The ALICE Forward Multiplicity Detector from Design to Installation

2 Matter and the Quark Gluon Plasma Heavy Ion Collisions and ALICE The Forward Multiplicity Detector: Motivation, sensors, electronics, tests Offline data analysis: Geometry, simulation, reconstruction analysis Overview

Matter m m m m 0.1m Standard model describes this by matter particles (fermions) and force particles (bosons): quarks leptons (fermions) “force mediators” (bosons)‏ photons: electromagneti c gluons: strong force  Z and W bosons: weak force

4 Forces 4 Gravity Apple falls, moon in orbit, 1/r 2 behaviour Electro-magnetism Light bulb, 1/r 2 behaviour, +/- charge, γ Weak nuclear force Heavier elements, e - mr /r behaviour, Z 0 and W ± Strong nuclear force Quarks in nucleons, nucleons in nuclei, gluons, colour gluons and quarks

QCD and Confinement 5 Quantum Chromo Dynamics (QCD) – theory of strong nuclear force. Quarks and gluons have colour ! Quark-quark-potential If you try to separate two quarks, you will just get two new ones… rV(r) qualitative difference between the q-q and the Coulomb potentials a/r a/r+b£ r Quarks are confined to the nucleons difficult theory – tough to measure

Quark Gluon Plasma (QGP) 6 … the q-q potential is screened and the hadrons dissolve  quark gluon plasma... if you compress the hadronic matter… Confinement: the quarks (and gluons) are confined in white objects (hadrons)‏Confinement: the quarks (and gluons) are confined in white objects (hadrons)‏ Colour cannot be probed directly, but...

Where to find QGP 7 baryon chemical potential Nuclear Matter Matter BBBB T 940 MeV temperature SIS crab nebula neutron stars hadron gas quarkgluonplasma TCTCTCTC early universe RHIC SPS AGS LHC

8 Matter and the Quark Gluon Plasma Heavy Ion Collisions and ALICE The Forward Multiplicity Detector: Motivation, sensors, electronics, tests Offline data analysis: Geometry, simulation, reconstruction analysis Overview

Colliding Heavy Ions 9 Before collision: ~ % speed of light, Lorentz contracted “pancakes” QCD interactions, quark-matter creation, high density & temperature → Phase transition? Re-combine to hadrons (confined), re-scattering Kinetic freeze-out, final state particles Measurable particles

Large Hadron Collider 10 LHC will collide : Pb-Pb at p-p at

A Large Ion Collider Experiment (ALICE) 11 EMCA L TRD TPC HMPID MUON PMDITSTOF T0, V0 PHOS FMD beam beam

Detecting Particles 12 ● Barrel detectors (ITS, TPC, TRD, TOF, HMPID): measure path of particles and identify particles. ● MUON: Direct di-lepton measurements. ● PHOS: Direct photon measurements. ● T0, V0: provide trigger information. ● FMD: Particle multiplicity, event plane, and flow (simulation of central collision)

13 Matter and the Quark Gluon Plasma Heavy Ion Collisions and ALICE The Forward Multiplicity Detector: Motivation, sensors, electronics, tests Offline data analysis: Geometry, simulation, reconstruction analysis Overview

Forward Multiplicity Detector 14 FMD1 FMD2 FMD3Interactionpoint

Why the FMD? (1) 15 FMD measures number of charged particles at low angles - or high Region not covered by other ALICE detectors. Charged particle multiplicity ● Baseline measurement (how much is there) ● 1 st order model discriminator ● Used to select events

Why the FMD? (2) 16 Determine event-plane ª R Used in jet-analysis – study medium effects. Q: How strongly does the QCD matter effect the produced particles? A: (RHIC) Quite a bit!

Why the FMD? (3) 17 Measure azimuthal asymmetry v 2 at small angles Fourier decomposition of dM ch /d' with ' relative to ª R Q: QCD matter have colour? A: (RHIC) yes! Q: is a phase reached? A: (RHIC) yes Q: do we understand it? A: No!

What is the FMD? 18 3 sub-detector: FMD1, 2, & 3 2 types of rings: inner and outer Made of silicon sensors Inners: 20 azimuthal sectors, 512 radial strips Outers: 40 azimuthal sectors, 256 radial strips Total of 51,200 channels

Front-End Electronics 19 Sensor+hybrid(module) Digitiser card (FMDD) ALTRO & I 2 C buses Trigger & timing Ethernet DAQ link Read-out Controller (RCU) & Detector Control System Card (DCSC) Trigger (L0)

Data Path in the FMD 20 ● Sensor register charged particles ● VA1 3 amplifies and serialises analogue signal ● ALTRO digitises analogue signal ● RCU fetch data from ALTRO and pass it to DAQ.

