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Forward Pi0-Meson Production at HERA  [PDF]
C. Adloff
Physics , 1999, DOI: 10.1016/S0370-2693(99)00906-5
Abstract: High transverse momentum pi0-mesons have been measured with the H1 detector at HERA in deep-inelastic ep scattering events at low Bjorken-x, down to x <~ 4.10^{-5}. The measurement is performed in a region of small angles with respect to the proton remnant in the laboratory frame of reference, namely the forward region, and corresponds to central rapidity in the centre of mass system of the virtual photon and proton. This region is expected to be particularly sensitive to QCD effects in hadronic final states. Differential cross-sections for inclusive pi0-meson production are presented as a function of Bjorken-x and the four-momentum transfer Q^2, and as a function of transverse momentum and pseudorapidity. A recent numerical BFKL calculation and predictions from QCD models based on DGLAP parton evolution are compared with the data.
Observation of the rare decay B+->K+pi0pi0 and measurement of the quasi-two body contributions B+->K*(892)+pi0, B+->f0(980)K+ and B+->chic0K+  [PDF]
The BaBar Collaboration,J. P. Lees
Physics , 2011, DOI: 10.1103/PhysRevD.84.092007
Abstract: We report an analysis of the charmless hadronic decays of charged B meson to the final state K+pi0pi0, using a data sample of 470+/-2.8 million BBbar events collected at the Y(4S) resonance. We observe an excess of signal events, with a significance above 10 standard deviations including systematic uncertainties, and measure the branching fraction and CP asymmetry to be B(B+->K+pi0pi0)=(16.2+/-1.2+/-1.5)x10^-6 and A_CP(B+->K+pi0pi0)=-0.06+/-0.06+/-0.04, where the uncertainties are statistical and systematic respectively. Additionally we study the contributions of the B+->K*(892)+pi0, B+->f0(980)K+ and B+->chic0K+ quasi-two body decays. We report the world's best measurements of the branching fractions and CP asymmetry of the B+->K+pi0pi0 and B+->K*(892)+pi0 channels.
Analysis of nature of phi -> gamma pi0 eta and phi -> gamma pi0 pi0 decays  [PDF]
N. N. Achasov
Physics , 2001, DOI: 10.1063/1.1482441
Abstract: We study interference patterns in the phi -> gamma a0 + pi0 rho -> gamma pi eta and phi -> gamma f0 + pi0 rho -> gamma pi0 pi0 reactions. Taking into account the interference, we fit the experimental data and show that the background reaction does not distort the pi0eta spectrum in the decay phi -> gamma pi eta everywhere over the energy region and does not distort the pi0 pi0 spectrum in the decay phi -> gamma pi0 pi0 when the invariant mass m_{pi0 pi0} > 670 MeV. We discuss the details of the scalar meson production in the radiative decays and note that there are conclusive arguments in favor of the one-loop mechanism phi -> K+K- -> gamma a0 (or gamma f0). We discuss also distinctions between the four-quark, molecular, and two-quark models and argue that the establishment of the scalar meson production mechanism in the phi radiative decays gives new strong evidence in favor of the four-quark nature of the scalar a0(980) and f0(980) mesons.
Vector-meson contributions do not explain the rate and spectrum in K_L -> pi0 gamma gamma  [PDF]
F. Gabbiani,G. Valencia
Physics , 2002, DOI: 10.1103/PhysRevD.66.074006
Abstract: We analyze the recent NA48 data for the reaction K_L -> pi0 gamma gamma with and without the assumption of vector meson dominance (VMD). We find that the data is well described by a three-parameter expression inspired by O(p^6) chiral perturbation theory. We also find that it is impossible to fit the shape of the decay distribution and the overall rate simultaneously if one imposes the VMD constraints on the three parameters. We comment on the different fits and their implications for the CP-conserving component of the decay K_L -> pi0 e+ e-.
Isospin violation in J/Psi to phi pi0 eta decay and the f0-a0 mixing  [PDF]
L. Roca
Physics , 2012, DOI: 10.1103/PhysRevD.88.014045
Abstract: The isospin violating $J/\Psi\to \phi \pi^0 \eta$ decay is thought to be dominated by the mixing of the $f_0(980)$ and $a_0(980)$ scalar resonances. We make a theoretical evaluation of the $J/\Psi\to \phi \pi^0 \eta$ decay extending our own previous model for other $J/\Psi$ decays into one vector meson and two pseudoscalars using the techniques of the chiral unitary approach. The scalar resonances are dynamically generated through the final state interaction of the pseudoscalar mesons implementing unitarity from the lowest order ChPT amplitudes. Besides the direct $J/\Psi\phi PP$ vertex, other mechanisms like the sequential exchange of vector and axial-vector mesons are shown to be important in order to obtain the actual strength of the mixing. We get a very good agreement with the $\pi^0 \eta$ invariant mass distribution and branching ratio with recent BESIII data. Quantification of the $f_0(980)-a_0(980)$ mixing is done and compared with results from several experiments.
