panda: an experiment to investigate hadron structure using antiproton beams

James Ritman Univ. Giessen

PANDA: An Experiment To Investigate Hadron Structure

Using Antiproton Beams

• Overview of the GSI Upgrade

• Overview of the PANDA Physics Program

• Exotic Hadrons in the Charm Mass Region

• HESR: High Energy Storage Ring

• The PANDA Detector

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The GSI Future Project

• Heavy Ion Physics: hot and dense nuclear matter

• Nuclear Structure: paths of nucleo-synthesis

• Ion and laser induced Plasma: very high energy densities• Atomic physics: QED, strong EM fields, Ion-Matter interactions• Physics with Antiprotons properties of the strong force

Project approved Feb 2003

James Ritman Univ. Giessen

What Do We Want To Know?

• Why don‘t we observe isolated quarks?Q-Q potential in the charmonioum system

• Are there other forms of hadrons?e.g. Hybrids qqg or Glueballs gg

• Why are hadrons so much heavier than their constituents?

p-A interactions

James Ritman Univ. Giessen

Why Don’t We See Isolated Quarks?

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Charmonium – the Positronium of QCD

3D2

2900

3100

3300

3500

3700

3900

4100

c(3590)

c(2980)

hc(3525)

(3097)

(3686)

(3770)

(4040)

0(3415)

1(3510) 2(3556)

3D1

3D3

1D2

3P2(~ 3940)

3P1(~ 3880)

3P0(~ 3800)

(~ 3800)

1 fm

C C

~ 600 meV -1000

-3000

-5000

-700011S

0

13S1

21S0 23S

121P

1 23P2

23P1

23P0

031S

0 31D

2 33D2

33D1

33D2

Ionisationsenergie33S

1

e+ e-0.1 nm

Binding energy [meV]

Mass [MeV]

DDThreshold

8·10-4 eV

10-4 eV

• Positronium • Charmonium

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Probe large separations with highly excited qq states_

Charmonium Spectroscopy

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Open Questions `

c(3590)

• Partial width mostly unknown• Precision spectroscopy

• confirm hc

• Little is known about states above DD

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Why Antiprotons?

• e+e- annihilation via virtual photon: only states with Jpc = 1--

• In pp annihilation all mesons can be formed

• Resolution of the mass and width is only limited by the beam momentum resolution

Measured rate

Beam

Resonance cross

section

CM Energy

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High Resolution

• Crystal Ball: typical resolution ~ 10 MeV

• Fermilab: 240 keV

p/p < 10-4 needed

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Why Are Hadrons So Heavy?

Hadron Masses

Protons = (uud) ?2Mu + Md ~ 15 MeV/c2

Mp = 938 MeV/c2

(P.Kienle)

no low mass hadrons (except , K, )

spontaneously broken chiral symmetry

Spontaneous Breaking of Chiral Symmetry

Although the QCD Lagrangian is symmetric, the ground state need not be. (e.g. Fe below TCurie )

Example:

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Quark Condensate

The QCD vacuum is not empty 0qq

Hadron masses are generated by the strong interaction with <qq> (also with gluon condensate)

The density of the quark condensate will change as a function of temperature and density in nuclei.

This should lead to modifications of the hadron’s spectral properties.

Hadrons in the Nuclear Medium

Spectral functions

W.Peters et al., Nucl. Phys. A632, 109 (1998).S.Klimt et al., Nucl. Phys. A515, 429 (1990).

