The results of a study of the annihilation reactions n p → θπ + and n p → ωπ + are reported; the data were collected by the OBELIX apparatus, with antineutrons annihilating in flight (momenta from ∼ 50 MeV/ c to 405 MeV/ c ). Annihilation frequencies and annihilation cross sections have been deduced, for both channels, as a function of antineutron momentum. From the cross section ratio, a substantial deviation from OZI rule expectations is observed. An s s quark content in the nucleon offers a fairly plausible explanation for such an effect.

We present cross sections for e+e−→hadrons, e+e−, and μ+μ− near 3095 MeV. The ψ(3095) resonance is established as having an assignment JPC=1−−. The mass is 3095 ±4 MeV. The partial width to electrons is Γe=4.8±0.6 keV and the total width Γ=69±15 keV. Total rates and interference measurements for the lepton channels are in accord with μ−e universality.

Using a data sample collected with the CLEO II detector at CESR, we have searched for dipion transitions between pairs of $\Upsilon$ resonances at energies near the $\Upsilon(4S)$. We obtain upper limits $B(\Upsilon(4S)\to \Upsilon(2S)\pi^+\pi^-) < 3.9 \times 10^{-4}$ and $B(\Upsilon(4S)\to \Upsilon(1S)\pi^+\pi^-) < 1.2 \times 10^{-4}$. We also observe the transitions $\Upsilon(3S)\to \Upsilon(1S)$, $\Upsilon(3S)\to \Upsilon(2S)$, and $\Upsilon(2S)\to \Upsilon(1S)$, from which we measure the cross-sections for the radiative processes $e^+e^- \to \Upsilon(3S)\gamma$ and $e^+e^- \to \Upsilon(2S)\gamma$.

A study of the reaction π − p → X − p based on 1.27 × 10 6 events, corresponding to a mean sensitivity of 200 events/μb, is presented. Properties of the exclusive channels π − p → π − π 0 p, π + π − π − p, π + π − π − π 0 p, π + π + π − π − π − p and π + π + π − π − π − π 0 p are discussed.

The process e+e- --> pi+ pi- pi0 gamma has been studied at a center-of-mass energy near the Y(4S) resonance using a 89.3 fb-1 data sample collected with the BaBar detector at the PEP-II collider. From the measured 3pi mass spectrum we have obtained the products of branching fractions for the omega and phi mesons, B(omega --> e+e-)B(omega --> 3pi)=(6.70 +/- 0.06 +/- 0.27)10-5 and B(phi --> e+e-)B(phi --> 3pi)=(4.30 +/- 0.08 +/- 0.21)10-5, and evaluated the e+e- --> pi+ pi- pi0 cross section for the e+e- center-of-mass energy range 1.05 to 3.00 GeV. About 900 e+e- --> J/psi gamma --> pi+ pi- pi0 gamma events have been selected and the branching fraction B(J/psi --> pi+ pi- pi0)=(2.18 +/- 0.19)% has been measured.

We have observed a second sharp peak in the cross section for e+e−→hadrons at a center-of-mass energy of 3.695±0.004 GeV. The upper limit of the full width at half-maximum is 2.7 MeV.

We report the result of a brief experiment to measure the cross section for photoproduction of Jψ(3100). At a mean energy of 55 GeV we find this cross section per nucleon to be 37.5 ± 8.2 (statistical) ± 4 (systematic) nb. The result establishes the previously indicated rise in Jψ photoproduction on protons above 20 GeV and suggests that the rise has occurred by 55 GeV.

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We report measurement of the cross section of $e^+e^-\to \pi^+\pi^-\psi(2S)$ between 4.0 and $5.5 {\rm GeV}$, based on an analysis of initial state radiation events in a $980 \rm fb^{-1}$ data sample recorded with the Belle detector. The properties of the $Y(4360)$ and $Y(4660)$ states are determined. Fitting the mass spectrum of $\pi^+\pi^-\psi(2S)$ with two coherent Breit-Wigner functions, we find two solutions with identical mass and width but different couplings to electron-positron pairs: $M_{Y(4360)} = (4347\pm 6\pm 3) {\rm MeV}/c^2$, $\Gamma_{Y(4360)} = (103\pm 9\pm 5) {\rm MeV}$, $M_{Y(4660)} = (4652\pm10\pm 8) {\rm MeV}/c^2$, $\Gamma_{Y(4660)} = (68\pm 11\pm 1) \rm MeV$; and ${\cal{B}}[Y(4360)\to \pi^+\pi^-\psi(2S)]\cdot \Gamma_{Y(4360)}^{e^+e^-} = (10.9\pm 0.6\pm 0.7) \rm eV$ and ${\cal{B}}[Y(4660)\to \pi^+\pi^-\psi(2S)]\cdot \Gamma_{Y(4660)}^{e^+e^-} = (8.1\pm 1.1\pm 0.5) \rm eV$ for one solution; or ${\cal{B}}[Y(4360)\to \pi^+\pi^-\psi(2S)]\cdot \Gamma_{Y(4360)}^{e^+e^-} = (9.2\pm 0.6\pm 0.6) \rm eV$ and ${\cal{B}}[Y(4660)\to \pi^+\pi^-\psi(2S)]\cdot \Gamma_{Y(4660)}^{e^+e^-} = (2.0\pm 0.3\pm 0.2) \rm eV$ for the other. Here, the first errors are statistical and the second systematic. Evidence for a charged charmoniumlike structure at $4.05 {\rm GeV}/c^2$ is observed in the $\pi^{\pm}\psi(2S)$ intermediate state in the $Y(4360)$ decays.

