1 / 35

Participation in the HADES experiment

This overview discusses the participation in the HADES experiment, focusing on the construction of a new TOF wall based on RPCs and the analysis of lepton selection. It provides details on the current responsibilities of the HADES RPC group and highlights the activities and achievements of the LIP-HADES group.

yvonnek
Download Presentation

Participation in the HADES experiment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Sixth framework programme Participation in the HADES experiment from construction of a new TOF wall based on RPCs to lepton selection analysis A. Blanco for the LIP-HADES group Activities Overview with the LIP International Advisory Committee Lisbon 27-04-2015

  2. HADES RPC Group Current responsibilities Former members • USC • D. Belver • P. Cabanelas • E. Castro J.A. Garzón • M. Zapata • D. González • GSI • W. Koenig • TU Darmstadt • G. Kornakov • 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 Calibration Software • IFIC-Valencia • J. Diaz • A. Gil Physics analysis Electronics & LV

  3. HADESHigh Acceptance DiElectron Spectrometer Study of “emissivity” and hadron properties in dense and cold nuclear matter, detected via e+ e- pairs (dielectrons) and strange hadrons, produced in proton , pionand heavy ioninduded reactions in a 1-3.5 GeV. Explore this region of the phase-space, still poorly known. Compressed matter at low T Heating Compression

  4. HADESHigh Acceptance DiElectron Spectrometer Study of “emissivity” and hadron properties in dense and cold nuclear matter, detected via e+ e- pairs (dielectrons) and strange hadrons, produced in proton , pionand heavy ioninduded reactions in a 1-3.5 GeV. Spectrometer with high invariant mass resolution and high rate capability. Installed at SIS18, GSI, Darmstadt. http://www-hades.gsi.de/ Project Launched in late 1994 6 years R&D and construction First production run in 2002 International collaboration of 19 institutions from 10 European countries.  Cyprus, Czech Rep., France, Germany, Italy, Poland, Portugal, Russia, Slovakia, Spain.

  5. Hexagonal geometry with 6 identical “sectors”

  6. HADES results on dielectron production Strong dilepton enhancement over hadronic cocktails, also measured by the DLS experiment “DLS Puzzle”

  7. Main contributions from LIP team Hardware Design, R&D and construction of a new TOF detector based on RPCs for the low polar angles. Physics analysis New selection method for leptons, based on neural networks In the frame work of the spectrometer upgrade

  8. Main contributions from LIP team Hardware Design, R&D and construction of a new TOF detector based on RPCs for the low polar angles. Physics analysis New selection method for leptons, based on neural networks In the frame work of the spectrometer upgrade

  9. Requirements of new TOF • Multi-hit capability hit-loss probability below 20% • Minimum 150 channels / sector x effective cluster size • Timing 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 kHz / cm2 in some areas • Not so easy for continuous beam • Efficiencyabove 95% for single hits • In principle no problem, except for geometric coverage • Area8/6 m2 / sector • Fastno long R&D time available.

  10. C+C Mind heavy nuclei colisions (very high multiplicity) Multiplicity/sector Lots of particles (up to ~40/sector) <n> ~ 15 Multiplicity. Radial distribution OneAu + Au collision from Hgeant simulation package => high detector granularity

  11. Requirements of new TOF • Multi-hit capability hit-loss probability below 20% • Minimum 150 channels / sector x effective cluster size • Timing 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 kHz / cm2 in some areas • Not so easy for continuous beam • Efficiencyabove 95% for single hits • In principle no problem, except for geometric coverage • Area8/6 m2 / sector • Fastno long R&D time available.

  12. Adopted solution => HADES cells • 0.27 mm  4 gaps • minimum for good efficiency • Aluminum and glass 2mm electrods • minimize amount of glass for maximum rate capability • try to keep good mechanics • Heat-tolerant materials Fully shielded Spring-loaded pressure plate Aluminium Glass HV & readout in the center

  13. rows Final design 2 layers of individual cells with partial overlap • 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

  14. Readout scheme t1 t2 FEE T = (t1 + t2)/2 X = t1 – t2

  15. FEE electronics t1 t2 4 channels 3GHz amp + timing comparator + QtoWidth conversion FEE based on Philips BGM1013 [TNS 57 vol 5 2010, 2848] Support motherboard (mechanics, services, signal routing)

  16. Time frame Prototype, 2005 Concept validation, 2003 Final prototype, 2007 FCT financial support Construction, 2008-09 Final test, 2009 Instalation, 2010 EU + FCT financial support

  17. Ready for production beam after commissioning with Au+Au 2 AGeV, 2011

  18. First production run with the RPC, operation relies completely on LIP team !! Data recorded, compared with previous beam times Very successful DAQ upgrade

  19. Operation performanceAu+Au 1.23 AGeV: HV currents Stable operation during whole beam time at constant settings: HV, thresholds and gas flow. Quite smooth operation !! G. Kornakov, XII Workshop on Resistive Plate Chambers, Beijing, 2014

  20. t1 t2 t’1 t’2 Operation performance Au+Au 1.23 AGeV: Intrinsic time resolution Overlapped cells [2013 JINST 8 P01004] <t> = 64 ps 64 Time resolution (ps) S1 S2 S3 S4 S5 S6 Time difference T = (t1+t2)/2 – (t’1+t’2)/2 Time resolution σt=σ(T)/√2 RPC row t (ps) <t> = 64 ps for all particles and area, stable in the whole beam time [2014 JINST 9 C11015] Time resolution (ps) Day of the Year 2012

