Nuclear Instruments and Methods in Physics Research A 502 (2003) 752–754 Natural cuts in search of New Physics phenomena. Example: eg-Wn-m % nn D. Anipko a, * ,1 , I. Ginzburg b , A. Pak a a Physics Department, Novosibirsk State University, Pirogova Street 2, Novosibirsk 630090, Russia b Theoretical Physics Department, Sobolev Institute of Mathematics, SB RAS, Acad. Koptyug prospect 4, Novosibirsk 630090, Russia Abstract To estimate the parameters of New Physics in the future experiments, the experimental data should be compared to thecross-sectionscalculatedintermsofsomemodel.Thevaluesofthemodelparameterscanthenbeextractedfromthe signal/background ratio (statistical significance, SS). It is shown that applying certain phase space cuts can sometimes improve the results. The ways of seeking for the ’’natural’’ cuts in the process/model are discussed. Results for eg-Wn-mnn are presented. r 2003 Elsevier Science B.V. All rights reserved. PACS: 02.70.Rr; 07.05.Kf; 13.38.Be; 12.60.Cn Keywords: Statistical significance; Anomalous coupling; Linear collider 1. Physics on the photon colliders Studying the triple gauge bosons anomalous interactions (beyond the Standard Model, SM) is an essential part of the program of Linear Colliders (LC) in the e þ e  mode [1], as well as in the eg and gg modes (Photon Colliders) [2,3]. The eg-Wn process was first considered as regards the Photon Collider program in 1984 in Ref. [4]. The anomalous gauge boson interactions in ee-WW; gg-WW; eg-Wn havebeenstudiedin Refs. [5] neglecting backgrounds and W-boson decay, and with the spectra, polarizations, and luminosities being far from the present-day under- standing. Theaboveinteractionscanbeexpressedtobeof theformofeffectiveLagrangianwiththestandard anomalous parameters Dk and l (the anomalous magnetic and quadruple momenta of W -boson, respectively) as eW w mn W m F n  W w m F n W mn h þð1 þ DkÞW w m W n F mn þ l m 2 W W w lm W m n F nl  : Here, the process signature with W decaying to muon and antineutrino is considered. This final state is easily detectable, but information about the angular distribution correlations is lost. Photon and electron are considered to be polar- ized. Electron spectrum (with ISR), photon energy spectrum, and polarization distributions are taken *Corresponding author. E-mail address: anipko@tornado.nsk.ru (D. Anipko). 1 Participation in ACAT’2002 is supported by HP-grant. 0168-9002/03/$-see front matter r 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-9002(03)00571-0