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The cross section of the process $e^+e^-\to \pi^+\pi^-\pi^0$ was measured in the Spherical Neutral Detector (SND) experiment at the VEPP-2M collider in the energy region $\sqrt[]{s}$ below 980 MeV. This measurement was based on about $1.2 \times 10^6$ selected events. The obtained cross section was analyzed together with the SND and DM2 data in the energy region $\sqrt[]{s}$ up to 2 GeV. The $\omega$-meson parameters: $m_\omega=782.79\pm 0.08\pm 0.09$ MeV, $\Gamma_\omega=8.68\pm 0.04\pm 0.15$ MeV and $\sigma(\omega\to 3\pi)=1615\pm 9\pm 57$ nb were obtained. It was found that the experimental data cannot be described by a sum of only $\omega$, $\phi$, $\omega^\prime$ and $\omega^{\prime\prime}$ resonances contributions. This can be interpreted as a manifestation of $\rho\to 3\pi$ decay, suppressed by $G$-parity, with relative probability $B(\rho\to 3\pi) = (1.01\pm^{0.54}_{0.36}\pm 0.034) \times 10^{-4}$.

Using data collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider, we measure the energy dependence of the $e^+e^- \to h_b(nP)\pi^+\pi^-$ $(n=1,2)$ cross sections from thresholds up to $11.02\,$GeV. We find clear $\Upsilon(10860)$ and $\Upsilon(11020)$ peaks with little or no continuum contribution. We study the resonant substructure of the $\Upsilon(11020) \to h_b(nP)\pi^+\pi^-$ transitions and find evidence that they proceed entirely via the intermediate isovector states $Z_b(10610)$ and $Z_b(10650)$. The relative fraction of these states is loosely constrained by the current data: the hypothesis that only $Z_b(10610)$ is produced is excluded at the level of 3.3 standard deviations, while the hypothesis that only $Z_b(10650)$ is produced is not excluded at a significant level.

The differential cross section for the reaction e + e − → γγ has been measured in the CMS energy range between 9.4 and 31.6 GeV. The results are found to be in agreement with the predictions of quantum electrodynamics up to momentum transfers- q 2 of 900 GeV 2 . The data set lower limits of about 40 GeV on QED cut-off parameters. We have searched for the decay υ (9.46) → γγ and obtain an upper limit Γ ( υ → γγ )/ Γ ( υ → all) < 1.4% (95% c.l.).

The cross section for e+e- to pi+ pi- psi(2S) between threshold and \sqrt{s}=5.5 GeV is measured using 673 fb^{-1} of data on and off the \Upsilon(4S) resonance collected with the Belle detector at KEKB. Two resonant structures are observed in the pi+ pi- psi(2S) invariant mass distribution, one at 4361\pm 9\pm 9 MeV/c2 with a width of 74\pm 15\pm 10 MeV/c2, and another at 4664\pm 11\pm 5 MeV/c2 with a width of 48\pm 15\pm 3 MeV/c2, if the mass spectrum is parameterized with the coherent sum of two Breit-Wigner functions. These values do not match those of any of the known charmonium states.

We have measured the total inelastic cross section (σinel) and charged-particle multiplicities obtained in pp collisions at 405 GeV/c. The data are from a preliminary 12 000-picture bubble-chamber exposure. We find σinel=32.8±1.0 mb; the low moments of the multiplicity distribution for negative particles are 〈n−〉=3.50±0.07, D−=2.37±0.05, f2−=2.1±0.2, and f3−=0.1±0.9. We also present updated results at 102 GeV/c.

