Recent results of HADES MotivationRemarks Dielectron analysis strategy Preliminary results C C 2 AGe

1
Recent results of HADESMotivation/RemarksDielec
tron analysis strategyPreliminary resultsCC 2
AGeVCC 1AGeVpp 2.2 GeVOutlook

• Joachim Stroth, Univ. Frankfurt, for the HADES
  collaboration

2
Motivation

• Probe the electromagnetic structure of hot and
  dense nuclear matter in the time-like region!
• What is the relevant excitation spectrum as the
  matter density increases?
• Where are the limits of hadronic existence?

W. Weise et al.
3
The case of moderate beam energies

• Final state (heavy ion collision _at_ 1-2 AGeV)
• 200 charged particles
• approximately 10 pions, baryon dominated
• little strangeness
• Production of vector mesons below threshold
• co-operative process
• production confined to high density phase
• One vector meson decaying into a lepton pair per
  1-10 Million reactions
• Increase of baryon density
• Dt (3 gt r/r0 gt 2) 15 fm/c
• comparatively long life-time ..
• .. at moderate densities

r/r0
15 fm/c
4
Probing the interior of compressed matter
?
n
?
p
p
?
?
K
?
5
The DLS results

• The yield (M ? 200MeV/c2) of the new data exceeds
  the old data set by a factor of 7 (CaCa).
• The shape (0.05 ? M ? 0.35) can be explained by
  Dalitz decays of p0 and h if cross sections are
  scaled appropriately but in contradiction with
  TAPS measurement...

6
Recent theoretical interpretations
Strong/weak (s/w) r - N(1535) coupling
Calculation C. Fuchs et al. Phys. Rev. C67
025202(2003)
7
Neutral meson multiplicities in event generators
here UrQMD Pluto

• Pluto thermal fireball blast.
• UrQMD difference between 'cascade' and 'EOS'
  because of different
• density profiles.

8
High Acceptance Dielectron Spectrometer

• Low-mass vector mesons (r, w, f)
• Detected via electron pair reconstruction
  (penetrating probes).
• Spectrometer with high invariant mass resolution
  and high rate capability.
• Utilises dedicated second level trigger
  processors to select rare events before mass
  storing.
• Installed at the SIS18, GSI Darmstadt

Project launched in late 19946 years RD and
construction.
First production run in 2002
9
Spectrometer concept

• Geometry
• Full azimuth , polar angles 18o - 85o
• Pair acceptance ? 0.35
• About 80.000 detector channels
• Fast particle identification
• RICH CsI solid photo cathode, No? 80, C4F10
  radiator
• TOF (Scintillator rods)
• TOFino (Scintillator paddles) temporary
  solution, RPC in future
• 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
10
The HADES set-up at GSI
11
Low mass tracking system

• 33 m2 multi-wire drift chambers
• Helium based counting gas
• Aluminum cathode/field wires
• 27000 cells

x/X0 ? 5 10-4
12
Particle ID with the tracking chambers
Jochen Markert ,Univ. Frankfurt

• Correct time-above-threshold for track topology.
• Simulation (Garfield)
• Use tracking information
• Will be exploited for
• Track matching
• Close pair rejection

Dt2 dE/dx Corr.
13
Experimental runs

• November 2001 commissioning run target 5
  
• CC 2 AGeV LVL1 triggered events (Mch.gt3)
  45 Mevents
• CC 1 AGeV LVL1 trigger
  7.3 Mevents
• full coverage with inner MDC chambers (Dp/p ? 10
  at 0.7 GeV/c)
• November 2002 CC 2 AGeV, commissioning and
  physics runs
• target 2 x 2.5, 56 LVL1 trigger 44 LVL2
  trigger 220 Mevents
• 6 outer drift chambers (MDC) in 4 sectors
• October 2003 pp commissioning run (1 GeV, 2
  GeV)
• full coverage with outer MDC III (4 MDC IV) (Dp/p
  ? 1.5 at 0.7 GeV/c)
• February 2004 pp 2GeV production run
• target 5 cm l-H2 400 Mevents
• August 2004 CC 1AGeV production run
• 3x1.5 target, 56 LVL1 trigger 44 LVL2
  trigger 650 Mevents

14
Pion spectra (12C12C 2 AGeV)
two temperature fit

• data in good agreement with TAPS/KaoS results!

15
K0 reconstruction (12C12C 2 AGeV)
Peter Zumbruch ,GSI

• 2000 Kaons found in
• 45 Million events.

