relativistic heavy ions experiment iii strangeness and heavy flavour
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K- + p 0+ K0
0 (S = -1, weak interaction) p+ - (S = -1, weak interaction)
Multiple Strange Particles: (Cascades)
Main Strangeness Carriers in A+A Collisions: K and
s s=
Strangeness Conservation
K0 (ds)K+ (us)
Isospin Symmetry
K- (us) K0 (ds)Isospin Symmetry
(uds) (uds)
>>
>>
If baryon density is high
Multiple Strange Particles from String Fragmentation
M. Bleicher et al.,Phys. Rev. Lett. 88 (2002), 202501
Particle Identification in NA49
dE/dx measured in TPCs Large acceptance Resolution 3-4%
Time-of-flight Mid-rapidity Resolution 60 ps
Example:Pb+Pb @ 40 AGeV
p
dE/d
x
High Voltage-Electrode (100 kV)
Fieldcage
Readout Chamber
Time Projection Chamber: ALICE
Volume: 88 m3
Drifttime 88 s Number of readout
channels: 570132
E-FieldE-Field
510 cm
TPC (ALICE): Working Principle of Readout Chambers
Gas amplification at the anode wires
Induced signal on pads: x/y-coordinates
Drifttime z-coordinates
Signalheight Energy loss of particles Particle identification
beam axis
Strange Particle Reconstruction in NA57
Si Pixels
telesc
ope
target
1 M ch
annels
B
30 cm
5 cm
5 cm
1.4 T
60 cm
Energy Dependence of Particle Ratios
5.1
K+/+
K-/-
/
/
-/
-++/
UrQMD + HSDE.L. Bratkovskaya et al.,PRC 69 (2004), 054907
Statistical hadron gas:P. Braun-Munzinger,J. Cleymans, H. Oeschler, and K. RedlichNucl. Phys. A697 (2002) 902
s = 1
acceptance: pt > 0.2 GeV/cr < 50 m for pt > 1.5 GeV/c
D0 K+ + -
c ~ 124 m
Reconstruction of D-Mesons
Transition Radiation
Produced by charged particles passing the border between two media of different di-electricity constant
Predicted by V.L. Ginzburg and I.M. Frank 1946
Properties: Energyspectrum in keV-region Emissionangle ~1/ (Lorentz-Factor)
Spectrum and yield determined by: Number and distance of borders Thickness and plasma frequency of
materials Velocity of charged particle
() Possible radiators:
Regular foil stack Fiber materials Foam-like materials
measuredspectrum for electrons with 2 GeV/c momentum
Zählgas: Xe/CO2
Driftlänge: 3cm
Transition Radiation Detector
Electron-/pion-discrimination:
e- (p = 5 GeV/c): 10000
- (p = 5 GeV/c): 36
Radiator made of microfibersPolypropylene, 17 m
TRD Setup in ALICE
TRD in numbers: 540 chambers 6 planes 18 sectors
(supermodule) Total area: 736 m2
(3 tennis courts) Gasvolume: 27,2 m3
Resolution (r) 400 m
Number of read out channels: 1.2 106
TRD Supermodule
TPC