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/ψμ+μ-Bg

Bg

GeV/c

μ+

J/ψ

μ-

pt

pt

z

Single particle cut:transverse momentum pt

J/ψμ+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/ψμ+μ-

J/ψμ+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/ψμ+μ- ρ0μ+μ-

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

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