[PPT] - -meson In-medium In-medium properties roperties of the f the PowerPoint Presentation

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Michaela Thiel Michaela Thiel

II. Physikalisches Institut, JLU Giessen
II. Physikalisches Institut, JLU Giessen

for for the the A2 collaboration A2 collaboration Hadron Hadron 2011 2011

XIV International Conference XIV International Conference

n Hadron

n Hadron Spectroscopy Spectroscopy

Munich Munich 13–17 June 13–17 June 2011 2011

In-medium In-medium properties roperties

f the

f the ω-meson

meson

near near the the productionthreshold productionthreshold

funded by DFG (SFB/TR 16) funded by DFG (SFB/TR 16)

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properties properties

f the
f the

ω meson meson

1

m=782.65 MeV m=782.65 MeV Γ=8.49MeV =8.49MeV well known well known for for ρ=0: =0:

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properties properties

f the
f the

ω meson meson

1

m=782.65 MeV m=782.65 MeV Γ=8.49MeV =8.49MeV well known well known for for ρ=0: =0:

what what happens happens in a medium? in a medium?

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E / G E / GeV eV

ω

M. Lutz et al.
M. Lutz et al.

NPA 706 (2002) 431 NPA 706 (2002) 431

Spectrum Spectrum / GeV / GeV-2

2

properties properties

f the
f the

ω meson meson

1

m=782.65 MeV m=782.65 MeV Γ=8.49MeV =8.49MeV

model model predictions predictions for for in-medium n-medium masses masses

well known well known for for ρ=0: =0:

what what happens happens in a medium? in a medium?

P. Mühlich
P. Mühlich

et al. et al. NPA 780 (2006) 187 NPA 780 (2006) 187

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E / G E / GeV eV

ω

M. Lutz et al.
M. Lutz et al.

NPA 706 (2002) 431 NPA 706 (2002) 431

Spectrum Spectrum / GeV / GeV-2

2

properties properties

f the
f the

ω meson meson

mass mass shift? shift? broadening? broadening? structures? structures?

experimental task experimental task

1

m=782.65 MeV m=782.65 MeV Γ=8.49MeV =8.49MeV

model model predictions predictions for for in-medium n-medium masses masses

well known well known for for ρ=0: =0:

what what happens happens in a medium? in a medium?

P. Mühlich
P. Mühlich

et al. et al. NPA 780 (2006) 187 NPA 780 (2006) 187

SLIDE 6

exp. approaches
exp. approaches

for for studying tudying in-medium n-medium effects effects

2

sensitive to nuclear sensitive to nuclear density ensity at decay at decay point!

int!

measurement

measurement of the f the meson eson lineshape: lineshape:

reconstruction reconstruction

f invariant mass

f invariant mass from from 4-momenta of decay 4-momenta of decay products: products: (

)

2 1

p p T , , p + = ρ μ r

2 1

X X H + →

ensure ensure that that decays decays

ccur
ccur

in the n the medium: edium: select select shortlived shortlived mesons: esons: cut cut on low n low meson eson momenta momenta for

r ω and

and φ mesons mesons

1.3 fm( 1.3 fm(ρ); 23 fm( ); 23 fm(ω); 46 fm( ); 46 fm(φ)

τ ⋅ βγ = c s

≈

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exp. approaches
exp. approaches

for for studying tudying in-medium n-medium effects effects

2

sensitive to nuclear sensitive to nuclear density ensity at decay at decay point!

int!

measurement

measurement of the f the momentum

mentum distribution:

istribution:

in case in case

f a dropping
f a dropping

in-medium n-medium mass: mass: when when leaving leaving the he nucleus nucleus hadron adron has to become has to become

n-shell;
n-shell;

mass mass generated generated at the at the expense xpense

f kinetic
f kinetic

energy; energy;

sensitive to nuclear sensitive to nuclear density ensity at production at production point!

int!

measurement

measurement of the f the meson eson lineshape: lineshape:

reconstruction reconstruction

f invariant mass

f invariant mass from from 4-momenta of decay 4-momenta of decay products: products: (

)

2 1

p p T , , p + = ρ μ r

2 1

X X H + →

ensure ensure that that decays decays

ccur
ccur

in the n the medium: edium: select select shortlived shortlived mesons: esons: cut cut on low n low meson eson momenta momenta for

r ω and

and φ mesons mesons

advantage: independent of meson advantage: independent of meson lifetime! ifetime!

