We have searched for resonance production in the reaction γγ→Ks0Kπ. No signal was found for theηc and an upper limit for the radiative with\(\Gamma _{\gamma \gamma }^{\eta _c } \) keV (95% c.l.) is obtained. For the glueball candidate η(1440) (previouslyi) the upper limit\(\Gamma _{\gamma \gamma }^{\eta (1440)} B(\eta (1440) \to K\bar K\pi )< 1.2keV(95\% c.l.)\) is derived. In the tagged data sample resonance formation of a spin 1 state at 1420 MeV is observed, which is absent in the untagged data. The mass and width of this state are consistent with those of thef1(1420); an analysis of decay angular distributions favours positive parity.
Data read from graph.. Additional overall systematic error decreasing from 25% in the lowest mass bins to 15% for M > 2.0 GeV.
Single π + production on protons by linearly polarized photons of 2.5 to 5 GeV was measured at squared four momentum transfers t between −0.01 and −0.6 (GeV/ c ) 2 . The results show that the differential cross section d σ ⊥ d t with the electric vector of the photon perpendicular to the reaction plane is much larger than d σ ‖ d t with the electric vector parallel to the reaction plane. The predictions of Regge models and of the vector meson dominance model are briefly discussed.
Axis error includes +- 0.0/0.0 contribution (?////).
Axis error includes +- 0.0/0.0 contribution (?////).
Axis error includes +- 0.0/0.0 contribution (?////).
We present results for the reactions K 0 p →Λπ + and K 0 p →∑ 0 π + , for |u'| <0. 05 ( GeV /c) 2 and kaon momenta between 1 and 8 GeV/ c . The experiment was performed ina neutral beam at the PS with a two arm spark chamber spectrometer. The cross sections show strong dependence on beam energy and momentum transfer u ′. Λ polarization is compatible with zero. We compare energy dependence of the backward cross sections with the baryon exchange model from π N scattering.
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The reactions gamma gamma -> pi^+pi^-pi^+pi^- and gamma gamma -> pi^+pi^0pi^-pi^0 are studied with the L3 detector at LEP in a data sample collected at centre-of-mass energies from 161GeV to 209GeV with a total integrated luminosity of 698/pb. A spin-parity-helicity analysis of the rho^0 rho^0 and rho^+ rho^- systems for two-photon centre-of-mass energies between 1GeV and 3GeV shows the dominance of the spin-parity state 2+ with helicity 2. The contribution of 0+ and 0- spin-parity states is also observed, whereas contributions of 2- states and of a state with spin-parity 2+ and zero helicity are found to be negligible.
Cross section for 4PI and (RHO0 RHO0) production.
Cross section for 4PI and (RHO+ RHO-) production.
Spin parity analysis fits for RHO0 RHO0.
Data on multiplicities of charged particles produced in proton-nucleus and nucleus-nucleus collisions at 200 GeV per nucleon are presented. It is shown that the mean multiplicity of negative particles is proportional to the mean number of nucleons participating in the collision both for nucleus-nucleus and proton-nucleus collisions. The apparent consistency of pion multiplicity data with the assumption of an incoherent superposition of nucleon-nucleon collisions is critically discussed.
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Using the internal beam of DESY elastic electron-proton cross-sections were measured at various angles between 32° and 130°, and with momentum transfers ofq 2=39, 60, 80 and 110 fm−2. Two single-quadrupole spectrometers, movable around a common liquid-hydrogen target, were used for analysing the momentum of the scattered electrons. Čerenkov and shower counters discriminated against pion and low-energy background. As a cross-section reference, recoil protons from elastic scattering atq 2=10 fm−2 were used, with a quantameter serving as an intermediate monitor. The data are consistent with the Rosenbluth formula, giving real form factorsG E andG M . Both continue to decrease with increasing momentum transfer, but somewhat faster than indicated by measurements performed so far.
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We present the first data on photon-photon annihilation into hadrons for CM energies > 1 GeV obtained with the detector PLUTO at the e + e − storage ring PETRA. Cross sections are extracted using an inelastic eγ scattering formalism. The results are compared to expectations from Regge-like models.
