Possible further extensions in the new LEPS beamline in Spring-8 S. Daté Accelerator Division, SPring-8/JASRI LEPS Collab. Meeting Academia Sinica, Jan. 13, 2006

Contents 1.Introduction 2.A short summary of previous discussions on energy upgrade above 5 GeV 3.A new estimate of high energy gamma yield for X-ray re- injection scheme 4.Conclusion

§1. Introduction LEPS experiments have proved the accessibility to new frontiers in hadron physics by making use of its advantages in measuring the forward angular regions without harmful background noise and manipulating gamma ray characteristics through easy-to- access laser system. They also enjoy highly stable operation of Spring-8 accelerators and its low emittance electron beams. After 5 years of physics runs with several important outputs, we are in a position to discuss a new LEPS beamline with enhancement and emphasis of recognized advantages, supplements to weak points, and challenges to completely new possibilities, which all motivated by physics.

SPring-8 Beamline Map

Directions of extentions Energy -> 3.5 GeV in near future (Laser upgrade) ~> GeV ? Intensity -> /s (high power laser, LRNB, high current, round beam, new tagging system) Detector Polarized target

High Energy Backward Compton Photons

HELP production by X-ray re-injection

HLEP generation by X-ray re-injection (2) 8 GeV 100 mA SR Undulator X-ray mirror Reflectivity = = 10% E x =100 eV E  < 7.4 GeV Diamond mirror

Multilayer Reflectivity

A short summary of previous discussions X-ray generation  reflection & re-injection  gamma ray production Gamma yield =

Cross section depends on photon energy d ˙ I dE  / I e,

Re-focussing Thin undulator approximation e-e- 275x2  m 6x2  m ~100  rad Can s be mm 2 ? In principle, yes. spherical mirror

Bunch mode dominance  rad 60 cm h ~ 275  m e-e- v ~ 6  m

Bunch-bunch collisions Limit: Heat load at finger contact ~ Maximum: 174 bunch filling

Conclusion Provided  an undulator with  high reflectable (R > 0.1)spherical mirror for 100 eV photons  with timing adjustment system (mirror position z = m, dz = 6mm) We may obtain in principle.

*******LEPS/SP8 template******

*******Suppl****** (2)

HELP generation (3)

Primakov Production of 

Radiation formula

Conclusion in the meeting on Oct. 20, 2005 The maximum yield of gamma in 5~6 GeV region attainable in Spring-8 SR: in an 1A, 1.5 GeV SR: =>

Cross section convoluted with N ph  d ˙ I dE  / R / I e,

An undulator to produce 100 eV photons Matching of the first harmonics: kG K > 2

Yield of X-ray photons  d ˙ N ph d  /I e ( )

Compton cross section

Reflectivity of N=11 multilayer mirror

Exotics:  +,  (1405), S 11 (1535) q X(K  -bound), C(1480)   q glueball, hybrid, odderon(odd-glueball) --- multi-g(+qq) Dirac monopole High precision: hyperon photoproduction nucleon resonance (e.g.  pol +p   0 + p _pol ) A-dependence – mean free path nonmesonic decay of hypernucleus Compton scattering – nucleon swelling  0,  –lifetime, polarizability,   Primakoff (high E , forward) Others: J/  from d or A (c.f. E th (  +p  J/  +p)=8.1 GeV) CP violation (    )  GDH  polarized HD target