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K LOE L uminosity M easurement

Achim G. Denig (LNF) Fabio Ambrosino (Napoli). KLOE Physics Workshop La Biodola, 25. May 2001. K LOE L uminosity M easurement. Large Angle Bhabhas Very Large Angle Bhabhas Gamma Gamma Luminosity. M aster F ormula. Measured Bhabha - candidates. Background Studies.

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K LOE L uminosity M easurement

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  1. Achim G. Denig (LNF) Fabio Ambrosino (Napoli) KLOE Physics Workshop La Biodola, 25. May 2001 KLOE Luminosity Measurement Large Angle Bhabhas Very Large Angle Bhabhas Gamma Gamma Luminosity

  2. MasterFormula Measured Bhabha - candidates Background Studies Theoretical Generator (Berends et.al., BABAYAGA) GEANFI Simulation Systematics Checks MC - Data: Monte Carlo Driven Approach !  use Selection/Cuts which are well described by MC (Theory & Experiment)

  3. LAB - Selection - Cuts: | TCL1 - TCL2 | < 4 ns N Hits DC > 50 45° < Q+ - < 135 ° Acoll. ( r,  ) < 10 ° 300 MeV < E+ - < 600  800 MeV *  cos(Acoll. (3d) ) < - 0.975 * LAB Investigation of ‘99-LAB’s showed: ExperimentalAngular Distributions in goodagreement with MC - Distributions ( ONLY EmC !)  g g - Contamination Contamination with g g - Events which make Pair Production Big Systematic Effect due to Miscalibration of EmC (Intrinsic Resolution of EmC DE  42 MeV @ 510 MeV) Contamination with , * inserted in 2000   

  4. 3dim - Accolinearity 3dim - Accolinearity New Version of BABAYAGA ! 1% cos  > -0.975 LAB since DB-V6 

  5. LAB since DB-V7  Upper Energy Cut FILFO moved from 600 to 800 MeV 300 MeV < ECL < 800 MeV Losses [%] 800 MeV d L / L00< 3 % In 2000 < DB-V7 due to variations of EmC Energy Calibration Upper Energy Cut [MeV]

  6. LAB DB-V3 1999 Data cross section=758 nb Luminosity = LAB * ( 1 - 2.4 % ) DB-V4 July - Aug. 2000 B=0.52T  cross section=780 nb dramatic g g - contamination ( noisy channels ) Fraction of LAB-events w/o charged vertex Luminosity table will be provided using this data as an input DB-V6 Sept. 2000; 3dim. Accolinearity ( g g -Events )  cross section=780 nb Luminosity = LAB * ( 1 - 1.2 % ) ; strong variations due to dEEMC DB-V7, DB-V8 from Oct. 2000 ; Cluster Energy-Cut moved to 800MeV  cross section=797 nb Luminosity = LAB * ( 1 - 1.2 % ) ; less sensitive to dEEMC July 2000 gg contam. [%] Days  

  7. VLAB: Distributions Excellent Agreement E + - GEANFI Radiative Tail well described by Theory BABAYAGA Data  Cut at 400 MeV Losses negligible Q + -

  8. (45° - 90°) - (90° - 135°) (45° - 135°) VLAB: Systematics  Cut on Polar Angle of Clusters (EmC) selected by FILFO-LAB’s Small loss (<0.3%) at intersection Barrel - Endcap VLAB (only barrel)  < 0.1%  Fit P2 around 90° (Centre of Distribution) X0 = ( 89.86 ± 0.50 )° No left - right - Asymmetry  < 0.5 % dL / L

  9. VLAB: Background LAB - Sample VLAB - Sample Before Likelihood LAB - Sample VLAB - Sample m m g p+p-p0 Removed by E+- > 400 MeV Cut After Likelihood m m g  p+p-p0 0.3 % backgr.

  10. LAB vs VLAB …. more long term test for DB-V7 going on ! (LAB - VLAB) / LAB [ % ] Integrated Luminosity [nb-1] • LAB • VLAB Run 18322 - 18351 Run 18322 - 18351 expected difference 1.2 % due to LAB background NLAB * ( 1 - 1.2% ) / 798.6nb = ( 207.0 ± 0.5 ) nb-1 NVLAB * ( 1 - 0.3% ) / 424.2nb = ( 206.0 ± 0.7 )nb-1

  11. Summary I : VLAB  VLAB - Routine is well tested and shows expected results;  Inserted in Datarec Version 8;  VLAB had been recalculated recently for DB-V7 and for reprocessing of DB-V6;  More Work on Systematics Studies has to be done ---> Outlook ---------------------------------------------------------------------------------------------  Use g g - Counter as independent cross check ---> GGL Most tested and accurate Method for Luminosity - Measurement dL / L < 2%

  12. Outlook look forPermille Effects !  1E6 MC - Production ( GEANFI , BABAYAGA) to reduce stat. Error on effective cross section and use latest reconstruction  FILFO - Efficiency  Description of Bremsstrahlung at DC walls by GEANFI  Effect of Beam - Energy  Effect of Beam - Interaction - Point  (0,0,0) ---------------------------------------------------------------------------------------------  Number of VLAB - candidates written in DB on a file - by - file - basis (statistical accuracy poor for a single run: 30nb-1 dL = 0.9 % )  VLAB - Information available on Slow Control

  13. GGL GGL = Gamma - Gamma - Luminosity  BABAYAGA Version 2.0 calculates e+ e- g g (g g ) and allows to use g - g - Events for Luminosity - Evaluation  on FILFO - Level using the same phase space cuts as for LAB: 45° < Qg < 135 ° Eg > 300 MeV Qg - Acollinearity < 10 ° + Cut in Scatterplot NHits - 3dim. Acollinearity A3D  Inserted in Datarec Version 8 Effective cross section = 118 nb

  14. GGL Data Nov 2000 e e (g) g g (g) NHits 100 g g A3D 0 - 1.0 - 0.9 NHits A3D Tail due to noisy channels / M.Bg

  15. GGL Distributions after GGL Event Selection  Data Nov00 Babayaga Achim Denig Luminosity @ KLOE

  16. GGL vs VLAB …. more long term test for DB-V7 going on ! (VLAB - GGL) / VLAB [ % ] Integrated Luminosity [nb-1] • VLAB • GGL Run 18322 - 18351 Run 18322 - 18351 NVLAB * ( 1 - 0.3% ) / 424.2nb = ( 207.0 ± 0.7 ) nb-1 NGGL / 117.8nb = ( 204.5 ± 1.3 ) nb-1

  17. Summary II  No Limitations for Luminosity Measurement with Systematics on 1% Level found , but further studies have to be done !  According to many theoreticians the theoretical knowledge of the Large Angle Bhabha Process on the Percent-Level is very challenging  all we can say: Berends - and BABAYAGA - Generator agree on permille level  Bhabha Studies were so far intended for Luminosity Measurement  in addition are we able to extract some physics ? Study of QED processes e+e- e+e-g (g ) with the SND detector at VEPP-2M Eur.Phys.J.C 12(2000)

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