16
Fast 2nd level trigger
up to 20 kHz LVL1Fast multiplicity trigger
full event information digitised.
on-line selection of electron candidates
Suppression 10 - 100
LVL2 triggered events are transported to mass
storage
17
On-line off-line comparison

• Trigger condition used in November 2002 run
• At least one good electron candidate
• Ring matched with META hit
• Data rate reduced by 92
• Pair enhancement by factor of ? 9
• Single lepton efficiency of IPUs matching ?
  62(pairs 82)

No bias on data
18
LVL2 trigger and Data taking capabilityin
November 2002
7.5 KHz(220 Mevents)
44
56
19
Lepton candidate selection

• Events with lepton multiplicity ? 1 in LVL1
  triggered events 1.2
• Require META and RICH signal (LVL2)
• matching with fully reconstructed tracks

cut on b
20
Signal Evaluation in RICH
Ring pattern on the Rich pad plane.

• Ring properties
• Pattern matrix amplitude hit pad distribution
• Pattern geometry ring centroid
• Number of fired pads in pattern
• Average charge collected in pattern

Non strong signature for double rings
21
Data CC_at_2AGeV Nov02
No Efficiency / Acceptance Correction
preliminary
22

• New Analysis for November 2002 data

Ongoing HADES collaboration meting in DUBNA next
week
23
Particle-ID Hard Cuts - CC_at_2AGeV

• Hard cuts (HC)
• Ring quality cut
• 3? window on ß
• Momentum dependent cut on shower signature

e-
simulation UrQMD data Nov02
HC1
HC2
HC3
agreement with in 25!
yield reduction
e
simulation UrQMD data Nov02
simulation UrQMD data Nov02
simulation UrQMD data Nov02
counts / 1 MeV / coll.
HC1
HC2
HC3
cut number
qp MeV/c
24
Purity and Efficiency - Hard Cuts
simulation UrQMD
simulation UrQMD
inner tracking
outer tracking
qp MeV/c
qp MeV/c
no problem with hadron fakes!
25
Pluto Generator for Dielectron Cocktail

• Pluto Generator
• agreement with UrQMD (pions, etas)
• all dielectron channel included
• fast event generation
• only stable particles in the output

?0
counts
UrQMD Pluto

• HADES acceptance filter available
• Single track acceptance matrix (p,q,f)
• Plus opening angle cut

plab
UrQMD Pluto
counts
?
Event generator
Detector response
Transport
Acceptance filter
Reconstr. efficiency
plab
26
Combinatorial background
?

• decay products of ?0 (single or many!)
• ?0 Dalitz decays
• Pair Conversion of photons from ?0
• 95 of ee- with ?ee- lt 50 !!

?0

• Combinatorial background (CB)
• e and e- comming from different reactions
• CB-Nee Ne-e- or CB
• Signal
• S- Nee- - CB-

27
Rejection strategy (Pairs)
Relative suppression
META
B-field
MDC I-II
RICH

• Pair cuts
• C0 pairing
• C1 C0 double hit rejection
• Remove tracks with ambiguous detector hit
• C2 C1 opening angle gt 9 deg
• Remove both tracks from sample
• C3 C2 close pair candidate rejection
• Remove track if non-fitted track candidate nearby

Relative suppression
28
Opening angle distribution
Arb. untis
Pair cut 1 applied Normalized to integral

• New analysis
• Pluto simulation

opening angle degree
29
Dielectrons Signal and Combinatorial Background C
C_at_2 AGeV
Simulation Pluto
Nee- S CB
Simulation Pluto
S / CB
arb. units
ee- S all true pairs ?0 Dalitz ? Dalitz ? Dalitz
M MeV/c2
Simulation Pluto
arb. units
Very Good Signal Reconstruction!
M MeV/c2
30
Dielectrons Signal and Combinatorial Background
CC_at_2 AGeV
No Efficiency / Acceptance Correction!
Data Nov02
Data Nov02
Nee- S CB
S / CB
counts / 1 MeV/c2 / coll.
M MeV/c2
M MeV/c2
31
CC 2 AGeV NOV02 (old vs. new analysis)
Thomas Eberl (TUM), Jacek Ottwinowski (Univ.
Krakow), Gosia Sudol (GSI)
preliminary

• New analysis
• Pluto simulation

Experimental (Pluto input) uncertainty in p to h
ratio ? 30-40
No Efficiency / Acceptance Correction! Normalized
to the pion multiplicity
32
CC 2 AGeV NOV02 (old vs. new analysis)
Thomas Eberl (TUM), Jacek Ottwinowski (Univ.
Krakow), Gosia Sudol (GSI)
preliminary