1.3 fm( 1.3 fm(ρ); 23 fm( ); 23 fm(ω); 46 fm( ); 46 fm(φ)

τ ⋅ βγ = c s

≈

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TAPS TAPS ϑ coverage: 1° - coverage: 1° - 20° 0° CB CB ϑ coverage: 20° - coverage: 20° - 160° 60° 4π setup setup

CB (inside 2 MWPCs, PID) TAPS ← beam LH2-Target

Crystal Ball and TAPS @ MAMI, Mainz Crystal Ball and TAPS @ MAMI, Mainz

Ee-

e-

: max. 1.6 GeV : max. 1.6 GeV

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TAPS TAPS ϑ coverage: 1° - coverage: 1° - 20° 0° CB CB ϑ coverage: 20° - coverage: 20° - 160° 60° 4π setup setup

CB (inside 2 MWPCs, PID) TAPS ← beam LH2-Target

Crystal Ball and TAPS @ MAMI, Mainz Crystal Ball and TAPS @ MAMI, Mainz

Ee-

e-

: max. 1.6 GeV : max. 1.6 GeV

solid targets: C, Nb solid targets: C, Nb

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ω−>π0γ invariant mass invariant mass spectrum spectrum

LH LH2 Carbon Carbon Niob Niobiu ium

4 hadronic decay channel: hadronic decay channel: γA -> (A-1) A -> (A-1)ωp -> (A-1) p -> (A-1)π0γp -> (A-1) p -> (A-1)γγγp

prelimi minary

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background background determination: 2 approaches determination: 2 approaches

5

background background determined determined by by fitting fitting average average deviation eviation from from 1.0 in the 1.0 in the mass mass range range 430 – 430 – 650 MeV: 50 MeV: 1% 1%

pre reli liminary ry

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background background determination: 2 approaches determination: 2 approaches

5

background background determined determined by by fitting fitting average average deviation eviation from from 1.0 in the 1.0 in the mass mass range range 430 – 430 – 650 MeV: 50 MeV: 1% 1% background background determined determined from from data data selecting selecting 4γ and 1proton, and 1proton,

mitting
mitting

1γ randomly randomly

(M. Nanova et al., PRC 82 (2010), 035209)

preliminary preliminary

pre reli liminary ry

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background background determination: 2 approaches determination: 2 approaches

5

background background determined determined by by fitting fitting average average deviation eviation from from 1.0 in the 1.0 in the mass mass range range 430 – 430 – 650 MeV: 50 MeV: 1% 1% agreement agreement within within 2% 2% in the in the lower

wer

mass mass range range near near the the ω signal signal background background determined determined from from data data selecting selecting 4γ and 1proton, and 1proton,

mitting
mitting

1γ randomly randomly comparison comparison

f both
f both

approaches approaches

(M. Nanova et al., PRC 82 (2010), 035209)

preliminary preliminary preliminary preliminary

pre reli liminary ry

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comparison comparison

f
f ω

signal signal lineshapes lineshapes

6 ω signal signal lineshapes lineshapes in good agreement in good agreement for for the he two two different ifferent background background determination determination methods ethods

in addition: in addition: applying applying a missing-mass a missing-mass cut cut and determine and determine the he background background by by a fit a fit

preliminary preliminary

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comparison comparison

f
f ω

signal signal lineshapes lineshapes

6 ω signal signal lineshapes lineshapes in good agreement in good agreement for for the he two two different ifferent background background determination determination methods ethods the the signal signal

btained

btained with with missing-mass missing-mass cut ut has slightly has slightly better better resolution resolution

