hadron physics with antiprotons with the panda experiment
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Hadron Physics with Antiprotons with the PANDA Experiment at FAIR
Diego Bettoni INFN, Ferrara, Italy
Outline
• Introduction • Physics program • PANDA at the MSV: the first 2 years • Detector • Summary
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One of the open problems in the Standard Model is a full understanding of Quantum Chromodynamics (QCD). QCD well and tested at high energies (perturbative regime). At low energies QCD becomes a strongly coupled theory, many aspects of which are not understood.
Physics Scope
PANDA at FAIR
Asympto7c freedom
Confinement
D.Be.oni 3
Experimental Measurements
• Hadron Spectroscopy. Precision measurements of particle spectra to be compared with theory calculations. Identification of the relevant degrees of freedom. – light quarks, cc, bb – heavy-light systems (D and B mesons) – baryons – Search for new forms of hadronic matter: hybrids,
glueballs, multiquark states ... (X, Y, Z) • Hadron structure.
– Form Factors – GDA, GPD, TMD – Spin physics
• Hadronic interactions: – Hadrons in nuclear matter (Origin of mass) – Hyperon physics (e.g. spin observables) – Hypernuclei.
PANDA at FAIR D.Be.oni 4
GSI Helmholtz Center and FAIR
PANDA at FAIR
p-‐Linac
HESR
SIS18 SIS100
CR/RESR
An7protons Produc7on Target
D.Be.oni 5
PANDA at FAIR
High luminosity mode High resolution mode
Nstored = 1010 p dp/p ~ 3×10-5 (electron cooling) Lumin. = 1031 cm-2 s-1
Nstored = 1011 p Lumin. = 2 x 1032 cm-2 s-1 dp/p ~ 10-4 (stochastic cooling)
Production rate 2x107/sec
Pbeam = 1.5 - 15 GeV/c Internal Target 4×1015 cm-2
High-Energy Storage Ring
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PANDA at FAIR
High luminosity mode High resolution mode
Nstored = 1010 p dp/p ~ 3×10-5 (electron cooling) Lumin. = 1031 cm-2 s-1
Nstored = 1011 p Lumin. = 2 x 1032 cm-2 s-1 dp/p ~ 10-4 (stochastic cooling)
Production rate 2x107/sec
Pbeam = 1.5 - 15 GeV/c Internal Target 4×1015 cm-2
High-Energy Storage Ring
Modularized Start Version (MSV0-3)
L ~ 1031cm-2s-1 Δp/p ~ 5 × 10-5
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PANDA at FAIR
pp Annihilation
Direct resonant formation of states with all non-exotic quantum numbers. ⟹ excellent precision in mass and
width measurement
Gluon- Rich Environment
Access to both exotic and non-exotic quantum numbers via production and formation reactions
Uniqueness of p probe (no other p facility in this energy range in the world)
Versatility of physics program (if coupled to universal detector)
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Comparison with Other Techniques
• e+e-
– direct formation limited to JPC = 1—
– limited resolution for masses and widths for non vector states – sub-MeV widths very difficult or impossible – high L not accessible
• high-energy (several TeV) hadroproduction – high combinatorial background makes discovery of new states
very difficult – width measurements limited by detector resolution
• B decays (both for e+e- and hadroproduction) – limited JPC
– C cannot be determined since not conserved in weak decay
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PANDA at FAIR
Experimental Method
( ) 4/412
22
2
2RR
RoutinBW ME
BBk
JΓ+−
Γ+=
πσ
The cross section for the process: pp → R → final state is given by the Breit-Wigner formula:
The production rate ν is a convolution of the BW cross section and the beam energy distribution function f(E,ΔE):
{ }∫ +Δ= bBW EEEdEfL σσεν )(),(0
The resonance mass MR, total width ΓR and product of branching ratios into the initial and final state BinBout can be extracted by measuring the formation rate for that resonance as a function of the cm energy E.
