Related papers: Four-pion production
We calculate the branching ratios of the yet unmeasured eta' decays into four pions, based on a combination of chiral perturbation theory and vector-meson dominance. The decays eta' --> 2(pi+ pi-) and eta' --> pi+ pi- 2pi0 are P-wave…
We report on baryon resonance production and decay in proton-proton collisions at a kinetic energy of $3.5$ GeV based on data measured with HADES. The exclusive channels $pp \rightarrow np\pi^{+}$ and $pp \rightarrow pp\pi^{0}$ as well as…
The differential cross section for the process $\gamma \gamma \to \pi^0 \pi^0$ has been measured in the kinematic range 0.6 GeV $< W < 4.1$ GeV, $|\cos \theta^*|<0.8$ in energy and pion scattering angle, respectively, in the $\gamma\gamma$…
Mechanism of di-pion transitions $nS\to n'S\pi\pi(n=3,2; n'=2,1)$ in bottomonium and charmonium is studied with the use of the chiral string-breaking Lagrangian allowing for the emission of any number of $\pi(K,\eta),$ and not containing…
A Monte Carlo generator has been constructed to simulate the reaction e^+e^- \to \gamma + 4 \pi, where the photon is assumed to be observed in the detector. Only initial state radiation is considered. Additional collinear photon radiation…
We investigate threshold pion photoproduction in the framework of heavy baryon chiral perturbation theory. We give the expansion of the electric dipole amplitude $E_{0+}$ to three orders in $\mu$, the ratio of the pion to nucleon mass, and…
The dominant contribution to the $\pi^0 \to 4\gamma$ branching ratio, coming from purely electromagnetic photon-splitting graph, is calculated. The result $Br(\pi^0 \to 4\gamma) \simeq (2.6 \pm 0.1) \cdot 10^{-11}$ is about three orders of…
A large set of cross sections for semi-inclusive electroproduction of charged pions ($\pi^\pm$) from both proton and deuteron targets was measured. The data are in the deep-inelastic scattering region with invariant mass squared $W^2$ > 4…
In this work, we make a systematical study on the four-body $B_{(s)} \to (\pi\pi)(\pi\pi)$ decays in the perturbative QCD approach, where the $\pi\pi$ invariant mass spectra are dominated by the vector resonance $\rho(770)$ and the scalar…
A study of the semi-analytical approach to four-fermion production in $e^+ e^-$ annihilation is presented. We classify all possible four-fermion final states and present results of new calculations for the `basic' processes with the…
We report a measurement of the branching fractions in the B0->J/Psi pi+pi- decay based on a 140/fb data sample collected at the Upsilon(4S) energy with the Belle detector at the KEKB e+e- collider. Charged pion pairs are found to arise…
The cross section for the dd -> 4He pi pi reaction is estimated near threshold in a two-step model where a pion created in a first interaction produces a second pion in a subsequent interaction. This approach, which describes well the rates…
In this paper, we studied the quasi-two-body $B_c \to D_{(s)} [ \rho(770),\rho(1450),\rho(1700) \to ] \pi \pi$ decays by employing the perturbative QCD (PQCD) factorization approach. The two-pion distribution amplitudes $\Phi_{\pi\pi}$ are…
We compute branching ratios of $B\to K\pi$ decays in the framework of perturbative QCD factorization theorem. Decay amplitudes are classified into the topologies of tree, penguin and annihilation, all of which contain both factorizable and…
Process of muon (pion) pair production with small invariant mass in the electron-positron high-energy annihilation, accompanied by emission of hard photon at large angles, is considered. We find that the Dell-Yan picture for differential…
Recent measurements of the pi^+pi^- invariant mass distribution at RHIC show a shifted peak for the rho meson in 100A GeV in peripheral Au + Au and even in p + p collisions. A recent theoretical study based on a picture of in-medium…
The process of the muon (pion) pair production with small invariant mass in the electron--positron high--energy annihilation, accompanied by emission of hard photon at large angles, is considered. We find that the Drell--Yan picture for…
We study heavy quarkonium production associated with gluons in $\rm e^+e^-$ annihilation as an illustration of the perturbative QCD (pQCD) factorization approach, which incorporates the first nonleading power in the energy of the produced…
We present and develop a general dispersive framework allowing us to construct representations of the amplitudes for the processes $P\pi\to\pi\pi$, $P=K,\eta$, valid at the two-loop level in the low-energy expansion. The construction…
We present the results of an energy-dependent and set of single-energy partial-wave analyses of single-pion photoproduction data. These analyses extend from threshold to 2 GeV in the laboratory photon energy, and update our previous…