Quiz (experimental lecture III)
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1. Why are parallel tracks in the RICH associated to the same ring

2. What are sources of correlated background electron pairs

3. Why does one not observe a high mass correlated background source
(from jets) in Au+Au collisions?

4. What is the source of the high-pT low-mass excess in p+p collisions
(slide 96)

5. Why did PHENIX have to go through the pain of understanding their
background within an uncertainty of 0.25% when NA60 could
live with an uncertainty of ~1-2%? 

6. Why are fake matches in NA60 not reproduced by the mixed events

7. Name at least two properties of the IMR excess observed by NA60

8. Why will CMS not be able to measure a possible low mass enhancement at
the LHC

9. What is Npart (x axis on slide 92)? What is Ncoll (used in the y-axis
on slide 92)? What is Npart and Ncoll in pp collisions? Can you find a
simple relation between the two in proton-lead collisions?

10. Why is the random correlation ccbar curve softer than the default
PYTHIA ccbar curve (slide 91)

11. Why does DY at SPS cross the open charm contribution at lower masses
than at RHIC (slide 60 and 91)

12. You have measured two charged tracks in your experiments with the
following three vectors:
pt1 = 0.5 GeV, eta1 = 0.1, phi1 = 2.1 rad
and
pt2 = 0.3 GeV, eta2 = -0.1, phi2 = -0.45 rad
by looking at the pair properties (invariant mass) do you have any guess
if these particles where electrons, muons, or charged pions? Why? Can
you be sure? Which detector system would you use to verify your
hypothesis?

13. You have measured 2000 e+ e- pairs in the mass interval 600-900
MeV/c^2 in 100 TeV PbPb collisions at the future “SLHC". Using mixed events you have
estimated your combinatorial background to be 1950 pairs with
negligible statistical uncertainty.
- calculate the signal and its statistical uncertainty

From a hadronic cocktail you would expect 40 pairs with negligible uncertainty:

- calculate the relative enhancement factor (signal-cocktail)/cocktail
  and its

uncertainty (you may approximate N~B)

- how much more data do you need to collect to measure an enhancement
factor with a significance of 3 sigma and 5 sigma (assuming that the
enhancement factor remains the same as already measured)?

- how would a systematic uncertainty of 1% on the background yield
modify the significance on the signal yield (you may approximate N~B)