 2004 on a Pb target showed a significant spin-exotic J^PC = 1^-+ resonance consistent with the controversial π₁(1600), which is considered to be a candidate for a non- mesonic state. In 2008 COMPASS collected a large diffractive π^-π⁺π^- data sample using a hydrogen target. A first comparison with the 2004 data shows a strong target dependence of the production strength of states with spin projections M = 0 and 1.

In October 2008, the WASA-at-COSY collected more than 10⁷ events for the pd → ³Heη reaction. The aim is the determination of the invariant mass of the lepton pairs created in the Dalitz decay η → γe⁺e^-. The e⁺e^- invariant mass spectrum is directly related to the distribution of the four-momentum squared of the virtual photon from the η → γγ* process and hence it allows for the study of the transition form factor which in turn reflects the structure of the decaying meson.

Studies of meson production in the pd → ³He X reaction, where X = η, η′ and ω, and their decays are investigated with the WASA-at-COSY facility. The angular distribution of the η in the center of mass of the ³He-η system, have been measured at an excess energy of Q = 61 MeV over the full angular range. The anisotropy expected at the relatively large Q is observed.

For the first time pp → pp³π⁰ has been measured at an incident proton momentum of P_b = 3.35GeV/c. The total cross section has been determined. The reaction mechanism is studied by a Dalitz plot analyses, which indicate that the leading production and decay mechanism is closely related to the simultaneous excitation of Δ(1232) and N*(1440) baryon resonances.

Once subtracted dispersion relations with imposed crossing symmetry condition are applied in description of the ππ D- and F-wave amplitudes. We show that these equations impose strong constraints on experimental data and model amplitudes.

In this article we present a determination of the strong coupling constant and parton distribution functions (PDFs) based on a next-to-leading order (NLO) perturbative QCD analysis of proton structure function. More precisely, we extract and PDFs by fitting perturbative QCD predictions to the data from the measurements of the proton structure function in deep inelastic scattering, which are based on perturbative QCD calculations up to NLO. We obtain at NLO in the variable-flavor number scheme.

For the very first time, the correlation femtoscopy method is applied to a kinematically complete measurement of meson production in the collisions of hadrons. The shape of the two-proton correlation function derived for the pp → ppη reaction differs from that for the pp → pp(pions) and both do not show a peak structure opposite to results determined for inclusive measurements of heavy ion collisions.

In the present contribution, we report on calculation of the Λ-hypernuclear production induced by the stopped kaon K^-. We performed the calculation within the framework of the distorted wave impulse approximation and used chirally motivated transition amplitudes for the microscopic description of the elementary kaon-nucleon process. The sensitivity of the model to several effects was tested with a special attention paid to the impact caused by variations of the initial kaon and final state pion wave functions. The calculated production rates are reported for target nuclei from Lithium to Oxygen.

Preliminary results on charged pion production in np collisions at an incident beam energy of 1.25 GeV obtained with HADES are presented. The np reactions were studied in dp collisions at 1.25 GeV/u using a Forward Wall hodoscope, aimed at registering spectator protons. The separation of np → ppπ^-, np → npπ⁺π^- and np → dπ⁺π^- channels is demonstrated.

Preliminary results on the differential cross section in dp elastic scattering has been obtained at 1.25 GeV/u with HADES within a large angular range in the center of mass system. The obtained data correspond to large transverse momenta, where a sensitivity to the 2N and 3N short range correlations is expected.

We study the meson yield ratios for high energy central nucleus-nucleus collisions by means of an effective relativistic mean-field model with the inclusion of the full octet of baryons, the Δ-isobars degrees of freedom and the lightest pseudoscalar and vector mesons. These last particles are considered in the so-called one-body contribution, taking into account of an effective chemical potential depending on the self-consistent interaction between baryons. The analysis is performed by requiring the global conservation of baryon number, electric charge fraction and zero net strangeness.

We use the Foldy-Wouthuysen representation to construct Lorentz-invariant interactions of heavy fields, building the interactions starting from non-relativistic heavy particle fields. We show that the couplings obtained feature a straightforward 1/m, where m is the mass of the heavy particle, expansion, which ensures Lorentz invariance order by order in effective field theories. We illustrate possible applications on the examples of pion-nucleon and pion-nucleon-delta couplings in chiral effective field theory. For instance, we show that one of the terms usually considered to be a part of chiral index-1 πNΔ vertex is redundant. We discuss the implications of this fact.

I calculate within two dipole models: GBW and CGC. I compare predictions with the last data from HERA. In the GBW and CGC saturation model the heavy quark contribution to F₂ was considered in the form of the pair production. I calculate inclusive charm production in terms of and diffractive charm production in terms of . I find good agreement with data both in diffractive and inclusive case. , measured by HERA, is an important issue in the determination of parton distribution functions (PDFs). Last measurement from H1⁶ shows that is consistent with D* data.

