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Crossing-angle-or-not physics implications report from 19-01-04 phone-meeting

Crossing-angle-or-not physics implications report from 19-01-04 phone-meeting. cold crossing-angle head-on warm crossing-angle -. more IP tuning optics design constraints

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Crossing-angle-or-not physics implications report from 19-01-04 phone-meeting

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  1. Crossing-angle-or-not physics implicationsreport from 19-01-04 phone-meeting cold crossing-angle head-on warm crossing-angle - more IP tuning optics design constraints crab-cavity req. beam(strahlung) extraction SC mini-quad. electrostatic separators backgrounds collimation  get worse at 1 TeV technical issues physics issues evaluated hermetic  veto post-IP diagnostics transverse boost for energy and B and P not polarisation no killer arguments either way - quantify physics impact consensually TESLA collaboration meeting APDG session 22/1/2004

  2. meeting agenda of the physics evaluation http://www-flc.desy.de/bdir/BDIRmeetings.html 1.Introduction, specification and context of study, meeting goals10‘P. Bambade/LAL2. Smuon and stau searches with small slepton-neutralino mass differences Implications for dark matter interpretation in co-annihilation scenarios25‘Z. Zhang/LAL3.Smuon and stau searches with small slepton-neutralino mass differences20‘U. Martyn/DESYTentative conclusion & further work concerning impact on slepton search capabilities4.Crossing angle and luminosity spectrum measurement10‘D. Miller/UCL5. News from the ALPCG SLAC Workshop20‘E. Torrence/Oregon6.Polarisation effects of the crossing angle10’ K. Mönig/DESY7.Review of arguments for upstream / downstream polarimetry15‘G. Mortgat-Pick/DurhamP. Schüler/DESYTentative conclusion & further work concerning impact on energy and polarisation8.Status of the detector background simulations Comparison of recent beamstrahlung pair calculations20‘K. Büsser/DESY9.Electron identification & veto in the LCAL / LumCAL Comparison with recent results from Takashi Maruyama20‘K. Kousnetzova/DESY10.Update on gamma-gamma to hadrons calculation20‘T. Barklow/SLACTentative conclusion & further work concerning requirements on the backgroundand very forward region Conclude by LCWS04 - strengthen international collaboration (GLC) TESLA collaboration meeting APDG session 22/1/2004

  3. SUSY motivation for head-on mode • Some popular dark matter SUSY explanations need the LSP 0to be quasi mass-degenerate with the lightest sleptons , ,… •  co-annihilation mechanism • mSUGRA + new dark matter constraints from WMAP cosmic microwave background measurements point in this direction • Scenario considered also relevant more generally in the MSSM Acceptable solutions in mSUGRA: M. Battaglia et al. hep-ph/0306219 co-annihilation example with g-2 constraint J. Ellis et al. hep-ph/0310356 TESLA collaboration meeting APDG session 22/1/2004

  4. efficient / hermetic  vetocrucial for  measurement Signal Main background ee   0  0 ee  (e)(e)    ~ 10 fb  ~ 104 fb Transverse view imperfect spectator electron veto ? R = 1.2 cm hole at 20 mrad  10-3 background efficiency • Important LC channel, complementary to LHC • Precise slepton masses  DM  CMB constraints from Planck • (luminosity & energy strategy )(LC  cosmology ) TESLA collaboration meeting APDG session 22/1/2004

  5. Forward region geometries • Specs for study • l* = 4.1m  veto at 3.7m • holes 1.2cm radius • (2.1cm likely for x-angle) 1.head-on 1 bunch2.x-angle 1 bunch3.x-angle n bunches (pile-up) TESLA collaboration meeting APDG session 22/1/2004

  6. Ideal vs. realistic veto and head-on vs. cross-angle from Z. Zhang in-coming beam hole rout=2.1cm instead of rout=1.2cm • Low angle veto essential to reduce photon-photon background • Veto power is better in head-on collision mode TESLA collaboration meeting APDG session 22/1/2004

  7. Preliminary  result benchmark point D’ with m- = 12 GeV from Z. Zhang After requiring Nm=2 Normalized for L=500fb-1 cuts valid for both head-on and crossing-angle collisions signal efficiency ~ 80% spectrum end-points preserved  ms and mLSP can be measured with precision for this benchmark point  more model-independent : smallest m s- detectable wrt to veto angle and quality ? TESLA collaboration meeting APDG session 22/1/2004