in addition: in addition: applying applying a missing-mass a missing-mass cut cut and determine and determine the he background background by by a fit a fit

preliminary preliminary

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comparison comparison

f
f ω

signal signal for for different nuclei ifferent nuclei

ω-meson

meson

lineshape lineshape in good in good agreement agreement for

r

C und und Nb Nb target target slightly slightly broader broader compared

mpared

to to LH LH2 signal signal 7

with with missing-mass missing-mass cut cut

preliminary preliminary

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comparison comparison

f
f ω

signal signal for for different nuclei ifferent nuclei

ω-meson

meson

lineshape lineshape in good in good agreement agreement for

r

C und und Nb Nb target target slightly slightly broader broader compared

mpared

to to LH LH2 signal signal 7

is is this this consistent consistent with with an an in-medium in-medium broadening broadening (Γmed

med

150 MeV) 150 MeV) determined determined from from the the Transparency ransparency ratio? atio?

≈

(M. Kotulla et al., PRL 100 (2008), 192302)

with with missing-mass missing-mass cut cut

preliminary preliminary

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comparison comparison

f
f ω

signal signal for for different nuclei ifferent nuclei

ω-meson

meson

lineshape lineshape in good in good agreement agreement for

r

C und und Nb Nb target target slightly slightly broader broader compared

mpared

to to LH LH2 signal signal 7

is is this this consistent consistent with with an an in-medium in-medium broadening broadening (Γmed

med

150 MeV) 150 MeV) determined determined from from the the transparency transparency ratio? atio?

≈

(M. Kotulla et al., PRL 100 (2008), 192302)

test on the test on the sensitivity ensitivity to in-medium to in-medium signal ignal

with with missing-mass missing-mass cut cut

preliminary preliminary

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GiBUU GiBUU simulations imulations (J. Weil) (J. Weil)

energy energy range: 900 – range: 900 – 1300 MeV (E 1300 MeV (Ethresh

thresh

= 1108 MeV) = 1108 MeV)

⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ρ ρ α + =

0 1

m m

with with α = -0,16 = -0,16

no in-medium no in-medium modification

dification

collisional collisional broadening broadening (Γmed

med = 150MeV)

= 150MeV)

coll. broadening
coll. broadening plus

plus mass mass shift shift mass mass shift shift (-16%)

16%)

4 scenarios: 4 scenarios:

nly
nly

small small difference ifference in lineshape in lineshape for for the the 4 scenarios 4 scenarios

no modification no modification

coll. broadening
coll. broadening
coll. broadening
coll. broadening

+ mass + mass shift shift mass mass shift shift

nly

nly

J. Weil
J. Weil

8

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comparison comparison

exp. data
exp. data

to GiBUU to GiBUU (J. Weil / U. Mosel) (J. Weil / U. Mosel)

GiBUU GiBUU (for (for Nb target): b target):

no in-medium no in-medium modification

dification

collisional collisional broadening broadening (Γmed

med

= 150 MeV) = 150 MeV) collisional collisional broadening broadening plus mass plus mass shift shift (Γmed

med

= 150 MeV, = 150 MeV, α = -0.16) = -0.16) mass mass shift shift only nly (α = -0.16) = -0.16) 9

data data disfavour disfavour „mass mass shift shift

nly

nly“ scenario “ scenario

preliminary preliminary

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limited limited sensitivity sensitivity to in-medium to in-medium signal signal

(F. Eichstaedt et al.,

Prog. Theo. Phys. Suppl.