Radiative decays of the $\phi$ meson have been studied using a data sample of about 19 million $\phi$ decays collected by the CMD-2 detector at VEPP-2M collider in Novosibirsk. From selected $e^+e^-\to\pi^{0}\pi^{0}\gamma$ and $e^+e^-\to\eta\pi^{0}\gamma$ events the following model independent results have been obtained: \par $Br(\phi\to\pi^{0}\pi^{0}\gamma) = (0.92\pm 0.08\pm0.06)\times10^{-4}$ for $M_{\pi^{0}\pi^{0}}>700$ MeV, \par $Br(\phi\to\eta\pi^{0}\gamma) = (0.90\pm 0.24\pm 0.10)\times10^{-4}$. It is shown that the intermediate mechanism $f_{0}(980)\gamma$ dominates in the $\phi\to\pi^{0}\pi^{0}\gamma$ decay and the corresponding branching ratio is \par $Br(\phi\to f_{0}(980)\gamma)=(2.90\pm 0.21\pm1.54)\times10^{-4}$. The systematic error is dominated by the possible model uncertainty. \par Using the same data sample the upper limit has been obtained for the P- and CP-violating decay of $\eta$ at 90% CL: \par $Br(\eta\to\pi^{0}\pi^{0}) < 4.3\times10^{-4}$ >.

Final total cross sections are given for a counter experiment at SLAC on hadronic photon absorption in hydrogen, deuterium, carbon, copper, and lead at incident energies from 3.7 to 18.3 GeV. Some of the nucleon cross sections have been revised and the C, Cu, and Pb data from 3.7 to 7.4 GeV have not been reported previously. The cross sections for complex nuclei vary approximately as A0.9 in our energy range, indicating that the photon interacts, at least partially, as a strongly interacting particle. The energy dependences of the proton and neutron cross sections are also similar to those of hadron-nucleon cross sections and hence may be fitted by a typical Regge parametrization, yielding σT(γp)=(98.7±3.6)+(65.0±10.1)ν−12 μb and σT(γn)=(103.4±6.7)+(33.1±19.4)ν−12 μb, where ν is the photon energy in GeV. These extrapolate to the same value at infinite energy, consistent with Pomeranchukon exchange, and the energy-dependent part yields an isovector-to-isoscalar-exchange ratio of 0.18 ± 0.06. While these observations are qualitatively consistent with vector meson dominance, quantitatively vector dominance fails in relating our results to ρ photo-production on hydrogen or to experiments determining the ρ-nucleon cross section. Vector dominance cannot be rescued by assuming that the ρ-photon coupling constant depends on the photon mass. Instead, an additional short-range interaction is apparently required, possibly due to a heavy (≳ 2 GeV / c2) vector meson or to a bare-photon interaction. The additional interaction accounts for approximately 20% of the total photoabsorption cross section.

Differential cross sections for the reaction π−p→π0n were measured at nine incident-pion kinetic energies in the interval from 500 to 1300 MeV. The negative pion beam from the bevatron was focused on a liquidhydrogen target completely surrounded by a cubic array of six steel-plate spark chambers. The spark chambers were triggered on events with neutral final states. Charge-exchange events were identified from the one-shower and two-shower events in the spark-chamber pictures. By the Monte Carlo technique, the π0 distributions were calculated from the bisector distributions of the two-shower π0 events together with the observed γ-ray distributions of the one-shower π0 events. These π0 distributions were fitted with both Legendre-polynomial expansions and power-series expansions by the method of least squares. The extrapolated forward differential cross sections are in good agreement with the dispersion calculations. The Legendre coefficients for the differential cross sections in isospin state T=12 were obtained by combining our results with available data on π±p elastic scattering. In the light of existing phase-shift solutions, the behavior of these coefficients is discussed. The D5F5 interference term that peaks near 900 MeV is verified to be in isospin state T=12 only. We report here also the total neutral cross sections and the cross sections for the production of neutral multipion final states 2π0n and 3π0n. The 4π solid angle and the calibrated energy response of the spark chambers contribute to the accuracy of the results.

The production of prompt $D^{0}$, $D^{+}_{\rm s}$, and $\Lambda_{\rm c}^{+}$ hadrons, and their ratios, $D^{+}_{\rm s}$/$D^{0}$ and $\Lambda_{\rm c}^{+}$/$D^{0}$, are measured in proton-proton collisions at $\sqrt{s}$ = 13 TeV at midrapidity ($|y| <0.5$) with the ALICE detector at the LHC. The measurements are performed as a function of the charm-hadron transverse momentum ($p_{\rm T}$) in intervals of charged-particle multiplicity, measured with two multiplicity estimators covering different pseudorapidity regions. While the strange to non-strange $D^{+}_{\rm s}$/$D^{0}$ ratio indicates no significant multiplicity dependence, the baryon-to-meson $p_{\rm T}$-differential $\Lambda_{\rm c}^{+}$/$D^{0}$ ratio shows a multiplicity-dependent enhancement, with a significance of 5.3$\sigma$ for $1< p_{\rm T} < 12$ GeV/$c$, comparing the highest multiplicity interval with respect to the lowest one. The measurements are compared with a theoretical model that explains the multiplicity dependence by a canonical treatment of quantum charges in the statistical hadronisation approach, and with predictions from event generators that implement colour reconnection mechanisms beyond the leading colour approximation to model the hadronisation process. The $\Lambda_{\rm c}^{+}$/$D^{0}$ ratios as a function of $p_{\rm T}$ present a similar shape and magnitude as the $\Lambda/K^{0}_{s}$ ratios in comparable multiplicity intervals, suggesting a potential common mechanism for light- and charm-hadron formation, with analogous multiplicity dependence. The $p_{\rm T}$-integrated ratios, extrapolated down to $p_{\rm T}$=0, do not show a significant dependence on multiplicity within the uncertainties.

