A. Ballestrero INFN and Dip. Fisica Teorica Torino

1. From SIXPHACT to PHANTOM A. Ballestrero INFN and Dip. Fisica Teorica Torino A short history of SIXPHACT PHANTOM now Future programs for ILC This is rather a letter of intent than a presentation Alessandro Ballestrero

2. A short history of SIXPHACT Six fermion calculations for LC are now 10 years old ! The first Joint ECFA/DESY Study: Physics and Detectors for a Linear Collider took place in 2006 First meeting in FRASCATI (5-6 February 1996) In one of the subsequent meeting (Munich September?) we presented the first completecalculations for six fermion final state. This was the first result with SIXPHACT ( Accomando Pizzio A.B.) For the following meeting GRACE produced results to compare with ours and immediately also SIXFAP (M. Moretti and PV group)entered the game Other six fermion MonteCarlos for Linear Collider have then appeared in these years Wizard, Lusifer,... All general purpose programs (Amegic, Phelac, Madevent,...) can now compute six fermion final states. Many comparisons have been done at subsequent ILC meetings Alessandro Ballestrero

3. A short history of SIXPHACT Method for computing amplitudes: diagrams for ¹ ¹ + ¡ d b b ¹ e e ¹ º u ! withthe use of subdiagrams computed only once. helicity amplitudes written with PHACT Alessandro Ballestrero

4. A short history of SIXPHACT Examples of subdiagrams Alessandro Ballestrero

5. A short history of SIXPHACT − SIXPHACT was used for studies of t t higgs and 3 boson physics Example of results : comparison of full 6f and approximations for 3 boson production NWA, SIGNAL and FULL as a function of cut dot, dashed for the two quark pairs Alessandro Ballestrero

6. A short history of SIXPHACT a further cut on e n reduces the effect for Alessandro Ballestrero

7. A short history of SIXPHACT Example of results : top and irreducible background for Higgs signal of different masses gaussian smearing Alessandro Ballestrero

8. A short history of SIXPHACT EW and QCD Higgs background as a function of real, reconstructed, missing mass Alessandro Ballestrero

9. A short history of SIXPHACT ¹ ¹ + + + ¡ ¡ ¡ ¡ ¡ ¡ + + + ¡ d d d ¹ ¹ ¹ ¹ 2Z2W e e e e e e ¹ ¹ ¹ ¹ ¹ ¹ u u u u e c c u º ! ! ! 4Z Mixed − SIXPHACT was used for studies of t t higgs and 3 boson physics Final states with a neutrino were therefore considered as they implied W+W- production SIXPHACT has not been extended to cover all possible final states If one consider all particles as outgoing, an 8 fermion process can be classified according to how can be grouped in pairs as 4Z, 2Z 2W, 4W or as mixed. e.g. therefore only 2Z2W amplitudes were implemented no multichannel technique was adopted For these final states and for the cuts used one optimized phase space at a time integrated with an adaptive routine (VEGAS) was enough: Alessandro Ballestrero

10. PHANTOM now PHANTOM 1.0 Belhouari Bevilacqua Maina AB Butterworth et al, Chanowitz Alessandro Ballestrero

11. PHANTOM now 2 4 ( ) O £ ® ® s e m PHANTOM main features: ●first 6f program for LHC ●complete : 4w + 2z2w + 4z + mixed ●new integration method developed for the first time in PHASE (Accomando Maina AB) Iterative-Adaptive Multichannel Merges best feautures of both! Adapts well to cuts Small number of channels required (Multimapping). Good efficiency ● amplitudes with PHACT ●extension and generalization of subdiagram method: 3 master amplitudes for 4w, 2z2w, 4z computed in this way all the rest by repeated calls ●oneshot generation: possibility of unweighted generation of any number of processes at the same time. Useful: 4q mn at LHC needs more that 160 processes ! ● contains important, expecially for LHC ●separation of various color contributions: les Houches accord 2 Alessandro Ballestrero

12. PHANTOM now PHANTOM has been used for boson boson scattering physics in collaboration with CMS groups of Torino and Rio for full analysis WW scattering effects are buried in WW fusion processes Important for EWSB studies Alessandro Ballestrero

13. Example of results PHANTOM now Alessandro Ballestrero

14. Example of results PHANTOM now Alessandro Ballestrero

15. Future programs for ILC WE INTEND TO EXTEND PHANTOM TO e+ e- COLLIDERS Integration methods, oneshot generation, amplitudes have a general validity They should work very well also in this case PDF should be substituted by isr and beamstrahlung. This implies two more variables of integration or unweighted generation of beamstrahlung. Should be no problem Number of possible processes for a given final state (eg. m n + quarks or six quarks) is much lowerbut it is important for physical studies to generate them simultaneously Many technical points remain to be fixed or changed, but the structure of the program should remain the same We plan to have the possibility to use both fully massive and massless amplitudes: Massless are more efficient and sufficient for many studies, but some require fully massive at least for comparison Alessandro Ballestrero

16. Future programs for ILC PHANTOM will have features and efficiency competitive with the other 6f MC for ILC But our main purpose in its extension is to use it as a tool for physics analyses and phenomenology It will be particularly suited for comparative studies between LHC and ILC physics potential We are in particular interested in extending to ILC our studies on Boson Boson scattering and alternative EWSB scenarios Several studies in this direction have already appeared (Chierici, Barklow,...) For discovering strong scattering effects the energy of the machine will be crucial. LHC can reach higher energies for parton interactions, but the luminosity is rapidly decreasing ILC on the other hand should have a much lower QCD background So it will be interesting to compare the reach of the two colliders in this field. A realistic study with all processes and detector simulation seems worthwhile We look forward for possible collaborations on our physics program. Alessandro Ballestrero

17. BACKUP Alessandro Ballestrero

18. Unitarization: eg: Butterworth,Cox,Forshaw PRD65(02)96014different ways of constructing amplitudes which are unitary from low order amp Must be prepared for the unexpected Must know SM “background” e.g VTVT Alessandro Ballestrero