• Old anlysis
• New analysis

Signal to background improved by a factor 2 in
the new analysis
No Efficiency / Acceptance Correction!
33

• Analysis CC 1 AGeV (August 2004)

ongoing
34
Recorded data CC_at_1AGeV
3-segment target
thick target
35
CC _at_ 1AGeV Aug04
No Efficiency / Acceptance Correction
All N- B- 2sqrt(NN--) S- N- - B-
very preliminary
Yield / 1 MeV/c2
M MeV/c2
36

• Analysis pp 2.2 GeV (January 2004)

ongoing
37
Events with 2 charged particles
peak 0.462 ? 0.005
inelastic channels
p p ? p p X (?0)
polar angles
Veto on pp elastic scattering
all pp events
?0
(M?0)20.018
Stefano Spadaro, INFN Catania
38
h reconstruction (hadronic final state)

• 4 identified tracks in the acceptance (pppp-)
• identify pp ? pph ? pppp-p0

Stefano Spadaro, INFN Catania
39
Kinematical fit
Anar Rustamov, GSI

• Vary of each track to minimize

pp missing mass resolution 2.4
40

• (Future) upgrades

Forward hodoscope RPC DAQ Beam line
41
TOFINO replacement by RPC

• TOFINO
• time-of-flight between 18o-45o
• 4 paddles per sector only
• limited resolution (250 ps)
• insufficient granularity for HI

42
RPC design criteria

• operational parameter matched to HADES overall
  performance
• granularity double-hit probability below 20
• resolution 100 ps (s) or better
• rate capability up to 1 kHz/cm2 (in some areas)
• efficiency above 95 for single hits
• concept of the design
• shielded single cells
• 4 gaps with commercial low-resistivity glass
• common gas box sector-wise
• customized read-out

