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This work measured ds/dO for neutral kaon photoproduction reactions from threshold up to a c.m. energy of 1855MeV, focussing specifically on the.p. K0S+, .n. K0., and.n. K 0 S 0 reactions. Our results for.n. K0S0 are the first-ever measurements for that reaction. These data will provide insight into the properties of N * resonances and, in particular, will lead to an improved knowledge about those states that couple only weakly to the pN channel. Integrated cross sections were extracted by fitting the differential cross sections for each reaction as a series of Legendre polynomials and our results are compared with prior experimental results and theoretical predictions.

The gamma n -> pi(0)n differential cross section evaluated for 27 energy bins span the photon-energy range 290-813 MeV (W = 1.195- 1.553 GeV) and the pion c.m. polar production angles, ranging from 18 degrees to 162 degrees, making use of model-dependent nuclear corrections to extract pi(0) production data on the neutron from measurements on the deuteron target. Additionally, the total photoabsorption cross section was measured. The tagged photon beam produced by the 883 MeV electron beam of the Mainz Microtron MAMI was used for the pi(0)-meson production. Our accumulation of 3.6 x 10(6) gamma n -> pi(0)n events allowed a detailed study of the reaction dynamics. Our data are in reasonable agreement with previous A2 measurements and extend them to lower energies. The data are compared with predictions of previous SAID, MAID, and BnGa partial-wave analyses and to the latest SAID fit MA19 that included our data. Selected photon-decay amplitudes N* -> gamma n at the resonance poles are determined for the first time.

The data available from the A2 Collaboration at MAMI were analyzed to select the gamma p -> pi(0) eta p reaction on an event-by-event basis, which allows for partial-wave analyses of three-body final states to obtain more reliable results, compared to fits to measured distributions. These data provide the world's best statistical accuracy in the energy range from threshold to E-gamma = 1.45 GeV, allowing a finer energy binning in the measurement of all observables needed for understanding the reaction dynamics. The results obtained for themeasured observables are compared to existing models, and the impact from the new data is checked by the fit with the revised Mainz model.

The Dalitz decays eta -> e(+)e(-)gamma and omega -> pi(0)e(+)e(-) have been measured in the gamma p -> eta p and gamma p -> omega p reactions, respectively, with the A2 tagged-photon facility at the Mainz Microtron. The value obtained for the slope parameter of the electromagnetic transition form factor of eta, Lambda(-2)(eta) = (1.97 +/- 0.11(tot)) GeV-2, is in good agreement with previous measurements of the eta -> e(+)e(-)gamma and eta ->mu(+)mu(-)gamma decays. The uncertainty obtained in the value of Lambda(-2)(eta) is lower than in previous results based on the eta -> e(+)e(-)gamma decay. The value obtained for the omega slope parameter Lambda(0-2)(omega pi) = (1.99 +/- 0.21(tot)) GeV-2, is somewhat lower than previous measurements based on omega -> pi(0)mu(+)mu(-), but the results for the omega transition form factor are in better agreement with theoretical calculations, compared to earlier experiments.

The reactions γp→ηp and γp→η′p are measured from their thresholds up to the center-of-mass energy W=1.96 GeV with the tagged-photon facilities at the Mainz Microtron, MAMI. Differential cross sections are obtained with unprecedented statistical accuracy, providing fine energy binning and full production-angle coverage. A strong cusp is observed in the total cross section for η photoproduction at the energies in the vicinity of the η′ threshold, W=1896 MeV (Eγ=1447 MeV). Within the framework of a revised ηMAID isobar model, the cusp, in connection with a steep rise of the η′ total cross section from its threshold, can only be explained by a strong coupling of the poorly known N(1895)1/2− state to both ηp and η′p. Including the new high-accuracy results in the ηMAID fit to available η and η′ photoproduction data allows the determination of the N(1895)1/2− properties.