The reaction e + e − → hadrons has been measured in the ϒ and ϒ′ region using the DASP detector at the DESY storage ring DORIS. The following final results are obtained: R had (9.5 GeV)=3.73±0.16±0.28, Γ ee ( ϒ )=(1.23 ± 0.08 ± 0.12) keV, B μμ ( ϒ )=(3.2±1.3±0.3)%, Γ ee Γ had Γ tot (ϒ′)=(0.55±0.11 ±0.06) keV , and M ( ϒ ′)− M ( ϒ )=(556 ±10) MeV.

The $e^+e^- \to \omega \pi^0 \to \pi^0 \pi^0 \gamma$ process was investigated in the SND experiment at the VEPP-2M collider. A narrow energy interval near the $\phi$-meson was scanned. The observed cross-section reveals, at the level of three standard deviation, the interference effect caused by $\phi \to \pi^0\pi^0\gamma$ decay. The cross-section parameters, as well as the real and imaginary parts of the $\phi$-meson related amplitude, were measured.

Results of the study of the e+e-->pi0 gamma process with SND detector at VEPP-2M collider in the c.m.s. energy range sqrt(s)=0.60-0.97 GeV are presented. Using 36513 selected events corresponding to a total integrated luminosity of 3.4 pb^-1 the e+e-->pi0 gamma cross section was measured. The energy dependence of the cross section was analyzed in the framework of the vector meson dominance model. The data are well described by a sum of phi,omega,rho0->pi0 gamma decay contributions with measured decay probabilities: Br(omega->pi0 gamma)=(9.34+-0.15+-0.31)% and Br(rho0->pi0 gamma)=(5.15+-1.16+-0.73)*10^-4 . The rho-omega relative interference phase is phi(rho,omega}=(-10.2+-6.5+-2.5) degree.

New bubble chamber data on the reactions K − n → π 0 Σ 0 in the c.m. energy range 1750–2200 MeV are presented and are compared with the predictions of the most recent partial-wave analysis of the reaction K N → πΣ . The comparison stresses the need for data involving a single value of isotopic spin in the study of this reaction. An analysis of the new data yields two satisfactory solutions involving only well established resonances.

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We have measured the charge-changing cross sections of 10.6 GeV/nucleon Au197 nuclei interacting in targets of CH2 (polyethylene), C, Al, Cu, Sn, and Pb. Cross sections for H are calculated from those measured in C and CH2. The total charge-changing cross sections are higher than those measured at energies of ≤1 GeV/nucleon. The measured cross sections for the heavier targets are somewhat larger than those predicted by a model based on data taken at lower energies with lighter targets. Partial charge-changing cross sections for the production of fragments from the incident Au projectiles were measured for charge changes (ΔZ) from ΔZ=+1,80Hg, down to approximately ΔZ=-29,50Sn. In comparison to lower energy measurements, these partial cross sections are found to be smaller for small ΔZ and larger or the same for large ΔZ. The H partial cross sections are found to follow a power law in ΔZ similar to that for heavier targets, instead of the exponential form observed at lower energies. Factorization is found to hold for all partial cross sections with ΔZ greater than two. In the heavier targets, the cross sections for one and two proton removal have significant contributions from electromagnetic dissociation. The electromagnetic dissociation contribution to the total cross section is derived and found to be relatively small, but with a strong dependence on the charge of the target nuclei of the form ZT1.75±0.01.

