E CM bias in the presence of Beamstrahlung Arik Florimonte & Mike Woods, SLAC September 15, 2004

Wakefields + DisruptionY-Z Kink instability (larger for WARM) (larger for COLD)(comparable at WARM, COLD) E-Spread + E-Z correlation + Y-Z Kink instability E CM Bias (larger for WARM) (comparable at WARM, COLD)(larger for WARM) E 1 and E 2 are beam energies measured by the energy spectrometers. (ISR and beamstrahlung are turned off for this study.) LC Machine Design (  y = 0)  (E CM bias ) (  y = 0) Max(E CM bias ) vary  y,  y WARM ppm170 ppm+1000 ppm COLD ppm30 ppm+250 ppm Summary of E CM bias Summary of E CM Bias studies w/ Beamstrahlung OFF

LC Machine Design (  y = 0)  (E CM bias ) (  y = 0) Max(E CM bias ) vary  y,  y WARM ppm170 ppm+1000 ppm COLD ppm30 ppm+250 ppm NLC'-5000 ppm10 ppm+50 ppm Summary of E CM bias NLC TESLA NLC’

Definition of E CM bias (BSL OFF) E 1 and E 2 are beam energies measured by the energy spectrometers. (ISR and beamstrahlung are turned off for this study.) where Definitions of E CM bias (BSL ON) studied Vary cutoff energy from GeV gives best results

Actually changes luminosity and hence beamstrahlung, due to waist focusing. So not ok for estimating E_bias!

NLC1 NLC NLC w/ random-ordered energy NLC NLC w/ random-ordered energy NLC NLC w/ random-ordered energy NLC NLC w/ random-ordered energy Tails are similar in both E1+E2 and E1-E2 distributions Clear difference in 2 distributions Negligible difference in 2 distributions

TESLA1 TESLA TESLA w/ random- ordered energy TESLA TESLA w/ random- ordered energy TESLA TESLA w/ random-ordered energy TESLA TESLA w/ random-ordered energy Tails are similar in both E1+E2 and E1-E2 distributions Negligible difference in 2 distributions Clear difference in 2 distributions

NLC’ NLC’ NLC’ w/ random-ordered energy NLC’ NLC’ w/ random-ordered energy NLC’ NLC’ w/ random-ordered energy NLC’ NLC’ w/ random-ordered energy Tails are similar in both E1+E2 and E1-E2 distributions Clear difference in 2 distributions Competing/cancelling ECM bias contributions

Offset scan, E CM bias vs. y-offset Beamstrahlung turned on E cutoff = 495 GeV Espread on- gaussian E

Offset scan, E CM bias vs. y dispersion Beamstrahlung turned on E cutoff = 495 GeV Espread on- gaussian E

NLC TESLA NLC’ LC Machine Design (  y = 0)  (E CM bias ) (  y = 0) Max(E CM bias ) vary  y,  y WARM ppm140 ppm+1120 ppm COLD ppm40 ppm+350 ppm NLC' ppm23 ppm-190 ppm Summary of E CM bias in presence of BSL (uses gaussian E results w/ E cutoff = 495 GeV)

LC Machine Design (  y = 0)  (E CM bias ) (  y = 0) Max(E CM bias ) vary  y,  y WARM ppm140 ppm ppm COLD ppm40 ppm+350 ppm NLC'-5002 ppm23 ppm-190 ppm Summary of E CM bias in presence of BSL (uses gaussian E results w/ E cutoff = 495 GeV) Summary of E CM bias without BSL LC Machine Design (  y = 0)  (E CM bias ) (  y = 0) Max(E CM bias ) vary  y,  y WARM ppm170 ppm+1000 ppm COLD ppm30 ppm+250 ppm NLC'-5000 ppm20 ppm+50 ppm