Hadron physics at GSI

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Hadron physics at GSI S. Kox

To cite this version:

Synthesis and Consequences of the Workshop :

Hadronic Physics at the future GSI Facility

1/ “Non expert” point of view on the antiproton GSI project

Some introductory points about hadronic physics,

the challenges and international context

2/ Discussion about the workshop (along a list of questions)

The antiproton beam, the physics program with

the PANDA detector. Extensions proposed.

2

_{International Workshop on the Future Accelerator …}

Darmstadt, October 14-17th 2003

Hadron Physics : Context

Why is this study so important ?

z Understand the strong/color forces and establish its theory (QCD) z Nature of confinement. Origin of the mass of quarks.

z NN and qq forces and the transition between the 2 regimes.

z Understand how nucleons and nuclei are formed from elementary blocks (with quarks and gluons/Nucleon and mesons as degrees of freedom) z Understand the structure (charge/magnetic moments, spin, …) of

fundamental objects like the nucleons

z Hadron physics at the interface between High Energy and Nuclear Physics z Elementary processes and reactions/decays of hadrons can provide

Hadron Physics : Context (II)

Why is there is still so much to do ?

z Particularities of the force between quarks

z Exchanged gluons carries color and are self-interacting.

z

α

z Many body problem and relativist effects to be treated exactly. z Limitation of previous experiments

z Beam (energy, intensity, duty cycle,

δ

ª Statistics, systematic errors, S/B ratio ª Ambiguities in results

z Absence of exact theory for a long time z Non predictive,

ª Poor guidance for the experiment (pentaquark and sleeping data …)

z Models with free parameters

Hadronic Physics : Challenges

Good progress underway and to come

z Theory and models with physics ingredients

(Madeleine Soyeur, Ted Barnes, Chris Michael talks)

z Rapid progress in LQCD with CPU. Discretization (smaller steps),

boundary conditions (larger volume), unquenched calculations (qq loops). z Models (QCD inspired, Chiral symmetry) are used for the light quark sector

ª Predictive level has been/can be further improved

z New generation of accelerators and associated detection set-ups

z Complete data sets (precision, large energy domain, …)

z Unambiguous signatures of states and process with good statistics

z Complementary probes/facilities

z Possible cross checks and different quantum numbers productions

z Links with companion fields

EM probe : JLab, MAMI, ELSA, GRAAL, SPRING8, …

Form Factors, N*, PV, GDH, Few Body,

Transition to pQCD, GPDs, Hypernuclei …

z Energy 1-6 GeV (→ 12 GeV project) z Electrons and photons

EM probe : HERMES, CERN, SLAC, …

Deep inelastic (SPIN), GPD, SM (PV) …

z Energy 20-200 GeV z Electrons and muons

Hadronic probe : CELSIUS, COSY, CERN, …

Spectroscopy, elem. cross sections, Hypernuclei, rare decays, ...

z Energy 1-3 GeV, 200 GeV

z Protons, secondary hadron beams

e+_e- _{colliders : DAΦPNE, BEPC, Cornell, ..}

Rare decays, Glueballs, spectroscopy… z CM energy (h-h creation)

Only a few machines still running

in 10 years Î need new projects

European machines in

operation for

Hadron Physic

µ

SPRING8, J-PARC Project (Japan) →

← JLab, 12 GeV Project (USA)

1.5 GeV

GSI Project

pup to 30 GeV

anti-pup to 14 GeV

The GSI project and Hadron Physics

How GSI is proceeding

z New GSI facility aimed at

z Attracting a large community (International coll., Physics cases) 9 z Multi-user operation mode. Parallel operation for different physics.

z Provide high quality beams. Here a new probe : antiprotons

(Norbert Angert, Fritz Nolden, Markus Steck, .. Talks)

z High energy range in HESR (up to 14.5 GeV, covering the charm sector) z Very good resolution (1 MeV to 100 keV, with electron cooling)

z CW in storage ring and operation stable over 1/2-1h time periods z Large intensity (5 1011 antiproton in ring)

↔

ª Requires a tricky acceleration scheme (production target and a set of

storage rings (acceleration or deceleration) and cooling techniques). z Large luminosity

z Internal target (pellet, jets, wire …, t.b.d.). Thickness 2.5 1015 cm-2 z up to 2. 1032 cm-2.s-1

PANDA experimental program (I)

Charmonium

z qq potential

z Regular but also hybrid states (exotic JPC)

z Narrow states, but not at full beam energy (resolution less problematic) z Tests of recent observation. Improved statistics.