A comparison is made of the low-mass three-meson systems (πππ), (Kππ), (π K K ) and ( K K K ) diffractively produced in the reaction meson + proton → three mesons + proton. Several striking similarities and a few important differences are observed: (i) the reactions are consistent with the assumption that the three mesons decay entirely into a 0 − meson and a 0 + , 1 − or 2 + resonance; (ii) the three-meson mass spectra have a peak ≈ 250 MeV above the effective threshold M eff of the dominant decay mode and then fall off approximately as (mass) −3 ;(iii) the average spin 〈 J 〉 = 0.55 + 1.1 Q eff , where Q eff = M - M eff ; (iv) the average orbital angular momentum 〈 l 〉 increases according to 〈 l 〉 = 0.75 Q eff ; (v) the three-meson states are produced dominantly in unnatural spin-parity states and no evidence for their being resonant is found; (vi) the only natural spin-parity states found are the well-established 2 + resonances A 2 and K ∗ (1420); they have similar properties to the non-resonant unnatural parity states except for a dip at t = 0 in the dσ/d t distributions; (vii) both the unnatural and natural spin-parity states are produced mostly by an exchange of natural parity; (viii) there is evidence for two types of production mechanism with different polarization properties, one approximately conserving helicity in the t -channel and the other in the s -channel.

Differential and total cross sections for the quasifree reactions $\gamma p\rightarrow\eta p$ and $\gamma n\rightarrow\eta n$ have been determined at the MAMI-C electron accelerator using a liquid deuterium target. Photons were produced via bremsstrahlung from the 1.5 GeV incident electron beam and energy-tagged with the Glasgow photon tagger. Decay photons of the neutral decay modes $\eta\rightarrow 2\gamma$ and $\eta\rightarrow 3\pi^0 \rightarrow 6\gamma$ and coincident recoil nucleons were detected in a combined setup of the Crystal Ball and the TAPS calorimeters. The $\eta$-production cross sections were measured in coincidence with recoil protons, recoil neutrons, and in an inclusive mode without a condition on recoil nucleons, which allowed a check of the internal consistency of the data. The effects from nuclear Fermi motion were removed by a kinematic reconstruction of the final-state invariant mass and possible nuclear effects on the quasifree cross section were investigated by a comparison of free and quasifree proton data. The results, which represent a significant improvement in statistical quality compared to previous measurements, agree with the known neutron-to-proton cross-section ratio in the peak of the $S_{11}(1535)$ resonance and confirm a peak in the neutron cross section, which is absent for the proton, at a center-of-mass energy $W = (1670\pm 5)$ MeV with an intrinsic width of $\Gamma\approx 30$ MeV.

Using 2917 $\rm{pb}^{-1}$ of data accumulated at 3.773~$\rm{GeV}$, 44.5~$\rm{pb}^{-1}$ of data accumulated at 3.65~$\rm{GeV}$ and data accumulated during a $\psi(3770)$ line-shape scan with the BESIII detector, the reaction $e^+e^-\rightarrow p\bar{p}$ is studied considering a possible interference between resonant and continuum amplitudes. The cross section of $e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p}$, $\sigma(e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p})$, is found to have two solutions, determined to be ($0.059\pm0.032\pm0.012$) pb with the phase angle $\phi = (255.8\pm37.9\pm4.8)^\circ$ ($<$0.11 pb at the 90% confidence level), or $\sigma(e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p}) = (2.57\pm0.12\pm0.12$) pb with $\phi = (266.9\pm6.1\pm0.9)^\circ$ both of which agree with a destructive interference. Using the obtained cross section of $\psi(3770)\rightarrow p\bar{p}$, the cross section of $p\bar{p}\rightarrow \psi(3770)$, which is useful information for the future PANDA experiment, is estimated to be either ($9.8\pm5.7$) nb ($<17.2$ nb at 90% C.L.) or $(425.6\pm42.9)$ nb.

In an experiment performed at the CERN Intersecting Storage Rings as a part of an energy scan to detect the η c formation in p p annihilation, we studied the reaction p p →φφ→ K + K − K + K − . The total cross section has been determined to be 25.0± 7.4±3.8 nb.

The e+e- -> pi0 pi0 gamma process was studied in the SND experiment at VEPP-2M e+e- collider in the energy region 0.60-0.97 GeV. From the analysis of the energy dependence of measured cross section the branching ratios B(omega -> pi0 pi0 gamma)= (6.6 +1.4-0.8(stat) +-0.6(syst))x10^-5 and B(rho -> pi0 pi0 gamma)=(4.1 +1.0-0.9(stat) +-0.3(syst))x10^-5 were obtained.