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PANDA at FAIR
Example: χc1 and χc2 scans in Fermilab E835
χ1
χ2
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PANDA at FAIR
PANDA Physics Program • HADRON SPECTROSCOPY
– CHARMONIUM – GLUONIC EXCITATIONS – OPEN CHARM – (MULTI)STRANGE BARYONS
• NUCLEON STRUCTURE – ELECTROMAGNETIC FORM
FACTORS – TMDs – GPDs, TDAs
• HYPERNUCLEAR PHYSICS • HADRONS IN THE NUCLEAR
MEDIUM
ArXiV:0903.3905 D.Be.oni 12
Exotic Hadrons I: Hybrids and Glueballs
p
p _
G
M
p
M
H
p _
p
M
H
p _
p
p _ G
p
p _ H
p
p _ H
Production
all JPC available
Formation
only selected JPC
nng ssg/ccg
PANDA at FAIR
Sound theoretical predictions from models and LQCD Gluon rich process creates gluonic excitation in a direct way Access to both exotic and non-exotic quantum numbers Highest precision for direct formation Access to both light and charm energy range UNIQUE to PANDA
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Glueball Search at PANDA
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Exotic Hadrons II: X, Y, Z
PANDA at FAIR
BàK π+π-J/ψ
X(3872) Y(4260)
BaBar
Belle ψ’
X(3872)
Zc(3900) at BESIII
Need systematic approach with the capability to carry out high-precision measurements to map out completely the spectrum of these news states, in order to understand their nature: PANDA will be unique in achieving this.
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Exotic Hadrons II: X, Y, Z
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Exotic Hadrons II: X, Y, Z
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X, Y, Z Rates at PANDA
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X, Y, Z at PANDA
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X(3872) at PANDA
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Open Charm
• QCD laboratory • Intermediate case between heavy and light quarks • Interesting spectroscopy • Weak interactions At PANDA full program requires high luminosity (1032cm-2s-1). Unique features at PANDA: • width measurement of DsJ(2317)
(30-100 KeV) (threshold scan) • Access to high L (available in pp,
suppressed in B decays)
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Strange and Charmed Hyperons
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Strange and Charmed Baryons
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Baryon Spectroscopy
PANDA at FAIR
• New baryon states ? • Properties of already known states. • Symmetries in observed spectrum.
Baryons in PANDA • Large cross section s for pp → YY
• pp → ΞΞ ≈ µb • pp → ΩΩ ≈ 0.002 ÷ 0.06 µb
• No extra mesons in final state needed for strangeness or charm conservation • Symmetry in hyperon and
antihyperon • PANDA detector versatile
Prospects for PANDA
S=2 hyperons (Ξ) S=0 baryons (N) S=1 hyperons (Λ)
S=3 hyperons (Ω)
Charmed (Λc, Σc) Hidden charm (Ncc)
PANDA is a Strangeness Factory
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Spin Observables in Hyperon Production
PANDA at FAIR
The parity-violating weak decay of hyperons gives access to spin observables even for unpolarised beam/target. These observables give insight in the production mechanism of hyperons (e.g. the role of spin in strangeness and charm production). Unique to PANDA: the study of these observables and especially the hyperon-antihyperon spin correlations.
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Ξ- capture: Ξ- p → ΛΛ + 28 MeV
Ξ-
3 GeV/c
Kaons _Ξ
Λ Λ
trigger
p_
2. Slowing down and capture
of Ξ- in secondary
target nucleus
1. Hyperon-
antihyperon production
at threshold +28MeV
γ
3. γ-spectroscopy
with Ge-detectors
γ
Production of Double Hypernuclei
Ξ-(dss) p(uud) → Λ(uds) Λ(uds)
PANDA at FAIR
1300 Hz
8000 / month
80 / month
5600 / day 12C diamond target to produce Ξ− Trigger on Ξbar. Ξ− interacts with ac7ve target containing different nuclei. Detect decay products. • High produc7on rate; • Many hypernuclear systems at the same
7me; • High acceptance/resolu7on magn. spect.
for neutral and charged; • Ge-‐detectors for X-‐ray transi7ons;
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Charmonium in Nuclei
PANDA at FAIR
e+
e-
Measure J/ψ production cross section in p annihilation on nuclear targets. ⇒J/ψ-nucleus dissociation cross section
• In PANDA the J/ψ is produced at relatively low energies. The cc pair hadronized in a very short time. • Measurement problematic in pA (need to go to xF ≪ 0) • ALICE at high energies opposite situation wrt PANDA.