The cross sections for exclusive D⁺D^- meson pair production in nucleus - nucleus collisions are calculated and differential distributions are shown. Realistic (Fourier transform of the charge density) charge form factors of nuclei are used. Absorption effects are included. Predictions for the STAR and PHENIX collaboration measurements at RHIC are presented.

Electroproduction of a ρ⁰ vector meson in the process γ* + N → V + N^′ is measured with a 27.6 GeV longitudinally polarized electron/positron beam in the HERMES experiment. Kinematical dependences of real and imaginary parts of the ratio of the helicity amplitudes are extracted from the data.

Differential cross sections for η production in proton-proton collisions at 40 and 72 MeV above threshold show that higher partial waves are necessary to describe the reaction. A simple model assuming constant production amplitudes and including most partial waves up to two units of angular momentum reproduces the data rather well, and also describes the invariant mass distributions found at 15.5 MeV excess energy.

The experimental program on the study of deuteron-proton interaction at Internal Target at Nuclotron is discussed. Recent results on the deuteron vector and tensor analyzing powers in dp-elastic scattering obtained at intermediate energies are presented. The status of the DSS setup upgrade is reported.

The unpolarized longitudinal nucleon structure function F_L, measured in the deep inelastic lepton-nucleon scattering, is contained of three parts, singlet, non-singlet and gluon. The aim of this paper is to perform a QCD analysis of the longitudinal heavy and light structure functions F_L(x, Q²) in the non-singlet part up to . We use the light and heavy flavor Wilson coefficients and distribution functions in Mellin space. Also we need to use the Padé approximation for α_s analysis.

We present feasibility studies of a precise measurement of the |G_E| and |G_M| proton form factors that will be possible in the future with the detector.

The features of the Hyperon Induced Non Mesonic Weak Decay in double hypernuclei are shortly reviewed and a preliminary evaluation of the expected production rate in the future PANDA experiment at FAIR is reported.

Determination of α_s is one of the most important issue in high energy physics. Measurements of deep inelastic diffraction provide a chance to study this parameter besides diffractive parton distribution functions (DPDFs). Regarding the fact that LHC data is coming, it is hoped that precision measurements of diffraction in Deep Inelastic Scattering (DIS) provide a more complete understanding of strong coupling constant. We performed advanced theoretical calculations to determine Λ and DPDFs.

We report on the exclusive production of ω and η mesons in p + p reactions at 3.5 GeV beam kinetic energy. Production cross sections, angular distributions and Dalitz plots of both mesons were determined. Moreover, the relative contribution of the N(1535) resonance in η production at this energy was evaluated. We conclude that η mesons produced via N(1535) exihibit an isotropic angular distribution, whereas those produced directly show a strong anisotropic distribition. ω mesons show a slightly anisotropic angular distribition.

The measurment of the charge symmetry conserving reactions dd → ³He p π^- and dd → ³He n π⁰ is the first step of the charge symmetry breaking physics program with WASA-at-COSY. The analysis of these channels helps to understand the experimental conditions and provides additional parameters for theoretical studies. The data have been collected in November 2007.

The double-pionic fusion reactions dd → ⁴Heπ⁰π⁰ and dd → ⁴Heπ⁺π^- were measured exclusively and kinematically complete with the WASA detector at COSY. The measurements were performed in the energy range T_p = 0.8 - 1.4 GeV covering thus the full energy region, where the so-called ABC effect – a peculiar low-mass enhancement in the ππ-invariant mass spectrum – was observed previously in inclusive measurements. Our findings for the double-pionic fusion to ⁴He are in accordance with the observations for the basic pn → dπ⁰π⁰ reaction pointing to the same fundamental mechanism. In both cases we observe that the ABC effect is associated with a peak in the energy dependence of the total cross section. In the ⁴He case the peak structure in the total cross section is broadened in comparison to the deuteron case. This is consistent with both Fermi motion of the basic pn system within ⁴He and with collision broadening as it is known, e.g., from excitations of the Δ resonance in nuclei.

The π⁰π⁰ production in pp-collisions has been investigated in exclusive and kinematically complete measurements from threshold up to T_p = 1.4 GeV. For incident energies T_p > 1 GeV, i.e. in the region beyond the Roper excitation, the ΔΔ excitation process takes over. The data are well explained by the t-channel ΔΔ process dominated by pion exchange. There is no low-mass enhancement (ABC effect) in the π⁰π⁰-invariant mass distribution beyond that given by the conventional t-channel ΔΔ process. This is also true for the limiting case, where the protons are in the quasi-bound ²He state.

