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- 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

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

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

Acceptance of RECO ρ0Acceptance of RECO ρ0

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

1 2 3 4

5 6 7 8

3000 ρ0 ➙ μ+ μ-

6%2.599

2%2.438

0.3%2.255

2%2.424

8.5%2.55

11%2.525

10.5%2.525

8%2.525

ρ0 acceptanceρ0 acceptance

4π sts

much 1m Fe

sts: > 4 sts hitsmuch: sts + first much1m Fe: behind 1m Fe

Momentum distributionMomentum distribution

much 1m Fe

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+

25 Fe × 5cm p [0.5, 1.5] GeV/c

MUCH detector model for MDTS study

MUCH detector model for MDTS study

25 Fe × 5cm p [0.5, 1.5] GeV/c

Δabsorber cm

Absorber thickness vs. momentum

Absorber thickness vs. momentum

π+, π- μ+, μ-ab

sorb

er t

hic

knes

s, c

m

abso

rber

th

ickn

ess,

cm

Absorber thickness vs. momentum

Absorber thickness vs. momentum

● π+, π-

■ μ+, μ-

p = 1 GeV/cc

ou

nts

N of hits at the MUCH system: ρ0➙μ+μ-

N of hits at the MUCH system: ρ0➙μ+μ-

1111

9977

55

NMUCH hitsμ+

NM

UC

H h

itsμ

-

μ-

μ+

ρ0

34

5

2

Type of muon pairsType of muon pairs

2 hard muons

μ+

μ-

65 cm

ρ0

~ 1m Fe

p (GeV/c)

Type of muon pairsType of muon pairs

1 hard + 1 soft muons

p (GeV/c)

μ+

μ-

65 cm

ρ0

~ 1m Fe

Type of muon pairsType of muon pairs

1 hard + 1 soft-soft muons

p (GeV/c)

μ+

65 cm

ρ0

~ 1m Fe

μ-

35

Type of muon pairsType of muon pairs

2 soft muons

p (GeV/c)

μ+

μ-

65 cm

ρ0

~ 1m Fe

1hard + 1soft-soft muons

MDTS: possible pairsMDTS: possible pairs

NMUCH hitsμ+

NM

UC

H h

itsμ

-

2 hard muons

1hard + 1soft muons

2 soft muons

ρ0 acceptanceρ0 acceptance2 hard μμ 1hard + 1soft μμ

2 soft μμ1hard + 1soft-soft μμ

MDTS: possible pair combinationsMDTS: possible pair combinations

NMUCH hitsμ+

NM

UC

H h

itsμ

-

1hard + 1soft-soft muons

2 hard muons

1hard + 1soft muons

2 soft muons

MDTS: possible pair combinationsMDTS: possible pair combinations

NMUCH hitsμ+

NM

UC

H h

itsμ

-

2 hard muons

1hard + 1soft muons

2 soft muons

ρ0 acceptanceρ0 acceptance

2 hard μμ

1hard + 1soft μμ

1hard + 1soft-soft μμ

2 soft μμ

1 + 2 1 + 2 + 3

1 + 2 + 41 + 2 + 3 + 4

ReconstructionReconstruction

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 backgroundRECO 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 ratioω ➙ μ+ μ- : S/B ratio

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

S/B

Invariant mass spectraInvariant mass spectra

minv (GeV/c2)

cou

nts

/(ev

ents

×10

GeV

/c2 )

2 hard μμ2 hard μμ

+1hard + 1soft μμ

2 hard μμ+

1hard + 1soft μμ+

2 soft μμ

■ ρ■ ω■ φ

■ ρ■ ω■ φ

■ ρ■ ω■ φ

OutlookOutlook

Tuning of momentum dependent muon

identification

Study of different absorber materials, for

example tungsten (W)

Absorber study: preliminary results

Absorber study: preliminary results

MUCH detectorbehind 5cm W

Hit density of central UrQMD event

Hit density of central UrQMD event

Fe Fe Fe FeFe

W W W WW

Fe Fe Fe FeW

W Fe Fe FeW

5cm

Thank you for your attention!Thank you for your attention!

ρ0 parameters ρ0 parameters

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opening angle (°) transverse momentum (GeV/c) scalar product (GeV/c)2

ρ0➙μ+μ-

ρ0

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