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VDM Scan in Lead-Lead (Scan-III) … VERY preliminary

VDM Scan in Lead-Lead (Scan-III) … VERY preliminary. ALICE TM. Pb+Pb van der Meer Scan. and with multi BX condition. Remember: 114 colliding bunch pairs With 1 BX, intensity is too low to measure Luminosity at head-on bunch intensity of Beam-1 bunch intensity of Beam-2

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VDM Scan in Lead-Lead (Scan-III) … VERY preliminary

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  1. VDM Scan in Lead-Lead(Scan-III) … VERY preliminary K. Oyama, Heidelberg ALICE TM

  2. K. Oyama, Heidelberg Pb+Pb van der Meer Scan

  3. K. Oyama, Heidelberg and with multi BX condition • Remember: 114 colliding bunch pairs • With 1 BX, intensity is too low to measure • Luminosity at head-on • bunch intensity of Beam-1 • bunch intensity of Beam-2 • choose all colliding bunch combinations • vdM scan shape factor (height divided by area ) • No distinguishing possible for shape factor among BXs (assumption needed) • Cross Section

  4. K. Oyama, Heidelberg Intensity • Intensities distribute in factor 2 • Stable during the scan time within <2.7% • Bunch product of:6085.8x1018 [charges2]is used as

  5. K. Oyama, Heidelberg Reduced BCMask • Colliding bunches … 114 • BCMaks set only for 30 (SPD phase to be constant) • Scaling and proper calculation of beam current required  to be done • Currently, all C* triggers should be scaled by factor 114/30=3.8 for the rate (cross section) • ZDC triggers are all without BCMask, no correction needed

  6. K. Oyama, Heidelberg Pileup and Emittance Corrections 1ZSD • Highest rate observed • 1ZSD reached 6000 Hz • Negligibly small • No further consideration about pileup • Emittance is significantly decreasedduring the scan (few %) • Normal straight line fit (gray line inthe right plot) and correction applied • Later, decoupling Emittance correction and beam intensity is in plan

  7. K. Oyama, Heidelberg Some Anomaly in Data (I) • Strange peak seen in • C0OM3 • C0SMH • C0TVX • CVBAND • Including AC/E masks • Little or invisible inZDC and Muon C0OM3

  8. K. Oyama, Heidelberg Some Anomaly in Data (II) • C0TSC is not possible to analyze because of missing data • To be checked

  9. K. Oyama, Heidelberg Scan Shapes • Almost perfect Gaussian with baselinefor most of triggers D [mm]

  10. K. Oyama, Heidelberg Background • 121 bunches in, and 114 collisions • Background may scales with (114*2) / (7*2) = factor 16 • Data shows factor 8/0.8~10 … more/less OK

  11. K. Oyama, Heidelberg Cross Sections (VERY PRELIMINARY) ! Scaled with factor 3.8 for BCMask correction * Errors are all partial statistical (not fully considered) * Up to 5 to 10% statistical error are there for width

  12. K. Oyama, Heidelberg Summary • Preliminary result of Pb+Pb van der Meer scan shown • 1ZED: 362 barn … comparable to estimation by Nora, Chiara et.al., • PWG2 on Mar.15, 2011: =185 b, =5.9 b, =7.8 b • TM on Nov.05, 2010: 2x185 - 5.9 + 7.8 = 372 barn • CVBAND: 10.6 barn … comparable to =8b with 8 fmPb radius • EM events cross section to be added • C0SMH: 6 barn … pure nuclear interactions, consistency check with Glauber possible? • However, please consider central value may significantly move • To be done: • Satellite bunch and ghost charge analysis (to/from BCNWG) • Background study • Precise bunch intensity with proper selection of BX for C* triggers • Cross checks … Which process? Inter-experiments?

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