1Silvia Franchino Universita' Pavia IFAE09 Bari - 15/04/09

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 2009IFAE09 Bari

2Silvia Franchino Universita' Pavia IFAE09 Bari - 15/04/09

DREAM = Dual REAdout MethodPerformances of hadronic calorimeters limited by fluctuations in em fraction (f

em )

DREAM measures fem

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 particleCherenkov 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

3Silvia Franchino Universita' Pavia IFAE09 Bari - 15/04/09

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

PbWO4 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 Cher signal

Filter to read Scint signal

4Silvia Franchino Universita' Pavia IFAE09 Bari - 15/04/09

Some test beam (50GeV electrons) resultsPicture of crystal with 2 filters and 2 PMTs

Time structure of PbWO4

doped Mo 1% UV + YELLOW filters

VERY Good separation

of C, S

Prompt = CherenkovDelayed + exp tail =Scint

Molybdenum doping seems to be very promising;Very good improvements w.r.t. undoped crystalsProblems: 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