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# Luca Stanco – INFN - Padova22 September 2010 1 Significance of TAU observation in OPERA Questions to OPERA: 1. Does it exist the  –  oscillation ? 2.

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Luca Stanco – INFN - Padova22 September 2010 1 Significance of TAU observation in OPERA Questions to OPERA: 1. Does it exist the  –  oscillation ? 2. Is it coherent with expectation ? We compute it as function of observed EVENTS (instead of the canonical dependence of LUMINOSITY)

Luca Stanco – INFN - Padova22 September 2010 2 Scenarios. 1.Standard: 5.3(2008+09) + 4.2(2010) + 4.2(2011) = 13.7*10 19 p.o.t 2.Small compensation in 2011: 5.3+4.2+4.5 = 14.0 3.More in 2010&2011: 5.3+4.7+5.0 = 15.3 4.Add MTE in 2011: 5.3+4.7+5.5 = 15.5 5.Add 2013 with MTE: 5.3+4.7+5.5+5.0 = 20.5

Luca Stanco – INFN - Padova22 September 2010 3 SIGNAL: for each scenario the 95% C.L. on the corresponding Poisson pdf is computed: - lower and higher limits on the TAU events we may observed - corresponding significance is computed (use Proposal efficiencies * 0.8, use 20% of error) BACKGROUND: use Proposal * 0.8 (we factorize out the different CC and NC efficiencies). Use 50% of error (not so relevant). This is a CONSERVATIVE choice (also because all channel are taken in a whole) And of course, we do not consider here the improvement in the background estimation with the increase of statistics

Luca Stanco – INFN - Padova22 September 2010 4 Check for 2008+2009 Data Sample: N tau =0.8*10.4*5.3/22.5=1.96±0.39 N bck =0.8*0.75*5.3/22.5=0.14±0.07 95% of C.L. 0 1 2 3 4

Luca Stanco – INFN - Padova22 September 2010 5 and the obtainable significance is quite fluctuating ! #  # N indication evidence observation (but, remember, only with largest bck)

Luca Stanco – INFN - Padova22 September 2010 6 #  # N limit of computation and use Feldman-Cousins Conclusions: if > 5-6 events we find “observation” anyway even with 20.5*10 19 p.o.t we may not “observe” Scen. 1 Scen. 5 Mean expect. (but, remember, only with largest bck)

Luca Stanco – INFN - Padova22 September 2010 7 1.Similar to curves of Proposal 2.At present really missing deeper studies with better Analysis and Monte Carlos 3.My conclusion is however similar: Luminosity does not really matter for the signal 4.We have to point towards BACKGROUND This is valid while answering question no. 1….

Luca Stanco – INFN - Padova22 September 2010 8 Luca Stanco – ISTITUTO NAZIONALE di FISICA NUCLEARE - Padova6 Maggio 2010 8 2. “Coherence” of the OPERA oscillation measure 5.3x10 19 p.o.t 13.7x10 19 p.o.t 15.5x10 19 p.o.t 20.5x10 19 p.o.t 90% C.L. 95% C.L. # of observed events FEW events: difficult but affordable #  “distant” from MINOS (remember, Tau with 80% efficiency) Need 2013-14 !!

Luca Stanco – INFN - Padova22 September 2010 9 Conclusions: OPERA is dominated by statistics, but... the Physics Results can be extracted afterwords, only once the Full DATA Sample has been exploited

Luca Stanco – INFN - Padova22 September 2010 10 Backup

Luca Stanco – INFN - Padova22 September 2010 11 13.7 14.0 15.3 15.5 20.5

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