Vector meson study for the CBM experiment at FAIR/GSI
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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
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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
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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)
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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)
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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
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CBM detector: μ+μ- setupCBM detector: μ+μ- setup
ECALTOFTRD3TRD2
STS
MUCH
TRD1
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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
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TracksTracks
π-
π+1 central Au+Au event at 25 AGeV beam energy(top view of the STS + MUCH system)
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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
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Cuts for background suppression
Cuts for background suppression
J/ψμ+μ-Bg
Bg
GeV/c
μ+
J/ψ
μ-
pt
pt
z
Single particle cut:transverse momentum pt
J/ψμ+μ-
p+
p-
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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/ψμ+μ-
J/ψμ+μ-
p+
p-
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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/ψμ+μ- ρ0μ+μ-
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Invariant mass spectraInvariant mass spectra
J/ψ
ρ0
ω
φ
opening angle
ptscalar product
J/J/ψψ > 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
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J/ψ acceptanceJ/ψ acceptance
4π sts
muchpt> 1GeV/c
1m Fe
sts: > 4 sts hitsmuch: sts + first much1m Fe: behind 1m Fe
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ρ0 acceptanceρ0 acceptance
4π sts
much 1m Fe
sts: > 4 sts hitsmuch: sts + first much1m Fe: behind 1m Fe
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Momentum distributionMomentum distribution
1.3
much 1m Fe
1.3
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Momentum Dependent Track Selection (MDTS)
Momentum Dependent Track Selection (MDTS)
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MUCH detector model for MDTS study
MUCH detector model for MDTS study
μ-
π-
μ+
π+
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Absorber thickness vs. momentum
Absorber thickness vs. momentum
abso
rber
th
ickn
ess,
cm
μ+, μ- π+, π-
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Application: preliminary resultsApplication: preliminary results
μ+
μ-
65 cm
ρ0
~ 1m Fe
2 hard muons
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μ-
Application: preliminary resultsApplication: preliminary results
μ+
ρ0
65 cm
~ 1m Fe
1 hard + 1 soft muons
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abso
rber
th
ickn
ess,
cm
μ+, μ- π+, π-
Application: preliminary resultsApplication: preliminary results
0.9
65
1.3
100
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Application: preliminary resultsApplication: preliminary resultsJ.Vassiliev
2 hard muons 1 soft + 1 hard muon
full STS and MUCH tracking
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ρ0 acceptanceρ0 acceptanceJ.Vassiliev
2 hard muons
1 soft + 1 hard muon
2.231
2.477
2.234
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OutlookOutlook
Study of different absorber materials, for
example tungsten (W)
Tuning of momentum dependent muon
identification