PANDA produces charmonium in cold nuclear matter, providing exclusive information complementary to hadroproduction and heavy ion experiments.
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Proton Electromagnetic Form Factors in the Timelike Region
PANDA at FAIR
]2s [(GeV/c)4 6 8 10 12 14
R
0
0.5
1
1.5
2
2.5
3BaBar
LEAR
E835
FENICE+DM2
PANDA sim. I
PANDA sim. II
pp→ e+e− pp→ µ+−µ−
Measurement of effective form factor over wide q2 range (30 GeV2) Individual measurement of |𝐺𝐸| and |𝐺𝑀| and their ratio R First measurement of form factors with muons. Measurement of form factors in unphysical region Longer range goal: measurement of phase of |𝐺𝐸| and |𝐺𝑀| via polarisation observables.
pp→ e+e−π 0
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Drell-Yan Process at PANDA
PANDA at FAIR
Handbag diagram: s>>Mh2
PDFs are convoluted with the fragmenta7on func7ons
@ FAIR unique energy range up to s~30 GeV2 with PANDA @ much higher energies → big contribution from sea-quarks @ppbar annihilation each valence quark contribute to the diagram
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Transition Distribution Amplitudes
PANDA at FAIR
• Describe the transition between two particles • Explore pionic components in the nucleon wave function • Transverse picture of the pion cloud • Universality: the same TDA could be measured in different kinematics/reactions • Test of Factorisation
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PANDA at FAIR
Hard Exclusive Processes and pp→γγ Generalized Distribution Amplitudes (GDA)
The QCD factorization theorem allows us to calculate high energy cross sections separating short-distance process with long-distance non perturbative functions Hard scale is defined by the large transverse momentum of the final state photon
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Timelike wide-angle Compton scattering can be measured at PANDA S/B~1 for (25% efficiency) S/B~2 for (50% efficiency) Further studies are required for precise predictions
pp→ π 0γpp→ γγ
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PANDA Spectrometer
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Minimal Detector for Start Physics
• Target TDR approved ✔ • Charged track detection and momentum
– Magnets TDR approved ✔ – MVD TDR approved ✔ – STT Tracker TDR approved ✔ – Forward tracker (2/6) TDR 2016 – Muon chambers TDR approved ✔
• Photons and electrons – Electromagnetic calorimeter TDR approved ✔ – Shashlyk TDR submitted
• Particle ID – Barrel DIRC TDR 2016 – Forward TOF TDR 2016
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Cluster Solenoid Muon GEM Dipole Muon Range Luminosity Target Detectors Plane System Detector
Barrel DIRC MVD STT Barrel FE Part FToF FSC EMC EMC F-Trk
BE EMC
PANDA Start Setup
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Cluster Solenoid Muon GEM Dipole Muon Range Luminosity & Pellet Detectors Tracker System Detector
Target
Barrel DIRC MVD STT Barrel Disc FE Full FRICH FToF FSC Barrel ToF EMC DIRC EMC F-Trk
BE EMC
PANDA Final Setup
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Summary
• PANDA has developed a world class experimental program covering the three pillars of hadron physics: – hadron spectroscopy – hadron structure – hadron interaction These experimental programs present many synergies and can in most cases be carried out in parallel.
• PANDA is unique in combining the potential for the discovery of new physics with the ability to carry out precise, systematic measurements.
• This physics potential will remain intact, and even increase, with time.
• The collaboration, detector developments and funding are in good shape and we are on track to produce excellent physics at the beginning of the next decade.
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