43
HADES collaboration
G.Agakishiev7, C.Agodi2, H.Alvarez-Pol19,
A.Balanda5, R.Bassini10, G.Bellia2,3, D.Belver19,
J.Bielcik6, A.Blanco4, M.Böhmer14, C.Boiano10,
A.Bortolotti10, J.Boyard16, S.Brambilla10,
P.Braun-Munzinger6, P.Cabanelas19, S.Chernenko7,
T.Christ14, R.Coniglione2, M.Dahlinger6,
J.Díaz20, R.Djeridi9, F.Dohrmann18, I.Durán19,
T.Eberl14, W.Enghardt18, L.Fabbietti14,
O.Fateev7, P.Finocchiaro2, P.Fonte4, J.Friese14,
I.Fröhlich9, J.Garzón19, R.Gernhäuser14,
M.Golubeva12, D.González-Díaz19, E.Grosse18,
F.Guber12, T.Heinz6, T.Hennino16, S.Hlavac1,
J.Hoffmann6, R.Holzmann6, A.Ierusalimov7,
I.Iori10,11, Ivashkin12, M.Jaskula5,
M.Jurkovic14, M.Kajetanowicz5, B.Kämpfer18,
K.Kanaki18, T.Karavicheva12, D.Kirschner9,
I.Koenig6, W.Koenig6, B.Kolb6, U.Kopf6,
R.Kotte18, J.Kotulic-Bunta1, R.Krücken14,
A.Kugler17, W.Kühn9, R.Kulessa5, S.Lang6,
J.Lehnert9, L.Maier14, P.Maier-Komor14,
C.Maiolino2, J.Marín19, J.Markert8, V.Metag9,
N.Montes19, E.Moriniere16, J.Mousa15, M.Münch6,
C.Müntz8, L.Naumann18, R.Novotny9, J.Novotny17,
W.Ott6, J.Otwinowski5, Y.Pachmayer8, V.Pechenov7,
T.Pérez9, J.Pietraszko6, J.Pinhao4, R.Pleskac17,
V.Pospísil17, W.Przygoda5, A.Pullia10,11,
N.Rabin13, B.Ramstein16, S.Riboldi10, J.Ritman9,
P.Rosier16, M.Roy-Stephan16, A.Rustamov6,
A.Sadovsky18, B.Sailer14, P.Salabura5,
P.Sapienza2, A.Schmah6, W.Schön6, C.Schroeder6,
E.Schwab6, P.Senger6, R.Simon6, V.Smolyankin13,
L.Smykov7, S.Spataro2, B.Spruck9, H.Stroebele8,
J.Stroth8,6, C.Sturm6, M.Sudol8,6, V.Tiflov12,
P.Tlusty17, A.Toia9, M.Traxler6, H.Tsertos15,
I.Turzo1, V.Wagner17, W.Walus5, C.Willmott19,
S.Winkler14, M.Wisniowski5, T.Wojcik5,
J.Wüstenfeld8, Y.Zanevsky7, P.Zumbruch6
  1)Institute of Physics, Slovak Academy of
Sciences, 84228 Bratislava, Slovakia 2)Istituto
Nazionale di Fisica Nucleare - Laboratori
Nazionali del Sud, 95125 Catania,
Italy 3)Dipartimento di Fisica e Astronomia,
Università di Catania, 95125, Catania,
Italy 4)LIP-Laboratório de Instrumentação e
Física Experimental de Partículas, Departamento
de Física da Universidade de Coimbra, 3004-516
Coimbra, PORTUGAL. 5)Smoluchowski Institute of
Physics, Jagiellonian University of Cracow, 30059
Cracow, Poland 6)Gesellschaft für
Schwerionenforschung mbH, 64291 Darmstadt,
Germany 7)Joint Institute of Nuclear Research,
141980 Dubna, Russia 8)Institut für Kernphysik,
Johann Wolfgang Goethe-Universität, 60486
Frankfurt, Germany 9)II.Physikalisches Institut,
Justus Liebig Universität Giessen, 35392 Giessen,
Germany 10)Istituto Nazionale di Fisica Nucleare,
Sezione di Milano, 20133 Milano,
Italy 11)Dipartimento di Fisica, Università di
Milano, 20133 Milano, Italy 12)Institute for
Nuclear Research, Russian Academy of Science,
117312 Moscow, Russia 13)Institute of Theoretical
and Experimental Physics, 117218 Moscow,
Russia 14)Physik Department E12, Technische
Universität München, 85748 Garching,
Germany 15)Department of Physics, University of
Cyprus, 1678 Nicosia, Cyprus 16)Institut de
Physique Nucléaire d'Orsay, CNRS/IN2P3, 91406
Orsay Cedex, France 17)Nuclear Physics Institute,
Academy of Sciences of Czech Republic, 25068 Rez,
Czech Republic 18)Institut für Kern- und
Hadronenphysik, Forschungszentrum Rossendorf, PF
510119, 01314 Dresden, Germany 19)Departamento de
Física de Partículas. University of Santiago de
Compostela. 15782 Santiago de Compostela,
Spain 20)Instituto de Física Corpuscular,
Universidad de Valencia-CSIC,46971-Valencia,
Spain
44
The collaboration

• Agakishiev Geydar6, Agodi Clementina2,
  Alvarez-Pol Hector19, Atkin Eduard13, Balanda
  Andrzej4, Bellia Giorgio2,3, Belver Daniel19,
  Böhmer Michael14, Boyard Jean-Louis16, Chernenko
  Sergey6, Christ Tassilo14, Diaz Jose20, Djeridi
  Roukaia8, Dohrmann Frank18, Duràn Ignacio19,
  Eberl Thomas14, Emeljanov Valery13, Fabbietti
  Laura14, Fateev Oleg6, Finocchiaro Paolo2, Friese
  Jürgen14, Fröhlich Ingo8, Garzòn Juan A.19,
  Gernhäuser Roman14, Golubeva Marina11, Gonzàlez
  Diego19, Grosse Eckart18, Guber Fedor11, Hennino
  Thierry16, Hlavac Stanislav1, Hoffmann Jan5,
  Holzmann Romain5, Ierusalimov Alexander6, Iori
  Ileana9,10, Ivashkin11, Jaskula Marcin4, Jurkovic
  Martin14, Kämpfer Burkhard18, Kanaki Kalliopi18,
  Karavicheva Tatiana11, Koenig Ilse5, Koenig
  Wolfgang5, Kolb Burkhard W.5, Kopf Ulrich5, Kotte
  Roland18, Kotulic-Bunta Juraj1, Krücken Reiner14,
  Kugler Andrej17, Kühn Wolfgang8, Kulessa
  Reinhard4, Kurepin Alexei11, Lang Simon5, Lehnert
  Jörg8, Maiolino Cettina2, Marín Jesús19, Markert
  Jochen7, Metag Volker8, Mishin Yuri13, Montes
  Noelia19, Mousa Jehad15, Münch Mathias5, Müntz
  Christian7, Naumann Lothar18, Novotny Rainer8,
  Novotny Jan17, Otwinowski Jacek4, Pachmayer
  Yvonne7, Pechenov Vladimir6, Perez Tiago8,
  Pietraszko Jerzy5, Pleskac Radek17, Pospísil
  Vladimír17, Przygoda Witold4, Rabin Nicolay12,
  Ramstein Beatrice16, Reshetin Andrei11, Ritman
  James8, Roy-Stephan Michele16, Rustamov Anar5,
  Sadovsky Alexander18, Sailer Benjamin14, Salabura
  Piotr4, Sànchez Manuel19, Schmah Alexander5,
  Shileev Kirill11, Simon Reinhard5, Smolyankin
  Vladimir12, Smykov Lev6, Spataro Stefano2, Spruck
  Bjoern8, Stroebele Herbert7, Stroth Joachim7,5,
  Sturm Christian5, Sudol Malgorzata7,5, Tlusty
  Pavel17, Toia Alberica8, Traxler Michael5,
  Tsertos Haralabos15, Volkov Yuri13, Wagner
  Vladimir17, Winkler Sonja14, Wisniowski Marcin4,
  Wojcik Tomasz4, Wüstenfeld Jörn7, Zanevsky Yuri6,
  Zumbruch Peter5

