OO Muon reconstruction in CMS

1

• Investigation of the 40 MHz structure
• with Test Pulse runs

• Problem 40 MHz structure
• Before the time boxes
• present in very few channels (1- 2/ chambers and
  
• topologically located in the minicrate in
  specific area)
• just a front of the clock is picked-up. Sensitive
  on grounding
• and threshold .
• on the Time-boxes
• The structure is present and known
• since TB2003 (first assembled Mini-crate) -
  Micheal-
• 1 effect). Was present in legnaro, in TB 2004 ,
  in SX5
• is almost uniform in all channels , SL,
  chambers.
• indipendent on scintillator/autotrigger L1A.
• indipendent on threshold. No quantified
  inefficiency
• and no quantified extra hits.
• TDC problems?
• Check with TP in legnaro

2

TP signals flow of command with TP In the
tests, TP was generated within 0 ns between
staggered cell i.e emulates normal tracks in the
middle of each semi-cell . Only cells in one
semi-column per TRB were pulsed ( cell 9, 25,
41,57) each event. 66 runs were performed
changing the delay between the clock and the
pulse of TP 10000 events per run read-out. The
L1A was sent at a fix bx from the orbit. No check
on the autotrigger was performed.
3

• TP generated with the orbit signal,
• 1chan/SL/ROB pulsed
• Same delay respect clock in all pulsed channels
• Delay shifted of 4 delay-steps i.e 640 ps
• per run.The accuracy
• Of the delay step is of 20 ps ( castellani )
• 65 runs analysed
• (10000 events each run but run 9th has only
• 4180 events and probably the delay was
• not changed..)
• NB the event has always the same
• BX number ,ie, is just the first event
• read out
• after the TDC reset.

All channels 1 run
One channel 1 run
MEAN TP value
Tdc count
4
SL 3 for the 4 channels MEAN TP value as a
function of delay
TDC units
TDC units
Dt 25ns
delay ( unit .85 ADC count.65-0.08 ns
5
TDC units
Dt 25ns
delay ( unit .85 ADC count.66 ns
6
SL 3 for the 4 channels occupancy
and
RMS
TDC units
delay ( unit .85 ADC count.66-.08 ns
7
conclusion

• The TP seems to be digitized almost always with
  the
• same value by the TDC.
• checking le mean value of 10000 events per delay
  point
• there is a 25 ns nonlinearity. Not clear for me
  if that is due
• to a mismatching of the delay-time step to the
  ADC count
• or if that is due exactly to a intrinsic TDC
  output non linearity
• results