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Transcript of The Experimental Quest for In-Medium Effects Romain Holzmann GSI Helmholtzzentrum für...
The Experimental Quest for In-Medium Effects
Romain Holzmann GSI Helmholtzzentrum für Schwerionenphysik, Darmstadt
at
23rd Indian-Summer School of Physics
and
6th HADES Summer School:
Physics @ FAIR
October 3-7, 2011 in Rez/Prague, Czech Republic
Lecture I: Pedestrian’s approach
Lecture II: Experiments galore
Lecture III: HADES at GSI
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 2
Lecture III:
Investigating dense matter with HADES at GSI:Present and future
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 3
Physics we are after with HADES
(High Acceptance DiElectron Spectrometer)
In very general terms:
Medium modifications of hadrons (e.g. vector mesons) chiral symmetry restoration vs. hadronic effects
enhanced dilepton yields → emissivity of hot & dense hadronic matter in-medium spectral functions
systematic dilepton spectroscopy in AA, pA and A (ρ/ρ0 1-3)
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 4
S. Vogel et al.Phys. Rev. C78(2008) 044909
11
2 GeV
30
Exploring the phase diagram at high μB
Probing nuclear matter at SIS: densities: max/0 2 - 3
temperature: T 50 -100 MeV N resonances become important
Andronic et al., Nucl. Phys. A 837 (2010) 65
Trajectories from Ivanov et al., PRC 73 (2006) 044904
HADES operates here!
UrQMDAu+Au
Rapp & WambachAdv. Nucl. Phys. 25(2000)
thermalmodelat =0
System stays above ground statedensity for 10 - 15 fm/c
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 6
Hadron production & spectroscopy meson and baryon production
coupling of and to N*
pn vs.pp
strangeness production form factors of and
systematic dilepton (and hadron) spectroscopy in pp, pn and p
(ρ/ρ0 = 0)
Physics we are after with HADES
→ needed to model p+A & A+A
(High Acceptance DiElectron Spectrometer)
In very general terms:
Medium modifications of hadrons (e.g. vector mesons) chiral symmetry restoration vs. hadronic effects
enhanced dilepton yields → emissivity of hot & dense hadronic matter in-medium spectral functions
systematic dilepton spectroscopy in AA, pA and A (ρ/ρ0 1-3)
π0 & η prod.in p+p
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture I: 9ECT* Dileptons September 13-17, 2010 R. Holzmann, GSI Darmstadt 9
The HADES detector at GSI
azimuth. symmetry
large coverage: y = 0 - 2
hadron & lepton PID
2% mass resolution
LVL2 lepton trigger
plastic forward wall Physics accessible with HADES:
1. Dielectrons in NN: p+p and n+p2. Dielectrons in HI: from C+C to Au+Au3. Vector mesons in cold matter: p+Nb4. Strangeness production: p+p, p+A, A+A5. Pion-induced reactions: (2012-2016)6. SIS100: (>2017)
/ RPC
Technical paper:G. Agakishiev et al. Eur. Phys. J. A41, 243 (2009)General documentation:http://www-hades.gsi.de
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 10
HADES at SIS18
Unilac
SIS18
ESR
HADES
π production target
Measure its:velocity β :momentum p : energy loss in matter dE/dx:Cherenkov (or transition) radiation:calorimetry ► total energy E
This needs a sophisticated detector, e.g. HADES
How to identify a particle?
p = m ∙ βc ►mass
B
A primer for theorists
►Z►e- vs. hadrons
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 12
Detector components
“RICH” (electron ID, hadron-blind)
“TOF”()
“Pre-Shower” (electron ID)“MDC” (tracking, )
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 14
Technical layout of HADES
Pre-S
hower
TOF
outer MDC
RPC
He pipe
Start + target
Cryostat
beam
outer MDC
inner MDC
B field region
inner MDC
RICH readout
HADES caveHADES sector
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 15
The RICH: a hadron-blind detector
hadron-blind, but...
e+
e-
0
~ 15.20
20% 0 Dalitz
e+
e- ~ 2.20
60% γ conversion
► use segmented target
γ > 18
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 16
Segmented target
Example: 3.5 GeV p+Nb
93Nb material 12 pellets of Ø = 1.25 mm Δz = 4.5 mm 2.8% interaction prob.
