Vector meson study for the CBM experiment at FAIR/GSIAnna Kiseleva GSI Germany, PNPI Russia
Motivation
The muon detection system of CBM
Vector meson identification (ρ0, ω, φ, J/ψ)
The low-mass vector meson problem (soft muons)
acceptance of ρ0 at MUCH
possible solution
preliminary results
Outlook
Dilepton Sources in Heavy-Ion Collisions
Dilepton Sources in Heavy-Ion Collisions
Signatures of the quark-gluon plasma:anomalous suppression of charmonium
In-medium spectral function using penetrating probes
D.Adamova et al., PRL 91 (2003) 042301
Calculations by R. Rapp:
thick dashed line: unmodified rho
thick dashed-dotted line: in-medium dropping rho mass
thick solid line: in-medium spread rho width
Di-electron measurements (CERES/CERN)
Di-electron measurements (CERES/CERN)
5-week-long run in Oct.–Nov. 2003 ~ 4 × 1012 ions delivered in total
In+In 158 AGeV
Di-muon measurements (NA60)Di-muon measurements (NA60)
CBM detector: e+e- setupCBM detector: e+e- setupECALTOF
TRD3TRD2STS
RICH
STS: track and vertex reconstruction RICH: electron identification.TRD: identification of high-energy electronsRPC-TOF: time-of-flight measurement ECAL: electron and photon identification
TRD1
A+A collisions at 10 – 45 AGeV
CBM detector: μ+μ- setupCBM detector: μ+μ- setup
ECALTOFTRD3TRD2
STS
MUCH
TRD1
MUonCHamber system (MUCH)MUonCHamber system (MUCH)
Fe C
5 10 20 30
120 cm
STS
First design study absorbers:
4 Fe + 1 C increasing thickness full thickness ~ 1m Fe
detectors: 2 layers between absorbers 1 – in front of MUCH 2 – behind last absorber
TracksTracks
π-
π+1 central Au+Au event at 25 AGeV beam energy(top view of the STS + MUCH system)
Yields for central Au+Au at 25 AGeV
Yields for central Au+Au at 25 AGeV
JJ//(3095 (3095 MeV)MeV)
00
(770 (770 MeV)MeV)
(782 (782 MeV)MeV)
(1020 (1020 MeV)MeV)
++
(140 (140 MeV)MeV)
--
(140 (140 MeV)MeV)
1.95×10-5 23 38 1.28 332 368
6%4.6×10-
5 9×10-5 2.9×10-
4 — —
~1×10-6 ~1×10-3 3.4×10-
3
3.7×10-
4 332 368
multiplicity
branching ratio of channel
per event
Cuts for background suppression
Cuts for background suppression
J/ψ➙μ+μ-Bg
Bg
GeV/c
μ+
J/ψ
μ-
pt
pt
z
Single particle cut:transverse momentum pt
J/ψ➙μ+μ-
p+
➙
p-
➙
Bg
Pair cuts:1. opening angle
μ+
J/ψ
μ-
z
º
2. scalar product
Bg
(GeV/c)2
μ+
J/ψ
μ-
z
Cuts for background suppression
Cuts for background suppression
p+
➙
p-
➙
p+•➙ p-
➙
J/ψ➙μ+μ-
J/ψ➙μ+μ-
p+
➙
p-
➙
Comparison of J/ψ to ρ0 Comparison of J/ψ to ρ0
ρ0
Bg
Bg
Bg
opening angle (°) transverse momentum (GeV/c) scalar product (GeV/c)2
J/ψ
J/ψ➙μ+μ- ρ0➙μ+μ-
Invariant mass spectraInvariant mass spectra
J/ψ
ρ0
ω
φ
opening angle
ptscalar product
J/ψJ/ψ > 12o > 1 [-2.4, -2.05]
ρρ, , ωω, , φφ
> 12o > 0.23 [-0.26, 0.04]
full STS tracking:
STS digitization
track finding
momentum
reconstruction
primary vertex cut
MUCH tracking:
100μm position
resolution
STS track extrapolation
track finding and
matching
J/ψ acceptanceJ/ψ acceptance
4π sts
muchpt> 1GeV/c
1m Fe
sts: > 4 sts hitsmuch: sts + first much1m Fe: behind 1m Fe
ρ0 acceptanceρ0 acceptance
4π sts
much 1m Fe
sts: > 4 sts hitsmuch: sts + first much1m Fe: behind 1m Fe
Momentum distributionMomentum distribution
1.3
much 1m Fe
1.3
Momentum Dependent Track Selection (MDTS)
Momentum Dependent Track Selection (MDTS)
MUCH detector model for MDTS study
MUCH detector model for MDTS study
μ-
π-
μ+
π+
Absorber thickness vs. momentum
Absorber thickness vs. momentum
abso
rber
th
ickn
ess,
cm
μ+, μ- π+, π-
Application: preliminary resultsApplication: preliminary results
μ+
μ-
65 cm
ρ0
~ 1m Fe
2 hard muons
μ-
Application: preliminary resultsApplication: preliminary results
μ+
ρ0
65 cm
~ 1m Fe
1 hard + 1 soft muons
abso
rber
th
ickn
ess,
cm
μ+, μ- π+, π-
Application: preliminary resultsApplication: preliminary results
0.9
65
1.3
100
Application: preliminary resultsApplication: preliminary resultsJ.Vassiliev
2 hard muons 1 soft + 1 hard muon
full STS and MUCH tracking
ρ0 acceptanceρ0 acceptanceJ.Vassiliev
2 hard muons
1 soft + 1 hard muon
2.231
2.477
2.234
OutlookOutlook
Study of different absorber materials, for
example tungsten (W)
Tuning of momentum dependent muon
identification
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