We have measured the cross section $\sigma(e^+e^-\to\pi^+\pi^-\gamma(\gamma))$ at DA$\Phi$NE, the Frascati \phi-factory, using events with initial state radiation photons emitted at small angle and inclusive of final state radiation. We present the analysis of a new data set corresponding to an integrated luminosity of 240 pb$^{-1}$. We have achieved a reduced systematic uncertainty with respect to previously published KLOE results. From the cross section we obtain the pion form factor and the contribution to the muon magnetic anomaly from two pion states in the mass range $0.592 &lt; M_{\pi\pi} &lt; 0.975$ GeV. For the latter we find $\Delta a^{\pi\pi}_\mu = (387.2\pm0.5_{\rm stat}\pm2.4_{\rm exp}\pm2.3_{\rm th})\times 10^{-10}$

Differential cross sections for K − n → Σ o π o have been measured at K − momenta between 680 and 840 MeV/ c in a bubble chamber experiment. For K − n → Σ o π − the Σ o polarization was also determined. The measurements were combined with the available data on K − p → Σπ in an energy-dependent partial wave analysis in the center of mass energy range from 1520 to 1745 MeV. An acceptable fit was obtained with the well established resonances.

We present the results obtained with the magnetic detector DM1 at the Orsay storage ring ACO for the reaction e + e − → π + π − π 0 from 483 to 1100 MeV in the center of mass. Our data show without ambiguity an interference effect between the ω and φ mesons, which corresponds to a negative coupling constant product ratio Re( g γω g ω →3 π / g γφ g φ →3 π ) ; however our measurements above the φ, performed using kinematical analysis, can only be explained by a higher energy contribution. In addition, the parameters of the ω have been obtained with an improved accuracy compared to other experiments, and particularly the branching ratio B ω →e + e − = (6.75±0.69) × 10 −5 . We confirm that the reaction e + e − → π + π − π 0 proceeds essentially via a quasi-two-body state ϱπ , at the energy of the φ.

The cross section of the process e^+e^-\to \pi^+\pi^- was measured in the SND experiment at the VEPP-2M collider in the energy region 400<\sqrt[]{s}<1000 MeV. This measurement was based on about 12.4 \times 10^6 selected collinear events, which include 7.4\times 10^6 e^+e^-\to e^+e^-, 4.5\times 10^6 e^+e^-\to\pi^+\pi^- and 0.5\times 10^6 e^+e^-\to\mu^+\mu^- selected events. The systematic uncertainty of the cross section determination is 1.3 %. The \rho-meson parameters were determined: m_\rho=774.9\pm 0.4\pm 0.5 MeV, \Gamma_\rho=146.5\pm 0.8\pm 1.5 MeV, \sigma(\rho\to\pi^+\pi^-)=1220\pm 7\pm 16 nb as well as the parameters of the G-parity suppressed decay \omega\to\pi^+\pi^-: \sigma(\omega\to\pi^+\pi^-)=29.9\pm 1.4\pm 1.0 nb and \phi_{\rho\omega} = 113.5\pm 1.3\pm 1.7 degree.

The cross section of the process $e^+e^-\to \pi^+\pi^-\pi^0$ was measured in the Spherical Neutral Detector experiment at the VEPP-2M collider in the energy region $\sqrt[]{s} = 980 \div 1380$ MeV. The measured cross section, together with the $e^+e^-\to \pi^+\pi^-\pi^0$ and $\omega\pi^+\pi^-$ cross sections obtained in other experiments, was analyzed in the framework of the generalized vector meson dominance model. It was found that the experimental data can be described by a sum of $\omega$, $\phi$ mesons and two $\omega^\prime$ and $\omega^{\prime\prime}$ resonances contributions, with masses $m_{\omega^\prime}\sim 1490$,$m_{\omega^{\prime\prime}}\sim 1790$ MeV and widths $\Gamma_{\omega^\prime}\sim 1210$, $\Gamma_{\omega^{\prime\prime}}\sim 560$ MeV. The analysis of the $\pi^+\pi^-$ invariant mass spectra in the energy region $\sqrt[]{s}$ from 1100 to 1380 MeV has shown that for their descriptionone should take into account the $e^+e^-\to\omega\pi^0\to\pi^+\pi^-\pi^0$ mechanism also. The phase between the amplitudes corresponding to the $e^+e^-\to\omega\pi$ and $e^+e^-\to\rho\pi$ intermediate states was measured for the first time. The value of the phase is close to zero and depends on energy.

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High precision measurements of the form factors of proton, pion, and kaon for timelike momentum transfers of |Q^2|=s=14.2 and 17.4 GeV^2 have been made. Data taken with the CLEO-c detector at sqrt(s)=3.772 GeV and 4.170 GeV, with integrated luminosities of 805 pb^-1 and 586 pb^-1, respectively, have been used to study $e^+e^-$ annihilations into pi+pi-, K+K^-, and ppbar. The perturbative QCD prediction that at large Q^2 the quantity Q^2F(Q^2) for vector mesons is nearly constant, and varies only weakly as the strong coupling constant alpha_S(Q^2) is confirmed for both pions and kaons. In contrast, a significant difference is observed between the values of the corresponding pQCD suggested near-constant quantity, |Q^4|G_M(|Q^2|)/mu_p for protons at |Q^2|=14.2 GeV^2 and 17.4 GeV^2. The results suggest the constancy of |Q^2|G_M(|Q^2|)/mu_p, instead.

