Photon Flux

For estimation the total number of produced $\phi$'s was chosen $N_{\phi}=10^{11}$. For a year experimental time $10^7$ s the corresponding $\phi$ production rate should be $10^4$/s. This rate is equivalent to $3\times10^{33}$ luminosity of $e^+ e^-$ collider which is a goal for $\phi$-factories.

As an example 2.5 cm of Be taget was chosen (7% rad.length, 4.6 $g/cm^2$) the same as was using in RadPhi experiment at CEBAF.

The total hadron production cross section for 4-6 GeV photons is 150 $\mu$b/nucleon and for $\phi$ production it is 0.5 $\mu$b/nucleon.

All together give a flux $7\cdot10^{9}$ photons/s for a $\phi$ rate of $10^4$/s.

To be able to reconstruct decay length in terms of life time units with accuracy better than one $\tau_S$ and for constrained purpose, about 2% uncertainty in photon energy is required. Existing tagging system is not capable to work with this flux but Pestov counters with 25 ps resolution could help.

For that value of photon flux and desired photon energy spread the coherent bremsstrahlung system, reported by Richard Jones (UConn) at Bloomington workshop can be used. With 8 GeV initial electrons it can produce 6 GeV photons with about 2% energy spread with intensity about $3\times10^8$ (plus about $2\times10^8$ of 5 and 4 GeV) For CPT study it should be 20 times more intensive photon beam.

Questions: Is $10^{10}$ flux achievable with tagged photons by 25 ps Pestov counters? Or by coherent bremsstrahlung system? With higher electron energy (16-20 GeV) may be it is posible to get this rate for 4-5 GeV photons. What is lifetime of the diamond crystal at that intensity? What is the physical limit of intensity?