The analysis of new data on π^±4He interaction at T_π =106 MeV provided information on the in-medium modifications of the Δ resonance and revealed signatures of the excitation of a nuclear collective state. Evidences for a reaction channel with thermal emission of photons are also presented.

Data for quasi-free photoproduction of π⁰π⁰ and π⁰π^+/- pairs from ⁷Li have been analyzed in view of the in-medium properties of hadrons. Data have been measured with the CB/TAPS detector setup using the Glasgow photon tagging spectrometer for incident photon energies up to 820 MeV. The double π⁰ invariant mass distributions show an enhancement with respect to the mixed charged channel at small invariant masses. This enhancement could be consistent with an in-medium modification of the ππ interaction in the I = J = 0 channel, however effects from final state interactions must also be considered.

We present recent measurements of τ decays into final states with kaons, which are based on several hundred million τ⁺τ^- pairs produced in electron-positron annihilation data collected with the BABAR detector. These measurements can be used to determine the Cabibbo-Kobayashi-Maskawa matrix element |V_us| with a tiny systematic error and in two different methods affected by different systematic effects.

The decay η → π⁺π^-γ has been measured with the WASA facility at COSY. The largest data set taken so far in an exclusive measurement was acquired, with 13740±140 events after background subtraction. Efficiency corrected Dalitz plot distributions have been extracted, which show the importance of final state interactions for the understanding of the decay.

We demonstrate that the Dubna-Mainz-Taipei (DMT) meson-exchange dynamical model, which starts from an effective chiral Lagrangian, for pion photoproduction provides an excellent and economic framework to describe both the π⁰ threshold production and the Δ deformation, two features dictated by chiral dynamics.

Photoproduction of η-mesons off ³He has been studied via the η → 2γ and η → 3π⁰ decay modes at the tagged photon beam of the Mainz MAMI accelerator using the combined 4π Crystal Ball/TAPS calorimeter. The main motivation for this experiment was the search for η-mesic nuclei. A possible signature for such states is a threshold enhancement of coherent η-photoproduction similar to what has been observed in hadronic induced reactions at COSY.⁸

Rich sets of high precision cross sections, vector and tensor analyzing powers for the breakup reaction were measured at 130 and 100 MeV beam energy with the use of detection systems covering large parts of the phase space. The cross section data allowed to establish evidences for three-nucleon force contributions and to confirm predictions of sizable effect of the Coulomb force in the breakup reaction. Analyzing power data are generally quite well described by theoretical predictions even with pure nucleon-nucleon interactions. However, in some regions discrepancies has been observed for tensor analyzing powers at 130 MeV.

The deuteron-proton elastic scattering is considered at the deuteron energies from 500 up to 2000 MeV. The multiple-scattering-expansion technique is applied to evaluate the reaction amplitude. The one-nucleon-exchange, single scattering and double scattering contributions are taken into account. Also, some relativistic effects are included into consideration. The obtained results are compared with the experimental data both for the differential cross section and polarization observables.

In this talk we review the properties of mesons in nuclear matter. A unitary approach in coupled channels within the framework of the local hidden gauge formalism is used to account for the interaction of the antikaon with the nucleons and the decay channel is incorporated in matter. The in-medium interaction accounts for Pauli blocking effects and the inclusion of the self-energy in a self-consistent manner. At normal nuclear matter density, the meson feels a moderately attractive potential while the width increases enormously becoming up to five times larger than in free space. We also perform the transparency ratio for the γA → K⁺K*^-A′ reaction, which can be a feasible scenario in experimental facilities.

In this article, we report on on investigations of the in-medium meson-nucleon interaction for the ω, ɸ, and mesons. Their in-medium cross sections and collisional widths can be measured by their absorption in a nucleus. In Hall B at the Thomas Jefferson National Accelerator Facility (JLab), the CLAS detector was used to study these long-lived mesons in nuclei. All of the mesons were produced by a photon beam with E_γ < 4 GeV in targets of ²H, C, Fe, and Pb. The vector mesons were reconstructed through their decay into e⁺e^-. The mesons were measured with their dominant π⁺π^- decay. The in-medium widths of the ω and ɸ mesons are found to be substantially larger than their values from the elementary reaction with a free nucleon. The analysis with the is preliminary, and its status will be discussd in this paper.

We report recent data on e⁺e^- pair emission in proton nucleus collisions at energies slightly above the light vector meson production threshold. Invariant mass distributions for the p+Nb system at E_kin = 3.5 GeV/c² show a clear ρ/ω signal and are compared to data from elementary p+p reactions. We observe a constant π⁰/ω yield ratio for both systems.