Precise helicity-dependent cross sections and the double-polarization observable E were measured for η photoproduction from quasifree protons and neutrons bound in the deuteron. The η→2γ and η→3π0→6γ decay modes were used to optimize the statistical quality of the data and to estimate systematic uncertainties. The measurement used the A2 detector setup at the tagged photon beam of the electron accelerator MAMI in Mainz. A longitudinally polarized deuterated butanol target was used in combination with a circularly polarized photon beam from bremsstrahlung of a longitudinally polarized electron beam. The reaction products were detected with the electromagnetic calorimeters Crystal Ball and TAPS, which covered 98% of the full solid angle. The results show that the narrow structure observed earlier in the unpolarized excitation function of η photoproduction off the neutron appears only in reactions with antiparallel photon and nucleon spin (σ1/2). It is absent for reactions with parallel spin orientation (σ3/2) and thus very probably related to partial waves with total spin 1/2. The behavior of the angular distributions of the helicity-dependent cross sections was analyzed by fitting them withLegendre polynomials. The results are in good agreement with a model from the Bonn-Gatchina group, which uses an interference of P11 and S11 partial waves to explain the narrow structure.

High-statistics measurements of the photon asymmetry S for the (gamma) over right arrowp -> pi(0)p reaction have been made in the center-of-mass energy range W = 1214-1450MeV. The data were measured with the MAMI A2 real photon beam and Crystal Ball/TAPS detector systems in Mainz, Germany. The results significantly improve the existing world data and are shown to be in good agreement with previous measurements, and with the MAID, SAID, and Bonn-Gatchina predictions. We have also combined the photon asymmetry results with recent cross-section measurements from Mainz to calculate the profile functions, Sigma (= sigma(0)Sigma), and perform a moment analysis. Comparison with calculations from the Bonn-Gatchina model shows that the precision of the data is good enough to further constrain the higher partial waves, and there is an indication of interference between the very small F-waves and the N(1520) 3/2(-) and N(1535)1/2(-) resonances.

The double polarization observable E and the helicity dependent cross sections σ1=2 and σ3=2 were measured for η photoproduction from quasifree protons and neutrons. The circularly polarized tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost 4π detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from η → 2γ and η → 3π0. The results show that the narrow structure previously observed in η photoproduction from the neutron is only apparent in σ1=2 and hence, most likely related to a spin-1=2 amplitude. Nucleon resonances that contribute to this partial wave in η production are only N1=2− (S11) and N 1=2þ (P11). Furthermore, the extracted Legendre coefficients of the angular distributions for σ1=2 are in good agreement with recent reaction model predictions assuming a narrow resonance in the P11 wave as the origin of this structure.

Polarisation-dependent differential cross sections σTσT associated with the target asymmetry T have been measured for the reaction View the MathML sourceγp→→pπ0 with transverse target polarisation from π0π0 threshold to photon energies of 190 MeV. The data were obtained using a frozen-spin butanol target with the Crystal Ball / TAPS detector set-up and the Glasgow photon tagging system at the Mainz Microtron MAMI. Results for σTσT have been used in combination with our previous measurements of the unpolarised cross section σ0σ0 and the beam asymmetry Σ for a model-independent determination of S- and P -wave multipoles in the π0π0 threshold region, which includes for the first time a direct determination of the imaginary part of the E0+E0+ multipole.

Measurements of gamma p -> K+ Lambda and gamma p -> K+ Sigma(0) cross-sections have been obtained with the photon tagging facility and the Crystal Ball calorimeter at MAMI-C. The measurement uses a novel K+ meson identification technique in which the weak decay products are characterized using the energy and timing characteristics of the energy deposit in the calorimeter, a method that has the potential to be applied at many other facilities. The fine center-of-mass energy (W) resolution and statistical accuracy of the new data results in a significant impact on partial wave analyses aiming to better establish the excitation spectrum of the nucleon. The new analyses disfavor a strong role for quark-diquark dynamics in the nucleon.

