In-medium Properties of In-medium Properties of the the

andandPAC33 Proposal PR08-018PAC33 Proposal PR08-018

M. H. Wood (spokesperson), C. Djalali (spokesperson),M. H. Wood (spokesperson), C. Djalali (spokesperson),R. Gothe, D. Tedeschi, S. StrauchR. Gothe, D. Tedeschi, S. Strauch

Univ. of South CarolinaUniv. of South Carolina

R. Nasseripour (spokesperson)R. Nasseripour (spokesperson)George Washington Univ.George Washington Univ.

D. Weygand (spokesperson) D. Weygand (spokesperson)

Jefferson LabJefferson Lab

and the CLAS Collaborationand the CLAS Collaboration

Mesons in the MediumMesons in the MediumHadronic structure is going to be altered due to the proximity of other hadrons.Predicted modifications can be viewed :

Seminal work on scaling law:G. E. Brown and M. Rho, PRL 66,2720, (1991)

8.0)( *

0*

f

f

m

m

V

V

Cited 786 times in SPIRES database

Quark-gluon level:•Chiral symmetry is broken by the small u,d masses.•In hot/dense medium, •Chiral symmetry restoration.

Many-body effects:•Modified coupling constants•Modified loops•Opening of decay channel•…

0qq

Meson in the MediumMeson in the Medium

Many-body effects:R. Rapp, G. Chanfray, J Wambach, Nucl Phys. A617 (1997) 472

meson

meson

vacuum state

Chiral symmetry restoration:T. Hatsuda and S. H. Lee,Phys. Rev. Lett. 66, 2720 (1992)

Calculations by the Valencia group - hybrid of quark effects and nuclear many-body effects.

JLabdensities

Meson in the MediumMeson in the MediumQuark-Meson Coupling Model (A. W. Thomas):K. Saito et al., Phys. Lett. B 433 (1998) 243

K. Saito et al., Phys. Rev. C 59 (1998) 1203

K. Saito et al., Prog. Part. Nucl. Phys. 58 (2007) 1

Considers the meson as a quark-anitquark pair coupled to the nucleons through -meson exchange.

Applied to -nucleus bound states and meson propagation in the medium.

Does not include absorption of the meson in the nucleus.

JLab densities

KEKKEK CBELSA/TAPSCBELSA/TAPS CERESCERES NA 60NA 60

Reaction

pA () A’VM e+e-

A A’ 0

p+Au,Pb+Au e+e-

In+In +-

Condition

=0.53=0.5300, T~0 , T~0 MeVMeV

=0.55=0.5500, T~0 , T~0 MeVMeV

158 A GeV158 A GeV 158 A GeV158 A GeV

Massmm~~mm~-9%~-9%

mm ~ -4% ~ -4%mm ~ -14%* ~ -14%* m not favoredm not favored No mass shiftNo mass shift

Width

~ ~ ~ 0 ~ 0 MeVMeV

((==00) = 47 ) = 47 MeVMeV

((==00))140 140 MeVMeV

(unpublished)(unpublished)

Broadening Broadening favoredfavored

Strong Strong broadeningbroadening

IssuesNo direct No direct extraction of extraction of mesonmeson

00 FSI FSI

Large Large background background (100x)(100x)

, T not , T not constantconstant

, T not , T not constantconstant

M.Naruki et al.,PRL 96 (2006)

R. Muto et al.,PRL 98 (2007)

*D. Trnka et al,PRL 94 (2005)

R. Arnaldi et al.,PRL 96 (2006)

D. Adamova et al.,PRL 91 (2003)

Experimental Results

Elementary Reactions Rel. Heavy-Ion

CLAS Experiment at Jefferson LabCLAS Experiment at Jefferson Lab(T~0 MeV and (T~0 MeV and ~0.5~0.5

Predicted medium modifications are large enough to be observed at normal nuclear density. • Vector mesons produced in various nuclei.• Photon beam probes the interior of the nucleus.• e+e- decay : no final state interactions, 10-5 branching ratio• CLAS detector rejection of pion pairs: 107

• Detect all three mesons simultaneously.• Measure the meson directly and cleanly.

