Participation in the HADES experiment P Fonte for

Participation in the HADES experiment P. Fonte for the HADES RPC group Jornadas LIP 2014 Sixth framework programme

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte HADES RPC Group Current responsibilities GSI • W. Koenig TU Darmstadt • G. Kornakov Calibration LIP • A. Blanco • N. Carolino • O. Cunha • P. Fonte • L. Lopes • A. Pereira • P. Bordalo • C. Franco • S. Ramos • L. Silva • A. Oliveira • C. Silva Maintenance & Operation Participation in the physics analysis • • • USC D. Belver P. Cabanelas E. Castro J. A. Garzón M. Zapata • • IFIC-Valencia J. Diaz

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte

Jornadas LIP 2014 Participation in the HADES experiment Spectrometer concept P. Fonte Geometry § Full azimuth, polar angles 18 o - 85 o § Pair acceptance » 0. 35 § About 80. 000 detector channels Fast particle identification § RICH Cs. I solid photo cathode, No~ 80, C 4 F 10 radiator § TOF (scintillator rods) § RPC-TOF § Pre-Shower 18 pad chambers & lead converters Momentum measurement § ILSE, super conducting toroid Br = 0. 36 Tm § MDC multi-wire drift chamber, single-cell resolution » 100 mm 1 m

Jornadas LIP 2014 Participation in the HADES experiment TOF RPC P. Fonte Shower Magnet MDC IV MDC III MDC II RICH MDC I Hexagonal geometry with 6 identical “sectors”

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte Strong dilepton enhancement over hadronic cocktails

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte Heavy nuclei colisions Lots of particles (up to 30/sector) Au+Au C+C Unevenly distributed radially by a factor ~2 over the inner TOF area

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte RPC design criteria Operational parameter matched to the HADES overall performance § Multi-hit capability hit-loss probability below 20% § Minimum 150 channels/sector effective cluster size § resolution 100 ps ( ) or better § In principle not difficult for a good detector § Potential problems: mechanics, crosstalk (hard to measure). § rate capability up to 1 k. Hz/cm 2 in some areas § Not so easy for almost continuous beam § efficiency above 95% for single hits § In principle no problem, except for geometric coverage § Area ~8/6 m 2/sector § Fast! no long R&D time available

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte Final design 2 layers of individual cells with partial overlap rows § 187 cells/sector distributed in 29 rows and 6 columns, 3 on top and 3 on bottom § 1122 cells total § 124 different detectors with variable width, length and shape no attempt at impedance matching

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte HADES cells § 0. 27 mm 4 gaps § minimum for good efficiency §Aluminum and glass 2 mm electrods § minimize amount of glass for maximum rate capability § try to keep good mechanics § Heat-tolerant materials Fully shielded Aluminium Glass Spring-loaded pressure plate HV & readout in the center

Jornadas LIP 2014 Participation in the HADES experiment Assembly in gas box HV capacitor (~1 cm 2) HV distribution PCB 50 signal Feedthrough PCB Further shielding between feedthrougs P. Fonte

Jornadas LIP 2014 Participation in the HADES experiment Readout scheme t 1 t 2 FEE P. Fonte

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte FEE electronics t 1 t 2 4 channel 3 GHz amp+timing comparator + Qto. Width conversion Support motherboard (mechanics, services, signal routing)

Jornadas LIP 2014 Participation in the HADES experiment TDC and DAQ P. Fonte (by GSI electronics group) TRB (Time Readout Board) 128 multihit TDC channels (CERN’s HPTDC)

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte Time frame Concept validation, 2003 First prototype test, 2005 Final prototype test, 2007 Partially instrumented Fully instrumented

Jornadas LIP 2014 Participation in the HADES experiment Time frame Final tests, 2009 Ready for beam, 2011 P. Fonte

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte Data recorded, compared with previous beamtimes Very successful DAQ upgrade

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte Sub-threshold produced K- clearly visible: robust multihit performance

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte

Jornadas LIP 2014 Participation in the HADES experiment Mind the internal spacers of the RPCs! P. Fonte

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte Motivation ● ● The main goal of the LIP-HADES group is to study the mass properties of hadrons inside a very dense hadronic medium at low temperature This region of the phase-space, which is still poorly known, is explored in Hades through Au+Au collisions at 1. 25 Ge. V/nucleon

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte Motivation ● ● ● Leptons are the ideal probe of the in-medium properties of hadrons: they are not disturbed by secondary interactions due to their lack of strong interaction The final goal is to compare the experimental e+e- (coming from the inmedium hadronic decays) mass spectrum with the predictions of models describing the heavy ion collisions The in-medium properties of the above mentioned mass spectrum are crucial for a better understanding of the mechanism responsible for the mass generation in hadrons

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte Flowchart of the method developed at LIP for the PID of leptons PID variables Signal Sample multivariate input (lepton tracks) Background Sample (hadron tracks) Multidimensional parametrisation: all correlations are properly taken into account Dynamic Neural Network single network output (per track) Network Cut Accepted Tracks Rejected Tracks

Participation in the HADES experiment Jornadas LIP 2014 P. Fonte Velocity distribution as a function of the momentum times polarity (before and after a multidimensional cut in the Neural Network response) All tracks Rejected tracks Accepted tracks The selection of relativistic electrons and positrons is evident ● ● The efficiency and purity of the lepton sample are both above 92% The selection of leptons with a low velocity or a high momentum is made possible by the use of a Neural Network

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte The invariant mass spectrum for dileptons Combinatorial background is subtracted e+e- Preliminary The physical background, e+e-, was removed with the help of a Neural Network

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte Conclusion § The HADES spectrometer was upgraded and had a very successful data taking with the Au-Au system. § The new RPC TOF Wall performed flawlessly, in specs, and showing a robust multihit performance. § There will be another production beamtime this year, either with beam or with the Ag-Ag system. § HADES will be part of the set of experiments of FAIR (the first one to run, actually).

Jornadas LIP 2014 Participation in the HADES experiment P. Fonte