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A Digitizer for Monolithic A Digitizer for Monolithic Active Pixel SensorsActive Pixel Sensors

Christina DritsaChristina Dritsa1,2,31,2,3, Michael Deveaux, Michael Deveaux33

11IPHC, Strasbourg, France IPHC, Strasbourg, France 22GSI, Darmstadt, GermanyGSI, Darmstadt, Germany

33IKF, Goethe University Frankfurt/Main, GermanyIKF, Goethe University Frankfurt/Main, Germany

XLVIII International meeting in nuclear physicsXLVIII International meeting in nuclear physicsBormio, 25-29 January 2010Bormio, 25-29 January 2010

22

The The CCompressed ompressed BBaryonicaryonic MMatter Experimentatter Experiment

Exploration of the QCD Exploration of the QCD phase diagram at phase diagram at highest net baryon highest net baryon densitiesdensities

ExperimentalExperimental focus: rare focus: rare diagnostic probes (i.e. open diagnostic probes (i.e. open charm)charm)

Needs: Vertex detector with Needs: Vertex detector with sec. vtx resolution of 50µmsec. vtx resolution of 50µm

Uses Monolithic Active Pixel Sensors:• Single point resolution: ~ 1µm• Material budget: 0.05% X0

MVD

STS

RICH

TRDTOF

ECAL

S. Belogurov et al.

Artistic view of the MVD

TThehe M Micro-icro-VVertex ertex DDetectoretector

Occupancy: Up to 40 tracks/mm²

33

TThe simulation challengehe simulation challenge

• MAPS are non-depleted

• Signal charge is collected via thermal diffusion.

• Conventional simulation models fail => wrong model assumptions

IInput for the simulation:nput for the simulation:

0° 15° 30°

45° 60° 80°

Beam test at CERN-SPS, Beam test at CERN-SPS, 120 GeV/c pions120 GeV/c pionsMAPS sensor MIMOSA 17 MAPS sensor MIMOSA 17 ( pitch of 30 µm ) ( pitch of 30 µm )Different incident angles (0Different incident angles (0oo--8080oo))

44

Cluster Profile

E

• Energy from measured LandauEnergy from measured Landau

• Shape from measured LorentzShape from measured Lorentz

DDigitizerigitizer

Summary and Conclusion:

• A digitizer for MAPS is available• Cluster multiplicity and charge distributions reproduce reality with 10% accuracy.