ª Could be used for/during commissioning period

Search for hybrid mesons in charm sector

z Role of the gluon. Flux tube and confinement (scalar/ vector) z Lower density/mixing of states (also system of 2 heavier quarks) z Formation versus production could sign directly the JPC

z Large statistics should allow complete partial wave analysis

z Scan in energy over threshold regions to disentangle mixed contributions

Search for glueballs

z Test case for gluonic degree of freedom in theory z Gluons are naturally well produced in pp annihilation

Experimental program with PANDA (II)

Hypernucleus

(Alessandro Feliciello talk) z S=-1

z Tests of nuclear structure. Study of medium effects z New perspectives

z S=-2 (double hypernuclei)

z Potential Y-N (Pentaquark : N-K) and Y-Y interaction. H particle z Possible test of weak interaction (Non-PV part)

z

γ

z Strong experimental requirements and adaptations of PANDA z Initial wire and secondary nuclear active targets

z

γ

Medium effects

z Propagation of J/Ψ in medium (related to QGP)

Questions asked (II) :

z Resolution allowing unambiguous determination for states/reaction … z Decay products (neutral and charged (B magnet))

z Partial wave analysis (

φ

z Importance of internal target (density, Nucleon and nuclear)

ª Need to make technical choice (pellet/jet, beam cooling issue ??)

z Versatility (covering present Physics cases … and more)

z Possibility to add specific detectors (

γ

z Choice of level trigger (needed for 4

π

ª PANDA (still under simulation) is developed along those requirements z Handled/supported by a large (young/2 years old) collaboration

Questions asked (I) :

2) What are the crucial problem (s) in hadronic physics that will likely be not fully solved within the next 10 years ??

z Full description of hadrons with QCD (theory and experimental tests) z Confinement and flux tubes. Excitation of gluonic degree of freedom. z Chiral symmetry role/restoration in quark masses.

z QCD in light quark sector. Role of qq pairs in resonances z q-q correlations in nucleon and spin (L_q) issue

3) What type of experiments (or experimental programs) can be done at the future GSI with antiprotons to answer these questions ??

z Discovery of exotic/missing states, glueballs, multiquarks assemblies … z Detailed/precise spectroscopy of hadrons. Study of charmonium states z Strangeness in nuclei (S=-1,-2).

z Modification/propagation of meson properties with/in medium (see also CBM). z Inverse DVCS ( luminosity, factorization ??). Nucleon form factor.

⊕ Companion physics :

4) Would an existing/future facility do the job ?

z Competition (complementary aspects) from :

z Halls B/D and JLab 6-12 GeV (exotics mesons, pentaquarks (in s sector) ) z e+-e- colliders and upgrades BEPCII+BESIII (charmonium, glueballs, …) z B factory via decays processes (charmonium)

z SPS + COMPASS (charmed baryons, …) z J-PARC (Hypernucleus, spectroscopy, …)

GSI beams/experiments can have however several unique features …

z antiproton probe in the high energy range (charm sector) z Gluon production. All JPC can be produced.

z Production of hadrons by pairs. Antiquarks in entrance channel z E_pbar = 0.8 - 14.5 GeV

z Fine steps in energy for scan (production/formation, threshold) z Very good resolution (cooling) down to some 10-5 in δp/p

z Large intensities of antiprotons ( 5. 1011 in HESR storage ring) z State of the art PANDA detector and large density internal target

Progress/content/teachings of the Workshop (hadron)

New ideas/programs

z Late night show and intrepid proposals :

(Paul Kienle, Kurt Killian, Frank Ratmann talks)

z antiproton-Radioactive beam collider (rms radii of p/n distributions) z Polarized target and polarized antiprotons (pp scattering)

z Not shown (to come ??) : How to increase antiproton production rate

z Low energy antiproton program (800 MeV → 100 keV) (Gerarld Gabrielse , Ryogo Hayano talks)

z CPT violation with anti-hydrogen. Still a long way to go (traps, laser, …) z antiprotonic atoms (e, m), low energy antiproton cross sections, halo …

z More antiprotons needed + NESR + FLAIR + 1-2 decelerating storage rings.

z Not shown in the workshop (see C.D.R. + PANDA internal workshop)

zCP violation

z Form factors, inverse DVCS, …

z Anti-deuteron formation ((Astroparticle + SUSY, beams ??),

ª LoI should follow soon and will strengthen even more the physics case

ª Add a synthesis's of the SM/Fundamental symmetry physics

Progress/content/teachings of the Workshop (hadron)

Other ideas/programs in PANDA

z Not shown in the workshop

(see C.D.R. + new ideas from PANDA internal workshop)

zCP violation

z Form factors, inverse DVCS, …

z Anti-deuteron formation ((Astroparticle + SUSY, beams ??),

ª LoI should follow soon and will strengthen even more the physics case

ª Add a synthesis's of the SM/Fundamental symmetry physics

Other teachings of the Workshop

z More clear (Thanks to pedagogic talks and booklet) z Allow extensions to lower energies, collider …

z Large luminosity and good resolution

z An unique production source of antiproton (sharing ??)

z Strong cooling necessary (duration, choice target, luminosity ??)

The attendance

z > 400 registered, 1/2 from abroad Germany z Several proto-collaborations :

z ≈ 200-300 physicists, ≈ 42 institutions, ≈ 15 countries each

Conclusions

The GSI future complex (antiproton beam, PANDA detector, possible

extensions) will provide a first class international facility for hadron physics. Physics program already attractive and competitive/unique worldwide.

It should provide results in hadron but also in related topics. Certainly more to come with LoIs.