  8. Preliminary  result benchmark point D’ with m- = 5 GeV from Z. Zhang Thrust axis angle in 3-dim  PT sum wrt thrust axis in the transverse plane Azimuthal dependance in the transverse momentum degradation visible but not huge head-on crossing-angle signal efficiency ~ 11 % ~ 8 % S/B ratio 3.1  1.3 2.4  1.1 Caveat 1 : TESLA  electron veto efficiencies with beamstrahlung pairs from single bunch crossing ; warm LC will need fast read-out (R&D?) to avoid pile-up Caveat 2 : some physics backgrounds still need to be fully included in the analysis TESLA collaboration meeting APDG session 22/1/2004

  9. Preliminary slepton study by H.U. Martyn TESLA collaboration meeting APDG session 22/1/2004

  10. Effect of crossing-angle on cms energy calibration • Acollinearity angle of Bhabha events monitor the luminosity-weighted centre-of-mass spectrum in the presence of ISR and beamstrahlung • • radiation = 0  changes in angles from the • 0.01*ECMS transverse boost in a 20 mrad • crossing-angle are corrected perfectly • • radiation > 1% use calorimetric information • • radiation < 1% use approximate correction • ( : “very good for symmetrical radiation”) •  simulation exercise started to check magnitude of potential bias • Desired precision ~ few 10-4- 5 10-5 for top & W masses • (10-5- 10-6 to improve MZmeasurement) S. Boogart D. Miller T. Barklow TESLA collaboration meeting APDG session 22/1/2004

  11. Steering and depolarisation from the solenoid with a 10 mrad crossing-angle K. Mönig (+ M. Woods) • Solenoid B field not aligned to momentum  deflection ~ 0.4 mrad • (assumes total length = 8 m, B = 4 T, Eb = 250 GeV) • 100 % longitudinal polarisation  spin precession to IP ~ 115 mrad • is known and can be corrected  P= 1- cos(0.115) = 0.7 % • If measurement error of polarimeter P~ 0.5 %  additional spin misalignment ~ 100 mrad  P= cos(0.115) – cos(0.215) = 1.6 % ! • Must include effects from fringe fields  P= 0.7 % • Physics requirement • new physics searches SM tests @ HE SM tests @ GigaZ • P~ 0.5 % P~ 0.2 - 0.1 %P< 0.1 % • extra vertical bends ( + some tuning ) required to correct for both effects ( M. Woods et al. are working on this ) G. Mortgat-Pick TESLA collaboration meeting APDG session 22/1/2004

  12. Energy and polarisation calibration strategies • Physics channels (Bhabhas, radiative Z returns, WW, We) give the relevant luminosity-weighted information  but need statistics • pre-IP calibration needed to monitor incoming changes in E and P • post-IP very desirable to measure beam-beam effects and validate • simulated predictions and biases; they provide important redundancy and can also be used in single-beam mode Head-on collisions  post-IP diagnostics quasi-impossible how essential are they ? E. Torrence P. Schüler Beam-beam depolarisation 1. spin precession in the magnetic field 2. spin-flip probability in beamstrahlung total depolarisation ~ 4  lumi - weighted TESLA collaboration meeting APDG session 22/1/2004

  13. Bottom-line on crossing-angle-or-not physics implications (preliminary) • Head-on is quantifiably • better for some topics • while crossing-angle is • preferable for some others • Both are acceptable for • physics • With TESLA one can in principle choose one or the other ? Proposed intermediate solution : 0.3 mrad x-angle Comparison and optimisation of cold/warm very forward veto capability and more comprehensive background studies seem more important TESLA collaboration meeting APDG session 22/1/2004

  14. Pair deposition and electron ID in the BeamCAL/LumCAL 6 2 BG Deposited Energy (arb. Units) Y (cm) 3 5 250 GeV e- 4 1 X (cm) SiLayers K. Büsser E. Kousnetzova T. Maruyama K. Mönig A. Stahl Large fake-rate if more than 3 bunch crossings pile-up TESLA collaboration meeting APDG session 22/1/2004

  15. background calculation T. Barklow Assume constant for Ecm (GeV) TESLA collaboration meeting APDG session 22/1/2004

  16. Tracker Occupancy = (# hits / train) / # channels T. Barklow TESLA collaboration meeting APDG session 22/1/2004

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