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First measurement of s tot and s el expectations for 2011/12

First measurement of s tot and s el expectations for 2011/12. LHCC 21 Sept 2011 Karsten Eggert on behalf of the TOTEM Collaboration. Elastic scattering differential cross-section. b * = 3.5 m, Oct. 2010 (EPL 95 2011, 41001). Extend the measurement to lower |t| values.

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First measurement of s tot and s el expectations for 2011/12

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  1. First measurement of stot and selexpectations for 2011/12 LHCC 21 Sept 2011Karsten Eggerton behalf of the TOTEM Collaboration

  2. Elastic scattering differential cross-section b* = 3.5 m, Oct. 2010 (EPL 95 2011, 41001) Extend the measurement to lower |t| values Karsten Eggert–

  3. Total Cross-Section Measurement Optical Theorem: Use r from COMPETE fit: Normalisation with luminosity from CMS Uncertainty ± 4%  Measure dsel / dt at lowest possible |t| Karsten Eggert–

  4. First run with the b* = 90 m optics and RP insertion Un-squeeze from injection optics b* = 11m to 90m [Helmut Burkhardt, Andre Verdier] Very robust optics with high precision • Two bunches with 1 and 2 x 1010 protons / bunch • Instantaneous luminosity: 8 x 1026 cm-2 s-1 • Integrated luminosity: 1.7 mb-1 • Estimated pile-up: ~ 0.5 % • Vertical Roman Pots at 10 s from beam center • Trigger rate : ~ 50 Hz • Recorded events in vertical Roman Pots: 66950 Karsten Eggert–

  5. Proton tracks of a single diagonal (left-right coincidences) b*= 90 m b*=3.5 m Sector 56 Sector 56 t = -p2q2 x = Dp/p Sector 45 Sector 45 y = LyQy+ vy y* x = LxQx + xD + vx x* Lx ~ 0 Integrated luminosity : 6.2 nbarn-1 Inel. pile-up ~ 0.8 ev/bx_ Integrated luminosity : 1.65 mbarn-1 Inel. pile-up ~ 0.005 ev/bx Karsten Eggert–

  6. Angular Correlations between outgoing protons Ly ~ 260 m Lx ~ 0 - 3 m • Background negligible < 1% • Width of correlation band in agreement with beam divergence (~ 2.4 mrad) Karsten Eggert–

  7. Angular difference between the two outgoing protons [Qy* (proton1) - Qy* (proton2)] / √ 2 beam divergence s Q* / √ 2 Karsten Eggert–

  8. Optics, t-scale and acceptance • Perturbations: optics very robust (Ly ~ sRP), better than: • dΘx*/Θx*=1.3%syst • dΘy*/Θy*=0.4%syst • Non-linearities in Θx*(y) reconstructiondue to dLx/ds fixed: (checked via Lx) • t systematics: dt/t = 0.8% (low t) up to 2.6% (large |t|) • Acceptance correction factor < 3 at low |t|, based on f symmetry Karsten Eggert–

  9. Raw t-Distributions Acceptance corrected Comparison of the two diagonals Karsten Eggert–

  10. Efficiency Correction and Resolution Unfolding Trigger efficiency ~ 99.9 % Reconstruction efficiency ~ 91 % Unfolding correction Effect on slope: B=0.11 GeV-2 Karsten Eggert–

  11. Final Differential Cross-Section Extrapolation to t = 0: Exponential slope Good agreement with the measurement at |t| > 0.36 GeV2 [EPL 95 (2011) 41001] Total elastic cross-section: Karsten Eggert–

  12. Systematics and Statistics • t :[0.6÷1.8]%syst optics  <1%align. [3.4÷11.9]%stat (before unfolding) • ds/dt :4%syst lumin1%syst(acc.+eff.+backg.+tag) 0.7%syst unfold. • B :1%stat1%syst from t0.7%syst from unfolding • ds/dt(t=0) : 0.3%stat 0.3%syst (optics) 4%syst lumin1%syst(acc.+eff.+backg.+tag) • ∫ds/dt dt :4%syst lumin1%syst(acc.+eff.+backg.+tag) 0.8%stat extrap. • sTOT : (+0.8% ;-0.2%)syst   0.2%stat 2.7%syst= (+2.8% ; -2.7%)syst  0.2%stat • sEL :5%syst 0.8%stat • sINEL :(+2.4% ; -1.8%)syst  0.8%stat Karsten Eggert–

  13. Results Elastic exponential slope: Elastic diff. cross-section at optical point: Optical Theorem, sinel (CMS) = (68.0  2.0(syst)  2.4(lumi)  4.0 (extrap)) mb sinel (ATLAS) = (69.4  2.4(exp)  6.9 (extrap)) mb Karsten Eggert–

  14. Energy dependence of the exponential slope B Karsten Eggert–

  15. Energy dependence of the elastic and total cross-sections Karsten Eggert–

  16. Energy dependence of inelastic cross-sections Karsten Eggert–

  17. Running Strategy for 2011/12 • RP alignment was performed at b* = 1.5 m • by approaching the RP detectors to the sharp beam edges produced by the LHC collimators • Qualification for running at b* = 1 m, obtained via loss maps • b* = 90 m • 29. June : machine test run and first RP insertion to 10 s using alignment at b* = 1.5 m • 30 min of data taking  first measurement of stot • August : alignment of all vertical RPs, beam lost before hor. Alignment • No data taking • Plan for end of September: • 5 hours data taking at 5 s (vertical RP)  luminosity independent measurement • Horizontal alignment • October: at least one more run with 147 m alignment  diffraction • 2012: • Toward larger b* ~ 1 km Karsten Eggert–

  18. Acknowledgements • Thanks to: • The LHC crew • for giving us such a beautiful machine • for supporting continuously our TOTEM requests • The physics coordinator Massi Ferro-Luzzi • for his help in critical situations and not forgetting us • The Optics group • for the development of the magic 90m optics • The CMS collaboration • For the friendly collaboration and the luminosity measurement • All our friends, funding agencies and the CERN management Karsten Eggert–

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