1. The ALICE Forward Multiplicity Detector Kristján Gulbrandsen Niels Bohr Institute for the ALICE Collaboration

2. The ALICE Detector TPC ITS HMPID TRD PHOS TOF V0T0 FMD

3. Physics Motivation Extend detection of total particles to forward (and backward) direction - increasing range of dN ch /d  Measure azimuthal asymmetry of particles to determine event plane and perform elliptic flow measurements Provide additional measure of centrality Want a detector which has, on average, less than 1 particle per channel per event for the most central events

4. FMD Detector 3 regions of detectors to extend the  acceptance Each ring split into sectors of silicon modules 10240 silicon strips per ring 3.68<  <5.031.70<  <3.68 -3.40<  <-1.70 -83.4 cm-75.2 cm75.2 cm83.4 cm320 cm0 cm 4.2 cm 17.2 cm 15.4 cm 28.4 cm

5. Silicon Sensors Silicon strip detectors 300  m thick Inner sensors 512 strips per side 13-50mm  250  m per strip Outer sensors 256 strips per side 24-42mm  500  m per strip Readout lines run over own strip only reducing crosstalk 13cm Bonding pads

6. Hybrids VA preamplifier chips Low noise High gain Radiation hard (0.35  m AMS Technology) 128 channels per chip Dynamic range of 0-20 MIPS 8 chips per inner hybrid 4 chips per outer hybrid

7. FMD Readout  8 / 4 FMD Module ON DETECTOR IN COUNTING ROOM VA 1 ring: 10/20 modules 2 Digitizers 1 RCU per ring system Full FMD: 70 modules 10 Digitizers 3 RCU’s VA control and biases VA control and biases TTC-RX BOARD CTRL FMD Digitizer ALTRO (16 ch) ALTRO (16 ch) ALTRO (16 ch) ALTRO (16 ch) ALTRO (16 ch) ALTRO (16 ch) CONTROL Local Monitor and Control BOARD controller Bus controller ( conf. & R/O ) DCS int. (Ethernet) DAQ int. (DDL-SIU) Trigger int. (TTC-rx) Data Proc. and Memory DCS DDL RCU Front-end bus  3 m Front-end bus  3 m  40 Control Network (I 2 C-serial link) Control Network (I 2 C-serial link) Trigger L0 NEAR PATCH PANEL Analog serial link (10 MHz)  0.5 m Analog serial link (10 MHz)  0.5 m  5 / 10

8. Prototype Module Prototype inner detector module built Hybrids glued to sensors with thin spacers Readout pads connected to silicon at periphery of hybrid

9. Noise Estimate Main contribution to noise is from electronics+input capacitance and noise from bias resistors Noise SourceShort stripsLong Strips Elect. + cap. 263 e - 309 e - Bias  208 e - I leak 38 e - 72 e - Total 337 e - 387 e - Signal (1 MIP)22000 e - Signal/Noise6557 Inner Sensor Noise Estimate

10. Test Beam Results Tested prototype with high energy electron beam (680 MeV) Clear signal peak Signal/Noise~60

11. Conclusions FMD prototype module shows excellent signal to noise characteristics (60:1) Hit sharing accounts for most of the particles seen between the MIP peak and the noise peak FMD is on schedule for collecting first day physics at the LHC

12. Hit Sharing

13. Test Beam Results Tested prototype with high energy electron beam (680 MeV) Clear signal peak Signal/Noise~60