Sensors 21 Manufactured by Hamamatsu Cut from 6” 320μ m thick wafers ● Low leakage current ● High stability ● < 1 ‰ dead channels Pitch: ● Inners: ~250μ m ● Outers: ~500 μ m

Hybrid Cards 22 VA1 3 To/from FMDD Bonds Glued & bonded to sensor Designed and manufactured by IDEAS Hybrid card holds VA1 3 pre-amplifiers VA1 3 : ● Time-tested VIKING family ● Low noise, high gain ● Radiation tolerant ● 128 input channels, serialised into 1 output channel ● Adjustable peaking time ● Calibration pulser – calibrate signal size.

Module Performance 23 Estimates of best signal-to-noise ratio: ● Inners: 59:1 to 65:1 ● Outers: 56:1 to 61:1 Test beam results from ASTRID using IDEAS test system: ● Inners: 57:1 to 63:1 ● Outers: ~ 35:1 All modules tested in laboratory with IDEAS test system.

Digitiser Cards (FMDD) 24 Designed at NBI (based on TPC FEC) Re-use TPC custom ADC - the ALTRO chip Main components: ● 3 ALTRO ADCs ● 1 Board Controller (BC) ● 4 5 channel monitors ● Connections to hybrids ● Bus connection

What does the FMDD do? 25 ● ALTRO: ● Parallel Analogue-to- digital converter ● Multi-event buffer ● Signal processing ● BC: ● Govern communication ● Monitor Temperatures, voltages, currents ● Trigger handling ● Control VA1 3 - incl. read- out, bias, pulser calibration RCU monitors state – turns off card in case of problems.

FMDD Board Controller 26 ● Implemented as Firmware in FPGA ● Developed at NBI – based on TPC BC, but completely re-written ● Allow control of all aspects of R/O, etc. ● Remotely re- programmable

Read-out Controller Unit 27 ● TPC design ● RCU chip: – Trigger handling – Control of FMDD – Monitor FMDD – Read-out ALTROs – Push data to DAQ ● DCSC computer: – Provide control of RCU to Ctrl. Sys. – Provide status info on RCU & FMDD Detectorcontrolsystemcard Datalink Ethernetlink Trigger & timing Embeddedcomputer RCU chip (on back)

Data Acquisition 28 ● Signal from sensor, digitised by ALTRO, read- out and sent to DAQ by RCU. ● DAQ collects sub-event data – write to permanent store ● Special programs analyse online data for pedestals and gains. ● Provide monitor channels

Detector Control System 29 ● Control & monitor FEE, power supplies, cooling. ● FEE control/monitor based on TPC – but revamped for FMD. ● Re-use custom software as much as possible ● Robust design of configuration DB

Test beam results 30 ● Full system test at ASTRID ● 630MeV e - beam c.f. Carsten Søgaard

31 Matter and the Quark Gluon Plasma Heavy Ion Collisions and ALICE The Forward Multiplicity Detector: Motivation, sensors, electronics, tests Offline data analysis: Geometry, simulation, reconstruction analysis Overview

Offline software 32 ● Geometric description ● Simulation of events ● Reconstruction of events ● Analysis

Reconstruction 33 ● Process raw data recorded by DAQ needed. For each strip, do – Pedestal subtraction (pedestals from special DAQ program) – Gain matching (gain from special DAQ pulser program) – Path length correction – Rough multiplicity estimate But that is not enough!

Sharing 34 ● Particles traverse >1 strip → signal shared over 2 (or, less often, more) strips ● Merge signals into single strip ●... but still more to come

# Particle Cuts 35 ● Fit ∑Landau to distribution ● Define cuts based on probability ● Compare to simulation input

Background Correction 36 ● Large contribution from external material ● In some places up to 300% ● Crucial for proper charged particle multiplicity c.f. Hans Hjersing Dalsgaard

Charged Particle Multiplicity Density 37 ● Data processing – Pedestal – Gain – Path length – Sharing – # of particle cuts – Background ● Final charged particle multiplicity c.f. Hans Hjersing Dalsgaard

Event Plane and v 2 38 ● Use ' segments to determine event plane ª R ● Determine event plane resolution R k ● Determine v 2 6% flow input

39 Conclusions & outlook ● Well tested detector ● Good performance – High s/n – Efficiency > 99.5% – < 1‰ dead channels – Stable ● FMD2+3 installed ● FMD3 fully commissioned. ● Offline software ready – Need better understanding of background & cuts ● FMD1 installed in a few days ● FDR2 will see operational FMD2+3 ● Ready for first beam this summer