SuperB with Two Interaction Regions Is it possible to obtain luminosity per each IP? P.Raimondi, D.N.Shatilov, A.Variola,M.Zobov

Preliminary Considerations 1.From one hand, the maximum achievable tune shift is expected to be constant. So, with 2 IPs the bunch current should be reduced by a factor of two. In this case the luminosity per IP should be a factor of 4 smaller. 2.On other hand, a 2IP symmetric collider (no crossing angle) can be considered as a 1IP collider, but with twice longer damping time in terms of revolution turns. A luminosity reduction of the order of 2 1/3 is expected in that case. 3.Besides, a partial compensation of beam-beam effects with 2 IPs (or more) is possible. For example, LEP experience with 4 IPs or LHC upgrade plans with long bunches and large crossing angle. Can we exploit the property that the crossing angle has different signs in the first and in the second interaction points?

Natural Way to Perform Simulations: 1.Start with symmetric phase advances between the IPs 2.Find good working point areas above the half-integers and above the integers. 3.Intuitively, the best tunes should be found when the following condition is satisfied : 2 x (good area above half-integers) is overlapped with (good area above the integers). 4. Try to optimize the phase advances between the IPs 5. Final full luminosity tune scan.

1IP Scan above Half Integers In the first order in perturbation nQx + mQy + kQs = integer m should be even (n + k) should be even 2Qx – 2Qs (first order) 2Qx – 1Qs (higher order) 4Qx – 2Qs (first order) ? 2Qx – 4Qs (first order) Q s = 0.02 L max = 1.21x10 36 cm -2 s -1

1IP Scan above Integers In the first order in perturbation nQx + mQy + kQs = integer m should be even (n + k) should be even 1Qx – 7Qs (first order) 1Qx – 5Qs (first order) 1Qx – 3Qs (first order) Q s = 0.02 L max = 1.02x10 36 cm -2 s -1

E - = 7 GeV E + = 4 GeV N - = 3.52 x N + = 6.16 x C = 2250 m N bunches = 1733 L = 1.01 x L = 0.97 x per IP Tune advance between IPs (0.555, 0.565, 0.01) 1 IP2 IPs D. Shatilov, M. Zobov Beam-Beam Induced Tails

Luminosity Tune Scan 1 IP2 IPs L min = 3.95 x cm -2 s -1 L max = 1.02 x cm -2 s -1 Lmin = 3.37 x cm -2 s -1 Lmax = 1.00 x cm -2 s -1 Qy Qx

Qy Ax Ay Distribution Tails at (0.155, 0.185) cm -2 s -1

Vertical Phase Advance Scan  x (IP 1 - IP 2 ) = 2  Q x = Q y =  y (IP 1 - IP 2 )

Double Phase Advance Scan  x /2   y /2   x,  y are phase advances between IP 1 and IP 2 The total tune (0.155, 0.185) The best choice is symmetric 2 x  x /2  integer 2 x (  y /2  ) = integer

Full Scale Luminosity Scan with 2 IPs Sum synchrobetatron resonancesDifference synchrobetatron resonances cm -2 s -1

Conclusions Beam Beam studies for a 2 IPs machine are very promising 1 IP does not saturate the BB effects with design parameters The two crossing angles, positive and negative are beneficial to the luminosity, further minimizing harmful resonances Overall deliverable luminosity can double for a given machine power To do: for now just some more detailed studies on BB with 2 IPs. Make up a ring with 2 interaction regions will require a lot of work and at the moment is “low-priority”, unless the 2 IPs machine becomes a real possibility…