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Soft muon identification. Anna Kiseleva GSI Germany, PNPI Russia. Results of the last collaboration meeting (ρ 0 , ω, φ, J/ψ) The low-mass vector meson problem (soft muons) acceptance of ρ 0 at MUCH possible solution results Absorber study: motivation Outlook.
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Soft muon identification Anna Kiseleva GSI Germany, PNPI Russia • Results of the last collaboration meeting (ρ0, ω, φ, J/ψ) • The low-mass vector meson problem (soft muons) • acceptance of ρ0 at MUCH • possible solution • results • Absorber study: motivation • Outlook
CBM detector: e+e- setup ECAL TRD1 TOF RICH TRD3 TRD2 STS STS: track and vertex reconstruction RICH: electron identification. TRD: identification of high-energy electrons RPC-TOF: time-of-flight measurement ECAL: electron and photon identification
CBM detector: μ+μ- setup ECAL TOF TRD3 TRD1 TRD2 MUCH STS
5 10 20 30 120 cm STS Fe C MUonCHamber system (MUCH) • 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
Tracks 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 multiplicity branching ratio of channel per event
J/ψ ω φ ρ0 Invariant mass spectra • 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 acceptance 4π sts much 1m Fe pt> 1GeV/c sts: > 4 sts hits much: sts + first much 1m Fe: behind 1m Fe
6% 2.599 2% 2.438 2% 2.424 0.3% 2.255 10.5% 2.525 8.5% 2.55 8% 2.525 11% 2.525 Acceptance of RECO ρ0 1 2 3 4 2 hard μμ 1hard + 1soft μμ 1hard + 1soft-soft μμ 2 soft μμ 1+2 1+2+3 1+2+3+4 1+2+4 3000 ρ0➙μ+μ- 5 6 7 8
ρ0 acceptance 4π sts much 1m Fe sts: > 4 sts hits much: sts + first much 1m Fe: behind 1m Fe
Momentum distribution much 1m Fe
MUCH detector model for MDTS study 25 Fe × 5cm p [0.5, 1.5] GeV/c μ- π- μ+ π+
Δabsorber cm MUCH detector model for MDTS study 25 Fe × 5cm p [0.5, 1.5] GeV/c
Absorber thickness vs. momentum π+, π- μ+, μ- absorber thickness, cm absorber thickness, cm
Absorber thickness vs. momentum p = 1 GeV/c counts ● π+, π- ■μ+, μ-
N of hits at the MUCH system: ρ0➙μ+μ- NMUCH hitsμ- 5 μ- 4 3 2 ρ0 μ+ 5 7 NMUCH hitsμ+ 9 11
Type of muon pairs 2 hard muons μ+ ρ0 μ- 65 cm ~ 1m Fe p (GeV/c)
Type of muon pairs 1 hard + 1 soft muons μ+ ρ0 μ- 65 cm ~ 1m Fe p (GeV/c)
Type of muon pairs 1 hard + 1 soft-soft muons μ+ ρ0 μ- 35 65 cm ~ 1m Fe p (GeV/c)
Type of muon pairs 2 soft muons μ+ ρ0 μ- 65 cm ~ 1m Fe p (GeV/c)
MDTS: possible pairs NMUCH hitsμ- 2 hard muons 1hard + 1soft muons 1hard + 1soft-soft muons 2 soft muons NMUCH hitsμ+
ρ0 acceptance 2 hard μμ 1hard + 1soft μμ 1hard + 1soft-soft μμ 2 soft μμ
MDTS: possible pair combinations NMUCH hitsμ- 2 hard muons 1hard + 1soft muons 1hard + 1soft-soft muons 2 soft muons NMUCH hitsμ+
MDTS: possible pair combinations NMUCH hitsμ- 2 hard muons 1hard + 1soft muons 2 soft muons NMUCH hitsμ+
ρ0 acceptance 1 + 2 1 + 2 + 3 2 hard μμ 1hard + 1soft μμ 1hard + 1soft-soft μμ 2 soft μμ 1 + 2 + 3 + 4 1 + 2 + 4
Reconstruction • full STS tracking: • STS digitization • track finding • momentum reconstruction • primary vertex cut • MUCH tracking: • 100μm position resolution • STS track extrapolation • track finding and matching
RECO background 2 hard μμ 1hard + 1soft μμ 1hard + 1soft-soft μμ 2 soft μμ 1+2 1+2+3 1+2+3+4 1+2+4
ω➙μ+μ- : S/B ratio S/B 2 hard μμ 1hard + 1soft μμ 1hard + 1soft-soft μμ 2 soft μμ 1+2 1+2+3 1+2+3+4 1+2+4
Invariant mass spectra 2 hard μμ 2 hard μμ + 1hard + 1soft μμ 2 hard μμ + 1hard + 1soft μμ + 2 soft μμ ■ρ ■ω ■φ ■ρ ■ω ■φ ■ρ ■ω ■φ counts/(events×10GeV/c2) minv (GeV/c2)
Outlook • Tuning of momentum dependent muon identification • Study of different absorber materials, for example tungsten (W)
Absorber study: preliminary results MUCH detector behind 5cm W
Fe Fe Fe Fe Fe W W W W W W Fe Fe Fe Fe W W Fe Fe Fe Hit density of central UrQMD event 5cm
ρ0 parameters opening angle (°) transverse momentum (GeV/c) scalar product (GeV/c)2 ρ0 bg bg ρ0➙μ+μ-