DREAM December 07 BGO Data Analysis based on QADC Signals L. La Rotonda, E. Meoni, A. Policicchio, G. Susinno, T. Venturelli Calabria University & INFN Cosenza

DREAM December 07 C Side ADC # 25 S Side ADC #26 SETUP & Data A : cookies + filters + standard gate [ ] e - 50GeV  -60 o +60 o [ ]  + 200GeV -90 o +90 o [ ] e - 50GeV horizontal scan B : cookies + filters + 10ns gate on C Side [ ] e - 50GeV  -60 o +60 o [ ] e - 50GeV  -50 o +40 o 25mm Pb C : no cookies + filters + 10ns gate on C Side [ ] e - 50GeV  -60 o +60 o D : no cookies +inverted filters +10ns gate C Side [ ] e - 50GeV horizontal scan E: no cookies + filters + 10ns gate on C Side [ ] e - 100GeV  -30 o +30 o PbWO 4

DREAM December 07 In some case, at large angles, signal on S side changes abruptly form – we don’t take care of such type of data Events SIGNAL SHAPE ADC Counts Events ADC Counts

DREAM December 07 θ > 0 Counts C 1 = η cere 1 + η α sci 1 Counts S 1 = γ sci 1 filter efficiency ->α geometrical factors -> η global efficiency S side -> γ S C When, at θ < 0, Cerenkov contribution is negligible : Counts C 2 = η α sci 2 Counts S 2 = γ sci 2 Counts C2 / Counts S2 = η α / γ = K and, if efficiencies don’t change with angles: η cere = Counts C – K Counts S C S PMT1PMT2 How to Measure Cerenkov contribution

DREAM December 07 PIONS run (1) Values from peak Gaussian fit The not regular shape could be ascribed to low photoelectrons statistic or to the difficult to fit signals very close to pedestal BUT: it’s very similar for two different data set

DREAM December 07 PIONS run (2) Data – G4 simulation comparison

DREAM December 07 PIONS run (3)

DREAM December 07 ELECTRONS (A) run ( 1 ) 1500V att. -14dB 1700V

DREAM December 07 ELECTRONS (A) run ( 2 ) 1700V 1500V att. -14dB

DREAM December 07 ELECTRONS (A) run ( 3 ) Typical shape K =.185 ??

DREAM December 07 ELECTRONS (B) run ( 1 ) 1300V 1700V gate 10 ns

DREAM December 07 ELECTRONS (B) run ( 2 ) 1300V 1700V Gate 10 ns

DREAM December 07 ELECTRONS (B) run ( 3 )

DREAM December 07 ELECTRONS (B) run ( 4 )

DREAM December 07 ELECTRONS (C) run ( 1 ) 1700V Gate 10 ns no cookies 1300V no cookies Same voltage as B Lower counts due to bad optical contact

DREAM December 07 ELECTRONS (C) run ( 2 ) 1300V no cookies 1700V Gate 10 ns no cookies

DREAM December 07 ELECTRONS (C) run ( 3 )

DREAM December 07 ELECTRONS (C) run ( 4 )

DREAM December 07 In the previous analysis C and S values are obtained from the Gaussian fit of the peak. To understand if C/S fluctuations depend from the employed method we have recalculated same quantities event by event. In this way we can too easily associate errors to C/S values.

DREAM December 07 ELECTRONS (C) run ( 5 ) Event by Event C/S

DREAM December 07 ELECTRONS (C) run ( 6 )  of data C/S values are compatible for the 3 methods The shape doesn’t changes

DREAM December 07 ELECTRONS (C) run ( 7 )  data / (C/S) fit

DREAM December 07 Shape in C/S plots is clearly due to the signals from Cerenkov side that show wide fluctuations whit angles. If fluctuations arise from photoelectron statistics they should be uncorrelated. So differences between C signal counts in different runs, at same angles, should be randomly distributed. If ‘fluctuations’ are the correct signals, changing with angles because of the optical properties of the crystal, they are correlated at the same angle, in different runs.

DREAM December 07 Differences between C side signals : C 1 = α cere + β scint (A: standard gate) C 2 = a cere + β γ scint (B:10 ns gate) Show that signals are clearly correlated and scale with angle as scintillation angle C 1 -C 2

DREAM December 07 Conclusions ( 1 )  BGO angular scan data have been analyzed.  The filters and appropriate gates on C side works well to disentangle cerenkov light from scintillation showing the good properties of the crystal.  If cookies are removed, bad optical contact, signals are largely attenuated.  C/S distribution in the angular scan shows a “scattered” structure especially around +20 degrees. It’s quite similar in all the data set and is found too in a very different analysis performed by the Roma1 group.  We explain such type of distribution as due to the optical properties of the crystal because of its particular geometry.  It’d be very useful to compare the C/S distributions from BGO and PbWO 4 because of the quite different crystal geometries. But PbWO 4 data have been acquired only at 3 angles.

DREAM December 07 Conclusions ( 2 )  C/S ratio is expected to be about constant at negative angles where cerenkov collected signal can be neglected. We observe clearly this effect in 1 data set only. We are investigating ….