45
The collaboration (Institutes)

• 1) Institute of Physics, Slovak Academy of
  Sciences, 84228 Bratislava, Slovakia
• 2) Istituto Nazionale di Fisica Nucleare -
  Laboratori Nazionali del Sud, 95125 Catania,
  Italy
• 3) Dipartimento di Fisica e Astronomia,
  Università di Catania, 95125, Catania, Italy
• 4) Smoluchowski Institute of Physics,
  Jagiellonian University of Cracow, 30059 Cracow,
  Poland
• 5) Gesellschaft für Schwerionenforschung mbH,
  64291 Darmstadt, Germany
• 6) Joint Institute of Nuclear Research, 141980
  Dubna, Russia
• 7) Institut für Kernphysik, Johann Wolfgang
  Goethe-Universität, 60486 Frankfurt, Germany
• 8) II.Physikalisches Institut, Justus Liebig
  Universität Giessen, 35392 Giessen, Germany
• 9) Istituto Nazionale di Fisica Nucleare, Sezione
  di Milano, 20133 Milano, Italy
• 10) Dipartimento di Fisica, Università di Milano,
  20133 Milano, Italy
• 11) Institute for Nuclear Research, Russian
  Academy of Science, Moscow, 117259 Moscow, Russia
• 12) Institute of Theoretical and Experimental
  Physics, 117218 Moscow, Russia
• 13) Moscow Engineering Physics Institute (State
  University), 115409 Moscow, Russia
• 14) Physik Department E12, Technische Universität
  München, 85748 Garching, Germany
• 15) Department of Physics, University of Cyprus,
  1678 Nicosia, Cyprus
• 16) Institut de Physique Nucléaire d'Orsay,
  CNRS/IN2P3, 91406 Orsay Cedex, France
• 17) Nuclear Physics Institute, Czech Academy of
  Sciences, 5068 Rez, Czech Republic
• 18) Institut für Kern- und Hadronenphysik, FZR,
  PF 510119, 01314 Dresden, Germany
• 19) Departamento de Física de Partículas.
  University of Santiago de Comp.. 15782 Santiago
  de Compostela, Spain

46
Summary

• HADES is fully operational within the design
  specs
• Second level trigger system performs well
• Preliminary results for first production run 12C
  12C 2 AGeV
• Hadronic observables Pion spectra in agreement
  with TAPS, KaoS measurements
• Electron pairs Preliminary spectrum close to
  prediction assuming p0 and h decay
• Systematic difference data/simulation for p0
  reconstruction due to modeling of close tracks
• High resolution tracking available (minor
  optimizations) -gt exclusive channels
• A lot of physics ahead for the coming years
• heavy ion system size dependence
• elementary reactions
• p, p, heavy ion high precision in-medium
  spectroscopy

47
Outlook

• Final spectra after
• .. (Absolute) reconstruction efficiency
  calibration
• Analysis p p data
• Next run in September 2005
• CaCa at 2 AGeV
• Completion outer tracking system in 2005
• Replacement of TOFino system by RPC
• Feasibility studies for HADES at SIS100 (lt8 AGeV)
  ...
• ... and beyond at FAIR