1 meson – decays inside the nucleus (direct properties).

and mesons – interact inside nucleus (many-body effects).

c~1.3 fm

c~23.4 fm

c~44.4 fm

ee++ee-- Mass Spectra and Background Determination Mass Spectra and Background Determination

NNN 2

measurement: at CERN-SPS IPNO-DR-02.015 (2002) measurement: at CERN-ISR (Nucl. Phys. B124 (1977) 1-11).e+e- measurement: at RHIC (arXiv:nucl-ex/0510006 v1 3 Oct 2005).Proton Femtoscopy of eA interactions: ITEP group, CLAS Analysis 2003-103

Mixed event background Mixed event background determination:determination:ShapeShape – random mixing of e+ – random mixing of e+ and e- from single lepton events.and e- from single lepton events.

Absolute normalizationAbsolute normalization - pairs - pairs of identical (e+e+, e-e-) leptons, of identical (e+e+, e-e-) leptons, which are produced only by which are produced only by uncorrelated processes provide uncorrelated processes provide an absolute normalization.an absolute normalization.

The The Mass Spectra Mass Spectra

After removing the , , and background contributions:

TargeTargett

Mass (MeV/cMass (MeV/c22))

CLAS dataCLAS dataWidth(MeV/Width(MeV/cc22))

CLAS dataCLAS data

Mass(MeV/Mass(MeV/cc22))

Giessen Giessen Sim.Sim.

Width(MeV/cWidth(MeV/c22))

Giessen Sim.Giessen Sim.

1212CC 762.5 +/- 3.7762.5 +/- 3.7 176.4 +/- 9.5176.4 +/- 9.5 773.8 +/- 773.8 +/- 0.90.9

177.6 +/- 2.1177.6 +/- 2.1

5656FeFe 779.0 +/- 5.7779.0 +/- 5.7 217.7 +/- 217.7 +/- 14.514.5

773.8 +/- 773.8 +/- 5.45.4

202.5 +/- 11.6202.5 +/- 11.6Broadening of the width is consistent with many-body effects.

Fit with Breit-Wigner/M3, where M and are free parameters.

D2 C Fe

e+e- Invariant Mass (GeV)

OutcomeOutcomePublish• PRL published – R. Nasseripour et al., PRL 99 (2007) 262302

• PRC article will be submitted in January 2008.

ImpactResult does not confirm the KEK results.Rule out M predictions of Brown/Rho and Hatsuda/Lee.

Momentum DependenceMass spectra – spectral function, branching ratio, production.Need more information - momentum dependence.

Chiral symmetry restoration - expected to be momentum independent.

Many-body effects – momentum dependent.

Momentum Dependence – Momentum Dependence – MesonMeson

Giessen group (U. Mosel):W. Peters et al., NPA 632 (1998) 109

M. Post et al., NPA 741 (2004) 81

BUU model of meson production and propagation with nucleon resonance-hole contributions.

Momentum Dependence - Momentum Dependence - ProposalProposal

With new measurement, With new measurement, we will obtain we will obtain 4 bins of 4 bins of equal statistics in equal statistics in momentum.momentum.

The sensitivity of each The sensitivity of each bin will be better than bin will be better than what was achieved over what was achieved over the entire previous the entire previous CLAS experiment.CLAS experiment.

Proposed improvement:Proposed improvement:5x statistics5x statisticsUse Nb and Fe targetsUse Nb and Fe targets

Previous data5x statistics

Momentum Dependence - Momentum Dependence - ExperimentExperiment

Below are the projected errors for each momentum bin based on the previous CLAS results.