The cross section for the process e+e- --> omega pi0 --> pi0 pi0 gamma has been measured in the energy range 1.05--2.00 GeV. The experiment has been performed at the e+e- collider VEPP-2000 with the SND detector. The measured e+e- --> omega pi0 cross section above 1.4 GeV is the most accurate to date. Below 1.4 GeV our data are in good agreement with the previous SND and CMD-2 measurements. Data on the e+e- --> omega pi0 cross section are well described by the VMD model with two excited rho-like states. From the measured cross section we have extracted the gamma^* --> omega pi0 transition form factor. It has been found that the VDM model cannot describe simultaneously our data and data obtained from the omega --> pi0 mu+ mu- decay. We have also tested CVC hypothesis comparing our results on the e+e- --> omega pi0 cross section with data on the tau- --> omega pi- nu_{tau} decay.

In the experiment with the SND detector at VEPP-2M e^+e^- collider the process $e^+e^-\to\pi^+\pi^-\pi^0$ was studied in the energy range 2E_0 from 1.04 to 1.38 GeV. A broad peak was observed with the visible mass $M_{vis}=1220\pm 20$ MeV and cross section in the maximum $\sigma_0\simeq 4$ nb. The peak can be interpreted as a $\omega$-like resonance $\omega (1200)$.

The total hadronic cross section in e + e − annihilation has been measured at s = 57.77 GeV using 290 pb −1 data sample collected with the VENUS detector at KEK TRISTAN. The cross section obtained is 140.3 ±1.8 pb for s ′/ s ≥0.5, where s ′ is the square of the invariant mass of the final state hadrons. The present result together with the recent results from the LEP collaborations is used to determine the hadronic γ − Z 0 interference parameter, j tot had , to be 0.196±0.083. The result is in good agreement with the Standard Model prediction of 0.220.

Using 11.6 pb^{-1} of data collected in the energy range 0.984--1.06 GeV by CMD-2 at VEPP-2M, the cross section of the reaction e+e- to pi+pi-pi+pi- has been studied. For the first time an interference pattern was observed in the energy dependence of the cross section near the phi meson. The branching ratio of the phi to pi+pi-pi+pi- decay double suppressed by the G-parity and OZI rule is measured Br(phi to pi+pi-pi+pi-) = (3.93 +- 1.74 +- 2.14) \cdot 10^{-6}. The upper limits have been placed for the decays phi to pi+pi-pi+pi-pi0 and phi to eta pi+pi- Br(phi to pi+pi-pi+pi-pi0) < 4.6 \cdot 10^{-6} 90% CL, Br(phi to eta pi+pi-) < 1.8 \cdot 10^{-5} 90% CL.

The πpi-system produced in the charge exchange π−p-reaction at 100 GeV/c has been studied. The experiment was performed at the CERN SPS accelerator with the multiphoton hodoscope spectrometer GAMS-400

We have used 87 pb^-1 of data collected with the Collider Detector at Fermilab to search for new particles decaying to b bbar. We present model-independent upper limits on the cross section for narrow resonances which excludes the color-octet technirho in the mass interval 350 < M < 440 GeV/c^2. In addition, we exclude topgluons, predicted in models of topcolor-assisted technicolor, of width Gamma = 0.3 M in the mass range 280 < M < 670 GeV/c^2, of width Gamma = 0.5 M in the mass range 340 < M < 640 GeV/c^2, and of width Gamma = 0.7 M in the mass range 375 < M < 560 GeV/c^2.

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A statistical combination of searches for heavy resonances decaying to pairs of bosons or leptons is presented. The data correspond to an integrated luminosity of 35.9 fb$^{-1}$ collected during 2016 by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. The data are found to be consistent with expectations from the standard model background. Exclusion limits are set in the context of models of spin-1 heavy vector triplets and of spin-2 bulk gravitons. For mass-degenerate W' and Z' resonances that predominantly couple to the standard model gauge bosons, the mass exclusion at 95% confidence level of heavy vector bosons is extended to 4.5 TeV as compared to 3.8 TeV determined from the best individual channel. This excluded mass increases to 5.0 TeV if the resonances couple predominantly to fermions.

