Search results for "meson"
showing 10 items of 1548 documents
About the realization of chiral symmetry in QCD2
1992
Two dimensional massless Quantum Chromodynamics presents many features which resemble those of the true theory. In particular the spectrum consists of mesons and baryons arranged in flavor multiplets without parity doubling. We analyze the implications of chiral symmetry, which is not spontaneously broken in two dimensions, in the spectrum and in the quark condensate. We study how parity doubling, an awaited consequence of Coleman's theorem, is avoided due to the dimensionality of space-time and confinement. We prove that a chiral phase transition is not possible in the theory.
Radiative corrections in Dalitz decays of π0, η and η′ mesons
2019
We briefly summarize current experimental and theoretical results on the two important processes of the low-energy hadron physics involving neutral pions: the Dalitz decay of π0 and the rare decay π0 → e+e−. As novel results we present the complete set of radiative corrections to the Dalitz decays η(′) → l+l−γ beyond the soft-photon approximation, i.e. over the whole range of the Dalitz plot and with no restrictions on the energy of a radiative photon. The corrections inevitably depend on the η(′) → γ*γ(*) transition form factors.
Neutrino flux prediction at MiniBooNE
2009
The booster neutrino experiment (MiniBooNE) searches for nu(mu)->nu(e) oscillations using the O(1 GeV) neutrino beam produced by the booster synchrotron at the Fermi National Accelerator Laboratory). The booster delivers protons with 8 GeV kinetic energy (8.89 GeV/c momentum) to a beryllium target, producing neutrinos from the decay of secondary particles in the beam line. We describe the Monte Carlo simulation methods used to estimate the flux of neutrinos from the beam line incident on the MiniBooNE detector for both polarities of the focusing horn. The simulation uses the Geant4 framework for propagating particles, accounting for electromagnetic processes and hadronic interactions in the…
Precision Study of η′→γπ+π− Decay Dynamics
2018
Using a low background data sample of 9.7×10^{5} J/ψ→γη^{'}, η^{'}→γπ^{+}π^{-} events, which are 2 orders of magnitude larger than those from the previous experiments, recorded with the BESIII detector at BEPCII, the decay dynamics of η^{'}→γπ^{+}π^{-} are studied with both model-dependent and model-independent approaches. The contributions of ω and the ρ(770)-ω interference are observed for the first time in the decays η^{'}→γπ^{+}π^{-} in both approaches. Additionally, a contribution from the box anomaly or the ρ(1450) resonance is required in the model-dependent approach, while the process specific part of the decay amplitude is determined in the model-independent approach.
Description of thef2(1270),ρ3(1690),f4(2050),ρ5(2350), andf6(2510)resonances as multi-ρ(770)states
2010
In a previous work regarding the interaction of two $\ensuremath{\rho}(770)$ resonances, the ${f}_{2}(1270)$ (${J}^{PC}={2}^{++}$) resonance was obtained dynamically as a two-$\ensuremath{\rho}$ molecule with a very strong binding energy, 135 MeV per $\ensuremath{\rho}$ particle. In the present work we use the $\ensuremath{\rho}\ensuremath{\rho}$ interaction in spin 2 and isospin 0 channel to show that the resonances ${\ensuremath{\rho}}_{3}(1690)$ (${3}^{--}$), ${f}_{4}(2050)$ (${4}^{++}$), ${\ensuremath{\rho}}_{5}(2350)$ (${5}^{--}$), and ${f}_{6}(2510)$ (${6}^{++}$) are basically molecules of increasing number of $\ensuremath{\rho}(770)$ particles. We use the fixed center approximation o…
Measurement of ϕ -meson production at forward rapidity in p+p collisions at s=510 GeV and its energy dependence from s=200 GeV to 7 TeV
2018
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section of φ(1020)-meson production at forward rapidity in p+p collisions at s=510 GeV via the dimuon decay channel. The partial cross section in the rapidity and pT ranges 1.2
Reggeized model forηandη′photoproduction
2003
A Reggeized model for $\ensuremath{\eta}$ and ${\ensuremath{\eta}}^{\ensuremath{'}}$ photoproduction on the nucleon is presented. In this model, $t$-channel vector meson exchanges are described in terms of Regge trajectories to comply with the correct high energy behavior. We compare this Reggeized model with an isobar model ($\ensuremath{\eta}$-MAID), where the $t$-channel exchanges are described by $\ensuremath{\rho}$ and $\ensuremath{\omega}$ poles. Both models contain the same resonance contributions, and describe current $\ensuremath{\gamma}p\ensuremath{\rightarrow}\ensuremath{\eta}p$ data up to ${E}_{\ensuremath{\gamma}}^{\text{lab}}=2\phantom{\rule{0.3em}{0ex}}\text{GeV}$ quite well,…
Role of pion exchange inηmeson photoproduction on the deuteron
2015
Incoherent $\ensuremath{\eta}$ photoproduction on the deuteron is studied, with the main emphasis on the role of final-state interactions. In addition to the previously studied mechanisms of $NN$ and $\ensuremath{\eta}N$ rescatterings, the role of an intermediate pion exchange is considered in detail, where first a pion is photoproduced on one nucleon and then rescatters into an $\ensuremath{\eta}$ meson on the other, the spectator nucleon. It is found that the role of this pion-mediated contribution is comparable in size to that of $\ensuremath{\eta}N$ rescattering. Results for total and semi-inclusive differential cross sections and associated polarization observables are presented. In pa…
Photoproduction of η and η′ mesons with EtaMAID
2016
The unitary isobar model EtaMAID has been updated with an extended list of nucleon resonances, fitted to recent and new data for differential cross sections and polarization observables. The nonresonant background is described by Regge trajectories of ω,ρ and a 1 , b 1 mesons and in addition Regge cuts, where vector and axial vector mesons are exchanged together with Pomeron and f 2 mesons.
Photo-production of tensor mesons
2016
Assuming that the f 2 (1270), f ′2 (1525), a 2 (1320), and K * 2 (1430) resonances are dynamically generated states from the vector meson-vector meson interactions in L = 0 and spin 2, we study the γp → f 2 (1270)[f ′2 (1525)]p , γp → a 0 2 (1320)p , and γp → K * 2 (1430)Λ(Σ) reactions. For the γp → f 2 (1270)p reaction, we find that the theoretical results for the differential cross sections are in good agreement with the experimental measurements and provide support for the molecular picture of the f 2 (1270) in the first baryonic reaction where it has been tested. Furthermore, we predict also the total and differential cross sections for other reactions. The results can be tested in futu…