168 (2007) 495)

( )

tot state final V 2 tot 2 2 2 V 2 tot tot state final V X X H

m A ~ d d

2 1

Γ Γ ⋅ Γ μ + − μ Γ ⋅ μ = Γ Γ ⋅ μ μ σ

→ → →

ω yield yield reduced educed by by increase increase

f in-medium
f in-medium

width width ( ) ) spread spread

ut in mass
ut in mass

experimentally experimentally observed

bserved mass

mass distribution distribution = convolution = convolution of

f

spectral spectral function function with with branching branching ratio ratio into nto channel channel being being studied studied

vac med

16 Γ ⋅ ≈ Γ

3 effects 3 effects limit limit sensitivity sensitivity: 10 10

nly
nly

20% of all 20% of all ω decays decays

ccur
ccur

at at ρ > 0.1 > 0.1ρ0

S. Friedrich
S. Friedrich
S. Friedrich
S. Friedrich

(M. Kotulla et al., PRL 100 (2008), 192302)

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measurement measurement

f the

f the momentum momentum distribution distribution

carbon carbon beamtime beamtime analysis analysis with with exactly exactly 3 ω yield yield in different momentum n different momentum bins bins

11 11

γ (+0,1,2,… charged) final state (+0,1,2,… charged) final state

pre reliminary

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Carbon Carbon Niob Niobiu ium GiBUU GiBUU calculations alculations (Nb): (Nb): no in-me no in-medium ium modification modification collisional collisional broadening broadening collisional collisional broadening broadening plus mass plus mass shift shift mass mass shift shift

nly
nly

measurement measurement

f the

f the momentum momentum distribution distribution

J. Weil
J. Weil

data data disfavour disfavour „mass mass shift shift“ and „ “ and „coll. broad. + mass

coll. broad. + mass

shift shift“ scenario “ scenario normalized normalized to to same same area area

pre reliminary

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conclusion conclusion and outlook and outlook

ω-lineshape

lineshape analysis

analysis sensitive to nuclear sensitive to nuclear density ensity at decay at decay point

int

signal signal sensitive to background sensitive to background determination determination reduced reduced sensitivity sensitivity favours favours scenarios scenarios without ithout mass ass shift shift ω-momentum

momentum analysis

analysis sensitive to nuclear sensitive to nuclear density ensity at production at production point point favours favours scenarios scenarios without ithout mass ass shift shift model model dependent! ependent! 13 13

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conclusion conclusion and outlook and outlook

ω-lineshape

lineshape analysis

analysis sensitive to nuclear sensitive to nuclear density ensity at decay at decay point

int

signal signal sensitive to background sensitive to background determination determination reduced reduced sensitivity sensitivity favours favours scenarios scenarios without ithout mass ass shift shift ω-momentum

momentum analysis

analysis sensitive to nuclear sensitive to nuclear density ensity at production at production point point favours favours scenarios scenarios without ithout mass ass shift shift model model dependent! ependent!

utlook:
utlook:

lineshape lineshape analysis: energy analysis: energy range range Eγ = 900 – = 900 – 1100 MeV 100 MeV cut cut on n ω momentum: p momentum: pω < 300 MeV < 300 MeV 13 13

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backup backup slides slides

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backup backup slides slides

experiment experiment requires requires very very accurate accurate energy energy calibration calibration

1%
1%

+1% +1% +2% +2%

2%
2%

π0 mass mass η mass mass 14 14

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L1 L1 L2 L2 L3 L3

L2 L2 L1 L1 L3 L3

σ=0,47ns =0,47ns σ=0,89ns =0,89ns σ=0,8ns =0,8ns

prompt time event prompt time event selection election

photon photon / particle / particle separation separation possible possible using using time-of-flight time-of-flight 15

15

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charged charged particle particle identification dentification

t=0 ns t=0 ns identification identification

f charged
f charged

particles particles in: n: PID (CB): PID (CB): ΔE vs E vs E TAPS: TAPS: ΔE vs E vs E and E vs E and E vs t 16 16

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pion pion sideband sideband subtraction subtraction

mπ0γ / Me / MeV counts counts / 1MeV / 1MeV

570MeV<m 570MeV<mγγγ <630MeV <630MeV

structure structure around round 600MeV 600MeV from from π0η-events

events

remove remove background background below below π0 peak peak by by sideband sideband subtraction subtraction

removes removes structure tructure around around 600MeV! 600MeV!

17 17