A dedicated sample of Large Hadron Collider proton-proton collision data at centre-of-mass energy $\sqrt{s}=8$ TeV is used to study inclusive single diffractive dissociation, $pp \rightarrow Xp$. The intact final-state proton is reconstructed in the ATLAS ALFA forward spectrometer, while charged particles from the dissociated system $X$ are measured in the central detector components. The fiducial range of the measurement is $-4.0 < \log_{10} \xi < -1.6$ and $0.016 < |t| < 0.43 \ {\rm GeV^2}$, where $\xi$ is the proton fractional energy loss and $t$ is the squared four-momentum transfer. The total cross section integrated across the fiducial range is $1.59 \pm 0.13 \ {\rm mb}$. Cross sections are also measured differentially as functions of $\xi$, $t$, and $\Delta \eta$, a variable that characterises the rapidity gap separating the proton and the system $X$. The data are consistent with an exponential $t$ dependence, ${\rm d} \sigma / {\rm d} t \propto \text{e}^{Bt}$ with slope parameter $B = 7.65 \pm 0.34 \ {\rm GeV^{-2}}$. Interpreted in the framework of triple Regge phenomenology, the $\xi$ dependence leads to a pomeron intercept of $\alpha(0) = 1.07 \pm 0.09$.

Pseudorapidity gap distributions in proton-proton collisions at sqrt(s) = 7 TeV are studied using a minimum bias data sample with an integrated luminosity of 7.1 inverse microbarns. Cross sections are measured differentially in terms of Delta eta F, the larger of the pseudorapidity regions extending to the limits of the ATLAS sensitivity, at eta = +/- 4.9, in which no final state particles are produced above a transverse momentum threshold p_T Cut. The measurements span the region 0 < Delta eta F < 8 for 200 < p_T Cut < 800 MeV. At small Delta eta F, the data test the reliability of hadronisation models in describing rapidity and transverse momentum fluctuations in final state particle production. The measurements at larger gap sizes are dominated by contributions from the single diffractive dissociation process (pp -> Xp), enhanced by double dissociation (pp -> XY) where the invariant mass of the lighter of the two dissociation systems satisfies M_Y <~ 7 GeV. The resulting cross section is d sigma / d Delta eta F ~ 1 mb for Delta eta F >~ 3. The large rapidity gap data are used to constrain the value of the pomeron intercept appropriate to triple Regge models of soft diffraction. The cross section integrated over all gap sizes is compared with other LHC inelastic cross section measurements.

A search for Majorana neutrinos in same-sign $WW$ scattering events is presented. The analysis uses $\sqrt{s}= 13$ TeV proton-proton collision data with an integrated luminosity of 140 fb$^{-1}$ recorded during 2015-2018 by the ATLAS detector at the Large Hadron Collider. The analysis targets final states including exactly two same-sign muons and at least two hadronic jets well separated in rapidity. The modelling of the main backgrounds, from Standard Model same-sign $WW$ scattering and $WZ$ production, is constrained with data in dedicated signal-depleted control regions. The distribution of the transverse momentum of the second-hardest muon is used to search for signals originating from a heavy Majorana neutrino with a mass between 50 GeV and 20 TeV. No significant excess is observed over the background expectation. The results are interpreted in a benchmark scenario of the Phenomenological Type-I Seesaw model. In addition, the sensitivity to the Weinberg operator is investigated. Upper limits at the 95% confidence level are placed on the squared muon-neutrino-heavy-neutrino mass-mixing matrix element $\vert V_{\mu N} \vert^{2}$ as a function of the heavy Majorana neutrino's mass $m_N$, and on the effective $\mu\mu$ Majorana neutrino mass $|m_{\mu\mu}|$.

A search has been performed for photons originating in the decay of a neutral long-lived particle, exploiting the capabilities of the ATLAS electromagnetic calorimeter to make precise measurements of the flight direction of photons, as well as the calorimeter's excellent time resolution. The search has been made in the diphoton plus missing transverse energy final state, using the full data sample of 4.8/fb of 7 TeV proton-proton collisions collected in 2011 with the ATLAS detector at the LHC. No excess is observed above the background expected from Standard Model processes. The results are used to set exclusion limits in the context of Gauge Mediated Supersymmetry Breaking models, with the lightest neutralino being the next-to-lightest supersymmetric particle and decaying with a lifetime in excess of 0.25 ns into a photon and a gravitino.

Using 3.07 ${pb}^{-1}$ of data collected in the energy range 0.60-0.97 GeV by CMD-2, about 150 events of the process $\epm \to \pch$ have been selected. The energy dependence of the cross section agrees with the assumption of the $a_1(1260) \pi$ intermediate state which is dominant above 1 GeV. For the first time \fourpi events are observed at the $\rho$ meson energy. Under the assumption that all these events come from the $\rho$ meson decay, the value of the cross section at the $\rho$ meson peak corresponds to the following decay width: \Gamma(\rho^0 \to \fourpi) = (2.8 \pm 1.4 \pm 0.5) {keV} or to the branching ratio B(\rho^0 \to \fourpi) = (1.8 \pm 0.9 \pm 0.3) \cdot 10 ^{-5}.