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We evaluate the constraints on anomalous trilinear gauge-boson couplings that can be obtained from the study of electron-positron annihilation into $W$ pairs at a facility with either the electron beam longitudinally polarized or both…

High Energy Physics - Phenomenology · Physics 2009-10-28 V. V. Andreev , A. A. Pankov , N. Paver

The cross section of the process $e^+e^-\to\pi^+\pi^-$ has been measured in the center of mass energy range from 0.32 to 1.2 GeV with the CMD-3 detector at the electron-positron collider VEPP-2000. The measurement is based on a full dataset…

We demonstrate experimentally that the trident process $e^-\rightarrow e^-e^+e^-$ in a strong external field, with a spatial extension comparable to the effective radiation length, is well understood theoretically. The experiment, conducted…

High Energy Physics - Experiment · Physics 2023-03-01 Christian F. Nielsen , Robert Holtzapple , Mads M. Lund , Jeppe H. Surrow , Allan H. Sørensen , Ulrik I. Uggerhøj

The quark spin effects have been introduced in the Pythia 8 Monte Carlo event generator for the simulation of $e^+e^-$ annihilation by interfacing the generator with the StringSpinner package. The package allows to simulate quark spin…

High Energy Physics - Phenomenology · Physics 2024-10-16 A. Kerbizi , L. Lönnblad , A. Martin

Inclusive production cross sections of $\pi^\pm$, $K^\pm$ and $p\bar{p}$ per hadronic $e^+e^-$ annihilation event in $e^+e^-$ are measured at a center-of-mass energy of 10.54 GeV, using a relatively small sample of very high quality data…

High Energy Physics - Experiment · Physics 2013-10-07 The BABAR Collaboration , J. P. Lees , others

We analyse the pion electromagnetic, charged-current, and $\pi\gamma$ transition form factors at timelike momentum transfers $q$, $q^2=s\le 1.4$ GeV$^2$, using a dispersion approach. We discuss in detail the propagator matrix of the…

High Energy Physics - Phenomenology · Physics 2009-11-10 D. Melikhov , O. Nachtmann , V. Nikonov , T. Paulus

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…

High Energy Physics - Phenomenology · Physics 2009-09-25 V. Bernard , N. Kaiser , Ulf-G. Meißner

We sketch some recent ideas proposed as the mechanism behind the puzzling experimental results on baryon-antibaryon production in e+e- annihilation close to threshold. The essential new point in the proposed mechanism is that it is a…

High Energy Physics - Phenomenology · Physics 2007-05-23 Marek Karliner

I present some recent results on neutral pion photo- and electroproduction in the threshold region and discuss the low energy theorem for $E_{0+}$ and some novel ones for the $P$-waves. I also study the two-pion production process $\gamma N…

High Energy Physics - Phenomenology · Physics 2009-10-28 V. Bernard

Quark spin effects in $e^+e^-$ annihilation to pseudoscalar and vector mesons are implemented for the first time in the PYTHIA Monte Carlo event generator. The spin-dependent fragmentation of the string stretched between the produced…

High Energy Physics - Phenomenology · Physics 2024-07-11 A. Kerbizi , L. Lönnblad , A. Martin

We investigate near threshold neutral pion photoproduction off protons to fourth order in heavy baryon chiral perturbation theory in the light of the new data from MAMI. We show that the unitarity cusp at the secondary \pi^+ n threshold is…

High Energy Physics - Phenomenology · Physics 2009-11-07 Véronique Bernard , Norbert Kaiser , Ulf-G. Meißner

We report measurements of hadronic final states produced in $e^+e^-$ annihilations from the BaBar and Belle experiments. In particular, we present cross sections measured in several different processes, including two-photon physics,…

High Energy Physics - Experiment · Physics 2008-10-07 Selina Z. Li

We utilize the effective Lagrangian method within the tree-level Born approximation to explore $\phi$-meson photoproduction, i.e., $\gamma p \to \phi p$. Our analysis encompasses contributions from various sources, including the Pomeron,…

High Energy Physics - Phenomenology · Physics 2024-02-13 Sang in Shim , Yongsun Kim , Seung-il Nam

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,…

We review the physics involved in the production and decay of top quarks in e^+e^- -> ttbar near threshold, with special emphasis on the recent theoretical study on the decay process of top quarks in the threshold region. The energy-angular…

High Energy Physics - Phenomenology · Physics 2011-03-02 Y. Sumino

The results of an analysis are presented of some recent data on the reactions $e^+e^-\to\pi^+\pi^-\pi^+\pi^-$, $e^+e^-\to\pi^+\pi^-\pi^0\pi^0$ with the subtracted $\omega\pi^0$ events, $e^+e^-\to\omega\pi^0$, $e^+e^-\to\eta \pi^+\pi^-$,…

High Energy Physics - Phenomenology · Physics 2014-11-17 N. N. Achasov , A. A. Kozhevnikov

We investigate the decay $\phi\to\pi^+\pi^-\pi^0$ in an effective-Lagrangian framework that keeps the dominant $\rho\pi$ mechanism and the direct three-pion term explicitly separated at the amplitude level. The resonant contribution is…

High Energy Physics - Phenomenology · Physics 2026-04-21 Seung-il Nam , Jung Keun Ahn

We study the processes $e^+ e^-\to K^+ K^- \pi^+\pi^-\gamma$, $K^+K^-\pi^0\pi^0\gamma$ and $K^+ K^- K^+ K^-\gamma$, where the photon is radiated from the initial state. About 34600, 4400 and 2300 fully reconstructed events, respectively,…

High Energy Physics - Experiment · Physics 2010-04-12 The BABAR Collaboration , B. Aubert

Exclusive hadron production processes in photon-photon collisions provide important tests of QCD at the amplitude level, particularly as measures of hadron distribution amplitudes and skewed parton distributions. The determination of the…

High Energy Physics - Phenomenology · Physics 2009-09-25 S. J. Brodsky

This talk presents recent experimental findings at BESIII experiment, including three distinct studies. Firstly, it reports the measurements of the Born cross-sections of $e^+e^-\to\Sigma^+\bar\Sigma^-$, $\Xi^-\bar\Xi^+$,…

High Energy Physics - Experiment · Physics 2024-11-12 Xiongfei Wang