<qq>

Reduction of <qq>

Hadron Production in the Nuclear Medium

c d_

d du

c_ d

repulsive

attractive

D-

D+d du

d du

d du

d du

d du

Quark atom

Mass of particles may change in dense matter( ) : 40

( ) : 200

s u

c d

K su m m

D cd m m

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Advantages of p-A Reactions Compared to A-A

Much lower momentum for heavy producedparticles (2 GeV for “free”)

(Effects are smaller at high momentum)

Open charm mass region (H atom of QCD) @HESR(single light quark)

Well defined nuclear environment (T and )

Strange Baryons in Nuclear FieldsHypernuclei open a 3rd dimension (strangeness) in the nuclear chart

-

3 GeV/c

K+KTrigger

_

secondary target

p

• Double-hypernuclei: very little data

• Baryon-baryon interactions: -N only short ranged (no 1 exchange due to isospin) impossible in scattering reactions

-(dss) p(uud) (uds) (uds)

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Exotic Hadrons

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Glueballs

gg

g

RG

GR

BGGRRB

C. Morningstar PRD60, 034509 (1999)Self interaction between gluons

Construction of color-neutral hadrons with gluons possible

exotic glueballs don‘t mix with mesons (qq)

0--, 0+-, 1-+, 2+-, 3-+,...

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RBRB

Prediction in QCD:

Collective gluon excitation

(Gluons contribute to quantum numbers)

Ground state: JPC = 1-+ (spin exotic)

Charm Hybrids ccg

distance between quarks

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Mixing With Mesonic States

Width: could be narrow (5-50 MeV) since

DD suppressed for some states

O+- DD,D*D*,DsDs (CP-Inv.)

(QQg) (Qq)L=0+(Qq)L=0 (Dynamic Selection Rule)

If DD forbidden, then the preferred decay is

(ccg) (cc) + X , e.g. 1-+ J/

Ex

oti

c lig

ht

qq

Ex

oti

c cc

1 - - 1 - +

0 2 0 0 0 4 0 0 0M e V / c2

10 - 2

1

1 0 2

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Partial Wave Analysis

Partial wave analysis as important tool

Example of 1-+ (CB@LEAR)pd X(1-+)++p, X

Strength ~ qq States !

Signal in production but not in formation is interesting !

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The Experimental Facility

HESR

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HESR: High Energy Storage Ring

Beam Momentum 1.5 - 15 GeV/c

High Intensity Mode:Luminosity 2x1032 cm-2s-1 (2x107Hz)p/p (st. cooling) ~10-4

High Resolution Mode:Luminosity 2x1031 cm-2s-1 p/p (e- cooling) ~10-5

James Ritman Univ. Giessen

James Ritman Univ. Giessen

Target• A fiber/wire target will be needed for D physics,• A pellet target is conceived:

1016 atoms/cm2 for D=20-40m

1 mm

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Micro Vertexing

7.2 mio. barrel pixels50 x 300 μm

2 mio. forward pixels100 x 150 μm

Central Tracking Detectors

example event: pp 4K

• MVD: (Si) 5 layers• Straw-Tubes: 15 skewed double-layers• Mini-Drift-Chambers

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Tracking Resolution

J/ K+K- (J) = 35 MeV/c2

() = 3.8 MeV/c2

Example reaction: pp J/ (s = 4.4 GeV/c2)

Single track resolution

Invariant mass resolution

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PID with DIRC

(DIRC@BaBar)

GEANT4 simulationfor HESR:

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Electromagnetic CalorimeterDetector material PbWO4

Photo sensors Avalanche Photo Diodes

Crystal size 35 x 35 x 150 mm3 (i.e. 1.5 x 1.5 RM2 x 17 X0)

Energy resolution 1.54 % / E[GeV] + 0.3 %

Time resolution 130 ps (N.B. with PMT!)

Total number of crystals 7150

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Staged Construction

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Summary

• GSI will explore the intensity frontier

• High luminosity cooled p-bar from 1-15 GeV/c

• Wide physics program including

• Charmonium spectroscopy

• pbar-A reactions

• Search for glueballs and charm hybrids

• Panda collaboration forming

James Ritman Univ. Giessen

List of participatinginstitutions(incomplete)

40 Institutes (32 Locations) from 9 Countries:Austria - Germany – Italy – Netherlands – Poland – Russia – Sweden – U.K. – U.S.

James Ritman Univ. Giessen

Physics with stopped antiprotons 18-19 September 2003 at GSI