DEPENDENCE OF CROSS SECTION FOR ELECTRON-PHOTON SCATTERING (ANALOGOUS TO HAND'S FORMULA) ON VISIBLE HADRONIC ENERGY, CALCULATED BY TAKING PION MASSES FOR ALL CHARGED PARTICLES.
We report a high-statistics measurement of differential cross sections for the process gamma gamma -> pi^0 pi^0 in the kinematic range 0.6 GeV <= W <= 4.0 GeV and |cos theta*| <= 0.8, where W and theta* are the energy and pion scattering angle, respectively, in the gamma gamma center-of-mass system. Differential cross sections are fitted to obtain information on S, D_0, D_2, G_0 and G_2 waves. The G waves are important above W ~= 1.6 GeV. For W <= 1.6 GeV the D_2 wave is dominated by the f_2(1270) resonance while the S wave requires at least one additional resonance besides the f_0(980), which may be the f_0(1370) or f_0(1500). The differential cross sections are fitted with a simple parameterization to determine the parameters (the mass, total width and Gamma_{gamma gamma}B(f_0 -> pi^0 pi^0)) of this scalar meson as well as the f_0(980). The helicity 0 fraction of the f_2(1270) meson, taking into account interference for the first time, is also obtained.
Differential cross section for W = 0.61, 0.63 and 0.65 GeV.
Differential cross section for W = 0.67, 0.69 and 0.71 GeV.
Differential cross section for W = 0.73, 0.75 and 0.77 GeV.
The differential cross section for the process $\gamma \gamma \to \eta \pi^0$ has been measured in the kinematic range $0.84 \GeV < W < 4.0 \GeV$, $|\cos \theta^*|<0.8$, where $W$ and $\theta^*$ are the energy and $\pi^0$ (or $\eta$) scattering angle, respectively, in the $\gamma\gamma$ center-of-mass system. The results are based on a 223 fb$^{-1}$ data sample collected with the Belle detector at the KEKB $e^+ e^-$ collider. Clear peaks due to the $a_0(980)$ and $a_2(1320)$ are visible. The differential cross sections are fitted in the energy region $0.9 \GeV < W < 1.46 \GeV$ to obtain the parameters of the $a_0(980)$. Its mass, width and $\Gamma_{\gamma \gamma} \B (\eta \pi^0)$ are measured to be $982.3 ^{+0.6}_{-0.7} ^{+3.1}_{-4.7} \MeV/c^2$, $75.6 \pm 1.6 ^{+17.4}_{-10.0} \MeV$ and $128 ^{+3}_{-2} ^{+502}_{-43} \eV$, respectively. The energy and angular dependences above 3.1 GeV are compared with those measured in the $\pi^0 \pi^0$ channel. The integrated cross section over $|\cos \theta^*|<0.8$ has a $W^{-n}$ dependence with $n = 10.5 \pm 1.2 \pm 0.5$, which is slightly larger than that for $\pi^0 \pi^0$. The differential cross sections show a $\sin^{-4} \theta^*$ dependence similar to $\gamma \gamma \to \pi^0 \pi^0$. The measured cross section ratio, $\sigma(\eta \pi^0)/\sigma(\pi^0 \pi^0) = 0.48 \pm 0.05 \pm 0.04$, is consistent with a QCD-based prediction.
The total cross section integrated over ABS(COS(THETA*)) < 0.8.
The differential cross section as a function of angle for W = 0.85 GeV.
The differential cross section as a function of angle for W = 0.87 GeV.
We present new high statistics data on hadron production in photon-photon reactions. The data are analyzed in terms of an electron-photon scattering formalism. The dependence of the total cross section of Q 2 , the four-momentum transfer squared of the scattered electron, and on the mass W of the hadronic system is investigated. The data are compared to predictions from Vector-Meson Dominance and the quark model.
No description provided.
DEPENDENCE ON VISIBLE HADRONIC INVARIANT MASS.
Data read from graph.
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