CLAS result - Fe

Estimated error Esimated error – total Nb

Additional StudiesAdditional StudiesPrevious -meson in Fe result:M – small and consistent with zero. – broadening consistent with many-body effects.

Proposal:Momentum dependence of M and of meson in Fe and Nb.

Absorption studies:Although the detected and mesons decay outside the nucleus, the in-medium widths can be accessed through meson-nucleon interactions.

c~1.3 fm

c~23.4 fm

c~44.4 fm

P. Mühlich and U. Mosel

NPA 773 (2006) 156

180 MeV

93 MeV

= 47 MeV

M. Kaskulov, E.Hernandez and E. OsetEPJ A 31 (2007) 245

= 34 MeV

94 MeV

Transparency ratio:

XC

XA

XN

XAA AA

T

12

12The in-medium width is =0+* where * = v*

VN

Absorption of Meson and its In-medium Width

Normalized to carbon Normalized to carbon

Comparison of Comparison of Meson Results Meson Results

Preliminary JLab result shows greater in-medium broadening.

JLab (preliminary)

TAPS (arXiv:nucl-ex0711.4709v2, Dec 2007)TAPS latest: ~130-150 MeV

Proposed JLab data

Comparison to Expt. – Comparison to Expt. – Meson MesonThe Spring8 experiment was A A’ K+K- A’ (E=1.5-2.4 GeV).

JLab (preliminary)

Spring8 T. Ishikawa et al. Phys. Lett. B 608, 215 (2005)

Giessen calculations

Giessen calculationsw/ Spring8 absorptionstrengths

CLAS has the advantage of the e+e- detection.

Proposed experiment will study momentum dependence.

Proposed JLab data

Unique Characteristics of CLASUnique Characteristics of CLAS

Intense photon beam. Vertex reconstruction for novel target design. Excellent e+e- identification and +- rejection. Clean mass spectra with all three vector mesons. Low background which is determined accurately.

The CLAS detector at 3 GeV is ideal for the study of the in-medium properties of the vector mesons.

This ProposalThis Proposal

Beam energy: 3 GeVBeam energy: 3 GeV Targets: LD2, C, Fe, Nb, SnTargets: LD2, C, Fe, Nb, Sn

LD2 – controlLD2 – control Fe – quality checkFe – quality check Nb – new results on Nb – new results on meson meson C – normalization; C – normalization; ,, studies studies Sn – new result; Sn – new result; ,, studies studies

Fe and Nb thicknesses: Fe and Nb thicknesses:

2.5 g/cm2.5 g/cm22 ( (x2.5x2.5) ) Beam time: 36 days (Beam time: 36 days (x2x2)) Statistical improvement: Statistical improvement: x5x5

Previous target

LD2C C C C

FeTi

Pb

Proposed target (not to scale)

SummarySummary

Medium modifications are complicated with various interactions:

Fundamental : chiral symmetry restoration, quarks/gluons Effective : nuclear many body effects Hybrid : quark-meson couplings

Proof of chiral symmetry restoration can only be achieved with an understanding of the vector-meson many-body effects.

Proposal:1. Momentum dependence of the in-medium properties of

meson in Fe and Nb.2. Additional studies – and meson in-medium widths accessed

through absorption.

Backup SlidesBackup Slides

Effective DensityEffective Density

J. G. Messchendorp, private J. G. Messchendorp, private communicationcommunication

Momentum Dependence – Momentum Dependence – MesonMesonGiessen group (U. Mosel):

W. Peters et al., NPA 632 (1998) 109

M. Post et al., NPA 741 (2004) 81

BUU model of meson production and propagation with nucleon resonance-hole contributions.

Transverse

Longitudinal

Momentum Dependence - Momentum Dependence - Meson Meson• Preliminary CBELSA/TAPS results.• Wealth of information in the absorption measurement.• Issue with subtraction of large background.• These results need to be independently checked.