Measurements of γp→K+Λγp→K+Λ and γp→K+Σ0γp→K+Σ0 cross-sections have been obtained with the photon tagging facility and the Crystal Ball calorimeter at MAMI-C. The measurement uses a novel K+K+ meson identification technique in which the weak decay products are characterized using the energy and timing characteristics of the energy deposit in the calorimeter, a method that has the potential to be applied at many other facilities. The fine center-of-mass energy (W) resolution and statistical accuracy of the new data results in a significant impact on partial wave analyses aiming to better establish the excitation spectrum of the nucleon. The new analyses disfavor a strong role for quark–diquark dynamics in the nucleon.

Information on the size and shape of the neutron skin on 208Pb is extracted from coherent pion photoproduction cross sections measured using the Crystal Ball detector together with the Glasgow tagger at the MAMI electron beam facility. On exploitation of an interpolated fit of a theoretical model to the measured cross sections the half-height radius and diffuseness of the neutron distribution are found to be cn=6.70±0.03(stat.)fm and an=0.55±0.01(stat.)+0.02−0.03(sys.)fm respectively, corresponding to a neutron skin thickness ∆r(np)=0.15±0.03(stat.)+0.01−0.03(sys.)fm. The results give the first successful extraction of a neutron skin thickness with an electromagnetic probe and indicate that the skin of 208Pb has a halo character. The measurement provides valuable new constraints on both the structure of nuclei and the equation of state for neutron rich matter.

Precise angular distributions have been measured for the first time for the photoproduction of π0-mesons off neutrons bound in the deuteron. The effects from nuclear Fermi motion have been eliminated by a complete kinematic reconstruction of the final state. The influence of final-state- interaction effects has been estimated by a comparison of the reaction cross section for quasi-free protons bound in the deuteron to the results for free protons and then applied as a correction to the quasi-free neutron data. The experiment was performed a t the tagged photon facility of the Mainz Microtron MAMI with the Crystal Ball and TAPS detector setup for incident photon energies between 0.45 GeV and 1.4 GeV. The results are compared to the predictions from react ion models and partial-wave analyses based on data from other isospin channels. The model predictions show large discrepancies among each other and the present data will provide much tighter constraints. This is demonstrated by the results of a new analysis in the framework of the Bonn-Gatchina coupled-channel analysis which included the present data.

We report the first large-acceptance measurement of polarization transfer from a polarized photon beam to a recoiling nucleon, pioneering a novel polarimetry technique with wide application to future nuclear and hadronic physics experiments. The commissioning measurement of polarization transfer in the 1H(~γ, ~p)π0 reaction in the range 0.4< Eγ < 1.4 GeV is highly selective regarding the basic parametrization used in partial wave analyses to extract the nucleon excitation spectrum. The new data strongly favor the recently proposed Chew-Mandelstam formalism.

The γp→K0 Σ+ reaction has been measured from threshold to Eγ=1.45 GeV (WCM = 1.9 GeV) using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. In the present experiment, this reaction was searched for in the 3π0p final state. The experimental results include total and differential cross sections as well as the polarization of the recoil hyperon. The new data significantly improve the empirical knowledge about the γp → K0 Σ+ reaction in the measured energy range. The results are compared to previous measurements and model predictions.

The first measurement of the helicity dependence of the total inclusive ^3He photo-absorption cross section and of the partial cross sections for several reaction channels was carried out at MAMI (Mainz) in the photon energy range between 150 and 500 MeV. The experiment used the large acceptance Crystal Ball spectrometer, complemented by charged particle and vertex detectors, a circularly polarised tagged photon beam and a longitudinally polarised high-pressure 3He gas target. The results obtained give information on the GDH integral on 3He and on the neutron and allow an investigation of the modifications of nucleon properties inside 3He.

The 12C (γ⃗ , pp) reaction has been studied in the photon energy range 200-450 MeV at the Mainz microtron MAMI-C, where linearly polarised photons were energy-tagged using the Glasgow-Mainz Tagged Photon Spectrometer and protons were detected in the Crystal Ball detector. The photon asymmetry Σ has been measured over a wider Eγ range than previous measurements. The strongest asymmetries were found at low missing energies where direct emission of nucleon pairs is expected. Cuts on the difference in azimuthal angles of the two ejected protons increased the magnitude of the observed asymmetries. At low missing energies the Σ data exhibit a strong angular dependence, similar to deuteron photodisintegration.

Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of neutral pion pairs in the reactions ~γp→pπ0 π0 and ~γd→(n)pπ0π0, ~γd → (p)nπ0π0 off free protons and off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow magnetic spectrometer. Decay photons from the π0 mesons, recoil protons, and recoil neutrons were detected in the 4π covering electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. After kinematic reconstruction of the final state, excellent agreement was found between the results for free and quasi-free protons. This demonstrates that the free-nucleon behavior of such observables can be extracted from measurements with quasi-free nucleons, which is the only possibility for the neutron. Contrary to expectations, the measured asymmetries are very similar for reactions off protons and neutrons. The results are compared to the predictions from the Two-Pion-MAID reaction model and (for the proton)also to the Bonn-Gatchina coupled channel analysis

The Dalitz decay η→γe+e− has been measured using the combined Crystal Ball and TAPS photon detector setup at the electron accelerator MAMI-C. Compared to the most recent transition form-factor measurement in the e+e− channel, statistics have been improved by one order of magnitude. The e+e− invariant mass distribution shows a deviation from the QED prediction for a point-like particle, which can be described by a form-factor. Using the usual monopole transition form-factor parameterization, F(m^2)=(1−m^2/Λ^2)^−1, a value of Λ^−2=(1.92±0.35(stat)±0.13(syst)) GeV^−2 has been determined. This value is in good agreement with a recent measurement of the η Dalitz decay in the μ+μ− channel and with recent form-factor calculations. An improved value of the branching ratio BR(η→γe+e−)=(6.6±0.4(stat)±0.4(syst))•10^−3 has been determined.

Differential cross sections for K- radiative capture in flight on the proton, leading to the γΛ and γΣ0 final states, have been measured at eight K- momenta between 514 and 750 MeV/c. The data were obtained with the Crystal Ball multiphoton spectrometer installed at the separated K/π beam line C6 of the BNL Alternating Gradient Synchrotron. The results substantially improve the existing experimental data available for studying radiative decays of excited hyperon states. An exploratory theoretical analysis is performed within the Regge-plus-resonance approach. According to this analysis, the γΣ0 final state is dominated by hyperon-resonance exchange and hints at an important role for a resonance in the mass region of 1700 MeV. In the γΛ final state, in contrast, the resonant contributions account for only half the strength, and the data suggest the importance of a resonance in the mass region of 1550 MeV.

The circular photon asymmetry for π0η photoproduction on the proton was measured for the first time at the tagged photon facility of the MAMI C accelerator using the Crystal Ball/TAPS photon spectrometer. The experimental results are interpreted within a phenomenological isobar model that confirms the dominant role of the Δ(1700)D33 resonance. The measured asymmetry allows us to identify small contributions from positive-parity resonances via interference terms with the dominant D33 amplitude.

The γp → ηp reaction has been measured with the Crystal Ball and TAPS multiphoton spectrometers in the energy range from the production threshold of 707 MeV to 1.4 GeV (1.49

We report the first measurements of the total cross section of the reaction K-p-->Sigma 0 gamma at eight beam momenta from 514 to 750 MeV/c. The data were obtained at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory using the Crystal Ball detector consisting of 672 NaI crystals. All charged particles were vetoed by a barrel of plastic scintillators, resulting in a study of only the neutral decays of the Sigma 0. The prompt photon and the photons from the decay products of Sigma 0 were detected for each reconstructed event ; the neutron was also detected in a small fraction of the events.

The dynamics of the eta→ 3pi^0 decay have been studied with the Crystal Ball multiphoton spectrometer and the TAPS calorimeter. Bremsstrahlung photons produced by the 1.5-GeV electron beam of the Mainz microtron MAMI-C and tagged by the Glasgow photon spectrometer were used for eta-meson production. The analysis of 3×10^6 gamma p→ eta p→ 3 pi^0 p→ 6 gama p events yields the value alpha = -0.032 +/- 0.003 for the eta→ 3pi^0 slope parameter, which agrees with the majority of recent experimental results and has the smallest uncertainty. The pi^0pi^0 invariant-mass spectrum was investigated for the occurrence of a cusplike structure in the vicinity of the pi^+pi^-threshold. The observed effect is small and does not affect our measured value for the slope parameter.

