Spectroscopy in the Charm Domain

Spectroscopy in the Charm Domain
– Introduction
– Merits of Experiments with Antiprotons
– Charmonium Spectroscopy
– Charmed Hybrids
– Heavier Glueballs
– Open Charm States
– Further Options
– PANDA-Detector
– Conclusions
H. Koch, Hadron Physics at COSY, July 2003
Introduction
Open problems in non-perturbative QCD
Confinement
Violation of chiral symmetry
Masses of Hadrons
Important : Gluonic degrees of freedom
H. Koch, Hadron Physics at COSY, July 2003
QCD systems to be studied at HESR
H. Koch, Hadron Physics at COSY, July 2003
HESR / PANDA
Production Rates (1-2 (fb)-1/y)
Final State
cross section
# reconstr. events/y
Meson resonance + anything
100µb
1010
50µb
1010
ΛΛ
Ξ Ξ (→ ΛΛ A)
2µb
10 8 (10 5 )
DD
250nb
10 7
J /ψ (→ e + e – , µ+µ – )
630nb
10 9
χ 2 (→ J /ψ + γ)
3.7nb
10 7
Λ c Λc
20nb
10 7
Ωc Ωc
0.1nb
10 5
Common Feature : Low multiplicity events
Moderate particle energies
For Pairs : Charge symmetric conditions
Trigger on one, investigate the other
H. Koch, Hadron Physics at COSY, July 2003
Merits of experiments with Antiprotons
– High cross sections
Facilitates search for rare particles (Glueball Groundstate)
– Most particles can be directly created in formation processes regardless of
PC
their J quantum numbers (cc-spectroscopy)
– Exotic states are produced with rates similar to qq, qqq-systems (Glueball-,
Hybrid candidates)
– (Cooled) beams have small ∆p/p and small emittances
Clean experimental conditions
– p-induced reactions (≤ 15 GeV) have low particle multiplities
Reconstruction of full events, Reliable PWA
H. Koch, Hadron Physics at COSY, July 2003
Merits of experiments with Antiprotons
Charmonium - States
e+e–- collisions:
Only 1– – -states are directly formed
(Well measured, e– e+ energy scans)
The other states only visible through
secondary reactions,
e.g.: e+e– → ψ’ → χ + γ (moderate mass resolution)
pp - collisions:
All states can be directly formed (Very good mass
resolution, scans with p)
H. Koch, Hadron Physics at COSY, July 2003
Physics with Antiprotons
LEAR: Candidate for Glueball Groundstate
H. Koch, Hadron Physics at COSY, July 2003
Merits of experiments with Antiprotons
LEAR : Spin Exotics
Number of events
pStop d → X(1−+ ) + π + p, X(1400 ) → ηπ 0 , ηπ − ; X(1600 ) → πη′ (Established by BNL;
First hints: VES,
General observations
GAMS)
– High Statistics data needed
– Exotics couple to pp with
a strength similar to qq-states
a2(1320)
π1(1400)
1
2
3
m2πη [GeV2/c4]
H. Koch, Hadron Physics at COSY, July 2003
Physics Program / Charmonium Spectroscopy
cc - system (QCD) ^= e+e–-system (QED)
Energies/Energy splittings/Widths of states
Details of QQ-interactions
Confinement Potential
Exclusive Decays
Mixing of perturbative/non-pert. effects
H. Koch, Hadron Physics at COSY, July 2003
Physics Program / Charmonium Spectroscopy
Experimental situation
R704 (CERN/ISR) / E760/835 (Fermilab)
Very precise values for masses and withs of χc, ηc-states
Measurement of previously unknown branching ratios
Determination of αs (mc)
But : Severe limitations (Non magnetic detector, beamtime, beam momentum
reproducibility, ...)
Many questions left open:
– 1P1 (E760) unconfirmed
– D-wave states (some of them very narrow) and radially P-states not fully understood
(Structure of states)
– Angular distributions of radiative decays not understood
(Mixing of pert./non-pert. Effects)
e.g. J / ψ → ρπ 0 ; ηc , χ co → BB (Hadron helicity non conserving process)
J / ψ → π + π − , ωπ 0 , ρη (G − parity violating decays)
ψ′ → γ + π, η ... (Radiative ψ′ − decays)
χ cJ → ρρ, φφ, ρη, ρη′, η′η′ (Higher Fock state contributions)
H. Koch, Hadron Physics at COSY, July 2003
Physics Program / Charmed Hybrids
Charmed Hybrids : (ccg)
Predictions: (LQCD, Bag-Model, Flux-Tube-Model,…)
Masses
Lowest energy states: 3.9-4.5 GeV/c2
Ground state: JPC = 1–+ (spin-exotic)
Widths
Could be narrow in some cases (≈MeV)
H. Koch, Hadron Physics at COSY, July 2003
Physics Program / Heavier Glueballs
Glueballs (gg)
Predictions:
Masses:
1.5-5.0 GeV/c2 (Ground state found? ;
Candidates for further states?)
