1 / 16

Effect of beam energy spread on precision measurements of m t and m H

Effect of beam energy spread on precision measurements of m t and m H. Cornell University July 13-16, 2003. Beam instrumentation goals Top mass: 200 ppm (35 MeV) Higgs mass: 200 ppm (25 MeV for 120 GeV Higgs) W mass: 50 ppm (4 MeV) ??

mahon
Download Presentation

Effect of beam energy spread on precision measurements of m t and m H

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Effect of beam energy spread on precision measurements of mt and mH Cornell University July 13-16, 2003 • Beam instrumentation goals • Top mass: 200 ppm (35 MeV) • Higgs mass: 200 ppm (25 MeV for 120 GeV Higgs) • W mass: 50 ppm (4 MeV) ?? • ‘Giga’-Z ALR: 200 ppm (20 MeV) (comparable to ~0.25% polarimetry) • 50 ppm (5 MeV) (for sub-0.1% polarimetry with e+ pol) ??

  2. The beam energy spectrometers measure <E>, but for physics we need to know <E>lum-wt. Effect I am considering today is the beam energy spread. At NLC, s(E) ~ 0.3% rms, and at TESLA it is ~ 0.1% rms. (3000 ppm) (1000 ppm)

  3. Energy Spread Study • MatLIAR-generated files from Andrei Seryi • LIAR+DIMAD+Matlab used to generate files • Tools developed by NLC Accelerator physics group • Files were used for TRC studies • They were obtained with non-perfect machines: • LCs were initially misaligned and then brought • back to ~nominal luminosity by one-to-one • correction in the linac. • generates distributions of incoming beams at IP • 6 files each for NLC-500 and TESLA-500 machines • Electron and positron beams are symmetric; • ie. similar spotsizes, bunch lengths, charge • Guinea-Pig simulation • ISR and Beamstrahlung turned off • electron.ini and positron.ini files from MatLIAR simulation • beam1.dat and beam2.dat files for outgoing beam distributions • lumi.dat file for distribution of particles that make luminosity

  4. NLC-500 Results Tail Head

  5. TESLA-500 Results

  6. Summary of Results for energy spread effect Note: energies are given in units of ppm, ie. the deviation from the nominal energy, for example: E1, E2 and Ecm all come from The Guinea-Pig file lumi.dat ~500ppm effect for NLC ~ 50ppm effect for TESLA

  7. Kink instability is dominant cause for energy bias effect • tail of the bunch is disrupted in y • energy-z correlation of the incoming bunches exacerbates effect • Can consider collision of opposing bunches to be: • head-head collisions (high ECM) • head-tail collisions (nominal ECM) • tail-tail collisions (low ECM; lower luminosity due to disruption) • Why effect is larger for NLC than TESLA: • large E-z correlation results from having to reduce • wakefields in the warm machine by performing a phase • space rotation to shorten the bunch length and increase • the energy spread • large energy spread (for same reason to mitigate wakefields)

  8. Comparing “kink instability” for e+e- and e-e- at NLC-500 e+e- e-e- (NLC-G has beam parameters with uncorrelated, gaussian distributions)

  9. Comparing “kink instability” for e-e- at NLC-500, TESLA-500 e-e- e-e-

  10. “kink instability” for e-e- at NLC-500; effect of E-z correlation • With E-z • correlation e-e- 2. Without E-z correlation (made z dist’n uncorrelated with 120 mm rms) e-e-

  11. e+e- (NLC-6) Outgoing e- Outgoing e- Lumi-wted ECM Outgoing e-

  12. e-e- (NLC-6) Outgoing e- Outgoing e- Lumi-wted ECM Outgoing e-

  13. Y Deflection Scan (deflection angles) NLC-6 e+e- TESLA-6 e+e- NLC-6 e-e- TESLA-6 e-e- ‘sharp’ deflection curve will make beam-based feedback/feed-forward difficult

  14. Y Deflection Scan (luminosity) NLC-6 e-e- TESLA-6 e-e- NLC-6 e+e- TESLA-6 e+e-

  15. Y Deflection Scan NLC-6 e-e- NLC-6 e-e- Maximum luminosity occurs at zero deflection angle, not zero offset

  16. Summary • Kink instabilityreduced luminosity • bias in energy determination • - large for e+e- at NLC due to large • E-z correlation and large espread • - large for e-e- at both NLC and TESLA • minimizing deflection angle reduces effect • Energy bias for e+e- collisions at NLC is ~500ppm • large compared to desired precision on energy determination of <200ppm • need to understand associated systematics and compare to other sources • need to see if 500ppm effect can be reduced • For e-e- collisions at NLC and TESLA • deflection scans indicate that beam-based feedbacks will be difficult • need to find more optimal collision parameters than those used for e+e-

More Related