The results on the differential cross sections as well as the polarizations of Lambda and Sigma0 have been obtained for {;K};0 n, pi0 Lambda, and pi0 Sigma0 production in K^- p interactions at eight K^- momenta between 514 and 750 MeV/c. The study is conducted by measuring multiphoton final states with the Crystal Ball spectrometer, using a K^- beam from the Alternating Gradient Synchrotron of BNL. The results improve substantially the existing data, allowing a detailed reexamination of the Lambda^* and Sigma^* states in our energy range.

We have measured the π+→e+νγ branching ratio over a wide region of phase space, based on a total of 65 460 events acquired using the PIBETA detector. Minimum-χ2 fits to the measured (Ee+, Eγ) energy distributions result in the weak form factor value of FA=0.0119(1) with a fixed value of FV=0.0259. An unconstrained fit yields FV=0.0258(17) and FA=0.0117(17). In addition, we have measured a=0.10(6) for the dependence of FV on q2, the e+ν pair invariant mass squared, parametrized as FV(q2)=FV(0)(1+aq2). The branching ratio for the kinematic region Eγ>10 MeV and θe+γ>40° is measured to be Bexpt=73.86(54)×10-8. Earlier deviations we reported in the high-Eγ–low-Ee+ kinematic region are resolved without a tensor term. We also derive new values for the pion polarizability αE=2.78(10)×10-4 fm3 and neutral pion lifetime τπ0=(8.5±1.1)×10-17 s.

Total and differential cross sections for the reaction gamma p -> pi^0 eta p have been measured with the Crystal Ball/TAPS detector using the tagged photon facility at the MAMI C accelerator in Mainz. In the energy range E_gamma=0.95-1.4 GeV the reaction is dominated by the excitation and sequential decay of the Delta(1700)D_33 resonance. Angular distributions measured with high statistics allow us to determine the ratio of hadronic decay widths Gamma_(eta Delta)/Gamma_(pi S11) and the ratio of the helicity amplitudes A_(3/2)/A_(1/2) for this resonance.

Tri raspršenja su eksperimentalno dostupna u sustavu piona i nukleona: dva elastična raspršenja te reakcija izmjene naboja. Da bi se precizno opisao sustav piona i nukleona potrebni su kvalitetni eksperimentalni podaci za sva tri raspršenja i to u svim područjima energija od interesa. Reakcija izmjene naboja na niskim energijama (ispod 100 MeV kinetičke energije pionskog snopa) ne zadovoljava taj uvjet: prethodnih mjerenja nema puno, a dio ih je i upitne kvalitete. S druge strane upravo je područje niskih energija vrlo zanimljivo jer su tu najizraženiji efekti narušenja izospinske simetrije. Drugi razlog je taj što su mjerenja na niskim energijama presudna za određivanje vrlo važne veličine: pionskonukleonskog sigma člana. Prikazani su diferencijalni udarni presjeci za reakciju pionsko-nukleonske izmjene naboja za sva područja kutova pri sedam različitih energija pionskog snopa u rasponu od 34 MeV do 87 MeV. Mjerenja su napravljena s Crystal Ball detektorom na Nacionalnom laboratoriju Brookhaven u Sjedinjenim Američkim Državama. Reakcija izmjene naboja prepoznata je mjerenjem energija i smjerova dvaju fotona nastalih iz raspada neutralnog piona. Statistički značaj prikazanih rezultata usporediv je sa svim prethodnim eksperimentima ispod 100 MeV zajedno. Rezultati su uspoređeni s predviđanjima analize parcijalnih valova sa Sveučilišta George Washington zasnovane na prethodnim mjerenjima. Statistički značajna odstupanja su uočena za sve energije osim najviše.