Integrating over momentum range

Dividing into momentum bins

Valencia group (no momentum dep.)TAPS data

Giessen group (before TAPS result)Giessen group (after TAPS result)

Momentum Dependence – Momentum Dependence – MesonMeson

Quark-Meson Coupling Model (A. W. Thomas):K. Saito et al., Phys. Lett. B 433 (1998) 243

K. Saito et al., Phys. Rev. C 59 (1998) 1203

K. Saito et al., Prog. Part. Nucl. Phys. 58 (2007) 1

Longitudinal

Transverse

Calculations at =20

Recent PAC Approved Photon-Recent PAC Approved Photon-beam Experimentsbeam Experiments

Run Run periodperiod

Beam time (days)Beam time (days) PAC ratingPAC rating

g9/FROSTg9/FROST 3737 A-A-

g10g10 3030 AA

g11g11 3535 A-A-

g12g12 3535 AA

g13g13 4848 A-A-

Phase DiagramPhase Diagram

0 | qq | 0

0 | qq | 0 0 | qq | 0

Hadronic properties depend on the quark condensate can change with (density) and T (temperature).As goes to zero, hadron masses go to zero.

How to measure modifications?

Relativistic Heavy Ion Collisions•collide heavy nuclei (Au+Au) at high speeds•compression of the 2 nuclei creates an environment of high temperature and density

Light vector meson in a stationary nucleusLatest predictions range from 5-20%.

m10fm 1

fm 168.0 15-

-30

Multi-Segment Nuclear Multi-Segment Nuclear TargetTarget Contains materials with different average densities.

LD2 and seven solid foils of C, Fe, Pb, and Ti.Each target material 1 g/cm2 and diameter 1.2 cmApproximately same number of nucleons/target

Proper spacing 2.5 cm to reduce multiple scattering Deuterium target as reference, small nucleus, no modification is

expected.

Event DisplayEvent Display

e+

e-

p

Due to the magneticfield orientation,the positively-chargedparticles bend away from the beamline.

The negatively-charged particles bend inward.

ee++ee-- Invariant Mass Spectra Invariant Mass Spectra

Same sector e+e- removed Momentum corrections Target energy loss corrections Lepton momentum > 500 MeV

Mixed-event background (see next slide)

Same sector events

Background Subtracted FitsBackground Subtracted Fits

Model the uncorrelated background using “mixed-events” technique. Monte-Carlo distributions of individual possible channels that contribute to e+e-

mass spectrum are generated by Giessen BUU model and to fit the data. Nucl. Phys. A671, 503(2000)

Vector mesons : M=768 MeV = 149 MeV c~1.3 fm JP=1- : M=782 MeV = 8 MeV c~23.4 fm

: M=1020 MeV = 4 MeV c~44.4 fm

The The Mass Spectra Mass Spectra

Fit function:

34

WignerBreit1WignerBreit

MM

M

Photonpropagator

Breakup momentumphase space

D2 C Fe

e+e- Invariant Mass (GeV)

After removing the , , and background contributions:

Extracting the Result

1. Make ratio of mass spectra of heavy target to reference target.

2. Fit the slope in region of meson.

3. Compare with relation of slope to the percentage change in mass.In Fe nucleus, g7a sets an upper

limit with a 95% confidence level: m~-21 MeV.Broadening of the width is consistent with nuclear many-body effects.

Accepted by PRL, Oct. 2007.PRC version in ad hoc committee.

OutcomeOutcomePublish• PRL published – R. Nasseripour et al., PRL 99 (2007) 262302

• PRC article will be submitted in January 2008.

ImpactResult does not confirm the KEK results.Rule out M predictions of Brown/Rho and Hatsuda/Lee.

Momentum DependenceMass spectra – spectral function, branching ratio, production.Need more information - momentum dependence.

M

pL

Decay length L:p=momentumM=mass=width

Chiral symmetry restoration is expected to be momentum independent.Momentum dependence addresses many-body effects.