~ 55 mm
beam
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture I: 17
IPN Orsay
FZR
LHE Dubna
GSI
wire planes:10o,-20o,0o,0o,20o,-10o
ORSAY plane
Tracking: the Multiwire Drift Chambers
4 MDC/sector
total 33 m2 area, 27000 cells
y<0.1 mm resolution
Ar-iC4H10 [60-40] gas
and low-Z material
Layer Width/m Height Area[m 2̂]I 76,7 75,5 0,34II 90,5 88,3 0,49III 180,5 178,0 1,88IV 222,4 219,9 2,83
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 18
Tracking: superconducting toroidal magnet
Bmax = 0.8 Tesla (mid-plane)
bending power = 0.36 Tm
(typically operated at
70% - 90% of max. field)
field map + tracking planes
Runge-Kutta track fit
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 20
Electron/positron identification
ee--
e-
e+
velocity vs. momentum
+ +
RICH patternMDC hit finder &
hit/track matching Pre-Shower condition
Momentum * charge [MeV/C]
DataMonte Carlo
e- e+
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 21
Lepton pair reconstruction
21)2/sin(2 ppM inv
RICH rings
lepton/baryon
p1
ee++
e-
p2
Pair reconstruction
0e-
e+
e-
e+
0 e-
e+
uncorrelated pairs
Combinatorial backgroundsubtraction
eeee NN2CB
From: like-sign pairsor event mixing
Signal:
S+-= Ne+e- - CB+-
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture I: 23
The HADES Collaboration on tour
Cyprus:Department of Physics, University of Cyprus
Czech Republic:Nuclear Physics Institute, Academy of Sciences of Czech Republic
France:IPN (UMR 8608), Université Paris Sud
Germany:GSI, DarmstadtFZ Dresden-RossendorfIKF, Goethe-Universität FrankfurtII.PI, Justus Liebig Universität GiessenPD E12, Technische Universität München
Italy:Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del SudIstituto Nazionale di Fisica Nucleare, Sezione di Milano
Poland:Smoluchowski Institute of Physics, Jagiellonian University of Cracow
Portugal:LIP-Laboratório de Instrumentação e Física Experimental de Partículas 17 institutions
120+ members
Russia:INR, Russian Academy of ScienceJoint Institute of Nuclear ResearchITEP
Spain:Departamento de Física de Partículas, University of Santiago de CompostelaInstituto de Física Corpuscular, Universidad de Valencia-CSIC
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 24
First HADES data: e+e- production in C+C Efficiency-corrected di-electron spectra, normalized to the number of neutral pions:
Ph
ys
.Re
v.
Le
tt 9
8(2
00
7)
05
23
02
Ph
ys
. L
ett
. B
66
3 (
20
08
) 4
3Cocktail generatedwith PLUTO
Checking on DLS: Is there excess e+e- yield? How does the excess evolve with bombarding energy? And with system size? – or – Is there physics beyond free NN?
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 25
1 AGeV C+C: HADES confirms DLS
π0, η acceptance
HADES >> DLS
ππ00→e+e–γHadesHades DLSDLS
mid-rapidity
η→e+e–γ
HadesHades DLSDLS
mid-rapidity
vs.
► HADES fully confirms highly controversial DLS findings in C+C:
Porter et al., PRL 79 (1997) 1229
Agakishiev et al., PLB 690 (2010) 118
HADES
DLS
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture I: 26
e+e- production in 1.756 GeV/u Ar+KCl
Again, strong overshoot above the cocktail of long-lived sources!
First ω peak seen at SIS energies!
► MLVL1(ω) = (6.5 ± 2.8) ·10-3Cocktail oflong-lived sources:π0, η, and ω
~ 40 counts
±20 % sys.
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 27
Tagging quasi-free np reactions in HADES
p+p:Cut View
FW > 7o
d
psp
p
pr
OBE calculationsreproduce pp,but not (yet) np !
d+p: quasi-free np
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 30
Preparing a “reference” for A+A
Compare excess over η in Ar+KClwith excess over η in reference
Definition of a ”reference” based on pp and np data:
x2.5 - 3
η contributions subtracted ! yield normalized to M(π0) ►► Excess over free NN!
Excess dilepton yield in HIC
SPS
RHIC
SIS
Low-mass dilepton excess present at all energies,although quite different processes contribute…
► Excitation function of the dilepton yield still largely unknown: HADES & CBM will provide this information at FAIR.
