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Absolute luminosity in ALICE: preliminary results of first VdM scan

Absolute luminosity in ALICE: preliminary results of first VdM scan. F. Antinori, G. De Cataldo, A. Di Mauro, C. Garabatos , K. Oyama,. Introductory remarks. Only preliminary results available (ALICE Physics week outside CERN + “short” notice)

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Absolute luminosity in ALICE: preliminary results of first VdM scan

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  1. Absolute luminosity in ALICE: preliminary results of first VdM scan F. Antinori, G. De Cataldo, A. Di Mauro, C. Garabatos, K. Oyama, LBS 17/05/2010

  2. Introductory remarks • Only preliminary results available (ALICE Physics week outside CERN + “short” notice) • Conditions during scan not optimized (non colliding bunches, angle from dipole) • Beam intensity monitoringto be checked • No uncertainties will be quoted LBS 17/05/2010

  3. Used relations and assumptions • Luminosity with beams with Gaussian shape in transverse planefor BEAM1and  (x1 , y1) and BEAM2(x2 , y2) • If BEAM1 and BEAM2 are displaced by distances (dx, dy) • Fitting the trigger rate R = L where  is cross section of the process related to the trigger  Standard deviation by Gaussian fit result scanx and scanx are Assume B1 and B2 have same size (x, y) LBS 17/05/2010

  4. The trigger detector: V0 Two circular arrays of scintillators, timing properties allow counting beam-beam and beam-gas (background) rates. For the scan: V0-A .AND. V0-C V0A rin=8 cm, rout=100 cm V0C rin=8 cm, rout=76 cm 90 cm (3 nsec) 340 cm (11 nsec) LBS 17/05/2010

  5. The V0 detector in ALICE V0-A V0-C LBS 17/05/2010

  6. Scan summary FILL 1090, 10/5/10 acquisition flag LBS 17/05/2010

  7. Scan “timing” • V0 rate integrated over 10 s • Acquisition flag .TRUE. over 30 s LBS 17/05/2010

  8. Avg V0 rate vs beam separation • Gaussian fit results H: scanx = 63 [m] V: scany = 69 [m] • Top ~ 950 [Hz] • Error estimation not available yet Separation  5 [m]? Waiting for results of bump calibration scan run Rate  sqrt(N)/Twhere T=10 [s] LBS 17/05/2010

  9. Check with double Gaussian fit Double Gauss, H Single Gauss, H scany1=65.0m scany2=10.1m scanx=63.3m Double Gauss, V Single Gauss, V scany1=65.0m scany2=17.1m scany=68.6m • Shape of V scan to be checked • Negligible difference (<1%) for the present accuracy LBS 17/05/2010

  10. Beam intensity issues • Beam intensity from BCTDC • B134x109, B238x109with overlapped noise (about)  2x109 • BCTDC data fit with straight line  B1 decay: 0.39x109 [/h] B2: 0.18x109 [/h] • During Horizontal Scan (unit: x109)N1: 33.91  0.16% N2: 38.09  0.07% N1xN2:  0.23% • During Vertical ScanN1: 33.75  0.17 %, N2: 38.04  0.07% N1xN2:  0.24% (numbers with  give difference between start and end ofscan) • Bunch intensity from BCTFR • B1, bucket 1 + bucket 17851~ B1 int. from BCTDC (after offset correction) • B2, bucket 1 + bucket 8911 < B2 int. from BCTDC (after offset correction) (5 % difference) • Used B1-1 and B2-8911 available in logging DB, without corrections LBS 17/05/2010

  11. Luminosity and V0 cross section • Beam sizes • Top luminosity • V0 trigger cross section LBS 17/05/2010

  12. Outlook Requirements for next scan • One bunch per beam, no angle (dipole off or compensation) • “Optimal” bunch intensities and b* to be discussed with LHC • Schedule to be discussed LBS 17/05/2010

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