Evidence for charged B meson decays to a1(1260)+/- pi0 and a1(1260)0 pi+/-  [PDF]
The BABAR Collaboration,B. Aubert
Physics , 2007, DOI: 10.1103/PhysRevLett.99.261801
Abstract: We present measurements of the branching fractions for the decays B+/- --> a1(1260)+/- pi0 and B+/- --> a1(1260)0 pi+/- from a data sample of 232 * 10^6 BB pairs produced in e+e- annihilation through the Y(4S) resonance. We measure the branching fraction B(B+/- --> a1(1260)+/- pi0) * B(a1(1260)+/- --> pi- pi+ pi+/-) = (13.2 +/- 2.7 +/- 2.1) * 10^-6 with a significance of 4.2 sigma, and the branching fraction B(B+/- --> a1(1260)0 pi+/-) * B(a1(1260)0 --> pi- pi+ pi0) = (20.4 +/- 4.7 +/- 3.4) * 10^-6 with a significance of 3.8 sigma, where the first error quoted is statistical and the second is systematic.
pi0 pi0 Scattering Amplitudes in the pi- p Charge Exchange Process and pi0 pi0 Phase Shift Analysis  [PDF]
Kunio Takamatsu
Physics , 1999,
Abstract: The amplitude analysis has been performed on the pi0 pi0 final state obtained in the pi- p charge exchange process. The pi0 pi0 scattering amplitudes have been obtained for the S and D waves by the Chew-Low extrapolation and the partial wave analysis. Breit Wigner parameters have been obtained for f0(1370) and f2(1270). I=0 S wave pi0 pi0 scattering phase shift has been obtained below K Kbar threshold. They agree well with the pi+ pi- standard phase shift data below 650GeV and deviate by about 10 degrees from the standard data above 650MeV. They show a different behavior from those of Cason and others. The pi0 pi0 phase shift data have been analyzed by the IA method. Resonance parameters have been obtained to be m_sigma =588 pm 12MeV and Gamma_sigma =281 pm 25MeV with r_c=2.76 pm 0.15GeV^-1. They are excellently in agreement with those obtained in the reanlysis on the pi+ pi- phase shift data.
Quark structure of f0(980) from the radiative decays phi(1020)->gamma f0(980), gamma eta, gamma eta', gamma pi0 and f0(980)->gamma gamma  [PDF]
A. V. Anisovich,V. V. Anisovich,V. A. Nikonov
Physics , 2000,
Abstract: Partial widths of the radiative decays $\phi(1020)\to\gamma f_0(980)$, $\gamma\eta$, $\gamma\eta'$, $\gamma\pi^0$ and $f_0(980)\to\gamma\gamma$ are calculated assuming all mesons under consideration to be $q\bar q$ states: $\phi(1020)$ is dominantly an $s\bar s$ state ($n\bar n$ component $\lesssim 1%$), $\eta$, $\eta'$ and $\pi^0$ are standard $q\bar q$ states, $\eta = n\bar n\cos\theta - s\bar s\sin\theta$ and $\eta'=n\bar n\sin\theta + s\bar s\cos\theta$ with $\theta\simeq 37^\circ$, and $f_0(980)$ is the $q\bar q$ meson with the flavour wave function $n\bar n\cos\phi + s\bar s \sin\phi$. Calculated partial widths for the decays $\phi\to\gamma \eta$, $\gamma\eta'$, $\gamma\pi^0$ are in a reasonable agreement with experiment. The measured value of the branching ratio $BR(\phi\to\gamma f_0(980))$ requires $25^\circ\le |\phi|\le 90^\circ$; for the decay $f_0(980)\to\gamma\gamma$ the agreement with data is reached at either $77^\circ\le\phi\le 93^\circ$ or $(-54^\circ)\le\phi\le (-38^\circ)$. Simultaneous analysis of the decays $\phi(1020)\to\gamma f_0(980)$ and $f_0(980)\to\gamma\gamma$ provides arguments in favour of the solution with negative mixing angle $\phi =-48^\circ\pm 6^\circ$.
Observation of a Narrow Meson Decaying to Ds+pi0 at a Mass of 2.32 GeV/c^2  [PDF]
the BABAR Collaboration,B. Aubert
Physics , 2003, DOI: 10.1103/PhysRevLett.90.242001
Abstract: We have observed a narrow state near 2.32 GeV/c^2 in the inclusive Ds+ pi0 invariant mass distributionfrom e+e- annihilation data at energies near 10.6 GeV. The observed width is consistent with the experimental resolution. The small intrinsic width and the quantum numbers of the final state indicate that the decay violates isospin conservation. The state has natural spin-parity and the low mass suggests a JP=0+ assignment. The data sample corresponds to an integrated luminosity of 91 fb-1 recorded by the BABAR detector at the PEP2 asymmetric-energy e+e- storage ring.
Search for a Charged Partner of the X(3872) in the B Meson Decay B --> X- K, X- --> J/psi pi- pi0  [PDF]
B. Aubert,BaBar Collaboration
Physics , 2004, DOI: 10.1103/PhysRevD.71.031501
Abstract: We search for a charged partner of the X(3872) in the decay B --> X- K, X- --> J/psi pi- pi0, using 234 million BBbar events collected at the Y(4S) resonance with the BaBar detector at the PEP-II e+e- asymmetric-energy storage ring. The resulting product branching fraction upper limits are BR(B0 --> X- K+, X- --> J/psi pi- pi0) < 5.4 x 10(-6) and BR(B- --> X- K0bar,X- --> J/psi pi- pi0) < 22 x 10(-6) at the 90% confidence level.
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