Anar Rustamov, GSI Darmstadt For the HADES collaboration

Anar Rustamov, GSI Darmstadt 

For the HADES collaboration

Hadron masses 

Chiral Symmetry Restoration 

In Medium Modifications of Vector Mesons 

CERES results 

DLS Puzzle 

HADES Results 

Results from pp 

Summary and outlook

Hadron Masses 

Current masses of u and d quarks are less than 20 MeV 

How can these quarks make a mass of nucleon of about 1 GeV ? 

There is even binding energy, reducing the mass further 

Chirality 

A.Rustamov, RNP meeteng, From MeV to TeV, May 23-28,Dubna

π = iψ τ γ ψ 

5 

r r 

ρ = ψ τ γ ψ 

σ = ψ ψ 

r r 

a = ψ τ γ 

Chiral symmetry 

γ ψ 

µ 1 µ 

µ 5 

axial : ψ → 

vector : ψ → 

r 

π → 

r 

ρ → 

r 

π → 

r 

ρ → 

e 

e 

r r 

π + θ × 

r r 

ρ + θ × 

r r 

π + θ × 

r r 

ρ + θ × 

− i γ 

5 

r 

τ r 

− i θ 

2 

r 

π 

r 

ρ 

σ 

a r 

r 

τ r 

θ 

2 

ψ 

1 µ 

ψ 

m 

m 

ρ 

= 770 

= 1260 

a 1 

MeV 

MeV 

Spontaneously broken: 

f 0 0 

+ 

? 

< qq >≠0 

A.Rustamov, RNP meeteng, From MeV to TeV, May 23-28,Dubna 

1. Absence of parity doublets in hadron spectrum 

2. Appearance of Goldstone bosons

Chiral symmetry 

Klimt, Lutz , Weise, 

Phys.Lett.B249 (1990) 386 

< 

< 

q q 

q q 

> 

> 

σ 

ρ 

π N 

≈ 1 − 

2 2 

0 fπ 

m π 

ρ 

< 

< 

q 

q 

q 

q 

> 

> 

T 

0 

≈ 

1 

− 

8 

T 

f 

π 

2 

2 

Brown-Rho scaling: 

m 

m 

* 

ρ 

ρ 

= 

m 

m 

* 

ω 

ω 

= 

< 

( 

< 

qq 

qq 

> 

> 

ρ 

0 

) 

1/ 3 


Brown+Rho, PRL 66 (1991) 2720 

and others . . .

Hadronic interaction 

In vacuum 

In medium 

ρ 

π 

π 

ρ 

ρ 

π 

∆(1232) 

N -1 

ρ 

N(1520) 

+ ρ ρ 

N -1 

+ 

... 


Spectral functions 

vacuum ρ = ρ , T = 0 

0 

ρ = 1.4* 

ρ ,T = 166MeV 

0 


Vector mesons 

cτ ≈10-15 fm/c 

m 

e+ 

e− 

= 

p 

e+ 

p 

e− 

e+ 

e- 

ϑe+ 

sin 

2 

e− 

HADES 

(p, π, A) + A collisions at SIS – GSI, 

0 ≤ ρ ≤ 3 ρ 0 , 0 ≤ T ≤ 80 MeV 

Dielectron two-body decays of light 

Vector Mesons ρ, ω, φ 

High resolution spectroscopy of e + e - - 

pairs, no final state interaction ! 

Meson Mass Γ cτ (fm) Main e + e - BR 

(MeV/c 2 ) (MeV/c 2 ) 

decay 

ρ 768 152 1.3 π + π − 4.4 x 10 -5 

ω 782 8.43 23.4 π + π − π 0 7.2 x 10 -5 

φ 1019 4.43 44.4 K + K - 3.1 x 10 -4 



EXPERIMENTAL RESULTS

DLS experiment 

Data: R.J. Porter et al.: PRL 79(97)1229 

Model: E.L. Bratkovskaya et al.: 

NP A634(98)168, BUU, 

vacuum spectral function 


! cannot be described by dropping mass 

scenario or modified spectral functions

CERES experiment 

J.P.Wessels et al., Nucl. Phys. A 715 (2003) 262 

modified spectral functions 

dropping mass only 

π + π - →ρ annihilation 

! Enhancement larger than at 158 AGeV! 