---Congratulation to all people contributing to the tremendous momentum gained to initiate antiproton beams and related physics program @ GSI

0% 50% 100% Radioactive Beams Nucleus-Nucleus Collisions Antiprotons Plasma-Physics 100 Tm Ring 200 Tm Ring

Collector & Storage Ring

High-Energy Storage Ring

Nucleus-Nucleus 100 sec Radioactive

Beams PlasmaPhysics

Antiprotons

Duty

Duty--Cycles of the Accelerator RingsCycles of the Accelerator Rings _{DutyDuty--Cycles of the Physics ProgramsCycles of the Physics Programs}

GSI Future Facility

Quark’s Structure of the nucleon

z Growing complexity at low energy z Etat fondamental des hadrons !! z Quarks of QCD

z proton (938 MeV) = u + u + d (≈15 MeV) + … ª Importance of the gluons of the pairs qq

) Search/study of the contribution of the “sea”

(Spin, masse, impulsion, courants …)

Modèles de quarks constituants

z Dressed Quarks (gluons, pairs qq) z Valence Quarks

(Charge, spin, quantum numbers ) z Mass ≈ Mass Hadron/N_quarks

z Models of bag

z Prediction resonances, excited states z Models diquarks (missing resonances)

) Verification : Spectroscopy baryonic/mesonic

D

U U

⏐_{p> =} ⏐_{uc uc dc>}

Elementary force (color)

z quarks et gluons in interaction

ª No analytical treatment of hadron (in non perturbative regime)

NN Interaction

z Nucleons and mesons

z Phenomenological treatment

 Exchanges of mesons (

π,ρ,ω

z Residual force

z Screening of color force z Potential

z Attractive, vanish at medium range z Short range part (repulsive)

↔ color force

) Transition between these different

degrees of freedom at large Q2

From nucleons to nuclei

z Exact description (3 → 4 corps) z Independents particles

z NN Interactions

z Different potentials

(Paris, Bonn, Argonne ...)

z MEC (meson exchange currents) z Relativistic effects (Kinematics,

F.O. nucleon)

) Properties of bound nucleons z NN Correlations, 3-body forces

) Search for a ¨ standard model ¨

of light nuclei (H, He)

Nuclei and hadronic physics

z NN Correlations

z Chiral symmetry restoration,

0.1 0.2 0.3 0.4 0.5 0.6 x_B 0 2 4 6 8 10 Q 2 (GeV 2 ) Upgraded CEBAF W > 2 GeV E = 27 GeV HERMES Hall A E = 11 GeV E = 6 GeV C O M P A S S C L A S

Generalized structure functions z Function of x,

∆

Î Correlations between partons z Hard exclusive reactions

 Factorization (pQCD regime,

to be tested) + handbag diagram...

z Integrals of GPDs

Î Spin of the nucleon (L_q) z Various kinematical variables

ª combination of several machines …

CEBAF 12 GeV (project)

Internal Structure of nucleon and mesons

z EM Form Factors at largest Q2

s and c thresholds

z Photo/Electro-production reactions Hard scattering reactions

z Structure Functions at large x and Q2 z Generalized Structure Functions

(⇒ GPD)

Exotic mesons

z Excitations of flux tube (gluons)

z Hybrid Mesons (new JPC ) z Predicted by Lattice QCD

ª Confinement ? z 5 ½ tours (11 GeV)

z New dedicated Hall (D)

z 4

π

z Photons : 8-9 GeV, linear polar.

CEBAF concept

and

performances

Recirculation Arcs (N=1-5 passes)

) 2 LINAC of 0.6 GeV max.

z 3 beams simultaneously

z Choice of E (N x E₀ (1 pass)) and Intensity for each Hall z Emittance ≈ 2 10-9 m.rd z Resolution in energy

δ

µ

Interaction de couleur

z Etats propres de SU(3) : Singulets de couleur

) quarks ou gluons ne peuvent être observés seuls/libre

Force quark-quark

z Echange des couleurs via des gluons (8) colorés (couleur + anticouleur)

ª Gluons interagissent entre eux

(diagrammes à 3-4 gluons)

z Echange d’un gluon : Force attractive

pour les états singulets de couleur

2 régimes distincts z A petite distance

ÂLiberté asymptotique (V_q-q (forte) → 0)

z A grande distance, V augmente (en kr)

Calcul de théorie des champs

z Lagrangien physique (QCD, …)

z Discrétisation de l’espace temps (x,y,z,t) z a3.n_t (106) sites où l’on calcule le champ z Variation (MC) des valeurs de champ

ª erreur statistique

z Intégrales sur toutes les configurations (104) ª Observables (masses …)

Hypothèse/simplifications

z Maille élémentaire finie (a ≠ 0)

z Volume fini (conditions aux limites)

ª Erreurs systématiques

z Métrique (Minkowski → Euclidien)

) Pas adaptée pour les états de diffusion

z Approximation “quenched”

(gluons mais pas de boucles (paires))

) prédictions pour mer qq ??

Prédictions

z Progrès avec techniques de calcul z Masses hadrons à 10%

z Masses quarks constituants, interaction q-q

z Constantes faibles, CKM

z … toutes théories des champs