The PEN Collaboration is conducting a new measurement of the pi+ -> e+ nu branching ratio at the Paul Scherrer Institute, with the goal uncertainty of delta B/B(pie2)=5E-4 or lower. At present, the combined accuracy of all published pie2 decay measurements lags behind the theoretical calculation by a factor of 40. In this contribution we report on the PEN detector configuration and its performance during two development runs done in 2007 and 2008., Comment: pdflatex, 11 pages, 5 figures, to be published in "Progress in High-Energy Physics and Nuclear Safety", NATO Science for Peace Series: B - Physics and Biophysics

The reaction K-p00 neutrals was studied with the Crystal Ball detector at the BNL Alternating Gradient Synchrotron for beam momenta between 514 and 750 MeV/c. The photons from 0 and 0 decays were detected, as well as the neutron in a small fraction of the events. The differential cross section and the 0 polarization are reported at eight momenta and nearly the full angular range. Total cross sections are derived from Legendre polynomial fits to the data. The measurements presented are of considerably higher precision than previous results.

Knjiga posvećena Ivanu Supeku izlaže nastanak i djelovanje svjetskog pagvaškog pokreta za nuklearno razoružanje te djelovanje hrvatskih znanstvenika u tom pokretu, kao i u Hrvatskoj pagvaškoj grupi. Posebna je pažnja posvećena djelovanju Hrvatske pagvaške grupe i Ivana Supeka u razdoblju prije raspada Jugoslavije i u toku domovinskog rata, kada su članovi Hrvatske pagvaške grupe koristili svoje članstvo u mejunarodnom Pugwash-u da bi upoznavali znanstvenu i širu javnost o zbivanjima u našem području.

We have measured the + ! e+ branching ratio over a wide region of phase space, based on a total of 65, 460 events acquired using the PIBETA detector. Minimum- 2 ts to the measured (Ee+ ; E) energy distributions result in the weak form factor value of FA = 0:0119(1) with a xed value of FV = 0:0259. An unconstrained t yields FV = 0:0258(17) and FA = 0:0117(17). In addition, we have measured a = 0:095 0:058 for the dependence of FV on the e+ pair invariant mass q2, parametrized as FV (q2) = FV (0)(1 + a q2). The branching ratio for the kinematic region E > 10MeV and e+ > 40 is measured to be Bexp = 73:86(54) 10

New results on the rare, doubly radiative decay eta -->pi0 gama gamma have been obtained from a revised analysis of the Crystal Ball experiment performed at the AGS. The analysis yields the first information on the dependence of the decay width, Gamma (eta-->pi0 gamma gamma), on the two-photon invariant mass squared, m2(gamma gamma). A re-evaluation of the branching ratio is also made, BR(eta-->pi0 gamma gamma= (2.21± 0.24stat± 0.47syst)×10-4 ; it implies that the decay width is Gamma(eta-->pi0 gamma gamma) =0.285± 0.031stat± 0.061syst eV. These results are close to predictions based on chiral perturbation theory with vector-meson dominance.

Posrijedi je svojevrsna povijest znanosti viđena iz obzora čovjekova traganja za istinom.

Riječ je o zapisnicima u Haagu.

We report a new measurement of the differential cross section for pi^-p-->pi^0 n from p_pi=649 to 752 MeV/c, which is around the opening of the eta channel (685 MeV/c). Our data support the main features of the pi^-p charge-exchange differential cross sections generated by the SAID piN partial-wave analysis. The opening of the eta channel has a clear effect on the shape of the excitation function for dsigma (pi^-p-->pi^0 n), which is most noticeable in the backward direction.

The differential cross section for eta production in reaction pi-p-->eta n has been measured over the full angular range at seven incident - beam momenta from threshold to p_pi-=747 MeV/c using the Crystal Ball multiphoton spectrometer. The angular distributions are S wave dominated. At 10 MeV/c above threshold, a small D-wave contribution appears that interferes with the main S wave. The total eta production cross section sigma^tot is obtained by integration of d sigma/d omega. Starting at threshold, sigma^tot rises rapidly, as expected for S-wave-dominated production. The features of the pi-p-->eta n cross section are strikingly similar to those of the SU(3) flavor-related process K-p-->eta Lambda. Comparison of the pi-p-->eta n reaction is made with eta photoproduction.

