1. Silvia Franchino Universita' Pavia IFAE09 Bari - 15/04/09 1 Nuovi cristalli per la calorimetria a doppio readout DREAM collaboration (INFN Italy & US) Cagliari - Cosenza - Iowa State - Pavia - Pisa - Roma I - Texas Tech Silvia Franchino Univerità di Pavia 15 Aprile 2009 IFAE09 Bari

2. Silvia Franchino Universita' Pavia IFAE09 Bari - 15/04/09 2 DREAM = Dual REAdout Method Performances of hadronic calorimeters limited by fluctuations in em fraction (f em ) DREAM measures f em event by event by separating the Scintillation & Cherenkov lights to improve performances of Hcal for next generation hep experiments Scintillation light (S) created by every charged particle Cherenkov light (C) created by relativistic particles (em component of the shower ) C/S ratio --> correlated to f em We started the dual readout approach with Fiber calorimeter, Now we are trying to extend the method to Homogeneous materials (PbWO4, BGO) to gain with number of C photons, sampling fluctuations How separate C, S in homogeneous materials: Effects of corrections

3. Silvia Franchino Universita' Pavia IFAE09 Bari - 15/04/09 3 1) Move the scintillation wave length peak in order to separate C and S through emission spectrum (use of optical filters) 2) Increase the decay time in order to separate C and S through the time structure New Doped Crystals: to combine the advantages of BGO with the much higher C fraction of PbWO 4 GOALS PbWO 4 crystals doped with Mo (1, 5%) & Pr (0.5, 1, 1.5%) Pure PbWO4 Mo doping 1% Mo doping 5% λ(nm) Emission spectrum Mo-doping Pr-doping Emission Spectrum Filter to read Scint signal Filter to read Cher signal Filter to read Scint signal

4. Silvia Franchino Universita' Pavia IFAE09 Bari - 15/04/09 4 Some test beam (50GeV electrons) results Picture of crystal with 2 filters and 2 PMTs Time structure of PbWO 4 doped Mo 1% UV + YELLOW filters VERY Good separation of C, S Prompt = Cherenkov Delayed + exp tail =Scint Molybdenum doping seems to be very promising; Very good improvements w.r.t. undoped crystals Problems: auto-absorption --> low Cherenkov light yield (8 p.e. per GeV) NEXTS STEPS: new test beam this summer, Try lower Mo-doping concentration with the same shift of emission spectrum, but with low absorption; Change Cherenkov filter to read more C photoelectrons Change Cherenkov photocathode with more QE