Electric charge screening effect in single-W production with the KoralW Monte Carlo

  • S. Jadach
  • W.  Placzek
  • M. Skrzypek
  • B.F.L. Ward
  • Z. Was
Theoretical Physics

Abstract.

Any Monte Carlo event generator in which only initial state radiation (ISR) is implemented, or ISR is simulated independently of the final state radiation (FSR), may feature too many photons with large transverse momenta, which deform the topology of events and result in too strong an overall energy loss due to ISR. This overproduction of ISR photons happens in the presence of the final state particle close to the beam particle of the same electric charge. It is often said that the lack of the electric charge screening effect between ISR and FSR is responsible for the above pathology in ISR. We present an elegant approximate method of curing the above problem, without actually reinstalling FSR. The method provides theoretical predictions of modest precision: \(\leq 2\%\). It is, however, sufficient for the current 1W data analysis at the LEP2 collider. Contrary to alternative methods implemented in other MC programs, our method works for the ISR multiphotons with finite \(p_{\mathrm {T}}\). Although this method is not an exact implementation of the complete/exact ISR, FSR and their interference, it is very closely modelled on it. We present a variety of numerical results obtained with the newest version of the KoralW Monte Carlo, in which this method is already implemented.

Keywords

Energy Loss Theoretical Prediction Transverse Momentum Electric Charge Event Generator 

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Copyright information

© Springer-Verlag Berlin Heidelberg / Società Italiana di Fisica 2002

Authors and Affiliations

  • S. Jadach
    • 1
  • W.  Placzek
    • 2
  • M. Skrzypek
    • 1
  • B.F.L. Ward
    • 3
  • Z. Was
    • 1
  1. 1.Institute of Nuclear Physics, ul. Radzikowskiego 152, 31-342 Cracow, Poland PL
  2. 2. Institute of Computer Science, Jagellonian University, ul. Nawojki 11, Cracow, Poland PL
  3. 3. CERN, Theory Division, 1211 Geneva 23, Switzerland CH

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