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Extraction of pseudo-rapidity density distributions from the Forward Multiplicity Detector

Extraction of pseudo-rapidity density distributions from the Forward Multiplicity Detector. Alexei Kurepin, Alla Maevskaia INR RAS, Moscow. ALICE Week 9 September 2003. FMD & T0 layout Occupancy Background conditions Accuracy of the multiplicity reconstruction of HIJING events

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Extraction of pseudo-rapidity density distributions from the Forward Multiplicity Detector

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  1. Extraction of pseudo-rapidity density distributions from the Forward Multiplicity Detector Alexei Kurepin, Alla Maevskaia INR RAS, Moscow ALICE Week 9 September 2003

  2. FMD & T0 layout • Occupancy • Background conditions • Accuracy of the multiplicity reconstruction of HIJING events • Iterative procedure to extract a rapidity distribution different from HIJING shape Alla Maevskaia ALICE Week 9 September 2003

  3. FMD & T0 layout Absorber I T S Si1inner Si2outer Si1outer Si2inner I T S Si3 Alla Maevskaia ALICE Week 9 September 2003

  4. Charge particles occupancy in Pb-Pb collision dN/dh = 8000 Si1 inner Si1 outer Si3 This low occupancy gives as possibility to reconstruct multiplicity using Poisson distribution to extract the multiplicity from the number of empty pads in 0.1h and gives the average number of particles in a group of pads . Alla Maevskaia ALICE Week 9 September 2003

  5. Background condition using HIJINGpara with dN/dh =8000 primary/total ratio as function of h Si2outer Si2inner Si1outer Si3 Si1inner h=1.73 h=2.4 h=1.31 Material distribution (ITS + beam pipe) Alla Maevskaia ALICE Week 9 September 2003

  6. Multiplicity reconstruction of HIJING events Particle hits in detector ( primary+background) Primarydistribution Primaries in detector Mean of 10 events dN/dh = 8000 Reconstructed distribution 1 HIJNIG event dN/dh = 8000 Alla Maevskaia ALICE Week 9 September 2003

  7. Reconstructed multiplicity as a function of the generated one. Background Subtracted All hits reconstructed 1 Since the relative error of multiplicity behaves as so choosing a suitable h interval one can achieve relative errors of about 10% with dh ~0.5 Alla Maevskaia ALICE Week 9 September 2003

  8. Iterative procedure to extract a rapidity distribution different from HIJING shape (1) • Step 1: reconstruct event multiplicity using primary/total coefficients extracted with HIJING. • Step 2 : repeat the transport simulation using as input distribution the one obtained in Step1 • Step3 : Calculate new primary/total coefficients • Step 4: Use the new coefficients for background correction • Step 5 : Repeat procedure until new iterations will not change result Alla Maevskaia ALICE Week 9 September 2003

  9. Iterative procedure to extract a rapidity distribution different from HIJING shape (2) Step 2 Step 1 Step 3 Step 1 Step 2 Alla Maevskaia ALICE Week 9 September 2003

  10. Conclusions: • The material surrounding the FMD causes a primary/(primary+background) ratio as low as 0.4. • Using a given pseudo-rapidity distribution (HIJING ) and knowledge of the material distribution we have calculated the correction coefficients to reconstruct from the measured distribution the primary one. • We have demonstrated that by using an iterative procedure this method can be applied to unknown pseudo-rapidity distribution. Alla Maevskaia ALICE Week 9 September 2003

  11. Alla Maevskaia ALICE Week 9 September 2003

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