• Geometry 

Full azimuth , polar angles 18 o - 

85 o 

Pair acceptance ≈ 0.35 

about 80.000 detector channels 

• Fast particle identification 

Hadron blind RICH : gasous 

Cherenkov 

TOF (Scintillator rods) : σ≈150 ps 

Pre-Shower for em. shower 

detection 

• RICH, TOF, Pre-Shower 

Image processing Online e + e - 

identification 

• Momentum measurement 

ILSE, super conducting toroid 

Bρ = 0.7 Tm 

MDC Multi-wire drift chamber, 

σ y 

≈ 100 µm 

∆M e+e 

/M≈1.5% at ρ/ω - 


I First Level Trigger 

• TOF/TOFINO multiplicity 

II Second Level Trigger 

Electron candidates in IPUs: 

• Shower hits 

• Cherenkov rings 

• Time-of-flight cut 

• Matching hits (∆θ,∆φ) 

III Third Level Trigger 

(implemented offline) 

• matching with MDC tracklets 


HADES DATA RUNS 

November 2001: commissioning run (target=5% C) 

C+C 2AGeV LVL1 triggered events (M ch. >3) : 36*10 6 events 

C+C 1AGeV LVL1 trigger 

: 7.3*10 6 events 

full coverage with inner MDC chambers (δp≈10% at 0.7 GeV/c) 

November 2002: commissioning and physics runs (target= 2x2.5% C) 

C+C 2AGeV ∼200*10 6 events: 56% LVL1 trigger + 44% LVL2 trigger 

4 outer MDCIII-IV (δp≈5% at 0.7 GeV/c) 

October 2003: 

first proton commissioning run (T=1 GeV, 2 GeV) 

full coverage with outer MDCIII (4 MDC IV) (δp≈2% at 0.7 GeV/c) 

Jan 04: 

Aug04: 

pp run, (2.2 GeV) 

C+C 1GeV 



Particle identification

Combinatorial background 

60% leptons from conversion 20% leptons from pi0 e - Dalitz 

γ e + 

conversion 

e - Θ ~ 2.2 0 

γ 

π 0 

e 

π 0 + 

γ 

Dalitz decay e - 

e + 

e - 

Θ ~ 15.2 0 

e + 

π 0 γ e - 

1. Like sign method 

e + 

Assumption: 

a. Like sign pairs are uncorrelated 

b. Single lepton distributions are similar 

Still can be some physics processes like , 

respect to Dalitz decay 

0 

π 

→ 

e 

+ 

e 

+ 

e 

− 

e 

− 

but suppressed highly, with 

2. Event mixing 

Unlike sign pairs from different events 


2 

χ 

cut 

Analysis Strategy 

1 Cut 

2 Cut 

3 Cut 

B r 

x 

x 

META 

B r 

x 

META 

B r 

x 

x 

MDC II 

MDC II 

) 

MDC II 

MDC I 

MDC I 

MDC I 

RICH 

RICH 

Opening 

angle Θ 

RICH 

Target 

Target 

Target 


Coctail plot 

• Two body meson decays (peaks): 

V → e+e- 

• Dalitz-meson decays 

(continuum): 

Γ 0 

π 

Γ 

Γ 

→ γ 

ω → π 

0 

e 

e 

η → γ e 

+ 

+ 

+ 

e 

e 

e 

− 

− 

− 

Γ 

Γ 

Γ 

tot 

tot 

tot 

≈ 

≈ 

≈ 

1.2 ⋅ 10 

5.9 ⋅10 

4.9 ⋅10 

−4 

−3 

−2 

• CB - combinatorial background from multi π 0 decays! 


No Efficiency / Acceptance Correction 

B + - = N e+e+ + N e-e- 

PRELIMINARY 

S + - = N e+e- - B +- 


PRELIMINARY 


PP data 

Energy 2.2 GeV 

Elastc channel 

η 

PP channel- acceptance and lepton identification efficiency study 


PP->ppETA 

p p 

+ − 

π π 

+ + + - 

p 

+ 

π 

+ 

π 

p 

p p 

− 

π 

− 

π 

Kinematic Fit 

F = ( α − ~ α ) ( ~ 

T 

V 

−1 

α − α ) + 

i 

i 

ij 

j 

j 

λ 

k 

F 

k 

( 

~ ) 

α 

r 

α 

i 

= 

⎛ Pi 

⎜ 

⎜ θ 

i 

⎜ 

⎝ ϕ 

i 

⎞ 

⎟ 

⎟ 

⎟ 

⎠ 

~ α 

r 

= 

~ 

⎛ Pi 

⎜ ~ 

⎜ θ 

i 

⎜ ~ 

⎝ ϕ 

i 

⎞ 

⎟ 

⎟ 

⎟ 

⎠ 


Before kinematik fit 

After kinematik fit 

Improvement of resolution 

Improvement of signal 


Summary and outlook 

Hadron masses are coming from non-perturbative behaviour of QCD vacuum. 

There is experimental evidence for in-medium modifications of vector mesons 

Vector mesons are important probes 

High resolution analysis are coming 

η 

Kinematic fit for Dalitz is in progress. 



