Study of attenuation of light in SMD strips (for sector 5)

  • Input: ~1.7M minB pp events from 2004 run. Only data from sector 5 are analyzed below.
  • Gains for SMD from AuAu62 integrals

    MIP selection (Fig 1)

  • 8 '0' before and after 'x' (or 'xx') in the SMD pattern in U & V.
  • UxV point within a tower boundary (0.7x0.7 of tower size in eta & phi)
  • MIP response from towers: ADC-ped in [0.4,2.5]*predicted_MIP_response
  • Pres-1, Pres-2, and PostShower : ADC>ped+3*sigPed
  • for calibratioj use SMD ADC-ped>3chan

    Method

  • For every group of 20 strips and every subsector (A-E) accumulate 3 spectra:
    * ADC-ped/gain,
    * distance of UxV point to the end of strip with the readout ( i.e. to end with label in fig 1),
    *eta of UxV point.
  • find MPV using Landau fit to get the average MIP response, and fit Guass to get average distance to redout and average eta (Fig 2)
  • convert MIP response to average gain using formula
    gain= MPV*2.89*tgh(eta)
  • plot gain vs. distance for every group of strips and find (fit) the average. Fig 3 shows resulting average gains for strip boundles 1-20, 21-40,..., 261-280,.. for the U plane and then another 15 panles for the V plane. table with results is here
  • As the cross check plot average gain vs. strip ID (bundle) and chi2/DOF from fit (Fig 4)

    Conclusions
    * within statistical error attenuation of light within a strip is below 10% per 1 m
    * MIP response for the U-plain is on average 10% larger vs. V-plane. (U-plane is closer to IP for sector 5)
    * Statistic is not enough to obtain uncorrelated parematers 'A' and 'lam' from the fit of
    gain(x)=A*(exp(-x/lam)+exp(-2L/lam +x/lam) .

    plSmdG.C was used to produce this results.

    Fig 1.
    X-Y distribution of MIP's accepted after all cuts as seen from West towards the IP. Red lines in the left (right) panel mark position of U (V) strips. Generated with code from mip05b-8zAB.hist.root

    Fig 2.
    Exmaple of response of strips 101-120. Rows 1-5 correspond to subsectors A-E. First column shows adc-ped/gain with X-range -0.1 to 4; second shows UxV distance with X-range 0 to 150 cm; third UxV eta with X-range 0 to 2.5 (PS)

    Fig 3.
    Gain vs. distance for every group of strips .Common scales: X=[0,1.4] m, Y=[0.5,1.5]. U-plane in blue, V-plane in magenta. Note, V-plane has systematic lower gains. (PS)

    Fig 3.
    average gain vs. strip ID and chi2/DOF from fit (PS)