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture I: 34
Strangeness production in Ar+KCl
HADES has
high mom resolution high acceptance good particle ID vertexing
1.76 GeV/u Ar+KCl
PID based on dE/dx and TOF
→K+K-
Ξ- → Λπ-
TB = 84
PRC 80 (2009) 025209 PRL 103 (2009) 132310PRC 82 (2010) 021901EPJA 44 (2010) etc.
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 40
The Hades upgrade project (2010/11)
Meta detector, < 45 deg.Time res: 350 ps. PreShower pos. res: 1.5 cmLimitation: multihit capability
RPC performance (beam test) Efficiency above 95 % Time res. 50-80 ps Negligible crosstalk < 1%
List of HADES upgrade subprojects:List of HADES upgrade subprojects: RPC - Resistive Plate Chamber FINISHED
Time res. 50-80 ps, high granularity Forward Wall FINISHED
range 0.2 – 7 degrees, centrality, reaction plane DAQ-Upgrade
FINISHED goal 20 kHz for Au+Au LVL1 MDC I rebuild system stability Commissioning
Summer 2011: commissioned with Au beam
1 RPC sector
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture I: 41
Next runs at SIS18: 1.25 GeV/u Au+Au
HADES upgrade nearly completed
new MDC inner tracking plane new RPC timing detectors new and faster readout electronics Forward Wall installed
► Getting ready for Au run 2nd Q 2012
Simulated counts for 4 weeks beam
1.25 GeV Au+Au
Expected pair rates/day
+ plenty of strangeness!
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 42
Experiments with pion beams:The GSI secondary pion beam line
Momentum of the beam particles reconstructed with precision of 0.3%
Tracking in the beam line: silicon strip detector
Diamond in front of the target for background rejection
• Q doublet defines acceptance = 2.3 msr
• Momenta up to 2.8 GeV/c , p/p = 8%• Beam spot at the HADES focal point:
3σx – 2.0 cm, 3σy – 1.8 cm • H1, H2 & H3 for beam momentum reconstruction (fiber/silicon det.)
p/p = 0.3%
7.5o
dispersive plane
Particle production in the HSD transport model
Thermal
Cassing & Bratkovskayacalculations for FAIR
central Au+Au
SIS100
A Photon Calorimeter for HADES
Adding a calorimeter to HADES offers:
• Better lepton ID• Neutral mesons in p+A & A+A• Direct photons in p+A & A+A• Hadron zoo in p+p & π+p
EbaE //
Photon decays:π0 → γγη → γγη’ → γγω → π0γ → γγγ+ Dalitz decays
Neutral meson detection in A+A
large photon combinatorial background small signal/background ratios
needs a high-resolution EM calorimeter
S/B=0.07 %
WA80
S/B=2.7 %
TAPS
0.8 AGeV Au+Au
200 AGeV S+Au
CB-subtracted mγγ spectra
A. Wolf et al.PRL 69 (98) 5281
R. Albrecht et al.PLB 361 (95) 14
100+100 AGeV Au+Au
PHENIX
S/B = 0.2% – 5%
158 AGeV Pb+Pb
WA98
S/B < 0.5%
Eta Dalitz reconstruction in simulation
η → γ e+e- measured in HADES + calorimeter:
► Potentially interesting, but needs to be explored in simulations!
S/B >1
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 48
2017: HADES goes underground
HADESin the CBM cave
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 49
The HADES roadmap: 2012-2018
The present planning foresees:
2012: Au+Au run at 1.25 AGeV (dileptons + strangeness)
2013: first pion beam run (physics goals still being discussed)
2014: Ag+Ag run at 1.65 AGeV (dileptons + strangeness)
2015: another pion beam run ??
2016: move HADES to CBM cave at SIS100
2018: first beams from SIS100 ???
Rez 2011 - The Experimental Quest for In-Medium Effects - R. Holzmann, GSI Lecture III: 51
HADES2 – 8 GeV/u
CBM8 – 45 GeV/u
Conclusions and outlook
Understanding pp, np & πN processes is essential for A+A !!!
In Ar+KCl onset of “medium” effects strong baryonic contribution to e+e-
first observation of vector mesons 2nd focus on strangeness production
Upgraded HADES will investigate heavy systems up to Au+Au πN and πA reactions + strong strangeness program
Move to SIS100 planned for 2016/17 add lead glass calorimeter do physics at 2 – 8 AGeV