Quantum numbers:
Several spin exotics (oddballs), e.g.
JPC = 2+- (4.3 GeV/c2 )
Widths: ≥ 100 MeV/c2
– Decay into two lighter glueballs often
forbidden because of q.-n.
– No mixing effects for oddballs
H. Koch, Hadron Physics at COSY, July 2003
Charmonium States and Predicted Glueballs
H. Koch, Hadron Physics at COSY, July 2003
Physics Program / Heavier Glueballs
Production cross section:
Maybe high in pp-annihilation (see f0(1500))
Comparable to qq-systems (! µb)
Experimental program at HESR
p-scan for non-exotics: pp → (gg) → φφ, φη
(Most reasonable channels, easily distinguishable,
low l - waves (simple PWA))
Production exp. for exotics: pp → (gg) + π
Reasonable measuring times
H. Koch, Hadron Physics at COSY, July 2003
Physics Program / Measurements in the Charm Region
Spin non − exotic states X : pp → X ( p − scan )
X : Heavier qq − mesons → nπ + mK ,...
Heavier Glueballs
→ φφ, φη,...
Charmed Hybrids
→ J / ψη,...
Spin − exotic states (# qq )Y : pp → Y + π, η,... (Production mod e )
→ ηπ, φφ,...
Y : Oddballs
Charmed Hybrids → χ(ππ )s ,... (e.g. groundstate )
H. Koch, Hadron Physics at COSY, July 2003
Physics with Open Charm
Many open questions yet
2
e.g. BR ( D+ → µ+ γ) → ψ D (0) , Sensitive Test of LQCD
Decay Branching Ratios of D‘s: Mixture of perturbative/non perturbative effects
M
Very recent development (BaBar, Belle, Cleo)
One extremely narrow state found: D*sj (2317), Γ compatible with exper. resolution
0
Dsπ
Explanations:
Excited cs-state improbable. Mass from quark-model does
not fit (Chiral extension)
DK-molecular state (see f0(980), a0(980)-Problem)?
Baryonium-state?
M
Latest news: Further state found: D*sj (2460)
Rich physics program in reach
H. Koch, Hadron Physics at COSY, July 2003
Physics Program / Further Options
– Baryon Spectroscopy
New states, Quantum numbers and decay rates
– Direct CP-Violation in Λ, Λ-decays
Compare angular decay asymmetries (α, α ) for Λ → pπ − / Λ → pπ +
α+ α
α− α
Prediction (SM) ≈ 2x10-5
A≈
HESR: 1 year of beamtime
H. Koch, Hadron Physics at COSY, July 2003
Physics Program / Further Options
CP-Violation in charmed region
D 0 / D 0 − Mixing (r ) < 10 −8 (SM )
HESR : ∆r / r ~ 10 −4
Direct CP-Violation (SCS)
Compare D + → K + K 0* / D − → K − K 0*
Asymmetries A (SM ) < 10 −3
HESR = ∆A / A ≈ 10 −4 − 10 −3
H. Koch, Hadron Physics at COSY, July 2003
Physics Program / Further Options
Study of reversed Deeply Virtual Compton Scattering (DVCS)
p + p → γ * + γ → l + l − + γ → Nucleon structure functions
Low energy p-physics
– pp-annihilation process
– Antiprotonic atoms
– Antihydrogen
H. Koch, Hadron Physics at COSY, July 2003
PANDA – Detector
Detector requests
– Nearly full solid angle for charged particles and Gammas
– High rate capability
– Good particle identification (e, µ, π, K, p)
– Efficient trigger on e, µ, K, D
General purpose detector
– Target:
Jet/Pellet/Wire
– Tracking:
Pixels (MVD) / Straws / Mini-Drift-Chambers (MDC)
– E.M. Calorimeter: PbWO4, APD-Readout
– Muons:
Plastic Scint. Strips
– PID:
Aerogel Cerenkov (ACC) / DIRC
– Trigger:
High p⊥ electrons/muons / Multiplicity jump (K0S, Λ, …)
Secondary vertex (D’s,…) / Invariant masses / Global kinematical conditions
H. Koch, Hadron Physics at COSY, July 2003
Conclusion
– HESR will deliver cooled high quality antiproton beams with energies up to 15 GeV
– Antiproton induced reactions exhibit unique features
– High statistics data
– Low multiplicity events
– Symmetric production of particles and antiparticles
– High production rates for gluonic hadrons
– Many states can be directly formed
– Rich and unique Physics Program with emphasis on charmed particles
– Precision charmonium spectroscopy
– Search for charmed hybrids and heavier Glueballs
– Investigation of Open Charm Systems (Molecules)
– CP-violation in the charm sector
– Low energy p - physics, including Antihydrogen experiments
H. Koch, Hadron Physics at COSY, July 2003