The branching ratio (BR) for the rare decay eta-->pi^0 gamma gamma was measured with the Crystal Ball multiphoton spectrometer. The result, BR(eta-->pi^0 gamma gamma)=(3.5&plusmn ; ; 0.7_stat&plusmn ; ; 0.6_syst)×10-4, is in agreement with calculations of chiral perturbation theory to third order. We have used a sample of 28 million eta mesons produced at the BNL Alternating Gradient Synchrotron using the pi-p-->eta n reaction close to threshold. We detail the intricate extraction of the signal, which has about 1.6 thousand eta-->pi^0 gamma gamma events, from the overwhelming background of eta -->3pi^0 decays and from the pi-p-->pi^0 pi^0 n reaction.

U knjizi se razmatra uloga Ruđera Boškovića u povijesti fizike, filozofije i znanosti uopće, kao i niz njegovih ideja koje su plodno utjecale na razvoj suvremene fizike, posebice kvantne teorije.

U knjizi se razmatra odnos znanosti i politike, te uloga koju bi trebala imati znanost u suvremenome društvu.

A new upper limit is presented for the branching ratio (BR) of eta -->3 gamma. This decay is not allowed by charge-conjugation invariance. We have determined that BR(eta -->3gamma)Pi^0 gamma-->3gamma)pi^0pi^0 gamma gamma)eta n reaction close to threshold.

We have used the PIBETA large-acceptance detector for a precise measurement of the pi+->e+nigama radiative decay at rest, with a broad phase space coverage. Using the CVC value for the pion vector form factor, F_V=0.0259(5), we have obtained a new value of the pion axial-vector form factor gamma=F_A/F_V=0.429(14). However, significant deviations from the SM predictions are evident in our data. The discrepancy can be accounted for by introducing a pion tensor form factor of F_T=-0.0016(3). The question of the true nature of the observed deviations remains open pending further theoretical and experimental study.

Measured values of the differential cross section for pion-nucleon charge exchange, pi^– -->p pi^0n, are presented at pi^- momenta of 148, 174, 188, 212, 238, 271, 298, and 323 MeV/c, a region dominated by the Lambda (1232) resonance. Complete angular distributions were obtained using the Crystal Ball detector at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL). Statistical uncertainties of the differential cross sections are typically 2 to 6%, exceptions being the results at the lowest momentum and at the most forward measurements at the five lowest momenta. We estimate the systematic uncertainties to be 3 to 6%.

Reaction pi^- p pi^0pi^0n has been measured with high statistics in the beam momentum range 270 - 750 MeV/c. The data were obtained using the Crystal Ball multiphoton spectrometer, which has 93% of 4pi solid angle coverage. The dynamics of the pi^- p pi^0pi^0n reaction and the dependence on the beam energy are displayed in total cross sections, Dalitz plots, invariant-mass spectra, and production angular distributions. Special attention is paid to the evaluation of the acceptance that is needed for the precision determination of the total cross section sigma_t(pi^- p pi^0pi^0n). The energy dependence of sigma_t(pi- p pi^0pi^0n) shows a shoulder at the Roper resonance [i.e., the N(1440)1/2^+], and there is also a maximum near the N(1520)3/2-. It illustrates the importance of these two resonances to the pi^0pi^0 production process. The Dalitz plots are highly nonuniform ; they indicate that the pi^0pi^0n final state is dominantly produced via the pi^0Delta^0(1232) intermediate state. The invariant-mass spectra differ much from the phase-space distributions. The production angular distributions are also different from the isotropic distribution, and their structure depends on the beam energy. For beam momenta above 550 MeV/c, the density distribution in the Dalitz plots strongly depends on the angle of the outgoing dipion system (or equivalently on the neutron angle). The role of the f_0(600) meson (also known as the sigma) in pi^0pi^0n production remains controversial.