We disuss exclusive electromagnetic production of two neutral ρ⁰ mesons and show the predictions for the AA → AAρ⁰ρ⁰ reactions for gold-gold collisions at the energy of and for lead-lead collisions at the energy of . The elementary cross section is calculated with the help of the vector-dominance-model (VDM)-Regge approach which usually very well describes the experimental data at large γγ energy. The low-energy γγ → ρ⁰ρ⁰ cross section is parametrized. The cross section for nuclear process is calculated by means of the equivalent photon approximation (EPA). We compare the results with realistic charge density with the results for monopole form factor.

Over twenty years ago QCD-inspired models of hadronic states began a rigorous search for meson outside of Naive Quark Model. Here we briefly review the current status of Exotica.

We report on a detailed investigation of four-body pp → ppπ⁺π^- and reactions which constitute an irreducible background to three-body processes pp → ppM, where M is a broad resonance in the π⁺π^- channel, e.g. M = σ, ρ⁰, f₀(980), f₂(1275), f₀(1500). We include double-diffractive contribution (both pomeron and reggeon exchanges) as well as the pion-pion rescattering contributions. The first process dominates at higher energies and small pion-pion invariant masses while the second becomes important at lower energies and higher pion-pion invariant masses. We compare our results with the experimental data. We make predictions for future experiments at PANDA, RHIC, Tevatron and LHC energies. The two-dimensional distribution in rapidity space of pions (y_π⁺, y_π^-) is particularly interesting. The higher the incident energy, the higher preference for the same-hemisphere emission of pions. The processes considered constitute a sizeable contribution to the total nucleon-nucleon cross section as well as to pion inclusive cross section.

This paper presents an analysis of π^- Pb → X^- Pb → π^-π^-π⁺ Pb events at 190 GeV/c beam momentum and low four-momentum transfer t′ < 0.01 (GeV/c)². Coherent scattering off the lead nucleus as a whole dominates with contributions from Reggeon, Pomeron and photon exchange. Photoproduction becomes apparent at lowest t′ and can be extracted statistically as well as by a partial-wave analysis, indicating also the overlap of diffractive and photo-production of the 3π events.

This paper presents one of the physics goals of the NA61/SHINE experiment: measurements of hadron production needed for neutrino (T2K) and cosmic-ray (Pierre Auger and KASKADE) experiments. Preliminary results from the proton-Carbon interactions at 31 GeV/c for the T2K experiment at J-PARC are presented. Knowledge of pion and kaon production is important for improving the accuracy of neutrino flux simulations. Three different methods of the pion spectra extractions are presented. Finally, preliminary differential cross section dsigma/dp in several intervals of emission angles of charged pion in p+C interactions at 31 GeV/c.

For making polarized antiproton beams the so called filter method is normally discussed. It is based on the depletion of one spin component due to the spin dependent interaction if a stored beam passes a polarized target. The method has been proven by the FILTEX collaboration and detailed studies are presently performed by the PAX collaboration.

Another source for polarized antiprotons is the antilambda decay as it was used in the only experiment with polarized antiprotons so far at FERMILAB.

Furthermore the antiproton production process itself if showing polarisation, would be by far the best way to get polarized . It can be assumed to result from a quasi-free proton-nucleon collison. Up to now it has never been investigated in detail. In such a hadronic interaction the antiprotons may have substantial polarisation which would simplify the preparation of a polarized antiproton beam drastically.

It is proposed to measure the polarisation of antiprotons produced in a fixed target experiment.

A precise description of the high excited meson spectra is obtained from the solution of the spinless Salpeter equation for a static radial potential. The coulombic asymptotic behavior of such potential suggests that the meson spectra are limited so that no single states may exist beyond a limiting mass.

The hard exclusive electro-production of ɸ and ω vector mesons was studied with the HERMES spectrometer at the DESY laboratory by scattering 27.6 GeV positron and electron beams off a transversely polarized hydrogen target. The single-spin azimuthal asymmetry with respect to the transverse proton polarization was measured.

The COMPASS experiment at CERN is well designed for light-hadron spectroscopy with emphasis on the detection of new states, in particular the search for J^PC-exotic states and glueballs. We have collected data with 190 GeV/c charged hadron beams on a liquid hydrogen and nuclear targets in 2008/09. The spectrometer features good coverage by electromagnetic calorimetry and a RICH detector further provides π K separation, allowing for studying final states involving neutral particles like π⁰ or η as well as hidden strangeness, respectively. We discuss the status of ongoing analyses with specific focus on diffractively produced (π⁰π⁰π)^- as well as final states.