  21. Operation performance Au+Au 1.23 AGeV: Intrinsic time resolution Impact of event multiplicity on time resolution [2014 JINST 9 C11015] Time resolution degradation (ps) Hits/sector/event Excellent multihittiming resolution only a few ps of degradation thanks to the innovative concept adopted: individually shielded RPC

  22. Operation performance Au+Au 1.23 AGeV: Intrinsic time resolution Impact of event multiplicity on time resolution [2014 JINST 9 C11015] RPC electrically shielded Time resolution degradation (ps) Hits/sector/event Excellent multihittiming resolution only a few ps of degradation thanks to the innovative concept adopted: individually shielded RPC

  23. Operation performance Au+Au 1.23 AGeV: System time resolution [2014 JINST 9 C11015] <t> e+e- = 81 ps Time resolution (ps) Momentum x Polarity (MeV/c) Besides the intrinsic resolution of the RPC other sources such as the diamond START detector, length of the trace and multiple scattering are also present contributing witharound 45 ps.

  24. Operation performance Au+Au 1.23 AGeV: PID plot Very good particle identification in a wide momentum range Reconstructed mass distribution with very low background contamination. [2014 JINST 9 C11015]  - + k+ p k- Momentum/z x Polarity [GeV/c] Mass x polarity [MeV/c2] K- peak is clearly visible, which is a very demanding test on the apparatus time response as well as granularity due to their extreme rarity (K- is produced at sub-threshold energy): about one per 10000 anti-pions

  25. MDC IV Shower RPC ? MDC III MDC II MDC I target Operation performance Au+Au 1.23 AGeV: Efficiency Request a valid hit in shower + outer MDC Double layer structure of the RPC visible X (mm) Y (mm) G. Kornakov, XII Workshop on Resistive Plate Chambers, Beijing, 2014

  26. Operation performance Au+Au 1.23 AGeV: Efficiency C1 C2 C3 0.99 0.94 Efficiency  min = int* ext max = (1-(1- int)2)* ext int = 2 - max/ min = 2-0.99/0.94  single cell = 0.95 Taking into account that the almost half of area is covered by two cell => <> = 0.97 Efficiency [2014 JINST 9 C11015] Y (mm)

  27. Main contributions from LIP team Hardware Design, R&D and construction of a new TOF detector based on RPCs for the low polar angles. Physics analysis New selection method for leptons, based on neural networks In the frame work of the spectrometer upgrade

  28. Flowchart of the method for the PID of leptons Physics analysis Au+Au 1.23 AGeV: Lepton selection PID variables PID variables Signal Sample (lepton tracks) Background Sample (hadron tracks) multivariate input Dynamic Neural Network (NN) Multidimensional parame trisation:all correlations are properly taken into account single network output (per track) O1 Network Cut Rejected Tracks Accepted Tracks

  29. Physics analysis Au+Au 1.23 AGeV: Lepton selection. Values of O1 (NN output) close to 1 indicate tracks which are kinematically similar to the simulated leptons (signal sample used to train the NN). O1 O1 (q x p) / 5 MeV (q x p) / 5 MeV With such a conservative cut one is able to achieve an impressive lepton purity of 97%, while keeping a resonable lepton efficiency of 75%.

  30. Physics analysis Au+Au 1.23 AGeV: Lepton selection. O1 < 0.3 background O1 > 0.3 signal All Tracks  RPC 7% of the RPC tracks (q x p) / 5 MeV (q x p) / 5 MeV (q x p) / 5 MeV  TOF 24% of the TOF tracks (q x p) / 5 MeV (q x p) / 5 MeV (q x p) / 5 MeV The selection of electrons and positrons is evident

  31. Physics analysis Au+Au 1.23 AGeV: Lepton selection. Mass spectrum Combinatorial and physical ( -> e+e-) backgrounds are subtracted Very Preliminar e+e- Counts / 10 Mev / c2 Mee [MeV/c2]

  32. Recently in 2014, the RPC-TOF wall was used in a pion beam during 4 weeks, initiating the elementary collisions program. The RPC-TOF wall performed satisfactorily confirming its reliability.

  33. LIP-HADES Future • Operation of the RPC-TOF (relies completely on LIP team)and participation on the next data taken periods • Optimization of the RPC-TOF wall. • Improve / create some useful tools for: monitoring, calibration, fast detection of anomalies, intrinsic performance calculation and producing of the RPC-TOF wall efficiency matrix. • Studies of the double hit rejection capability and optimization of the digitizer. • Physics case • Continue with the determination of the e+ e- mass spectrum. • Strangeness studies, the focus will be on the production rate of strange particles (in particular K- particles) in Au+Au collisions. To pursue this endeavour financial support has been requested in last PTC call. PTDC/FIS-NUC/3731/2014

  34. HADES Future HADES will operate in the new accelerator SIS100 at the future FAIR to complete the dielectron data up to 8 AGeV. HADES at SIS100 One should note that, in the energy range, 2-40 AGeV no dieletron data exist so far, this is complete terra incognita for dielectron measurements.

  35. Conclusion • The HADES spectrometer was upgraded and had a very successful data taking with the Au-Au system thanks partially to the new RPC-TOF. • The new RPC TOF Wall performed flawlessly, in specs, and showing a robust multihit performance. • LIP is contributing with one of the two independent analyses of the Hades Au channel. • The new lepton identification method introduced by LIP, based on a Dynamic Neural Network, proved to be the most efficient one in the selection of electrons and positrons from data.

More Related