G.Agakishiev 7 , C.Agodi2, H.Alvarez-Pol19, A.Balanda5, R.Bassini10, G.Bellia2,3, D.Belver19, J.Bielcik6, A.Blanco4, M.Böhmer14, 

C.Boiano10, A.Bortolotti10, J.Boyard16, S.Brambilla10, P.Braun-Munzinger6, P.Cabanelas19, S.Chernenko7, T.Christ14, 

R.Coniglione2, M.Dahlinger6, J.Díaz20, R.Djeridi9, F.Dohrmann18, I.Durán19, T.Eberl14, W.Enghardt18, L.Fabbietti14, O.Fateev7, 

P.Finocchiaro2, P.Fonte4, J.Friese14, I.Fröhlich9, J.Garzón19, R.Gernhäuser14, M.Golubeva12, D.González-Díaz19, E.Grosse18, 

F.Guber12, T.Heinz6, T.Hennino16, S.Hlavac1, J.Hoffmann6, R.Holzmann6, A.Ierusalimov7, I.Iori10,11, Ivashkin12, M.Jaskula5, 

M.Jurkovic14, M.Kajetanowicz5, B.Kämpfer18, K.Kanaki18, T.Karavicheva12, D.Kirschner9, I.Koenig6, W.Koenig6, B.Kolb6, U.Kopf6, 

R.Kotte18, J.Kotulic-Bunta1, R.Krücken14, A.Kugler17, W.Kühn9, R.Kulessa5, S.Lang6, J.Lehnert9, L.Maier14, P.Maier-Komor14, 

C.Maiolino2, J.Marín19, J.Markert8, V.Metag9, N.Montes19, E.Moriniere16, J.Mousa15, M.Münch6, C.Müntz8, L.Naumann18, 

R.Novotny9, J.Novotny17, W.Ott6, J.Otwinowski5, Y.Pachmayer8, V.Pechenov7, T.Pérez9, J.Pietraszko6, J.Pinhao4, R.Pleskac17, 

V.Pospísil17, W.Przygoda5, A.Pullia10,11, N.Rabin13, B.Ramstein16, S.Riboldi10, J.Ritman9, P.Rosier16, M.Roy-Stephan16, 

A.Rustamov6, A.Sadovsky18, B.Sailer14, P.Salabura5, P.Sapienza2, A.Schmah6, W.Schön6, C.Schroeder6, E.Schwab6, P.Senger6, 

R.Simon6, V.Smolyankin13, L.Smykov7, S.Spataro2, B.Spruck9, H.Stroebele8, J.Stroth8,6, C.Sturm6, M.Sudol8,6, V.Tiflov12, 

P.Tlusty17, A.Toia9, M.Traxler6, H.Tsertos15, I.Turzo1, V.Wagner17, W.Walus5, C.Willmott19, S.Winkler14, M.Wisniowski5, 

T.Wojcik5, J.Wüstenfeld8, Y.Zanevsky7, P.Zumbruch6 

1)Institute of Physics, Slovak Academy of Sciences, 84228 Bratislava, Slovakia 

2)Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud, 95125 Catania, Italy 

3)Dipartimento di Fisica e Astronomia, Università di Catania, 95125, Catania, Italy 

4)LIP-Laboratório de Instrumentação e Física Experimental de Partículas, Departamento de Física da Universidade de Coimbra, 3004-516 Coimbra, 

PORTUGAL. 

5)Smoluchowski Institute of Physics, Jagiellonian University of Cracow, 30059 Cracow, Poland 

6)Gesellschaft für Schwerionenforschung mbH, 64291 Darmstadt, Germany 

7)Joint Institute of Nuclear Research, 141980 Dubna, Russia 

8)Institut für Kernphysik, Johann Wolfgang Goethe-Universität, 60486 Frankfurt, Germany 

9)II.Physikalisches Institut, Justus Liebig Universität Giessen, 35392 Giessen, Germany 

10)Istituto Nazionale di Fisica Nucleare, Sezione di Milano, 20133 Milano, Italy 

11)Dipartimento di Fisica, Università di Milano, 20133 Milano, Italy 

12)Institute for Nuclear Research, Russian Academy of Science, 117312 Moscow, Russia 

13)Institute of Theoretical and Experimental Physics, 117218 Moscow, Russia 

14)Physik Department E12, Technische Universität München, 85748 Garching, Germany 

15)Department of Physics, University of Cyprus, 1678 Nicosia, Cyprus 

16)Institut de Physique Nucléaire d'Orsay, CNRS/IN2P3, 91406 Orsay Cedex, France 

17)Nuclear Physics Institute, Academy of Sciences of Czech Republic, 25068 Rez, Czech Republic 

18)Institut für Kern- und Hadronenphysik, Forschungszentrum Rossendorf, PF 510119, 01314 Dresden, Germany 

19)Departamento de Física de Partículas. University of Santiago de Compostela. 15782 Santiago de Compostela, Spain 

20)Instituto de Física Corpuscular, Universidad de Valencia-CSIC,46971-Valencia, Spain

Anar Rustamov, GSI Darmstadt For the HADES collaboration

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