Upgrade Letter of Intent High Level Trigger Thorsten Kollegger ALICE | Offline Week | Requirements Focus of ALICE upgrade on physics probes requiring high statistics: sample 10 nb -1 Online System Requirements Sample full 50kHz Pb-Pb interaction rate (current limit at ~500Hz, factor 100 increase) ~1.1 TByte/s detector readout However: storage bandwidth limited to ~20 GByte/s many physics probes have low S/B: classical trigger/event filter approach not efficient 2ALICE | Offline Week | | Thorsten Kollegger 3 Main physics topics, at the LHC uniquely accessible with the ALICE detector: measurement of heavy-flavour transport parameters: diffusion coefficient azimuthal anisotropy and R AA in-medium thermalization and hadronization meson-baryon mass dependence of energy loss R AA study of QGP properties via transport coefficients ( /s, q) J/ , , and c states down to zero p t in wide rapidity range yields and transverse momentum spectra R AA, elliptic flow density dependence central vs. forward production statistical hadronization vs. dissociation/recombination Physics Motivation Slide from Karel Safarik ALICE | Offline Week | | Thorsten Kollegger 4 measurement of low-mass and low-p t di-leptons chiral symmetry restoration vector-meson spectral function disappearance of vacuum condensate and generation of hadron masses QGP thermal radiation low-mass di-lepton continuum space-time evolution of the QGP radial and elliptic flow of emitted radiation Jet quenching and fragmentation jet energy recuperation at very low p t heavy-flavour tagged jets, gluon vs. quark induced jets heavy-flavour produced in fragmentation particle identified fragmentation functions Heavy-nuclear states high statistics mass-4 and -5 (anti-)hypernuclei search for H-dibaryon, n bound state, etc. Physics Motivation ALICE | Offline Week | | Thorsten Kollegger Slide from Karel Safarik Why not triggering? 5 Triggering on D 0, D s and c (p T >2 Gev/c) ~ 36 rate... Slide from Luciano Musa ALICE | Offline Week | | Thorsten Kollegger Strategy Data reduction by (partial) online reconstruction and compression Store only reconstruction results, discard raw data Demonstrated with TPC clustering since Pb-Pb 2011 Optimized data structures for lossless compression Algorithms designed to allow for offline reconstruction passes with improved calibrations Implies much tighter coupling between online and offline reconstruction software 6ALICE | Offline Week | | Thorsten Kollegger Event Size Expected data sizes for minimum bias Pb-Pb collisions at full LHC energy 7 Detector Event Size (MByte) After Zero Suppression After Data Compression TPC TRD ITS Others Total ALICE | Offline Week | | Thorsten Kollegger TPC Data Reduction First steps up to clustering on FEE/FPNs (RORC FPGA) Further steps require full event reconstruction on EPNs, pattern recognition requires only coarse online calibration 8 Data Format Data Reduction Factor Event Size (MByte) Raw Data1700 FEEZero Suppression3520 HLT Clustering & Compression5-7~3 Remove clusters not associated to relevant tracks 21.5 Data format optimization2-3 10 Byte Float to Fixed-Point convertion, size according to detector resolution TPC Data Reduction ALICE | Offline Week | | Thorsten Kollegger9 Lossless data compression with Huffman code (entropy encoding) Data members transformed to increase performance: e.g. Padrow Number => row(i) = row(i) row(i-1) Entropy reduced from ~6 to 1.1 ALICE | Offline Week | | Thorsten Kollegger10 TPC Data Reduction Overall data size to tape reduced by factor 4.3 Used in Pb+Pb 2011, p+p standard ALICE data format Further reduction possible by transforming pad, time coordinates ALICE | Offline Week | | Thorsten Kollegger11 TPC Data Reduction First steps up to clustering on FEE/FPNs (RORC FPGA) Further steps require full event reconstruction on EPNs, pattern recognition requires only coarse online calibration 12 Data Format Data Reduction Factor Event Size (MByte) Raw Data1700 FEEZero Suppression3520 HLT Clustering & Compression5-7~3 Remove clusters not associated to relevant tracks 21.5 Data format optimization2-3